NFS Version 4 Working Group                                  S. Shepler
INTERNET-DRAFT                                             B. Callaghan
Document: draft-ietf-nfsv4-00.txt                             M. Eisler
                                                            D. Robinson
                                                             R. Thurlow
                                                       Sun Microsystems
                                                          February 1999



                             NFS version 4



Status of this Memo

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

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

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

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

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


Abstract

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





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Copyright

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


Key Words

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









































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . 6
   2.  RPC and Security Flavor  . . . . . . . . . . . . . . . . . . 7
   2.1.  Ports and Transports . . . . . . . . . . . . . . . . . . . 7
   2.2.  Security Flavors . . . . . . . . . . . . . . . . . . . . . 7
   2.2.1.  Security mechanisms for NFS version 4  . . . . . . . . . 7
   2.2.1.1.  Kerberos V5 as security triple . . . . . . . . . . . . 7
   2.2.1.2.  <another security triple>  . . . . . . . . . . . . . . 8
   2.3.  Security Negotiation . . . . . . . . . . . . . . . . . . . 8
   2.3.1.  Security Error . . . . . . . . . . . . . . . . . . . . . 8
   2.3.2.  SECINFO  . . . . . . . . . . . . . . . . . . . . . . . . 9
   3.  File handles . . . . . . . . . . . . . . . . . . . . . . .  10
   3.1.  Obtaining the first file handle  . . . . . . . . . . . .  10
   3.2.  The persistent and volatile file handle  . . . . . . . .  10
   4.  Basic Data Types . . . . . . . . . . . . . . . . . . . . .  12
   5.  File Attributes  . . . . . . . . . . . . . . . . . . . . .  14
   5.1.  Mandatory attributes . . . . . . . . . . . . . . . . . .  15
   5.2.  Recommended attributes . . . . . . . . . . . . . . . . .  15
   5.3.  Extended attributes  . . . . . . . . . . . . . . . . . .  16
   5.4.  Mandatory Attributes - Definitions . . . . . . . . . . .  16
   5.5.  Recommended Attributes - Definitions . . . . . . . . . .  18
   6.  NFS Server Namespace . . . . . . . . . . . . . . . . . . .  28
   6.1.  Server Exports . . . . . . . . . . . . . . . . . . . . .  28
   6.2.  Browsing Exports . . . . . . . . . . . . . . . . . . . .  28
   6.3.  Server Pseudo File-System  . . . . . . . . . . . . . . .  29
   6.4.  Multiple Roots . . . . . . . . . . . . . . . . . . . . .  29
   6.5.  Filehandle Volatility  . . . . . . . . . . . . . . . . .  29
   6.6.  Exported Root  . . . . . . . . . . . . . . . . . . . . .  29
   6.7.  Mount Point Crossing . . . . . . . . . . . . . . . . . .  30
   6.8.  Summary  . . . . . . . . . . . . . . . . . . . . . . . .  30
   7.  File Locking . . . . . . . . . . . . . . . . . . . . . . .  31
   7.1.  Definitions  . . . . . . . . . . . . . . . . . . . . . .  31
   7.2.  Locking  . . . . . . . . . . . . . . . . . . . . . . . .  32
   7.2.1.  Client ID  . . . . . . . . . . . . . . . . . . . . . .  32
   7.2.2.  nfs_lockowner and stateid definition . . . . . . . . .  34
   7.2.3.  Use of the stateid . . . . . . . . . . . . . . . . . .  34
   7.2.4.  Sequencing of lock requests  . . . . . . . . . . . . .  35
   7.3.  Blocking locks . . . . . . . . . . . . . . . . . . . . .  35
   7.4.  Lease renewal  . . . . . . . . . . . . . . . . . . . . .  36
   7.5.  Crash recovery . . . . . . . . . . . . . . . . . . . . .  36
   7.6.  Server revocation of locks . . . . . . . . . . . . . . .  37
   7.7.  Share reservations . . . . . . . . . . . . . . . . . . .  38
   7.8.  OPEN/CLOSE procedures  . . . . . . . . . . . . . . . . .  38
   8.  Defined Error Numbers  . . . . . . . . . . . . . . . . . .  40
   9.  Compound Requests  . . . . . . . . . . . . . . . . . . . .  44
   10.  NFS Version 4 Requests  . . . . . . . . . . . . . . . . .  45
   10.1.  Evaluation of a Compound Request  . . . . . . . . . . .  45



