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Versions: 00 01 02 03                                                   
Network Working Group                                        S. Shepler
Internet Draft                                              August 1998
Document: draft-shepler-nfsv4-02.txt



                         NFS version 4 Strawman



Status of this Memo

   This document is an Internet-Draft.  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."

   To view the entire list of current Internet-Drafts, please check the
   "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow
   Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern
   Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific
   Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast).

Abstract

   NFS version 4 is meant to be a further revision of the NFS protocol
   defined already by versions 2 and 3.  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.

   This strawman is being offered as a starting point for future
   discussions and work on NFS version 4.  The document contains ideas
   presented and discussed via email at nfsv4-wg@sunroof.eng.sun.com.
   Additional content has been added in areas with the intent of
   offering more suggestions for future discussion.

   Goals for NFS version 4 include: strong security, access and good
   performance via the Internet, cross-platform interoperability, and
   protocol extensibility.






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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
   2.  RPC and Security Flavor  . . . . . . . . . . . . . . . . . . 5
   2.1.  Ports and Transports . . . . . . . . . . . . . . . . . . . 5
   2.2.  Security Flavors . . . . . . . . . . . . . . . . . . . . . 5
   2.2.1.  Security mechanisms for NFS version 4  . . . . . . . . . 5
   2.3.  Security Negotiation . . . . . . . . . . . . . . . . . . . 6
   2.3.1.  Security Error . . . . . . . . . . . . . . . . . . . . . 6
   2.3.2.  SECINFO  . . . . . . . . . . . . . . . . . . . . . . . . 6
   2.4.  Alternate Negotiation Technique - SPNEGO . . . . . . . . . 6
   3.  File handles . . . . . . . . . . . . . . . . . . . . . . . . 7
   3.1.  Obtaining the first file handle  . . . . . . . . . . . . . 7
   3.2.  The persistent and volatile file handle  . . . . . . . . . 7
   4.  Basic Data Types . . . . . . . . . . . . . . . . . . . . . . 9
   5.  File Attributes  . . . . . . . . . . . . . . . . . . . . .  11
   5.1.  Defining Attributes  . . . . . . . . . . . . . . . . . .  12
   5.2.  File Attribute Bits  . . . . . . . . . . . . . . . . . .  12
   6.  Defined Error Numbers  . . . . . . . . . . . . . . . . . .  20
   7.  Compound Requests  . . . . . . . . . . . . . . . . . . . .  24
   8.  NFS Version 4 Requests . . . . . . . . . . . . . . . . . .  25
   8.1.  Evaluation of a Compound Request . . . . . . . . . . . .  25
   9.  NFS Version 4 Procedures . . . . . . . . . . . . . . . . .  26
   9.1.  Procedure 0: NULL - No operation . . . . . . . . . . . .  27
   9.2.  Procedure 1: ACCESS - Check Access Permission  . . . . .  28
   9.3.  Procedure 2: COMMIT - Commit cached data . . . . . . . .  31
   9.4.  Procedure 3: CREATE - Create a filesystem object . . . .  34
   9.5.  Procedure 4: GETATTR - Get attributes  . . . . . . . . .  38
   9.6.  Procedure 5: GETFH - Get current filehandle  . . . . . .  39
   9.7.  Procedure 6: LINK - Create link to an object . . . . . .  40
   9.8.  Procedure 7: LOCKR - Create a read lock  . . . . . . . .  42
   9.9.  Procedure 8: LOCKW - Create write lock . . . . . . . . .  44
   9.10.  Procedure 9: LOCKT - test for lock  . . . . . . . . . .  46
   9.11.  Procedure 10: LOCKX - validate and extend lock  . . . .  47
   9.12.  Procedure 11: LOCKU - Unlock file . . . . . . . . . . .  49
   9.13.  Procedure 12: LOOKUP - Lookup filename  . . . . . . . .  50
   9.14.  Procedure 13: LOOKUPP - Lookup parent directory . . . .  52
   9.15.  Procedure 14: NVERIFY - Verify attributes different . .  53
   9.16.  Procedure 15: RESTOREFH - Restore saved filehandle  . .  54
   9.17.  Procedure 16: SAVEFH - Save current filehandle  . . . .  55
   9.18.  Procedure 17: PUTFH - Set current filehandle  . . . . .  56
   9.19.  Procedure 18: PUTROOTFH - Set root filehandle . . . . .  57
   9.20.  Procedure 19: READ - Read from file . . . . . . . . . .  58
   9.21.  Procedure 20: READDIR - Read directory  . . . . . . . .  60
   9.22.  Procedure 21: READLINK - Read symbolic link . . . . . .  63
   9.23.  Procedure 22: REMOVE - Remove filesystem object . . . .  65
   9.24.  Procedure 23: RENAME - Rename directory entry . . . . .  67
   9.25.  Procedure 24: SETATTR - Set attributes  . . . . . . . .  69



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   9.26.  Procedure 25: VERIFY - Verify attributes same . . . . .  71
   9.27.  Procedure 26: WRITE - Write to file . . . . . . . . . .  72
   9.28.  Procedure 27: SECINFO - Obtain Available Security . . .  76
   10.  Locking notes . . . . . . . . . . . . . . . . . . . . . .  78
   10.1.  Short and long leases . . . . . . . . . . . . . . . . .  78
   10.2.  Clocks and leases . . . . . . . . . . . . . . . . . . .  78
   10.3.  Locks and lease times . . . . . . . . . . . . . . . . .  79
   10.4.  Lease scalability . . . . . . . . . . . . . . . . . . .  79
   10.5.  Rejecting write locks and denial of service . . . . . .  79
   10.6.  Locking of directories and other meta-files . . . . . .  79
   10.7.  Proxy servers and leases  . . . . . . . . . . . . . . .  79
   10.8.  Archive updates and lease time adjustment . . . . . . .  79
   10.9.  Locking and the new latency . . . . . . . . . . . . . .  80
   11.  NFS Version 4 RPC definition file . . . . . . . . . . . .  81
   12.  Bibliography  . . . . . . . . . . . . . . . . . . . . . .  99
   13.  Author's Address  . . . . . . . . . . . . . . . . . . . .  102



































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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.














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2.  RPC and Security Flavor

   The NFS version 4 protocol will use the Remote Procedure Call (RPC)
   version 2 and corresponding eXternal Data Representation (XDR) as
   defined in [RFC1831] and [RFC1832].  The RPCSEC_GSS security flavor
   as defined in [RFC2203] will 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.  The NFS
   server should use port 2049 as a means to ease the use of NFS through
   firewalls.  This means that for NFS version 4 services the client
   will not need to use the RPC binding protocols as described in
   [RFC1833].

   The NFS server, at a minimum, must offer its RPC service via the TCP
   transport. The use of UDP for RPC service offering should also be
   present if applicable.  The NFS client should have a preference for
   TCP usage but should 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.

2.2.1.  Security mechanisms for NFS version 4

   As a goal of the NFS version 4 work, adding stronger security to the
   protocol definition is required.  The use of RPCSEC_GSS will require
   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.

        NOTE: Kerberos-V5 has been suggested as one of the security
        mechanisms.  Another mechanism should be chosen and should
        be a public key based system so as to complement the
        Kerberos-V5 selection.





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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
   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.

2.4.  Alternate Negotiation Technique - SPNEGO

   It has also been suggested that the SPNEGO protocol defined in
   [SPNEGO] would also be available for use with RPCSEC_GSS.  However,
   this seems to imply that the NFS server would need to offer all of
   its resources under the same security mechanism.  This needs to be
   evaluated further as an alternative.




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3.  File handles

   The file handle in the NFS protocol is an opaque identifier for a
   file system object.  The server is responsible for translating the
   file handle to its internal representation of the file system object.
   The file handle is uniquely identifies a file system object at the
   NFS server.  The client should be able to depend on the fact that a
   file handle will not be reused once a file system object has been
   destroyed.  If the file handle is reused, the time elapsed before
   reuse will be very significant. Note that each NFS procedure is
   defined in terms of its file handle(s) except for the NULL procedure.

