[Search] [txt|pdf|bibtex] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 04 05 06 07 rfc3010                                  
NFS Version 4 Working Group                                  S. Shepler
INTERNET-DRAFT                                             B. Callaghan
Document: draft-ietf-nfsv4-01.txt                             M. Eisler
                                                            D. Robinson
                                                             R. Thurlow
                                                       Sun Microsystems
                                                              D. Noveck
                                                      Network Appliance
                                                         September 1999

                             NFS version 4

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet- Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

Abstract

   NFS version 4 is a distributed file system protocol which owes
   heritage to NFS versions 2 [RFC1094] and 3 [RFC1813].  Unlike earlier
   versions, NFS version 4 supports traditional file access while
   integrating support for file locking and the mount protocol.  In
   addition, support for strong security (and its negotiation), compound
   operations, and internationlization have been added.  Of course,
   attention has been applied to making NFS version 4 operate well in an
   Internet environment.

Expires: March 2000                                             [Page 1]


Draft Protocol Specification  NFS version 4               September 1999

Copyright

   Copyright (C) The Internet Society (1999).  All Rights Reserved.

Key Words

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119.

Expires: March 2000                                             [Page 2]


Draft Protocol Specification  NFS version 4               September 1999

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . 7
   2.  RPC and Security Flavor  . . . . . . . . . . . . . . . . . . 8
   2.1.  Ports and Transports . . . . . . . . . . . . . . . . . . . 8
   2.2.  Security Flavors . . . . . . . . . . . . . . . . . . . . . 8
   2.2.1.  Security mechanisms for NFS version 4  . . . . . . . . . 8
   2.2.1.1.  Kerberos V5 as security triple . . . . . . . . . . . . 8
   2.2.1.2.  <another security triple>  . . . . . . . . . . . . . . 9
   2.3.  Security Negotiation . . . . . . . . . . . . . . . . . . . 9
   2.3.1.  Security Error . . . . . . . . . . . . . . . . . . . .  10
   2.3.2.  SECINFO  . . . . . . . . . . . . . . . . . . . . . . .  10
   3.  File handles . . . . . . . . . . . . . . . . . . . . . . .  11
   3.1.  Obtaining the First File Handle  . . . . . . . . . . . .  11
   3.1.1.  Root File Handle . . . . . . . . . . . . . . . . . . .  11
   3.1.2.  Public File Handle . . . . . . . . . . . . . . . . . .  12
   3.2.  File Handle Types  . . . . . . . . . . . . . . . . . . .  12
   3.2.1.  General Properties of a File Handle  . . . . . . . . .  12
   3.2.2.  Persistent File Handle . . . . . . . . . . . . . . . .  13
   3.2.3.  Volatile File Handle . . . . . . . . . . . . . . . . .  13
   3.2.4.  One Method of Constructing a Volatile File Handle  . .  15
   3.3.  Client Recovery from File Handle Expiration  . . . . . .  15
   4.  Basic Data Types . . . . . . . . . . . . . . . . . . . . .  17
   5.  File Attributes  . . . . . . . . . . . . . . . . . . . . .  19
   5.1.  Mandatory Attributes . . . . . . . . . . . . . . . . . .  20
   5.2.  Recommended Attributes . . . . . . . . . . . . . . . . .  20
   5.3.  Named Attributes . . . . . . . . . . . . . . . . . . . .  20
   5.4.  Mandatory Attributes - Definitions . . . . . . . . . . .  22
   5.5.  Recommended Attributes - Definitions . . . . . . . . . .  25
   5.6.  Interpreting owner and owner_group . . . . . . . . . . .  30
   6.  Filesystem Migration and Replication . . . . . . . . . . .  31
   6.1.  Replication  . . . . . . . . . . . . . . . . . . . . . .  31
   6.2.  Migration  . . . . . . . . . . . . . . . . . . . . . . .  31
   6.3.  Interpretation of the fs_locations Attribute . . . . . .  32
   6.4.  Filehandle Recovery for Migration or Replication . . . .  33
   7.  NFS Server Namespace . . . . . . . . . . . . . . . . . . .  34
   7.1.  Server Exports . . . . . . . . . . . . . . . . . . . . .  34
   7.2.  Browsing Exports . . . . . . . . . . . . . . . . . . . .  34
   7.3.  Server Pseudo File-System  . . . . . . . . . . . . . . .  35
   7.4.  Multiple Roots . . . . . . . . . . . . . . . . . . . . .  35
   7.5.  Filehandle Volatility  . . . . . . . . . . . . . . . . .  35
   7.6.  Exported Root  . . . . . . . . . . . . . . . . . . . . .  36
   7.7.  Mount Point Crossing . . . . . . . . . . . . . . . . . .  36
   7.8.  Security Policy and Namespace Presentation . . . . . . .  37
   7.9.  Summary  . . . . . . . . . . . . . . . . . . . . . . . .  37
   8.  File Locking . . . . . . . . . . . . . . . . . . . . . . .  38
   8.1.  Definitions  . . . . . . . . . . . . . . . . . . . . . .  38
   8.2.  Locking  . . . . . . . . . . . . . . . . . . . . . . . .  39

Expires: March 2000                                             [Page 3]


Draft Protocol Specification  NFS version 4               September 1999

   8.2.1.  Client ID  . . . . . . . . . . . . . . . . . . . . . .  39
   8.2.2.  nfs_lockowner and stateid Definition . . . . . . . . .  41
   8.2.3.  Use of the stateid . . . . . . . . . . . . . . . . . .  41
   8.2.4.  Sequencing of Lock Requests  . . . . . . . . . . . . .  42
   8.3.  Blocking Locks . . . . . . . . . . . . . . . . . . . . .  42
   8.4.  Lease Renewal  . . . . . . . . . . . . . . . . . . . . .  43
   8.5.  Crash Recovery . . . . . . . . . . . . . . . . . . . . .  43
   8.5.1.  Client Failure and Recovery  . . . . . . . . . . . . .  43
   8.5.2.  Server Failure and Recovery  . . . . . . . . . . . . .  44
   8.5.3.  Network Partitions and Recovery  . . . . . . . . . . .  44
   8.6.  Server Revocation of Locks . . . . . . . . . . . . . . .  45
   8.7.  Share Reservations . . . . . . . . . . . . . . . . . . .  46
   8.8.  OPEN/CLOSE Procedures  . . . . . . . . . . . . . . . . .  47
   9.  Client-Side Caching  . . . . . . . . . . . . . . . . . . .  48
   9.1.  Performance Challenges for Client-Side Caching . . . . .  48
   9.2.  Proxy Caching  . . . . . . . . . . . . . . . . . . . . .  49
   9.3.  Delegation and Callbacks . . . . . . . . . . . . . . . .  50
   9.3.1.  Delegation Recovery  . . . . . . . . . . . . . . . . .  51
   9.4.  Data Caching . . . . . . . . . . . . . . . . . . . . . .  53
   9.4.1.  Data Caching and OPENs . . . . . . . . . . . . . . . .  53
   9.4.2.  Data Caching and File Locking  . . . . . . . . . . . .  54
   9.4.3.  Data Caching and Mandatory File Locking  . . . . . . .  55
   9.4.4.  Data Caching and File Identity . . . . . . . . . . . .  56
   9.5.  Open Delegation  . . . . . . . . . . . . . . . . . . . .  57
   9.5.1.  Open Delegation and Data Caching . . . . . . . . . . .  59
   9.5.2.  Open Delegation and File Locks . . . . . . . . . . . .  60
   9.5.3.  Recall of Open Delegation  . . . . . . . . . . . . . .  60
   9.5.4.  Delegation Revocation  . . . . . . . . . . . . . . . .  63
   9.6.  Data Caching and Revocation  . . . . . . . . . . . . . .  63
   9.6.1.  Revocation Recovery for Write Open Delegation  . . . .  63
   9.7.  Attribute Caching  . . . . . . . . . . . . . . . . . . .  64
   9.8.  Name Caching . . . . . . . . . . . . . . . . . . . . . .  65
   9.9.  Directory Caching  . . . . . . . . . . . . . . . . . . .  66
   10.  Defined Error Numbers . . . . . . . . . . . . . . . . . .  68
   11.  NFS Version 4 Requests  . . . . . . . . . . . . . . . . .  73
   11.1.  Compound Procedure  . . . . . . . . . . . . . . . . . .  73
   11.2.  Evaluation of a Compound Request  . . . . . . . . . . .  73
   12.  NFS Version 4 Procedures  . . . . . . . . . . . . . . . .  75
   12.1.  Procedure 0: NULL - No Operation  . . . . . . . . . . .  75
   12.2.  Procedure 1: COMPOUND - Compound Operations . . . . . .  76
   12.2.1.  Operation 2: ACCESS - Check Access Rights . . . . . .  78
   12.2.2.  Operation 3: CLOSE - Close File . . . . . . . . . . .  82
   12.2.3.  Operation 4: COMMIT - Commit Cached Data  . . . . . .  84
   12.2.4.  Operation 5: CREATE - Create a Non-Regular File Object 87
   12.2.5.  Operation 6: DELEGPURGE - Purge Delegations Awaiting
            Recovery  . . . . . . . . . . . . . . . . . . . . . .  91
   12.2.6.  Operation 7: DELEGRETURN - Return Delegation  . . . .  92
   12.2.7.  Operation 8: GETATTR - Get Attributes . . . . . . . .  93

Expires: March 2000                                             [Page 4]


Draft Protocol Specification  NFS version 4               September 1999

   12.2.8.  Operation 9: GETFH - Get Current Filehandle . . . . .  95
   12.2.9.  Operation 10: LINK - Create Link to a File  . . . . .  97
   12.2.10.  Operation 11: LOCK - Create Lock . . . . . . . . . .  99
   12.2.11.  Operation 12: LOCKT - Test For Lock  . . . . . . . .  101
   12.2.12.  Operation 13: LOCKU - Unlock File  . . . . . . . . .  103
   12.2.13.  Operation 14: LOOKUP - Lookup Filename . . . . . . .  105
   12.2.14.  Operation 15: LOOKUPP - Lookup Parent Directory  . .  108
   12.2.15.  Operation 16: NVERIFY - Verify Difference in
             Attributes . . . . . . . . . . . . . . . . . . . . .  110
   12.2.16.  Operation 17: OPEN - Open a Regular File . . . . . .  112
   12.2.17.  Operation 18: OPENATTR - Open Named Attribute
             Directory  . . . . . . . . . . . . . . . . . . . . .  120
   12.2.18.  Operation 19: PUTFH - Set Current Filehandle . . . .  122
   12.2.19.  Operation 20: PUTPUBFH - Set Public Filehandle . . .  124
   12.2.20.  Operation 21: PUTROOTFH - Set Root Filehandle  . . .  125
   12.2.21.  Operation 22: READ - Read from File  . . . . . . . .  126
   12.2.22.  Operation 23: READDIR - Read Directory . . . . . . .  129
   12.2.23.  Operation 24: READLINK - Read Symbolic Link  . . . .  133
   12.2.24.  Operation 25: REMOVE - Remove Filesystem Object  . .  135
   12.2.25.  Operation 26: RENAME - Rename Directory Entry  . . .  137
   12.2.26.  Operation 27: RENEW - Renew a Lease  . . . . . . . .  140
   12.2.27.  Operation 28: RESTOREFH - Restore Saved Filehandle .  141
   12.2.28.  Operation 29: SAVEFH - Save Current Filehandle . . .  143
   12.2.29.  Operation 30: SECINFO - Obtain Available Security  .  145
   12.2.30.  Operation 31: SETATTR - Set Attributes . . . . . . .  147
   12.2.31.  Operation 32: SETCLIENTID - Negotiated Clientid  . .  150
   12.2.32.  Operation 33: VERIFY - Verify Same Attributes  . . .  152
   12.2.33.  Operation 34: WRITE - Write to File  . . . . . . . .  154
   13.  NFS Version 4 Callback Procedures . . . . . . . . . . . .  159
   13.1.  Procedure 0: CB_NULL - No Operation . . . . . . . . . .  159
   13.2.  Procedure 1: CB_COMPOUND - Compound Operations  . . . .  160
   13.2.1.  Procedure 2: CB_GETATTR - Get Attributes  . . . . . .  162
   13.2.2.  Procedure 3: CB_RECALL - Recall an Open Delegation  .  164
   14.  Locking notes . . . . . . . . . . . . . . . . . . . . . .  166
   14.1.  Short and long leases . . . . . . . . . . . . . . . . .  166
   14.2.  Clocks and leases . . . . . . . . . . . . . . . . . . .  166
   14.3.  Locks and lease times . . . . . . . . . . . . . . . . .  166
   14.4.  Locking of directories and other meta-files . . . . . .  167
   14.5.  Proxy servers and leases  . . . . . . . . . . . . . . .  167
   14.6.  Locking and the new latency . . . . . . . . . . . . . .  167
   15.  Internationalization  . . . . . . . . . . . . . . . . . .  168
   15.1.  Universal Versus Local Character Sets . . . . . . . . .  168
   15.2.  Overview of Universal Character Set Standards . . . . .  169
   15.3.  Difficulties with UCS-4, UCS-2, Unicode . . . . . . . .  170
   15.4.  UTF-8 and its solutions . . . . . . . . . . . . . . . .  171
   16.  Security Considerations . . . . . . . . . . . . . . . . .  172
   17.  NFS Version 4 RPC definition file . . . . . . . . . . . .  173
   18.  Bibliography  . . . . . . . . . . . . . . . . . . . . . .  200

Expires: March 2000                                             [Page 5]


Draft Protocol Specification  NFS version 4               September 1999

   19.  Authors and Contributors  . . . . . . . . . . . . . . . .  204
   19.1.  Contributors  . . . . . . . . . . . . . . . . . . . . .  204
   19.2.  Editor's Address  . . . . . . . . . . . . . . . . . . .  204
   19.3.  Authors' Addresses  . . . . . . . . . . . . . . . . . .  204
   20.  Full Copyright Statement  . . . . . . . . . . . . . . . .  206

Expires: March 2000                                             [Page 6]


Draft Protocol Specification  NFS version 4               September 1999

1.  Introduction

   NFS version 4 is a further revision of the NFS protocol defined
   already by versions 2 [RFC1094] and 3 [RFC1813].  It retains the
   essential characteristics of previous versions: design for easy
   recovery, independent of transport protocols, operating systems and
   filesystems, simplicity, and good performance.  The NFS version 4
   revision has the following goals:

   o    Improved access and good performance on the Internet.

        The protocol is designed to transit firewalls easily, perform
        well where latency is high and bandwidth is low, and scale to
        very large numbers of clients per server.

   o    Strong security with negotiation built into the protocol.

        The protocol builds on the work of the ONCRPC working group in
        supporting the RPCSEC_GSS protocol.  Additionally NFS version 4
        provides a mechanism to allow clients and servers to negotiate
        security and require clients and servers to support a minimal
        set of security schemes.

   o    Good cross-platform interoperability.

        The protocol features a filesystem model that provides a useful,
        common set of features that does not unduly favor one filesystem
        or operating system over another.

   o    Designed for protocol extensions.

        The protocol is designed to accept standard extensions that do
        not compromise backward compatibility.

Expires: March 2000                                             [Page 7]


Draft Protocol Specification  NFS version 4               September 1999

2.  RPC and Security Flavor

   The NFS version 4 protocol is a Remote Procedure Call (RPC)
   application that uses RPC version 2 and the corresponding eXternal
   Data Representation (XDR) as defined in [RFC1831] and [RFC1832].  The
   RPCSEC_GSS security flavor as defined in [RFC2203] MUST be used as
   the mechanism to deliver stronger security to NFS version 4.

2.1.  Ports and Transports

   Historically, NFS version 2 and version 3 servers have resided on
   UDP/TCP port 2049. Port 2049 is a IANA registered port number for NFS
   and therefore will continue to be used for NFS version 4.  Using the
   well known port for NFS services means the NFS client will not need
   to use the RPC binding protocols as described in [RFC1833]; this will
   allow NFS to transit firewalls.

   The NFS server SHOULD offer its RPC service via TCP as the primary
   transport. The server SHOULD also provide UDP for RPC service.  The
   NFS client SHOULD also have a preference for TCP usage but may supply
   a mechanism to override TCP in favor of UDP as the RPC transport.

2.2.  Security Flavors

   Traditional RPC implementations have included AUTH_NONE, AUTH_SYS,
   AUTH_DH, and AUTH_KRB4 as security flavors.  With [RFC2203] an
   additional security flavor of RPCSEC_GSS has been introduced which
   uses the functionality of GSS-API [RFC2078].  This allows for the use
   of varying security mechanisms by the RPC layer without the
   additional implementation overhead of adding RPC security flavors.
   For NFS version 4, the RPCSEC_GSS security flavor MUST be used to
   enable the mandatory security mechanism.  The flavors AUTH_NONE,
   AUTH_SYS, and AUTH_DH MAY be implemented as well.

2.2.1.  Security mechanisms for NFS version 4

   The use of RPCSEC_GSS requires selection of: mechanism, quality of
   protection, and service (authentication, integrity, privacy).  The
   remainder of this document will refer to these three parameters of
   the RPCSEC_GSS security as the security triple.

2.2.1.1.  Kerberos V5 as security triple

   The Kerberos V5 GSS-API mechanism as described in [RFC1964] MUST be
   implemented and provide the following security triples.

 columns:

Expires: March 2000                                             [Page 8]


Draft Protocol Specification  NFS version 4               September 1999

 1 == number of pseudo flavor
 2 == name of pseudo flavor
 3 == mechanism's OID
 4 == mechanism's algorithm(s)
 5 == RPCSEC_GSS service

 1      2     3                    4              5
 -----------------------------------------------------------------------
 390003 krb5  1.2.840.113554.1.2.2 DES MAC MD5    rpc_gss_svc_none
 390004 krb5i 1.2.840.113554.1.2.2 DES MAC MD5    rpc_gss_svc_integrity
 390005 krb5p 1.2.840.113554.1.2.2 DES MAC MD5    rpc_gss_svc_privacy
                                   for integrity,
                                   and 56 bit DES
                                   for privacy.

   Note that the pseudo flavor is presented here as a mapping aid to the
   implementor.  Because this NFS protocol includes a method to
   negotiate security and it understands the GSS-API mechanism, the
   pseudo flavor is not needed.  The pseudo flavor is needed for NFS
   version 3 since the security negotiation is done via the MOUNT
   protocol.

   For a discussion of NFS' use of RPCSEC_GSS and Kerberos V5, please
   see [RFC2623].

2.2.1.2.  <another security triple>

        Another GSS-API mechanism will need to be specified here
        along with the corresponding security triple(s).

2.3.  Security Negotiation

   With the NFS version 4 server potentially offering multiple security
   mechanisms, the client will need a way to determine or negotiate
   which mechanism is to be used for its communication with the server.
   The NFS server may have multiple points within its file system name
   space that are available for use by NFS clients.  In turn the NFS
   server may be configured such that each of these entry points may
   have different or multiple security mechanisms in use.

   The security negotiation between client and server must be done with
   a secure channel to eliminate the possibility of a third party
   intercepting the negotiation sequence and forcing the client and
   server to choose a lower level of security than required/desired.

Expires: March 2000                                             [Page 9]


Draft Protocol Specification  NFS version 4               September 1999

2.3.1.  Security Error

   Based on the assumption that each NFS version 4 client and server
   must support a minimum set of security (i.e. Kerberos-V5 under
   RPCSEC_GSS, <ed: add other>), the NFS client will start its
   communication with the server with one of the minimal security
   triples.  During communication with the server, the client may
   receive an NFS error of NFS4ERR_WRONGSEC.  This error allows the
   server to notify the client that the security triple currently being
   used is not appropriate for access to the server's file system
   resources.  The client is then responsible for determining what
   security triples are available at the server and choose one which is
   appropriate for the client.

2.3.2.  SECINFO

   The new procedure SECINFO (see SECINFO procedure definition) will
   allow the client to determine, on a per filehandle basis, what
   security triple is to be used for server access.  In general, the
   client will not have to use the SECINFO procedure except during
   initial communication with the server or when the client crosses
   policy boundaries at the server.  It could happen that the server's
   policies change during the client's interaction therefore forcing the
   client to negotiate a new security triple.

Expires: March 2000                                            [Page 10]


Draft Protocol Specification  NFS version 4               September 1999

3.  File handles

   The file handle in the NFS protocol is a per server unique identifier
   for a file system object.  The contents of the file handle are opaque
   to the client.  Therefore, the server is responsible for translating
   the file handle to an internal representation of the file system
   object.  Since the file handle is the client's reference to an object
   and the client may cache this reference, the server should not reuse
   a file handle for another file system object.  If the server needs to
   reuse a file handle value, the time elapsed before reuse SHOULD be
   large enough that it is likely the client no longer has a cached copy
   of the reused file handle value.

3.1.  Obtaining the First File Handle

   The procedures of the NFS protocol are defined in terms of one or
   more file handles.  Therefore, the client needs a file handle to
   initiate communication with the server.  With NFS version 2 [RFC1094]
   and NFS version 3 [RFC1813], there exists an ancillary protocol to
   obtain this first file handle.  The MOUNT protocol, RPC program
   number 100005, provides the mechanism of translating a string based
   file system path name to a file handle which can then be used by the
   NFS protocols.

   The MOUNT protocol has deficiencies in the area of security and use
   via firewalls.  This is one reason that the use of the public file
   handle was introduced [RFC2054] [RFC2055].  With the use of public
   file handle in combination with the LOOKUP procedure in NFS version 2
   and 3, it has been demonstrated that the MOUNT protocol is
   unnecessary for viable interaction between NFS client and server.

   Therefore, NFS version 4 will not use an ancillary protocol for
   translation from string based path names to a file handle.  Two
   special file handles will be used as starting points for the NFS
   client.

3.1.1.  Root File Handle

   The first of the special file handles is the ROOT file handle.  The
   ROOT file handle is the "conceptual" root of the file system name
   space at the NFS server.  The client uses or starts with the ROOT
   file handle by employing the PUTROOTFH procedure.  The PUTROOTFH
   procedure instructs the server to set the "current" file handle to
   the ROOT of the server's file tree.  Once this PUTROOTFH procedure is
   used, the client can then traverse the entirety of the server's file
   tree with the LOOKUP procedure.  A complete discussion of the server
   name space is in section 7, "NFS Server Name Space".

Expires: March 2000                                            [Page 11]


Draft Protocol Specification  NFS version 4               September 1999

3.1.2.  Public File Handle

   The second special file handle is the PUBLIC file handle.  Unlike the
   ROOT file handle, the PUBLIC file handle may be bound or represent an
   arbitrary file system object at the server.  The server is
   responsible for this binding.  It may be that the PUBLIC file handle
   and the ROOT file handle refer to the same file system object.
   However, it is up to the administrative software at the server and
   the policies of the server administrator to define the binding of the
   PUBLIC file handle and server file system object.  The client may not
   make any assumptions about this binding.

3.2.  File Handle Types

   In NFS version 2 and 3, there was one type of file handle with a
   single set of semantics.  NFS version 4 introduces a new type of file
   handle in an attempt to accommodate certain server environments.  The
   first type of file handle is 'persistent'.  The semantics of a
   persistent file handle are the same as the file handles of NFS
   version 2 and 3.  The second or new type of file handle is the
   'volatile' file handle.

   The volatile file handle type is being introduced to address server
   functionality or implementation issues which prevent correct or
   feasible implementation of a persistent file handle.  Some server
   environments do not provide a file system level invariant that can be
   used to construct a persistent file handle.  The underlying server
   file system may not provide the invariant or the server's file system
   APIs may not provide access to the needed invariant.  Volatile file
   handles may ease the implementation of server functionality such as
   hierarchical storage management or file system reorganization or
   migration.  However, the volatile file handle increases the
   implementation burden for the client but this increased burden is
   deemed acceptable based on the overall gains achieved by the
   protocol.

   Since the client will have different paths of logic to handle
   persistent and volatile file handles, a file attribute is defined
   which may be used by the client to determine the file handle types
   being returned by the server.

3.2.1.  General Properties of a File Handle

   The file handle contains all the information the server needs to
   distinguish an individual file.  To the client, the file handle is
   opaque. The client stores file handles for use in a later request and

Expires: March 2000                                            [Page 12]


Draft Protocol Specification  NFS version 4               September 1999

   can compare two file handles from the same server for equality by
   doing a byte-by-byte comparison, but MUST NOT otherwise interpret the
   contents of file handles. If two file handles from the same server
   are equal, they MUST refer to the same file, but if they are not
   equal, no conclusions can be drawn. Servers SHOULD try to maintain a
   one-to-one correspondence between file handles and files but this is
   not required. Clients MUST only use file handle comparisons only to
   improve performance, not for correct behavior.

   As an example, in the case that two different path names when
   traversed at the server terminate at the same file system object, the
   server SHOULD return the same file handle for each path.  This can
   occur if a hard link is used to create two file names which refer to
   the same underlying file object and associated data.  For example, if
   paths /a/b/c and /a/d/c refer to the same file, the server SHOULD
   return the same file handle for both path names traversals.

3.2.2.  Persistent File Handle

   A persistent file handle is defined as having a persistent value for
   the lifetime of the file system object to which it refers.  Once the
   server creates the file handle for a file system object, the server
   MUST return the same file handle for the object for the lifetime of
   the object.  If the server restarts or reboots, or the filesystem is
   migrated, the NFS server must honor and present the same file handle
   value as it did in the server's previous instantiation.

   The persistent file handle will be become stale or invalid when the
   file system object is removed.  When the server is presented with a
   persistent file handle that refers to a deleted object, it MUST
   return an error of NFS4ERR_STALE.  A file handle may become stale
   when the file system containing the object is no longer available.
   The file system may become unavailable if it exists on removable
   media and the media is no longer available at the server or the file
   system in whole has been destroyed or the file system has simply been
   removed from the server's name space (i.e. unmounted in a Unix
   environment).

3.2.3.  Volatile File Handle

   A volatile file handle does not share the same longevity attributes
   of the persistent file handle.  The server may determine that a
   volatile file handle is no longer valid at many different points in
   time.  If the server can definitively determine that a volatile file
   handle refers to an object that has been removed, the server should
   return NFS4ERR_STALE to the client (as is the case for persistent

Expires: March 2000                                            [Page 13]


Draft Protocol Specification  NFS version 4               September 1999

   file handles).  In all other cases where the server determines that a
   volatile file handle can no longer be used, it should return an error
   of NFS4ERR_EXPIRED.

   The following table shows the most common points at which a volatile
   file handle may expire.  This table represents the view from the
   client's perspective and as such provides columns for when the file
   may be open or closed by the client.

           Server Provides Persistent or Volatile File Handle
                                         File Open        File Closed
   ___________________________________________________________________
   Restart of Server (note 4)            P / V            P / V
   Filesystem Migration (note 5)         P / V            P / V
   SHARE/LOCK recovery                   P / V            N/A (note 1)
   Client RENAMEs object                 P / V            P / V
   Client RENAMEs path to object         P / V            P / V
   Other client RENAMEs object           P / V            P / V
   Other client RENAMEs path to object   P / V            P / V
   Client REMOVEs object                 P / V (note 2)   P / V
   Other client REMOVEs object           P / V            N/A (note 3)

   Note 1
     If the file is not open, persistence of the file handle is not
     applicable for the recovery of SHARE/LOCK.

   Note 2
     With NFS version 2 and 3, when the client removes a file it has
     open it follows the convention of RENAMEing the file to '.nfsXXXX'
     until the file is closed.  At this point the REMOVE is done at the
     server.

        If this same model is used for v4 then this entry will be
        'N/A'.

   Note 3
     If the file is not open by the client, then it should not expect
     any cached file handle to be valid.

   Note 4
     The restart of the NFS server signifies when the operating system
     or NFS software is (re)started.  This also includes High
     Availability configurations where a separate operating system
     instantiation acquires ownership of the file system resources and
     network resources (i.e. disks and IP addresses).

Expires: March 2000                                            [Page 14]


Draft Protocol Specification  NFS version 4               September 1999

   Note 5
     Filesystem migration may occur in response to an unresponsive
     server or when the current server indicates that a filesystem has
     moved by returning NFS4ERR_MOVED.  In both cases, the attribute
     fs_locations designates the new server location for the filesystem.

3.2.4.  One Method of Constructing a Volatile File Handle

   As mentioned, in some instances a file handle is stale (no longer
   valid, perhaps because the file was removed from the server), or it
   is expired (the underlying file is valid, but since the file handle
   is volatile, it may have expired).  Thus the server needs to be able
   to return NFS4ERR_STALE in the former case, and NFS4ERR_FHEXPIRED in
   the latter case. This can be done by careful construction of the
   volatile file handle.  One possible implementation follows.

   A volatile file handle, while opaque to the client could contain:

   [volatile bit = 1 | server boot time | slot | generation number]

   o    slot is an index in the server volatile file handle table

   o    generation number is the generation number for the table
        entry/slot

   If the server boot time is less than the current server boot time,
   return NFS4ERR_FHEXPIRED.  If slot is out of range, return
   NFS4ERR_BADHANDLE.  If the generation number does not match, return
   NFS4ERR_BADHANDLE.

   When the server reboots, the table is gone (it is volatile).

   If volatile bit is 0, then it is a persistent file handle with a
   different structure following it.

3.3.  Client Recovery from File Handle Expiration

   With the introduction of the volatile file handle, the client must
   take on additional responsibility so that it may prepare itself to
   recover from the expiration of a volatile file handle.  If the server
   returns persistent file handles, the client does not need these
   additional steps.

   For volatile file handles, most commonly the client will need to
   store the component names leading up to and including the file system

Expires: March 2000                                            [Page 15]


Draft Protocol Specification  NFS version 4               September 1999

   object in question.  With these names, the client should be able to
   recover by finding a file handle in the name space that is still
   available or by starting at the root of the server's file system name
   space.

   If the expired file handle refers to an object that has been removed
   from the file system, obviously the client will not be able to
   recover from the expired file handle.

   It is also possible that the expired file handle refers to a file
   that has been renamed.  If the file was renamed by another client,
   again it is possible that the original client will not be able to
   recover.  However, in the case that the client itself is renaming the
   file and the file is open, it is possible that the client may be able
   to recover.  The client can determine the new path name based on the
   processing of the rename request.  The client can then regenerate the
   new file handle based on the new path name.  The client could also
   use the compound operation mechanism to construct a set of operations
   like:
           RENAME A B
           LOOKUP B
           GETFH

Expires: March 2000                                            [Page 16]


Draft Protocol Specification  NFS version 4               September 1999

4.  Basic Data Types

   Arguments and results from operations will be described in terms of
   basic XDR types defined in [RFC1832].  The following data types will
   be defined in terms of basic XDR types:

   filehandle: opaque <128>

        An NFS version 4 filehandle.  A filehandle with zero length is
        recognized as a "public" filehandle.

   utf8string:  opaque <>

        A counted array of octets that contains a UTF-8 string.

        Note: Section 11, Internationalization, covers the rational of
        using UTF-8.

   bitmap: uint32 <>

        A counted array of 32 bit integers used to contain bit values.
        The position of the integer in the array that contains bit n can
        be computed from the expression (n / 32) and its bit within that
        integer is (n mod 32).

                                      0            1
                    +-----------+-----------+-----------+--
                    |  count    | 31  ..  0 | 63  .. 32 |
                    +-----------+-----------+-----------+--

   createverf: opaque<8>

        Verify used for exclusive create semantics

   nfstime4
         struct nfstime4 {
             int64_t seconds;
             uint32_t nseconds;
         }

        The nfstime4 structure gives the number of seconds and
        nanoseconds since midnight or 0 hour January 1, 1970 Coordinated
        Universal Time (UTC).  Values greater than zero for the seconds
        field denote dates after the 0 hour January 1, 1970.  Values
        less than zero for the seconds field denote dates before the 0
        hour January 1, 1970.  In both cases, the nseconds field is to
        be added to the seconds field for the final time representation.
        For example, if the time to be represented is one-half second

Expires: March 2000                                            [Page 17]


Draft Protocol Specification  NFS version 4               September 1999

        before 0 hour January 1, 1970, the seconds field would have a
        value of negative one (-1) and the nseconds fields would have a
        value of one-half second (500000000).  Values greater than
        999,999,999 for nseconds are considered invalid.

        This data type is used to pass time and date information.  A
        server converts to and from local time when processing time
        values, preserving as much accuracy as possible. If the
        precision of timestamps stored for a file system object is less
        than defined, loss of precision can occur.  An adjunct time
        maintenance protocol is recommended to reduce client and server
        time skew.

   specdata4
         struct specdata4 {
             uint32_t specdata1;
             uint32_t specdata2;
         }

        This data type represents additional information for the device
        file types NFCHR and NFBLK.

Expires: March 2000                                            [Page 18]


Draft Protocol Specification  NFS version 4               September 1999

5.  File Attributes

   To meet the NFS Version 4 requirements of extensibility and increased
   interoperability with non-Unix platforms, attributes must be handled
   in a more flexible manner.  The NFS Version 3 fattr3 structure
   contained a fixed list of attributes that not all clients and servers
   are able to support or care about, which cannot be extended as new
   needs arise, and which provides no way to indicate non-support.  With
   NFS Version 4, the client will be able to ask what attributes the
   server supports, and will be able to request only those attributes in
   which it is interested.

   To this end, attributes will be divided into three groups: mandatory,
   recommended and named.  Both mandatory and recommended attributes are
   supported in the NFS V4 protocol by a specific and well-defined
   encoding, and are identified by number.  They are requested by
   setting a bit in the bit vector sent in the GETATTR request; the
   server response includes a bit vector to list what attributes were
   returned in response.  New mandatory or recommended attributes may be
   added to the NFS protocol between revisions by publishing a
   standards-track RFC which allocates a new attribute number value and
   defines the encoding for the attribute.