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   11.  NFS Version 4 Procedures  . . . . . . . . . . . . . . . .  46
   11.1.  Procedure 0: NULL - No operation  . . . . . . . . . . .  47
   11.2.  Procedure 1: ACCESS - Check Access Permission . . . . .  48
   11.3.  Procedure 2: CLOSE - close file . . . . . . . . . . . .  51
   11.4.  Procedure 3: COMMIT - Commit cached data  . . . . . . .  52
   11.5.  Procedure 4: CREATE - Create a non-regular file object   55
   11.6.  Procedure 5: GETATTR - Get attributes . . . . . . . . .  59
   11.7.  Procedure 6: GETFH - Get current filehandle . . . . . .  60
   11.8.  Procedure 7: LINK - Create link to an object  . . . . .  61
   11.9.  Procedure 8: LOCK - Create lock . . . . . . . . . . . .  63
   11.10.  Procedure 9: LOCKT - test for lock . . . . . . . . . .  64
   11.11.  Procedure 10: LOCKU - Unlock file  . . . . . . . . . .  65
   11.12.  Procedure 11: LOOKUP - Lookup filename . . . . . . . .  66
   11.13.  Procedure 12: LOOKUPP - Lookup parent directory  . . .  68
   11.14.  Procedure 13: NVERIFY - Verify attributes different  .  69
   11.15.  Procedure 14: OPEN - Open a regular file . . . . . . .  70
   11.16.  Procedure 15: PUTFH - Set current filehandle . . . . .  73
   11.17.  Procedure 16: PUTROOTFH - Set root filehandle  . . . .  74
   11.18.  Procedure 17: READ - Read from file  . . . . . . . . .  75
   11.19.  Procedure 18: READDIR - Read directory . . . . . . . .  78
   11.20.  Procedure 19: READLINK - Read symbolic link  . . . . .  81
   11.21.  Procedure 20: REMOVE - Remove filesystem object  . . .  83
   11.22.  Procedure 21: RENAME - Rename directory entry  . . . .  85
   11.23.  Procedure 22: RENEW - renew a lease  . . . . . . . . .  87
   11.24.  Procedure 23: RESTOREFH - Restore saved filehandle . .  88
   11.25.  Procedure 24: SAVEFH - Save current filehandle . . . .  89
   11.26.  Procedure 25: SECINFO - Obtain Available Security  . .  90
   11.27.  Procedure 26: SETATTR - Set attributes . . . . . . . .  92
   11.28.  Procedure 27: SETCLIENTID - negotiated clientid  . . .  94
   11.29.  Procedure 28: VERIFY - Verify attributes same  . . . .  95
   11.30.  Procedure 29: WRITE - Write to file  . . . . . . . . .  96
   12.  Locking notes . . . . . . . . . . . . . . . . . . . . . .  101
   12.1.  Short and long leases . . . . . . . . . . . . . . . . .  101
   12.2.  Clocks and leases . . . . . . . . . . . . . . . . . . .  101
   12.3.  Locks and lease times . . . . . . . . . . . . . . . . .  101
   12.4.  Locking of directories and other meta-files . . . . . .  102
   12.5.  Proxy servers and leases  . . . . . . . . . . . . . . .  102
   12.6.  Locking and the new latency . . . . . . . . . . . . . .  102
   13.  Internationalization  . . . . . . . . . . . . . . . . . .  103
   13.1.  Universal Versus Local Character Sets . . . . . . . . .  103
   13.2.  Overview of Universal Character Set Standards . . . . .  104
   13.3.  Difficulties with UCS-4, UCS-2, Unicode . . . . . . . .  105
   13.4.  UTF-8 and its solutions . . . . . . . . . . . . . . . .  106
   14.  Security Considerations . . . . . . . . . . . . . . . . .  107
   15.  NFS Version 4 RPC definition file . . . . . . . . . . . .  108
   16.  Bibliography  . . . . . . . . . . . . . . . . . . . . . .  127
   17.  Authors and Contributors  . . . . . . . . . . . . . . . .  131
   17.1.  Contributors  . . . . . . . . . . . . . . . . . . . . .  131



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   17.2.  Editor's Address  . . . . . . . . . . . . . . . . . . .  131
   17.3.  Authors' Addresses  . . . . . . . . . . . . . . . . . .  131
   18.  Full Copyright Statement  . . . . . . . . . . . . . . . .  133
















































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

2.1.  Ports and Transports

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

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

2.2.  Security Flavors

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

2.2.1.  Security mechanisms for NFS version 4

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

2.2.1.1.  Kerberos V5 as security triple

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

 columns:




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

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


        This section will be expanded to include the pertinent
        details from draft-ietf-nfsv4-nfssec-00.txt.


2.2.1.2.  <another security triple>


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


2.3.  Security Negotiation

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

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

2.3.1.  Security Error

   Based on the assumption that each NFS version 4 client and server
   must support a minimum set of security (i.e. Kerberos-V5 under
   RPCSEC_GSS, <ed: add other>), the NFS client will start its
   communication with the server with one of the minimal security



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   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.

































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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 used to uniquely identify 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 SHOULD 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 [RFC2054] [RFC2055].
   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
   handle.  Most commonly the client will need to store the component



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   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    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    Allows for server file systems that have difficulty in mapping a
        stable file handle to a file object.  In this case, a server
        implementation would be able to build a mapping dynamically
        between a volatile file handle and the file system object.


   In some cases a file handle is stale (no longer valid, perhaps
   because the file was removed from the server), or it is expired (the
   underlying file is valid, but since the file handle is volatile, it
   may have expired, requiring the client to get a new file handle).
   Thus the server needs to be able to return NFS4ERR_STALE in the
   former case, and NFS4ERR_EXPIRED in the latter case. This can be done
   by careful construction of the volatile file handle.  One
   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.

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

   bitmap: uint32 <>

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

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

   createverf: opaque<8>

        Verify used for exclusive create semantics

   nfstime4
         struct nfstime4 {
             int64_t seconds;
             uint32_t nseconds;
         }

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



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

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


   specdata4
         struct specdata4 {
             uint32_t specdata1;
             uint32_t specdata2;
         }

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





























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5.  File Attributes

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

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

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


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


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

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



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


5.1.  Mandatory attributes

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


5.2.  Recommended attributes

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

   Most attributes from NFS V3's FSINFO, FSSTAT and PATHCONF procedures
   have been added as recommended attributes, so that filesystem info
   may be collected via the filehandle of any object the filesystem.
   This renders those procedures unnecessary in NFS V4.  If a server
   supports any per-filesystem attributes, it must support the fsid
   attribute so that the client may always determine when filesystems
   are crossed so that it can work correctly with these attributes.







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5.3.  Extended attributes

   These attributes are not supported by direct encoding in the NFS
   Version 4 protocol, but are accessed by string names rather than
   numbers, and correspond to an uninterpreted stream of bytes which are
   stored with the filesystem object.  The namespace for these
   attributes may be accessed by using the OPENATTR operation to get a
   filehandle for a virtual "attribute directory" and using READDIR and
   LOOKUP operations on this filehandle.  Extended attributes may then
   be examined or changed by normal READ and WRITE and CREATE operations
   on the filehandles returned from READDIR and LOOKUP.  Attributes may
   have attributes, for example, a security label may have access
   control information in its own right.

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

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

   The following is a list of mandatory and recommended attributes.


