NFS Version 4 Working Group S. Shepler INTERNET-DRAFT B. Callaghan Document: draft-ietf-nfsv4-00.txt M. Eisler D. Robinson R. Thurlow Sun Microsystems June 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: December 1999 [Page 1]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 2]
Draft Protocol Specification NFS version 4 June 1999 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 6 2. RPC and Security Flavor . . . . . . . . . . . . . . . . . . 7 2.1. Ports and Transports . . . . . . . . . . . . . . . . . . . 7 2.2. Security Flavors . . . . . . . . . . . . . . . . . . . . . 7 2.2.1. Security mechanisms for NFS version 4 . . . . . . . . . 7 2.2.1.1. Kerberos V5 as security triple . . . . . . . . . . . . 7 2.2.1.2. <another security triple> . . . . . . . . . . . . . . 8 2.3. Security Negotiation . . . . . . . . . . . . . . . . . . . 8 2.3.1. Security Error . . . . . . . . . . . . . . . . . . . . . 8 2.3.2. SECINFO . . . . . . . . . . . . . . . . . . . . . . . . 9 3. File handles . . . . . . . . . . . . . . . . . . . . . . . 10 3.1. Obtaining the First File Handle . . . . . . . . . . . . 10 3.1.1. Root File Handle . . . . . . . . . . . . . . . . . . . 10 3.1.2. Public File Handle . . . . . . . . . . . . . . . . . . 11 3.2. File Handle Types . . . . . . . . . . . . . . . . . . . 11 3.2.1. General Properties of a File Handle . . . . . . . . . 12 3.2.2. Persistent File Handle . . . . . . . . . . . . . . . . 12 3.2.3. Volatile File Handle . . . . . . . . . . . . . . . . . 13 3.2.4. One Method of Constructing a Volatile File Handle . . 14 3.3. Client Recovery from File Handle Expiration . . . . . . 15 4. Basic Data Types . . . . . . . . . . . . . . . . . . . . . 16 5. File Attributes . . . . . . . . . . . . . . . . . . . . . 18 5.1. Mandatory Attributes . . . . . . . . . . . . . . . . . . 19 5.2. Recommended Attributes . . . . . . . . . . . . . . . . . 19 5.3. Named Attributes . . . . . . . . . . . . . . . . . . . . 20 5.4. Mandatory Attributes - Definitions . . . . . . . . . . . 20 5.5. Recommended Attributes - Definitions . . . . . . . . . . 22 6. NFS Server Namespace . . . . . . . . . . . . . . . . . . . 28 6.1. Server Exports . . . . . . . . . . . . . . . . . . . . . 28 6.2. Browsing Exports . . . . . . . . . . . . . . . . . . . . 28 6.3. Server Pseudo File-System . . . . . . . . . . . . . . . 29 6.4. Multiple Roots . . . . . . . . . . . . . . . . . . . . . 29 6.5. Filehandle Volatility . . . . . . . . . . . . . . . . . 29 6.6. Exported Root . . . . . . . . . . . . . . . . . . . . . 29 6.7. Mount Point Crossing . . . . . . . . . . . . . . . . . . 30 6.8. Summary . . . . . . . . . . . . . . . . . . . . . . . . 30 7. File Locking . . . . . . . . . . . . . . . . . . . . . . . 31 7.1. Definitions . . . . . . . . . . . . . . . . . . . . . . 31 7.2. Locking . . . . . . . . . . . . . . . . . . . . . . . . 32 7.2.1. Client ID . . . . . . . . . . . . . . . . . . . . . . 32 7.2.2. nfs_lockowner and stateid definition . . . . . . . . . 34 7.2.3. Use of the stateid . . . . . . . . . . . . . . . . . . 34 7.2.4. Sequencing of lock requests . . . . . . . . . . . . . 35 7.3. Blocking locks . . . . . . . . . . . . . . . . . . . . . 35 7.4. Lease renewal . . . . . . . . . . . . . . . . . . . . . 36 7.5. Crash recovery . . . . . . . . . . . . . . . . . . . . . 36 Expires: December 1999 [Page 3]
Draft Protocol Specification NFS version 4 June 1999 7.6. Server revocation of locks . . . . . . . . . . . . . . . 37 7.7. Share Reservations . . . . . . . . . . . . . . . . . . . 38 7.8. OPEN/CLOSE procedures . . . . . . . . . . . . . . . . . 38 8. Defined Error Numbers . . . . . . . . . . . . . . . . . . 40 9. NFS Version 4 Requests . . . . . . . . . . . . . . . . . . 45 9.1. Compound Procedure . . . . . . . . . . . . . . . . . . . 45 9.2. Evaluation of a Compound Request . . . . . . . . . . . . 45 10. NFS Version 4 Procedures . . . . . . . . . . . . . . . . 47 10.1. Procedure 0: NULL - No Operation . . . . . . . . . . . 47 10.2. Procedure 1: COMPOUND - Compound Operations . . . . . . 48 10.3. Procedure 2: ACCESS - Check Access Permission . . . . . 50 10.4. Procedure 3: CLOSE - Close File . . . . . . . . . . . . 53 10.5. Procedure 4: COMMIT - Commit Cached Data . . . . . . . 55 10.6. Procedure 5: CREATE - Create a Non-Regular File Object 58 10.7. Procedure 6: GETATTR - Get Attributes . . . . . . . . . 62 10.8. Procedure 7: GETFH - Get Current Filehandle . . . . . . 64 10.9. Procedure 8: LINK - Create Link to a File . . . . . . . 66 10.10. Procedure 9: LOCK - Create Lock . . . . . . . . . . . 68 10.11. Procedure 10: LOCKT - Test For Lock . . . . . . . . . 70 10.12. Procedure 11: LOCKU - Unlock File . . . . . . . . . . 72 10.13. Procedure 12: LOOKUP - Lookup Filename . . . . . . . . 74 10.14. Procedure 13: LOOKUPP - Lookup Parent Directory . . . 77 10.15. Procedure 14: NVERIFY - Verify Difference in Attributes 79 10.16. Procedure 15: OPEN - Open a Regular File . . . . . . . 81 10.17. Procedure 16: OPENATTR - Open Named Attribute Directory 86 10.18. Procedure 17: PUTFH - Set Current Filehandle . . . . . 88 10.19. Procedure 18: PUTPUBFH - Set Public Filehandle . . . . 89 10.20. Procedure 19: PUTROOTFH - Set Root Filehandle . . . . 90 10.21. Procedure 20: READ - Read from File . . . . . . . . . 91 10.22. Procedure 21: READDIR - Read Directory . . . . . . . . 94 10.23. Procedure 22: READLINK - Read Symbolic Link . . . . . 98 10.24. Procedure 23: REMOVE - Remove Filesystem Object . . . 100 10.25. Procedure 24: RENAME - Rename Directory Entry . . . . 102 10.26. Procedure 25: RENEW - Renew a Lease . . . . . . . . . 105 10.27. Procedure 25: RESTOREFH - Restore Saved Filehandle . . 106 10.28. Procedure 27: SAVEFH - Save Current Filehandle . . . . 108 10.29. Procedure 28: SECINFO - Obtain Available Security . . 109 10.30. Procedure 29: SETATTR - Set Attributes . . . . . . . . 111 10.31. Procedure 30: SETCLIENTID - Negotiated Clientid . . . 114 10.32. Procedure 31: VERIFY - Verify Same Attributes . . . . 116 10.33. Procedure 32: WRITE - Write to File . . . . . . . . . 118 11. Locking notes . . . . . . . . . . . . . . . . . . . . . . 123 11.1. Short and long leases . . . . . . . . . . . . . . . . . 123 11.2. Clocks and leases . . . . . . . . . . . . . . . . . . . 123 11.3. Locks and lease times . . . . . . . . . . . . . . . . . 123 11.4. Locking of directories and other meta-files . . . . . . 124 11.5. Proxy servers and leases . . . . . . . . . . . . . . . 124 11.6. Locking and the new latency . . . . . . . . . . . . . . 124 Expires: December 1999 [Page 4]
Draft Protocol Specification NFS version 4 June 1999 12. Internationalization . . . . . . . . . . . . . . . . . . 125 12.1. Universal Versus Local Character Sets . . . . . . . . . 125 12.2. Overview of Universal Character Set Standards . . . . . 126 12.3. Difficulties with UCS-4, UCS-2, Unicode . . . . . . . . 127 12.4. UTF-8 and its solutions . . . . . . . . . . . . . . . . 128 13. Security Considerations . . . . . . . . . . . . . . . . . 129 14. NFS Version 4 RPC definition file . . . . . . . . . . . . 130 15. Bibliography . . . . . . . . . . . . . . . . . . . . . . 151 16. Authors and Contributors . . . . . . . . . . . . . . . . 155 16.1. Contributors . . . . . . . . . . . . . . . . . . . . . 155 16.2. Editor's Address . . . . . . . . . . . . . . . . . . . 155 16.3. Authors' Addresses . . . . . . . . . . . . . . . . . . 155 17. Full Copyright Statement . . . . . . . . . . . . . . . . 157 Expires: December 1999 [Page 5]
Draft Protocol Specification NFS version 4 June 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: stateless 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: December 1999 [Page 6]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 7]