   Named attributes are accessed by the new OPENATTR operation, which
   accesses a hidden directory of attributes associated with a
   filesystem object.  OPENATTR takes a filehandle for the object and
   returns the filehandle for the attribute hierarchy, which is a
   directory object accessible by LOOKUP or READDIR, and which contains
   files whose names represent the named attributes and whose data bytes
   are the value of the attribute.  For example:

          LOOKUP     "foo"       ; look up file
          GETATTR    attrbits
          OPENATTR               ; access foo's named attributes
          LOOKUP     "x11icon"   ; look up specific attribute
          READ       0,4096      ; read stream of bytes

   Named attributes are intended primarily for data needed by
   applications rather than by an NFS client implementation per se; NFS
   implementors are strongly encouraged to define their new attributes
   as recommended attributes by bringing them to the working group.

   The set of attributes which are classified as mandatory is
   deliberately small, since servers must do whatever it takes to
   support them.  The recommended attributes may be unsupported, though
   a server should support as many as it can.  Attributes are deemed

Expires: March 2000                                            [Page 19]


Draft Protocol Specification  NFS version 4               September 1999

   mandatory if the data is both needed by a large number of clients and
   is not otherwise reasonably computable by the client when support is
   not provided on the server.

5.1.  Mandatory Attributes

   These MUST be supported by every NFS Version 4 client and server in
   order to ensure a minimum level of interoperability.  The server must
   store and return these attributes, and the client must be able to
   function with an attribute set limited to these attributes, though
   some operations may be impaired or limited in some ways in this case.
   A client may ask for any of these attributes to be returned by
   setting a bit in the GETATTR request, and the server must return
   their value.

5.2.  Recommended Attributes

   These attributes are understood well enough to warrant support in the
   NFS Version 4 protocol, though they may not be supported on all
   clients and servers.  A client may ask for any of these attributes to
   be returned by setting a bit in the GETATTR request, but must be able
   to deal with not receiving them.  A client may ask for the set of
   attributes the server supports and should not request attributes the
   server does not support.  A server should be tolerant of requests for
   unsupported attributes, and simply not return them, rather than
   considering the request an error.  It is expected that servers will
   support all attributes they comfortably can, and only fail to support
   attributes which are difficult to support in their operating
   environments.  A server should provide attributes whenever they don't
   have to "tell lies" to the client.  For example, a file modification
   time should be either an accurate time or should not be supported by
   the server.  This will not always be comfortable to clients but it
   seems that the client has a better ability to fabricate or construct
   an attribute or do without.

   Most attributes from NFS V3's FSINFO, FSSTAT and PATHCONF procedures
   have been added as recommended attributes, so that filesystem info
   may be collected via the filehandle of any object the filesystem.
   This renders those procedures unnecessary in NFS V4.

5.3.  Named Attributes

   These attributes are not supported by direct encoding in the NFS
   Version 4 protocol but are accessed by string names rather than
   numbers and correspond to an uninterpreted stream of bytes which are

Expires: March 2000                                            [Page 20]


Draft Protocol Specification  NFS version 4               September 1999

   stored with the filesystem object.  The namespace for these
   attributes may be accessed by using the OPENATTR operation to get a
   filehandle for a virtual "attribute directory" and using READDIR and
   LOOKUP operations on this filehandle.  Named attributes may then be
   examined or changed by normal READ and WRITE and CREATE operations on
   the filehandles returned from READDIR and LOOKUP.  Named attributes
   may have attributes, for example, a security label may have access
   control information in its own right.

   It is recommended that servers support arbitrary named attributes.  A
   client should not depend on the ability to store any named attributes
   in the server's filesystem.  If a server does support named
   attributes, a client which is also able to handle them should be able
   to copy a file's data and meta-data with complete transparency from
   one location to another; this would imply that there should be no
   attribute names which will be considered illegal by the server.

   Names of attributes will not be controlled by a standards body.
   However, vendors and application writers are encouraged to register
   attribute names and the interpretation and semantics of the stream of
   bytes via informational RFC so that vendors may interoperate where
   common interests exist.

Expires: March 2000                                            [Page 21]


Draft Protocol Specification  NFS version 4               September 1999

5.4.  Mandatory Attributes - Definitions

   Name              #    DataType     Access   Description
   ___________________________________________________________________
   supp_attr         0    bitmap       READ
                                                The bit vector which
                                                would retrieve all
                                                mandatory and
                                                recommended attributes
                                                which may be requested
                                                for this object.

                                                The client must ask
                                                this question to
                                                request correct
                                                attributes.

   object_type       1    nfs4_ftype   READ
                                                The type of the object
                                                (file, directory,
                                                symlink)

                                                The client cannot
                                                handle object
                                                correctly without
                                                type.

   persistent_fh     2    boolean      READ
                                                Is the filehandle for
                                                this object
                                                persistent?

                                                Server should know if
                                                the filehandles being
                                                provided are
                                                persistent or not.  If
                                                the server is not able
                                                to make this
                                                determination, then it
                                                can choose volatile or
                                                non-persistent.

Expires: March 2000                                            [Page 22]


Draft Protocol Specification  NFS version 4               September 1999

   change            3    uint64       READ
                                                A value created by the
                                                server that the client
                                                can use to determine
                                                if a file data,
                                                directory contents or
                                                attributes have been
                                                modified.  The server
                                                can just return the
                                                file mtime in this
                                                field though if a more
                                                precise value exists
                                                then it can be
                                                substituted, for
                                                instance, a sequence
                                                number.

                                                Necessary for any
                                                useful caching, likely
                                                to be available.

   object_size       4    uint64       R/W
                                                The size of the object
                                                in bytes.

                                                Could be very
                                                expensive to derive,
                                                likely to be
                                                available.

   link_support      5    boolean      READ
                                                Does the object's
                                                filesystem supports
                                                hard links?

                                                Server can easily
                                                determine if links are
                                                supported.

   symlink_support   6    boolean      READ
                                                Does the object's
                                                filesystem supports
                                                symbolic links?

                                                Server can easily
                                                determine if links are
                                                supported.

   named_attr        7    boolean      READ
                                                Does this object have
                                                named attributes?

Expires: March 2000                                            [Page 23]


Draft Protocol Specification  NFS version 4               September 1999

   fsid              8    fsid4        READ
                                                Unique filesystem
                                                identifier for the
                                                filesystem holding
                                                this object.  fsid
                                                contains major and
                                                minor components each
                                                of which are uint64.

   unique_handles    9    boolean      READ
                                                Are two distinct
                                                filehandles guaranteed
                                                to refer to two
                                                different file system
                                                objects?

   lease_time        10   uint32       READ
                                                Duration of leases at
                                                server in seconds.

Expires: March 2000                                            [Page 24]


Draft Protocol Specification  NFS version 4               September 1999

5.5.  Recommended Attributes - Definitions

   Name               #    Data Type      Access   Description
   _____________________________________________________________________
   ACL                11   nfsacl4        R/W
                                                   The access control
                                                   list for the object.
                                                   [The nature and
                                                   format of ACLs is
                                                   still to be
                                                   determined.]

   archive            12   boolean        R/W
                                                   Whether or not this
                                                   file has been
                                                   archived since the
                                                   time of last
                                                   modification
                                                   (deprecated in favor
                                                   of backup_time).

   cansettime         13   boolean        READ
                                                   Whether or not this
                                                   object's filesystem
                                                   can fill in the times
                                                   on a SETATTR request
                                                   without an explicit
                                                   time.

   case_insensitive   14   boolean        READ
                                                   Are filename
                                                   comparisons on this
                                                   filesystem case
                                                   insensitive?

   case_preserving    15   boolean        READ
                                                   Is filename case on
                                                   this filesystem
                                                   preserved?

   chown_restricted   16   boolean        READ
                                                   Will a request to
                                                   change ownership be
                                                   honored?

   filehandle         17   nfs4_fh        READ
                                                   The filehandle of
                                                   this object
                                                   (primarily for
                                                   readdir requests).

Expires: March 2000                                            [Page 25]


Draft Protocol Specification  NFS version 4               September 1999

   fileid             18   uint64         READ
                                                   A number uniquely
                                                   identifying the file
                                                   within the
                                                   filesystem.

   files_avail        19   uint64         READ
                                                   File slots available
                                                   to this user on the
                                                   filesystem containing
                                                   this object - this
                                                   should be the
                                                   smallest relevant
                                                   limit.

   files_free         20   uint64         READ
                                                   Free file slots on
                                                   the filesystem
                                                   containing this
                                                   object - this should
                                                   be the smallest
                                                   relevant limit.

   files_total        21   uint64         READ
                                                   Total file slots on
                                                   the filesystem
                                                   containing this
                                                   object.

   fs_locations       22   fs_locations   READ
                                                   Locations where this
                                                   filesystem may be
                                                   found.  If the server
                                                   returns NFS4ERR_MOVED
                                                   as an error, this
                                                   attribute must be
                                                   supported.

   hidden             23   boolean        R/W
                                                   Is file considered
                                                   hidden?

   homogeneous        24   boolean        READ
                                                   Whether or not this
                                                   object's filesystem
                                                   is homogeneous, i.e.
                                                   whether pathconf is
                                                   the same for all
                                                   filesystem objects.

   maxfilesize        25   uint64         READ
                                                   Maximum supported
                                                   file size for the
                                                   filesystem of this
                                                   object.

Expires: March 2000                                            [Page 26]


Draft Protocol Specification  NFS version 4               September 1999

   maxlink            26   uint32         READ
                                                   Maximum number of
                                                   links for this
                                                   object.

   maxname            27   uint32         READ
                                                   Maximum filename size
                                                   supported for this
                                                   object.

   maxread            28   uint64         READ
                                                   Maximum read size
                                                   supported for this
                                                   object.

   maxwrite           29   uint64         READ
                                                   Maximum write size
                                                   supported for this
                                                   object.  This
                                                   attribute SHOULD be
                                                   supported if the file
                                                   is writable.  Lack of
                                                   this attribute can
                                                   lead to the client
                                                   either wasting
                                                   bandwidth or not
                                                   receiving the best
                                                   performance.

   mime_type          30   utf8<>         R/W
                                                   MIME body
                                                   type/subtype of this
                                                   object.

   mode               31   uint32         R/W
                                                   Unix-style permission
                                                   bits for this object
                                                   (deprecated in favor
                                                   of ACLs)

   no_trunc           32   boolean        READ
                                                   If a name longer than
                                                   name_max is used,
                                                   will an error be
                                                   returned or will the
                                                   name be truncated?

   numlinks           33   uint32         READ
                                                   Number of links to
                                                   this object.

   owner              34   utf8<>         R/W
                                                   The string name of
                                                   the owner of this
                                                   object.

Expires: March 2000                                            [Page 27]


Draft Protocol Specification  NFS version 4               September 1999

   owner_group        35   utf8<>         R/W
                                                   The string name of
                                                   the group of the
                                                   owner of this object.

   quota_hard         36   uint64         READ
                                                   Number of bytes of
                                                   disk space beyond
                                                   which the server will
                                                   decline to allocate
                                                   new space.

   quota_soft         37   uint64         READ
                                                   Number of bytes of
                                                   disk space at which
                                                   the client may choose
                                                   to warn the user
                                                   about limited space.

   quota_used         38   uint64         READ
                                                   Number of bytes of
                                                   disk space occupied
                                                   by the owner of this
                                                   object on this
                                                   filesystem.

   rawdev             39   specdata4      READ
                                                   Raw device
                                                   identifier.

   space_avail        40   uint64         READ
                                                   Disk space in bytes
                                                   available to this
                                                   user on the
                                                   filesystem containing
                                                   this object - this
                                                   should be the
                                                   smallest relevant
                                                   limit.

   space_free         41   uint64         READ
                                                   Free disk space in
                                                   bytes on the
                                                   filesystem containing
                                                   this object - this
                                                   should be the
                                                   smallest relevant
                                                   limit.

   space_total        42   uint64         READ
                                                   Total disk space in
                                                   bytes on the
                                                   filesystem containing
                                                   this object.

Expires: March 2000                                            [Page 28]


Draft Protocol Specification  NFS version 4               September 1999

   space_used         43   uint64         READ
                                                   Number of filesystem
                                                   bytes allocated to
                                                   this object.

   system             44   boolean        R/W
                                                   Whether or not this
                                                   file is a system
                                                   file.

   time_access        45   nfstime4       R/W
                                                   The time of last
                                                   access to the object.

   time_backup        46   nfstime4       R/W
                                                   The time of last
                                                   backup of the object.

   time_create        47   nfstime4       R/W
                                                   The time of creation
                                                   of the object. This
                                                   attribute does not
                                                   have any relation to
                                                   the traditional Unix
                                                   file attribute
                                                   time'.

   time_delta         48   nfstime4       READ
                                                   Smallest useful
                                                   server time
                                                   granularity.

   time_metadata      49   nfstime4       R/W
                                                   The time of last
                                                   meta-data
                                                   modification of the
                                                   object.

   time_modify        50   nfstime4       R/W
                                                   The time since the
                                                   epoch of last
                                                   modification to the
                                                   object.

   version            51   utf8<>         R/W
                                                   Version number of
                                                   this document.

   volatility         52   nfstime4       READ
                                                   Approximate time
                                                   until next expected
                                                   change on this
                                                   filesystem, as a
                                                   measure of
                                                   volatility.

Expires: March 2000                                            [Page 29]


Draft Protocol Specification  NFS version 4               September 1999

5.6.  Interpreting owner and owner_group

   The recommended attributes "owner" and "owner_group" are represented
   in terms of a UTF-8 string.  To avoid a representation that is tied
   to a particular underlying implementation at the client or server,
   the use of the UTF-8 string has been chosen.  Note that section 6.1
   of [RFC2624] provides additional rationale.  It is expected that the
   client and server will have their own local representation of owner
   and owner_group that is used for local storage or presentation to the
   end user.  Therefore, it is expected that the when these attributes
   are transferred between the client and server that the local
   representation is translated to a syntax of the form
   "user@dns_domain".  This will allow for a client and server that do
   not use the same local representation the ability to translate to a
   common syntax that can be interpreted by both.

   The translation is not specified as part of the protocol.  This
   allows various solutions to be employed.  For example, a local
   translation table may be consulted that maps between a numeric id to
   the user@dns_domain syntax.  A name service may also be used to
   accomplish the translation.  The 'dns_domain' portion of the owner
   string is meant to be a DNS domain name.  For example, user@ietf.org.

   In the case where there is no translation available to the client or
   server, the attribute value must be constructed without the '@'.
   Therefore, the absence of the @ from the owner or owner_group
   attribute signifies that no translation was available and the
   receiver of the attribute should not place any special meaning with
   the attribute value.  Even though the attribute value can not be
   translated, it may still be useful.  In the case of a client, the
   attribute string may be used for local display of ownership.

Expires: March 2000                                            [Page 30]


Draft Protocol Specification  NFS version 4               September 1999

6.  Filesystem Migration and Replication

   With the use of the recommended attribute "fs_locations", the NFS
   version 4 server has a method of providing filesystem migration or
   replication services.  For the purposes of migration and replication,
   a filesystem will be defined as all files that share a given fsid
   (major and minor values are the same).

   The fs_locations attribute provides a list of filesystem locations.
   These locations are specified by providing the server name (either
   DNS domain or IP address) and the path name representing the root of
   the filesystem.  Depending on the type of service being provided, the
   list will provide a new or alternate locations for the filesystem.
   The client will use this information to redirect its requests to the
   new server.

6.1.  Replication

   It is expected that filesystem replication will be used in the case
   of read-only data.  Typically, the filesystem will be replicated
   amongst two or more servers.  The fs_locations attribute will provide
   the list of these locations to the client.  On first access of the
   filesystem, the client should obtain the value of the fs_locations
   attribute.  If, in the future, the client finds the server
   unresponsive, the client may attempt to use another server specified
   by fs_locations.

   If applicable, the client must take the appropriate steps to recover
   valid filehandles from the new server.  This is described in more
   detail in the following sections.

6.2.  Migration

   Filesystem migration is used to move a filesystem from one server to
   another.  Migration is typically used for a filesystem that is
   writable and has a single copy.  The expected use of migration is for
   load balancing or general resource reallocation.  The protocol does
   not specify how the filesystem will be moved between servers.  This
   server-to-server transfer mechanism is left to the server
   implementor.  However, the method used to communicate the migration
   event between client and server is specified here.

   Once the servers participating in the migration have completed the
   move of the filesystem, the error NFS4ERR_MOVED will be returned for
   subsequent requests received by the original server.  The
   NFS4ERR_MOVED error is returned for all operations except GETATTR.

Expires: March 2000                                            [Page 31]


Draft Protocol Specification  NFS version 4               September 1999

   Upon receiving the NFS4ERR_MOVED error, the client will obtain the
   value of the fs_locations attribute.  The client will then use the
   contents of the attribute to redirect its requests to the specified
   server.  To facilitate the use of GETATTR operations such as PUTFH
   must also be accepted by the server for the migrated filesystem's
   filehandles.  Note that if the server returns NFS4ERR_MOVED, the
   server MUST support the fs_locations attribute.

   If the client requests more attributes than fs_locations, the server
   may return fs_locations only.  This is to be expected since the
   server has migrated the filesystem and may not have a method of
   obtaining additional attribute data.

   The server implementor needs to be careful in developing a migration
   solution.  The server must consider all of the state information
   clients may have outstanding at the server.  This includes but is not
   limited to locking/share state, delegation state, and asynchronous
   file writes which are represented by WRITE and COMMIT verifiers.  The
   server should strive to minimize the impact on its clients during and
   after the migration process.

6.3.  Interpretation of the fs_locations Attribute

   The fs_location attribute is structured in the following way:

   struct fs_location {
           utf8string      server<>;
           pathname4       rootpath;
   };

   struct fs_locations {
           pathname4       fs_root;
           fs_location     locations<>;
   };

   The fs_location struct is used to represent the location of a
   filesystem by providing a server name and the path to the root of the
   filesystem.  For a multi-homed server or a set of servers that use
   the same rootpath, an array of server names may be provided.  An
   entry in the server array is an UTF8 string and represents one of a
   traditional DNS host name, IPv4 address, or IPv6 address.  It is not
   a requirement that all servers that share the same rootpath be listed
   in one fs_location struct.  The array of server names is provided for
   convenience.  Servers that share the same rootpath may also be listed
   in separate fs_location entries in the fs_locations attribute.

   The fs_locations struct and attribute then contains an array of

Expires: March 2000                                            [Page 32]


Draft Protocol Specification  NFS version 4               September 1999

   locations.  Since the namespace of each server may be constructed
   differently, the "fs_root" field is provided.  The path represented
   by fs_root represents the location of the filesystem in the server's
   namespace.  Therefore, the fs_root path is only associated with the
   server from which the fs_locations attribute was obtained.  The
   fs_root path is meant to aid the client in locating the filesystem at
   the various servers listed.

   As an example, there is a replicated file system located at two
   servers (servA and servB).  At servA the filesystem is located at
   path "/a/b/c".  At servB the filesystem is located at path "/x/y/z".
   In this example the client accesses the filesystem first at servA
   with a multi-component lookup path of "/a/b/c/d".  Since the client
   used a multi-component lookup to obtain the filehandle at "/a/b/c/d",
   it is unaware that the filesystem's root is located in servA's
   namespace at "/a/b/c".  When the client switches to servB, it will
   need to determine that the directory it first referenced at servA is
   now represented by the path "/x/y/z/d" on servB.  To facilitate this,
   the fs_locations attribute provided by servA would have a fs_root
   value of "/a/b/c" and two entries in fs_location.  One entry in
   fs_location will be for itself (servA) and the other will be for
   servB with a path of "/x/y/z".  With this information, the client is
   able to substitute "/x/y/z" for the "/a/b/c" at the beginning of its
   access path and construct "/x/y/z/d" to use for the new server.

6.4.  Filehandle Recovery for Migration or Replication

   Filehandles for filesystems that are replicated or migrated have the
   same semantics as for filesystems that are not replicated or
   migrated.  For example, if a filesystem has persistent filehandles
   and it is migrated to another server, the filehandle values for the
   filesystem will be valid at the new server.

   The same is true for a filesystem which is made up of volatile
   filehandles.  In fact, in this case the client should expect that the
   new server will return NFS4ERR_EXPIRED when old filehandles are
   presented; the client will need to recover the filehandles
   appropriately.

Expires: March 2000                                            [Page 33]


Draft Protocol Specification  NFS version 4               September 1999

7.  NFS Server Namespace

7.1.  Server Exports

   On a UNIX server the name-space describes all the files reachable by
   pathnames under the root directory "/". On a Windows NT server the
   name-space constitutes all the files on disks named by mapped disk
   letters.  NFS server administrators rarely make the entire server's
   file-system name-space available to NFS clients.  Typically, pieces
   of the name-space are made available via an "export" feature.  In
   previous versions of NFS, the root file-handle for each export is
   obtained through the MOUNT protocol; the client sends a string that
   identifies the export of name-space and the server returns the root
   file-handle for it.  The MOUNT protocol supports an EXPORTS procedure
   that will enumerate the server's exports.

7.2.  Browsing Exports

   The NFS version 4 protocol provides a root file-handle that clients
   can use to obtain file-handles for these exports via a multi-
   component LOOKUP.  A common user experience is to use a graphical
   user interface (perhaps a file "Open" dialog window) to find a file
   via progressive browsing through a directory tree. The client must be
   able to move from one export to another export via single-component,
   progressive LOOKUP operations.

   This style of browsing is not well supported by NFS version 2 and 3
   protocols.  The client expects all LOOKUP operations to remain within
   a single server file-system, i.e. the device attribute will not
   change.  This prevents a client from taking name-space paths that
   span exports.

   An automounter on the client can obtain a snapshot of the server's
   name-space using the EXPORTS procedure of the MOUNT protocol. If it
   understands the server's pathname syntax, it can create an image of
   the server's name-space on the client.  The parts of the name-space
   that are not exported by the server are filled in with a "pseudo
   file-system" that allows the user to browse from one mounted file-
   system to another.  There is a drawback to this representation of the
   server's name-space on the client: it is static.  If the server
   administrator adds a new export the client will be unaware of it.

Expires: March 2000                                            [Page 34]


Draft Protocol Specification  NFS version 4               September 1999

7.3.  Server Pseudo File-System

   NFS version 4 servers avoid this name-space inconsistency by
   presenting all the exports within the framework of a single server
   name-space.  An NFS version 4 client uses LOOKUP and READDIR
   operations to browse seamlessly from one export to another. Portions
   of the server name-space that are not exported are bridged via a
   "pseudo file-system" that provides a view of exported directories
   only. A pseudo file-system has a unique fsid and behaves like a
   normal, read-only file-system.

        Based on the construction of the server's name space, it is
        possible that multiple pseudo filesystems may exist.  For
        example,

        /a         pseudo filesystem
        /a/b       real filesystem
        /a/b/c     pseudo filesystem
        /a/b/c/d   real filesystem

        Need to discuss the ramifications of multiple pseudo
        filesystems.

7.4.  Multiple Roots

   DOS, Windows 95, 98 and NT are sometimes described as having
   "multiple roots".  File-Systems are commonly represented as disk
   letters.  MacOS represents file-systems as top-level names.  NFS
   version 4 servers for these platforms can construct a pseudo file-
   system above these root names so that disk letters or volume names
   are simply directory names in the pseudo-root.

7.5.  Filehandle Volatility

   The nature of the server's pseudo file-system is that it is a logical
   representation of file-system(s) available from the server.
   Therefore, the pseudo file-system is most likely constructed
   dynamically when the NFS version 4 is first instantiated.  It is
   expected the pseudo file-system may not have an on-disk counterpart
   from which persistent filehandles could be constructed.  Even though
   it is preferable that the server provide persistent filehandles for
   the pseudo file-system, the NFS client should expect that pseudo
   file-system file-handles are volatile.  This can be confirmed by
   checking the associated "persistent_fh" attribute for those

Expires: March 2000                                            [Page 35]


Draft Protocol Specification  NFS version 4               September 1999

   filehandles in question.  If the filehandles are volatile, the NFS
   client must be prepared to recover a filehandle value (i.e. with a v4
   multi-component LOOKUP) when receiving an error of NFS4ERR_FHEXPIRED.

7.6.  Exported Root

   If the server's root file-system is exported, it might be easy to
   conclude that a pseudo-file-system is not needed.  This would be
   wrong.  Assume the following file-systems on a server:

           /       disk1  (exported)
           /a      disk2  (not exported)
           /a/b    disk3  (exported)

   Because disk2 is not exported, disk3 cannot be reached with simple
   LOOKUPs.  The server must bridge the gap with a pseudo-file-system.

7.7.  Mount Point Crossing

   The server file-system environment may be constructed in such a way
   that one file-system contains a directory which is 'covered' or
   mounted upon by a second file-system. For example:

           /a/b            (file system 1)
           /a/b/c/d        (file system 2)

   The pseudo file-system for this server may be constructed to look
   like:

           /               (place holder/not exported)
           /a/b            (file system 1)
           /a/b/c/d        (file system 2)

   It is the server's responsibility to present the pseudo file-system
   that is complete to the client.  If the client sends a lookup request
   for the path "/a/b/c/d", the server's response is the filehandle of
   the file system "/a/b/c/d".  In previous versions of NFS, the server
   would respond with the directory "/a/b/d/d" within the file-system
   "/a/b".

   The NFS client will be able to determine if it crosses a server mount
   point by a change in the value of the "fsid" attribute.

Expires: March 2000                                            [Page 36]


Draft Protocol Specification  NFS version 4               September 1999

7.8.  Security Policy and Namespace Presentation

   The application of the server's security policy needs to be carefully
   considered by the implementor.  One may choose to limit the
   viewability of portions of the pseudo file-system based on the
   server's perception of the client's ability to authenticate itself
   properly.  However with the support of multiple security mechanisms
   and the ability to negotiate the appropriate use of these mechanisms,
   the server is unable to properly determine if a client will be able
   to authenticate itself.  If, based on its policies, the server
   chooses to limit the contents of the pseudo file-system, the server
   may effectively hide file-systems from a client that may otherwise
   have legitimate access.

7.9.  Summary

   NFS version 4 provides LOOKUP and READDIR operations for browsing of
   NFS file-systems.  These operations are also used to browse server
   exports. A v4 server supports export browsing by including exported
   directories in a pseudo-file-system.  A browsing client can cross
   seamlessly between a pseudo-file-system and a real, exported file-
   system.  Clients must support volatile filehandles and recognize
   mount point crossing of server file-systems.

Expires: March 2000                                            [Page 37]


Draft Protocol Specification  NFS version 4               September 1999

8.  File Locking

   Integrating locking into NFS necessarily causes it to be state-full,
   with the invasive nature of "share" file locks it becomes
   substantially more dependent on state than the traditional
   combination of NFS and NLM [XNFS].  There are three components to
   making this state manageable:

   o    Clear division between client and server

   o    Ability to reliably detect inconsistency in state between client
        and server

   o    Simple and robust recovery mechanisms

   In this model, the server owns the state information.  The client
   communicates its view of this state to the server as needed.  The
   client is also able to detect inconsistent state before modifying a
   file.

   To support Windows "share" locks, it is necessary to atomically open
   or create files.  Having a separate share/unshare operation will not
   allow correct implementation of the Windows OpenFile API.  In order
   to correctly implement share semantics, the existing mechanisms used
   when a file is opened or created (LOOKUP, CREATE, ACCESS) need to be
   replaced.  NFS V4 will have an OPEN procedure that subsumes the
   functionality of LOOKUP, CREATE, and ACCESS.  However, because many
   operations require a file handle, the traditional LOOKUP is preserved
   to map a file name to file handle without establishing state on the
   server.  Policy of granting access or modifying files is managed by
   the server based on the client's state.  It is believed that these
   mechanisms can implement policy ranging from advisory only locking to
   full mandatory locking.  While ACCESS is just a subset of OPEN, the
   ACCESS procedure is maintained as a lighter weight mechanism.

8.1.  Definitions

   Lock      The term "lock" will be used to refer to both record
             (byte-range) locks as well as file (share) locks unless
             specifically stated otherwise.

   Client    Throughout this proposal the term "client" is used to
             indicate the entity that maintains a set of locks on behalf
             of one or more applications. The client is responsible for
             crash recovery of those locks it manages.  Multiple clients
             may share the same transport and multiple clients may exist

Expires: March 2000                                            [Page 38]


Draft Protocol Specification  NFS version 4               September 1999

             on the same network node.

   Clientid  A 64-bit quantity returned by a server that uniquely
             corresponds to a client supplied Verifier and ID.

   Lease     An interval of time defined by the server for which the
             client is irrevokeably granted a lock.  At the end of a
             lease period the lock may be revoked if the lease has not
             been extended.  The lock must be revoked if a conflicting
             lock has been granted after the lease interval.  All leases
             granted by a server have the same fixed interval.

   Stateid   A 64-bit quantity returned by a server that uniquely
             defines the locking state granted by the server for a
             specific lock owner for a specific file.  A stateid
             composed of all bits 0 or all bits 1 have special meaning
             and are reserved.

   Verifier  A 32-bit quantity generated by the client that the server
             can use to determine if the client has restarted and lost
             all previous lock state.

8.2.  Locking

   It is assumed that manipulating a lock is rare when compared to I/O
   operations.  It is also assumed that crashes and network partitions
   are relatively rare.  Therefore it is important that I/O operations
   have a light weight mechanism to indicate if they possess a held
   lock.  A lock request contains the heavy weight information required
   to establish a lock and uniquely define the lock owner.

   The following sections describe the transition from the heavy weight
   information to the eventual stateid used for most client and server
   locking and lease interactions.

8.2.1.  Client ID

   For each LOCK request, the client must identify itself to the server.
   This is done in such a way as to allow for correct lock
   identification and crash recovery.  Client identification is
   accomplished with two values.

   o    A verifier that is used to detect client reboots.

   o    A variable length opaque array to uniquely define a client.

        For an operating system this may be a fully qualified host

Expires: March 2000                                            [Page 39]


Draft Protocol Specification  NFS version 4               September 1999

        name or IP address, and for a user level NFS client it may
        additionally contain a process id or other unique sequence.

   The data structure for the Client ID would then appear as:
           struct nfs_client_id {
                   opaque verifier[4];
                   opaque id<>;
           }

   It is possible through the mis-configuration of a client or the
   existence of a rogue client that two clients end up using the same
   nfs_client_id.  This situation is avoided by 'negotiating' the
   nfs_client_id between client and server with the use of the
   SETCLIENTID.  The following describes the two scenarios of
   negotiation.

   1    Client has never connected to the server

        In this case the client generates an nfs_client_id and
        unless another client has the same nfs_client_id.id field,
        the server accepts the request. The server also records the
        principal (or principal to uid mapping) from the credential
        in the RPC request that contains the nfs_client_id
        negotiation request.

        Two clients might still use the same nfs_client_id.id due
        to perhaps configuration error (say a High Availability
        configuration where the nfs_client_id.id is derived from
        the ethernet controller address and both systems have the
        same address).  In this case, nfs4err can be a switched
        union that returns in addition to NFS4ERR_CLID_INUSE, the
        network address (the rpcbind netid and universal address)
        of the client that is using the id.

   2    Client is re-connecting to the server after a client reboot

        In this case, the client still generates an nfs_client_id
        but the nfs_client_id.id field will be the same as the
        nfs_client_id.id generated prior to reboot.  If the server
        finds that the principal/uid is equal to the previously
        "registered" nfs_client_id.id, then locks associated with
        the old nfs_client_id are immediately released.  If the
        principal/uid is not equal, then this is a rogue client and
        the request is returned in error.  For more discussion of
        crash recovery semantics, see the section on "Crash
        Recovery"

Expires: March 2000                                            [Page 40]


Draft Protocol Specification  NFS version 4               September 1999

   In both cases, upon success, NFS4_OK is returned.  To help reduce the
   amount of data transferred on OPEN and LOCK, the server will also
   return a unique 64-bit clientid value that is a short hand reference
   to the nfs_client_id values presented by the client.  From this point
   forward, the client can use the clientid to refer to itself.

8.2.2.  nfs_lockowner and stateid Definition

   When requesting a lock, the client must present to the server the
   clientid and an identifier for the owner of the requested lock.
   These two fields are referred to as the nfs_lockowner and the
   definition of those fields are:

   o    A clientid returned by the server as part of the clients use of
        the SETCLIENTID procedure

   o    A variable length opaque array used to uniquely define the owner
        of a lock managed by the client.

        This may be a thread id, process id, or other unique value.

   When the server grants the lock it responds with a unique 64-bit
   stateid.  The stateid is used as a short hand reference to the
   nfs_lockowner, since the server will be maintaining the
   correspondence between them.

8.2.3.  Use of the stateid

   All I/O requests contain a stateid.  If the nfs_lockowner performs
   I/O on a range of bytes within a locked range, the stateid returned
   by the server must be used to indicate the appropriate lock (record
   or share) is held. If no state is established by the client, either
   record lock or share lock, a stateid of all bits 0 is used.  If no
   conflicting locks are held on the file, the server may grant the I/O
   request.  If a conflict with an explicit lock occurs, the request is
   failed (NFS4ERR_LOCKED). This allows "mandatory locking" to be
   implemented.

   A stateid of all bits 1 allows read requests to bypass locking checks
   at the server.  However, write requests with stateid with bits all 1
   does not bypass file locking requirements.

   An explicit lock may not be granted while an I/O operation with
   conflicting implicit locking is being performed.

Expires: March 2000                                            [Page 41]


Draft Protocol Specification  NFS version 4               September 1999

   The byte range of a lock is indivisible.  A range may be locked,
   unlocked, or changed between read and write but may not have
   subranges unlocked or changed between read and write.  This is the
   semantics provided by Win32 but only a subset of the semantics
   provided by Unix.  It is expected that Unix clients can more easily
   simulate modifying subranges than Win32 servers adding this feature.