5.4.  Mandatory Attributes - Definitions



   Name:           supp_attr

   Data Type:      nfs_attrvec4

   Access:         Read

   Description:    the bit vector which would retrieve all mandatory and
                   recommended attributes which may be requested for
                   this object

   Justification:  the client must ask this question to request correct
                   attributes



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   Name:           object_type

   Data Type:      nfs_type4

   Access:         Read

   Description:    the type of the object (file/directory/symlink)

   Justification:  the client cannot handle object correctly without
                   type


   Name:           object_size

   Data Type:      uint64

   Access:         Read Write

   Description:    the size of the object in bytes

   Justification:  could be very expensive to derive, likely to be
                   available



   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.

   Justification:  necessary for any useful caching, likely to be
                   available


   Name:           persistent_fh

   Data Type:      boolean

   Access:         Read

   Description:    is the filehandle for this object persistent?




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


   Name:           extended

   Data Type:      boolean

   Access:         Read

   Description:    whether or not this object has extended attributes

   Justification:


   Name:           link_support

   Data Type:      boolean

   Access:         Read

   Description:    whether or not this object's filesystem supports hard
                   links

   Justification:  Server can easily determine if links are supported


   Name:           symlink_support

   Data Type:      boolean

   Access:         Read

   Description:    whether or not this object's filesystem supports
                   symbolic links

   Justification:  Server can easily determine if links are supported


5.5.  Recommended Attributes - Definitions



   Name:           owner

   Data Type:      utf8<>



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   Access:         Read Write

   Description:    the string name of the owner of this object; note
                   that the concept of a numeric uid has been dropped


   Name:           group_owner

   Data Type:      utf8<>

   Access:         Read Write

   Description:    the string name of the group of the owner of this
                   object; note that the concept of a numeric gid has
                   been dropped


   Name:           file_id

   Data Type:      fileid4

   Access:         Read

   Description:    a number uniquely identifying the file within the
                   filesystem


   Name:           file_name

   Data Type:      utf8<>

   Access:         Read

   Description:    the name of this object (primarily for readdir
                   requests)


   Name:           filehandle

   Data Type:      nfs_fh4

   Access:         Read

   Description:    the filehandle of this object (primarily for readdir
                   requests)


   Name:           ACL



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   Data Type:      nfsacl4

   Access:         Read Write

   Description:    the access control list for the object [The nature
                   and format of ACLs is still to be determined.]


   Name:           mode

   Data Type:      uint32

   Access:         Read Write

   Description:    Unix-style permission bits for this object
                   (deprecated in favor of ACLs)


   Name:           object_links

   Data Type:      uint32

   Access:         Read

   Description:    number of links to this object


   Name:           space_used

   Data Type:      uint64

   Access:         Read

   Description:    number of filesystem bytes allocated to this object


   Name:           fsid.major

   Data Type:      uint64

   Access:         Read

   Description:    unique filesystem identifier for the filesystem
                   holding this object


   Name:           fsid.minor




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   Data Type:      uint64

   Access:         Read

   Description:    unique filesystem identifier within the fsid.major
                   filesystem identifier for the filesystem holding this
                   object


   Name:           quota_used

   Data Type:      uint64

   Access:         Read

   Description:    number of bytes of disk space occupied by the owner
                   of this object on this filesystem


   Name:           quota_soft

   Data Type:      uint64

   Access:         Read

   Description:    number of bytes of disk space at which the client may
                   choose to warn the user about limited space


   Name:           quota_hard

   Data Type:      uint64

   Access:         Read

   Description:    number of bytes of disk space beyond which the server
                   will decline to allocate new space


   Name:           rawdev

   Data Type:      specdata4

   Access:         Read

   Description:    raw device identifier





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   Name:           access_time

   Data Type:      nfstime4

   Access:         Read Write

   Description:    the time of last access to the object


   Name:           create_time

   Data Type:      nfstime4

   Access:         Read Write

   Description:    the time of creation of the object. This attribute
                   does not have any relation to the traditional Unix
                   file attribute 'ctime' or 'change time'.


   Name:           meta-data_time

   Data Type:      nfstime4

   Access:         Read Write

   Description:    the time of last meta-data modification of the
                   object.


   Name:           mod_time

   Data Type:      nfstime4

   Access:         Read Write

   Description:    the time since the epoch of last modification to the
                   object


   Name:           backup_time

   Data Type:      nfstime4

   Access:         Read Write

   Description:    the time of last backup of the object




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   Name:           mime_type

   Data Type:      utf8<>

   Access:         Read Write

   Description:    MIME body type/subtype of this object


   Name:           version

   Data Type:      utf8<>

   Access:         Read Write

   Description:    version number of this document


   Name:           hidden

   Data Type:      boolean

   Access:         Read Write

   Description:    whether or not this file is considered hidden


   Name:           archive

   Data Type:      boolean

   Access:         Read Write

   Description:    whether or not this file has been archived since the
                   time of last modification (deprecated in favor of
                   backup_time)


   Name:           system

   Data Type:      boolean

   Access:         Read Write

   Description:    whether or not this file is a system file


   Name:           homogeneous



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   Data Type:      boolean

   Access:         Read

   Description:    whether or not this object's filesystem is
                   homogeneous, i.e.  whether pathconf is the same for
                   all filesystem objects


   Name:           cansettime

   Data Type:      boolean

   Access:         Read

   Description:    whether or not this object's filesystem can fill in
                   the times on a SETATTR request without an explicit
                   time


   Name:           no_trunc

   Data Type:      boolean

   Access:         Read

   Description:    if a name longer than name_max is used, will an error
                   be returned or will the name be truncated?


   Name:           chown_restricted

   Data Type:      boolean

   Access:         Read

   Description:    will a request to change ownership be honored?


   Name:           case_insensitive

   Data Type:      boolean

   Access:         Read

   Description:    are filename comparisons on this filesystem case
                   insensitive?




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   Name:           case_preserving

   Data Type:      boolean

   Access:         Read

   Description:    is filename case on this filesystem preserved?