Draft Protocol Specification NFS version 4 June 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. This section will be expanded to include the pertinent details from draft-ietf-nfsv4-nfssec-00.txt. 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. 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 Expires: December 1999 [Page 8]
Draft Protocol Specification NFS version 4 June 1999 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: December 1999 [Page 9]
Draft Protocol Specification NFS version 4 June 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 does not have a special file handle value as does the public 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 Expires: December 1999 [Page 10]
Draft Protocol Specification NFS version 4 June 1999 complete discussion of the server name space is in section 6, "NFS Server Name Space". 3.1.2. Public File Handle Unlike the root file handle, the public file handle is represented by a reserved or special value of the file handle. NFS version 4 defines the file handle as a variable length array of bytes (see section 4, "Basic Data Types"). The public file handle is the 'zero' file handle or in other words a file handle with a array length of zero. Again 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 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 Expires: December 1999 [Page 11]
Draft Protocol Specification NFS version 4 June 1999 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 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, 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). Expires: December 1999 [Page 12]
Draft Protocol Specification NFS version 4 June 1999 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 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 Fileset 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. Expires: December 1999 [Page 13]
Draft Protocol Specification NFS version 4 June 1999 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). Note 5 Fileset migration occurs when a the ownership of file system resources are transfered from one server to another without a transfer of ownership of the network resources. So this differs from the High Availability scenario. This also includes the move of a file system resources within the same server such that the fsid value is different. The fileset migration entry is a place holder until a file set migration proposal has been fully evaluated and decided upon. 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_EXPIRED 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_EXPIRED. If slot is out of range, return NFS4ERR_EXPIRED. If the generation number does not match, return NFS4ERR_EXPIRED. When the server reboots, the table is gone (it is volatile). Expires: December 1999 [Page 14]
Draft Protocol Specification NFS version 4 June 1999 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 is return 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 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: December 1999 [Page 15]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 16]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 17]
Draft Protocol Specification NFS version 4 June 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 crop up, 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: December 1999 [Page 18]
Draft Protocol Specification NFS version 4 June 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. If a server supports any per-filesystem attributes, it must support the fsid attribute so that the client may always determine when filesystems are crossed so that it can work correctly with these attributes. Expires: December 1999 [Page 19]
Draft Protocol Specification NFS version 4 June 1999 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 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. 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. Expires: December 1999 [Page 20]
Draft Protocol Specification NFS version 4 June 1999 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 file handles being provided are persistent or not. If the server is not able to make this determination, then it can choose volatile or non-persistent. 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. Expires: December 1999 [Page 21]
Draft Protocol Specification NFS version 4 June 1999 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? fsid.major 8 uint64 READ Unique filesystem identifier for the filesystem holding this object. fsid.minor 9 uint64 READ Unique filesystem identifier within the fsid.major filesystem identifier for the filesystem holding this object. 5.5. Recommended Attributes - Definitions Name # Data Type Access Description ___________________________________________________________________ ACL 10 nfsacl4 R/W The access control list for the object. [The nature and format of ACLs is still to be determined.] Expires: December 1999 [Page 22]
Draft Protocol Specification NFS version 4 June 1999 archive 11 boolean R/W Whether or not this file has been archived since the time of last modification (deprecated in favor of backup_time). cansettime 12 boolean READ Whether or not this object's filesystem can fill in the times on a SETATTR request without an explicit time. case_insensitive 13 boolean READ Are filename comparisons on this filesystem case insensitive? case_preserving 14 boolean READ Is filename case on this filesystem preserved? chown_restricted 15 boolean READ Will a request to change ownership be honored? filehandle 16 nfs4_fh READ The filehandle of this object (primarily for readdir requests). fileid 17 uint64 READ A number uniquely identifying the file within the filesystem. files_avail 18 uint64 READ File slots available to this user on the filesystem containing this object - this should be the smallest relevant limit. files_free 19 uint64 READ Free file slots on the filesystem containing this object - this should be the smallest relevant limit. Expires: December 1999 [Page 23]
Draft Protocol Specification NFS version 4 June 1999 files_total 20 uint64 READ Total file slots on the filesystem containing this object. hidden 21 boolean R/W Is file considered hidden? homogeneous 22 boolean READ Whether or not this object's filesystem is homogeneous, i.e. whether pathconf is the same for all filesystem objects. maxfilesize 23 uint64 READ Maximum supported file size for the filesystem of this object. maxlink 24 uint32 READ Maximum number of links for this object. maxname 25 uint32 READ Maximum filename size supported for this object. maxread 26 uint64 READ Maximum read size supported for this object. maxwrite 27 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 28 utf8<> R/W MIME body type/subtype of this object. Expires: December 1999 [Page 24]
Draft Protocol Specification NFS version 4 June 1999 mode 29 uint32 R/W Unix-style permission bits for this object (deprecated in favor of ACLs) no_trunc 30 boolean READ If a name longer than name_max is used, will an error be returned or will the name be truncated? numlinks 31 uint32 READ Number of links to this object. owner 32 utf8<> R/W The string name of the owner of this object. owner_group 33 utf8<> R/W The string name of the group of the owner of this object. quota_hard 34 uint64 READ Number of bytes of disk space beyond which the server will decline to allocate new space. quota_soft 35 uint64 READ Number of bytes of disk space at which the client may choose to warn the user about limited space. quota_used 36 uint64 READ Number of bytes of disk space occupied by the owner of this object on this filesystem. rawdev 37 specdata4 READ Raw device identifier. Expires: December 1999 [Page 25]