8.2.4.  Sequencing of Lock Requests

   Locking is different than most NFS operations as it requires "at-
   most-one" semantics that are not provided by ONC RPC.  In the face of
   retransmission or reordering, lock or unlock requests must have a
   well defined and consistent behavior.  To accomplish this each lock
   request contains a sequence number that is a monotonically increasing
   integer.  Different nfs_lockowners have different sequences.  The
   server maintains the last sequence number (L) received and the
   response that was returned.  If a request with a previous sequence
   number (r < L) is received it is silently ignored as its response
   must have been received before the last request (L) was sent.  If a
   duplicate of last request (r == L) is received, the stored response
   is returned.  If a request beyond the next sequence (r == L + 2) is
   received it is silently ignored.  Sequences are reinitialized
   whenever the client verifier changes.

8.3.  Blocking Locks

   Some clients require the support of blocking locks.  The current
   proposal lacks a call-back mechanism, similar to NLM, to notify a
   client when the lock has been granted.  Clients have no choice but to
   continually poll for the lock, which presents a fairness problem.
   Two new lock types are added, READW and WRITEW used to indicate to
   the server that the client is requesting a blocking lock.  The server
   should maintain an ordered list of pending blocking locks.  When the
   conflicting lock is released, the server may wait the lease period
   for the first client to re-request the lock.  After the lease period
   expires the next waiting client request is allowed the lock.  Clients
   are required to poll at an interval sufficiently small that it is
   likely to acquire the lock in a timely manner.  The server is not
   required to maintain a list of pending blocked locks as it is used to
   increase fairness and not correct operation.  Because of the
   unordered nature of crash recovery, storing of lock state to stable
   storage would be required to guarantee ordered granting of blocking
   locks.

Expires: March 2000                                            [Page 42]


Draft Protocol Specification  NFS version 4               September 1999

8.4.  Lease Renewal

   The purpose of a lease is to allow a server to remove stale locks
   that are held by a client that has crashed or is otherwise
   unreachable.  It is not a mechanism for cache consistency and lease
   renewals may not be denied if the lease interval has not expired.
   Any I/O request that has been made with a valid stateid is a positive
   indication that the client is still alive and locks are being
   maintained.  This becomes an implicit renewal of the lease.  In the
   case no I/O has been performed within the lease interval, a lease can
   be renewed by having the client issue a zero length READ.  Because
   the nfs_lockowner contains a unique client value, any stateid for a
   client will renew all leases for locks held with the same client
   field.  This will allow very low overhead lease renewal that scales
   extremely well.  In the typical case, no extra RPC calls are needed
   and in the worst case one RPC is required every lease period
   regardless of the number of locks held by the client.

8.5.  Crash Recovery

   The important requirement in crash recovery is that both the client
   and the server know when the other has failed.  Additionally it is
   required that a client sees a consistent view of data across server
   reboots.  All I/O operations that may have been queued within the
   client or network buffers must wait until the client has successfully
   recovered the locks protecting the I/O operations.

8.5.1.  Client Failure and Recovery

   In the event that a client fails, the server may recover the client's
   locks when the associated leases have expired.  Conflicting locks
   from another client may only be granted after this lease expiration.
   If the client is able to restart or reinitialize within the lease
   period the client may be forced to wait the remainder of the lease
   period before obtaining new locks.

   To minimize client delay upon restart, lock requests contain a
   verifier field in the lock_owner.  This verifier is part of the
   initial SETCLIENTID call made by the client.  Since the verifier will
   be changed by the client upon each initialization, the server can
   compare a new verifier to the the verifier associated with currently
   held locks and determine that they do not match.  This signifies the
   client's new instantiation and loss of locking state.  As a result,
   the server is free to release all locks held which are associated
   with the old verifier.

Expires: March 2000                                            [Page 43]


Draft Protocol Specification  NFS version 4               September 1999

   For secure environments, a change in the verifier must only cause the
   release of locks associated with the authenticated requester.  This
   is required to prevent a rogue entity from freeing otherwise valid
   locks.  Note that the verifier must have the same uniqueness
   properties of the COMMIT verifier.

8.5.2.  Server Failure and Recovery

   If the server fails and loses locking state, the server must wait the
   lease period before granting any new locks or allowing any I/O.  An
   I/O request during the grace period with a stale stateid will fail
   with NFS4ERR_GRACE.  To recover the lock and associate state, the
   client will reissue the lock request with reclaim set to TRUE.  Upon
   receiving a successful reply and associated stateid, the client may
   reissue the I/O request with the new stateid.

   Any time a client receives an NFS4ERR_GRACE error, the client must
   assume that all locking state associated with the server returning
   the error has been lost.  The client should start recovering all
   outstanding locks upon receiving NFS4ERR_GRACE.

   If the server receives a lock request during its grace period that
   does not have reclaim set to TRUE, the server must return
   NFS4ERR_GRACE.  This error return will trigger the client to recover
   all of its locking state by reclaiming locks.

   A lock request outside the server's grace period with reclaim set to
   TRUE can only succeed if the server can guarantee that no conflicting
   lock or I/O request has been granted since reboot.

8.5.3.  Network Partitions and Recovery

   If the duration of a network partition is greater than the lease
   period provided by the server, the server will have not received a
   lease renewal from the client.  If this occurs, the server may free
   all locks held for the client.  As a result, all stateids held by the
   client will become invalid.  Once the client is able to reach the
   server after such a network partition, all I/O submitted by the
   client with the now invalid stateids will fail with the server
   returning the error NFS4ERR_EXPIRED.  Once this error is received,
   the client will suitably notify the application that held the lock.

   As a courtesy to the client or optimization, the server may continue
   to hold locks on behalf of a client for which recent communication
   has extended beyond the lease period.  If the server receives a lock
   or I/O request that conflicts with one of these courtesy locks, the

Expires: March 2000                                            [Page 44]


Draft Protocol Specification  NFS version 4               September 1999

   server must free the courtesy lock and grant the new request.

   In the event of a network partition with a duration extending beyond
   the expiration of a client's leases, the server MUST employ a method
   of recording this fact in its stable storage.  Conflicting locks
   requests from another client may be serviced after the lease
   expiration.  There are various scenarios involving server failure
   after such an event that require the storage of these lease
   expirations or network partitions.  One scenario is as follows:

        A client holds a lock at the server and encounters a
        network partition and is unable to renew the associated
        lease.  A second client obtains a conflicting lock and then
        frees the lock.  After the unlock request by the second
        client, the server reboots or reinitializes.  Once the
        server recovers, the network partition heals and the
        original client attempts to reclaim the original lock.

   In this scenario and without any state information, the server will
   allow the reclaim and the client will be in an inconsistent state
   because the server or the client has no knowledge of the conflicting
   lock.

   The server may choose to store this lease expiration or network
   partitioning state in a way that will only identify the client as a
   whole.  Note that this may potentially lead to lock reclaims being
   denied unnecessarily because of a mix of conflicting and non-
   conflicting locks.  The server may also choose to store information
   about each lock that has an expired lease with an associated
   conflicting lock.  The choice of the amount and type of state
   information that is stored is left to the implementor.  In any case,
   the server must have enough state information to enable correct
   recovery from multiple partitions and multiple server failures.

8.6.  Server Revocation of Locks

   At any point, the server can revoke locks held by a client and the
   client must be prepared for this event.  When the client detects that
   its locks have been or may have been revoked, the client is
   responsible for validating the state information between itself and
   the server.  Validating locking state for the client means that it
   must verify or reclaim state for each lock currently held.

   The first instance of lock revocation is upon server reboot or re-
   initialization.  In this instance the client will receive an error or
   NFS4ERR_GRACE and the client will proceed with normal crash recovery
   as described in the previous section.

Expires: March 2000                                            [Page 45]


Draft Protocol Specification  NFS version 4               September 1999

   The second lock revocation event can occur as a result of
   administrative intervention within the lease period.  While this is
   considered a rare event, it is possible that the server's
   administrator has decided to release or revoke a particular lock held
   by the client.  As a result of revocation, the client will receive an
   error of NFS4ERR_EXPIRED and the error is received within the lease
   period for the lock.  In this instance the client may assume that
   only the lock_owner's locks have been lost.  The client notifies the
   lock holder appropriately.  The client may not assume the lease
   period has been renewed as a result of failed operation.

   The third lock revocation event is the inability to renew the lease
   period.  While this is considered a rare or unusual event, the client
   must be prepared to recover.  Both the server and client will be able
   to detect the failure to renew the lease and are capable of
   recovering without data corruption.  For the server, it tracks the
   last renewal event serviced for the client and knows when the lease
   will expire.  Similarly, the client must track operations which will
   renew the lease period and is able to determine lease period
   expiration.

   When the client determines that the lease period has expired, the
   client must mark all locks held for the associated lease as
   "unvalidated".  This means the client has been unable to re-establish
   or confirm the appropriate lock state with the server.  As described
   in the previous section on crash recovery, there are scenarios in
   which the server may grant conflicting locks after the lease period
   has expired for a client.  Once the lease period has expired, the
   client must validate each lock it has held to ensure that a
   conflicting lock has not been granted.  The client may accomplish
   this task by issuing an I/O request, either a pending I/O or zero
   length read.  If the response to the request is success, the client
   has validated the lock and re-established the appropriate state
   between itself and the server.  If the I/O request is not successful,
   the lock was revoked by the server and the client must notify the
   owner.

8.7.  Share Reservations

   A share reservation is a mechanism to control access to a file.  It
   is a separate and independent mechanism from record locking.  When a
   client opens a file, it issues an OPEN request to the server
   specifying the type of access required (READ, WRITE, or BOTH) and the
   type of access to deny others (deny NONE, READ, WRITE, or BOTH).  If
   the OPEN fails the client will fail the applications open request.

   Pseudo-code definition of the semantics:

Expires: March 2000                                            [Page 46]


Draft Protocol Specification  NFS version 4               September 1999

                if ((request.access & file_state.deny)) ||
                      (request.deny & file_state.access))
                              return (NFS4ERR_DENIED)

8.8.  OPEN/CLOSE Procedures

   To provide correct share semantics, a client MUST use the OPEN
   procedure to obtain the initial file handle and indicate the desired
   access and what if any access to deny.  Even if the client intends to
   use a stateid of all 0's or all 1's, it must still obtain the
   filehandle for the regular file with the OPEN procedure.  For clients
   that do not have a deny mode built into their open API, deny equal to
   NONE should be used.

   The OPEN procedure with the CREATE flag, also subsumes the CREATE
   procedure for regular files as used in previous versions of NFS,
   allowing a create with a share to be done atomicly.

        Will expand on create semantics here.

   The CLOSE procedure removes all share locks held by the lock_owner on
   that file.  If record locks are held they should be explicitly
   unlocked.  Some servers may not support the CLOSE of a file that
   still has record locks held; if so, CLOSE will fail and return an
   error.

   The LOOKUP procedure is preserved and will return a file handle
   without establishing any lock state on the server. Without a valid
   stateid, the server will assume the client has the least access.  For
   example, a file opened with deny READ/WRITE cannot be accessed using
   a file handle obtained through LOOKUP.

Expires: March 2000                                            [Page 47]


Draft Protocol Specification  NFS version 4               September 1999

9.  Client-Side Caching

   Client-side caching of data, of file attributes, and of file names is
   essential to providing good performance in NFS.  Providing dis-
   tributed cache-coherence is a difficult problem and previous versions
   of NFS have not attempted it.  Instead, several client implementation
   techniques have been used to reduce the problems that lack of co-
   herence poses for users.  These techniques have not been clearly
   defined by earlier specifications and it is often unclear what is
   valid or invalid client behavior.

   NFS version 4 uses many techniques similar to those that have been
   used in previous versions of NFS.  It does not provide distributed
   cache coherence, but it defines a more limited set of caching
   guarantees to allow locks and share reservation to be used without
   destructive interference from client-side caching.

   In addition, version 4 introduces a delegation mechanism which allows
   many decisions normally made by the server to be made locally by
   clients.  This provides efficient support of the common cases where
   sharing is infrequent or where sharing is read-only.

9.1.  Performance Challenges for Client-Side Caching

   Caching techniques used in previous versions of NFS have been
   successful in providing good performance.  However, several scala-
   bility challenges can arise when those techniques are used with very
   large numbers of clients, particularly when those clients are
   geographically distributed, increasing the latency for cache
   revalidation requests.

   When latencies are large, repeated cache validation requests at open
   time, which NFS-v2 and NFS-v3 clients typically do, can have serious
   performance drawbacks.  A common case is one in which a file is only
   accessed by a single client.  Sharing is infrequent.

   In this case, repeated reference to the server to find that no
   conflicts exist, is expensive.  A better option is to allow a client
   repeatedly opening a file to do so without reference to the server,
   until potentially conflicting operations from another client actually
   occur.

   A similar situation arises in connection with file locking.  Sending
   file lock and unlock requests to the server as well as the I/O
   requests necessary to make data caching consistent with the locking
   semantics (see the section "Data Caching and File Locking") can
   severely limit performance.  When locking is used to provide pro-

Expires: March 2000                                            [Page 48]


Draft Protocol Specification  NFS version 4               September 1999

   tection against infrequent conflicts, a large penalty will be paid,
   which may discourage the use of locking.

   In NFS Version 4, more aggressive caching strategies are designed:

   o    To be compatible with a large range of server semantics.

   o    Provide the same caching benefits as previous versions of NFS
        when unable to provide the more aggressive model.

   o    Requirements for aggressive caching are organized so that a
        large portion of the benefit can be obtained even when not all
        of the requirements can be met.

   The appropriate requirements for the server are discussed in later
   sections in which specific forms of caching are dealt with. (see
   Section "Open Delegation").

        NOTE: [[This discussion of proxy caching assumes that the a
        proxy server appears to the (real) server as an ordinary
        client.  Should there be a proposal for non-transparent
        proxy server support (Mike Eisler's proxy model 2), this
        can be modified.]]

9.2.  Proxy Caching

   Proxy caching is a useful technique to reduce latency and avoid
   server overload when a large number of geographically distributed
   clients share data.  The proxy cache allows many requests to be
   satisfied by a local server, reducing bandwidth and latencies
   associated with accessing the primary server.

   If NFS version 4 were to limit itself to the caching approaches used
   in NFS v2 and NFS v3, a large number of the requests which a proxy
   server would receive would result in corresponding requests to the
   distant server:

   o    All OPEN and CLOSE requests

   o    WRITE requests necessary to flush out dirty data before all file
        close operations.

   o    All LOCK and UNLOCK requests.

Expires: March 2000                                            [Page 49]


Draft Protocol Specification  NFS version 4               September 1999

   o    READ and WRITE requests which must go to the server because
        locks are held or being released.

   o    All directory modification requests (e.g. CREATE, REMOVE, etc.)

   o    All SETATTR requests

   o    Many other requests because of cache entry staleness

   Maintaining distributed caches allowing authoritative decisions to be
   made locally is difficult, in the general case.  However, there are
   many situations in which access patterns allow such decisions to be
   delegated opportunistically to particular clients (such as proxy
   servers) avoiding a great deal of unnecessary communication.  This is
   of particular importance when scaling to very large numbers of
   clients.

9.3.  Delegation and Callbacks

   Recallable delegation of server responsibilities for a file to a
   client (which may include proxy servers) improves performance by
   avoiding repeated requests to the server in the absence of
   interclient conflict.  A server recalls delegated responsibilities,
   using a callback rpc from the server to the client, when another
   client engages in sharing of a delegated file.

   A delegation is passed from the server to the client, specifying the
   object for which the delegation is being done and type of delegation.
   There are different types of delegations but each contains a stateid
   to be used to represent the delegation when performing operations
   that depend on the delegation.  This stateid is similar to those
   associated with locks and share reservations but differs in that the
   stateid for a delegation is associated with a clientid and may be
   used on behalf of all the nfs_lockowner's for the given client.  A
   delegation is made to the client as a whole and not to any specific
   process within it.

   Because callback rpc's may not work in all environments (due to
   firewalls, for example), correct operation does not depend on them.
   Preliminary testing of callback functionality by means of a CB_NULL
   request determines whether callbacks can be supported. The CB_NULL
   request checks the continuity of the callback path. A server makes a
   preliminary assessment of callback availability to a given client and
   avoids delegating responsibilities until it has determined that
   callbacks are supported.  Because client requests for delegation are
   always conditional upon the absence of conflicting access, clients

Expires: March 2000                                            [Page 50]


Draft Protocol Specification  NFS version 4               September 1999

   can not assume that a request for delegation will be granted, and
   must always be prepared for denial.

   Once granted, a delegation behaves in most ways like a lock.  There
   is an associated lease that is subject to renewal together with all
   of the other leases held by that client.

   Unlike locks, a request to a delegated file from a second client will
   cause the server to recall a delegation through a callback.

   On recall, the client holding the delegation must flush modified
   state (such as modified data) to the server and return the
   delegation. The conflicting request will not be responded to until
   the recall is complete, either by the return of the delegation or by
   the server timing out the recall and revoking the delegation.
   Following recall, the server has the information necessary to grant
   or deny second client's request.

   Since recalling a delegation may involve the flushing of substantial
   state to the server, the server should allow a time to complete the
   recall substantially longer than for a typical single RPC.  The
   server may also extend the time allowed if it can determine that
   state is being diligently flushed by the client.  However, the time
   to complete the recall should not be unbounded.

   For example, when responsibility to mediate opens on a given file is
   delegated to a client (see the section "Open Delegation"), the server
   will not know what opens are in effect on the client and thus will be
   unable to determine whether the access and deny state for the file
   allows any particular open until the delegation has been returned.

   Client failure or a network partition can result in failure to
   respond to a recall callback. The server will revoke the delegation,
   rendering any modified state still on the client useless.

9.3.1.  Delegation Recovery

   There are three situations that delegation recovery must deal with:

   o    Client reboot

   o    Server reboot

   o    Network partition (full or callback-only)

Expires: March 2000                                            [Page 51]


Draft Protocol Specification  NFS version 4               September 1999

   In the even of a client reboot, the failure to renew leases will
   result in the revocation of record locks and share reservations.
   Delegations, however, may treated a bit differently.

   Because data associated with some delegations may be written to
   stable storage on the client and because a delegation held by a proxy
   server may be further delegated to its client in turn whereupon the
   proxy server may reboot, there will be situations in which
   delegations will need to be re-established after a client (which
   includes a proxy server) reboots.

   To accommodate such situations, the server may, after leases expire,
   force requests that conflict with existing delegations to wait for a
   longer period of time.  This is consistent with the fact that recall,
   including the time necessary to flush modified state to the server
   and return the delegation, may take significant time.  This longer
   interval would allow clients which reboot to consult stable storage
   and request the reclamation of delegations which have not been timed
   out using this longer interval.  For open delegations, such
   delegations are reclaimed using OPEN with a claim type of
   CLAIM_DELEGATE_PREV.  (See the Sections on "Data Caching and
   Revocation" and "Procedure 17: OPEN" for discussion of open
   delegation and the details of OPEN respectively).

   When the server reboots, delegations are reclaimed (using OPEN with
   CLAIM_DELEGATE_PREV) in a similar fashion to record locks and share
   reservations.  However, there is a slight semantic difference.
   Normally, the server decides that a delegation should not be granted,
   it performs the requested action (e.g. OPEN) without granting any
   delegation.  When this happens as part of reclaim, the server grants
   the delegation but marks it specially so that the client treats the
   delegation as having been granted but recalled by the server so that
   it then has the duty to write all modified state to the server and
   then return the delegation. This handling of delegation reclaim
   reconciles three principles of NFS Version 4:

   o    That upon reclaim, a client faithfully reporting resources
        assigned to it by an earlier server instance, must be granted
        those resources.

   o    That the server has untrammeled authority to determine whether
        delegations are to be granted and, once granted, whether they
        are to be continued.

   o    That the use of callbacks is not to be depended upon until the
        client has proved its ability to receive them.

Expires: March 2000                                            [Page 52]


Draft Protocol Specification  NFS version 4               September 1999

   When a network partition occurs, delegations, like locks and share
   reservations will be subject to freeing when the lease renewal period
   expires, although the server will normally extend the period in which
   conflicting requests are held off in the case of delegations.
   Eventually, however, the occurrence of a conflicting request from
   another client will cause revocation of the delegation.  A blockage
   of the callback (e.g. by later network configuration change) will
   have the same effect.  A recall request will fail and revocation of
   the delegation will result.

   A client normally finds out about revocation of a delegation when it
   uses a stateid associated with a delegation and receives the error
   NFS4ERR_EXPIRED.  It also may find out about delegation revocation
   after a client reboot when it attempts to reclaim a delegation and
   receives that same error.  Note that in the case of a revoked write
   open delegation, there are issues because data may have been modified
   by the client whose delegation is revoked and separately by other
   clients.  See the section "Revocation Recovery for Write Open
   Delegation" for a discussion of such issues.  Note also that when
   delegations are revoked information about the revoked delegation will
   be written by the server to stable storage (as described in section
   7.5) to deal with the case in which a server reboots after revoking a
   delegation but before revoked delegate find out about the revocation.

9.4.  Data Caching

   When programs share access to a set of files they need to be
   implemented so as to take account of the possibility of conflicting
   access by another program.  This is true whether the programs in
   question are on different hosts or reside on the same host.

   Share reservations and record locks are the facilities that NFS v4
   provides to allow programs to co-ordinate access by providing mutual
   exclusion facilities.  NFS v4 data caching must be implemented so
   that it does not vitiate the assumptions that those using these
   facilities depend on.

9.4.1.  Data Caching and OPENs

   In order to avoid invalidating the sharing assumptions that
   applications rely on, NFS v4 clients should not provide cached data
   to applications or modify it on behalf of an application when it
   would not be valid to obtain/modify that same data via a READ or
   WRITE rpc.

Expires: March 2000                                            [Page 53]


Draft Protocol Specification  NFS version 4               September 1999

   Further, in the absence of open delegation (see the Section "Open
   delegation"), two further rules apply.  These rules are obeyed in
   practice by many NFS v2 and NFS v3 clients.

   o    The first rule is that cached data present on a client must be
        revalidated after doing an OPEN, to make sure that the data for
        the file in question, is still validly reflected in the client's
        cache.  This must be done at least when a client open includes
        DENY=WRITE or BOTH, terminating a period in which other clients
        may have had the opportunity to open the file with WRITE access.
        Clients may choose to do the revalidation more often (i.e.  on
        opens specifying DENY=NONE) to parallel NFS v3 practice for the
        benefit of users assuming this degree of cache revalidation.

   o    The second rule, complementary to the first, is that modified
        data must be flushed to the server before closing a file opened
        for write.  If this rule is not adhered to, the revalidation
        done after client OPEN's cannot achieve its purpose.  This data
        must be committed to stable storage before the CLOSE is done
        since retransmission of the data after a server reboot might not
        be possible, once the file is closed.

9.4.2.  Data Caching and File Locking

   When users do not use share reservations to exclude inconsistent
   access, but use file locking instead, there is an analogous set of
   constraints that apply to client side data caching.  These rules are
   effective only if file locking is used in a way which is congruent
   with the actual IO operations being done, as opposed to being used in
   a purely conventional way.  For example, it is possible to manipulate
   a 2MB file, dividing the file into two 1MB regions, and using a lock
   for write on byte 0 of the file to represent the right to do IO to
   the first region and a lock for write to byte 1 of the file to
   represent the right to do IO on the second region.  As long as all
   applications manipulating the file obey this convention, they will
   work on a local file system, but they may not work on NFS v4 unless
   clients refrain from data caching.

   The first rule is that when a client locks a region, it must
   revalidate its data cache if it has any cached data in the region
   newly locked and invalidate it if the change attribute shows that the
   file may have been written since that data was obtained.  (A client
   might choose to invalidate all of non-modified cached data that it
   has, but invalidating all of the data in the newly locked region is
   necessary for correct operation).

Expires: March 2000                                            [Page 54]


Draft Protocol Specification  NFS version 4               September 1999

   The second rule is that before releasing a write lock for a region,
   all modified data for that region must be flushed to the server
   (although not necessarily to disk).

   Note that flushing data to the server and the invalidation of cached
   data must reflect the actual byte ranges locked or unlocked.
   Rounding these up or down to reflect client cache block boundaries
   will cause problems if not carefully done.  For example, writing a
   modified block when only half of that block is within an area being
   unlocked may cause invalid modification to the region outside the
   unlocked area which may be part of a region locked by another client.
   Clients can avoid this situation by synchronously performing portions
   of write operations that overlap that portion (initial or final) that
   is not a full block.  Similarly, invalidating a locked area which is
   not an integral number of full buffer blocks would require the client
   to read one or two partial blocks from the server if the revalidation
   procedure shows that the data which the client possesses may not be
   valid.

   Writes required to flush data before unlocking must be done to stable
   storage, either by doing synchronous writes or a COMMIT as part of
   the flush operation.  The is so because retransmission of the
   modified data after a server reboot might conflict with a lock held
   by another client.

   Clients may choose to accommodate programs using record locking in
   non-standard ways (e.g. using a record lock as a global semaphore),
   by flushing to the server more data upon an UNLOCK than is covered by
   the locked range, possibly including modified data in other files.
   Any client doing so must ensure that for any file in which all data
   written is to properly locked areas, no piece of data be written to
   the server which is not within the locked area.

9.4.3.  Data Caching and Mandatory File Locking

   Client side data caching needs to respect mandatory file locking when
   this is in effect.  The presence of mandatory file locking for a
   given file is indicated in the result flags for an OPEN.  When there
   is a read or write for a file for which mandatory locking is in
   effect, the client must check if it holds an appropriate lock for the
   range of bytes being read or written.  If it does, it may satisfy the
   request using client side caching, just as for any other read or
   write.  If such a lock is not held, the read or write cannot be
   satisfied by caching but must be sent to the server.  When a request
   partially overlaps a locked area, the request should be broken up
   into multiple pieces with each region (locked or not) treated

Expires: March 2000                                            [Page 55]


Draft Protocol Specification  NFS version 4               September 1999

   appropriately.

9.4.4.  Data Caching and File Identity

   When clients cache data, data needs to organized according to the the
   file system object to which the data belongs.  For NFS v3 clients,
   the typical practice has been to assume (for this purpose) that
   distinct handles represent distinct filesystem objects (even though
   in some unusual cases this has not been the case) and that the data
   cache may be maintained on the this basis.

   In NFS v4, we have the prospect (due to pathname based handles) of
   more significant deviations from a one-filehandle-per-object model.
   This requires some method by which clients may reliably determine
   whether two filehandles designate the same object.  If they were to
   simply assume that all distinct filehandles denoted distinct objects
   and proceeded to do data caching on that basis, caching
   inconsistencies would arise between the distinct client side objects
   which mapped to the same server side object.  While it is true that
   such inconsistencies would be similar to those typically seen by
   programs running on multiple clients (apart from this issue), these
   inconsistencies would not be expected an NFS v3 clients not sharing
   files with any other client.  The appearance of such inconsistencies
   would be a definite problem inhibiting transition from NFS v3 to NFS
   v4 and so must be avoided.

   The following procedure allows an NFS v4 client to determine (for the
   purposes of data caching) whether two distinct filehandles denote the
   same server side object:

   o    If GETATTR directed to the two handles in question have
        different values of fsid.major or fsid.minor, then they are
        distinct objects.

   o    If GETATTR for any file on the fsid (major and minor) to which
        the two handles belong and unique_handles is TRUE, then the two
        objects are distinct.

   o    If GETATTR directed to the two handles does not return the
        fileid attribute for one or both of the handles, then the it
        cannot be determined whether the two objects are the same and so
        operations which depend on that knowledge (e.g. client side data
        caching) cannot be done reliably.

   o    If the two GETATTR's return different values for the fileid

Expires: March 2000                                            [Page 56]


Draft Protocol Specification  NFS version 4               September 1999

        attribute, then they are distinct objects.

   o    Otherwise they are the same object.

9.5.  Open Delegation

   When a file is being opened, the server may delegate further handling
   of opens and closes for that file to the opening client.  Any such
   delegation is recallable, since the circumstances that occasioned it
   are subject to change.  In particular, the server may receive a
   conflicting OPEN from another client, which obliges it to recall the
   delegation before deciding whether the OPEN may be granted.  Granting
   a delegation request is up to the server and it may deny all such
   requests.  The following is a typical set of conditions that servers
   might use in deciding whether open should be delegated:

   o    The client must be able to respond to callbacks (as evidenced by
        responding to previous CB_NULL requests).

   o    The client must not have failed to respond properly to previous
        recalls.

   o    There must be no current open conflicting with the requested
        delegation.

   o    There should be no current delegation that conflicts with the
        delegation being requested.

   o    The probability of future conflicting open requests should be
        low based on the recent history of the file.

   o    The existence of any server specific semantics of OPEN/CLOSE
        that would make the required handling incompatible with the
        prescribed handling that the delegated client would apply (see
        below).

   There are two types of open delegations, read and write.  A read open
   delegation allows a client to handle, on its own, requests to open a
   file for reading that do not deny read access to others. Multiple
   read open delegations may be outstanding simultaneously and do not
   conflict.  A write open delegation allows the client to handle on its
   own all opens.  Only one write open delegation may exist for a given
   file at a given time and it is inconsistent with any read open

Expires: March 2000                                            [Page 57]


Draft Protocol Specification  NFS version 4               September 1999

   delegations.

   When a client has a read open delegation, it may not make any changes
   to the contents or attributes of the file but it is assured that no
   other client may do so.  When a client has a write open delegation it
   may modify the file data as it wishes secure in the knowledge that no
   other client is accessing the file's data.  The client holding a
   write delegation may only affect file attributes which are intimately
   connected with the file data:  length, modify_time, change.

   When a client has an open delegation, it does not send OPEN's, or
   CLOSE's to the server but updates the appropriate status internally.
   For a read open delegation, opens that cannot be handled locally
   (opens for write or that deny read access) must go to the server.

   When an open delegation is requested and granted, the response to the
   OPEN contains an open delegation structure which specifies, the type
   of delegation (read or write), space limitation information to
   control flushing of data on close (write open delegation only, see
   the Section "Open Delegation and Data Caching"), an nfsacl4
   specifying read and write permissions and a stateid to represent the
   delegation when doing IO.  This stateid is separate and distinct from
   the stateid for the OPEN proper, which, unlike the delegation
   stateid, is associated with a particular nfs_lockowner, and will
   continue to be valid after the delegation is recalled, if the file
   remains open.

   When an internal request (or a request by one of a proxy server's
   clients) is made to open a file when open delegation is in effect, it
   will be accepted or rejected solely on the basis of the following
   conditions.  Any requirement for other checks to be made by the
   delegate, should result in open delegation being denied so that the
   checks can be made by the server itself.

   o    The access and deny bits for the request and the file as
        described in Section 7.7, Share reservations

   o    The read and write permissions as determined below.

   The nfsacl4 passed with delegation can be used to avoid frequent
   ACCESS calls.  The permission check should be as follows:

   o    If the nfsacl4 indicates that the open may be done, then it
        should be granted, without reference to the server.

Expires: March 2000                                            [Page 58]


Draft Protocol Specification  NFS version 4               September 1999

   o    If the nfsacl4 indicates that the open may not be done, then an
        ACCESS request must be made to the server to obtain the
        definitive answer.

   The server may thus return an nfsacl4 that is more restrictive than
   the actual ACL of the file, including one that specifies denial of
   all access.  Note that some common practices like mapping root to
   nobody may make it incorrect to send the actual ACL of the file in
   some cases.

   The use of delegation together with various other forms of caching
   creates the possibility that no server authentication will ever be
   performed on a given user since all of his requests might be
   satisfied locally.  Where the client is depending of the server for
   authentication, it should make sure that some authentication (via an
   ACCESS call) happens for each user, even if an ACCESS call would not
   otherwise be required.  The server may enforce frequent
   authentication by returning an nfsacl4 denying all access with every
   open delegation.

9.5.1.  Open Delegation and Data Caching

   Open delegation allows much of the message overhead associated with
   opening and close files to be eliminated.  This is also the case for
   a proxy server to which an open delegation was made but which did not
   pass the delegation on.  In either case, an open when an open
   delegation was in effect would not require that a validation message
   be sent to the server.  The continued endurance of the read-open-
   delegation provides a guarantee that no open for write and thus no
   write has occurred.  Similarly, when closing a file opened for write,
   if write open delegation is in effect, the data written does not have
   to be flushed to the server until the open delegation is recalled.
   The continued endurance of the open delegation provides a guarantee
   that no open and thus no read or write has been done by another
   client.

   For the purposes of open delegation, IO done without an OPEN (via
   special stateid's consisting of all zero bits or all one bits) are
   treated as the functional equivalent of a corresponding type of open.
   Thus, such READ's or WRITE's done by another client need will provoke
   recall of a write open delegation, will any such WRITE will provoke
   recall of a read open delegation.

   In order to maintain current semantics in which the non-availability
   of storage to hold a file written by an NFS client is guaranteed to

Expires: March 2000                                            [Page 59]


Draft Protocol Specification  NFS version 4               September 1999

   be determined at or before the associated close operation, the
   avoidance by the client of the requirement to flush data to the
   server on close, is limited to cases in which the client and server
   together can determine in advance that the required space will be
   available.  The server specifies one of a number of limiting
   conditions, either a limit on the size of the file or a limit on the
   number of modified blocks using a blocksize supplied by the server.
   Based on implementation experience, changes in the form of these
   conditions may be made or new types of limiting conditions defined.
   Whatever the form of condition used, it us up to the server to ensure
   that any set of writes, no matter how arranged that meets the
   specified condition will ever encounter a lack of disk space
   availability when the modified data is allowed to remain on the
   client unflushed to the server past the point of close.  The server
   must make sure that the maximum possible amount of storage is
   reserved so that all outstanding delegations together meet that
   condition, and to recall delegations appropriately to maintain that
   invariant.  When a server implements quotas, it should also be
   careful that it does not invalidate its quota invariants when
   granting write open delegation.  When a user is near a quota limit,
   this may result in write open delegations granted with very
   restrictive space limitation conditions or those which always force
   modified data to be flushed to the server on close.