3.1.  Obtaining the first file handle

   If each of the meaningful operations of the NFS protocol require a
   file handle, the client must have a mechanism to obtain the first
   file handle.  With NFS version 2 [RFC1094] and NFS version 3
   [RFC1813], there exists an ancillary, protocol to obtain the 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 as currently implemented 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 [add references to RFCs
   for WebNFS].  The public file handle is a special case file handle
   that is used in combination with a path name to avoid using the MOUNT
   protocol for obtaining the first file handle.  With the introduction
   and use of the public file handle in the previous versions of NFS, it
   has been shown that the MOUNT protocol is unnecessary for viable
   interaction between the client and server with the use of file
   handles.

3.2.  The persistent and volatile file handle

   For the first time in NFS version 4, the file handle constructed by
   the server can be volatile.  In the previous versions of NFS, the
   server was responsible for ensuring the persistence of the file
   handle.  This meant that as long as a file system object remained in
   existence at the server the file handle for that object had to be the
   same each time the client asked for it.  This persistent quality
   eased the implementation at the client in the event of server restart
   or failure and recovery.  For some servers, fulfilling the persistent
   requirement has been straight forward; for others it has been
   difficult and affected at best performance and at worst correctness.

   The existence of the volatile file handle requires the client to
   implement a method of recovering from the expiration of a file



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   handle.  Most commonly the client will need to store the component
   names associated with the file system object in question.  With these
   names, the client will 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.

   The use of a volatile file handle provides these advantages:

   o    Allows or eases the server implementation requirements

   o    Server can provide extended services more easily with the use of
        volatile file handles (HSM software, file system reorganization)

   o    Others???


        NOTE: Need to describe a method of identifying a file
        handle as persistent or volatile (In the file handle
        itself?).  Also need a discussion of when and where a each
        type of file handle would be used.  Also need to extend the
        list of examples of what things volatile file handles
        enable (or remove the list altogether).



        Note: A question has arisen about the server's ability to
        return a correct error code (NFS4ERR_STALE vs.
        NFS4ERR_EXPIRED).  One implementation that has been
        suggested is the following.  A volatile file handle, while
        opaque to the client could contain:

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

        slot is an index in the server volatile file handle table.
        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).

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





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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.

   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
        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



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        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.

        Note: This is used for the rdev attribute.  Is this the
        correct representation or should this be considered an
        extended/named attribute for a file.  Is there some other
        solution?



























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5.  File Attributes

   Previous versions of the NFS protocol supported only the set of POSIX
   file attributes.


                    Posix        V2 Fattr    V3 Fattr3
                    -----        --------    ---------

                    -            type        type
                    st_mode      mode        mode
                    st_ino       fileid      fileid
                    st_dev       fsid        fsid
                    st_rdev      rdev        rdev
                    st_nlink     nlink       nlink
                    st_uid       uid         uid
                    st_gid       gid         gid
                    st_size      size        size
                    -            -           used
                    st_atime     atime       atime
                    st_mtime     mtime       mtime
                    st_ctime     ctime       ctime
                    st_blksize   blocks      -
                    st_blocks    blocksize   -



   This fixed set of attributes has been limiting:


   o    There is no way to add new attributes without revising the
        protocol.  This penalizes file systems and/or operating systems
        that support attributes that do not map into the POSIX set.

   o    Not all file systems or operating systems support the full range
        of POSIX attributes.  The server is required to "invent"
        approximate values for attributes that it does not support. The
        client does not know that the server doesn't support these
        values.

   o    Attributes cannot be obtained individually. If the client needs
        to obtain only one attribute it must request them all.  Some of
        those attributes may be computationally expensive for the server
        to return.

   o    The set of supported attributes may vary depending on the type
        of file system object.  Additionally, previous versions of the
        protocol required multiple attribute spaces for files (GETATTR)



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        and file systems (FSINFO, FSSTAT, PATHCONF) which heavily
        favored POSIX-based file systems.

   To overcome these limitations NFS version 4 supports an attribute
   model with the following features:

   o    Extensibility.  New attributes can be added in incremental
        revisions of the protocol.

   o    For each file system object the client can determine which
        attributes are supported.

   o    The client can select the attributes it needs.



5.1.  Defining Attributes

   Each attribute is assigned a unique integer which corresponds to a
   position in a bitmap.  When requesting or setting attributes the
   client sets the appropriate bits in the bitmap to identify the
   attributes.  Similarly, when returning attributes the server returns
   a bitmap that identifies the attributes returned. The sequence of
   attributes in a request or reply must follow the

5.2.  File Attribute Bits


   Name:         type

   Data type:    uint32

   Description:  Type of file.



        Note: Some of these are now handled by accessbits.  Need to
        represent Unix perm bits as an ACL


   Name:         mode

   Data type:    uint32

   Description:  Protection mode bits

   The mode bits are defined as follows:




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            0x00800   Set user ID on execution.
            0x00400   Set group ID on execution.
            0x00200   Save swapped text (not defined in POSIX).
            0x00100   Read permission for owner.
            0x00080   Write permission for owner.
            0x00040   Execute permission for owner on a file.
                      Or lookup (search) permission for owner
                      in directory.
            0x00020   Read permission for group.
            0x00010   Write permission for group.
            0x00008   Execute permission for group on a file.
                      Or lookup (search) permission for group
                      in directory.
            0x00004   Read permission for others.
            0x00002   Write permission for others.
            0x00001   Execute permission for others on a file.
                      Or lookup (search) permission for others
                      in directory.




   Name:         accessbits

   Data type:    uint32

   Description:




            0x0001   READ.
                     Read data from file or read a directory.
            0x0002   LOOKUP.
                     Look up a name in a directory (no meaning
                     for non-directory objects).

            0x0004   MODIFY.
                     Rewrite existing file data or modify
                     existing directory entries.

            0x0008   EXTEND.
                     Write new data or add directory entries.

            0x0010   DELETE.
                     Delete an existing directory entry.

            0x0020   EXECUTE.



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                     Execute file (no meaning for a directory).



   Name:         nlink

   Data type:    uint32

   Description:  Number of hard links to the file - that is, the number
                 of different names for the same file.  If a
                 modification is made to data within a file and the file
                 has a nlink value greater than 1, then the
                 modifications will appear under each of the names for
                 the file.



   Name:         uid

   Data type:    utf8string

   Description:  Identifier of the owner of the file.



   Name:         gid

   Data type:    utf8string

   Description:  Identifier of the group of the file.


        NOTE: The string representation for the user and group
        identifiers of a file are provided to include support for
        user identifiers beyond the scope of the traditional Unix
        uid/gid name space.  The contents of the user and group
        identifier should be defined or have strong
        recommendations.  One suggestion for user identifier might
        be user@domain.  To translate a traditional Unix uid the
        representation may be something like 123456@uid.



   Name:         size

   Data type:    uint64

   Description:  Size of the file in bytes.



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   Name:         used

   Data type:    uint64

   Description:  Number of bytes of disk space that the file actually
                 uses (which can be smaller because the file may have
                 holes or it may be larger due to fragmentation).



   Name:         rdev

   Data type:    specdata4

   Description:  Describes the device file if the file type is NF4CHR or
                 NF4BLK.  For all other file types, this attribute is
                 undefined.  If this attribute is returned from the
                 server for file types other than NF4CHR and NF4BLK, the
                 client should consider the values to be zero.



   Name:         fsid

   Data type:    uint64

   Description:  The file system identifier for the file system.  This
                 identifier is expected to uniquely identify the file
                 system at the server.


        NOTE: The unique quality of the fsid will indicate to the
        client that certain operations will fail if the source and
        target of the operation are located on different fsids.  A
        RENAME is a good example of this.  If the source and
        destination directories have different fsid values at the
        server then the RENAME operation will fail.  This type of
        failure mode needs to be determined and documented for all
        procedures.



   Name:         fileid

   Data type:    uint32

   Description:  A number which uniquely identifies the file within the
                 file system. On UNIX this would be the inode number.



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        Note: Are the fsid and fileid data types large enough for
        unique identifiers?  Are there environments that something
        more is needed.



   Name:         atime

   Data type:    nfstime4

   Description:  The time when the file data was last accessed.



   Name:         mtime

   Data type:    nfstime4

   Description:  The time when the file data was last modified.



        Note: In the case that a file is updated twice within the
        granularity of the server's mtime, what is the server
        supposed to do?  Is it supposed to increase the mtime
        nseconds field to signify that a change has occurred?  In
        the case that mtime is not kept for certain file system
        objects, what is the server supposed to do with the object
        is updated?  Is mtime sufficient or should there be another
        opaque attribute that can be used by the server to fulfill
        the client's need to know if the file system object has
        been updated.