   Name:           name_max

   Data Type:      uint32

   Access:         Read

   Description:    maximum filename size supported for this object


   Name:           link_max

   Data Type:      uint32

   Access:         Read

   Description:    maximum number of links for this object


   Name:           read_max

   Data Type:      uint64

   Access:         Read

   Description:    maximum read size supported for this object


   Name:           write_max

   Data Type:      uint64

   Access:         Read

   Description:    maximum write size supported for this object.  This
                   attribute SHOULD be supported if the file is
                   writable.  Lack of this attribute can lead to the
                   client either wasting bandwidth or not receiving the
                   best performance.




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   Name:           maxfilesize

   Data Type:      uint64

   Access:         Read

   Description:    maximum supported file size for the filesystem of
                   this object


   Name:           time_delta

   Data Type:      nfstime4

   Access:         Read

   Description:    smallest useful server time granularity


   Name:           total_space

   Data Type:      uint64

   Access:         Read

   Description:    total disk space in bytes on the filesystem
                   containing this object


   Name:           free_space

   Data Type:      uint64

   Access:         Read

   Description:    free disk space in bytes on the filesystem containing
                   this object - this should be the smallest relevant
                   limit


   Name:           avail_space

   Data Type:      uint64

   Access:         Read

   Description:    disk space in bytes available to this user on the
                   filesystem containing this object - this should be



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                   the smallest relevant limit


   Name:           total_files

   Data Type:      uint64

   Access:         Read

   Description:    total file slots on the filesystem containing this
                   object


   Name:           free_files

   Data Type:      uint64

   Access:         Read

   Description:    free file slots on the filesystem containing this
                   object - this should be the smallest relevant limit


   Name:           avail_files

   Data Type:      uint64

   Access:         Read

   Description:    file slots available to this user on the filesystem
                   containing this object - this should be the smallest
                   relevant limit


   Name:           volatility

   Data Type:      nfstime4

   Access:         Read

   Description:    approximate time until next expected change on this
                   filesystem, as a measure of volatility









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6.  NFS Server Namespace


6.1.  Server Exports

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


6.2.  Browsing Exports


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

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

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







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6.3.  Server Pseudo File-System


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


6.4.  Multiple Roots

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


6.5.  Filehandle Volatility

   The nature of the server's pseudo file-system is that it is a logical
   representation of file-system(s) available from the server.
   Therefore, the pseudo file-system is most likely constructed
   dynamically when the NFS version 4 is first instantiated.  It is
   expected the pseudo file-system may not have an on-disk counterpart
   from which persistent filehandles could be constructed.  Even though
   it is preferable that the server provide persistent filehandles for
   the pseudo file-system, the NFS client should expect that pseudo
   file-system file-handles are volatile.  This can be confirmed by
   checking the associated "persistent_fh" attribute for those
   filehandles in question.  If the filehandles are volatile, the NFS
   client must be prepared to recover a filehandle value (i.e. with a v4
   multi-component LOOKUP) when receiving an error of NFS4ERR_FHEXPIRED.


6.6.  Exported Root

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

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



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           /a/b    disk3  (exported)

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


6.7.  Mount Point Crossing

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

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

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

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

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

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


6.8.  Summary


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








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7.  File Locking

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

   o    Clear division between client and server

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

   o    Simple and robust recovery mechanisms

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

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


7.1.  Definitions


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

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



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             on the same network node.

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

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

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

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


7.2.  Locking

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

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

7.2.1.  Client ID

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

   o    A verifier that is used to detect client reboots.

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

        For an operating system this may be a fully qualified host



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


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

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

   1    Client has never connected to the server

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

        Two clients might still use the same nfs_client_id.id due
        to perhaps configuration error (say a High Availability
        configuration where the nfs_client_id.id is derived from
        the ethernet controller address and both systems have the
        same address).  In this case, nfs4err can be a switched
        union that returns in addition to NFS4ERR_CLID_IN_USE, the
        network address (the rpcbind netid and universal address)
        of the client that is using the id.


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

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



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


7.2.2.  nfs_lockowner and stateid definition

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

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

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

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


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


7.2.3.  Use of the stateid

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

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

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




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

7.2.4.  Sequencing of lock requests

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


7.3.  Blocking locks

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







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7.4.  Lease renewal

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


7.5.  Crash recovery

   The important requirement in crash recovery is that both the client
   and the server know when the other has failed.  Additionally it is
   required that a client sees a consistent view of data across server
   reboots.  I/O operations that may have been queued within the client
   or network buffers, cannot complete until after the client has
   successfully recovered the lock protecting the I/O operation.

   If a client fails, the server only needs to wait the lease period to
   allow conflicting locks.  If the client reinitializes within the
   lease period, it may be forced to wait the remainder of the period
   before resuming service.  To minimize this delay, lock requests
   contain a verifier field in the lock_owner, if the server receives a
   verifier field that does not match the existing verifier, the server
   knows that the client has lost all lock state and locks held for that
   client that do not match the current verifier may be released.  In a
   secure environment, a change in the verifier must only cause the
   locks held by the authenticated requester to be released in order to
   prevent a rogue user from freeing otherwise valid locks.  The
   verifier must have the same uniqueness properties of the COMMIT
   verifier.

   If the server fails and loses locking state, the server must wait the
   lease period before granting any new locks or allowing any I/O.  An
   I/O request during the grace period with an invalid stateid will fail
   with NFS4ERR_GRACE, the client will reissue the lock request with
   reclaim set to TRUE, and upon receiving a successful reply, the I/O
   may be reissued with the new stateid.  Any time a client receives an



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   NFS4ERR_GRACE error it should start recovering all outstanding locks.
   A lock request during the grace period without reclaim set will also
   result in a NFS4ERR_GRACE, triggering the client recovery processing.
   A lock request outside the grace period with reclaim set will succeed
   only if the server can guarantee that no conflicting lock or I/O
   request has been granted since reboot.