   When authentication considerations make flushing of modified data to
   the server after the close problematic (after the last close, the
   user may have logged off and unexpired local credentials may not
   exist), the client may need to take special care to ensure that local
   unexpired credentials will in fact be available, either by tracking
   the expiration time of credentials and flushing data well in advance
   of their expiration, or by making private copies of credentials to
   assure their availability when needed.

9.5.2.  Open Delegation and File Locks

   When a client holds a write-open-delegation, lock operations,
   including those required by mandatory file locking are performed
   locally since the delegation implies that there can be no conflicting
   locks.  On a similar basis, all of the revalidations that would
   normally be associated with obtaining locks and the flushing of data
   which would attend the releasing of locks for write need not be done.

9.5.3.  Recall of Open Delegation

Expires: March 2000                                            [Page 60]


Draft Protocol Specification  NFS version 4               September 1999

   The following events necessitate recall of an open delegation:

   o    Potentially conflicting OPEN request (or IO done with "special"
        stateid)

   o    SETATTR issued by another client

   o    REMOVE request for the file in question

   o    RENAME request for the file in question as either source or
        target of the RENAME

        NOTE: [[The following are necessary unless the spec is
        cleaned up to disallow LOCK's and IO operations without a
        corresponding OPEN.]]

   o    LOCK request by another client.

   o    IO operation done with "special" stateid by another client.

   Whether a RENAME of a directory in the path leading to the file
   results in recall of an open delegation depends on the semantics of
   the server file system.  If that filesystem denies such RENAME's when
   a file is open, the recall must be performed to determine whether the
   file in question is, in fact, open.

   In addition to the situations above, the server may choose to recall
   open delegations at any time if resource constraints make it
   advisable to do so.  Clients should always be prepared for the
   possibility of recall.

   Special handling is needed for a GETATTR which occurs when a write
   open delegation is in effect.  In this case, the client holding the
   delegation needs to be interrogated, using a CB_GETATTR callback, if
   the GETATTR attribute bits include any of the attributes that a write
   open delegate may modify (length, modify time, change).

   When a client receives a recall for an open delegation, it needs to
   update state on the server before returning the delegation.  These
   same updates must be done whenever a client chooses to return a
   delegation voluntarily.  The following items of state need to be
   dealt with:

Expires: March 2000                                            [Page 61]


Draft Protocol Specification  NFS version 4               September 1999

   o    If the open file associated with the OPEN which delivered the
        delegation to the client is no longer open, then a CLOSE must be
        done to the server, if this has not been done previously.

   o    If there are other opens extant for that file, then OPEN
        operations must be done to update the server and obtain the
        stateid's to be used subsequently, given that the delegation
        stateid will no longer be valid.  Such OPEN's are done using a
        claim type of CLAIM_DELEGATE_CUR so that the delegation stateid
        can be presented to the server to establish the client's right
        to perform this OPEN.  (See the section "Procedure 17: OPEN" for
        details).

   o    If there are locks which have been granted (write open
        delegation case only), then these need to be performed to the
        server.

   In the case of a write open delegation, if the file in question is
   not opened for write at the time of recall, then any modified data
   for the file needs to be flushed to the server, as it would have been
   flushed when the file was closed, had the write open delegation not
   been in effect.  The possibility of truncation on the client means
   that the following needs to be done:

   o    If a file truncate has been done on the client (as part of an
        OPEN UNCHECKED, for example), and this has not yet been
        propagated to the server (it must be before allowing any new
        data to be written to the server), it must be done as part of
        recall, again before writing modified data to the server.

   o    Any modified data for the file needs to be flushed to the the
        server.

   In the case of write open delegation, file locking imposes some
   additional requirements.  The flushing of any modified data in any
   area for which a write lock was released while the write open
   delegation was in effect is what is required to precisely maintain
   the associated invariant.  However, because the write open delegation
   implies no other locking by other clients, a simpler implementation
   is to flush all modified data for the file (as described just above)
   if any write lock has been released while the write open delegation
   was in effect.

Expires: March 2000                                            [Page 62]


Draft Protocol Specification  NFS version 4               September 1999

9.5.4.  Delegation Revocation

   When a delegation is revoked, if there are associated opens on the
   client, the processes holding these opens need to be notified,
   normally by returning errors whenever IO operations or a close is
   attempted on that open file.

   When an open delegation is revoked, if no opens are present on the
   client, then no error needs to be reported, unless there is modified
   data present on the client.  In this case, the user will have to be
   notified, since there may not be an active application to get an
   error status.  (See the section "Revocation Recovery for Write Open
   Delegation" for more details).

9.6.  Data Caching and Revocation

   When locks (including delegations) are revoked, the assumptions upon
   which successful caching depend, are no longer guaranteed.  Therefore
   the client, in addition to notifying the owner of a record lock or
   share reservation, and processes holding opens for the delegation,
   needs to remove all data for the file from its cache.  In the case of
   modified data, it must be removed from the client's cache without
   being written to the server.

   Notification to the lock owner will in many cases consist of simply
   returning an error on the next (and all subsequent) IO to the open
   file or on the close.  Where the client API make such notification
   impossible (because errors for certain operations may not be
   returned), more drastic action such as signals or process termination
   may be appropriate since an invariant that an application depends on
   may be violated.  Depending on how errors are typically treated on
   the client operating system, further levels of notification including
   logging, console messages, and GUI pop-up's may be in order.

9.6.1.  Revocation Recovery for Write Open Delegation

   Revocation recovery for a write open delegation poses the issue in
   that there may be modified data in the client cache while the file is
   not open.  In this situation, any client which does not flush
   modified data to the server on each close must make sure that the
   user receives appropriate notification of the failure.  Since such
   situations may require human action to correct problems, notification
   schemes in which the appropriate user or administrator is notified

Expires: March 2000                                            [Page 63]


Draft Protocol Specification  NFS version 4               September 1999

   may be necessary.  Logging and console messages are typical examples.

   If there is modified data on the client, it must not be flushed
   normally to the server.  A client may attempt to provide a copy of
   the file data as modified during the delegation under a different
   name, to ease recovery.  Unless the client can determine that the
   file was has not modified by any other client, this technique is
   limited to situations in which a client has a complete cached copy of
   the file in question.  Use of such a technique may be limited to
   files under a certain size or may only be used when sufficient disk
   space is guaranteed available within the target file system and when
   the client has sufficient buffering resources to keep the cached copy
   available until it is properly stored to the target file system.

9.7.  Attribute Caching

   First note that when attributes are discussed here, extended or named
   attributes are not included.  Individual named attributes are
   analogous to files and caching of the data for these needs to be
   handled just as data caching is for ordinary files. Similarly, LOOKUP
   results from an OPENATTR directory are to be cached on the same basis
   as any other pathnames and similarly for directory contents.

   Clients may cache file attributes obtained from the server and use
   them to avoid subsequent GETATTR requests.  Such caching is write
   through in that modification to file attributes is always done by
   means of requests to the server and should not be done locally and
   cached, the exception being modifications to attributes that are
   intimately connected with data caching.  Thus, extending a file by
   writing data to the local data cache is reflected immediately in the
   length as seen on the client without this change being immediately
   reflected on the server.  Normally such changes are not propagated
   directly to the server, but when the modified data is flushed to the
   server, analogous attribute changes are made on the server.  When
   open delegation is in effect, the modified attributes may be returned
   to the server in the response to a CB_RECALL call.

   The result of local caching of attributes is that the attribute
   caches maintained on individual clients will not be coherent. Changes
   made in one order on the server may be seen in a different order on
   one client and in a third order on a different client.

   Given that typical file API's do not provide means to atomically
   modify or interrogate attributes for multiple files at the same time,
   the undesirable effects of these incoherencies have proved
   manageable, if the following rules, derived from the practice of

Expires: March 2000                                            [Page 64]


Draft Protocol Specification  NFS version 4               September 1999

   NFSv3 implementations are followed:

   o    All attributes for a given file (per-fsid attributes excepted)
        are cached as a unit so that no non-serializability can arise
        within the context of a single file.

   o    A bound is maintained on how long a client cache entry can be
        kept without being refreshed from the server.

   o    When performing any operation that changes attributes on the
        server, including directory operations that due so indirectly,
        updated attributes would be fetched as part of the associated
        rpc, using a GETATTR following the operation in question, which
        the results of the GETATTR used to update the client's attribute
        cache.

   Note that if the full set of attributes to be cached is requested by
   READDIR, the results can be cached by the client on the same basis as
   attributes obtained GETATTR.

   A client may validate its cached version of attributes for a file by
   fetching only the change attribute and assuming that if the change
   attribute has the same value as it did when the attributes were
   cached, then no attributes have changed, with the possible exception
   of access_time.

9.8.  Name Caching

   The results of LOOKUP and READDIR operations may be cached to avoid
   the cost of subsequent LOOKUP operations.  Just as in the case
   attribute caching, inconsistencies may arise among the various client
   caches.  To mitigate the effects of these inconsistencies, given the
   context of typical file API's, the following rules should be adhered
   to:

   o    The results of unsuccessful LOOKUP's should not cached, unless
        they are specifically reverified at the point of use.

   o    A bound is maintained on how long a client name cache entry can
        be kept without verifying that the entry in question has not
        been made invalid by a directory change operation performed by
        another client.

Expires: March 2000                                            [Page 65]


Draft Protocol Specification  NFS version 4               September 1999

   When a client is not making changes to a directory for which there
   exist name cache entries, it needs to periodically fetch attributes
   for that directory to make sure that it is not changing.  After
   determining that no change that has occurred, the expiration time for
   the associated name cache entries may be updated to be the current
   time plus the name cache staleness bound.

   When a client is making changes to a given directory, it needs to
   determine whether there have been changes made to the directory by
   other clients.  It does this using the change attribute as reported
   before and after the directory operation in the associated wcc4_info
   returned on that operation.  When the server is able to report these
   values atomically with respect to the directory operation, which the
   server indicates in the wcc4_info, comparison of the pre-operation
   change value with the change value which the client has in his cache
   determines whether there has been a change by another client,
   necessitating a purge of name cache associated with the directory.
   If there has been no such change, the name cache can be updated on
   the client to reflect the directory operation and the associated
   timeout extended.  The post-operation change value needs to be saved
   as the basis for future wcc4_info comparisons.

   Name caching requires that the client revalidate cached data by
   comparing the change attribute for a directory when the name item was
   cached.  This requires that any changes in the contents of a
   directory be visible as a changed value for the change attribute of
   the directory.  Proper use of wcc4_info, when a client makes a change
   to a directory, requires that reporting of the pre-operation and
   post-operation change attribute values are in fact atomic with the
   actual directory change.  When the server cannot reliably report
   before and after values atomically with respect to the directory
   operation, the server indicates that in the wcc4_info and the client
   should not assume that other clients have not changed the directory.

9.9.  Directory Caching

   The results of READDIR operations may be used to avoid subsequent
   READDIR operations.  Just as in the cases of attribute and name
   caching, this may result in inconsistencies among the various client
   caches.  To mitigate the effects of these inconsistencies, given the
   context of typical file API's, the following rules should be adhered
   to:

   o    Cached READDIR information for a directory which is not obtained
        in a single READDIR operation must always be a consistent

Expires: March 2000                                            [Page 66]


Draft Protocol Specification  NFS version 4               September 1999

        snapshot of directory contents as evidenced by a GETATTR before
        the first and after the last of READDIR's which contribute.

   o    A bound is maintained on the amount of time that a directory
        cache entry may be kept on the client without revalidation.

   The revalidation technique parallels that discussed in the case of
   name caching.  When the client is not changing the directory in
   question, checking that the directory has not changed (by using
   GETATTR to obtain the change attribute) is adequate to extend the
   lifetime of the cache entry.  When a client is modifying the
   directory, it needs to use the wcc4_info data to determine whether
   there are other clients who are modifying the directory, allowing it
   to update the directory cache to reflect its own changes if it is the
   only client making modifications.

   Directory caching requires that the client revalidate cached data by
   comparing the change attribute for a directory when the directory
   data was cached.  This requires that any changes in the contents of a
   directory be visible as a changed value for the change attribute of
   the directory.  Proper use of wcc4_info, when a client makes a change
   to a directory, require that reporting of the pre-operation and
   post-operation change attribute values are in fact atomic with the
   actual directory change. When the server cannot reliably report
   before and after values atomically with respect to the directory
   operation, the server indicates that in the wcc4_info and the client
   should not assume that other clients have not changed the directory.

Expires: March 2000                                            [Page 67]


Draft Protocol Specification  NFS version 4               September 1999

10.  Defined Error Numbers

   NFS error numbers are assigned to failed operations within a compound
   request.  A compound request contains a number of NFS operations that
   have their results encoded in sequence in a compound reply.  The
   results of successful operations will consist of an NFS4_OK status
   followed by the encoded results of the operation.  If an NFS
   operation fails, an error status will be entered in the reply and the
   compound request will be terminated.

   A description of each defined error follows:

   NFS4_OK               Indicates the operation completed successfully.

   NFS4ERR_PERM          Not owner. The operation was not allowed
                         because the caller is either not a privileged
                         user (root) or not the owner of the target of
                         the operation.

   NFS4ERR_NOENT         No such file or directory. The file or
                         directory name specified does not exist.

   NFS4ERR_IO            I/O error. A hard error (for example, a disk
                         error) occurred while processing the requested
                         operation.

   NFS4ERR_NXIO          I/O error. No such device or address.

   NFS4ERR_ACCES         Permission denied. The caller does not have the
                         correct permission to perform the requested
                         operation. Contrast this with NFS4ERR_PERM,
                         which restricts itself to owner or privileged
                         user permission failures.

   NFS4ERR_EXIST         File exists. The file specified already exists.

   NFS4ERR_XDEV          Attempt to do a cross-device hard link.

   NFS4ERR_NODEV         No such device.

Expires: March 2000                                            [Page 68]


Draft Protocol Specification  NFS version 4               September 1999

   NFS4ERR_NOTDIR        Not a directory. The caller specified a non-
                         directory in a directory operation.

   NFS4ERR_ISDIR         Is a directory. The caller specified a
                         directory in a non-directory operation.

   NFS4ERR_INVAL         Invalid argument or unsupported argument for an
                         operation. Two examples are attempting a
                         READLINK on an object other than a symbolic
                         link or attempting to SETATTR a time field on a
                         server that does not support this operation.

   NFS4ERR_FBIG          File too large. The operation would have caused
                         a file to grow beyond the server's limit.

   NFS4ERR_NOSPC         No space left on device. The operation would
                         have caused the server's file system to exceed
                         its limit.

   NFS4ERR_ROFS          Read-only file system. A modifying operation
                         was attempted on a read-only file system.

   NFS4ERR_MLINK         Too many hard links.

   NFS4ERR_NAMETOOLONG   The filename in an operation was too long.

   NFS4ERR_NOTEMPTY      An attempt was made to remove a directory that
                         was not empty.

   NFS4ERR_DQUOT         Resource (quota) hard limit exceeded. The
                         user's resource limit on the server has been
                         exceeded.

   NFS4ERR_STALE         Invalid file handle. The file handle given in
                         the arguments was invalid. The file referred to
                         by that file handle no longer exists or access
                         to it has been revoked.

Expires: March 2000                                            [Page 69]


Draft Protocol Specification  NFS version 4               September 1999

   NFS4ERR_BADHANDLE     Illegal NFS file handle. The file handle failed
                         internal consistency checks.

   NFS4ERR_NOT_SYNC      Update synchronization mismatch was detected
                         during a SETATTR operation.

   NFS4ERR_BAD_COOKIE    READDIR cookie is stale.

   NFS4ERR_NOTSUPP       Operation is not supported.

   NFS4ERR_TOOSMALL      Buffer or request is too small.

   NFS4ERR_SERVERFAULT   An error occurred on the server which does not
                         map to any of the legal NFS version 4 protocol
                         error values.  The client should translate this
                         into an appropriate error.  UNIX clients may
                         choose to translate this to EIO.

   NFS4ERR_BADTYPE       An attempt was made to create an object of a
                         type not supported by the server.

   NFS4ERR_JUKEBOX       The server initiated the request, but was not
                         able to complete it in a timely fashion. The
                         client should wait and then try the request
                         with a new RPC transaction ID.  For example,
                         this error should be returned from a server
                         that supports hierarchical storage and receives
                         a request to process a file that has been
                         migrated. In this case, the server should start
                         the immigration process and respond to client
                         with this error.

   NFS4ERR_SAME          Returned if an NVERIFY operation shows that no
                         attributes have changed.

   NFS4ERR_DENIED        An attempt to lock a file is denied.  Since
                         this may be a temporary condition, the client
                         is encouraged to retry the lock request (with
                         exponential backoff of timeout) until the lock

Expires: March 2000                                            [Page 70]


Draft Protocol Specification  NFS version 4               September 1999

                         is accepted.

   NFS4ERR_EXPIRED       A lease has expired that is being used in the
                         current procedure.

   NFS4ERR_LOCKED        A read or write operation was attempted on a
                         locked file.

   NFS4ERR_GRACE         The server is in its recovery or grace period
                         which should match the lease period of the
                         server.

   NFS4ERR_FHEXPIRED     The file handle provided is volatile and has
                         expired at the server.  The client should
                         attempt to recover the new file handle by
                         traversing the server's file system name space.
                         The file handle may have expired because the
                         server has restarted, the file system object
                         has been removed, or the file handle has been
                         flushed from the server's internal mappings.

        NOTE: This error definition will need to be crisp and match
        the section describing the volatile file handles.

   NFS4ERR_SHARE_DENIED  An attempt to OPEN a file with a share
                         reservation has failed because of a share
                         conflict.

   NFS4ERR_SAME          This error is returned by the NVERIFY operation
                         to signify that the attributes compared were
                         the same as provided in the client's request.

   NFS4ERR_WRONGSEC      The security mechanism being used by the client
                         for the procedure does not match the server's
                         security policy.  The client should change the
                         security mechanism being used and retry the
                         operation.

   NFS4ERR_CLID_INUSE    The SETCLIENTID procedure has found that a

Expires: March 2000                                            [Page 71]


Draft Protocol Specification  NFS version 4               September 1999

                         client id is already in use by another client.

   NFS4ERR_RESOURCE      For the processing of the COMPOUND procedure,
                         the server may exhaust available resources and
                         can not continue processing procedures within
                         the COMPOUND operation.  This error will be
                         returned from the server in those instances of
                         resource exhaustion related to the processing
                         of the COMPOUND procedure.

   NFS4ERR_MOVED         The filesystem which contains the current
                         filehandle object has been relocated or
                         migrated to another server.  The client may
                         obtain the new filesystem location by obtaining
                         the "fs_locations" attribute for the current
                         filehandle.  For further discussion, refer to
                         the section "Filesystem Migration or
                         Relocation".

   NFS4ERR_NOFILEHANDLE  The logical current file handle value has not
                         been set properly.  This may be a result of a
                         malformed COMPOUND operation (i.e. no PUTFH or
                         PUTROOTFH before an operation that requires the
                         current file handle be set).

Expires: March 2000                                            [Page 72]


Draft Protocol Specification  NFS version 4               September 1999

11.  NFS Version 4 Requests

   For the NFS program, version 4, there are two traditional RPC
   procedures: NULL and COMPOUND.  All other operations for NFS version
   4 are defined in normal XDR/RPC syntax and semantics except that
   these operations are encapsulated within the COMPOUND request.  This
   requires that the client combine one or more NFSv4 operations into a
   single request.

   The NFS4_CALLBACK program is used to provide server to client
   signaling and is constructed in a similar fashion as the NFS program.
   The procedures CB_NULL and CB_COMPOUND are defined in the same way as
   NULL and COMPOUND are within the NFS program.  The CB_COMPOUND
   request also encapsulates the remaining operations of the
   NFS4_CALLBACK program.

11.1.  Compound Procedure

   These compound requests provide the opportunity for better
   performance on high latency networks.  The client can avoid
   cumulative latency of multiple RPCs by combining multiple dependent
   operations into a single compound request.  A compound op may provide
   for protocol simplification by allowing the client to combine basic
   procedures into a single request that is customized for the client's
   environment.

   The basics of the COMPOUND procedures construction is:

                  +-----------+-----------+-----------+--
                  | op + args | op + args | op + args |
                  +-----------+-----------+-----------+--

   and the reply looks like this:

          +----------------+----------------+----------------+--
          | code + results | code + results | code + results |
          +----------------+----------------+----------------+--

   Where "code" is an indication of the success or failure of the
   operation including the opcode itself.

11.2.  Evaluation of a Compound Request

   The server will process the COMPOUND procedure by evaluating each of
   the operations within the COMPOUND request in order.  Each component

Expires: March 2000                                            [Page 73]


Draft Protocol Specification  NFS version 4               September 1999

   operation consists of a 32 bit operation code, followed by the
   argument of length determined by the type of operation. The results
   of each operation are encoded in sequence into a reply buffer.  The
   results of each operation are preceded by the opcode and a status
   code (normally zero).  If an operation results in a non-zero status
   code, the status will be encoded and evaluation of the compound
   sequence will halt and the reply will be returned.

   There are no atomicity requirements for the procedures contained
   within the COMPOUND procedure.  The operations being evaluated as
   part of a COMPOUND request may be evaluated simultaneously with other
   COMPOUND requests that the server receives.

   It is the client's responsibility for recovering from any partially
   completed compound request.

   Each operation assumes a "current" filehandle that is available as
   part of the execution context of the compound request.  Operations
   may set, change, or return this filehandle.

Expires: March 2000                                            [Page 74]


Draft Protocol Specification  NFS version 4               September 1999

12.  NFS Version 4 Procedures

12.1.  Procedure 0: NULL - No Operation

   SYNOPSIS

     <null>

   ARGUMENT

     void;

   RESULT

     void;

   DESCRIPTION

     Standard ONCRPC NULL procedure.  Void argument, void response.

   ERRORS

     None.

Expires: March 2000                                            [Page 75]


Draft Protocol Specification  NFS version 4               September 1999

12.2.  Procedure 1: COMPOUND - Compound Operations

   SYNOPSIS

     compoundargs -> compoundres

   ARGUMENT

     union opunion switch (unsigned opcode) {
             case <OPCODE>: <argument>;
             ...
     };

     struct op {
             opunion         ops;
     };

     struct COMPOUND4args {
             utf8string      tag;
             op              oplist<>;
     };

   RESULT

     struct COMPOUND4res {
             nfsstat4 status;
             utf8string      tag;
             resultdata      data<>;
     };

   DESCRIPTION

     The COMPOUND procedure is used to combine one or more of the NFS
     procedures into a single RPC request.  The main NFS RPC program has
     two main procedures: NULL and COMPOUND.  All other procedures use
     the COMPOUND procedure as a wrapper.

     In the processing of the COMPOUND procedure, the server may find
     that it does not have the available resources to execute any or all
     of the procedures within the COMPOUND sequence.  In this case, the
     error NFS4ERR_RESOURCE will be returned for the particular
     procedure within the COMPOUND operation where the resource
     exhaustion occurred.  This assume that all previous procedures

Expires: March 2000                                            [Page 76]


Draft Protocol Specification  NFS version 4               September 1999

     within the COMPOUND sequence have been evaluated successfully.

   IMPLEMENTATION

     The COMPOUND procedure is used to combine individual procedures
     into a single RPC request.  The server interprets each of the
     procedures in turn.  If a procedure is executed by the server and
     the status of that procedure is NFS4_OK, then the next procedure in
     the COMPOUND procedure is executed.  The server continues this
     process until there are no more procedures to be executed or one of
     the procedures has a status value other than NFS4_OK.

     Note that the definition of the "tag" in both the request and
     response are left to the implementor.  It may be used to summarize
     the content of the compound request for the benefit of packet
     sniffers and engineers debugging implementations.

   ERRORS

     NFS4ERR_RESOURCE

Expires: March 2000                                            [Page 77]


Draft Protocol Specification  NFS version 4               September 1999

12.2.1.  Operation 2: ACCESS - Check Access Rights

   SYNOPSIS

     (cfh), accessreq -> supported, accessrights

   ARGUMENT

     const ACCESS4_READ      = 0x0001;
     const ACCESS4_LOOKUP    = 0x0002;
     const ACCESS4_MODIFY    = 0x0004;
     const ACCESS4_EXTEND    = 0x0008;
     const ACCESS4_DELETE    = 0x0010;
     const ACCESS4_EXECUTE   = 0x0020;

     struct ACCESS4args {
             /* CURRENT_FH: object */
             uint32_t        access;
     };

   RESULT

     struct ACCESS4resok {
             uint32_t        supported;
             uint32_t        access;
     };

     union ACCESS4res switch (nfsstat4 status) {
      case NFS4_OK:
              ACCESS4resok   resok;
      default:
              void;
     };

   DESCRIPTION

     ACCESS determines the access rights that a user, as identified by
     the credentials in the request, has with respect to a file system
     object. The client encodes the set of access rights that are to be
     checked in a bit mask.  The server checks the permissions encoded
     in the bit mask.  If a status of NFS4_OK is returned, two bit masks

Expires: March 2000                                            [Page 78]


Draft Protocol Specification  NFS version 4               September 1999

     are included in the response.  The first represents the access
     rights for which the server can verify reliably for the user.  The
     second represents the access rights available to the user for the
     filehandle provided.

     The results of this procedure are necessarily advisory in nature.
     That is, a return status of NFS4_OK and the appropriate bit set in
     the bit mask does not imply that such access will be allowed to the
     file system object in the future, as access rights can be revoked
     by the server at any time.

     The following access permissions may be requested:

          ACCESS_READ:   bit 1   Read data from file or read
                                 a directory.
        ACCESS_LOOKUP:   bit 2   Look up a name in a
                                 directory (no meaning for
                                 non-directory objects).
        ACCESS_MODIFY:   bit 3   Rewrite existing file data or modify
                                 existing directory entries.
        ACCESS_EXTEND:   bit 4   Write new data or add
                                 directory entries.
        ACCESS_DELETE:   bit 5   Delete an existing
                                 directory entry.
       ACCESS_EXECUTE:   bit 6   Execute file (no meaning
                                 for a directory).

   IMPLEMENTATION

     In general, it is not sufficient for the client to attempt to
     deduce access permissions by inspecting the uid, gid, and mode
     fields in the file attributes, since the server may perform uid or
     gid mapping or enforce additional access control restrictions. It
     is also possible that the NFS version 4 protocol server may not be
     in the same ID space as the NFS version 4 protocol client. In these
     cases (and perhaps others), the NFS version 4 protocol client can
     not reliably perform an access check with only current file
     attributes.

     In the NFS version 2 protocol, the only reliable way to determine
     whether an operation was allowed was to try it and see if it
     succeeded or failed. Using the ACCESS procedure in the NFS version
     4 protocol, the client can ask the server to indicate whether or

Expires: March 2000                                            [Page 79]


Draft Protocol Specification  NFS version 4               September 1999

     not one or more classes of operations are permitted.  The ACCESS
     operation is provided to allow clients to check before doing a
     series of operations. This is useful in operating systems (such as
     UNIX) where permission checking is done only when a directory is
     opened. This procedure is also invoked by NFS client access
     procedure (called possibly through access(2)). The intent is to
     make the behavior of opening a remote file more consistent with the
     behavior of opening a local file.

     For NFS version 4, the use of the ACCESS procedure when opening a
     regular file is deprecated in favor of using OPEN.

     The information returned by the server in response to an ACCESS
     call is not permanent. It was correct at the exact time that the
     server performed the checks, but not necessarily afterwards. The
     server can revoke access permission at any time.

     The NFS version 4 protocol client should use the effective
     credentials of the user to build the authentication information in
     the ACCESS request used to determine access rights. It is the
     effective user and group credentials that are used in subsequent
     read and write operations.

     Many implementations do not directly support the ACCESS_DELETE
     permission. Operating systems like UNIX will ignore the
     ACCESS_DELETE bit if set on an access request on a non-directory
     object. In these systems, delete permission on a file is determined
     by the access permissions on the directory in which the file
     resides, instead of being determined by the permissions of the file
     itself.  Therefore the mask returned enumerating which access
     rights can be determined will have the ACCESS_DELETE value set to
     0.  This indicates to the client that the server was unable to
     check that particular access right.  The ACCESS_DELETE bit in the
     access mask returned will then be ignored by the client.

   ERRORS

     NFS4ERR_IO

     NFS4ERR_ACCES

     NFS4ERR_SERVERFAULT

     NFS4ERR_STALE

     NFS4ERR_BADHANDLE

Expires: March 2000                                            [Page 80]


Draft Protocol Specification  NFS version 4               September 1999

     NFS4ERR_FHEXPIRED

     NFS4ERR_WRONGSEC

     NFS4ERR_MOVED

Expires: March 2000                                            [Page 81]


Draft Protocol Specification  NFS version 4               September 1999

12.2.2.  Operation 3: CLOSE - Close File

   SYNOPSIS

     (cfh), stateid -> stateid

   ARGUMENT

     struct CLOSE4args {
             stateid4        stateid;
     };

   RESULT

     union CLOSE4res switch (nfsstat4 status) {
      case NFS4_OK:
             stateid4        stateid;
      default:
             void;
     };

   DESCRIPTION

     The CLOSE procedure notifies the server that all share reservations
     corresponding to the client supplied stateid should be released.

   IMPLEMENTATION

     Share reservations for the matching stateid will be released on
     successful completion of the CLOSE procedure.

   ERRORS

     NFS4ERR_INVAL

     NFS4ERR_STALE

     NFS4ERR_BADHANDLE

Expires: March 2000                                            [Page 82]


Draft Protocol Specification  NFS version 4               September 1999

     NFS4ERR_SERVERFAULT

     NFS4ERR_EXPIRED

     NFS4ERR_GRACE

     NFS4ERR_FHEXPIRED

     NFS4ERR_MOVED

Expires: March 2000                                            [Page 83]


Draft Protocol Specification  NFS version 4               September 1999

12.2.3.  Operation 4: COMMIT - Commit Cached Data

   SYNOPSIS

     (cfh), offset, count -> verifier

   ARGUMENT

     struct COMMIT4args {
             /* CURRENT_FH: file */
             offset4         offset;
             count4          count;
     };

   RESULT

     struct COMMIT4resok {
             writeverf4      verf;
     };

     union COMMIT4res switch (nfsstat4 status) {
      case NFS4_OK:
              COMMIT4resok   resok4;
      default:
              void;
     };

   DESCRIPTION

     The COMMIT procedure forces or flushes data to stable storage that
     was previously written with a WRITE operation which had the stable
     field set to UNSTABLE4.

     The offset provided by the client represents the position within
     the file at which the flush is to begin.  An offset value of 0
     (zero) means to flush data starting at the beginning of the file.
     The count as provided by the client is the number of bytes of data
     to flush. If count is 0 (zero), a flush from offset to the end of
     file is done.

     The server returns a write verifier upon successful completion of
     the COMMIT.  The write verifier is used by the client to determine
     if the server has restarted or rebooted between the initial

Expires: March 2000                                            [Page 84]


Draft Protocol Specification  NFS version 4               September 1999

     WRITE(s) and the COMMIT.  The client does this by comparing the
     write verifier returned from the initial writes and the verifier
     returned by the COMMIT procedure.  The server must vary the value
     of the write verifier at each server event that may lead to a loss
     of uncommitted data.  Most commonly this occurs when the server is
     rebooted; however, other events at the server may result in
     uncommitted data loss as well.

   IMPLEMENTATION

     The COMMIT procedure is similar in operation and semantics to the
     POSIX fsync(2) system call that synchronizes a file's state with
     the disk (file data and metadata is flushed to disk or stable
     storage). COMMIT performs the same operation for a client, flushing
     any unsynchronized data and metadata on the server to the server's
     disk or stable storage for the specified file.  Like fsync(2), it
     may be that there is some modified data or no modified data to
     synchronize. The data may have been synchronized by the server's
     normal periodic buffer synchronization activity. COMMIT should
     return NFS4_OK, unless there has been an unexpected error.

     COMMIT differs from fsync(2) in that it is possible for the client
     to flush a range of the file (most likely triggered by a buffer-
     reclamation scheme on the client before file has been completely
     written).

     The server implementation of COMMIT is reasonably simple.  If the
     server receives a full file COMMIT request, that is starting at
     offset 0 and count 0, it should do the equivalent of fsync()'ing
     the file. Otherwise, it should arrange to have the cached data in
     the range specified by offset and count to be flushed to stable
     storage.  In both cases, any metadata associated with the file must
     be flushed to stable storage before returning. It is not an error
     for there to be nothing to flush on the server.  This means that
     the data and metadata that needed to be flushed have already been
     flushed or lost during the last server failure.

     The client implementation of COMMIT is a little more complex.
     There are two reasons for wanting to commit a client buffer to
     stable storage. The first is that the client wants to reuse a
     buffer. In this case, the offset and count of the buffer are sent
     to the server in the COMMIT request. The server then flushes any
     cached data based on the offset and count, and flushes any metadata
     associated with the file. It then returns the status of the flush
     and the write verifier.  The other reason for the client to
     generate a COMMIT is for a full file flush, such as may be done at

Expires: March 2000                                            [Page 85]


Draft Protocol Specification  NFS version 4               September 1999

     close.  In this case, the client would gather all of the buffers
     for this file that contain uncommitted data, do the COMMIT
     operation with an offset of 0 and count of 0, and then free all of
     those buffers.  Any other dirty buffers would be sent to the server
     in the normal fashion.

     After a buffer is written by the client with stable parameter set
     to UNSTABLE, the buffer must be considered as modified by the
     client until the buffer has either been flushed via a COMMIT
     operation or written via a WRITE operation with stable parameter
     set to FILE_SYNC or DATA_SYNC. This is done to prevent the buffer
     from being freed and reused before the data can be flushed to
     stable storage on the server.