   Name:         ctime

   Data type:    nfstime4

   Description:  The time when the attributes of the file were last
                 changed. Writing to the file changes the ctime in
                 addition to the mtime.



   Name:         rtmax

   Data type:    uint32



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   Description:  The maximum size in bytes of a READ request supported
                 by the server. Any READ with a number greater than
                 rtmax will result in a short read of rtmax bytes or
                 less.



   Name:         wtmax

   Data type:    uint32

   Description:  The maximum size of a WRITE request supported by the
                 server.  In general, the client is limited by wtmax
                 since there is no guarantee that a server can handle a
                 larger write. Any WRITE with a count greater than wtmax
                 will result in a short write of at most wtmax bytes.



   Name:         maxfilesize

   Data type:    uint64

   Description:  The maximum size of a file on the file system.



   Name:         time_delta

   Data type:    nfstime4

   Description:  The server time granularity. When setting a file time
                 using SETATTR, the server guarantees only to preserve
                 times to this accuracy. If this is {0, 1}, the server
                 can support nanosecond times, {0, 1000000} denotes
                 millisecond precision, and {1, 0} indicates that times
                 are accurate only to the nearest second.


        Note: Should there be more granularity definitions or a
        general scheme devised for this?  Is this attribute
        necessary at all?  If there are mechanisms to ensure that
        modification times are recorded correctly or at least
        recorded in such a way to signify that a modification has
        occurred, is this attribute needed?






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   Name:         linkmax

   Data type:    uint32

   Description:  The maximum number of hard links to an object.



   Name:         name_max

   Data type:    uint32

   Description:  The maximum length of a component of a filename.



   Name:         change

   Data type:    uint64

   Description:  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 checksum or sequence number.



   Name:         properties

   Data type:    uint32

   Description:  A bit mask of file system properties. The following
                 values are defined:



               FSF_LINK   If this bit is 1 (TRUE), the file system
                          supports hard links.
            FSF_SYMLINK   If this bit is 1 (TRUE), the file system
                          supports symbolic links.
        FSF_HOMOGENEOUS   If this bit is 1 (TRUE), the information
                          in the properties attributes is identical for
                          every file and directory in the file
                          system. If it is 0 (FALSE), the client
                          should retrieve properties information for
                          each file and directory as required.



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         FSF_CANSETTIME   If this bit is 1 (TRUE), the server will
                          set the times for a file via SETATTR if
                          requested (to the accuracy indicated by
                          time_delta). If it is 0 (FALSE), the
                          server cannot set times as requested.
            FSF_NOTRUNC   If this bit is 1 (TRUE), the server will
                          reject any request that includes a name longer
                          than name_max with the error,
                          NFS4ERR_NAMETOOLONG.  If FALSE, any length
                          name over name_max bytes will be silently
                          truncated to name_max bytes.
   FSF_CHOWN_RESTRICTED   If this bit is 1 (TRUE), the server
                          will reject any request to change either the
                          owner or the group associated with a file if
                          the caller is not the privileged user. (UID 0)
   FSF_CASE_INSENSITIVE   If this bit is 1 (TRUE), the server
                          file system does not distinguish case when
                          interpreting filenames.
    FSF_CASE_PRESERVING   If this bit is 1 (TRUE), the server
                          will preserve the case of a name during the
                          creation of a file system object.
                          (i.e. CREATE, MKDIR, MKNOD, SYMLINK, RENAME
                          or LINK operation)



        For FSF_CHOWN_RESTRICTED, what should be done with the
        privileged user definition in face of a non-numeric
        uid/gid.






















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6.  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_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 is
                       accepted.


   NFS4ERR_EXIST       File exists. The file specified already exists.



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   NFS4ERR_XDEV        Attempt to do a cross-device hard link.


   NFS4ERR_NODEV       No such device.


   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.





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


   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.


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


   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



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                       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_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_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.


























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7.  Compound Requests

   NFS version 4 allows a client to combine multiple NFS operations into
   a single request.  Compound requests provide:

   o    Good performance on high latency networks

        If a client can combine multiple, dependent operations into a
        single request then it can avoid the cumulative latency in many
        request/response round-trips across the network.  This is
        particularly important on the Internet or through geosynchronous
        satellite connections.


   o    Protocol simplification

        Clients can build NFS requests of arbitrary complexity from more
        primitive operations.  These requests can be tailored to the
        unique needs of each client.

   A compound request looks like this:

                  +-----------+-----------+-----------+--
                  | 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.

















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8.  NFS Version 4 Requests

   Nearly all NFS version 4 operations are defined as compound
   operations - not as RPC procedures.  There is a single RPC procedure
   for all compound requests.

        NOTE: Let's imagine procedure 1 is defined as a compound
        request.  Procedure 2 might be a proxied compound request,
        i.e. a compound request with a header that identifies the
        target server.


8.1.  Evaluation of a Compound Request


        NOTE: A useful initial prefix on a compound request
        sequence would be a string that summarizes the content of
        the compound request for the benefit of packet sniffers
        like snoop and engineers debugging implementations.


   The server evaluates the operations in sequence.  Each operation
   consists of a 32 bit operation code, followed by a sequence of
   arguments 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 fails a non-zero status code
   will be encoded, evaluation of the compound request will halt, and
   the reply will be returned.

   The client is responsible 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.















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9.  NFS Version 4 Procedures


















































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9.1.  Procedure 0: NULL - No operation


   SYNOPSIS

      (cfh) -> (cfh)

   ARGS

      (none)

   RESULTS

      (none)

   DESCRIPTION

      The server does no work other than to return a NFS_OK result in
      the reply.

   ERRORS

      (none)




























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9.2.  Procedure 1: ACCESS - Check Access Permission



   SYNOPSIS

      (cfh), permbits -> permbits

   ARGS

      permbits: uint32

   RESULTS

      permbits: uint32

   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.

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




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      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
      series of operations. This is useful in operating systems (such as
      UNIX) where permission checking is done only when a file or
      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.

      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.



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   ERRORS

      NFS4ERR_IO

      NFS4ERR_SERVERFAULT

   SEE

      GETATTR.










































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9.3.  Procedure 2: COMMIT - Commit cached data


   SYNOPSIS

      (cfh), offset, count -> verifier

      Procedure COMMIT forces or flushes data to stable storage that was
      previously written with a WRITE operation with the stable field
      set to UNSTABLE.

   ARGS

      offset: uint64

      The position within the file at which the flush is to begin.  An
      offset of 0 means to flush data starting at the beginning of the
      file.

      count: uint32

      The number of bytes of data to flush. If count is 0, a flush from
      offset to the end of file is done.

   RESULTS

      verifier: uint32

      This is a cookie that the client can use to determine whether the
      server has rebooted between a call to WRITE and a subsequent call
      to COMMIT. This cookie must be consistent during a single boot
      session and must be unique between instances of the NFS version 4
      protocol server where uncommitted data may be lost.

   IMPLEMENTATION

      Procedure COMMIT is similar in operation and semantics to the
      POSIX fsync(2) system call that synchronizes a file's state with
      the disk, that is it flushes the file's data and metadata to disk.
      COMMIT performs the same operation for a client, flushing any
      unsynchronized data and metadata on the server to the server's
      disk 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 will always return NFS4_OK,
      unless there has been an unexpected error.

      COMMIT differs from fsync(2) in that it is possible for the client



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      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 verf verifier.  The other reason for the client
      to generate a COMMIT is for a full file flush, such as may be done
      at 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.

      This implementation will require some modifications to the buffer
      cache on the client. After a buffer is written with stable
      UNSTABLE, it must be considered as dirty by the client system
      until it is either flushed via a COMMIT operation or written via a
      WRITE operation with stable 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 that contains an unexpected verf, 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 flag. If there more than one, it might be
      worthwhile retransmitting all of the buffers in WRITE requests
      with stable set to UNSTABLE and then retransmitting the COMMIT
      operation to flush all of the data on the server to stable



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      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

   SEE

      WRITE.




