Draft Protocol Specification NFS version 4 June 1999 space_avail 38 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 39 uint64 READ Free disk space in bytes on the filesystem containing this object - this should be the smallest relevant limit. space_total 40 uint64 READ Total disk space in bytes on the filesystem containing this object. space_used 41 uint64 READ Number of filesystem bytes allocated to this object. system 42 boolean R/W Whether or not this file is a system file. time_access 43 nfstime4 R/W The time of last access to the object. time_backup 44 nfstime4 R/W The time of last backup of the object. time_create 45 nfstime4 R/W The time of creation of the object. This attribute does not have any relation to the traditional Unix file attribute 'ctime' or 'change time'. time_delta 46 nfstime4 READ Smallest useful server time granularity. time_metadata 47 nfstime4 R/W The time of last meta-data modification of the object. Expires: December 1999 [Page 26]
Draft Protocol Specification NFS version 4 June 1999 time_modify 48 nfstime4 R/W The time since the epoch of last modification to the object. version 49 utf8<> R/W Version number of this document. volatility 50 nfstime4 READ Approximate time until next expected change on this filesystem, as a measure of volatility. Expires: December 1999 [Page 27]
Draft Protocol Specification NFS version 4 June 1999 6. NFS Server Namespace 6.1. 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. The root filehandle 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 filehandle for it. The MOUNT protocol supports an EXPORTS procedure that will enumerate the server's exports. 6.2. Browsing Exports The NFS version 4 protocol provides a root filehandle that clients can use to obtain filehandles 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: December 1999 [Page 28]
Draft Protocol Specification NFS version 4 June 1999 6.3. 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 only of exported directories. The pseudo file-system has a unique fsid and behaves like a normal, read-only file-system. 6.4. 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. 6.5. 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 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. 6.6. 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) Expires: December 1999 [Page 29]
Draft Protocol Specification NFS version 4 June 1999 /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. 6.7. Mount Point Crossing The server file-system environment may 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. 6.8. 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: December 1999 [Page 30]
Draft Protocol Specification NFS version 4 June 1999 7. 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. 7.1. 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: December 1999 [Page 31]
Draft Protocol Specification NFS version 4 June 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. 7.2. 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. 7.2.1. 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: December 1999 [Page 32]
Draft Protocol Specification NFS version 4 June 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_IN_USE, 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: December 1999 [Page 33]
Draft Protocol Specification NFS version 4 June 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. 7.2.2. 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. 7.2.3. 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: December 1999 [Page 34]
Draft Protocol Specification NFS version 4 June 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. 7.2.4. 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. 7.3. 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: December 1999 [Page 35]
Draft Protocol Specification NFS version 4 June 1999 7.4. 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. 7.5. 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. I/O operations that may have been queued within the client or network buffers, cannot complete until after the client has successfully recovered the lock protecting the I/O operation. If a client fails, the server only needs to wait the lease period to allow conflicting locks. If the client reinitializes within the lease period, it may be forced to wait the remainder of the period before resuming service. To minimize this delay, lock requests contain a verifier field in the lock_owner, if the server receives a verifier field that does not match the existing verifier, the server knows that the client has lost all lock state and locks held for that client that do not match the current verifier may be released. In a secure environment, a change in the verifier must only cause the locks held by the authenticated requester to be released in order to prevent a rogue user from freeing otherwise valid locks. The verifier must have the same uniqueness properties of the COMMIT verifier. 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 an invalid stateid will fail with NFS4ERR_GRACE, the client will reissue the lock request with reclaim set to TRUE, and upon receiving a successful reply, the I/O may be reissued with the new stateid. Any time a client receives an Expires: December 1999 [Page 36]
Draft Protocol Specification NFS version 4 June 1999 NFS4ERR_GRACE error it should start recovering all outstanding locks. A lock request during the grace period without reclaim set will also result in a NFS4ERR_GRACE, triggering the client recovery processing. A lock request outside the grace period with reclaim set will succeed only if the server can guarantee that no conflicting lock or I/O request has been granted since reboot. In the case of a network partition longer than the lease period, the server will have not received an implicit lease renewal and may free all locks held for the client, thus invalidating any stateid held by the client. Subsequent reconnection will cause I/O with invalid stateid to fail with NFS4ERR_EXPIRED, the client will suitably notify the application holding the lock. After the lease period has expired the server may optionally continue to hold the locks for the client. In this case, if a conflicting lock or I/O request is received, the lock must be freed to allow the client to detect possible corruption. When there is a network partition and the lease expires, the server must record on stable storage the client information relating to those leases. This is to prevent the case where another client obtains the conflicting lock, frees the lock, and the server reboots. After the server recovers the original client may recover the network partition and attempt to reclaim the lock. Without any state to indicate that a conflicting may have occurred, the client could get in an inconsistent state. Storing just the client information is the minimal state necessary to detect this condition, but could lead to losing locks unnecessarily. However this is considered to be a very rare event, and a sophisticated server could store more state completely eliminate any unnecessary locks being lost. 7.6. Server revocation of locks The server can revoke the locks held by a client at any time, when the client detects revocation it must ensure its state matches that of the server. If locks are revoked due to a server reboot, the client will receive a NFS4ERR_GRACE and normal crash recovery described above will be performed. The server may revoke a lock within the lease period, this is considered a rare event likely to be initiated only by a human (as part of an administration task). The client may assume that only the file that caused the NFS4ERR_EXPIRED to be returned has lost the lock_owner's locks and notifies the holder appropriately. The client can not assume the lease period has been renewed. The client not being able to renew the lease period is a relatively rare and unusual state. Both sides will detect this state and can recover without data corruption. The client must mark all locks held Expires: December 1999 [Page 37]