     When a response comes back from either a WRITE or a COMMIT
     operation and it contains a write verifier that is different than
     previously returned by the server, the client will need to
     retransmit all of the buffers containing uncommitted cached data to
     the server.  How this is to be done is up to the implementor.  If
     there is only one buffer of interest, then it should probably be
     sent back over in a WRITE request with the appropriate stable
     parameter. If there is more than one buffer, it might be worthwhile
     retransmitting all of the buffers in WRITE requests with the stable
     parameter set to UNSTABLE and then retransmitting the COMMIT
     operation to flush all of the data on the server to stable storage.
     The timing of these retransmissions is left to the implementor.

     The above description applies to page-cache-based systems as well
     as buffer-cache-based systems. In those systems, the virtual memory
     system will need to be modified instead of the buffer cache.

   ERRORS

     NFS4ERR_IO

     NFS4ERR_LOCKED

     NFS4ERR_SERVERFAULT

     NFS4ERR_MOVED

Expires: March 2000                                            [Page 86]


Draft Protocol Specification  NFS version 4               September 1999

12.2.4.  Operation 5: CREATE - Create a Non-Regular File Object

   SYNOPSIS

     (cfh), name, type, how -> (cfh), change_info

   ARGUMENT

     struct CREATE4args {
             /* CURRENT_FH: directory for creation */
             component4      objname;
             fattr4_type     type;
             createhow4      createhow;
     };

   RESULT

     struct change_info4 {
             bool            atomic;
             fattr4_change   before;
             fattr4_change   after;
     };

     struct CREATE4resok {
             change_info4     cinfo;
     };

     union CREATE4res switch (nfsstat4 status) {
      case NFS4_OK:
              CREATE4resok resok4;
      default:
              void;
     };

   DESCRIPTION

     The CREATE procedure creates an non-regular file object in a
     directory with a given name.  The OPEN procedure MUST be used to
     create a regular file.

        The need for exclusive create semantics for non-regular

Expires: March 2000                                            [Page 87]


Draft Protocol Specification  NFS version 4               September 1999

        files needs to be decided upon and decisions about storage
        location of the verifier will need to be determined as
        well.

   The objtype determines the type of object to be created: directory,
   symlink, etc.  The how union may have a value of UNCHECKED, GUARDED,
   and EXCLUSIVE. UNCHECKED means that the object should be created
   without checking for the existence of a duplicate object in the same
   directory. In this case, attrbits and attrvals describe the initial
   attributes for the file object. GUARDED specifies that the server
   should check for the presence of a duplicate object before performing
   the create and should fail the request with NFS4ERR_EXIST if a
   duplicate object exists. If the object does not exist, the request is
   performed as described for UNCHECKED.  EXCLUSIVE specifies that the
   server is to follow exclusive creation semantics, using the verifier
   to ensure exclusive creation of the target. No attributes may be
   provided in this case, since the server may use the target object
   meta-data to store the verifier.

   For the directory where the new file object was created, the server
   returns change_info4 information in cinfo.  With the atomic field of
   the change_info4 struct, the server will indicate if the before and
   after change attributes were obtained atomically with respect to the
   file object creation.

   The current filehandle is replaced by that of the new object.

   IMPLEMENTATION

     The CREATE procedure carries support for EXCLUSIVE create forward
     from NFS version 3.  As in NFS version 3, this mechanism provides
     reliable exclusive creation.  Exclusive create is invoked when the
     how parameter is EXCLUSIVE.  In this case, the client provides a
     verifier that can reasonably be expected to be unique.  A
     combination of a client identifier, perhaps the client network
     address, and a unique number generated by the client, perhaps the
     RPC transaction identifier, may be appropriate.

     If the object does not exist, the server creates the object and
     stores the verifier in stable storage. For file systems that do not
     provide a mechanism for the storage of arbitrary file attributes,
     the server may use one or more elements of the object meta-data to
     store the verifier. The verifier must be stored in stable storage
     to prevent erroneous failure on retransmission of the request. It
     is assumed that an exclusive create is being performed because
     exclusive semantics are critical to the application. Because of the

Expires: March 2000                                            [Page 88]


Draft Protocol Specification  NFS version 4               September 1999

     expected usage, exclusive CREATE does not rely solely on the
     normally volatile duplicate request cache for storage of the
     verifier. The duplicate request cache in volatile storage does not
     survive a crash and may actually flush on a long network partition,
     opening failure windows.  In the UNIX local file system
     environment, the expected storage location for the verifier on
     creation is the meta-data (time stamps) of the object. For this
     reason, an exclusive object create may not include initial
     attributes because the server would have nowhere to store the
     verifier.

     If the server can not support these exclusive create semantics,
     possibly because of the requirement to commit the verifier to
     stable storage, it should fail the CREATE request with the error,
     NFS4ERR_NOTSUPP.

     During an exclusive CREATE request, if the object already exists,
     the server reconstructs the object's verifier and compares it with
     the verifier in the request. If they match, the server treats the
     request as a success. The request is presumed to be a duplicate of
     an earlier, successful request for which the reply was lost and
     that the server duplicate request cache mechanism did not detect.
     If the verifiers do not match, the request is rejected with the
     status, NFS4ERR_EXIST.

     Once the client has performed a successful exclusive create, it
     must issue a SETATTR to set the correct object attributes.  Until
     it does so, it should not rely upon any of the object attributes,
     since the server implementation may need to overload object meta-
     data to store the verifier.

     Use of the GUARDED attribute does not provide exactly-once
     semantics.  In particular, if a reply is lost and the server does
     not detect the retransmission of the request, the procedure can
     fail with NFS4ERR_EXIST, even though the create was performed
     successfully.

        Note:

        1. Need to determine an initial set of attributes
           that must be set, and a set of attributes that
           can optionally be set, on a per-filetype basis.
           For instance, if the filetype is a NF4BLK then
           the device attributes must be set.

        2. Need to consider the symbolic link path as
           an "attribute".  No need for a READLINK op

Expires: March 2000                                            [Page 89]


Draft Protocol Specification  NFS version 4               September 1999

           if this is so. Similarly, a filehandle could
           be defined as an attribute for LINK.

   ERRORS

     NFS4ERR_IO

     NFS4ERR_ACCES

     NFS4ERR_EXIST

     NFS4ERR_NOTDIR

     NFS4ERR_INVAL

     NFS4ERR_NOSPC

     NFS4ERR_ROFS

     NFS4ERR_NAMETOOLONG

     NFS4ERR_DQUOT

     NFS4ERR_NOTSUPP

     NFS4ERR_SERVERFAULT

     NFS4ERR_FHEXPIRED

     NFS4ERR_WRONGSEC

     NFS4ERR_MOVED

Expires: March 2000                                            [Page 90]


Draft Protocol Specification  NFS version 4               September 1999

12.2.5.  Operation 6: DELEGPURGE - Purge Delegations Awaiting Recovery

   SYNOPSIS

     clientid ->

   ARGUMENT

     struct DELEGPURGE4args {
             clientid4       clientid;
     };

   RESULT

     struct DELEGPURGE4res {
             nfsstat4        status;
     };

   DESCRIPTION

     Purges all of the delegations awaiting recovery for a given client.
     This is useful for clients which do not commit delegation
     information to stable storage to indicate that conflicting requests
     need not be held up awaiting recovery of delegation information.

     This operation should also be used by clients which do have
     delegation information on stable storage after doing all of
     delegation recovery that is needed.  Using DELEGPURGE will prevent
     any delegations which were made by the server but were not sent to
     the client and committed to stable storage from holding up other
     clients making conflicting requests.

   ERRORS

     <TBD>

Expires: March 2000                                            [Page 91]


Draft Protocol Specification  NFS version 4               September 1999

12.2.6.  Operation 7: DELEGRETURN - Return Delegation

   SYNOPSIS

     stateid ->

   ARGUMENT

     struct DELEGRETURN4args {
             stateid4        stateid;
     };

   RESULT

     struct DELEGRETURN4res {
             nfsstat4        status;
     };

   DESCRIPTION

     Returns the delegation represented by the given stateid

   ERRORS

     <TBD>

Expires: March 2000                                            [Page 92]


Draft Protocol Specification  NFS version 4               September 1999

12.2.7.  Operation 8: GETATTR - Get Attributes

   SYNOPSIS

     (cfh), attrbits -> attrbits, attrvals

   ARGUMENT

     struct GETATTR4args {
             /* CURRENT_FH: directory or file */
             bitmap4         attr_request;
     };

   RESULT

     struct GETATTR4resok {
             fattr4          obj_attributes;
     };

     union GETATTR4res switch (nfsstat4 status) {
      case NFS4_OK:
              GETATTR4resok  resok4;
      default:
              void;
     };

   DESCRIPTION

     The GETATTR procedure will obtain attributes from the server.  The
     client sets a bit in the bitmap argument for each attribute value
     that it would like the server to return.  The server returns an
     attribute bitmap that indicates the attribute values for which it
     was able to return, followed by the attribute values ordered lowest
     attribute number first.

     The server must return a value for each attribute that the client
     requests if the attribute is supported by the server.  If the
     server does not support an attribute or cannot approximate a useful
     value then it must not return the attribute value and must not set
     the attribute bit in the result bitmap.  The server must return an
     error if it supports an attribute but cannot obtain its value.  In
     that case no attribute values will be returned.

Expires: March 2000                                            [Page 93]


Draft Protocol Specification  NFS version 4               September 1999

     All servers must support attribute 0 (zero) which is a bitmap of
     all supported attributes for the filesystem object.

   IMPLEMENTATION

   ERRORS

     NFS4ERR_IO

     NFS4ERR_ACCES

     NFS4ERR_INVAL

     NFS4ERR_STALE

     NFS4ERR_BADHANDLE

     NFS4ERR_SERVERFAULT

     NFS4ERR_JUKEBOX

     NFS4ERR_FHEXPIRED

     NFS4ERR_MOVED

Expires: March 2000                                            [Page 94]


Draft Protocol Specification  NFS version 4               September 1999

12.2.8.  Operation 9: GETFH - Get Current Filehandle

   SYNOPSIS

     (cfh) -> filehandle

   ARGUMENT

     /* CURRENT_FH: */
     void;

   RESULT

     struct GETFH4resok {
             nfs4_fh         object;
     };

     union GETFH4res switch (nfsstat4 status) {
      case NFS4_OK:
              GETFH4resok    resok4;
      default:
              void;
     };

   DESCRIPTION

     Returns the current filehandle.  Operations that change the current
     filehandle like LOOKUP or CREATE to not automatically return the
     new filehandle as a result.  For instance, if a client needs to
     lookup a directory entry and obtain its filehandle then the
     following request is needed.

             1: PUTFH  (directory filehandle)
             2: LOOKUP (entry name)
             3: GETFH

   IMPLEMENTATION

Expires: March 2000                                            [Page 95]


Draft Protocol Specification  NFS version 4               September 1999

   ERRORS

     NFS4ERR_BADHANDLE

     NFS4ERR_FHEXPIRED

     NFS4ERR_MOVED

     NFS4ERR_NOFILEHANDLE

     NFS4ERR_SERVERFAULT

     NFS4ERR_STALE

     NFS4ERR_WRONGSEC

Expires: March 2000                                            [Page 96]


Draft Protocol Specification  NFS version 4               September 1999

12.2.9.  Operation 10: LINK - Create Link to a File

   SYNOPSIS

     (cfh), directory, newname -> (cfh), change_info

   ARGUMENT

     struct LINK4args {
             /* CURRENT_FH: file */
             nfs4_fh         dir;
             component4      newname;
     };

   RESULT

     struct LINK4resok {
             change_info4    cinfo;
     };

     union LINK4res switch (nfsstat4 status) {
      case NFS4_OK:
              LINK4resok resok4;
      default:
              void;
     };

   DESCRIPTION

     The LINK procedure creates an additional newname for the file with
     the current filehandle in the directory dir.  The current file
     handle and the directory must reside within the same file system on
     the server.

     For the directory, the server returns change_info4 information in
     cinfo.  With the atomic field of the change_info4 struct, the
     server will indicate if the before and after change attributes were
     obtained atomically with respect to the link creation.

   IMPLEMENTATION

Expires: March 2000                                            [Page 97]


Draft Protocol Specification  NFS version 4               September 1999

     Changes to any property of the hard-linked files are reflected in
     all of the linked files.  When a hard link is made to a file, the
     attributes for the file should have a value for nlink that is one
     greater than the value before the LINK.

     The comments under RENAME regarding object and target residing on
     the same file system apply here as well. The comments regarding the
     target name applies as well.

   ERRORS

     NFS4ERR_IO

     NFS4ERR_ACCES

     NFS4ERR_EXIST

     NFS4ERR_XDEV

     NFS4ERR_NOTDIR

     NFS4ERR_INVAL

     NFS4ERR_NOSPC

     NFS4ERR_ROFS

     NFS4ERR_MLINK

     NFS4ERR_NAMETOOLONG

     NFS4ERR_DQUOT

     NFS4ERR_STALE

     NFS4ERR_BADHANDLE

     NFS4ERR_NOTSUPP

     NFS4ERR_SERVERFAULT

     NFS4ERR_FHEXPIRED

     NFS4ERR_MOVED

Expires: March 2000                                            [Page 98]


Draft Protocol Specification  NFS version 4               September 1999

12.2.10.  Operation 11: LOCK - Create Lock

   SYNOPSIS

     (cfh) type, seqid, reclaim, owner, offset, length -> stateid,
     access

   ARGUMENT

     enum nfs4_lock_type {
             READ_LT         = 1,
             WRITE_LT        = 2,
             READW_LT        = 3,    /* blocking read */
             WRITEW_LT       = 4     /* blocking write */
     };

     struct LOCK4args {
             /* CURRENT_FH: file */
             nfs4_lock_type  type;
             seqid4          seqid;
             bool            reclaim;
             stateid4        stateid;
             offset4         offset;
             length4         length;
     };

   RESULT

     struct lockres {
             stateid4        stateid;
             int32_t         access;
     };

     union LOCK4res switch (nfsstat4 status) {
      case NFS4_OK:
              lockres        result;
      default:
              void;
     };

   DESCRIPTION

Expires: March 2000                                            [Page 99]


Draft Protocol Specification  NFS version 4               September 1999

     The LOCK procedure requests a record lock for the byte range
     specified by the offset and length parameters.  The lock type is
     also specified to be one of the nfs4_lock_types.  If this is a
     reclaim request, the reclaim parameter will be TRUE;

   IMPLEMENTATION

     The File Locking section contains a full description of this and
     the other file locking procedures.

   ERRORS

     NFS4ERR_ACCES

     NFS4ERR_ISDIR

     NFS4ERR_INVAL

     NFS4ERR_STALE

     NFS4ERR_BADHANDLE

     NFS4ERR_SERVERFAULT

     NFS4ERR_GRACE

     NFS4ERR_FHEXPIRED

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 100]


Draft Protocol Specification  NFS version 4               September 1999

12.2.11.  Operation 12: LOCKT - Test For Lock

   SYNOPSIS

     (cfh) type, seqid, reclaim, owner, offset, length -> {void,
     NFS4ERR_DENIED -> owner}

   ARGUMENT

     struct LOCK4args {
             /* CURRENT_FH: file */
             nfs4_lock_type  type;
             seqid4          seqid;
             bool            reclaim;
             nfs_lockowner   owner;
             offset4         offset;
             length4         length;
     };

   RESULT

     union LOCKT4res switch (nfsstat4 status) {
      case NFS4ERR_DENIED:
              nfs_lockowner  owner;
      case NFS4_OK:
              void;
      default:
              void;
     };

   DESCRIPTION

     The LOCKT procedure tests the lock as specified in the argument.
     The owner of the lock is returned in the event it is currently
     being held; if no lock is held, nothing other than NFS4_OK is
     returned.

   IMPLEMENTATION

     The File Locking section contains a full description of this and
     the other file locking procedures.

Expires: March 2000                                           [Page 101]


Draft Protocol Specification  NFS version 4               September 1999

   ERRORS

     NFS4ERR_ACCES

     NFS4ERR_ISDIR

     NFS4ERR_INVAL

     NFS4ERR_STALE

     NFS4ERR_BADHANDLE

     NFS4ERR_SERVERFAULT

     NFS4ERR_DENIED

     NFS4ERR_GRACE

     NFS4ERR_FHEXPIRED

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 102]


Draft Protocol Specification  NFS version 4               September 1999

12.2.12.  Operation 13: LOCKU - Unlock File

   SYNOPSIS

     (cfh) type, seqid, reclaim, owner, offset, length -> stateid

   ARGUMENT

     struct LOCK4args {
             /* CURRENT_FH: file */
             nfs4_lock_type  type;
             seqid4          seqid;
             bool            reclaim;
             nfs_lockowner   owner;
             offset4         offset;
             length4         length;
     };

   RESULT

     union LOCKU4res switch (nfsstat4 status) {
      case   NFS4_OK:
              stateid4       stateid_ok;
      default:
              stateid4       stateid_oth;
     };

   DESCRIPTION

     The LOCKU procedure unlocks the record lock specified by the
     parameters.

   IMPLEMENTATION

     The File Locking section contains a full description of this and
     the other file locking procedures.

   ERRORS

     NFS4ERR_ACCES

Expires: March 2000                                           [Page 103]


Draft Protocol Specification  NFS version 4               September 1999

     NFS4ERR_ISDIR

     NFS4ERR_INVAL

     NFS4ERR_STALE

     NFS4ERR_BADHANDLE

     NFS4ERR_SERVERFAULT

     NFS4ERR_GRACE

     NFS4ERR_FHEXPIRED

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 104]


Draft Protocol Specification  NFS version 4               September 1999

12.2.13.  Operation 14: LOOKUP - Lookup Filename

   SYNOPSIS

     (cfh), filenames -> (cfh)

   ARGUMENT

     struct LOOKUP4args {
             /* CURRENT_FH: directory */
             pathname4       path;
     };

   RESULT

     struct LOOKUP4res {
             /* CURRENT_FH: object */
             nfsstat4        status;
     };

   DESCRIPTION

     The current filehandle is assumed to refer to a directory.  LOOKUP
     evaluates the pathname contained in the array of names and obtains
     a new current filehandle from the final name. All but the final
     name in the list must be the names of directories.

     If the pathname cannot be evaluated either because a component
     doesn't exist or because the client doesn't have permission to
     evaluate a component of the path, then an error will be returned
     and the current filehandle will be unchanged.

   IMPLEMENTATION

     If the client prefers a partial evaluation of the path then a
     sequence of LOOKUP operations can be substituted e.g.

             1. PUTFH  (directory filehandle)
             2. LOOKUP "pub" "foo" "bar"
             3. GETFH

Expires: March 2000                                           [Page 105]


Draft Protocol Specification  NFS version 4               September 1999

     or

             1. PUTFH  (directory filehandle)
             2. LOOKUP "pub"
             3. GETFH
             4. LOOKUP "foo"
             5. GETFH
             6. LOOKUP "bar"
             7. GETFH

     NFS version 4 servers depart from the semantics of previous NFS
     versions in allowing LOOKUP requests to cross mountpoints on the
     server. The client can detect a mountpoint crossing by comparing
     the fsid attribute of the directory with the fsid attribute of the
     directory looked up.  If the fsids are different then the new
     directory is a server mountpoint.  Unix clients that detect a
     mountpoint crossing will need to mount the server's filesystem.

     Servers that limit NFS access to "shares" or "exported" filesystems
     should provide a pseudo-filesystem into which the exported
     filesystems can be integrated, so that clients can browse the
     server's namespace.  The clients view of a pseudo filesystem will
     be limited to paths that lead to exported filesystems.

     Note: previous versions of the protocol assigned special semantics
     to the names "." and "..".  NFS version 4 assigns no special
     semantics to these names.  The LOOKUPP operator must be used to
     lookup a parent directory.

     Note that this procedure does not follow symbolic links.  The
     client is responsible for all parsing of filenames including
     filenames that are modified by symbolic links encountered during
     the lookup process.

   ERRORS

     NFS4ERR_NOENT

     NFS4ERR_IO

     NFS4ERR_ACCES

     NFS4ERR_NOTDIR

     NFS4ERR_INVAL

     NFS4ERR_NAMETOOLONG

Expires: March 2000                                           [Page 106]


Draft Protocol Specification  NFS version 4               September 1999

     NFS4ERR_STALE

     NFS4ERR_SERVERFAULT

     NFS4ERR_FHEXPIRED

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 107]


Draft Protocol Specification  NFS version 4               September 1999

12.2.14.  Operation 15: LOOKUPP - Lookup Parent Directory

   SYNOPSIS

     (cfh) -> (cfh)

   ARGUMENT

     /* CURRENT_FH: object */
     void;

   RESULT

     struct LOOKUPP4res {
             /* CURRENT_FH: directory */
             nfsstat4        status;
     };

   DESCRIPTION

     The current filehandle is assumed to refer to a directory.  LOOKUPP
     assigns the filehandle for its parent directory to be the current
     filehandle.  If there is no parent directory an ENOENT error must
     be returned.  Therefore, ENOENT will be returned by the server when
     the current filehandle is at the root or top of the server's file
     tree.

   IMPLEMENTATION

     As for LOOKUP, LOOKUPP will also cross mountpoints.

   ERRORS

     NFS4ERR_NOENT

     NFS4ERR_IO

     NFS4ERR_ACCES

     NFS4ERR_INVAL

Expires: March 2000                                           [Page 108]


Draft Protocol Specification  NFS version 4               September 1999

     NFS4ERR_STALE

     NFS4ERR_SERVERFAULT

     NFS4ERR_FHEXPIRED

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 109]


Draft Protocol Specification  NFS version 4               September 1999

12.2.15.  Operation 16: NVERIFY - Verify Difference in Attributes

   SYNOPSIS

     (cfh), attrbits, attrvals -> -

   ARGUMENT

     struct NVERIFY4args {
             /* CURRENT_FH: object */
             bitmap4         attr_request;
             fattr4          obj_attributes;
     };

   RESULT

     struct NVERIFY4res {
             nfsstat4        status;
     };

   DESCRIPTION

     This operation is used to prefix a sequence of operations to be
     performed if one or more attributes have changed on some filesystem
     object.  If all the attributes match then the error NFS4ERR_SAME
     must be returned.

   IMPLEMENTATION

     This operation is useful as a cache validation operator.  If the
     object to which the attributes belong has changed then the
     following operations may obtain new data associated with that
     object.  For instance, to check if a file has been changed and
     obtain new data if it has:

             1. PUTFH  (public)
             2. LOOKUP "pub" "foo" "bar"
             3. NVERIFY attrbits attrs
             4. READ 0 32767

Expires: March 2000                                           [Page 110]


Draft Protocol Specification  NFS version 4               September 1999

   ERRORS

     NFS4ERR_IO

     NFS4ERR_ACCES

     NFS4ERR_STALE

     NFS4ERR_BADHANDLE

     NFS4ERR_SERVERFAULT

     NFS4ERR_FHEXPIRED

     NFS4ERR_SAME

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 111]


Draft Protocol Specification  NFS version 4               September 1999

12.2.16.  Operation 17: OPEN - Open a Regular File

   SYNOPSIS

     (cfh), claim, openhow, owner, seqid, access, deny -> (cfh),
     stateid, rflags, access, delegation

   ARGUMENT

     struct OPEN4args {
             open_claim4     claim;
             openflag        openhow;
             nfs_lockowner   owner;
             seqid4          seqid;
             int32_t         access;
             int32_t         deny;
     };

     enum createmode4 {
             UNCHECKED       = 0,
             GUARDED         = 1,
             EXCLUSIVE       = 2
     };

     union createhow4 switch (createmode4 mode) {
             case UNCHECKED:
             case GUARDED:
                     fattr4          createattrs;
             case EXCLUSIVE:
                     createverf4     verf;
     };

     enum opentype4 {
             OPEN4_NOCREATE  0,
             OPEN4_CREATE    1
     };

     union openflag switch (opentype4 opentype) {
      case OPEN4_CREATE:
              createhow4     how;
      default:
              void;
     };

     /*
      * Access and Deny constants for open argument
      */

Expires: March 2000                                           [Page 112]


Draft Protocol Specification  NFS version 4               September 1999

     const OPEN4_ACCESS_READ = 0x0001;
     const OPEN4_ACCESS_WRITE= 0x0002;
     const OPEN4_ACCESS_BOTH = 0x0003;

     const OPEN4_DENY_NONE   = 0x0000;
     const OPEN4_DENY_READ   = 0x0001;
     const OPEN4_DENY_WRITE  = 0x0002;
     const OPEN4_DENY_BOTH   = 0x0003;

     enum open_delegation_type4 {
             OPEN_DELEGATE_NONE      = 0,
             OPEN_DELEGATE_READ      = 1,
             OPEN_DELEGATE_WRITE     = 2
     };

     enum open_claim_type4 {
             CLAIM_NULL              = 0,
             CLAIM_PREVIOUS          = 1,
             CLAIM_DELEGATE_CUR      = 2,
             CLAIM_DELEGATE_PREV     = 3
     };

     struct open_claim_delegate_cur {
             pathname4       file;
             stateid4        delegate_stateid;
     };

     union open_claim4 switch (open_claim_type4 claim) {
      /*
       * No special rights to file. Ordinary OPEN of the specified file.
       */
      case CLAIM_NULL:
              /* CURRENT_FH: directory */
              pathname4      file;

      /*
       * Right to the file established by an open previous to server
       * reboot.  File identified by filehandle obtained at that time
       * rather than by name.
       */
      case CLAIM_PREVIOUS:
              /* CURRENT_FH: file being reclaimed */
              int32_t        delegate_type;

      /*
       * Right to file based on a delegation granted by the server.
       * File is specified by name.
       */

Expires: March 2000                                           [Page 113]


Draft Protocol Specification  NFS version 4               September 1999

      case CLAIM_DELEGATE_CUR:
              /* CURRENT_FH: directory */
              open_claim_delegate_cur        delegate_cur_info;

      /* Right to file based on a delegation granted to a previous boot
       * instance of the client.  File is specified by name.
       */
      case CLAIM_DELEGATE_PREV:
              /* CURRENT_FH: directory */
              pathname4      file_delegate_prev;
     };

   RESULT

     /*
      * Result flags
      */
     /* Mandatory locking is in effect for this file. */
     const OPEN4_RESULT_MLOCK        = 0x0001;

     struct open_read_delegation4 {
             stateid4        stateid;        /* Stateid for delegation*/
             bool            recall;         /* Pre-recalled flag for
                                                delegations obtained
                                                by reclaim
                                                (CLAIM_PREVIOUS) */
             nfsacl4         permissions;    /* Defines users who don't
                                                need an ACCESS call to
                                                open for read */
     };

     struct open_write_delegation4 {
             stateid4        stateid;        /* Stateid for delegation
                                                be flushed to the server
                                                on close. */
             bool            recall;         /* Pre-recalled flag for
                                                delegations obtained
                                                by reclaim
                                                (CLAIM_PREVIOUS) */
             nfs_space_limit4 space_limit;   /* Defines condition that
                                                the client must check to
                                                determine whether the
                                                file needs to be flushed
                                                to the server on close.
                                                */
             nfsacl4         permissions;    /* Defines users who don't

Expires: March 2000                                           [Page 114]


Draft Protocol Specification  NFS version 4               September 1999

                                                need an ACCESS call as
                                                part of a delegated
                                                open. */
     };

     union open_delegation4
     switch (open_delegation_type4 delegation_type) {
             case OPEN_DELEGATE_NONE:
                     void;
             case OPEN_DELEGATE_READ:
                     OPEN4readDelegation read;
             case OPEN_DELEGATE_WRITE:
                     OPEN4writeDelegation write;
     };

     struct OPEN4resok {
             stateid4        stateid;        /* Stateid for open */
             uint32_t        rflags;         /* Result flags */
             int32_t         access;         /* Access granted */
             open_delegation4 delegation;    /* Info on any open
                                                delegation */
     };

     union OPEN4res switch (nfsstat4 status) {
      case NFS4_OK:
             /* CURRENT_FH: opened file */
             OPEN4resok      result;
      default:
             void;
     };

   DESCRIPTION

     The OPEN procedure creates and/or opens a regular file in a
     directory with the provided name.  If the file does not exist at
     the server and creation is desired, specification of the method of
     creation is provided by the openhow parameter.  The client has the
     choice of three creation methods: UNCHECKED, GUARDED, or EXCLUSIVE.

     UNCHECKED means that the file should be created without checking
     for the existence of a duplicate object in the same directory.  For
     this type of create, createattrs specifies the initial set of
     attributes for the file (NOTE: need to define exactly which
     attributes should be set and if the file exists, should the
     attributes be modified if the file exists).  If GUARDED is
     specified, the server checks for the presence of a duplicate object

Expires: March 2000                                           [Page 115]


Draft Protocol Specification  NFS version 4               September 1999

     by name before performing the create.  If a duplicate exists, an
     error of NFS4ERR_EXIST is returned as the status.  If the object
     does not exist, the request is performed as described for
     UNCHECKED.

     EXCLUSIVE specifies that the server is to follow exclusive creation
     semantics, using the verifier to ensure exclusive creation of the
     target.  The server should check for the presence of a duplicate
     object by name.  If the object does not exist, the server creates
     the object and stores the verifier with the object.  If the object
     does exist and the stored verifier matches the client provided
     verifier, the server uses the existing object as the newly created
     object.  If the stored verifier does not match, then an error of
     NFS4ERR_EXIST is returned.  No attributes may be provided in this
     case, since the server may use an attribute of the target object to
     store the verifier.  (NOTE: does a specific attribute need to be
     specified for storage of verifier )

     Upon successful creation, the current filehandle is replaced by
     that of the new object.

     The OPEN procedure provides for DOS SHARE capability with the use
     of the access and deny fields of the OPEN arguments.  The client
     specifies at OPEN the required access and deny modes.  For clients
     that do not directly support SHAREs (i.e. Unix), the expected deny
     value is DENY_NONE.  In the case that there is a existing SHARE
     reservation that conflicts with the OPEN request, the server
     returns the error NFS4ERR_DENIED.  For a complete SHARE request,
     the client must provide values for the owner and seqid fields for
     the OPEN argument.  For additional discussion of SHARE semantics
     see the section on 'Share Reservations'.

     In the case that the client is recovering state from a server
     failure, the reclaim field of the OPEN argument is used to signify
     that the request is meant to reclaim state previously held.

     The "claim" field of the OPEN argument is used to specify the file
     to be opened and the state information which the client claims to
     possess.  There are four basic claim types which cover the various
     situations for an OPEN.  They are as follows:

     CLAIM_NULL
                           For the client, this is a new OPEN
                           request and there is no previous state
                           associate with the file for the client.

Expires: March 2000                                           [Page 116]


Draft Protocol Specification  NFS version 4               September 1999

     CLAIM_PREVIOUS
                           The client is claiming basic OPEN state
                           for a file that was held previous to a
                           server reboot.  Generally used when a
                           server is returning persistent file
                           handles; the client may not have the
                           file name to reclaim the OPEN.

     CLAIM_DELEGATE_CUR
                           The client is claiming a delegation for
                           OPEN as granted by the server.
                           Generally this is done as part of
                           recalling a delegation.

     CLAIM_DELEGATE_PREV
                           The client is claiming a delegation
                           granted to a previous client instance;
                           used after the client reboots.

     For OPEN requests whose claim type is other than CLAIM_PREVIOUS
     (i.e. requests other than those devoted to reclaiming opens after a
     server reboot) that reach the server during its grace or lease
     expiration period, the server returns an error of NFS4ERR_GRACE.

     For any OPEN request, the server may return an open delegation,
     which allows further opens and closes to be handled locally on the
     client as described in the section Open Delegation.  Note that
     delegation is up to the server to decide.  The client should never
     assume that delegation will or will not be granted in a particular
     instance.  It should always be prepared for either case.  A partial
     exception is the reclaim (CLAIM_PREVIOUS) case, in which a
     delegation type is claimed.  In this case, delegation will always
     be granted, although the server may specify an immediate recall in
     the delegation structure.

   IMPLEMENTATION

     The OPEN procedure contains support for EXCLUSIVE create.  The
     mechanism is similar to the support in NFS version 3 [RFC1813].  As
     in NFS version 3, this mechanism provides reliable exclusive
     creation.  Exclusive create is invoked when the how parameter is
     EXCLUSIVE.  In this case, the client provides a verifier that can
     reasonably be expected to be unique.  A combination of a client
     identifier, perhaps the client network address, and a unique number
     generated by the client, perhaps the RPC transaction identifier,
     may be appropriate.

     If the object does not exist, the server creates the object and

Expires: March 2000                                           [Page 117]


Draft Protocol Specification  NFS version 4               September 1999

     stores the verifier in stable storage. For file systems that do not
     provide a mechanism for the storage of arbitrary file attributes,
     the server may use one or more elements of the object meta-data to
     store the verifier. The verifier must be stored in stable storage
     to prevent erroneous failure on retransmission of the request. It
     is assumed that an exclusive create is being performed because
     exclusive semantics are critical to the application. Because of the
     expected usage, exclusive CREATE does not rely solely on the
     normally volatile duplicate request cache for storage of the
     verifier. The duplicate request cache in volatile storage does not
     survive a crash and may actually flush on a long network partition,
     opening failure windows.  In the UNIX local file system
     environment, the expected storage location for the verifier on
     creation is the meta-data (time stamps) of the object. For this
     reason, an exclusive object create may not include initial
     attributes because the server would have nowhere to store the
     verifier.

     If the server can not support these exclusive create semantics,
     possibly because of the requirement to commit the verifier to
     stable storage, it should fail the OPEN request with the error,
     NFS4ERR_NOTSUPP.

     During an exclusive CREATE request, if the object already exists,
     the server reconstructs the object's verifier and compares it with
     the verifier in the request. If they match, the server treats the
     request as a success. The request is presumed to be a duplicate of
     an earlier, successful request for which the reply was lost and
     that the server duplicate request cache mechanism did not detect.
     If the verifiers do not match, the request is rejected with the
     status, NFS4ERR_EXIST.