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9.4.  Procedure 3: CREATE - Create a filesystem object


   SYNOPSIS

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

   ARGS

      name: utf8string

      objtype: filetype

      how: union

         UNCHECKED:
         GUARDED:

             attrbits: bitmap
             attrvals

         EXCLUSIVE:

             verifier: createverf

   RESULTS

      (cfh): filehandle

   DESCRIPTION

      Procedure CREATE creates an object in a directory with a given
      name.  The objtype determines the type of object to be created:
      directory, regular file, 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. GUARDED
      specifies that the server should check for the presence of a
      duplicate object before performing the create and should fail the
      request with NFS4ERR_EXIST if a duplicate object exists. If the
      object does not exist, the request is performed as described for
      UNCHECKED.  EXCLUSIVE specifies that the server is to follow
      exclusive creation semantics, using the verifier to ensure
      exclusive creation of the target. No attributes may be provided in
      this case, since the server may use the target object metadata to
      store the verifier.




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      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
      metadata 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 metadata (time stamps) of the
      object. For this reason, an exclusive object create may not
      include initial attributes because the server would have nowhere
      to store the verifier.

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

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

      Once the client has performed a successful exclusive create, it
      must issue a SETATTR to set the correct object attributes.  Until
      it does so, it should not rely upon any of the object attributes,



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      since the server implementation may need to overload object
      metadata 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.

        3. The presence of a generic create for
           multiple filetypes makes the protocol
           easier to extend to new filetypes in
           a minor rev (without defining new ops)

        4. The specific exclusive create semantics can be
           removed if there is guaranteed support for extended
           attributes.  The client could specify the verifier
           be stored in an extended attribute and then check
           the attribute value itself instead of relying on the
           server to do so.


   ERRORS

      NFS4ERR_IO

      NFS4ERR_ACCES

      NFS4ERR_EXIST

      NFS4ERR_NOTDIR

      NFS4ERR_NOSPC




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      NFS4ERR_ROFS

      NFS4ERR_NAMETOOLONG

      NFS4ERR_DQUOT

      NFS4ERR_NOTSUPP

      NFS4ERR_SERVERFAULT










































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9.5.  Procedure 4: GETATTR - Get attributes


   SYNOPSIS

      (cfh), attrbits -> attrbits, attrvals

   ARGS

      attrbits: bitmap

   RESULTS

      attrbits: bitmap

      attrvals: sequence of attributes

   DESCRIPTION

      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 that 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.

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

   IMPLEMENTATION

      ?

   ERRORS

      NFS4ERR_IO

      NFS4ERR_SERVERFAULT





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9.6.  Procedure 5: GETFH - Get current filehandle



   SYNOPSIS

         (cfh) -> filehandle


   ARGS



   RESULTS

         filehandle: filehandle


   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 will do it:


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


   IMPLEMENTATION

      ?

   ERRORS

      NFS4ERR_SERVERFAULT












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9.7.  Procedure 6: LINK - Create link to an object


   SYNOPSIS

      (cfh), dir, newname -> (cfh)

   ARGS

      dir: filehandle

      newname: utf8string

   RESULTS

      (none)


   DESCRIPTION

      Procedure LINK 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. On entry, the arguments
      in LINK3args are:

   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

      NFS4ERR_ACCES

      NFS4ERR_EXIST

      NFS4ERR_XDEV

      NFS4ERR_NOTDIR



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      NFS4ERR_INVAL

      NFS4ERR_NOSPC

      NFS4ERR_ROFS

      NFS4ERR_MLINK

      NFS4ERR_NAMETOOLONG

      NFS4ERR_DQUOT

      NFS4ERR_NOTSUPP

      NFS4ERR_SERVERFAULT




































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9.8.  Procedure 7: LOCKR - Create a read lock


   SYNOPSIS

      (cfh), id, offset, length -> lease

   ARGS

      id: uint64

      offset: uint64

      length: uint64

   RESULTS

      lease: uint32

   DESCRIPTION

      Requested by a client that needs to protect a file extent from
      change.  Other clients may have read locks that overlap the extent
      completely or partially but no other client or server process will
      be allowed to modify or create an overlapping write lock on the
      extent until there are no read or write locks covering any part of
      the extent.  A write lock will be granted only when the leases for
      conflicting locks have expired, or because all clients have
      removed their locks. The locked extent is permitted to lie
      partially or completely beyond the end of the file. The id is a
      64-bit value that the client provides to uniquely identify its
      lock. The server will attempt to match this value with a
      subsequent LOCKX or LOCKU request.

      A read-lock will receive an NFS4_DENIED error if another client
      has requested a write-lock or is holding a write lock on any part
      of the requested extent.  The returned lease time is the time
      remaining on the lock-holder's lease.


   IMPLEMENTATION

      A read lock is mandatory.  The server must prevent other clients
      or local processes from changing the locked extent of the file
      while the read lock is held.

      A duplicate read-lock request must be treated as an idempotent
      operation and must not return an error.



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      A LOCKR may be combined with a READ in a compound request so that
      the data be locked and read in a single operation:

              1: PUTFH 0x12345
              2: LOCKR 123  0,8192
              3: READ       0,8192

      or perhaps

              1: PUTFH 0x12345
              2: READ       0,8192
              3: LOCKR 123  0,8192

      allowing the client to read the data unconditionally yet change
      its caching strategy depending on whether the lock is granted.

   ERRORS

      NFS4ERR_DENIED

      NFS4ERR_IO

      NFS4ERR_NXIO

      NFS4ERR_ACCES

      NFS4ERR_INVAL

      NFS4ERR_SERVERFAULT






















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9.9.  Procedure 8: LOCKW - Create write lock


   SYNOPSIS

      (cfh) id, offset, length -> lease

   ARGS

      id: uint64

      offset: uint64

      length: uint64

   RESULTS

      lease: uint32

   DESCRIPTION

      Requested by a client that needs to change a file.  While a write
      lock is held, no other client can read the locked extent or obtain
      either a read lock or a write lock for the same extent. The locked
      extent is permitted to lie partially or completely beyond the end
      of the file. The id is a 64-bit value that the client provides to
      uniquely identify the lock.  The server will attempt to match this
      value with a subsequent LOCKX or LOCKU request.

      An NFS4ERR_DENIED error will be returned if one or more other
      clients are holding a read or write lock on any part of the
      requested extent.  The client should continue to retransmit the
      lock request (using exponential backoff to avoid server overload)
      until the request is granted. The client will not be granted a
      write lock for an extent that overlaps an extent that it has write
      locked previously. When the server rejects a write lock request it
      should prevent clients from renewing or obtaining new read locks
      for the same file for some reasonable period of time. This policy
      prevents write starvation.

   IMPLEMENTATION

      The server might employ a "fairness" scheme to arbitrate between
      multiple clients attempting write locks, e.g. client lock requests
      be ordered so that the first requester is given the preference
      window when the write lock becomes available.

        NOTE: Could get some interesting dynamics here where there



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        is much contention for read and write locks on a single
        file.  I haven't begun to think about possible problems
        when a file becomes popular.  I'm concerned that we keep
        the protocol simple and easy to understand - leaving
        implementations to focus on topics like "fairness" and
        "performance."


   A LOCKW may be combined with a READ in a compound request followed by
   a subsequent combination of WRITE and LOCKU where the client writes
   back the updated record/file, e.g.

           1: PUTFH 0x12345
           2: LOCKW 123  0,8192
           3: READ       0,8192


   Client updates data, then

           1: PUTFH 0x12345
           2: LOCKX 123   0,8192
           3: WRITE       0,8192
           4: LOCKU 123   0,8192

   Note the use of a LOCKX to abort the transaction if the lock has been
   lost. It also seems a reasonable requirement that if a lOCKX is
   granted that it be valid for at least the duration of the compound
   request.