   In the case of a network partition longer than the lease period, the
   server will have not received an implicit lease renewal and may free
   all locks held for the client, thus invalidating any stateid held by
   the client.  Subsequent reconnection will cause I/O with invalid
   stateid to fail with NFS4ERR_EXPIRED, the client will suitably notify
   the application holding the lock.  After the lease period has expired
   the server may optionally continue to hold the locks for the client.
   In this case, if a conflicting lock or I/O request is received, the
   lock must be freed to allow the client to detect possible corruption.
   When there is a network partition and the lease expires, the server
   must record on stable storage the client information relating to
   those leases.  This is to prevent the case where another client
   obtains the conflicting lock, frees the lock, and the server reboots.
   After the server recovers the original client may recover the network
   partition and attempt to reclaim the lock.  Without any state to
   indicate that a conflicting may have occurred, the client could get
   in an inconsistent state.  Storing just the client information is the
   minimal state necessary to detect this condition, but could lead to
   losing locks unnecessarily.  However this is considered to be a very
   rare event, and a sophisticated server could store more state
   completely eliminate any unnecessary locks being lost.


7.6.  Server revocation of locks

   The server can revoke the locks held by a client at any time, when
   the client detects revocation it must ensure its state matches that
   of the server.  If locks are revoked due to a server reboot, the
   client will receive a NFS4ERR_GRACE and normal crash recovery
   described above will be performed.

   The server may revoke a lock within the lease period, this is
   considered a rare event likely to be initiated only by a human (as
   part of an administration task).  The client may assume that only the
   file that caused the NFS4ERR_EXPIRED to be returned has lost the
   lock_owner's locks and notifies the holder appropriately.  The client
   can not assume the lease period has been renewed.

   The client not being able to renew the lease period is a relatively
   rare and unusual state.  Both sides will detect this state and can
   recover without data corruption.  The client must mark all locks held



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   as "invalidated" and then must issue an I/O request, either a pending
   I/O or zero length read to revalidate the lock. If the response is
   success the lock is upgraded to valid, otherwise it was revoked by
   the server and the owner is notified.


7.7.  Share reservations

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

   Pseudo-code definition of the semantics:


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


   Old DOS applications specify shares in compatibility mode.  Microsoft
   has indicated in the Win32 specification that it will be deprecated
   in the future and recommends that deny NONE be used.  This
   specification does not support compatibility mode.


7.8.  OPEN/CLOSE procedures

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

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

        Will expand on create semantics here.


   The CLOSE procedure removes all share locks held by the lock_owner on



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

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









































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8.  Defined Error Numbers

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

   A description of each defined error follows:


   NFS4_OK             Indicates the operation completed successfully.


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


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


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


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


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


   NFS4ERR_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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9.  Compound Requests

   NFS version 4 requires 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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10.  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.


10.1.  Evaluation of a Compound Request


   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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11.  NFS Version 4 Procedures


















































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11.1.  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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11.2.  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 directory is
      opened. This procedure is also invoked by NFS client access
      procedure (called possibly through access(2)). The intent is to
      make the behavior of opening a remote file more consistent with
      the behavior of opening a local file.

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

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

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

      Many implementations do not directly support the ACCESS_DELETE
      permission. Operating systems like UNIX will ignore the
      ACCESS_DELETE bit if set on an access request on a non-directory
      object. In these systems, delete permission on a file is
      determined by the access permissions on the directory in which the
      file resides, instead of being determined by the permissions of



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      the file itself.  Thus, the bit mask returned for such a request
      will have the ACCESS_DELETE bit set to 0, indicating that the
      client does not have this permission.

   ERRORS

      NFS4ERR_IO

      NFS4ERR_SERVERFAULT

   SEE

      GETATTR.






































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11.3.  Procedure 2: CLOSE - close file


   SYNOPSIS

      (cfh), stateid -> stateid

   ARGS

      stateid: uint64

   RESULTS

      stateid: uint64

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

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

   ERRORS
      To be determined

   SEE

      OPEN






















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11.4.  Procedure 3: 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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11.5.  Procedure 4: CREATE - Create a non-regular file 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 non-regular file object in a directory
      with a given name.  The OPEN procedure MUST be used to create a
      regular file.

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



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      this case, since the server may use the target object meta-data to
      store the verifier.

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

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

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

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

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




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

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


        Note:

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

        2. Need to consider the symbolic link path as
           an "attribute".  No need for a READLINK op
           if this is so. Similarly, a filehandle could
           be defined as an attribute for LINK.

        3. The presence of a generic create for
           multiple file types makes the protocol
           easier to extend to new file types 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



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      NFS4ERR_NOSPC

      NFS4ERR_ROFS

      NFS4ERR_NAMETOOLONG

      NFS4ERR_DQUOT

      NFS4ERR_NOTSUPP

      NFS4ERR_SERVERFAULT








































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11.6.  Procedure 5: 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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11.7.  Procedure 6: 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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11.8.  Procedure 7: 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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11.9.  Procedure 8: LOCK - Create lock


   SYNOPSIS

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

   ARGS

      type: {READ, WRITE, READW, WRITEW}

      seqid: uint32

      reclaim: boolean

      owner: nfs_lockowner

      offset: uint64

      length: uint64

   RESULTS

      stateid: uint64

      access: int

   DESCRIPTION
      The LOCK procedure requests that a record lock starting at
      'offset' for length 'length' be set on the file represented by
      'cfh'.  The integer.  The 'reclaim' field is used for failure
      recovery.

   IMPLEMENTATION
      See locking section for now.

   ERRORS
      To be determined.












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11.10.  Procedure 9: LOCKT - test for lock


   SYNOPSIS

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

   ARGStype: {READ, WRITE, READW, WRITEW}

      seqid: uint32

      reclaim: boolean

      owner: nfs_lockowner

      offset: uint64

      length: uint64

   RESULTS

      owner: nfs_lockowner

   DESCRIPTION

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

   ERRORS

      NFS4ERR_DENIED

















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11.11.  Procedure 10: LOCKU - Unlock file


   SYNOPSIS

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

   ARGS

      type: {READ, WRITE, READW, WRITEW}

      seqid: uint32

      reclaim: boolean

      owner: nfs_lockowner

      offset: uint64

      length: uint64

   RESULTS

      stateid: uint64

   DESCRIPTION

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

   ERRORS
      To be determined.



