Draft Protocol Specification NFS version 4 June 1999 as "invalidated" and then must issue an I/O request, either a pending I/O or zero length read to revalidate the lock. If the response is success the lock is upgraded to valid, otherwise it was revoked by the server and the owner is notified. 7.7. 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: if ((request.access & file_state.deny)) || (request.deny & file_state.access)) return (NFS4ERR_DENIED) Old DOS applications specify shares in compatibility mode. Microsoft has indicated in the Win32 specification that it will be deprecated in the future and recommends that deny NONE be used. This specification does not support compatibility mode. 7.8. 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 Expires: December 1999 [Page 38]
Draft Protocol Specification NFS version 4 June 1999 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: December 1999 [Page 39]
Draft Protocol Specification NFS version 4 June 1999 8. 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: December 1999 [Page 40]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 41]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 42]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 43]
Draft Protocol Specification NFS version 4 June 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. Expires: December 1999 [Page 44]
Draft Protocol Specification NFS version 4 June 1999 9. NFS Version 4 Requests For the NFS program, version 4, there are two traditional RPC procedures: NULL and COMPOUND. All other procedures for NFS version 4 are defined in normal XDR/RPC syntax and semantics except that these procedures are encapsulated within the COMPOUND request. This requires that the client combine one or more NFSv4 procedures into a single request. 9.1. 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. 9.2. Evaluation of a Compound Request The server will process the COMPOUND procedure by evaluating each of the procedures within the COMPOUND request in order. Each component procedure or 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. Expires: December 1999 [Page 45]
Draft Protocol Specification NFS version 4 June 1999 There are no atomicity requirements for the procedures contained within the COMPOUND procedure. The procedures being evaluated as part of a COMPOUND request may and more than likely will 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: December 1999 [Page 46]
Draft Protocol Specification NFS version 4 June 1999 10. NFS Version 4 Procedures 10.1. Procedure 0: NULL - No Operation SYNOPSIS <null> ARGUMENT void; RESULT void; DESCRIPTION Standard ONCRPC NULL procedure. Void argument, void response. ERRORS None. Expires: December 1999 [Page 47]
Draft Protocol Specification NFS version 4 June 1999 10.2. 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 COMPOUND4resok { utf8string tag; resultdata data<>; }; union COMPOUND4res switch (nfsstat4 status){ case NFS4_OK: COMPOUND4resok resok4; default: void; }; 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. Expires: December 1999 [Page 48]
Draft Protocol Specification NFS version 4 June 1999 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 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. ERRORS NFS4ERR_RESOURCE Expires: December 1999 [Page 49]
Draft Protocol Specification NFS version 4 June 1999 10.3. Procedure 2: ACCESS - Check Access Permission SYNOPSIS (cfh), permbits -> permbits 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_taccess; }; RESULT struct ACCESS4resok { uint32_taccess; }; union ACCESS4res switch (nfsstat4 status) { case NFS4_OK: ACCESS4resokresok; 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 permissions that are to be checked in a bit mask. The server checks the permissions encoded in the bit mask. A status of NFS4_OK is returned along with a bit mask encoded with the permissions that the client is allowed. Expires: December 1999 [Page 50]
Draft Protocol Specification NFS version 4 June 1999 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_MODIFY: bit 2 Rewrite existing file data or modify existing directory entries. ACCESS_LOOKUP: bit 3 Look up a name in a directory (no meaning for non-directory objects). 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). The server must return an error if the any access permission cannot be determined. 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 not one or more classes of operations are permitted. The ACCESS operation is provided to allow clients to check before doing a Expires: December 1999 [Page 51]
Draft Protocol Specification NFS version 4 June 1999 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. Thus, the bit mask returned for such a request will have the ACCESS_DELETE bit set to 0, indicating that the client does not have this permission. ERRORS NFS4ERR_IO NFS4ERR_ACCES NFS4ERR_SERVERFAULT NFS4ERR_STALE NFS4ERR_BADHANDLE NFS4ERR_FHEXPIRED NFS4ERR_WRONGSEC Expires: December 1999 [Page 52]
Draft Protocol Specification NFS version 4 June 1999 10.4. Procedure 3: CLOSE - Close File SYNOPSIS (cfh), stateid -> stateid ARGUMENT struct CLOSE4args { stateid4stateid; }; RESULT union CLOSE4res switch (nfsstat4 status) { case NFS4_OK: stateid4stateid; 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: December 1999 [Page 53]
Draft Protocol Specification NFS version 4 June 1999 NFS4ERR_SERVERFAULT NFS4ERR_EXPIRED NFS4ERR_GRACE NFS4ERR_FHEXPIRED Expires: December 1999 [Page 54]
Draft Protocol Specification NFS version 4 June 1999 10.5. Procedure 4: COMMIT - Commit Cached Data SYNOPSIS (cfh), offset, count -> verifier ARGUMENT struct COMMIT4args { /* CURRENT_FH: file */ offset4offset; count4count; }; RESULT struct COMMIT4resok { writeverf4verf; }; union COMMIT4res switch (nfsstat4 status) { case NFS4_OK: COMMIT4resokresok4; 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: December 1999 [Page 55]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 56]
Draft Protocol Specification NFS version 4 June 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 Expires: December 1999 [Page 57]
Draft Protocol Specification NFS version 4 June 1999 10.6. Procedure 5: CREATE - Create a Non-Regular File Object SYNOPSIS (cfh), name, type, how -> (cfh) ARGUMENT struct CREATE4args { /* CURRENT_FH: directory for creation */ filename4objname; fattr4_typetype; createhow4createhow; }; RESULT struct CREATE4res { nfsstat4status; }; 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 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 Expires: December 1999 [Page 58]
Draft Protocol Specification NFS version 4 June 1999 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. 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 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. Expires: December 1999 [Page 59]
Draft Protocol Specification NFS version 4 June 1999 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 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 Expires: December 1999 [Page 60]
Draft Protocol Specification NFS version 4 June 1999 NFS4ERR_NAMETOOLONG NFS4ERR_DQUOT NFS4ERR_NOTSUPP NFS4ERR_SERVERFAULT NFS4ERR_FHEXPIRED NFS4ERR_WRONGSEC Expires: December 1999 [Page 61]
Draft Protocol Specification NFS version 4 June 1999 10.7. Procedure 6: 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: GETATTR4resokresok4; 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: December 1999 [Page 62]
Draft Protocol Specification NFS version 4 June 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 Expires: December 1999 [Page 63]
Draft Protocol Specification NFS version 4 June 1999 10.8. Procedure 7: 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: GETFH4resokresok4; 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: December 1999 [Page 64]
Draft Protocol Specification NFS version 4 June 1999 ERRORS NFS4ERR_SERVERFAULT Expires: December 1999 [Page 65]