     Once the client has performed a successful exclusive create, it
     must issue a SETATTR to set the correct object attributes.  Until
     it does so, it should not rely upon any of the object attributes,
     since the server implementation may need to overload object meta-
     data to store the verifier.  The subsequent SETATTR must not occur
     in the same COMPOUND request as the OPEN.  This separation will
     guarantee that the exclusive create mechanism will continue to
     function properly in the face of retransmission of the request.

     Use of the GUARDED attribute does not provide exactly-once
     semantics.  In particular, if a reply is lost and the server does
     not detect the retransmission of the request, the procedure can
     fail with NFS4ERR_EXIST, even though the create was performed
     successfully.

     For SHARE reservations, the client must specify a value for access

Expires: March 2000                                           [Page 118]


Draft Protocol Specification  NFS version 4               September 1999

     that is one of READ, WRITE, or BOTH.  For deny, the client must
     specify one of NONE, READ, WRITE, or BOTH.  If the client fails to
     do this, the server must return NFS4ERR_INVAL.

     The OPEN call

   ERRORS

     NFS4ERR_IO

     NFS4ERR_ACCES

     NFS4ERR_EXIST

     NFS4ERR_NOTDIR

     NFS4ERR_NOSPC

     NFS4ERR_ROFS

     NFS4ERR_NAMETOOLONG

     NFS4ERR_DQUOT

     NFS4ERR_NOTSUPP

     NFS4ERR_SERVERFAULT

     NFS4ERR_SHARE_DENIED

     NFS4ERR_GRACE

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 119]


Draft Protocol Specification  NFS version 4               September 1999

12.2.17.  Operation 18: OPENATTR - Open Named Attribute Directory

   SYNOPSIS

     (cfh) -> (cfh)

   ARGUMENT

     /* CURRENT_FH: file or directory */
     void;

   RESULT

     struct OPENATTR4res {
             /* CURRENT_FH: name attr directory*/
             nfsstat4        status;
     };

   DESCRIPTION

     The OPENATTR procedure is used to obtain the filehandle of the
     named attribute directory associated with the current filehandle.
     The result of the OPENATTR will be a filehandle of type NF4ATTRDIR.
     From this filehandle, READDIR and LOOKUP procedures can be used to
     obtain filehandles for the various named attributes associated with
     the original file system object.  Filehandles returned within the
     named attribute directory will have a type of NF4NAMEDATTR.

   IMPLEMENTATION

     If the server does not support named attributes for the current
     filehandle, an error of NFS4ERR_NOTSUPP will be returned to the
     client.

   ERRORS

     NFS4ERR_NOENT

     NFS4ERR_IO

Expires: March 2000                                           [Page 120]


Draft Protocol Specification  NFS version 4               September 1999

     NFS4ERR_ACCES

     NFS4ERR_INVAL

     NFS4ERR_STALE

     NFS4ERR_BADHANDLE

     NFS4ERR_NOTSUPP

     NFS4ERR_SERVERFAULT

     NFS4ERR_JUKEBOX

     NFS4ERR_FHEXPIRED

     NFS4ERR_WRONGSEC

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 121]


Draft Protocol Specification  NFS version 4               September 1999

12.2.18.  Operation 19: PUTFH - Set Current Filehandle

   SYNOPSIS

     filehandle -> (cfh)

   ARGUMENT

     struct PUTFH4args {
             nfs4_fh         object;
     };

   RESULT

     struct PUTFH4res {
             /* CURRENT_FH: */
             nfsstat4        status;
     };

   DESCRIPTION

     Replaces the current filehandle with the filehandle provided as an
     argument.

   IMPLEMENTATION

     Commonly used as the first operator in any NFS request to set the
     context for following operations.

   ERRORS

     NFS4ERR_BADHANDLE

     NFS4ERR_FHEXPIRED

     NFS4ERR_MOVED

     NFS4ERR_SERVERFAULT

Expires: March 2000                                           [Page 122]


Draft Protocol Specification  NFS version 4               September 1999

     NFS4ERR_STALE

     NFS4ERR_WRONGSEC

Expires: March 2000                                           [Page 123]


Draft Protocol Specification  NFS version 4               September 1999

12.2.19.  Operation 20: PUTPUBFH - Set Public Filehandle

   SYNOPSIS

     - -> (cfh)

   ARGUMENT

     void;

   RESULT

     struct PUTPUBFH4res {
             /* CURRENT_FH: root fh */
             nfsstat4        status;
     };

   DESCRIPTION

     Replaces the current filehandle with the filehandle that represents
     the public filehandle of the server's namespace.  This filehandle
     may be different from the "root" filehandle which may be associated
     with some other directory on the server.

   IMPLEMENTATION

     Used as the first operator in any NFS request to set the context
     for following operations.

   ERRORS

     NFS4ERR_SERVERFAULT NFS4ERR_WRONGSEC

Expires: March 2000                                           [Page 124]


Draft Protocol Specification  NFS version 4               September 1999

12.2.20.  Operation 21: PUTROOTFH - Set Root Filehandle

   SYNOPSIS

     - -> (cfh)

   ARGUMENT

     void;

   RESULT

     struct PUTROOTFH4res {
             /* CURRENT_FH: root fh */
             nfsstat4        status;
     };

   DESCRIPTION

     Replaces the current filehandle with the filehandle that represents
     the root of the server's namespace.  From this filehandle a LOOKUP
     operation can locate any other filehandle on the server. This
     filehandle may be different from the "public" filehandle which may
     be associated with some other directory on the server.

   IMPLEMENTATION

     Commonly used as the first operator in any NFS request to set the
     context for following operations.

   ERRORS

     NFS4ERR_SERVERFAULT

     NFS4ERR_WRONTSEC

Expires: March 2000                                           [Page 125]


Draft Protocol Specification  NFS version 4               September 1999

12.2.21.  Operation 22: READ - Read from File

   SYNOPSIS

     (cfh), offset, count, stateid -> eof, data

   ARGUMENT

     struct READ4args {
             /* CURRENT_FH: file */
             stateid4        stateid;
             offset4         offset;
             count4          count;
     };

   RESULT

     struct READ4resok {
             bool            eof;
             opaque          data<>;
     };

     union READ4res switch (nfsstat4 status) {
      case NFS4_OK:
              READ4resok     resok4;
      default:
              void;
     };

   DESCRIPTION

     The READ procedure reads data from the regular file identified by
     the current filehandle.

     The client provides an offset of where the READ is to start and a
     count of how many bytes are to be read.  An offset of 0 (zero)
     means to read data starting at the beginning of the file. If offset
     is greater than or equal to the size of the file, the status,
     NFS4_OK, is returned with a data length set to 0 (zero) and eof set
     to TRUE.  The READ is subject to access permissions checking.

     If the client specifies a count value of 0 (zero), the READ

Expires: March 2000                                           [Page 126]


Draft Protocol Specification  NFS version 4               September 1999

     succeeds and returns 0 (zero) bytes of data again subject to access
     permissions checking.  The server may choose to return fewer bytes
     than specified by the client.  The client needs to check for this
     condition and handle the condition appropriately.

     The stateid value for a READ request represents a value returned
     from a previous record lock or share reservation request.  Used by
     the server to verify that the associated lock is still valid and to
     update lease timeouts for the client.

     If the read ended at the end-of-file (formally, in a correctly
     formed READ request, if offset + count is equal to the size of the
     file), eof is returned as TRUE; otherwise it is FALSE. A successful
     READ of an empty file will always return eof as TRUE.

   IMPLEMENTATION

     It is possible for the server to return fewer than count bytes of
     data. If the server returns less than the count requested and eof
     set to FALSE, the client should issue another READ to get the
     remaining data. A server may return less data than requested under
     several circumstances. The file may have been truncated by another
     client or perhaps on the server itself, changing the file size from
     what the requesting client believes to be the case. This would
     reduce the actual amount of data available to the client. It is
     possible that the server may back off the transfer size and reduce
     the read request return. Server resource exhaustion may also occur
     necessitating a smaller read return.

     If the file is locked the server will return an NFS4ERR_LOCKED
     error.  Since the lock may be of short duration, the client may
     choose to retransmit the READ request (with exponential backoff)
     until the operation succeeds.

   ERRORS

     NFS4ERR_IO

     NFS4ERR_NXIO

     NFS4ERR_ACCES

     NFS4ERR_INVAL

     NFS4ERR_STALE

Expires: March 2000                                           [Page 127]


Draft Protocol Specification  NFS version 4               September 1999

     NFS4ERR_BADHANDLE

     NFS4ERR_SERVERFAULT

     NFS4ERR_DENIED

     NFS4ERR_JUKEBOX

     NFS4ERR_EXPIRED

     NFS4ERR_LOCKED

     NFS4ERR_GRACE

     NFS4ERR_FHEXPIRED

     NFS4ERR_WRONGSEC

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 128]


Draft Protocol Specification  NFS version 4               September 1999

12.2.22.  Operation 23: READDIR - Read Directory

   SYNOPSIS
      (cfh), cookie, dircount, maxcount, attrbits -> { cookie, filename,
      attrbits, attributes }

   ARGUMENT

     struct READDIR4args {
             /* CURRENT_FH: directory */
             nfs_cookie4     cookie;
             count4          dircount;
             count4          maxcount;
             bitmap4         attr_request;

     };

   RESULT

     struct entry4 {
             nfs_cookie4     cookie;
             component4      name;
             fattr4          attrs;
             entry4          *nextentry;
     };

     struct dirlist4 {
             entry4          *entries;
             bool            eof;
     };

     struct READDIR4resok {
             dirlist4        reply;
     };

     union READDIR4res switch (nfsstat4 status) {
      case NFS4_OK:
              READDIR4resok  resok4;
      default:
              void;
     };

Expires: March 2000                                           [Page 129]


Draft Protocol Specification  NFS version 4               September 1999

   DESCRIPTION

     The READDIR procedure retrieves a variable number of entries from a
     file system directory and returns complete information about each
     entry along with information to allow the client to request
     additional directory entries in a subsequent READDIR.

     The arguments contain a cookie value that represents where the
     READDIR should start within the directory.  A value of 0 (zero) for
     the cookie is used to start reading at the beginning of the
     directory.  For subsequent READDIR requests, the client specifies a
     cookie value that is provided by the server on a previous READDIR
     request.

     The dircount portion of the argument is the maximum number of bytes
     of directory information that should be returned.  This value does
     not include the size of attributes or filehandle values that may be
     returned in the result.

     The maxcount value of the argument specifies the maximum number of
     bytes for the result.  This maximum size represents all of the data
     being returned and includes the XDR overhead.  The server may
     return less data.

     Finally, attrbits represents the list of attributes the client
     wants returned for each directory entry supplied by the server.

     On successful return, the server's response will provide a list of
     directory entries.  Each of these entries contains the name of the
     directory entry, a cookie value for that entry and the associated
     attributes as requested.  The cookie value is only meaningful to
     the server and is used as a "bookmark" for the directory entry.  As
     mentioned, this cookie is used by the client for subsequent READDIR
     operations so that it may continue reading a directory.  The cookie
     is similar in concept to a READ offset but should not be
     interpreted as such by the client.  Ideally, the cookie value
     should not change if the directory is modified.

   IMPLEMENTATION

     Issues that need to be understood for this procedure include
     increased cache flushing activity on the client (as new file
     handles are returned with names which are entered into caches) and
     over-the-wire overhead versus expected subsequent LOOKUP and
     GETATTR elimination.

     The dircount and maxcount fields are included as an optimization.

Expires: March 2000                                           [Page 130]


Draft Protocol Specification  NFS version 4               September 1999

     Consider a READDIR call on a UNIX operating system implementation
     for 1048 bytes; the reply does not contain many entries because of
     the overhead due to attributes and file handles. An alternative is
     to issue a READDIR call for 8192 bytes and then only use the first
     1048 bytes of directory information. However, the server doesn't
     know that all that is needed is 1048 bytes of directory information
     (as would be returned by READDIR). It sees the 8192 byte request
     and issues a VOP_READDIR for 8192 bytes. It then steps through all
     of those directory entries, obtaining attributes and file handles
     for each entry.  When it encodes the result, the server only
     encodes until it gets 8192 bytes of results which include the
     attributes and file handles. Thus, it has done a larger VOP_READDIR
     and many more attribute fetches than it needed to. The ratio of the
     directory entry size to the size of the attributes plus the size of
     the file handle is usually at least 8 to 1. The server has done
     much more work than it needed to.

     The solution to this problem is for the client to provide two
     counts to the server. The first is the number of bytes of directory
     information that the client really wants, dircount.  The second is
     the maximum number of bytes in the result, including the attributes
     and file handles, maxcount. Thus, the server will issue a
     VOP_READDIR for only the number of bytes that the client really
     wants to get, not an inflated number.  This should help to reduce
     the size of VOP_READDIR requests on the server, thus reducing the
     amount of work done there, and to reduce the number of VOP_LOOKUP,
     VOP_GETATTR, and other calls done by the server to construct
     attributes and file handles.

   ERRORS

     NFS4ERR_IO

     NFS4ERR_ACCES

     NFS4ERR_NOTDIR

     NFS4ERR_INVAL

     NFS4ERR_STALE

     NFS4ERR_BADHANDLE

     NFS4ERR_BAD_COOKIE

     NFS4ERR_TOOSMALL

Expires: March 2000                                           [Page 131]


Draft Protocol Specification  NFS version 4               September 1999

     NFS4ERR_NOTSUPP

     NFS4ERR_SERVERFAULT

     NFS4ERR_JUKEBOX

     NFS4ERR_FHEXPIRED

     NFS4ERR_WRONGSEC

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 132]


Draft Protocol Specification  NFS version 4               September 1999

12.2.23.  Operation 24: READLINK - Read Symbolic Link

   SYNOPSIS

     (cfh) -> linktext

   ARGUMENT

     /* CURRENT_FH: symlink */
     void;

   RESULT

     struct READLINK4resok {
             linktext4       link;
     };

     union READLINK4res switch (nfsstat4 status) {
      case NFS4_OK:
              READLINK4resok resok4;
      default:
              void;
     };

   DESCRIPTION

     READLINK reads the data associated with a symbolic link.  The data
     is a UTF-8 string that is opaque to the server.  That is, whether
     created by an NFS client or created locally on the server, the data
     in a symbolic link is not interpreted when created, but is simply
     stored.

   IMPLEMENTATION

     A symbolic link is nominally a pointer to another file.  The data
     is not necessarily interpreted by the server, just stored in the
     file.  It is possible for a client implementation to store a path
     name that is not meaningful to the server operating system in a
     symbolic link.  A READLINK operation returns the data to the client
     for interpretation. If different implementations want to share
     access to symbolic links, then they must agree on the

Expires: March 2000                                           [Page 133]


Draft Protocol Specification  NFS version 4               September 1999

     interpretation of the data in the symbolic link.

     The READLINK operation is only allowed on objects of type, NF4LNK.
     The server should return the error, NFS4ERR_INVAL, if the object is
     not of type, NF4LNK.

   ERRORS

     NFS4ERR_IO

     NFS4ERR_INVAL

     NFS4ERR_ACCES

     NFS4ERR_STALE

     NFS4ERR_BADHANDLE

     NFS4ERR_NOTSUPP

     NFS4ERR_SERVERFAULT

     NFS4ERR_JUKEBOX

     NFS4ERR_FHEXPIRED

     NFS4ERR_WRONGSEC

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 134]


Draft Protocol Specification  NFS version 4               September 1999

12.2.24.  Operation 25: REMOVE - Remove Filesystem Object

   SYNOPSIS

     (cfh), filename -> change_info

   ARGUMENT

     struct REMOVE4args {
             /* CURRENT_FH: directory */
             component4       target;
     };

   RESULT

     struct REMOVE4resok {
             change_info4    cinfo;
     }

     union REMOVE4res switch (nfsstat4 status) {
      case NFS4_OK:
              REMOVE4resok   resok4;
      default:
              void;
     }

   DESCRIPTION

     The REMOVE procecure removes (deletes) a directory entry named by
     filename from the directory corresponding to the current
     filehandle.  If the entry in the directory was the last reference
     to the corresponding file system object, the object may be
     destroyed.

     For the directory where the filename was removed, the server
     returns change_info4 information in cinfo.  With the atomic field
     of the change_info4 struct, the server will indicate if the before
     and after change attributes were obtained atomically with respect
     to the removal.

Expires: March 2000                                           [Page 135]


Draft Protocol Specification  NFS version 4               September 1999

   IMPLEMENTATION

     NFS versions 2 and 3 required a different operator RMDIR for
     directory removal.  NFS version 4 REMOVE can be used to delete any
     directory entry independent of its filetype.

     The concept of last reference is server specific. However, if the
     nlink field in the previous attributes of the object had the value
     1, the client should not rely on referring to the object via a file
     handle. Likewise, the client should not rely on the resources (disk
     space, directory entry, and so on.) formerly associated with the
     object becoming immediately available. Thus, if a client needs to
     be able to continue to access a file after using REMOVE to remove
     it, the client should take steps to make sure that the file will
     still be accessible. The usual mechanism used is to use RENAME to
     rename the file from its old name to a new hidden name.

   ERRORS

     NFS4ERR_NOENT

     NFS4ERR_IO

     NFS4ERR_ACCES

     NFS4ERR_NOTDIR

     NFS4ERR_ROFS

     NFS4ERR_NAMETOOLONG

     NFS4ERR_NOTEMPTY

     NFS4ERR_STALE

     NFS4ERR_BADHANDLE

     NFS4ERR_NOTSUPP

     NFS4ERR_SERVERFAULT

     NFS4ERR_FHEXPIRED

     NFS4ERR_WRONGSEC

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 136]


Draft Protocol Specification  NFS version 4               September 1999

12.2.25.  Operation 26: RENAME - Rename Directory Entry

   SYNOPSIS

     (cfh), oldname, newdir, newname -> source_change_info,
     target_change_info

   ARGUMENT

     struct RENAME4args {
             /* CURRENT_FH: source directory */
             component4       oldname;
             nfs4_fh         newdir;
             component4       newname;
     };

   RESULT

     struct RENAME4resok {
             change_info4    source_cinfo;
             change_info4    target_cinfo;
     };

     union RENAME4res switch (nfsstat4 status) {
      case NFS4_OK:
              RENAME4resok   resok4;
      default:
              void;
     };

   DESCRIPTION

     RENAME renames the object identified by oldname in the directory
     corresponding to the current filehandle to newname in directory
     newdir. The operation is required to be atomic to the client.
     Source and target directories must reside on the same file system
     on the server.

     If the directory, newdir, already contains an entry with the name,
     newname, the source object must be compatible with the target:
     either both are non-directories or both are directories and the
     target must be empty. If compatible, the existing target is removed

Expires: March 2000                                           [Page 137]


Draft Protocol Specification  NFS version 4               September 1999

     before the rename occurs. If they are not compatible or if the
     target is a directory but not empty, the server should return the
     error, NFS4ERR_EXIST.

     If oldname and newname both refer to the same file (they might be
     hard links of each other), then RENAME should perform no action and
     return success.

     For both directories involved in the RENAME, the server returns
     change_info4 information.  With the atomic field of the
     change_info4 struct, the server will indicate if the before and
     after change attributes were obtained atomically with respect to
     the rename.

   IMPLEMENTATION

     The RENAME operation must be atomic to the client. The statement
     "source and target directories must reside on the same file system
     on the server" means that the fsid fields in the attributes for the
     directories are the same. If they reside on different file systems,
     the error, NFS4ERR_XDEV, is returned.  Even though the operation is
     atomic, the status, NFS4ERR_MLINK, may be returned if the server
     used a "unlink/link/unlink" sequence internally.

     A file handle may or may not become stale on a rename.  However,
     server implementors are strongly encouraged to attempt to keep file
     handles from becoming stale in this fashion.

     On some servers, the filenames, "." and "..", are illegal as either
     oldname or newname. In addition, neither oldname nor newname can be
     an alias for the source directory.  These servers will return the
     error, NFS4ERR_INVAL, in these cases.

   ERRORS

     NFS4ERR_NOENT

     NFS4ERR_IO

     NFS4ERR_ACCES

     NFS4ERR_EXIST

     NFS4ERR_XDEV

Expires: March 2000                                           [Page 138]


Draft Protocol Specification  NFS version 4               September 1999

     NFS4ERR_NOTDIR

     NFS4ERR_ISDIR

     NFS4ERR_INVAL

     NFS4ERR_NOSPC

     NFS4ERR_ROFS

     NFS4ERR_MLINK

     NFS4ERR_NAMETOOLONG

     NFS4ERR_NOTEMPTY

     NFS4ERR_DQUOT

     NFS4ERR_STALE

     NFS4ERR_BADHANDLE

     NFS4ERR_NOTSUPP

     NFS4ERR_SERVERFAULT

     NFS4ERR_FHEXPIRED

     NFS4ERR_WRONGSEC

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 139]


Draft Protocol Specification  NFS version 4               September 1999

12.2.26.  Operation 27: RENEW - Renew a Lease

   SYNOPSIS

     stateid -> ()

   ARGUMENT

     struct RENEW4args {
             stateid4        stateid;
     };

   RESULT

     struct RENEW4res {
             nfsstat4        status;
     };

   DESCRIPTION

     The RENEW procedure is used by the client to renew leases which it
     currently holds at a server.  The processing the RENEW request, the
     server renews all leases associated with the client.  The
     associated leases are determined by the client id provided via the
     SETCLIENTID procedure.

   IMPLEMENTATION

   ERRORS

     NFS4ERR_SERVERFAULT

     NFS4ERR_EXPIRED

     NFS4ERR_GRACE

     NFS4ERR_WRONGSEC

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 140]


Draft Protocol Specification  NFS version 4               September 1999

12.2.27.  Operation 28: RESTOREFH - Restore Saved Filehandle

   SYNOPSIS

     (sfh) -> (cfh)

   ARGUMENT

     /* SAVED_FH: */
     void;

   RESULT

     struct RESTOREFH4res {
             /* CURRENT_FH: value of saved fh */
             nfsstat4        status;
     };

   DESCRIPTION

     Set the current filehandle to the value in the saved filehandle.
     If there is no saved filehandle then return an error NFS4ERR_INVAL.

   IMPLEMENTATION

     Procedures like OPEN and LOOKUP use the current filehandle to
     represent a directory and replace it with a new filehandle.
     Assuming the previous filehandle was saved with a SAVEFH operator,
     the previous filehandle can be restored as the current filehandle.
     This is commonly used to obtain post-operation attributes for the
     directory, e.g.

             1. PUTFH (directory filehandle)
             2. SAVEFH
             3. GETATTR attrbits     (pre-op dir attrs)
             4. CREATE optbits "foo" attrs
             5. GETATTR attrbits     (file attributes)
             6. RESTOREFH
             7. GETATTR attrbits     (post-op dir attrs)

Expires: March 2000                                           [Page 141]


Draft Protocol Specification  NFS version 4               September 1999

   ERRORS

     NFS4ERR_BADHANDLE

     NFS4ERR_FHEXPIRED

     NFS4ERR_MOVED

     NFS4ERR_NOFILEHANDLE

     NFS4ERR_SERVERFAULT

     NFS4ERR_STALE

     NFS4ERR_WRONGSEC

Expires: March 2000                                           [Page 142]


Draft Protocol Specification  NFS version 4               September 1999

12.2.28.  Operation 29: SAVEFH - Save Current Filehandle

   SYNOPSIS

     (cfh) -> (sfh)

   ARGUMENT

     /* CURRENT_FH: */
     void;

   RESULT

     struct SAVEFH4res {
             /* SAVED_FH: value of current fh */
             nfsstat4        status;
     };

   DESCRIPTION

     Save the current filehandle.  If a previous filehandle was saved
     then it is no longer accessible.  The saved filehandle can be
     restored as the current filehandle with the RESTOREFH operator.

   IMPLEMENTATION

   ERRORS

     NFS4ERR_BADHANDLE

     NFS4ERR_FHEXPIRED

     NFS4ERR_MOVED

     NFS4ERR_NOFILEHANDLE

     NFS4ERR_SERVERFAULT

     NFS4ERR_STALE

Expires: March 2000                                           [Page 143]


Draft Protocol Specification  NFS version 4               September 1999

     NFS4ERR_WRONGSEC

Expires: March 2000                                           [Page 144]


Draft Protocol Specification  NFS version 4               September 1999

12.2.29.  Operation 30: SECINFO - Obtain Available Security

   SYNOPSIS

     (cfh), filename -> { secinfo }

   ARGUMENT

     struct SECINFO4args {
             /* CURRENT_FH: */
             component4     name;
     };

   RESULT

     struct rpcsec_gss_info {
             sec_oid4 oid;
             qop4 qop;
             rpc_gss_svc_t service;
     };

     struct secinfo4 {
             unsigned int flavor;
             opaque flavor_info<>;   /* null for AUTH_SYS, AUTH_NONE;
                                        contains rpcsec_gss_info for
                                        RPCSEC_GSS. */
     };

     struct SECINFO4resok {
             secinfo4 reply<>;
     };

     union SECINFO4res switch (nfsstat4 status) {
      case NFS4_OK:
              SECINFO4resok resok4;
      default:
              void;
     };

   DESCRIPTION

Expires: March 2000                                           [Page 145]


Draft Protocol Specification  NFS version 4               September 1999

     The SECINFO procedure is used by the client to obtain a list of
     valid RPC authentication flavors for a specific file handle, file
     name pair.  The result will contain an array which represents the
     security mechanisms available.  The array entries are represented
     by the secinfo4 structure.  The field 'flavor' will contain a value
     of AUTH_NONE, AUTH_SYS (as defined in [RFC1831]), or RPCSEC_GSS (as
     defined in [RFC2203]).

     For the flavors, AUTH_NONE, and AUTH_SYS no additional security
     information is returned.  For a return value of RPCSEC_GSS, a
     security triple is returned that contains the mechanism object id
     (as defined in [RFC2078]), the quality of protection (as defined in
     [RFC2078]) and the service type (as defined in [RFC2203]).  It is
     possible for SECINFO to return multiple entries with flavor equal
     to RPCSEC_GSS with different security triple values.

   IMPLEMENTATION

     The SECINFO procedure is expected to be used by the NFS client when
     the error value of NFS4ERR_WRONGSEC is returned from another NFS
     procedure.  This signifies to the client that the server's security
     policy is different from what the client is currently using.  At
     this point, the client is expected to obtain a list of possible
     security flavors and choose what best suits its policies.

   ERRORS

     NFS4ERR_SERVERFAULT

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 146]


Draft Protocol Specification  NFS version 4               September 1999

12.2.30.  Operation 31: SETATTR - Set Attributes

   SYNOPSIS

     (cfh), attrbits, attrvals -> -

   ARGUMENT

     struct SETATTR4args {
             /* CURRENT_FH: target object */
             stateid4        stateid;
             fattr4          obj_attributes;
     };

   RESULT

     struct SETATTR4res {
             nfsstat4        status;
     };

   DESCRIPTION

     The SETATTR Procedure changes one or more of the attributes of a
     file system object. The new attributes are specified with a bitmap
     and the attributes that follow the bitmap in bit order.

     The stateid is necessary for SETATTR's that change the size of file
     (modify the attribute object_size).  This stateid represents a
     record lock, share reservation, or delegation which must be valid
     for the SETATTR to modify the file data.

   IMPLEMENTATION

     The file size attribute is used to request changes to the size of a
     file. A value of 0 (zero) causes the file to be truncated, a value
     less than the current size of the file causes data from new size to
     the end of the file to be discarded, and a size greater than the
     current size of the file causes logically zeroed data bytes to be
     added to the end of the file.  Servers are free to implement this
     using holes or actual zero data bytes. Clients should not make any

Expires: March 2000                                           [Page 147]


Draft Protocol Specification  NFS version 4               September 1999

     assumptions regarding a server's implementation of this feature,
     beyond that the bytes returned will be zeroed. Servers must support
     extending the file size via SETATTR.

     SETATTR is not guaranteed atomic. A failed SETATTR may partially
     change a file's attributes.

     Changing the size of a file with SETATTR indirectly changes the
     time_modify. A client must account for this as size changes can
     result in data deletion.

     If server and client times differ, programs that compare client
     time to file times can break. A time maintenance protocol should be
     used to limit client/server time skew.

     If the server cannot successfully set all the attributes it must
     return an NFS4ERR_INVAL error. If the server can only support 32
     bit offsets and sizes, a SETATTR request to set the size of a file
     to larger than can be represented in 32 bits will be rejected with
     this same error.

   ERRORS

     NFS4ERR_PERM

     NFS4ERR_IO

     NFS4ERR_ACCES

     NFS4ERR_INVAL

     NFS4ERR_FBIG

     NFS4ERR_NOSPC

     NFS4ERR_ROFS

     NFS4ERR_DQUOT

     NFS4ERR_STALE

     NFS4ERR_BADHANDLE

     NFS4ERR_NOTSUPP

     NFS4ERR_SERVERFAULT

Expires: March 2000                                           [Page 148]


Draft Protocol Specification  NFS version 4               September 1999

     NFS4ERR_JUKEBOX

     NFS4ERR_DENIED

     NFS4ERR_GRACE

     NFS4ERR_FHEXPIRED

     NFS4ERR_WRONGSEC

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 149]


Draft Protocol Specification  NFS version 4               September 1999

12.2.31.  Operation 32: SETCLIENTID - Negotiated Clientid

   SYNOPSIS

     verifier, client -> clientid

   ARGUMENT

     struct cid {
             opaque          verifier[4];
             opaque          id<>;
     };

     union nfs_client_id switch (clientid4 clientid) {
      case 0:
              cid            ident;
      default:
              void;
     };

     struct SETCLIENTID4args {
             seqid4          seqid;
             nfs_client_id   client;
     };

   RESULT

     union SETCLIENTID4res switch (nfsstat4 status) {
      case NFS4_OK:
              clientid4      clientid;
      default:
              void;
     };

   DESCRIPTION

     The SETCLIENTID procedure introduces the ability of the client to
     notify the server of its intention to use a particular client
     identifier and verifier pair.  Upon successful completion the
     server will return a clientid which is used in subsequent file
     locking requests.

Expires: March 2000                                           [Page 150]


Draft Protocol Specification  NFS version 4               September 1999

   IMPLEMENTATION

     The server takes the verifier and client identification supplied
     and search for a match of the client identification.  If no match
     is found the server saves the principal/uid information along with
     the verifier and client identification and returns a unique
     clientid that is used as a short hand reference to the supplied
     information.

     If the server find matching client identification and a
     corresponding match in principal/uid, the server releases all
     locking state for the client and returns a new clientid.

   ERRORS

     NFS4ERR_INVAL

     NFS4ERR_SERVERFAULT

     NFS4ERR_CLID_INUSE

Expires: March 2000                                           [Page 151]


Draft Protocol Specification  NFS version 4               September 1999

12.2.32.  Operation 33: VERIFY - Verify Same Attributes

   SYNOPSIS

     (cfh), attrbits, attrvals -> -

   ARGUMENT

     struct VERIFY4args {
             /* CURRENT_FH: object */
             bitmap4         attr_request;
             fattr4          obj_attributes;
     };

   RESULT

     struct VERIFY4res {
             nfsstat4        status;
     };

   DESCRIPTION

     The VERIFY procedure is used to verify that attributes have a value
     assumed by the client before proceeding with following operations
     in the compound request.  For instance, a VERIFY can be used to
     make sure that the file size has not changed for an append-mode
     write:

             1. PUTFH 0x0123456
             2. VERIFY attrbits attrs
             3. WRITE 450328 4096

     If the attributes are not as expected, then the request fails and
     the data is not appended to the file.

   IMPLEMENTATION

   ERRORS

Expires: March 2000                                           [Page 152]


Draft Protocol Specification  NFS version 4               September 1999

     NFS4ERR_ACCES

     NFS4ERR_INVAL

     NFS4ERR_STALE

     NFS4ERR_BADHANDLE

     NFS4ERR_NOTSUPP

     NFS4ERR_SERVERFAULT

     NFS4ERR_JUKEBOX

     NFS4ERR_FHEXPIRED

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 153]


Draft Protocol Specification  NFS version 4               September 1999

12.2.33.  Operation 34: WRITE - Write to File

   SYNOPSIS

     (cfh), offset, count, stability, stateid, data -> count, committed,
     verifier

   ARGUMENT

     enum stable_how4 {
             UNSTABLE4       = 0,
             DATA_SYNC4      = 1,
             FILE_SYNC4      = 2
     };

     struct WRITE4args {
             /* CURRENT_FH: file */
             stateid4        stateid;
             offset4         offset;
             count4          count;
             stable_how4     stable;
             opaque          data<>;
     };

   RESULT

     struct WRITE4resok {
             count4          count;
             stable_how4     committed;
             writeverf4      verf;
     };

     union WRITE4res switch (nfsstat4 status) {
      case NFS4_OK:
              WRITE4resok    resok4;
      default:
              void;
     };

   DESCRIPTION

     The WRITE procedure is used to write data to a regular file.  The

Expires: March 2000                                           [Page 154]


Draft Protocol Specification  NFS version 4               September 1999

     target file is specified by the current filehandle.  The offset
     specifies the offset where the data should be written.  An offset
     of 0 (zero) specifies that the write should start at the beginning
     of the file.  The count represents the number of bytes of data that
     are to be written.  If the count is 0 (zero), the WRITE will
     succeed and return a count of 0 (zero) subject to permissions
     checking.  The server may choose to write fewer bytes than
     requested by the client.

     Part of the write request is a specification of how the write is to
     be performed.  The client specifies with the stable parameter the
     method of how the data is to be processed by the server.  If stable
     is FILE_SYNC, the server must commit the data written plus all file
     system metadata to stable storage before returning results. This
     corresponds to the NFS version 2 protocol semantics. Any other
     behavior constitutes a protocol violation. If stable is DATA_SYNC,
     then the server must commit all of the data to stable storage and
     enough of the metadata to retrieve the data before returning.  The
     server implementor is free to implement DATA_SYNC in the same
     fashion as FILE_SYNC, but with a possible performance drop.  If
     stable is UNSTABLE, the server is free to commit any part of the
     data and the metadata to stable storage, including all or none,
     before returning a reply to the client. There is no guarantee
     whether or when any uncommitted data will subsequently be committed
     to stable storage. The only guarantees made by the server are that
     it will not destroy any data without changing the value of verf and
     that it will not commit the data and metadata at a level less than
     that requested by the client.