   ERRORS

      NFS4ERR_DENIED

      NFS4ERR_ACCES

      NFS4ERR_SERVERFAULT















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9.10.  Procedure 9: LOCKT - test for lock


   SYNOPSIS

      (cfh), offset, length -> lockstate

   ARGS

      offset: uint64

      length: uint64

   RESULTS

      lockstate: uint32

   DESCRIPTION

      Requested by a client that needs to establish whether any part of
      an extent in a file is locked.  The server returns one of three
      lock states:

              0 - Unlocked
              1 - Read lock held
              2 - Write lock held


   ERRORS

      NFS4ERR_ACCES

      NFS4ERR_SERVERFAULT


















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9.11.  Procedure 10: LOCKX - validate and extend lock


   SYNOPSIS

      (cfh) id, offset, length, locktype -> lease

   ARGS

      id: uint64

      offset: uint64

      length: uint64

      locktype: enum { READLOCK | WRITELOCK }

   RESULTS

      lease: uint32

   DESCRIPTION

      Requested by a client that wishes to extend the lease on a read or
      write lock. The id, offset, and length must match a previous
      successful LOCKR or LOCKW request. If successful, the server
      returns the remaining time for the new lease. A LOCKX operation
      must precede any READ or WRITE operation in the compound request
      that assumes the extent is locked.  This serves two purposes: it
      assures the client that the server is still holding the lock (the
      server may have lost the lock for some reason) and it validates to
      the server that the client holds the lock. Without this validation
      the server will deny any read or write request on a locked file.

      An NFS4ERR_EXPIRED error means that the server has lost the lock,
      or that the client's lease expired before the client could renew
      it.  The client must take appropriate recovery action and request
      a new lease. A lease could expire if the client attempted a lock
      extension close to the expiry time and the request was lost or
      dropped.  In that case the retransmission of the extension request
      might arrive at the server after expiry.

   IMPLEMENTATION

      Even though an extension request might arrive after expiry, a
      benevolent server may grant the extension if it notices that there
      have been no other changes to the file since the expiry.




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      Note the server may acknowledge the ownership of the lock but deny
      a lease extension.  In this case the lease time returned will be
      the time remaining on the original lease.

      The server must implement a "grace" period after a crash in which
      it will monitor all requests but respond to none. During the grace
      period information from LOCKX operations will be used to rebuild
      lock state.

        NOTE: Assumption here that if the server can recover very
        quickly, well within the lease times, then it might use the
        client's renewal requests to recover lock state.  In the
        case where clients are unable to extend leases because the
        server is down and their leases expire, they should
        continue to attempt lease extensions in the hope that the
        grace period will allow recovery.  The worst that can
        happen is that they miss the grace period, or that they
        lost the lease because of network partition (or server
        overload) and the lease extension is denied.


   ERRORS

      NFS4ERR_EXPIRED

      NFS4ERR_ACCES

      NFS4ERR_SERVERFAULT























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9.12.  Procedure 11: LOCKU - Unlock file


   SYNOPSIS

      (cfh) id, offset, length -> -

   ARGS

      id: uint64

      offset: uint64

      length: uint64

   DESCRIPTION

      Unlock read or write lock for a file extent.  The id, offset, and
      length must match that of a previous successful LOCKR or LOCKW
      request.

      An NFS4ERR_EXPIRED error means that the server has no knowledge of
      the client's lock - most likely the lease expired.  In this
      situation the client may choose to take some recovery action.

   ERRORS

      NFS4ERR_EXPIRED

      NFS4ERR_ACCES

      NFS4ERR_SERVERFAULT



















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9.13.  Procedure 12: LOOKUP - Lookup filename


   SYNOPSIS

      (cfh), filenames -> (cfh)

   ARGS

      filename: utf8string[]

   RESULTS

      (none)

   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

      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



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      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_IO

      NFS4ERR_NOENT

      NFS4ERR_ACCES

      NFS4ERR_NOTDIR

      NFS4ERR_NAMETOOLONG

      NFS4ERR_SERVERFAULT

   SEE

      CREATE











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9.14.  Procedure 13: LOOKUPP - Lookup parent directory


   SYNOPSIS

      (cfh) -> (cfh)

   ARGS

      (none)

   RESULTS

      (none)

   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_IO

      NFS4ERR_NOENT

      NFS4ERR_ACCES

      NFS4ERR_SERVERFAULT

   SEE

      CREATE












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9.15.  Procedure 14: NVERIFY - Verify attributes different


   SYNOPSIS

      (cfh), attrbits, attrvals -> -

   ARGS

      attrbits: bitmap

      attrvals: sequence of attributes


   RESULTS

      (none)

   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


   ERRORS

      NFS4ERR_IO

      NFS4ERR_ACCES

      NFS4ERR_SERVERFAULT

      NFS4ERR_SAME



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9.16.  Procedure 15: RESTOREFH - Restore saved filehandle


   SYNOPSIS

      (sfh) -> (cfh)

   ARGS

      (none)

   RESULTS

      (none)

   DESCRIPTION

      Make the saved filehandle the current filehandle.  If there is no
      saved filehandle then return an error NFS4ERR_INVAL.

   IMPLEMENTATION

      Operators like CREATE 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)


   ERRORS

      NFS4ERR_SERVERFAULT










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9.17.  Procedure 16: SAVEFH - Save current filehandle


   SYNOPSIS

      (cfh) -> (sfh)

   ARGS

      (none)

   RESULTS

      (none)

   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

      (see RESTOREFH)

   ERRORS

      NFS4ERR_SERVERFAULT























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9.18.  Procedure 17: PUTFH - Set current filehandle


      SYNOPSIS

           filehandle -> (cfh)

      ARGS

           filehandle: filehandle

      RESULTS

           (none)

      DESCRIPTION

         Replaces the current filehandle with the filehandle
         provided as an argument.  If no filehandle has previously
         been installed as the current filehandle then root filehandle
         is assumed. If the length of the filehandle is zero, it is
         recognized by the server as a "public" filehandle.

      IMPLEMENTATION

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

      ERRORS
         NFS4ERR_BADHANDLE
         NFS4ERR_SERVERFAULT




















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9.19.  Procedure 18: PUTROOTFH - Set root filehandle


   SYNOPSIS

      - -> (cfh)

   ARGS

      (none)

   RESULTS

      (none)

   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



















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9.20.  Procedure 19: READ - Read from file


   SYNOPSIS

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

   ARGS

      offset: uint64

      count: uint32

   RESULTS

      eof: bool

      data: opaque <>

   DESCRIPTION

      READ reads data from the file identified by the current
      filehandle.

      offset

           The position within the file at which the read is to begin.
           An offset of 0 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 count set
           to 0 and eof set to TRUE, subject to access permissions
           checking.

      count

           The number of bytes of data that are to be read. If count is
           0, the READ will succeed and return 0 bytes of data, subject
           to access permissions checking. count must be less than or
           equal to the value of the rtmax for the file system that
           contains file. If greater, the server may return only rtmax
           bytes, resulting in a short read.

      If the operation is successful the results are:

      eof

           If the read ended at the end-of-file (formally, in a
           correctly formed READ request, if offset + count is equal to



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           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.

      data

           The counted data read from the file.

   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_LOCKED

      NFS4ERR_SERVERFAULT











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9.21.  Procedure 20: READDIR - Read directory


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

   ARGS

      cookie: uint64

           This should be set to 0 in the first request to read the
           directory. On subsequent requests, it should be a cookie as
           returned by the server.

      dircount: uint32

           The maximum number of bytes of directory information
           returned. This number should not include the size of the
           attributes and file handle portions of the result.

      maxcount: uint32

           The maximum size of the result in bytes.  The size must
           include all XDR overhead. The server is free to return less
           than count bytes of data.

      attrbits: bitmap

           The attributes to be returned for each directory entry.

   RESULTS

      A list of directory entries.  Each entry contains:

      cookie: uint64

           A value recognized by the server as a "bookmark" into the
           directory.  It may be an offset or an index into a table.
           Ideally, the cookie value should not change if the directory
           is modified.

      filename: utf8string;

           The name of the directory entry.

      attrbits: bitmap




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           A bitmap that indicates which attributes follow.  Ideally
           this bitmap will be identical to the attribute bitmap in the
           arguments, i.e. the server returns everything the client
           asked for.  However, the returned bitmap may be different if
           the server does not support the attribute or if the attribute
           is not valid for the filetype.

        Note: need to consider the file handle as an "attribute"
        that may be optionally returned. The concept of file handle
        as attribute might also be useful for the CREATE of a hard
        link.


   DESCRIPTION

      Procedure READDIR 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.

   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.
      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



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      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_BAD_COOKIE

      NFS4ERR_TOOSMALL

      NFS4ERR_NOTSUPP

      NFS4ERR_SERVERFAULT


























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9.22.  Procedure 21: READLINK - Read symbolic link


   SYNOPSIS

      (cfh) -> linktext

   ARGS

      (none)

   RESULTS

      linktext: utf8string

   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
      interpretation of the data in the symbolic link.