Draft Protocol Specification NFS version 4 June 1999 10.9. Procedure 8: LINK - Create Link to a File SYNOPSIS (cfh), directory, newname -> (cfh) ARGUMENT struct LINK4args { /* CURRENT_FH: file */ nfs4_fh dir; filename4 newname; }; RESULT struct LINK4res { nfsstat4status; }; DESCRIPTION The LINK procedure creates an additional newname for the file with the current filehandle in the new directory dir file and link.dir must reside on the same file system and server. IMPLEMENTATION 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 Expires: December 1999 [Page 66]
Draft Protocol Specification NFS version 4 June 1999 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 Expires: December 1999 [Page 67]
Draft Protocol Specification NFS version 4 June 1999 10.10. Procedure 9: LOCK - Create Lock SYNOPSIS (cfh) type, seqid, reclaim, owner, offset, length -> stateid, access ARGUMENT struct lockown { clientid4clientid; opaqueowner<>; }; union nfs_lockowner switch (stateid4 stateid) { case 0: lockownident; default: void; }; 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_typetype; seqid4seqid; boolreclaim; nfs_lockownerowner; offset4offset; length4length; }; RESULT struct lockres { stateid4stateid; int32_taccess; }; Expires: December 1999 [Page 68]
Draft Protocol Specification NFS version 4 June 1999 union LOCK4res switch (nfsstat4 status) { case NFS4_OK: lockresresult; default: void; }; DESCRIPTION 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 Expires: December 1999 [Page 69]
Draft Protocol Specification NFS version 4 June 1999 10.11. Procedure 10: LOCKT - Test For Lock SYNOPSIS (cfh) type, seqid, reclaim, owner, offset, length -> {void, NFS4ERR_DENIED -> owner} ARGUMENT struct LOCK4args { /* CURRENT_FH: file */ nfs4_lock_typetype; seqid4seqid; boolreclaim; nfs_lockownerowner; offset4offset; length4length; }; RESULT union LOCKT4res switch (nfsstat4 status) { case NFS4ERR_DENIED: nfs_lockownerowner; 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: December 1999 [Page 70]
Draft Protocol Specification NFS version 4 June 1999 ERRORS NFS4ERR_ACCES NFS4ERR_ISDIR NFS4ERR_INVAL NFS4ERR_STALE NFS4ERR_BADHANDLE NFS4ERR_SERVERFAULT NFS4ERR_DENIED NFS4ERR_GRACE NFS4ERR_FHEXPIRED Expires: December 1999 [Page 71]
Draft Protocol Specification NFS version 4 June 1999 10.12. Procedure 11: LOCKU - Unlock File SYNOPSIS (cfh) type, seqid, reclaim, owner, offset, length -> stateid ARGUMENT struct LOCK4args { /* CURRENT_FH: file */ nfs4_lock_typetype; seqid4seqid; boolreclaim; nfs_lockownerowner; offset4offset; length4length; }; RESULT union LOCKU4res switch (nfsstat4 status) { caseNFS4_OK: stateid4stateid_ok; default: stateid4stateid_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: December 1999 [Page 72]
Draft Protocol Specification NFS version 4 June 1999 NFS4ERR_ISDIR NFS4ERR_INVAL NFS4ERR_STALE NFS4ERR_BADHANDLE NFS4ERR_SERVERFAULT NFS4ERR_GRACE NFS4ERR_FHEXPIRED Expires: December 1999 [Page 73]
Draft Protocol Specification NFS version 4 June 1999 10.13. Procedure 12: LOOKUP - Lookup Filename SYNOPSIS (cfh), filenames -> (cfh) ARGUMENT struct LOOKUP4args { /* CURRENT_FH: directory */ filename4 filenames<>; }; RESULT struct LOOKUP4res { /* CURRENT_FH: object */ nfsstat4status; }; 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: December 1999 [Page 74]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 75]
Draft Protocol Specification NFS version 4 June 1999 NFS4ERR_STALE NFS4ERR_SERVERFAULT NFS4ERR_FHEXPIRED Expires: December 1999 [Page 76]
Draft Protocol Specification NFS version 4 June 1999 10.14. Procedure 13: LOOKUPP - Lookup Parent Directory SYNOPSIS (cfh) -> (cfh) ARGUMENT /* CURRENT_FH: object */ void; RESULT struct LOOKUPP4res { /* CURRENT_FH: directory */ nfsstat4status; }; 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. IMPLEMENTATION As for LOOKUP, LOOKUPP will also cross mountpoints. ERRORS NFS4ERR_NOENT NFS4ERR_IO NFS4ERR_ACCES NFS4ERR_INVAL NFS4ERR_STALE Expires: December 1999 [Page 77]
Draft Protocol Specification NFS version 4 June 1999 NFS4ERR_SERVERFAULT NFS4ERR_FHEXPIRED Expires: December 1999 [Page 78]
Draft Protocol Specification NFS version 4 June 1999 10.15. Procedure 14: NVERIFY - Verify Difference in Attributes SYNOPSIS (cfh), attrbits, attrvals -> - ARGUMENT struct NVERIFY4args { /* CURRENT_FH: object */ bitmap4 attr_request; fattr4 obj_attributes; }; RESULT struct NVERIFY4res { nfsstat4status; }; 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: December 1999 [Page 79]
Draft Protocol Specification NFS version 4 June 1999 ERRORS NFS4ERR_IO NFS4ERR_ACCES NFS4ERR_STALE NFS4ERR_BADHANDLE NFS4ERR_SERVERFAULT NFS4ERR_FHEXPIRED NFS4ERR_SAME Expires: December 1999 [Page 80]
Draft Protocol Specification NFS version 4 June 1999 10.16. Procedure 15: OPEN - Open a Regular File SYNOPSIS (cfh), file, openhow, owner, seqid, reclaim, access, deny -> (cfh), stateid, access ARGUMENT struct OPEN4args { open_nameorfh file; openflag openhow; nfs_lockowner owner; seqid4 seqid; bool reclaim; int32_t access; int32_t deny; }; union open_nameoffh switch (bool reclaim_fh) { case FALSE: /* CURRENT_FH: directory */ filename4 filenames<>; case TRUE: /* CURRENT_FH: file on reclaim */ void; }; 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_NOCREATE0, OPEN4_CREATE1 }; Expires: December 1999 [Page 81]
Draft Protocol Specification NFS version 4 June 1999 union openflag switch (opentype4 opentype) { case OPEN4_CREATE: createhow4how; default: void; }; /* * 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; RESULT union OPEN4res switch (nfsstat4 status) { case NFS4_OK: /* CURRENT_FH: opened file */ LOCK4resresok; 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: December 1999 [Page 82]
Draft Protocol Specification NFS version 4 June 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 use to signify that the request is meant to reclaim state previously held. The file field of the OPEN argument allows the client to specify an open by name or by filehandle. The filehandle MAY only be specified in the case that the OPEN is a reclaim request. It is expected that if the server is providing persistent filehandles, the client will not have file names saved to request a reclaim OPEN by name. For non-reclaim OPEN requests that reach the server during its grace or lease expiration period, the server returns an error of NFS4ERR_GRACE. Expires: December 1999 [Page 83]
Draft Protocol Specification NFS version 4 June 1999 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 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, Expires: December 1999 [Page 84]
Draft Protocol Specification NFS version 4 June 1999 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 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. 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 Expires: December 1999 [Page 85]
Draft Protocol Specification NFS version 4 June 1999 10.17. Procedure 16: OPENATTR - Open Named Attribute Directory SYNOPSIS (cfh) -> (cfh) ARGUMENT /* CURRENT_FH: file or directory */ void; RESULT struct OPENATTR4res { /* CURRENT_FH: name attr directory*/ nfsstat4status; }; 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: December 1999 [Page 86]
Draft Protocol Specification NFS version 4 June 1999 NFS4ERR_ACCES NFS4ERR_INVAL NFS4ERR_STALE NFS4ERR_BADHANDLE NFS4ERR_NOTSUPP NFS4ERR_SERVERFAULT NFS4ERR_JUKEBOX NFS4ERR_FHEXPIRED NFS4ERR_WRONGSEC Expires: December 1999 [Page 87]
Draft Protocol Specification NFS version 4 June 1999 10.18. Procedure 17: PUTFH - Set Current Filehandle SYNOPSIS filehandle -> (cfh) ARGUMENT struct PUTFH4args { nfs4_fh object; }; RESULT struct PUTFH4res { /* CURRENT_FH: */ nfsstat4status; }; 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_SERVERFAULT NFS4ERR_WRONGSEC Expires: December 1999 [Page 88]
Draft Protocol Specification NFS version 4 June 1999 10.19. Procedure 18: PUTPUBFH - Set Public Filehandle SYNOPSIS - -> (cfh) ARGUMENT void; RESULT struct PUTPUBFH4res { /* CURRENT_FH: root fh */ nfsstat4status; }; 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: December 1999 [Page 89]