     The stateid returned from a previous record lock or share
     reservation request is provided as part of the argument.  The
     stateid is used by the server to verify that the associated lock is
     still valid and to update lease timeouts for the client.

     Upon successful completion, the following results are returned.
     The count result is the number of bytes of data written to the
     file. The server may write fewer bytes than requested. If so, the
     actual number of bytes written starting at location, offset, is
     returned.

     The server also returns an indication of the level of commitment of
     the data and metadata via committed. If the server committed all
     data and metadata to stable storage, committed should be set to
     FILE_SYNC. If the level of commitment was at least as strong as
     DATA_SYNC, then committed should be set to DATA_SYNC.  Otherwise,
     committed must be returned as UNSTABLE. If stable was FILE_SYNC,
     then committed must also be FILE_SYNC: anything else constitutes a
     protocol violation. If stable was DATA_SYNC, then committed may be

Expires: March 2000                                           [Page 155]


Draft Protocol Specification  NFS version 4               September 1999

     FILE_SYNC or DATA_SYNC: anything else constitutes a protocol
     violation. If stable was UNSTABLE, then committed may be either
     FILE_SYNC, DATA_SYNC, or UNSTABLE.

     The final portion of the result is the write verifier, verf.  The
     write verifier is a cookie that the client can use to determine
     whether the server has changed state between a call to WRITE and a
     subsequent call to either WRITE or COMMIT.  This cookie must be
     consistent during a single instance of the NFS version 4 protocol
     service and must be unique between instances of the NFS version 4
     protocol server, where uncommitted data may be lost.

     If a client writes data to the server with the stable argument set
     to UNSTABLE and the reply yields a committed response of DATA_SYNC
     or UNSTABLE, the client will follow up some time in the future with
     a COMMIT operation to synchronize outstanding asynchronous data and
     metadata with the server's stable storage, barring client error. It
     is possible that due to client crash or other error that a
     subsequent COMMIT will not be received by the server.

   IMPLEMENTATION

     It is possible for the server to write fewer than count bytes of
     data. In this case, the server should not return an error unless no
     data was written at all. If the server writes less than count
     bytes, the client should issue another WRITE to write the remaining
     data.

     It is assumed that the act of writing data to a file will cause the
     time_modified of the file to be updated. However, the time_modified
     of the file should not be changed unless the contents of the file
     are changed.  Thus, a WRITE request with count set to 0 should not
     cause the time_modified of the file to be updated.

     The definition of stable storage has been historically a point of
     contention. The following expected properties of stable storage may
     help in resolving design issues in the implementation. Stable
     storage is persistent storage that survives:

             1. Repeated power failures.
             2. Hardware failures (of any board, power supply, etc.).
             3. Repeated software crashes, including reboot cycle.

     This definition does not address failure of the stable storage
     module itself.

Expires: March 2000                                           [Page 156]


Draft Protocol Specification  NFS version 4               September 1999

     The verifier, is defined to allow a client to detect different
     instances of an NFS version 4 protocol server over which cached,
     uncommitted data may be lost. In the most likely case, the verifier
     allows the client to detect server reboots. This information is
     required so that the client can safely determine whether the server
     could have lost cached data. If the server fails unexpectedly and
     the client has uncommitted data from previous WRITE requests (done
     with the stable argument set to UNSTABLE and in which the result
     committed was returned as UNSTABLE as well) it may not have flushed
     cached data to stable storage. The burden of recovery is on the
     client and the client will need to retransmit the data to the
     server.

     A suggested verifier would be to use the time that the server was
     booted or the time the server was last started (if restarting the
     server without a reboot results in lost buffers).

     The committed field in the results allows the client to do more
     effective caching. If the server is committing all WRITE requests
     to stable storage, then it should return with committed set to
     FILE_SYNC, regardless of the value of the stable field in the
     arguments. A server that uses an NVRAM accelerator may choose to
     implement this policy.  The client can use this to increase the
     effectiveness of the cache by discarding cached data that has
     already been committed on the server.

     Some implementations may return NFS4ERR_NOSPC instead of
     NFS4ERR_DQUOT when a user's quota is exceeded.

   ERRORS

     NFS4ERR_IO

     NFS4ERR_ACCES

     NFS4ERR_INVAL

     NFS4ERR_FBIG

     NFS4ERR_NOSPC

     NFS4ERR_ROFS

     NFS4ERR_DQUOT

     NFS4ERR_STALE

Expires: March 2000                                           [Page 157]


Draft Protocol Specification  NFS version 4               September 1999

     NFS4ERR_BADHANDLE

     NFS4ERR_SERVERFAULT

     NFS4ERR_JUKEBOX

     NFS4ERR_LOCKED

     NFS4ERR_GRACE

     NFS4ERR_FHEXPIRED

     NFS4ERR_WRONGSEC

     NFS4ERR_MOVED

Expires: March 2000                                           [Page 158]


Draft Protocol Specification  NFS version 4               September 1999

13.  NFS Version 4 Callback Procedures

   The procedures used for callbacks are defined in the following
   sections.  In the interest of clarity, the terms "client" and
   "server" refer to NFS clients and servers, despite the fact that for
   an individual callback RPC, the sense of these terms would be
   precisely the opposite.

13.1.  Procedure 0: CB_NULL - No Operation

   SYNOPSIS

     <null>

   ARGUMENT

     void;

   RESULT

     void;

   DESCRIPTION

     Standard ONCRPC NULL procedure.  Void argument, void response.

   ERRORS

     None.

Expires: March 2000                                           [Page 159]


Draft Protocol Specification  NFS version 4               September 1999

13.2.  Procedure 1: CB_COMPOUND - Compound Operations

   SYNOPSIS

     compoundargs -> compoundres

   ARGUMENT

     union cb_opunion switch (unsigned opcode) {
             case <OPCODE>: <argument>;
             ...
     };

     struct cb_op {
             cb_opunion      ops;
     };

     struct CB_COMPOUND4args {
             utf8string      tag;
             cb_op           oplist<>;
     };

   RESULT

     union cb_resultdata switch (unsigned resop){
       case <OPCODE: <result>;
       ...
     };

     struct CB_COMPOUND4res {
             nfsstat4 status;
             utf8string      tag;
             cb_resultdata   data<>;
     };

     union opunion switch (unsigned opcode) {
             case <OPCODE>: <argument>;
             ...
     };

     struct op {
             opunion         ops;
     };

     struct COMPOUND4args {

Expires: March 2000                                           [Page 160]


Draft Protocol Specification  NFS version 4               September 1999

             utf8string      tag;
             op              oplist<>;
     };

   DESCRIPTION

     The CB_COMPOUND procedure is used to combine one or more of the
     callback procedures into a single RPC request.  The main callback
     RPC program has two main procedures: CB_NULL and CB_COMPOUND. All
     other procedures use the CB_COMPOUND procedure as a wrapper.

     In the processing of the CB_COMPOUND procedure, the server may find
     that it does not have the available resources to execute any or all
     of the procedures within the CB_COMPOUND sequence.  In this case,
     the error NFS4ERR_RESOURCE will be returned for the particular
     procedure within the CB_COMPOUND operation where the resource
     exhaustion occurred.  This assumes that all previous procedures
     within the CB_COMPOUND sequence have been evaluated successfully.

   IMPLEMENTATION

     The CB_COMPOUND procedure is used to combine individual procedures
     into a single RPC request.  The server interprets each of the
     procedures in turn.  If a procedure is executed by the server and
     the status of that procedure is NFS4_OK, then the next procedure in
     the CB_COMPOUND procedure is executed.  The server continues this
     process until there are no more procedures to be executed or one of
     the procedures has a status value other than NFS4_OK.

   ERRORS

     NFS4ERR_RESOURCE

Expires: March 2000                                           [Page 161]


Draft Protocol Specification  NFS version 4               September 1999

13.2.1.  Procedure 2: CB_GETATTR - Get Attributes

   SYNOPSIS

     fh, attrbits -> attrbits, attrvals

   ARGUMENT

     struct CB_GETATTR4args {
             nfs_fh4 fh;
             bitmap4 attr_request;
     };

   RESULT

     struct CB_GETATTR4resok {
             fattr4  obj_attributes;
     };

     union CB_GETATTR4res switch (nfsstat4 status) {
      case NFS4_OK:
              CB_GETATTR4resok       resok4;
      default:
              void;
     };

   DESCRIPTION

     CB_GETATTR is used to obtain the attributes modified by an open
     delegate to allow the server to respond to GETATTR requests for a
     file which is the subject of an open delegation.

   IMPLEMENTATION

     The client returns attrbits and the associated attribute values
     only for attributes that it may change (change, time_modify,
     object_size).  It may further limit the response to attributes that
     it has in fact changed during the scope of the delegation.

Expires: March 2000                                           [Page 162]


Draft Protocol Specification  NFS version 4               September 1999

   ERRORS

     <TBD>

Expires: March 2000                                           [Page 163]


Draft Protocol Specification  NFS version 4               September 1999

13.2.2.  Procedure 3: CB_RECALL - Recall an Open Delegation

   SYNOPSIS

     stateid, truncate, fh

   ARGUMENT

     struct CB_RECALL4args {
             stateid4        stateid;
             bool            truncate;
             nfs_fh4         fh;
     };

   RESULT

     struct CB_RECALL4res {
             nfsstat4        status;
     };

   DESCRIPTION

     CB_RECALL is used to begin the process of recalling an open
     delegation and returning it to the server.

     The truncate flag is used to optimize recall for a file which is
     about to be truncated to zero.  When it is set, the client is freed
     of obligation to propagate modified data for the file to the
     server, since this data is irrelevant.

   IMPLEMENTATION

     The client should reply to the callback immediately.  Replying does
     not complete the recall.  The recall is not complete until the
     delegation is returned using a DELEGRETURN.

   ERRORS

Expires: March 2000                                           [Page 164]


Draft Protocol Specification  NFS version 4               September 1999

     <TBD>

Expires: March 2000                                           [Page 165]


Draft Protocol Specification  NFS version 4               September 1999

14.  Locking notes

14.1.  Short and long leases

   The usual lease trade-offs apply: short leases are good for fast
   server recovery at a cost of increased RENEW or READ (with zero
   length) requests.

   Longer leases are certainly kinder and gentler to large internet
   servers trying to handle huge numbers of clients. RENEW requests drop
   in direct proportion to the lease time.  The disadvantages of long
   leases are slower server recover after crash (server must wait for
   leases to expire and grace period before granting new lock requests)
   and increased file contention (if client fails to transmit an unlock
   request then server must wait for lease expiration before granting
   new locks).

   Long leases are usable if the server is to store lease state in non-
   volatile memory.  Upon recovery, the server can reconstruct the lease
   state from its non-volatile memory and continue operation with its
   clients and therefore long leases are not an issue.

14.2.  Clocks and leases

   To avoid the need for synchronized clocks, lease times are granted by
   the server as a time delta, though there is a requirement that the
   client and server clocks do not drift excessively over the duration
   of the lock.  There is also the issue of propagation delay across the
   network which could easily be several hundred milliseconds across the
   Internet as well as the possibility that requests will be lost and
   need to be retransmitted.

   To take propagation delay into account, the client should subtract a
   it from lease times, e.g. if the client estimates the one-way
   propagation delay as 200 msec, then it can assume that the lease is
   already 200 msec old when it gets it.  In addition, it'll take
   another 200 msec to get a response back to the server.  So the client
   must send a lock renewal or write data back to the server 400 msec
   before the lease would expire.

   The client could measure propagation delay with reasonable accuracy
   by measuring the round-trip time for lock extensions assuming that
   there's not much server processing overhead in an extension.

14.3.  Locks and lease times

   Lock requests do not contain desired lease times.  The server

Expires: March 2000                                           [Page 166]


Draft Protocol Specification  NFS version 4               September 1999

   allocates leases with no information from the client.  The assumption
   here is that the client really has no idea of just how long the lock
   will be required. If a scenario can be found where a hint from the
   client as to the maximum lease time desired would be useful, then
   this feature could be added to lock requests.

14.4.  Locking of directories and other meta-files

   A question: should directories and/or other file-system objects like
   symbolic links be lockable ?  Clients will want to cache whole
   directories. It would be nice to have consistent directory caches,
   but it would require that any client creating a new file get a write
   lock on the directory and be prepared to handle lock denial.  Is the
   weak cache consistency that we currently have for directories
   acceptable ?  I think perhaps it is - given the expense of doing full
   consistency on an Internet scale.

14.5.  Proxy servers and leases

   Proxy servers.  There is some interest in having NFS V4 support
   caching proxies.  Support for proxy caching is a requirement if
   servers are to handle large numbers of clients - clients that may
   have little or no ability to cache on their own.  How could proxy
   servers use lease-based locking ?

14.6.  Locking and the new latency

   Latency caused by locking.  If a client wants to update a file then
   it will have to wait until the leases on read locks have expired.  If
   the leases are of the order of 60 seconds or several minutes then the
   client (and end-user) may be blocked for a while.  This is unfamiliar
   for current NFS users who are not bothered by mandatory locking - but
   it could be an issue if we decide we like the caching benefits.  A
   similar problem exists for clients that wish to read a file that is
   write locked.  The read-lock case is likely to be more common if
   read-locking is used to protect cached data on the client.

Expires: March 2000                                           [Page 167]


Draft Protocol Specification  NFS version 4               September 1999

15.  Internationalization

   The primary issue in which NFS needs to deal with
   internationalization, or i18n, is with respect to file names and
   other strings as used within the protocol.  NFS' choice of string
   representation must allow reasonable name/string access to clients
   which use various languages.  The UTF-8 encoding allows for this type
   of access and this choice is explained in the following.

15.1.  Universal Versus Local Character Sets

   [RFC1345] describes a table of 16 bit characters for many different
   languages (the bit encodings match Unicode, though of course RFC1345
   is somewhat out of date with respect to current Unicode assignments).
   Each character from each language has a unique 16 bit value in the 16
   bit character set. Thus this table can be thought of as a universal
   character set. [RFC1345] then talks about groupings of subsets of the
   entire 16 bit character set into "Charset Tables". For example one
   might take all the Greek characters from the 16 bit table (which are
   are consecutively allocated), and normalize their offsets to a table
   that fits in 7 bits.  Thus we find that "lower case alpha" is in the
   same position as "upper case a" in the US-ASCII table, and "upper
   case alpha" is in the same position as "lower case a" in the US-ASCII
   table.

   These normalized subset character sets can be thought of as "local
   character sets", suitable for an operating system locale.

   Local character sets are not suitable for the NFS protocol.  Consider
   someone who creates a file with a name in a Swedish character set. If
   someone else later goes to access the file with their locale set to
   the Swedish language, then there are no problems. But if someone in
   say the US-ASCII locale goes to access the file, the file name will
   look very different, because the Swedish characters in the 7 bit
   table will now be represented in US-ASCII characters on the display.
   It would be preferable to give the US-ASCII user a way to display the
   file name using Swedish glyphs. In order to do that, the NFS protocol
   would have to include the locale with the file name on each operation
   to create a file.

   But then what of the situation when we have a path name on the server
   like:

           /component-1/component-2/component-3

   Each component could have been created with a different locale. If
   one issues CREATE with multi-component path name, and if some of the
   leading components already exist, what is to be done with the

Expires: March 2000                                           [Page 168]


Draft Protocol Specification  NFS version 4               September 1999

   existing components?  Is the current locale attribute replaced with
   the user's current one?  These types of situations quickly become too
   complex when there is an alternate solution.

   If NFS V4 used a universal 16 bit or 32 bit character set (or a
   encoding of a 16 bit or 32 bit character set into octets), then
   server and client need not care if the locale of the user accessing
   the file is different than the locale of the user who created the
   file.  The unique 16 bit or 32 bit encoding of the character allows
   for determination of what language the character is from and also how
   to display that character on the client.  The server need not know
   what locales are used.

15.2.  Overview of Universal Character Set Standards

   The previous section makes a case for using a universal character set
   in NFS version 4.  This section makes the case for using UTF-8 as the
   specific universal character set for NFS version 4.

   [RFC2279] discusses UTF-* (UTF-8 and other UTF-XXX encodings),
   Unicode, and UCS-*. There are two standards bodies managing universal
   code sets:

   o    ISO/IEC which has the standard 10646-1

   o    Unicode which has the Unicode standard

   Both standards bodies have pledged to track each other's assignments
   of character codes.

   The following is a brief analysis of the various standards.

   UCS       Universal Character Set. This is ISO/IEC 10646-1: "a
             multi-octet character set called the Universal Character
             Set (UCS), which encompasses most of the world's writing
             systems."

   UCS-2     a two octet per character encoding that addresses the first
             2^16 characters of UCS. Currently there are no UCS
             characters beyond that range.

   UCS-4     a four octet per character encoding that permits the
             encoding of up to 2^31 characters.

Expires: March 2000                                           [Page 169]


Draft Protocol Specification  NFS version 4               September 1999

   UTF       UCS transformation format.

   UTF-1     Only historical interest; it has been removed from 10646-1

   UTF-7     Encodes the entire "repertoire" of UCS "characters using
             only octets with the higher order bit clear".  [RFC2152]
             describes UTF-7. UTF-7 accomplishes this by reserving one
             of the 7bit US-ASCII characters as a "shift" character to
             indicate non-US-ASCII characters.

   UTF-8     Unlike UTF-7, uses all 8 bits of the octets. US-ASCII
             characters are encoded as before unchanged. Any octet with
             the high bit cleared can only mean a US-ASCII character.
             The high bit set means that a UCS character is being
             encoded.

   UTF-16    Encodes UCS-4 characters into UCS-2 characters using a
             reserved range in UCS-2.

   Unicode   Unicode and UCS-2 are the same; [RFC2279] states:

        Up to the present time, changes in Unicode and amendments
        to ISO/IEC 10646 have tracked each other, so that the
        character repertoires and code point assignments have
        remained in sync.  The relevant standardization committees
        have committed to maintain this very useful synchronism.

15.3.  Difficulties with UCS-4, UCS-2, Unicode

   Adapting existing applications, and file systems to multi-octet
   schemes like UCS and Unicode can be difficult. A significant amount
   of code has been written to process streams of bytes. Also there are
   many existing stored objects described with 7 bit or 8 bit
   characters. Doubling or quadrupling the bandwidth and storage
   requirements seems like an expensive way to accomplish I18N.

   UCS-2 and Unicode are "only" 16 bits long. That might seem to be
   enough but, according to [Unicode1], 38,887 Unicode characters are
   already assigned. And according to [Unicode2] there are still more
   languages that need to be added.

Expires: March 2000                                           [Page 170]


Draft Protocol Specification  NFS version 4               September 1999

15.4.  UTF-8 and its solutions

   UTF-8 solves problems for NFS that exist with the use of UCS and
   Unicode.  UTF-8 will encode 16 bit and 32 bit characters in a way
   that will be compact for most users. The encoding table from UCS-4 to
   UTF-8, as copied from [RFC2279]:

      UCS-4 range (hex.)           UTF-8 octet sequence (binary)
    0000 0000-0000 007F   0xxxxxxx
    0000 0080-0000 07FF   110xxxxx 10xxxxxx
    0000 0800-0000 FFFF   1110xxxx 10xxxxxx 10xxxxxx

    0001 0000-001F FFFF   11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
    0020 0000-03FF FFFF   111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
    0400 0000-7FFF FFFF   1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
   10xxxxxx

   See [RFC2279] for precise encoding and decoding rules. Note because
   of UTF-16, the algorithm from Unicode/UCS-2 to UTF-8 needs to account
   for the reserved range between D800 and DFFF.

   Note that the 16 bit UCS or Unicode characters require no more than 3
   octets to encode into UTF-8

   Interestingly, UTF-8 has room to handle characters larger than 31
   bits, because the leading octet of form:

           1111111x

   is not defined. If needed, ISO could either use that octet to
   indicate a sequence of an encoded 8 octet character, or perhaps use
   11111110 to permit the next octet to indicate an even more expandable
   character set.

   So using UTF-8 to represent character encodings means never having to
   run out of room.

Expires: March 2000                                           [Page 171]


Draft Protocol Specification  NFS version 4               September 1999

16.  Security Considerations

   The major security feature to consider is the authentication of the
   user making the request of NFS service.  Consideration should also be
   given to the integrity and privacy of this NFS request.  These
   specific issues are discussed as part of the section on "RPC and
   Security Flavor".

   As this document progresses, other issues of denial of service and
   other typical security issues will be addressed here along with those
   issues specific to NFS service.

Expires: March 2000                                           [Page 172]


Draft Protocol Specification  NFS version 4               September 1999

17.  NFS Version 4 RPC definition file

   /*
    *      nfs_prot.x
    *
    */

   %#pragma ident  "@(#)nfs4_prot.x        1.48    99/09/05"

   /*
    * Sizes
    */
   const NFS4_FHSIZE         = 128;
   const NFS4_CREATEVERFSIZE = 8;

   /*
    * Timeval
    */
   struct nfstime4 {
           int64_t         seconds;
           uint32_t        nseconds;
   };

   struct specdata4 {
           uint32_t        specdata1;
           uint32_t        specdata2;
   };

   typedef uint32_t        bitmap4<>;

   /*
    * Basic data types
    */
   typedef opaque          utf8string<>;
   typedef uint64_t        offset4;
   typedef uint32_t        count4;
   typedef uint32_t        length4;
   typedef uint64_t        clientid4;
   typedef uint64_t        stateid4;
   typedef uint32_t        seqid4;
   typedef uint32_t        writeverf4;
   typedef opaque          createverf4[NFS4_CREATEVERFSIZE];
   typedef utf8string      component4;
   typedef component4      pathname4<>;
   typedef uint64_t        nfs_lockid4;
   typedef uint32_t        nfs_lease4;
   typedef uint32_t        nfs_lockstate4;
   typedef uint64_t        nfs_cookie4;

Expires: March 2000                                           [Page 173]


Draft Protocol Specification  NFS version 4               September 1999

   typedef utf8string      linktext4;
   typedef opaque          sec_oid4<>;
   typedef uint32_t        qop4;

   /*
    * File attributes
    */

   /*
    * FSID structure for major/minor
    */
   struct fsid4 {
           uint64_t        major;
           uint64_t        minor;
   };

   /*
    * Filesystem locations attribute for relocation/migration
    */
   struct fs_location {
           utf8string      server<>;
           pathname4       rootpath;
   };

   struct fs_locations {
           pathname4       fs_root;
           fs_location     locations<>;
   };

   typedef uint32_t        fattr4_type;
   typedef bool            fattr4_persistent_fh;
   typedef uint64_t        fattr4_change;
   typedef uint64_t        fattr4_size;
   typedef bool            fattr4_link_support;
   typedef bool            fattr4_symlink_support;
   typedef bool            fattr4_named_attr;
   typedef fsid4           fattr4_fsid;
   typedef bool            fattr4_unique_handles;
   typedef uint32_t        fattr4_lease_time;

   typedef bool            fattr4_archive;
   typedef bool            fattr4_cansettime;
   typedef bool            fattr4_case_insensitive;
   typedef bool            fattr4_case_preserving;
   typedef bool            fattr4_chown_restricted;
   typedef uint64_t        fattr4_fileid;
   typedef uint64_t        fattr4_files_avail;

Expires: March 2000                                           [Page 174]


Draft Protocol Specification  NFS version 4               September 1999

   typedef uint64_t        fattr4_files_free;
   typedef uint64_t        fattr4_files_total;
   typedef fs_locations    fattr4_fs_locations;
   typedef bool            fattr4_hidden;
   typedef bool            fattr4_homogenous;
   typedef uint64_t        fattr4_maxfilesize;
   typedef uint32_t        fattr4_maxlink;
   typedef uint32_t        fattr4_maxname;
   typedef uint64_t        fattr4_maxread;
   typedef uint64_t        fattr4_maxwrite;
   typedef utf8string      fattr4_mimetype;
   typedef uint32_t        fattr4_mode;
   typedef bool            fattr4_no_trunc;
   typedef uint32_t        fattr4_numlinks;
   typedef utf8string      fattr4_owner;
   typedef utf8string      fattr4_owner_group;
   typedef uint64_t        fattr4_quota_hard;
   typedef uint64_t        fattr4_quota_soft;
   typedef uint64_t        fattr4_quota_used;
   typedef specdata4       fattr4_rawdev;
   typedef uint64_t        fattr4_space_avail;
   typedef uint64_t        fattr4_space_free;
   typedef uint64_t        fattr4_space_total;
   typedef uint64_t        fattr4_space_used;
   typedef bool            fattr4_system;
   typedef nfstime4        fattr4_time_access;
   typedef nfstime4        fattr4_time_backup;
   typedef nfstime4        fattr4_time_create;
   typedef nfstime4        fattr4_time_delta;
   typedef nfstime4        fattr4_time_metadata;
   typedef nfstime4        fattr4_time_modify;
   typedef utf8string      fattr4_version;
   typedef nfstime4        fattr4_volatility;

   /*
    * nfsacl4 - attribute
    * NOTE: This is meant to be very temporary; definition will change
    */
   struct nfsacl4 {
           utf8string      user;   /* owning user */
           utf8string      group;  /* owning group */
           fattr4_mode     mode;   /* Unix-style mode bits */
   };

   /*
    * Error status
    */
   enum nfsstat4 {

Expires: March 2000                                           [Page 175]


Draft Protocol Specification  NFS version 4               September 1999

           NFS4_OK                 = 0,
           NFS4ERR_PERM            = 1,
           NFS4ERR_NOENT           = 2,
           NFS4ERR_IO              = 5,
           NFS4ERR_NXIO            = 6,
           NFS4ERR_ACCES           = 13,
           NFS4ERR_EXIST           = 17,
           NFS4ERR_XDEV            = 18,
           NFS4ERR_NODEV           = 19,
           NFS4ERR_NOTDIR          = 20,
           NFS4ERR_ISDIR           = 21,
           NFS4ERR_INVAL           = 22,
           NFS4ERR_FBIG            = 27,
           NFS4ERR_NOSPC           = 28,
           NFS4ERR_ROFS            = 30,
           NFS4ERR_MLINK           = 31,
           NFS4ERR_NAMETOOLONG     = 63,
           NFS4ERR_NOTEMPTY        = 66,
           NFS4ERR_DQUOT           = 69,
           NFS4ERR_STALE           = 70,
           NFS4ERR_BADHANDLE       = 10001,
           NFS4ERR_NOT_SYNC        = 10002,
           NFS4ERR_BAD_COOKIE      = 10003,
           NFS4ERR_NOTSUPP         = 10004,
           NFS4ERR_TOOSMALL        = 10005,
           NFS4ERR_SERVERFAULT     = 10006,
           NFS4ERR_BADTYPE         = 10007,
           NFS4ERR_JUKEBOX         = 10008,
           NFS4ERR_SAME            = 10009,/* nverify says attrs same */
           NFS4ERR_DENIED          = 10010,/* lock unavailable */
           NFS4ERR_EXPIRED         = 10011,/* lock lease expired */
           NFS4ERR_LOCKED          = 10012,/* I/O failed due to lock */
           NFS4ERR_GRACE           = 10013,/* in grace period */
           NFS4ERR_FHEXPIRED       = 10014,/* file handle expired */
           NFS4ERR_SHARE_DENIED    = 10015,/* share reserve denied */
           NFS4ERR_WRONGSEC        = 10016,/* wrong security flavor */
           NFS4ERR_CLID_INUSE      = 10017,/* clientid in use */
           NFS4ERR_RESOURCE        = 10018,/* resource exhaustion */
           NFS4ERR_MOVED           = 10019,/* filesystem relocated */
           NFS4ERR_NOFILEHANDLE    = 10020 /* current FH is not set */
   };

   /*
    * From RFC 2203
    */
   enum rpc_gss_svc_t {
           RPC_GSS_SVC_NONE        = 1,
           RPC_GSS_SVC_INTEGRITY   = 2,

Expires: March 2000                                           [Page 176]


Draft Protocol Specification  NFS version 4               September 1999

           RPC_GSS_SVC_PRIVACY     = 3
   };

   /*
    * File access handle
    */
   typedef opaque  nfs_fh4<NFS4_FHSIZE>;

   /*
    * File types
    */
   enum nfs_ftype4 {
           NF4REG          = 1,    /* Regular File */
           NF4DIR          = 2,    /* Directory */
           NF4BLK          = 3,    /* Special File - block device */
           NF4CHR          = 4,    /* Special File - character device */
           NF4LNK          = 5,    /* Symbolic Link */
           NF4SOCK         = 6,    /* Special File - socket */
           NF4FIFO         = 7,    /* Special File - fifo */
           NF4ATTRDIR      = 8,    /* Attribute Directory */
           NF4NAMEDATTR    = 9     /* Named Attribute */
   };

   /*
    * Mandatory Attributes
    */
   const FATTR4_SUPPORTED_ATTRS    = 0;
   const FATTR4_TYPE               = 1;
   const FATTR4_PERSISTENT_FH      = 2;
   const FATTR4_CHANGE             = 3;
   const FATTR4_SIZE               = 4;
   const FATTR4_LINK_SUPPORT       = 5;
   const FATTR4_SYMLINK_SUPPORT    = 6;
   const FATTR4_NAMED_ATTR         = 7;
   const FATTR4_FSID               = 8;
   const FATTR4_UNIQUE_HANDLES     = 9;
   const FATTR4_LEASE_TIME         = 10;

   /*
    * Recommended Attributes
    */
   const FATTR4_ACL                = 11;
   const FATTR4_ARCHIVE            = 12;
   const FATTR4_CANSETTIME         = 13;
   const FATTR4_CASE_INSENSITIVE   = 14;
   const FATTR4_CASE_PRESERVING    = 15;
   const FATTR4_CHOWN_RESTRICTED   = 16;
   const FATTR4_FILEHANDLE         = 17;

Expires: March 2000                                           [Page 177]


Draft Protocol Specification  NFS version 4               September 1999

   const FATTR4_FILEID             = 18;
   const FATTR4_FILES_AVAIL        = 19;
   const FATTR4_FILES_FREE         = 20;
   const FATTR4_FILES_TOTAL        = 21;
   const FATTR4_FS_LOCATIONS       = 22;
   const FATTR4_HIDDEN             = 23;
   const FATTR4_HOMOGENEOUS        = 24;
   const FATTR4_MAXFILESIZE        = 25;
   const FATTR4_MAXLINK            = 26;
   const FATTR4_MAXNAME            = 27;
   const FATTR4_MAXREAD            = 28;
   const FATTR4_MAXWRITE           = 29;
   const FATTR4_MIME_TYPE          = 30;
   const FATTR4_MODE               = 31;
   const FATTR4_NO_TRUNC           = 32;
   const FATTR4_NUMLINKS           = 33;
   const FATTR4_OWNER              = 34;
   const FATTR4_OWNER_GROUP        = 35;
   const FATTR4_QUOTA_HARD         = 36;
   const FATTR4_QUOTA_SOFT         = 37;
   const FATTR4_QUOTA_USED         = 38;
   const FATTR4_RAWDEV             = 39;
   const FATTR4_SPACE_AVAIL        = 40;
   const FATTR4_SPACE_FREE         = 41;
   const FATTR4_SPACE_TOTAL        = 42;
   const FATTR4_SPACE_USED         = 43;
   const FATTR4_SYSTEM             = 44;
   const FATTR4_TIME_ACCESS        = 45;
   const FATTR4_TIME_BACKUP        = 46;
   const FATTR4_TIME_CREATE        = 47;
   const FATTR4_TIME_DELTA         = 48;
   const FATTR4_TIME_METADATA      = 49;
   const FATTR4_TIME_MODIFY        = 50;
   const FATTR4_VERSION            = 51;
   const FATTR4_VOLATILITY         = 52;

   typedef opaque  attrlist<>;

   struct fattr4 {
           bitmap4         attrmask;
           attrlist        attr_vals;
   };

   /*
    * Change info for the client
    */
   struct change_info4 {

Expires: March 2000                                           [Page 178]


Draft Protocol Specification  NFS version 4               September 1999

           bool            atomic;
           fattr4_change   before;
           fattr4_change   after;
   };

   struct clientaddr4 {
           /* see struct rpcb in RFC 1833 */
           string r_netid;         /* network id */
           string r_addr;          /* universal address */
   };

   /*
    * Callback program info as provided by the client
    */
   struct cb_client4 {
           unsigned int    program;
           clientaddr4     cb_location;
   };

   /*
    * Client ID
    */
   struct cid {
           opaque          verifier[4];
           opaque          id<>;
   };

   union nfs_client_id switch (clientid4 clientid) {
    case 0:
            cid            ident;
    default:
            void;
   };

   struct nfs_lockowner {
           clientid4       clientid;
           opaque          owner<>;
   };

   enum nfs_lock_type4 {
           READ_LT         = 1,
           WRITE_LT        = 2,
           READW_LT        = 3,    /* blocking read */
           WRITEW_LT       = 4     /* blocking write */
   };

   /*
    * ACCESS: Check access permission

Expires: March 2000                                           [Page 179]


Draft Protocol Specification  NFS version 4               September 1999

    */
   const ACCESS4_READ      = 0x0001;
   const ACCESS4_LOOKUP    = 0x0002;
   const ACCESS4_MODIFY    = 0x0004;
   const ACCESS4_EXTEND    = 0x0008;
   const ACCESS4_DELETE    = 0x0010;
   const ACCESS4_EXECUTE   = 0x0020;

   struct ACCESS4args {
           /* CURRENT_FH: object */
           uint32_t        access;
   };

   struct ACCESS4resok {
           uint32_t        supported;
           uint32_t        access;
   };

   union ACCESS4res switch (nfsstat4 status) {
    case NFS4_OK:
            ACCESS4resok   resok4;
    default:
            void;
   };