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

   ERRORS

      NFS4ERR_IO

      NFS4ERR_INVAL

      NFS4ERR_ACCES

      NFS4ERR_NOTSUPP




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      NFS4ERR_SERVERFAULT


















































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9.23.  Procedure 22: REMOVE - Remove filesystem object


   SYNOPSIS

      (cfh), filename -> -

   ARGS

      entryname: utf8string

   RESULTS

      (none)

   DESCRIPTION

      REMOVE 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 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



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      NFS4ERR_NAMETOOLONG

      NFS4ERR_ROFS

      NFS4ERR_NOTEMPTY

      NFS4ERR_SERVERFAULT












































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9.24.  Procedure 23: RENAME - Rename directory entry


   SYNOPSIS

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

   ARGS

      oldname: utf8string

      newdir: filehandle

      newname: utf8string

   RESULTS

      status: uint32

   DESCRIPTION

      RENAME renames the directory 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
      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.



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      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

      NFS4ERR_DQUOT

      NFS4ERR_NOTSUPP

      NFS4ERR_SERVERFAULT









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9.25.  Procedure 24: SETATTR - Set attributes


   SYNOPSIS

      (cfh), attrbits, attrvals -> -

   ARGS

      attrbits: bitmap

      attrvals

   DESCRIPTION

      Procedure SETATTR changes one or more of the attributes of a file
      system object on the server. 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 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.

      Changing the size of a file with SETATTR indirectly changes the
      mtime. 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. An error may be returned if the
      server can not store a uid or gid in its own representation of
      uids or gids, respectively.  If the server can only support 32 bit
      offsets and sizes, a SETATTR request to set the size of a file to



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      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_NOSPC

      NFS4ERR_ROFS

      NFS4ERR_DQUOT

      NFS4ERR_SERVERFAULT































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9.26.  Procedure 25: VERIFY - Verify attributes same


   SYNOPSIS

      (cfh), attrbits, attrvals -> -

   ARGS

      attrbits: bitmap

      attrvals

   RESULTS

      (none)

   DESCRIPTION

      This operation 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















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9.27.  Procedure 26: WRITE - Write to file


   SYNOPSIS

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

   ARGS

      offset: uint64

      count: uint32

      stability: uint32

      data: opaque

   RESULTS

      count: uint32

      committed: uint32

      verifier: uint32

   DESCRIPTION

      Write data to the file identified by the current filehandle.
      Arguments are as follows:

      offset

           The position within the file at which the write is to begin.
           An offset of 0 means to write data starting at the beginning
           of the file.

      count

           The number of bytes of data to be written. If count is 0, the
           WRITE will succeed and return a count of 0, barring errors
           due to permissions checking. The size of data must be less
           than or equal to the value of the wtmax attribute for the
           filesystem that contains file.  If greater, the server may
           write only wtmax bytes, resulting in a short write.

      stability




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           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.

      data

              The data to be written to the file.

      If the operation is successful the following results are returned:

      count

           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.

      committed

           The server should return 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 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.

      verifier



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           This 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 mtime of the file to be updated. However, the mtime 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 mtime 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.

      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



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      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_FBIG

      NFS4ERR_DQUOT

      NFS4ERR_NOSPC

      NFS4ERR_ROFS

      NFS4ERR_INVAL

      NFS4ERR_LOCKED

      NFS4ERR_SERVERFAULT







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9.28.  Procedure 27: SECINFO - Obtain Available Security


   SYNOPSIS

      (cfh), filename -> { secinfo }

   ARGS

      filename: utf8string

   RESULTS

      secinfo: secinfo
           This is a link list of security flavors available for the
           supplied file handle and filename.

   DESCRIPTION

      This procedure is used by the client to obtain a list of 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

      This 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_NOENT

      NFS4ERR_IO

      NFS4ERR_ACCES

      NFS4ERR_NAMETOOLONG



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      NFS4ERR_STALE

      NFS4ERR_SERVERFAULT

      NFS4ERR_FHEXPIRED

      NFS4ERR_WRONGSEC












































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10.  Locking notes


10.1.  Short and long leases

   The usual lease trade-offs apply: short leases are good for fast
   server recovery at a cost of increased LOCKX requests, though this
   may not be a factor if we can take advantage of compound requests to
   piggyback LOCKX on normal read and write requests.  If the client is
   not actively doing I/O, perhaps a user editing a locked file, then
   the lOCKX requests become more obvious.

   Longer leases are certainly kinder and gentler to large internet
   servers trying to handle huge numbers of clients. LOCKX 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 expiry before granting new
   locks).

   Assuming that locks are held for very short periods (msec), that
   unlock requests usually get through, that there is usually very
   little lock contention, I'd recommend long leases to keep LOCKX
   requests to a minimum, i.e. leases of one or two minutes.  This seems
   appropriate for an Internet scale - and no problem on Intranets.

10.2.  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 exessively 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 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.



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10.3.  Locks and lease times

   Lock requests do not contain desired lease times.  The server
   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.

10.4.  Lease scalability

   Read locks will be vastly more popular than write locks and will be
   popular for client caching.  A server might easily have a hundred
   thousand concurrent read locks on a single file.  The server doesn't
   need to store individual lease times for each client - only the
   longest lease associated with each locked file.

10.5.  Rejecting write locks and denial of service

   Unrestricted use of locking could certainly asking for denial of
   service attacks.  There's an implicit assumption here that attempts
   to set write locks will be rejected if the client does not have write
   permission for the file.  Similarly for read locks if the client has
   no read permission.

10.6.  Locking of directories and other meta-files

   A question: should directories and/or other filesystem 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.

10.7.  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 ?

10.8.  Archive updates and lease time adjustment

   Regularly-updated archives.  It is common for FTP and HTTP servers on
   the Internet to be updated at regularly scheduled intervals, e.g.  on



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   the hour, daily, or weekly.  These servers could grant extremely long
   leases that get progressively shorter as the update time draws near.
   Clients get to cache efficiently, network and server load is vastly
   reduced, and new data is available as soon as it is updated.  The
   lease times might be randomly skewed across clients to spread the
   update load.  These servers may choose to assign a blanket lease time
   for the entire server or for an entire filesystem.

10.9.  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.
































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11.  NFS Version 4 RPC definition file

   /*
    *      nfs_prot.x
    *
    */

   %#pragma ident  "@(#)nfs_prot.x 1.24    98/08/06"

   /*
    * 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;
   };

   /*
    * Basic data types
    */
   typedef opaque          utf8string<>;
   typedef uint64_t        offset4;
   typedef uint32_t        count4;
   typedef uint32_t        length4;
   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;
   typedef uint64_t        nfs_cookie4;
   typedef utf8string      linktext4;
   typedef opaque          sec_oid4<>;
   typedef uint32_t        qop4;

   typedef uint32_t        fattr4_type;
   typedef uint32_t        fattr4_mode;



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   typedef uint32_t        fattr4_accessbits;
   typedef uint32_t        fattr4_nlink;
   typedef utf8string      fattr4_uid;
   typedef utf8string      fattr4_gid;
   typedef uint64_t        fattr4_size;
   typedef uint64_t        fattr4_used;
   typedef specdata4       fattr4_rdev;
   typedef uint64_t        fattr4_fsid;
   typedef uint64_t        fattr4_fileid;
   typedef nfstime4        fattr4_atime;
   typedef nfstime4        fattr4_mtime;
   typedef nfstime4        fattr4_ctime;
   typedef uint32_t        fattr4_rtmax;
   typedef uint32_t        fattr4_rtpref;
   typedef uint32_t        fattr4_rtmult;
   typedef uint32_t        fattr4_wtmax;
   typedef uint32_t        fattr4_wtpref;
   typedef uint32_t        fattr4_wtmult;
   typedef uint32_t        fattr4_dtpref;
   typedef uint64_t        fattr4_maxfilesize;
   typedef uint64_t        fattr4_change;
   typedef nfstime4        fattr4_time_delta;
   typedef uint32_t        fattr4_properties;
   typedef uint32_t        fattr4_linkmax;
   typedef uint32_t        fattr4_name_max;