Draft Protocol Specification NFS version 4 June 1999 10.20. Procedure 19: PUTROOTFH - Set Root Filehandle SYNOPSIS - -> (cfh) ARGUMENT void; RESULT struct PUTROOTFH4res { /* CURRENT_FH: root fh */ nfsstat4status; }; 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: December 1999 [Page 90]
Draft Protocol Specification NFS version 4 June 1999 10.21. Procedure 20: READ - Read from File SYNOPSIS (cfh), offset, count, stateid -> eof, data ARGUMENT struct READ4args { /* CURRENT_FH: file */ stateid4stateid; offset4offset; count4count; }; RESULT struct READ4resok { booleof; opaquedata<>; }; union READ4res switch (nfsstat4 status) { case NFS4_OK: READ4resokresok4; 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: December 1999 [Page 91]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 92]
Draft Protocol Specification NFS version 4 June 1999 NFS4ERR_BADHANDLE NFS4ERR_SERVERFAULT NFS4ERR_DENIED NFS4ERR_JUKEBOX NFS4ERR_EXPIRED NFS4ERR_LOCKED NFS4ERR_GRACE NFS4ERR_FHEXPIRED NFS4ERR_WRONGSEC Expires: December 1999 [Page 93]
Draft Protocol Specification NFS version 4 June 1999 10.22. Procedure 21: READDIR - Read Directory SYNOPSIS (cfh), cookie, dircount, maxcount, attrbits -> { cookie, filename, attrbits, attributes } ARGUMENT struct READDIR4args { /* CURRENT_FH: directory */ nfs_cookie4cookie; count4dircount; count4maxcount; bitmap4attr_request; }; RESULT struct entry4 { nfs_cookie4cookie; filename4name; fattr4attrs; entry4*nextentry; }; struct dirlist4 { entry4*entries; booleof; }; struct READDIR4resok { dirlist4reply; }; union READDIR4res switch (nfsstat4 status) { case NFS4_OK: READDIR4resokresok4; default: void; }; Expires: December 1999 [Page 94]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 95]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 96]
Draft Protocol Specification NFS version 4 June 1999 NFS4ERR_NOTSUPP NFS4ERR_SERVERFAULT NFS4ERR_JUKEBOX NFS4ERR_FHEXPIRED NFS4ERR_WRONGSEC Expires: December 1999 [Page 97]
Draft Protocol Specification NFS version 4 June 1999 10.23. Procedure 22: READLINK - Read Symbolic Link SYNOPSIS (cfh) -> linktext ARGUMENT /* CURRENT_FH: symlink */ void; RESULT struct READLINK4resok { linktext4link; }; union READLINK4res switch (nfsstat4 status) { case NFS4_OK: READLINK4resokresok4; 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: December 1999 [Page 98]
Draft Protocol Specification NFS version 4 June 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 Expires: December 1999 [Page 99]
Draft Protocol Specification NFS version 4 June 1999 10.24. Procedure 23: REMOVE - Remove Filesystem Object SYNOPSIS (cfh), filename -> - ARGUMENT struct REMOVE4args { /* CURRENT_FH: directory */ filename4target; }; RESULT struct REMOVE4res { nfsstat4status; }; 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. 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 Expires: December 1999 [Page 100]
Draft Protocol Specification NFS version 4 June 1999 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 Expires: December 1999 [Page 101]
Draft Protocol Specification NFS version 4 June 1999 10.25. Procedure 24: RENAME - Rename Directory Entry SYNOPSIS (cfh), oldname, newdir, newname -> - ARGUMENT struct RENAME4args { /* CURRENT_FH: source directory */ filename4oldname; nfs4_fhnewdir; filename4newname; }; RESULT struct RENAME4res { nfsstat4status; }; 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 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. IMPLEMENTATION The RENAME operation must be atomic to the client. The statement "source and target directories must reside on the same file system Expires: December 1999 [Page 102]
Draft Protocol Specification NFS version 4 June 1999 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. 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. ERRORS NFS4ERR_NOENT NFS4ERR_IO NFS4ERR_ACCES NFS4ERR_EXIST NFS4ERR_XDEV NFS4ERR_NOTDIR NFS4ERR_ISDIR NFS4ERR_INVAL NFS4ERR_NOSPC NFS4ERR_ROFS NFS4ERR_MLINK NFS4ERR_NAMETOOLONG NFS4ERR_NOTEMPTY Expires: December 1999 [Page 103]
Draft Protocol Specification NFS version 4 June 1999 NFS4ERR_DQUOT NFS4ERR_STALE NFS4ERR_BADHANDLE NFS4ERR_NOTSUPP NFS4ERR_SERVERFAULT NFS4ERR_FHEXPIRED NFS4ERR_WRONGSEC Expires: December 1999 [Page 104]
Draft Protocol Specification NFS version 4 June 1999 10.26. Procedure 25: RENEW - Renew a Lease SYNOPSIS stateid -> () ARGUMENT struct RENEW4args { stateid4stateid; }; RESULT struct RENEW4res { nfsstat4status; }; 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 Expires: December 1999 [Page 105]
Draft Protocol Specification NFS version 4 June 1999 10.27. Procedure 25: RESTOREFH - Restore Saved Filehandle SYNOPSIS (sfh) -> (cfh) ARGUMENT /* SAVED_FH: */ void; RESULT struct RESTOREFH4res { /* CURRENT_FH: value of saved fh */ nfsstat4status; }; 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: December 1999 [Page 106]
Draft Protocol Specification NFS version 4 June 1999 ERRORS NFS4ERR_INVAL NFS4ERR_STALE NFS4ERR_BADHANDLE NFS4ERR_SERVERFAULT NFS4ERR_FHEXPIRED NFS4ERR_WRONGSEC Expires: December 1999 [Page 107]
Draft Protocol Specification NFS version 4 June 1999 10.28. Procedure 27: SAVEFH - Save Current Filehandle SYNOPSIS (cfh) -> (sfh) ARGUMENT /* CURRENT_FH: */ void; RESULT struct SAVEFH4res { /* SAVED_FH: value of current fh */ nfsstat4status; }; 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_INVAL NFS4ERR_STALE NFS4ERR_BADHANDLE NFS4ERR_SERVERFAULT NFS4ERR_FHEXPIRED NFS4ERR_WRONGSEC Expires: December 1999 [Page 108]
Draft Protocol Specification NFS version 4 June 1999 10.29. Procedure 28: SECINFO - Obtain Available Security SYNOPSIS (cfh), filename -> { secinfo } ARGUMENT struct SECINFO4args { /* CURRENT_FH: */ filename4name; }; RESULT struct rpc_flavor_info { sec_oid4oid; qop4qop; rpc_gss_svc_t service; }; struct secinfo4 { rpc_flavor4flavor; rpc_flavor_info *flavor_info; secinfo4*nextentry; }; struct SECINFO4resok { secinfo4reply; }; union SECINFO4res switch (nfsstat4 status) { case NFS4_OK: SECINFO4resokresok4; default: void; }; DESCRIPTION The SECINFO procedure is used by the client to obtain a list of Expires: December 1999 [Page 109]
Draft Protocol Specification NFS version 4 June 1999 valid RPC authentication flavors for a specific file handle, file name pair. For the flavors, AUTH_NONE, AUTH_SYS, AUTH_DH, and AUTH_KRB4 no additional security information is returned. For a return value of AUTH_RPCSEC_GSS, a security triple is returned that contains the mechanism object id (as defined in [RFC2078]), the quality of protection (as defined in [RFC 2078]) and the service type (as defined in [RFC2203]). It is possible for SECINFO to return multiple entries with flavor equal to AUTH_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 Expires: December 1999 [Page 110]
Draft Protocol Specification NFS version 4 June 1999 10.30. Procedure 29: SETATTR - Set Attributes SYNOPSIS (cfh), attrbits, attrvals -> - ARGUMENT struct SETATTR4args { /* CURRENT_FH: target object */ fattr4 obj_attributes; }; RESULT struct SETATTR4res { nfsstat4status; }; 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. 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 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. Expires: December 1999 [Page 111]
Draft Protocol Specification NFS version 4 June 1999 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 NFS4ERR_JUKEBOX NFS4ERR_DENIED NFS4ERR_GRACE NFS4ERR_FHEXPIRED Expires: December 1999 [Page 112]
Draft Protocol Specification NFS version 4 June 1999 NFS4ERR_WRONGSEC Expires: December 1999 [Page 113]