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11.12.  Procedure 11: 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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11.13.  Procedure 12: 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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11.14.  Procedure 13: 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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11.15.  Procedure 14: OPEN - Open a regular file


   SYNOPSIS

      (cfh) filename, flag, owner, seqid, reclaim, access, deny ->
      stateid, access

   ARGS

      filename: utf8string

      flag: openflag (union (createhow4, void))

      owner: nfs_lockowner

      seqid: uint32

      reclaim: boolean

      access: int (flag)

      deny: int (flag)

   RESULTS

      stateid: uint64

      access: int

   DESCRIPTION

      OPEN

      Procedure OPEN creates and/or opens a regular file in a directory
      with a given name.  The flag determines if the file should be
      created if it does not exist and the how union contains a value of
      UNCHECKED, GUARDED, or EXCLUSIVE. UNCHECKED means that the file
      should be created without checking for the existence of a
      duplicate object in the same directory. 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



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      this case, since the server may use the target object meta-data to
      store the verifier.

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

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

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

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

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




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

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


        Note: Need to determine an initial set of attributes that
        must be set, and a set of attributes that can optionally be
        set.


   ERRORS

      NFS4ERR_IO

      NFS4ERR_ACCES

      NFS4ERR_EXIST

      NFS4ERR_NOTDIR

      NFS4ERR_NOSPC

      NFS4ERR_ROFS

      NFS4ERR_NAMETOOLONG

      NFS4ERR_DQUOT

      NFS4ERR_NOTSUPP

      NFS4ERR_SERVERFAULT












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11.16.  Procedure 15: 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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11.17.  Procedure 16: 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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11.18.  Procedure 17: READ - Read from file


   SYNOPSIS

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

   ARGS

      offset: uint64

      count: uint32

      stateid: uint64

   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.

      stateid

           The stateid returned from a previous record or share lock
           request.  Used by the server to verify that the associated



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           lock is still valid and to update lease timeouts for the
           client.

      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
           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




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      NFS4ERR_SERVERFAULT


















































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11.19.  Procedure 18: 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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11.20.  Procedure 19: 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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11.21.  Procedure 20: 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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11.22.  Procedure 21: 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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11.23.  Procedure 22: RENEW - renew a lease


   SYNOPSIS

      stateid -> ()

   ARGS

      stateid: uint64 length: uint64

   RESULTS

      none

   DESCRIPTION

      Renews all leases for the client associated with the stateid.

   ERRORS
      TDB






























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11.24.  Procedure 23: 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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11.25.  Procedure 24: 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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11.26.  Procedure 25: 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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11.27.  Procedure 26: 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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11.28.  Procedure 27: SETCLIENTID - negotiated clientid


   SYNOPSIS

      verifier, client -> clientid

   ARGS

      verifier: uint32

      client: opaque <>

   RESULTS

      clientid: uint64


   DESCRIPTION

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

   IMPLEMENTATION

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

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


   ERRORS
      TBD









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11.29.  Procedure 28: 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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11.30.  Procedure 29: WRITE - Write to file


   SYNOPSIS

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

   ARGS

      offset: uint64

      count: uint32

      stability: uint32

      stateid: uint64

      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.




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      stability

           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.

      stateid

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



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           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

           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:







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              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
      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




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      NFS4ERR_NOSPC

      NFS4ERR_ROFS

      NFS4ERR_INVAL

      NFS4ERR_LOCKED

      NFS4ERR_SERVERFAULT










































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12.  Locking notes


12.1.  Short and long leases

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

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

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

12.2.  Clocks and leases

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

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

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

12.3.  Locks and lease times

   Lock requests do not contain desired lease times.  The server



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   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.

12.4.  Locking of directories and other meta-files

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

12.5.  Proxy servers and leases

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

12.6.  Locking and the new latency

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















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13.  Internationalization

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

13.1.  Universal Versus Local Character Sets

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

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

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

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

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

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



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

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


13.2.  Overview of Universal Character Set Standards


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

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

   o    ISO/IEC which has the standard 10646-1

   o    Unicode which has the Unicode standard

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

   The following is a brief analysis of the various standards.

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


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


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




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   UTF       UCS transformation format.


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


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


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


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


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

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


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


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

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




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13.4.  UTF-8 and its solutions

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

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

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

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

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

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

           1111111x

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

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















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14.  Security Considerations

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

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








































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15.  NFS Version 4 RPC definition file

   /*
    *      nfs_prot.x
    *
    */

   %#pragma ident  "@(#)nfs_prot.x 1.28    99/02/26"

   /*
    * 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 uint64_t        clientid4;
   typedef uint64_t        stateid4;
   typedef uint32_t        seqid4;
   typedef uint32_t        writeverf4;
   typedef opaque          createverf4[NFS4_CREATEVERFSIZE];
   typedef utf8string      filename4;
   typedef uint64_t        nfs_lockid4;
   typedef uint32_t        nfs_lease4;
   typedef uint32_t        nfs_lockstate4;
   typedef uint64_t        nfs_cookie4;
   typedef utf8string      linktext4;
   typedef opaque          sec_oid4<>;
   typedef uint32_t        qop4;



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   typedef uint32_t        fattr4_type;
   typedef uint32_t        fattr4_mode;
   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,