   /*
    * COMMIT: Commit cached data on server to stable storage
    */
   struct COMMIT4args {
           /* CURRENT_FH: file */
           offset4         offset;
           count4          count;
   };

   struct COMMIT4resok {
           writeverf4      verf;
   };

   union COMMIT4res switch (nfsstat4 status) {
    case NFS4_OK:
            COMMIT4resok   resok4;
    default:
            void;
   };

   /*
    * CREATE: Create a file

Expires: March 2000                                           [Page 180]


Draft Protocol Specification  NFS version 4               September 1999

    */
   enum createmode4 {
           UNCHECKED4      = 0,
           GUARDED4        = 1,
           EXCLUSIVE4      = 2
   };

   union createhow4 switch (createmode4 mode) {
    case UNCHECKED4:
    case GUARDED4:
            fattr4         createattrs;
    case EXCLUSIVE4:
            createverf4    verf;
   };

   enum opentype4 {
           OPEN4_NOCREATE  = 0,
           OPEN4_CREATE    = 1
   };

   union openflag switch (opentype4 opentype) {
    case OPEN4_CREATE:
            createhow4     how;
    default:
            void;
   };

   /*
    * LOCK/LOCKT/LOCKU: Record lock management
    */
   struct LOCK4args {
           /* CURRENT_FH: file */
           nfs_lock_type4  type;
           seqid4          seqid;
           bool            reclaim;
           stateid4        stateid;
           offset4         offset;
           length4         length;
   };

   struct lockres {
           stateid4        stateid;
           int32_t         access;
   };

   union LOCK4res switch (nfsstat4 status) {
    case NFS4_OK:
            lockres        result;

Expires: March 2000                                           [Page 181]


Draft Protocol Specification  NFS version 4               September 1999

    default:
            void;
   };

   union LOCKT4res switch (nfsstat4 status) {
    case NFS4ERR_DENIED:
            nfs_lockowner  owner;
    case NFS4_OK:
            void;
    default:
            void;
   };

   union LOCKU4res switch (nfsstat4 status) {
    case   NFS4_OK:
            stateid4       stateid_ok;
    default:
            stateid4       stateid_oth;
   };

   /*
    * SETCLIENTID
    */
   struct SETCLIENTID4args {
           seqid4          seqid;
           nfs_client_id   client;
           cb_client4      callback;
   };

   union SETCLIENTID4res switch (nfsstat4 status) {
    case NFS4_OK:
            clientid4      clientid;
    case NFS4ERR_CLID_INUSE:
            clientaddr4    client_using;
    default:
            void;
   };

   /*
    * Various definitions for OPEN
    */
   enum limit_by4 {
           NFS_LIMIT_SIZE          = 1,
           NFS_LIMIT_BLOCKS        = 2 /* experimental;
                                          subject to change*/
           /* others as needed */
   };

Expires: March 2000                                           [Page 182]


Draft Protocol Specification  NFS version 4               September 1999

   struct nfs_modified_limit4 {
           uint64_t        bytes;
           uint32_t        blocksize;
   };

   union nfs_space_limit4 switch (limit_by4 limitby) {
    case NFS_LIMIT_SIZE:
            uint64_t               filesize;
    case NFS_LIMIT_BLOCKS:
            nfs_modified_limit4    mod_blocks;
   } ;

   /*
    * Access and Deny constants for open argument
    */
   const OPEN4_ACCESS_READ = 0x0001;
   const OPEN4_ACCESS_WRITE= 0x0002;
   const OPEN4_ACCESS_BOTH = 0x0003;

   const OPEN4_DENY_NONE   = 0x0000;
   const OPEN4_DENY_READ   = 0x0001;
   const OPEN4_DENY_WRITE  = 0x0002;
   const OPEN4_DENY_BOTH   = 0x0003;

   enum open_delegation_type4 {
           OPEN_DELEGATE_NONE      = 0,
           OPEN_DELEGATE_READ      = 1,
           OPEN_DELEGATE_WRITE     = 2
   };

   enum open_claim_type4 {
           CLAIM_NULL              = 0,
           CLAIM_PREVIOUS          = 1,
           CLAIM_DELEGATE_CUR      = 2,
           CLAIM_DELEGATE_PREV     = 3
   };

   struct open_claim_delegate_cur {
           pathname4       file;
           stateid4        delegate_stateid;
   };

   union open_claim4 switch (open_claim_type4 claim) {
    /*
     * No special rights to file. Ordinary OPEN of the specified file.
     */
    case CLAIM_NULL:
            /* CURRENT_FH: directory */

Expires: March 2000                                           [Page 183]


Draft Protocol Specification  NFS version 4               September 1999

            pathname4      file;

    /*
     * Right to the file established by an open previous to server
     * reboot.  File identified by filehandle obtained at that time
     * rather than by name.
     */
    case CLAIM_PREVIOUS:
            /* CURRENT_FH: file being reclaimed */
            int32_t        delegate_type;

    /*
     * Right to file based on a delegation granted by the server.
     * File is specified by name.
     */
    case CLAIM_DELEGATE_CUR:
            /* CURRENT_FH: directory */
            open_claim_delegate_cur        delegate_cur_info;

    /* Right to file based on a delegation granted to a previous boot
     * instance of the client.  File is specified by name.
     */
    case CLAIM_DELEGATE_PREV:
            /* CURRENT_FH: directory */
            pathname4      file_delegate_prev;
   };

   /*
    * OPEN: Open a file, potentially receiving an open delegation
    */
   struct OPEN4args {
           open_claim4     claim;
           openflag        openhow;
           nfs_lockowner   owner;
           seqid4          seqid;
           int32_t         access;
           int32_t         deny;
   };

   /*
    * Result flags
    */
   /* Mandatory locking is in effect for this file. */
   const OPEN4_RESULT_MLOCK        = 0x0001;

   struct open_read_delegation4 {
           stateid4        stateid;        /* Stateid for delegation*/
           bool            recall;         /* Pre-recalled flag for

Expires: March 2000                                           [Page 184]


Draft Protocol Specification  NFS version 4               September 1999

                                              delegations obtained
                                              by reclaim
                                              (CLAIM_PREVIOUS) */
           nfsacl4         permissions;    /* Defines users who don't
                                              need an ACCESS call to
                                              open for read */
   };

   struct open_write_delegation4 {
           stateid4        stateid;        /* Stateid for delegation
                                              be flushed to the server
                                              on close. */
           bool            recall;         /* Pre-recalled flag for
                                              delegations obtained
                                              by reclaim
                                              (CLAIM_PREVIOUS) */
           nfs_space_limit4 space_limit;   /* Defines condition that
                                              the client must check to
                                              determine whether the
                                              file needs to be flushed
                                              to the server on close.
                                              */
           nfsacl4         permissions;    /* Defines users who don't
                                              need an ACCESS call as
                                              part of a delegated
                                              open. */
   };

   union open_delegation4
   switch (open_delegation_type4 delegation_type) {
           case OPEN_DELEGATE_NONE:
                   void;
           case OPEN_DELEGATE_READ:
                   open_read_delegation4 read;
           case OPEN_DELEGATE_WRITE:
                   open_write_delegation4 write;
   };

   struct OPEN4resok {
           stateid4        stateid;        /* Stateid for open */
           uint32_t        rflags;         /* Result flags */
           int32_t         access;         /* Access granted */
           open_delegation4 delegation;    /* Info on any open
                                              delegation */
   };

   union OPEN4res switch (nfsstat4 status) {
    case NFS4_OK:

Expires: March 2000                                           [Page 185]


Draft Protocol Specification  NFS version 4               September 1999

           /* CURRENT_FH: opened file */
           OPEN4resok      result;
    default:
           void;
   };

   /*
    * CREATE: Create special file
    */
   struct CREATE4args {
           /* CURRENT_FH: directory for creation */
           component4      objname;
           fattr4_type     type;
           createhow4      createhow;
   };

   struct CREATE4resok {
           change_info4     cinfo;
   };

   union CREATE4res switch (nfsstat4 status) {
    case NFS4_OK:
            CREATE4resok resok4;
    default:
            void;
   };

   /*
    * CLOSE: Close a file and release share locks
    */
   struct CLOSE4args {
           stateid4        stateid;
   };

   union CLOSE4res switch (nfsstat4 status) {
    case NFS4_OK:
            stateid4       stateid;
    default:
            void;
   };

   /*
    * GETATTR: Get file attributes
    */
   struct GETATTR4args {
           /* CURRENT_FH: directory or file */
           bitmap4         attr_request;
   };

Expires: March 2000                                           [Page 186]


Draft Protocol Specification  NFS version 4               September 1999

   struct GETATTR4resok {
           fattr4          obj_attributes;
   };

   union GETATTR4res switch (nfsstat4 status) {
    case NFS4_OK:
            GETATTR4resok  resok4;
    default:
            void;
   };

   /*
    * DELEGRETURN: Return a delegation
    */
   struct DELEGRETURN4args {
           stateid4        stateid;
   };

   struct DELEGRETURN4res {
           nfsstat4        status;
   };

   /*
    * DELEGPURGE: Purge Delegations Awaiting Recovery
    */
   struct DELEGPURGE4args {
           clientid4       clientid;
   };

   struct DELEGPURGE4res {
           nfsstat4        status;
   };

   /*
    * OPENATTR: open named attributes directory
    */
   struct OPENATTR4res {
           /* CURRENT_FH: name attr directory*/
           nfsstat4        status;
   };

   /*
    * GETFH: Get current filehandle
    */
   struct GETFH4resok {
           nfs_fh4         object;
   };

Expires: March 2000                                           [Page 187]


Draft Protocol Specification  NFS version 4               September 1999

   union GETFH4res switch (nfsstat4 status) {
    case NFS4_OK:
            GETFH4resok    resok4;
    default:
            void;
   };

   /*
    * LINK: Create link to an object
    */
   struct LINK4args {
           /* CURRENT_FH: file */
           nfs_fh4         dir;
           component4      newname;
   };

   struct LINK4resok {
           change_info4    cinfo;
   };

   union LINK4res switch (nfsstat4 status) {
    case NFS4_OK:
            LINK4resok resok4;
    default:
            void;
   };

   /*
    * LOOKUP: Lookup filename
    */
   struct LOOKUP4args {
           /* CURRENT_FH: directory */
           pathname4       path;
   };

   struct LOOKUP4res {
           /* CURRENT_FH: object */
           nfsstat4        status;
   };

   /*
    * LOOKUPP: Lookup parent directory
    */
   struct LOOKUPP4res {
           /* CURRENT_FH: directory */
           nfsstat4        status;
   };

Expires: March 2000                                           [Page 188]


Draft Protocol Specification  NFS version 4               September 1999

   /*
    * NVERIFY: Verify attributes different
    */
   struct NVERIFY4args {
           /* CURRENT_FH: object */
           bitmap4         attr_request;
           fattr4          obj_attributes;
   };

   struct NVERIFY4res {
           nfsstat4        status;
   };

   /*
    * RESTOREFH: Restore saved filehandle
    */

   struct RESTOREFH4res {
           /* CURRENT_FH: value of saved fh */
           nfsstat4        status;
   };

   /*
    * SAVEFH: Save current filehandle
    */
   struct SAVEFH4res {
           /* SAVED_FH: value of current fh */
           nfsstat4        status;
   };

   /*
    * PUTFH: Set current filehandle
    */
   struct PUTFH4args {
           nfs_fh4         object;
   };

   struct PUTFH4res {
           /* CURRENT_FH: */
           nfsstat4        status;
   };

   /*
    * PUTROOTFH: Set root filehandle
    */
   struct PUTROOTFH4res {
           /* CURRENT_FH: root fh */
           nfsstat4        status;

Expires: March 2000                                           [Page 189]


Draft Protocol Specification  NFS version 4               September 1999

   };

   /*
    * PUTPUBFH: Set public filehandle
    */
   struct PUTPUBFH4res {
           /* CURRENT_FH: public fh */
           nfsstat4        status;
   };

   /*
    * READ: Read from file
    */
   struct READ4args {
           /* CURRENT_FH: file */
           stateid4        stateid;
           offset4         offset;
           count4          count;
   };

   struct READ4resok {
           bool            eof;
           opaque          data<>;
   };

   union READ4res switch (nfsstat4 status) {
    case NFS4_OK:
            READ4resok     resok4;
    default:
            void;
   };

   /*
    * READDIR: Read directory
    */
   struct READDIR4args {
           /* CURRENT_FH: directory */
           nfs_cookie4     cookie;
           count4          dircount;
           count4          maxcount;
           bitmap4         attr_request;

   };

   struct entry4 {
           nfs_cookie4     cookie;
           component4      name;
           fattr4          attrs;

Expires: March 2000                                           [Page 190]


Draft Protocol Specification  NFS version 4               September 1999

           entry4          *nextentry;
   };

   struct dirlist4 {
           entry4          *entries;
           bool            eof;
   };

   struct READDIR4resok {
           dirlist4        reply;
   };

   union READDIR4res switch (nfsstat4 status) {
    case NFS4_OK:
            READDIR4resok  resok4;
    default:
            void;
   };

   /*
    * READLINK: Read symbolic link
    */
   struct READLINK4resok {
           linktext4       link;
   };

   union READLINK4res switch (nfsstat4 status) {
    case NFS4_OK:
            READLINK4resok resok4;
    default:
            void;
   };

   /*
    * REMOVE: Remove filesystem object
    */
   struct REMOVE4args {
           /* CURRENT_FH: directory */
           component4      target;
   };

   struct REMOVE4resok {
           change_info4    cinfo;
   };

   union REMOVE4res switch (nfsstat4 status) {

Expires: March 2000                                           [Page 191]


Draft Protocol Specification  NFS version 4               September 1999

    case NFS4_OK:
            REMOVE4resok   resok4;
    default:
            void;
   };

   /*
    * RENAME: Rename directory entry
    */
   struct RENAME4args {
           /* CURRENT_FH: source directory */
           component4      oldname;
           nfs_fh4         newdir;
           component4      newname;
   };

   struct RENAME4resok {
           change_info4    source_cinfo;
           change_info4    target_cinfo;
   };

   union RENAME4res switch (nfsstat4 status) {
    case NFS4_OK:
            RENAME4resok   resok4;
    default:
            void;
   };

   /*
    * RENEW: Renew a Lease
    */
   struct RENEW4args {
           stateid4        stateid;
   };

   struct RENEW4res {
           nfsstat4        status;
   };

   /*
    * SETATTR: Set attributes
    */
   struct SETATTR4args {
           /* CURRENT_FH: target object */
           stateid4        stateid;
           fattr4          obj_attributes;
   };

Expires: March 2000                                           [Page 192]


Draft Protocol Specification  NFS version 4               September 1999

   struct SETATTR4res {
           nfsstat4        status;
   };

   /*
    * VERIFY: Verify attributes same
    */
   struct VERIFY4args {
           /* CURRENT_FH: object */
           bitmap4         attr_request;
           fattr4          obj_attributes;
   };

   struct VERIFY4res {
           nfsstat4        status;
   };

   /*
    * WRITE: Write to file
    */
   enum stable_how4 {
           UNSTABLE4       = 0,
           DATA_SYNC4      = 1,
           FILE_SYNC4      = 2
   };

   struct WRITE4args {
           /* CURRENT_FH: file */
           stateid4        stateid;
           offset4         offset;
           count4          count;
           stable_how4     stable;
           opaque          data<>;
   };

   struct WRITE4resok {
           count4          count;
           stable_how4     committed;
           writeverf4      verf;
   };

   union WRITE4res switch (nfsstat4 status) {
    case NFS4_OK:
            WRITE4resok    resok4;
    default:
            void;
   };

Expires: March 2000                                           [Page 193]


Draft Protocol Specification  NFS version 4               September 1999

   /*
    * SECINFO: Obtain Available Security Mechanisms
    */
   struct SECINFO4args {
           /* CURRENT_FH: */
           component4      name;
   };

   struct rpcsec_gss_info {
           sec_oid4 oid;
           qop4 qop;
           rpc_gss_svc_t service;
   };

   struct secinfo4 {
           unsigned int flavor;
           opaque flavor_info<>;   /* null for AUTH_SYS, AUTH_NONE;
                                      contains rpcsec_gss_info for
                                      RPCSEC_GSS. */
   };

   typedef secinfo4 SECINFO4resok<>;

   union SECINFO4res switch (nfsstat4 status) {
    case NFS4_OK:
            SECINFO4resok resok4;
    default:
            void;
   };

   enum opcode {
           OP_ACCESS               = 2,
           OP_CLOSE                = 3,
           OP_COMMIT               = 4,
           OP_CREATE               = 5,
           OP_DELEGPURGE           = 6,
           OP_DELEGRETURN          = 7,
           OP_GETATTR              = 8,
           OP_GETFH                = 9,
           OP_LINK                 = 10,
           OP_LOCK                 = 11,
           OP_LOCKT                = 12,
           OP_LOCKU                = 13,
           OP_LOOKUP               = 14,
           OP_LOOKUPP              = 15,
           OP_NVERIFY              = 16,
           OP_OPEN                 = 17,

Expires: March 2000                                           [Page 194]


Draft Protocol Specification  NFS version 4               September 1999

           OP_OPENATTR             = 18,
           OP_PUTFH                = 19,
           OP_PUTPUBFH             = 20,
           OP_PUTROOTFH            = 21,
           OP_READ                 = 22,
           OP_READDIR              = 23,
           OP_READLINK             = 24,
           OP_REMOVE               = 25,
           OP_RENAME               = 26,
           OP_RENEW                = 27,
           OP_RESTOREFH            = 28,
           OP_SAVEFH               = 29,
           OP_SECINFO              = 30,
           OP_SETATTR              = 31,
           OP_SETCLIENTID          = 32,
           OP_VERIFY               = 33,
           OP_WRITE                = 34
   };

   union opunion switch (unsigned opcode) {
    case OP_ACCESS:        ACCESS4args opaccess;
    case OP_CLOSE:         CLOSE4args opclose;
    case OP_COMMIT:        COMMIT4args opcommit;
    case OP_CREATE:        CREATE4args opcreate;
    case OP_DELEGPURGE:    DELEGPURGE4args opdelegpurge;
    case OP_DELEGRETURN:   DELEGRETURN4args opdelegreturn;
    case OP_GETATTR:       GETATTR4args opgetattr;
    case OP_GETFH:         void;
    case OP_LINK:          LINK4args oplink;
    case OP_LOCK:          LOCK4args oplock;
    case OP_LOCKT:         LOCK4args oplockt;
    case OP_LOCKU:         LOCK4args oplocku;
    case OP_LOOKUP:        LOOKUP4args oplookup;
    case OP_LOOKUPP:       void;
    case OP_NVERIFY:       NVERIFY4args opnverify;
    case OP_OPEN:          OPEN4args opopen;
    case OP_OPENATTR:      void;
    case OP_PUTFH:         PUTFH4args opputfh;
    case OP_PUTPUBFH:      void;
    case OP_PUTROOTFH:     void;
    case OP_READ:          READ4args opread;
    case OP_READDIR:       READDIR4args opreaddir;
    case OP_READLINK:      void;
    case OP_REMOVE:        REMOVE4args opremove;
    case OP_RENAME:        RENAME4args oprename;
    case OP_RENEW:         RENEW4args oprenew;
    case OP_RESTOREFH:     void;
    case OP_SAVEFH:        void;

Expires: March 2000                                           [Page 195]


Draft Protocol Specification  NFS version 4               September 1999

    case OP_SECINFO:       SECINFO4args opsecinfo;
    case OP_SETATTR:       SETATTR4args opsetattr;
    case OP_SETCLIENTID:   SETCLIENTID4args opsetclientid;
    case OP_VERIFY:        VERIFY4args opverify;
    case OP_WRITE:         WRITE4args opwrite;
   };

   struct op {
           opunion         ops;
   };

   union resultdata switch (unsigned resop){
    case OP_ACCESS:        ACCESS4res opaccess;
    case OP_CLOSE:         CLOSE4res opclose;
    case OP_COMMIT:        COMMIT4res opcommit;
    case OP_CREATE:        CREATE4res opcreate;
    case OP_DELEGPURGE:    DELEGPURGE4res opdelegpurge;
    case OP_DELEGRETURN:   DELEGRETURN4res opdelegreturn;
    case OP_GETATTR:       GETATTR4res opgetattr;
    case OP_GETFH:         GETFH4res opgetfh;
    case OP_LINK:          LINK4res oplink;
    case OP_LOCK:          LOCK4res oplock;
    case OP_LOCKT:         LOCKT4res oplockt;
    case OP_LOCKU:         LOCKU4res oplocku;
    case OP_LOOKUP:        LOOKUP4res oplookup;
    case OP_LOOKUPP:       LOOKUPP4res oplookupp;
    case OP_NVERIFY:       NVERIFY4res opnverify;
    case OP_OPEN:          OPEN4res opopen;
    case OP_OPENATTR:      OPENATTR4res opopenattr;
    case OP_PUTFH:         PUTFH4res opputfh;
    case OP_PUTPUBFH:      PUTPUBFH4res opputpubfh;
    case OP_PUTROOTFH:     PUTROOTFH4res opputrootfh;
    case OP_READ:          READ4res opread;
    case OP_READDIR:       READDIR4res opreaddir;
    case OP_READLINK:      READLINK4res opreadlink;
    case OP_REMOVE:        REMOVE4res opremove;
    case OP_RENAME:        RENAME4res oprename;
    case OP_RENEW:         RENEW4res oprenew;
    case OP_RESTOREFH:     RESTOREFH4res oprestorefh;
    case OP_SAVEFH:        SAVEFH4res opsavefh;
    case OP_SECINFO:       SECINFO4res opsecinfo;
    case OP_SETATTR:       SETATTR4res opsetattr;
    case OP_SETCLIENTID:   SETCLIENTID4res opsetclientid;
    case OP_VERIFY:        VERIFY4res opverify;
    case OP_WRITE:         WRITE4res opwrite;
   };

   struct COMPOUND4args {

Expires: March 2000                                           [Page 196]


Draft Protocol Specification  NFS version 4               September 1999

           utf8string      tag;
           op              oplist<>;
   };

   struct COMPOUND4res {
           nfsstat4 status;
           utf8string      tag;
           resultdata      data<>;
   };

   /*
    * Remote file service routines
    */
   program NFS4_PROGRAM {
           version NFS_V4 {
                   void
                           NFSPROC4_NULL(void) = 0;

                   COMPOUND4res
                           NFSPROC4_COMPOUND(COMPOUND4args) = 1;

           } = 4;
   } = 100003;

   /*
    * NFS4 Callback Procedure Definitions and Program
    */

   /*
    * CB_GETATTR: Get Current Attributes
    */
   struct CB_GETATTR4args {
           nfs_fh4 fh;
           bitmap4 attr_request;
   };

   struct CB_GETATTR4resok {
           fattr4  obj_attributes;
   };

   union CB_GETATTR4res switch (nfsstat4 status) {
    case NFS4_OK:
            CB_GETATTR4resok       resok4;
    default:
            void;
   };

Expires: March 2000                                           [Page 197]


Draft Protocol Specification  NFS version 4               September 1999

   /*
    * CB_RECALL: Recall an Open Delegation
    */
   struct CB_RECALL4args {
           stateid4        stateid;
           bool            truncate;
           nfs_fh4         fh;
   };

   struct CB_RECALL4res {
           nfsstat4        status;
   };

   /*
    * Various definitions for CB_COMPOUND
    */
   enum cb_opcode {
           OP_CB_GETATTR           = 2,
           OP_CB_RECALL            = 3
   };

   union cb_opunion switch (unsigned opcode) {
    case OP_CB_GETATTR:    CB_GETATTR4args opcbgetattr;
    case OP_CB_RECALL:     CB_RECALL4args  opcbrecall;
   };

   struct cb_op {
           cb_opunion      ops;
   };

   union cb_resultdata switch (unsigned resop){
    case OP_CB_GETATTR:    CB_GETATTR4res  opcbgetattr;
    case OP_CB_RECALL:     CB_RECALL4res   opcbrecall;
   };

   struct CB_COMPOUND4args {
           utf8string      tag;
           cb_op           oplist<>;
   };

   struct CB_COMPOUND4res {
           nfsstat4 status;
           utf8string      tag;
           cb_resultdata   data<>;
   };

   /*

Expires: March 2000                                           [Page 198]


Draft Protocol Specification  NFS version 4               September 1999

    * Program number is in the transient range since the client
    * will assign the exact transient program number and provide
    * that to the server via the SETCLIENTID operation.
    */
   program NFS4_CALLBACK {
           version NFS_CB {
                   void
                           CB_NULL(void) = 0;
                   CB_COMPOUND4res
                           CB_COMPOUND(CB_COMPOUND4args) = 1;
           } = 1;
   } = 40000000;

Expires: March 2000                                           [Page 199]


Draft Protocol Specification  NFS version 4               September 1999

18.  Bibliography

   [Gray]
   C. Gray, D. Cheriton, "Leases: An Efficient Fault-Tolerant Mechanism
   for Distributed File Cache Consistency," Proceedings of the Twelfth
   Symposium on Operating Systems Principles, p. 202-210, December 1989.

   [Juszczak]
   Juszczak, Chet, "Improving the Performance and Correctness of an NFS
   Server," USENIX Conference Proceedings, USENIX Association, Berkeley,
   CA, June 1990, pages 53-63.  Describes reply cache implementation
   that avoids work in the server by handling duplicate requests. More
   important, though listed as a side-effect, the reply cache aids in
   the avoidance of destructive non-idempotent operation re-application
   -- improving correctness.

   [Kazar]
   Kazar, Michael Leon, "Synchronization and Caching Issues in the
   Andrew File System," USENIX Conference Proceedings, USENIX
   Association, Berkeley, CA, Dallas Winter 1988, pages 27-36.  A
   description of the cache consistency scheme in AFS.  Contrasted with
   other distributed file systems.

   [Macklem]
   Macklem, Rick, "Lessons Learned Tuning the 4.3BSD Reno Implementation
   of the NFS Protocol," Winter USENIX Conference Proceedings, USENIX
   Association, Berkeley, CA, January 1991.  Describes performance work
   in tuning the 4.3BSD Reno NFS implementation. Describes performance
   improvement (reduced CPU loading) through elimination of data copies.

   [Mogul]
   Mogul, Jeffrey C., "A Recovery Protocol for Spritely NFS," USENIX
   File System Workshop Proceedings, Ann Arbor, MI, USENIX Association,
   Berkeley, CA, May 1992.  Second paper on Spritely NFS proposes a
   lease-based scheme for recovering state of consistency protocol.

   [Nowicki]
   Nowicki, Bill, "Transport Issues in the Network File System," ACM
   SIGCOMM newsletter Computer Communication Review, April 1989.  A
   brief description of the basis for the dynamic retransmission work.

Expires: March 2000                                           [Page 200]


Draft Protocol Specification  NFS version 4               September 1999

   [Pawlowski]
   Pawlowski, Brian, Ron Hixon, Mark Stein, Joseph Tumminaro, "Network
   Computing in the UNIX and IBM Mainframe Environment," Uniforum `89
   Conf.  Proc., (1989) Description of an NFS server implementation for
   IBM's MVS operating system.

   [RFC1094]
   Sun Microsystems, Inc., "NFS: Network File System Protocol
   Specification", RFC1094, March 1989.

   http://www.ietf.org/rfc/rfc1094.txt

   [RFC1345]
   Simonsen, K., "Character Mnemonics & Character Sets", RFC1345,
   Rationel Almen Planlaegning, June 1992.

   http://www.ietf.org/rfc/rfc1345.txt

   [RFC1813]
   Callaghan, B., Pawlowski, B., Staubach, P., "NFS Version 3 Protocol
   Specification", RFC1813, Sun Microsystems, Inc., June 1995.

   http://www.ietf.org/rfc/rfc1813.txt

   [RFC1831]
   Srinivasan, R., "RPC: Remote Procedure Call Protocol Specification
   Version 2", RFC1831, Sun Microsystems, Inc., August 1995.

   http://www.ietf.org/rfc/rfc1831.txt

   [RFC1832]
   Srinivasan, R., "XDR: External Data Representation Standard",
   RFC1832, Sun Microsystems, Inc., August 1995.

   http://www.ietf.org/rfc/rfc1832.txt

   [RFC1833]
   Srinivasan, R., "Binding Protocols for ONC RPC Version 2", RFC1833,
   Sun Microsystems, Inc., August 1995.

   http://www.ietf.org/rfc/rfc1833.txt

Expires: March 2000                                           [Page 201]


Draft Protocol Specification  NFS version 4               September 1999

   [RFC2054]
   Callaghan, B., "WebNFS Client Specification", RFC2054, Sun
   Microsystems, Inc., October 1996

   http://www.ietf.org/rfc/rfc2054.txt

   [RFC2055]
   Callaghan, B., "WebNFS Server Specification", RFC2054, Sun
   Microsystems, Inc., October 1996

   http://www.ietf.org/rfc/rfc2055.txt

   [RFC2078]
   Linn, J., "Generic Security Service Application Program Interface,
   Version 2", RFC2078, OpenVision Technologies, January 1997.

   http://www.ietf.org/rfc/rfc2078.txt

   [RFC2152]
   Goldsmith, D., "UTF-7 A Mail-Safe Transformation Format of Unicode",
   RFC2152, Apple Computer, Inc., May 1997

   http://www.ietf.org/rfc/rfc2152.txt

   [RFC2203]
   Eisler, M., Chiu, A., Ling, L., "RPCSEC_GSS Protocol Specification",
   RFC2203, Sun Microsystems, Inc., August 1995.

   http://www.ietf.org/rfc/rfc2203.txt

   [RFC2279]
   Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC2279,
   Alis Technologies, January 1998.

   http://www.ietf.org/rfc/rfc2279.txt

   [RFC2623]
   Eisler, M., "NFS Version 2 and Version 3 Security Issues and the NFS
   Protocol's Use of RPCSEC_GSS and Kerberos V5", RFC2623, Sun
   Microsystems, June 1999

   http://www.ietf.org/rfc/rfc2623.txt

Expires: March 2000                                           [Page 202]


Draft Protocol Specification  NFS version 4               September 1999

   [RFC2624]
   Shepler, S., "NFS Version 4 Design Considerations", RFC2624, Sun
   Microsystems, June 1999

   http://www.ietf.org/rfc/rfc2624.txt

   [Sandberg]
   Sandberg, R., D. Goldberg, S. Kleiman, D. Walsh, B.  Lyon, "Design
   and Implementation of the Sun Network Filesystem," USENIX Conference
   Proceedings, USENIX Association, Berkeley, CA, Summer 1985.  The
   basic paper describing the SunOS implementation of the NFS version 2
   protocol, and discusses the goals, protocol specification and trade-
   offs.

   [Srinivasan]
   Srinivasan, V., Jeffrey C. Mogul, "Spritely NFS: Implementation and
   Performance of Cache Consistency Protocols", WRL Research Report
   89/5, Digital Equipment Corporation Western Research Laboratory, 100
   Hamilton Ave., Palo Alto, CA, 94301, May 1989.  This paper analyzes
   the effect of applying a Sprite-like consistency protocol applied to
   standard NFS. The issues of recovery in a stateful environment are
   covered in [Mogul].

   [Unicode1]
   "Unicode Technical Report #8 - The Unicode Standard, Version 2.1",
   Unicode, Inc., The Unicode Consortium, P.O. Box 700519, San Jose, CA
   95710-0519 USA, September 1998

   http://www.unicode.org/unicode/reports/tr8.html

   [Unicode2]
   "Unsupported Scripts" Unicode, Inc., The Unicode Consortium, P.O. Box
   700519, San Jose, CA 95710-0519 USA, October 1998

   http://www.unicode.org/unicode/standard/unsupported.html

   [XNFS]
   The Open Group, Protocols for Interworking: XNFS, Version 3W, The
   Open Group, 1010 El Camino Real Suite 380, Menlo Park, CA 94025, ISBN
   1-85912-184-5, February 1998.

   HTML version available: http://www.opengroup.org

Expires: March 2000                                           [Page 203]


Draft Protocol Specification  NFS version 4               September 1999

19.  Authors and Contributors

   General feedback related to this document should be directed to:

        nfsv4-wg@sunroof.eng.sun.com

   or the editor.

19.1.  Contributors

   The following individuals have contributed to the document:

   Carl Beame, beame@bws.com, of Hummingbird Communications Ltd.

19.2.  Editor's Address

   Spencer Shepler
   Sun Microsystems, Inc.
   7808 Moonflower Drive
   Austin, Texas 78750

   Phone: +1 512-349-9376
   E-mail: shepler@eng.sun.com

19.3.  Authors' Addresses

   Brent Callaghan
   Sun Microsystems, Inc.
   901 San Antonio Road
   Palo Alto, CA 94303

   Phone: +1 650-786-5067
   E-mail: brent.callaghan@eng.sun.com

   Mike Eisler
   Sun Microsystems, Inc.
   5565 Wilson Road
   Colorado Springs, CO 80919

   Phone: +1 719-599-9026
   E-mail: mre@eng.sun.com

   Dave Noveck
   Network Appliance
   495 East Java Drive
   Sunnyvale, CA 94089

Expires: March 2000                                           [Page 204]


Draft Protocol Specification  NFS version 4               September 1999

   Phone: +1 781-861-9291
   E-mail: dave.noveck@netapp.com

   David Robinson
   Sun Microsystems, Inc.
   901 San Antonio Road
   Palo Alto, CA 94303

   Phone: +1 650-786-5088
   E-mail: david.robinson@eng.sun.com

   Robert Thurlow
   Sun Microsystems, Inc.
   901 San Antonio Road
   Palo Alto, CA 94303

   Phone: +1 650-786-5096
   E-mail: robert.thurlow@eng.sun.com

Expires: March 2000                                           [Page 205]


Draft Protocol Specification  NFS version 4               September 1999

20.  Full Copyright Statement

   "Copyright (C) The Internet Society (1999).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."

Expires: March 2000                                           [Page 206]