Draft Protocol Specification NFS version 4 June 1999 10.31. Procedure 30: SETCLIENTID - Negotiated Clientid SYNOPSIS verifier, client -> clientid ARGUMENT struct cid { opaque verifier<4>; opaque id<>; }; union nfs_client_id switch (clientid4 clientid) { case 0: cidident; default: void; }; struct SETCLIENTID4args { seqid4seqid; nfs_client_idclient; }; RESULT union SETCLIENTID4res switch (nfsstat4 status) { case NFS4_OK: clientid4clientid; 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: December 1999 [Page 114]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 115]
Draft Protocol Specification NFS version 4 June 1999 10.32. Procedure 31: VERIFY - Verify Same Attributes SYNOPSIS (cfh), attrbits, attrvals -> - ARGUMENT struct VERIFY4args { /* CURRENT_FH: object */ bitmap4 attr_request; fattr4 obj_attributes; }; RESULT struct VERIFY4res { nfsstat4status; }; 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: December 1999 [Page 116]
Draft Protocol Specification NFS version 4 June 1999 NFS4ERR_ACCES NFS4ERR_INVAL NFS4ERR_STALE NFS4ERR_BADHANDLE NFS4ERR_NOTSUPP NFS4ERR_SERVERFAULT NFS4ERR_JUKEBOX NFS4ERR_FHEXPIRED Expires: December 1999 [Page 117]
Draft Protocol Specification NFS version 4 June 1999 10.33. Procedure 32: 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 */ stateid4stateid; offset4offset; count4count; stable_how4stable; opaquedata<>; }; RESULT struct WRITE4resok { count4count; stable_how4committed; writeverf4verf; }; union WRITE4res switch (nfsstat4 status) { case NFS4_OK: WRITE4resokresok4; default: void; }; DESCRIPTION The WRITE procedure is used to write data to a regular file. The Expires: December 1999 [Page 118]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 119]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 120]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 121]
Draft Protocol Specification NFS version 4 June 1999 NFS4ERR_BADHANDLE NFS4ERR_SERVERFAULT NFS4ERR_JUKEBOX NFS4ERR_LOCKED NFS4ERR_GRACE NFS4ERR_FHEXPIRED NFS4ERR_WRONGSEC Expires: December 1999 [Page 122]
Draft Protocol Specification NFS version 4 June 1999 11. Locking notes 11.1. 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. 11.2. 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. 11.3. Locks and lease times Lock requests do not contain desired lease times. The server Expires: December 1999 [Page 123]
Draft Protocol Specification NFS version 4 June 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. 11.4. 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. 11.5. 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 ? 11.6. 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: December 1999 [Page 124]
Draft Protocol Specification NFS version 4 June 1999 12. 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. 12.1. 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: December 1999 [Page 125]
Draft Protocol Specification NFS version 4 June 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. 12.2. 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: December 1999 [Page 126]
Draft Protocol Specification NFS version 4 June 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. 12.3. 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: December 1999 [Page 127]
Draft Protocol Specification NFS version 4 June 1999 12.4. 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: December 1999 [Page 128]
Draft Protocol Specification NFS version 4 June 1999 13. 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: December 1999 [Page 129]
Draft Protocol Specification NFS version 4 June 1999 14. NFS Version 4 RPC definition file /* * nfs_prot.x * */ %#pragma ident "@(#)nfs4_prot.x 1.32 99/06/25" /* * 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; }; struct bitmap4 { uint32_t bits<>; }; /* * 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 filename4; typedef uint64_t nfs_lockid4; typedef uint32_t nfs_lease4; typedef uint32_t nfs_lockstate4; Expires: December 1999 [Page 130]
Draft Protocol Specification NFS version 4 June 1999 typedef uint64_t nfs_cookie4; typedef utf8string linktext4; typedef opaque sec_oid4<>; typedef uint32_t qop4; 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 uint64_t fattr4_fsid_major; typedef uint64_t fattr4_fsid_minor; 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; typedef uint64_t fattr4_files_free; typedef uint64_t fattr4_files_total; 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; Expires: December 1999 [Page 131]
Draft Protocol Specification NFS version 4 June 1999 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; /* * Error status */ enum nfsstat4 { 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 */ Expires: December 1999 [Page 132]
Draft Protocol Specification NFS version 4 June 1999 NFS4ERR_RESOURCE = 10018 /* resource exhaustion */ }; enum rpc_flavor4 { AUTH4_NONE = 0, AUTH4_SYS = 1, AUTH4_DH = 2, AUTH4_KRB4 = 3, AUTH4_RPCSEC_GSS = 4 }; /* * From RFC 2203 */ enum rpc_gss_svc_t { RPC_GSS_SVC_NONE = 1, RPC_GSS_SVC_INTEGRITY = 2, RPC_GSS_SVC_PRIVACY = 3 }; /* * File access handle */ struct nfs4_fh { opaque data<NFS4_FHSIZE>; }; /* * File types */ enum nfs4_ftype { 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; Expires: December 1999 [Page 133]
Draft Protocol Specification NFS version 4 June 1999 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_MAJOR = 8; const FATTR4_FSID_MINOR = 9; /* * Recommended Attributes */ const FATTR4_ACL = 10; const FATTR4_ARCHIVE = 11; const FATTR4_CANSETTIME = 12; const FATTR4_CASE_INSENSITIVE = 13; const FATTR4_CASE_PRESERVING = 14; const FATTR4_CHOWN_RESTRICTED = 15; const FATTR4_FILEHANDLE = 16; const FATTR4_FILEID = 17; const FATTR4_FILES_AVAIL = 18; const FATTR4_FILES_FREE = 19; const FATTR4_FILES_TOTAL = 20; const FATTR4_HIDDEN = 21; const FATTR4_HOMOGENEOUS = 22; const FATTR4_MAXFILESIZE = 23; const FATTR4_MAXLINK = 24; const FATTR4_MAXNAME = 25; const FATTR4_MAXREAD = 26; const FATTR4_MAXWRITE = 27; const FATTR4_MIME_TYPE = 28; const FATTR4_MODE = 29; const FATTR4_NO_TRUNC = 30; const FATTR4_NUMLINKS = 31; const FATTR4_OWNER = 32; const FATTR4_OWNER_GROUP = 33; const FATTR4_QUOTA_HARD = 34; const FATTR4_QUOTA_SOFT = 35; const FATTR4_QUOTA_USED = 36; const FATTR4_RAWDEV = 37; const FATTR4_SPACE_AVAIL = 38; const FATTR4_SPACE_FREE = 39; const FATTR4_SPACE_TOTAL = 40; const FATTR4_SPACE_USED = 41; const FATTR4_SYSTEM = 42; const FATTR4_TIME_ACCESS = 43; const FATTR4_TIME_BACKUP = 44; const FATTR4_TIME_CREATE = 45; const FATTR4_TIME_DELTA = 46; Expires: December 1999 [Page 134]
Draft Protocol Specification NFS version 4 June 1999 const FATTR4_TIME_METADATA = 47; const FATTR4_TIME_MODIFY = 48; const FATTR4_VERSION = 49; const FATTR4_VOLATILITY = 50; struct attrlist { opaque attrs<>; }; struct fattr4 { bitmap4 attrmask; attrlist attr_vals; }; struct cid { opaque verifier<4>; opaque id<>; }; union nfs_client_id switch (clientid4 clientid) { case 0: cid ident; default: void; }; struct lockown { clientid4 clientid; opaque owner<>; }; union nfs_lockowner switch (stateid4 stateid) { case 0: lockown ident; default: void; }; enum nfs4_lock_type { READ_LT = 1, WRITE_LT = 2, READW_LT = 3, /* blocking read */ WRITEW_LT = 4 /* blocking write */ }; /* * ACCESS: Check access permission Expires: December 1999 [Page 135]
Draft Protocol Specification NFS version 4 June 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 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: December 1999 [Page 136]
Draft Protocol Specification NFS version 4 June 1999 enum createmode4 { UNCHECKED4 = 0, GUARDED4 = 1, EXCLUSIVE4 = 2 }; union createhow4 switch (createmode4 mode) { case UNCHECKED4: case GUARDED4: fattr4 createattrs; case EXCLUSIVE4: createverf4 verf; }; const ACCESS4_READ = 0x0001; const ACCESS4_MODIFY = 0x0002; const ACCESS4_LOOKUP = 0x0004; const ACCESS4_EXTEND = 0x0008; const ACCESS4_DELETE = 0x0010; const ACCESS4_EXECUTE = 0x0020; 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 */ nfs4_lock_type type; seqid4 seqid; bool reclaim; nfs_lockowner owner; offset4 offset; length4 length; }; struct lockres { stateid4 stateid; Expires: December 1999 [Page 137]