   /*
    * 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,



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           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,
           NFS4ERR_DENIED = 10010,
           NFS4ERR_EXPIRED = 10011,
           NFS4ERR_LOCKED = 10012
   };

   enum rpc_flavor4 {
       AUTH_NONE = 0,
       AUTH_SYS = 1,
       AUTH_DH = 2,
       AUTH_KRB4 = 3,
       AUTH_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
   };

   /*
    * LOCKX lock type
    */
   enum lockx_locktype {
       READLOCK = 1,
       WRITELOCK = 2
   };

   /*
    * File access handle
    */
   struct nfs_fh4 {
           opaque data<NFS4_FHSIZE>;
   };




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   /*
    * File types
    */
   enum ftype4 {
           NF4REG = 1,
           NF4DIR = 2,
           NF4BLK = 3,
           NF4CHR = 4,
           NF4LNK = 5,
           NF4SOCK = 6,
           NF4FIFO = 7
   };

   const FATTR4_TYPE               = 1;
   const FATTR4_MODE               = 2;
   const FATTR4_ACCESSBITS         = 3;
   const FATTR4_NLINK              = 4;
   const FATTR4_UID                = 5;
   const FATTR4_GID                = 6;
   const FATTR4_SIZE               = 7;
   const FATTR4_USED               = 8;
   const FATTR4_RDEV               = 9;
   const FATTR4_FSID               = 10;
   const FATTR4_FILEID             = 11;
   const FATTR4_ATIME              = 12;
   const FATTR4_MTIME              = 13;
   const FATTR4_CTIME              = 14;
   const FATTR4_RTMAX              = 15;
   const FATTR4_RTPREF             = 16;
   const FATTR4_RTMULT             = 17;
   const FATTR4_WTMAX              = 18;
   const FATTR4_WTPREF             = 19;
   const FATTR4_WTMULT             = 20;
   const FATTR4_DTPREF             = 21;
   const FATTR4_MAXFILESIZE        = 22;
   const FATTR4_TIME_DELTA         = 23;
   const FATTR4_PROPERTIES         = 24;
   const FATTR4_LINKMAX            = 25;
   const FATTR4_NAME_MAX           = 26;
   const FATTR4_NO_TRUNC           = 27;
   const FATTR4_CHOWN_RESTRICTED   = 28;
   const FATTR4_CASE_INSENSITIVE   = 29;
   const FATTR4_CASE_PRESERVING    = 30;

   /*
    * fattr4_properties bits
    */
   const FSF_LINK                  = 0x00000001;



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   const FSF_SYMLINK               = 0x00000002;
   const FSF_HOMOGENEOUS           = 0x00000004;
   const FSF_CANSETTIME            = 0x00000008;
   const FSF_NOTRUNC               = 0x00000010;
   const FSF_CHOWN_RESTRICTED      = 0x00000020;
   const FSF_CASE_INSENSITIVE      = 0x00000040;
   const FSF_CASE_PRESERVING       = 0x00000080;

   struct bitmap4 {
       uint32_t bits<>;
   };

   struct attrlist {
       opaque attrs<>;
   };

   struct fattr4 {
       bitmap4     attrmask;
       attrlist    attr_vals;
   };

   /*
    * ACCESS: Check access permission
    */
   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 {
       uint32_t    access;
   };

   struct ACCESS4resok {
       uint32_t    access;
   };

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

   /*
    * COMMIT: Commit cached data on server to stable storage



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    */
   struct COMMIT4args {
       offset4     offset;
       count4      count;
   };

   struct COMMIT4resok {
       writeverf4  verf;
   };


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

   /*
    * CREATE: Create a file
    */
   enum createmode4 {
       UNCHECKED   = 0,
       GUARDED     = 1,
       EXCLUSIVE   = 2
   };

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

   struct CREATE4args {
       filename4   name;
       ftype4      objtype;
       createhow4  how;
   };

   union CREATE3res switch (nfsstat4 status) {
   case NFS4_OK:
       void;
   default:
       void;
   };




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   /*
    * GETATTR: Get file attributes
    */
   struct GETATTR4args {
       bitmap4 attr_request;
   };

   struct GETATTR4resok {
       fattr4 obj_attributes;
   };

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

   /*
    * GETFH: Get current filehandle
    */
   struct GETFH4resok {
       nfs_fh4 object;
   };

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

   /*
    * LINK: Create link to an object
    */
   struct LINK4args {
       nfs_fh4 dir;
       filename4 newname;
   };

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

   /*



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    * LOCKR: Create a read lock on a file
    */
   struct LOCKR4args {
       nfs_lockid4 id;
       offset4     offset;
       length4     length;
   };

   struct LOCKR4resok {
       nfs_lease4 lease;
   };

   union LOCKR4res switch (nfsstat4 status) {
   case NFS4_OK:
       LOCKR4resok resok;
   default:
       void;
   };


   /*
    * LOCKW: Create a write lock
    */
   struct LOCKW4args {
       nfs_lockid4 id;
       offset4     offset;
       length4     length;
   };

   struct LOCKW4resok {
       nfs_lease4 lease;
   };

   union LOCKW4res switch (nfsstat4 status) {
   case NFS4_OK:
       LOCKW4resok resok;
   default:
       void;
   };

   /*
    * LOCKT: Test for lock
    */
   struct LOCKT4args {
       offset4     offset;
       length4     length;
   };




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   struct LOCKT4resok {
       nfs_lockstate4 lease;
   };

   union LOCKT4res switch (nfsstat4 status) {
   case NFS4_OK:
       LOCKT4resok resok;
   default:
       void;
   };

   /*
    * LOCKX: validate and extend lock
    */
   struct LOCKX4args {
       nfs_lockid4 id;
       offset4     offset;
       length4     length;
       lockx_locktype locktype;
   };

   struct LOCKX4resok {
       nfs_lockstate4 lease;
   };

   union LOCKX4res switch (nfsstat4 status) {
   case NFS4_OK:
       LOCKX4resok resok;
   default:
       void;
   };

   /*
    * LOCKU: Unlock file
    */
   struct LOCKU4args {
       nfs_lockid4 id;
       offset4     offset;
       length4     length;
   };

   union LOCKU4res switch (nfsstat4 status) {
   case NFS4_OK:
       void;
   default:
       void;
   };




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   /*
    * LOOKUP: Lookup filename
    */
   struct LOOKUP4args {
       filename4 filenames<>;
   };

   union LOOKUP4res switch (nfsstat4 status) {
   case NFS4_OK:
       void;
   default:
       void;
   };

   /*
    * LOOKUPP: Lookup parent directory
    */
   union LOOKUPP4res switch (nfsstat4 status) {
   case NFS4_OK:
       void;
   default:
       void;
   };

   /*
    * NVERIFY: Verify attributes different
    */
   struct NVERIFY4args {
       bitmap4 attr_request;
       fattr4 obj_attributes;
   };

   union NVERIFY4res switch (nfsstat4 status) {
   case NFS4_OK:
       void;
   default:
       void;
   };

   /*
    * RESTOREFH: Restore saved filehandle
    */

   union RESTOREFH4res switch (nfsstat4 status) {
   case NFS4_OK:
       void;
   default:
       void;



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   };

   /*
    * SAVEFH: Save current filehandle
    */
   union SAVEFH4res switch (nfsstat4 status) {
   case NFS4_OK:
       void;
   default:
       void;
   };

   /*
    * PUTFH: Set current filehandle
    */
   struct PUTFH4args {
       nfs_fh4 object;
   };

   union PUTFH4res switch (nfsstat4 status) {
   case NFS4_OK:
       void;
   default:
       void;
   };

   /*
    * PUTROOTFH: Set root filehandle
    */
   union PUTROOTFH4res switch (nfsstat4 status) {
   case NFS4_OK:
       void;
   default:
       void;
   };

   /*
    * READ: Read from file
    */
   struct READ4args {
       offset4             offset;
       count4              count;
   };

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



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

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

   };

   struct entry4 {
       cookie4     cookie;
       filename4   name;
       fattr4      attrs;
       entry4      *nextentry;
   };

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

   struct READDIR4resok {
       dirlist4    reply;
   };


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


   /*
    * READLINK: Read symbolic link
    */
   struct READLINK4resok {
       linktext4   link;



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   };

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

   /*
    * REMOVE: Remove filesystem object
    */
   struct REMOVE4args {
       filename4   target;
   };

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

   /*
    * RENAME: Rename directory entry
    */
   struct RENAME4args {
       filename4   oldname;
       nfs_fh4     newdir;
       filename4   newname;
   };