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           NFS4ERR_NAMETOOLONG     = 63,
           NFS4ERR_NOTEMPTY        = 66,
           NFS4ERR_DQUOT           = 69,
           NFS4ERR_STALE           = 70,
           NFS4ERR_BADHANDLE       = 10001,
           NFS4ERR_NOT_SYNC        = 10002,
           NFS4ERR_BAD_COOKIE      = 10003,
           NFS4ERR_NOTSUPP         = 10004,
           NFS4ERR_TOOSMALL        = 10005,
           NFS4ERR_SERVERFAULT     = 10006,
           NFS4ERR_BADTYPE         = 10007,
           NFS4ERR_JUKEBOX         = 10008,
           NFS4ERR_SAME            = 10009,
           NFS4ERR_DENIED          = 10010,/* lock unavailable */
           NFS4ERR_EXPIRED         = 10011,/* lock lease expired */
           NFS4ERR_LOCKED          = 10012,/* I/O failed due to lock */
           NFS4ERR_GRACE           = 10013,/* in grace period */
           NFS4ERR_FHEXPIRED       = 10014 /* file handle expired */
   };

   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
   };

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

   /*
    * File types
    */
   enum ftype4 {



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           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;
   const FSF_SYMLINK               = 0x00000002;
   const FSF_HOMOGENEOUS           = 0x00000004;
   const FSF_CANSETTIME            = 0x00000008;
   const FSF_NOTRUNC               = 0x00000010;



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   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;
   };

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

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

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

   union nfs_lockowner switch (stateid4 stateid) {
    case 0:
            lockown        ident;
    default:
            void;
   };

   enum lock_type {
           READ    = 1,
           WRITE   = 2,
           READW   = 3,    /* blocking read */
           WRITEW  = 4     /* blocking write */
   };




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   /*
    * 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
    */
   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
    */



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

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

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

   const DENY4_NONE        = 0x0000;
   const DENY4_READ        = 0x0001;
   const DENY4_WRITE       = 0x0002;

   union openflag switch (uint32_t flag) {
    case CREATE:
            createhow4     how;
    default:
            void;
   };

   /*
    * LOCK/LOCKT/LOCKU: Record lock management
    */
   struct LOCK4args {
           lock_type       type;
           seqid4          seqid;
           bool            reclaim;
           nfs_lockowner   owner;
           offset4         offset;
           length4         length;
   };

   struct lockres {
           stateid4        stateid;
           int32_t         access;
   };



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

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

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

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

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

   /*
    * OPEN: Open a file, potentially with a share lock
    */
   struct OPEN4args {
           filename4       filenames<>;
           openflag        flag;
           nfs_lockowner   owner;
           seqid4          seqid;
           bool            reclaim;
           int32_t         access;



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           int32_t         deny;
   };

   union OPEN4res switch (nfsstat4 status) {
    case NFS4_OK:
            LOCK4resok     resok;
    default:
            void;
   };

   /*
    * CLOSE: Close a file and release share locks
    */
   struct CLOSE4args {
           stateid4        stateid;
   };

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

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



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   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;
   };

   /*
    * 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



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    */
   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;
   };

   /*
    * 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;
   };




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

   /*
    * READ: Read from file
    */
   struct READ4args {
           stateid4        stateid;
           offset4         offset;
           count4          count;
   };

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

   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;
   };



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   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;
   };

   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



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    */
   struct RENAME4args {
           filename4       oldname;
           nfs_fh4         newdir;
           filename4       newname;
   };

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

   struct RENEW4args {
           stateid4        stateid;
   };

   union RENEW4res 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:
            void;
    default:
            void;
   };

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

   union VERIFY4res switch (nfsstat4 status) {



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    case NFS4_OK:
            void;
    default:
            void;
   };

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

   struct WRITE4args {
           stateid4        stateid;
           offset4         offset;
           count4          count;
           stable_how4     stable;
           opaque          data<>;
   };

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

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

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

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



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   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_CLOSE                = 2,
           OP_COMMIT               = 3,
           OP_GETATTR              = 4,
           OP_GETFH                = 5,
           OP_LINK                 = 6,
           OP_LOCK                 = 7,
           OP_LOCKT                = 8,
           OP_LOCKU                = 9,
           OP_LOOKUP               = 10,
           OP_LOOKUPP              = 11,
           OP_NVERIFY              = 12,
           OP_OPEN                 = 13,
           OP_PUTFH                = 14,
           OP_PUTROOTFH            = 15,
           OP_READ                 = 16,
           OP_READDIR              = 17,
           OP_READLINK             = 18,
           OP_REMOVE               = 19,
           OP_RENAME               = 20,
           OP_RENEW                = 21,
           OP_RESTOREFH            = 22,
           OP_SAVEFH               = 23,
           OP_SECINFO              = 24,
           OP_SETATTR              = 25,
           OP_SETCLIENTID          = 26,
           OP_VERIFY               = 27,
           OP_WRITE                = 28



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   };

   union opunion switch (unsigned opcode) {
    case OP_NULL:          void;
    case OP_ACCESS:        ACCESS4args opaccess;
    case OP_CLOSE:         CLOSE4args opclose;
    case OP_COMMIT:        COMMIT4args opcommit;
    case OP_GETATTR:       GETATTR4args opgettattr;
    case OP_GETFH:         void;
    case OP_LINK:          LINK4args oplink;
    case OP_LOCK:          LOCK4args oplock;
    case OP_LOCKT:         LOCK4args oplockt;
    case OP_LOCKU:         LOCK4args oplocku;
    case OP_LOOKUP:        LOOKUP4args oplookup;
    case OP_LOOKUPP:       void;
    case OP_NVERIFY:       NVERIFY4args opnverify;
    case OP_OPEN:          OPEN4args opopen;
    case OP_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_RENEW:         RENEW4args oprenew;
    case OP_RESTOREFH:     void;
    case OP_SAVEFH:        void;
    case OP_SECINFO:       SECINFO4args opsecinfo;
    case OP_SETATTR:       SETATTR4args opsetattr;
    case OP_SETCLIENTID:   SETCLIENTID4args opsetclientid;
    case OP_VERIFY:        VERIFY4args opverify;
    case OP_WRITE:         WRITE4args opwrite;
   };

   struct op {
           opunion         ops;
   };

   union resultdata switch (unsigned resop){
    case OP_NULL:          void;
    case OP_ACCESS:        ACCESS4res op;
    case OP_CLOSE:         CLOSE4res opclose;
    case OP_COMMIT:        COMMIT4res opcommit;
    case OP_GETATTR:       GETATTR4res opgetattr;
    case OP_GETFH:         GETFH4res opgetfh;
    case OP_LINK:          LINK4res oplink;
    case OP_LOCK:          LOCK4res oplock;
    case OP_LOCKT:         LOCKT4res oplockt;