Draft Protocol Specification NFS version 4 June 1999 int32_t access; }; union LOCK4res switch (nfsstat4 status) { case NFS4_OK: lockres result; 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; }; union SETCLIENTID4res switch (nfsstat4 status) { case NFS4_OK: clientid4 clientid; default: void; }; /* * Access and Deny constants for open argument */ const OPEN4_ACCESS_READ = 0x0001; const OPEN4_ACCESS_WRITE= 0x0002; const OPEN4_ACCESS_BOTH = 0x0003; Expires: December 1999 [Page 138]
Draft Protocol Specification NFS version 4 June 1999 const OPEN4_DENY_NONE = 0x0000; const OPEN4_DENY_READ = 0x0001; const OPEN4_DENY_WRITE = 0x0002; const OPEN4_DENY_BOTH = 0x0003; union open_nameoffh switch (bool reclaim_fh) { case FALSE: /* CURRENT_FH: directory */ filename4 filenames<>; case TRUE: /* CURRENT_FH: file on reclaim */ void; }; /* * OPEN: Open a file, potentially with a share lock */ struct OPEN4args { open_nameorfh file; openflag openhow; nfs_lockowner owner; seqid4 seqid; bool reclaim; int32_t access; int32_t deny; }; union OPEN4res switch (nfsstat4 status) { case NFS4_OK: /* CURRENT_FH: opened file */ LOCK4res resok4; default: void; }; /* * CREATE: Create special file */ struct CREATE4args { /* CURRENT_FH: directory for creation */ filename4 objname; fattr4_type type; createhow4 createhow; }; struct CREATE4res { nfsstat4 status; Expires: December 1999 [Page 139]
Draft Protocol Specification NFS version 4 June 1999 }; /* * 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; }; struct GETATTR4resok { fattr4 obj_attributes; }; union GETATTR4res switch (nfsstat4 status) { case NFS4_OK: GETATTR4resok resok4; default: void; }; /* * OPENATTR: open named attributes directory */ struct OPENATTR4res { /* CURRENT_FH: name attr directory*/ nfsstat4 status; }; /* * GETFH: Get current filehandle */ struct GETFH4resok { Expires: December 1999 [Page 140]
Draft Protocol Specification NFS version 4 June 1999 nfs4_fh object; }; union GETFH4res switch (nfsstat4 status) { case NFS4_OK: GETFH4resok resok4; default: void; }; /* * LINK: Create link to an object */ struct LINK4args { /* CURRENT_FH: file */ nfs4_fh dir; filename4 newname; }; struct LINK4res { nfsstat4 status; }; /* * LOOKUP: Lookup filename */ struct LOOKUP4args { /* CURRENT_FH: directory */ filename4 filenames<>; }; struct LOOKUP4res { /* CURRENT_FH: object */ nfsstat4 status; }; /* * LOOKUPP: Lookup parent directory */ struct LOOKUPP4res { /* CURRENT_FH: directory */ nfsstat4 status; }; /* * NVERIFY: Verify attributes different */ struct NVERIFY4args { Expires: December 1999 [Page 141]
Draft Protocol Specification NFS version 4 June 1999 /* 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 { nfs4_fh object; }; struct PUTFH4res { /* CURRENT_FH: */ nfsstat4 status; }; /* * PUTROOTFH: Set root filehandle */ struct PUTROOTFH4res { /* CURRENT_FH: root fh */ nfsstat4 status; }; /* * PUTPUBFH: Set public filehandle Expires: December 1999 [Page 142]
Draft Protocol Specification NFS version 4 June 1999 */ 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; filename4 name; fattr4 attrs; entry4 *nextentry; }; struct dirlist4 { Expires: December 1999 [Page 143]
Draft Protocol Specification NFS version 4 June 1999 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 */ filename4 target; }; struct REMOVE4res { nfsstat4 status; }; /* * RENAME: Rename directory entry */ struct RENAME4args { /* CURRENT_FH: source directory */ Expires: December 1999 [Page 144]
Draft Protocol Specification NFS version 4 June 1999 filename4 oldname; nfs4_fh newdir; filename4 newname; }; struct RENAME4res { nfsstat4 status; }; /* * RENEW: Renew a Lease */ struct RENEW4args { stateid4 stateid; }; struct RENEW4res { nfsstat4 status; }; /* * SETATTR: Set attributes */ struct SETATTR4args { /* CURRENT_FH: target object */ fattr4 obj_attributes; }; 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 */ Expires: December 1999 [Page 145]
Draft Protocol Specification NFS version 4 June 1999 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; }; /* * SECINFO: Obtain Available Security Mechanisms */ struct SECINFO4args { /* CURRENT_FH: */ filename4 name; }; struct rpc_flavor_info { sec_oid4 oid; qop4 qop; rpc_gss_svc_t service; }; struct secinfo4 { rpc_flavor4 flavor; rpc_flavor_info *flavor_info; secinfo4 *nextentry; }; Expires: December 1999 [Page 146]
Draft Protocol Specification NFS version 4 June 1999 struct SECINFO4resok { secinfo4 reply; }; 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_GETATTR = 6, OP_GETFH = 7, OP_LINK = 8, OP_LOCK = 9, OP_LOCKT = 10, OP_LOCKU = 11, OP_LOOKUP = 12, OP_LOOKUPP = 13, OP_NVERIFY = 14, OP_OPEN = 15, OP_OPENATTR = 16, OP_PUTFH = 17, OP_PUTPUBFH = 18, OP_PUTROOTFH = 19, OP_READ = 20, OP_READDIR = 21, OP_READLINK = 22, OP_REMOVE = 23, OP_RENAME = 24, OP_RENEW = 25, OP_RESTOREFH = 26, OP_SAVEFH = 27, OP_SECINFO = 28, OP_SETATTR = 29, OP_SETCLIENTID = 30, OP_VERIFY = 31, OP_WRITE = 32 }; union opunion switch (unsigned opcode) { case OP_ACCESS: ACCESS4args opaccess; Expires: December 1999 [Page 147]
Draft Protocol Specification NFS version 4 June 1999 case OP_CLOSE: CLOSE4args opclose; case OP_COMMIT: COMMIT4args opcommit; case OP_CREATE: CREATE4args opcreate; case OP_GETATTR: GETATTR4args opgettattr; 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; 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 op; case OP_CLOSE: CLOSE4res opclose; case OP_COMMIT: COMMIT4res opcommit; case OP_CREATE: CREATE4res opcreate; 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; Expires: December 1999 [Page 148]
Draft Protocol Specification NFS version 4 June 1999 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 { utf8string tag; op oplist<>; }; struct COMPOUND4resok { utf8string tag; resultdata data<>; }; union COMPOUND4res switch (nfsstat4 status){ case NFS4_OK: COMPOUND4resok resok4; default: void; }; /* * Remote file service routines */ program NFS4_PROGRAM { version NFS_V4 { void NFSPROC4_NULL(void) = 0; Expires: December 1999 [Page 149]
Draft Protocol Specification NFS version 4 June 1999 COMPOUND4res NFSPROC4_COMPOUND(COMPOUND4args) = 1; } = 4; } = 100003; Expires: December 1999 [Page 150]
Draft Protocol Specification NFS version 4 June 1999 15. 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: December 1999 [Page 151]
Draft Protocol Specification NFS version 4 June 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: December 1999 [Page 152]
Draft Protocol Specification NFS version 4 June 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 [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- Expires: December 1999 [Page 153]
Draft Protocol Specification NFS version 4 June 1999 offs. [SPNEGO] Baize, E., Pinkas, D., "The Simple and Protected GSS-API Negotiation Mechanism", draft-ietf-cat-snego-09.txt, Bull, April 1998. ftp://ftp.isi.edu/internet-drafts/draft-ietf-cat-snego-09.txt [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: December 1999 [Page 154]
Draft Protocol Specification NFS version 4 June 1999 16. Authors and Contributors General feedback related to this document should be directed to: nfsv4-wg@sunroof.eng.sun.com or the editor. 16.1. Contributors The following individuals have contributed to the document: Carl Beame, beame@bws.com, of Hummingbird Communications Ltd. 16.2. 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 16.3. 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 David Robinson Sun Microsystems, Inc. 901 San Antonio Road Palo Alto, CA 94303 Expires: December 1999 [Page 155]
Draft Protocol Specification NFS version 4 June 1999 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: December 1999 [Page 156]
Draft Protocol Specification NFS version 4 June 1999 17. 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: December 1999 [Page 157]