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

   /*
    * SETATTR: Set attributes
    */
   struct SETATTR4args {
       fattr4 obj_attributes;
   };

   union SETATTR4res switch (nfsstat4 status) {
   case NFS4_OK:



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       void;
   default:
       void;
   };

   /*
    * VERIFY: Verify attributes same
    */
   struct VERIFY4args {
       bitmap4 attr_request;
       fattr4 obj_attributes;
   };

   union VERIFY4res switch (nfsstat4 status) {
   case NFS4_OK:
       void;
   default:
       void;
   };

   /*
    * WRITE: Write to file
    */
   enum stable_how4 {
       UNSTABLE  = 0,
       DATA_SYNC = 1,
       FILE_SYNC = 2
   };

   struct WRITE4args {
       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 resok;
   default:
       void;
   };



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   /*
    * SECINFO: Obtain Available Security Mechanisms
    */
   struct SECINFO4args {
       filename4   name;
   };

   struct rpc_flavor_info {
       secoid4     oid;
       qop4        qop;
       rpc_gss_svc_t service;
   };

   struct secinfo4 {
       rpc_flavor4 flavor;
       rpc_flavor_info *flavor_info;
       secinfo4    *nextentry;
   };

   struct SECINFO4resok {
       secinfo4    reply;
   };


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

   enum opcode {
       OP_NULL             = 0,
       OP_ACCESS           = 1,
       OP_COMMIT           = 2,
       OP_CREATE           = 3,
       OP_GETATTR          = 4,
       OP_GETFH            = 5,
       OP_LINK             = 6,
       OP_LOCKR            = 7,
       OP_LOCKW            = 8,
       OP_LOCKT            = 9,
       OP_LOCKX            = 10,
       OP_LOCKU            = 11,
       OP_LOOKUP           = 12,
       OP_LOOKUPP          = 13,
       OP_NVERIFY          = 14,
       OP_RESTOREFH        = 15,



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       OP_SAVEFH           = 16,
       OP_PUTFH            = 17,
       OP_PUTROOTFH        = 18,
       OP_READ             = 19,
       OP_READDIR          = 20,
       OP_READLINK         = 21,
       OP_REMOVE           = 22,
       OP_RENAME           = 23,
       OP_SETATTR          = 24,
       OP_VERIFY           = 25,
       OP_WRITE            = 26,
       OP_SECINFO          = 27
   };

   union opunion switch (unsigned opcode) {
       case OP_NULL:       void;
       case OP_ACCESS:     ACCESS4args opaccess;
       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_LOCKR:      LOCKR4args oplockr;
       case OP_LOCKW:      LOCKW4args oplockw;
       case OP_LOCKT:      LOCKT4args oplockt;
       case OP_LOCKX:      LOCKX4args oplockx;
       case OP_LOCKU:      LOCKU4args oplocku;
       case OP_LOOKUP:     LOOKUP4args oplookup;
       case OP_LOOKUPP:    void;
       case OP_NVERIFY:    NVERIFY4args opnverify;
       case OP_RESTOREFH:  void;
       case OP_SAVEFH:     void;
       case OP_PUTFH:      PUTFH4args opputfh;
       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_SETATTR:    SETATTR4args opsetattr;
       case OP_VERIFY:     VERIFY4args opverify;
       case OP_WRITE:      WRITE4args opwrite;
       case OP_SECINFO:    SECINFO4args opsecinfo;
   };

   struct op {
       opunion ops;
   };



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   union resultdata switch (unsigned resop){
       case OP_NULL:       void;
       case OP_ACESS:      ACCESS4res op;
       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_LOCKR:      LOCKR4res oplockr;
       case OP_LOCKW:      LOCKW4res oplockw;
       case OP_LOCKT:      LOCKT4res oplockt;
       case OP_LOCKX:      LOCKX4res oplockx;
       case OP_LOCKU:      LOCKU4res oplocku;
       case OP_LOOKUP:     LOOKUP4res oplookup;
       case OP_LOOKUPP:    LOOKUPP4res oplookupp;
       case OP_NVERIFY:    NVERIFY4res opnverify;
       case OP_RESTOREFH:  RESTOREFH4res oprestorefh;
       case OP_SAVEFH:     SAVEFH4res opsavefh;
       case OP_PUTFH:      PUTFH4res opputfh;
       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_SETATTR:    SETATTR4res opsetattr;
       case OP_VERIFY:     VERIFY4res opverify;
       case OP_WRITE:      WRITE4res opwrite;
       case OP_SECINFO:    SECINFO4res opsecinfo;
   };

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

   struct COMPOUND4resok {
       utf8string tag;
       resultdata data<>;
   };

   union COMPOUND4res switch (nfsstat4 status){
   case NFS4_OK:
       COMPOUND4resok resok;
   default:
       void;
   };




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   /*
    * Remote file service routines
    */
   program NFS4_PROGRAM {
       version NFS_V4 {
           void
               NFSPROC4_NULL(void) = 0;

           COMPOUND4res
               NFSPROC4_COMPOUND(COMPOUND4args) = 1;

       } = 4;
   } = 100003;






































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12.  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.





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   [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.

   ftp://ftp.isi.edu/in-notes/rfc1094.txt


   [RFC1813]
   Callaghan, B., Pawlowski, B., Staubach, P., "NFS Version 3 Protocol
   Specification", RFC1813, Sun Microsystems, Inc., June 1995.

   ftp://ftp.isi.edu/in-notes/rfc1813.txt


   [RFC1831]
   Srinivasan, R., "RPC: Remote Procedure Call Protocol Specification
   Version 2", RFC1831, Sun Microsystems, Inc., August 1995.

   ftp://ftp.isi.edu/in-notes/rfc1831.txt


   [RFC1832]
   Srinivasan, R., "XDR: External Data Representation Standard",
   RFC1832, Sun Microsystems, Inc., August 1995.

   ftp://ftp.isi.edu/in-notes/rfc1832.txt


   [RFC1833]
   Srinivasan, R., "Binding Protocols for ONC RPC Version 2", RFC1833,
   Sun Microsystems, Inc., August 1995.

   ftp://ftp.isi.edu/in-notes/rfc1833.txt


   [RFC2078]
   Linn, J., "Generic Security Service Application Program Interface,
   Version 2", RFC2078, OpenVision Technologies, January 1997.

   ftp://ftp.isi.edu/in-notes/rfc2078.txt




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   [RFC2203]
   Eisler, M., Chiu, A., Ling, L., "RPCSEC_GSS Protocol Specification"
   RFC2203, Sun Microsystems, Inc., August 1995.

   ftp://ftp.isi.edu/in-notes/rfc2203.txt


   [Sandberg]
   Sandberg, R., D. Goldberg, S. Kleiman, D. Walsh, B.  Lyon, "Design
   and Implementation of the Sun Network Filesystem," USENIX Conference
   Proceedings, USENIX Association, Berkeley, CA, Summer 1985.  The
   basic paper describing the SunOS implementation of the NFS version 2
   protocol, and discusses the goals, protocol specification and trade-
   offs.


   [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].


   [X/OpenNFS]
   X/Open Company, Ltd., X/Open CAE Specification: Protocols for X/Open
   Internetworking: XNFS, X/Open Company, Ltd., Apex Plaza, Forbury
   Road, Reading Berkshire, RG1 1AX, United Kingdom, 1991.  This is an
   indispensable reference for NFS version 2 protocol and accompanying
   protocols, including the Lock Manager and the Portmapper.


   [X/OpenPCNFS]
   X/Open Company, Ltd., X/Open CAE Specification: Protocols for X/Open
   Internetworking: (PC)NFS, Developer's Specification, X/Open Company,
   Ltd., Apex Plaza, Forbury Road, Reading Berkshire, RG1 1AX, United
   Kingdom, 1991.  This is an indispensable reference for NFS version 2
   protocol and accompanying protocols, including the Lock Manager and
   the Portmapper.



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13.  Author's Address

   Address comments related to this memorandum to:

        nfsv4-wg@sunroof.eng.sun.com

   Spencer Shepler
   Sun Microsystems, Inc.
   7808 Moonflower Drive
   Austin, Texas 78750

   Phone: 1-512-349-9376
   E-mail: shepler@eng.sun.com






































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