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    case OP_LOCKU:         LOCKU4res oplocku;
    case OP_LOOKUP:        LOOKUP4res oplookup;
    case OP_LOOKUPP:       LOOKUPP4res oplookupp;
    case OP_NVERIFY:       NVERIFY4res opnverify;
    case OP_OPEN:          OPEN4res opopen;
    case OP_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_RENEW:         RENEW4res oprenew;
    case OP_RESTOREFH:     RESTOREFH4res oprestorefh;
    case OP_SAVEFH:        SAVEFH4res opsavefh;
    case OP_SECINFO:       SECINFO4res opsecinfo;
    case OP_SETATTR:       SETATTR4res opsetattr;
    case OP_SETCLIENTID:   SETCLIENTID4res opsetclientid;
    case OP_VERIFY:        VERIFY4res opverify;
    case OP_WRITE:         WRITE4res opwrite;
   };

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

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

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


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




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                   COMPOUND4res
                           NFSPROC4_COMPOUND(COMPOUND4args) = 1;

           } = 4;
   } = 100003;














































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16.  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.

   http://www.ietf.org/rfc/rfc1094.txt


   [RFC1345]
   Simonsen, K., "Character Mnemonics & Character Sets", RFC1345,
   Rationel Almen Planlaegning, June 1992.

   http://www.ietf.org/rfc/rfc1345.txt


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

   http://www.ietf.org/rfc/rfc1813.txt


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

   http://www.ietf.org/rfc/rfc1831.txt


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

   http://www.ietf.org/rfc/rfc1832.txt


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

   http://www.ietf.org/rfc/rfc1833.txt




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   [RFC2054]
   Callaghan, B., "WebNFS Client Specification", RFC2054, Sun
   Microsystems, Inc., October 1996

   http://www.ietf.org/rfc/rfc2054.txt


   [RFC2055]
   Callaghan, B., "WebNFS Server Specification", RFC2054, Sun
   Microsystems, Inc., October 1996

   http://www.ietf.org/rfc/rfc2055.txt


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

   http://www.ietf.org/rfc/rfc2078.txt


   [RFC2152]
   Goldsmith, D., "UTF-7 A Mail-Safe Transformation Format of Unicode",
   RFC2152, Apple Computer, Inc., May 1997

   http://www.ietf.org/rfc/rfc2152.txt


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

   http://www.ietf.org/rfc/rfc2203.txt


   [RFC2279]
   Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC2279,
   Alis Technologies, January 1998.

   http://www.ietf.org/rfc/rfc2279.txt


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



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   offs.


   [SPNEGO]
   Baize, E., Pinkas, D., "The Simple and Protected GSS-API Negotiation
   Mechanism", draft-ietf-cat-snego-09.txt, Bull, April 1998.

   ftp://ftp.isi.edu/internet-drafts/draft-ietf-cat-snego-09.txt


   [Srinivasan]
   Srinivasan, V., Jeffrey C. Mogul, "Spritely NFS: Implementation and
   Performance of Cache Consistency Protocols", WRL Research Report
   89/5, Digital Equipment Corporation Western Research Laboratory, 100
   Hamilton Ave., Palo Alto, CA, 94301, May 1989.  This paper analyzes
   the effect of applying a Sprite-like consistency protocol applied to
   standard NFS. The issues of recovery in a stateful environment are
   covered in [Mogul].


   [Unicode1]
   "Unicode Technical Report #8 - The Unicode Standard, Version 2.1",
   Unicode, Inc., The Unicode Consortium, P.O. Box 700519, San Jose, CA
   95710-0519 USA, September 1998

   http://www.unicode.org/unicode/reports/tr8.html


   [Unicode2]
   "Unsupported Scripts" Unicode, Inc., The Unicode Consortium, P.O. Box
   700519, San Jose, CA 95710-0519 USA, October 1998

   http://www.unicode.org/unicode/standard/unsupported.html


   [XNFS]
   The Open Group, Protocols for Interworking: XNFS, Version 3W, The
   Open Group, 1010 El Camino Real Suite 380, Menlo Park, CA 94025, ISBN
   1-85912-184-5, February 1998.

   HTML version available: http://www.opengroup.org










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17.  Authors and Contributors

   General feedback related to this document should be directed to:

        nfsv4-wg@sunroof.eng.sun.com

   or the editor.

17.1.  Contributors

   The following individuals have contributed to the document:

   Carl Beame, beame@bws.com, of Hummingbird Communications Ltd.

17.2.  Editor's Address

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

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

17.3.  Authors' Addresses

   Brent Callaghan
   Sun Microsystems, Inc.
   901 San Antonio Road
   Palo Alto, CA 94303

   Phone: +1 650-786-5067
   E-mail: brent.callaghan@eng.sun.com


   Mike Eisler
   Sun Microsystems, Inc.
   5565 Wilson Road
   Colorado Springs, CO 80919

   Phone: +1 719-599-9026
   E-mail: mre@eng.sun.com


   David Robinson
   Sun Microsystems, Inc.
   901 San Antonio Road
   Palo Alto, CA 94303



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   Phone: +1 650-786-5088
   E-mail: david.robinson@eng.sun.com


   Robert Thurlow
   Sun Microsystems, Inc.
   901 San Antonio Road
   Palo Alto, CA 94303

   Phone: +1 650-786-5096
   E-mail: robert.thurlow@eng.sun.com








































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18.  Full Copyright Statement

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

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implmentation may be prepared, copied, published and
   distributed, in whole or in part, without restriction of any kind,
   provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."
























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