svn commit: r307694 - head/sys/fs/nfsserver

[Rick Macklem]

Author: rmacklem
Date: Thu Oct 20 23:53:16 2016
New Revision: 307694
URL: https://svnweb.freebsd.org/changeset/base/307694

Log:
  A problem w.r.t. interoperation between the FreeBSD NFSv4.1 server with
  delegations enabled and the Linux NFSv4.1 client was reported in
  reviews.freebsd.org/D7891.
  I believe that the FreeBSD server behaviour conforms to the RFC and that
  the Linux client has a bug. Therefore, I do not think the proposed patch
  is appropriate. When nfsrv_writedelegifpos is non-zero, the FreeBSD
  server will issue a write delegation for a read open if possible.
  The Linux client then erroneously assumes that the credentials used for
  the read open can write the file.
  This patch reverses the default value for nfsrv_writedelegifpos to 0 so
  that the default behaviour is Linux compatible and adds a sysctl that can
  be used to set nfsrv_writedelegifpos.
  
  This change should only affect users that are mounting a FreeBSD server
  with delegations enabled (they are not enabled by default) with a Linux
  NFSv4.1 client mount.
  
  Reported by:	fatih.acar at gandi.net
  Tested by:	fatih.acar at gandi.net
  MFC after:	2 weeks
  Differential Revision:	https://reviews.freebsd.org/D7891

Modified:
  head/sys/fs/nfsserver/nfs_nfsdstate.c

Modified: head/sys/fs/nfsserver/nfs_nfsdstate.c
==============================================================================
--- head/sys/fs/nfsserver/nfs_nfsdstate.c	Thu Oct 20 23:10:27 2016	(r307693)
+++ head/sys/fs/nfsserver/nfs_nfsdstate.c	Thu Oct 20 23:53:16 2016	(r307694)
@@ -70,6 +70,11 @@ SYSCTL_INT(_vfs_nfsd, OID_AUTO, v4statel
     &nfsrv_v4statelimit, 0,
     "High water limit for NFSv4 opens+locks+delegations");
 
+static int	nfsrv_writedelegifpos = 0;
+SYSCTL_INT(_vfs_nfsd, OID_AUTO, writedelegifpos, CTLFLAG_RW,
+    &nfsrv_writedelegifpos, 0,
+    "Issue a write delegation for read opens if possible");
+
 /*
  * Hash lists for nfs V4.
  */
@@ -80,7 +85,6 @@ struct nfssessionhash		*nfssessionhash;
 
 static u_int32_t nfsrv_openpluslock = 0, nfsrv_delegatecnt = 0;
 static time_t nfsrvboottime;
-static int nfsrv_writedelegifpos = 1;
 static int nfsrv_returnoldstateid = 0, nfsrv_clients = 0;
 static int nfsrv_clienthighwater = NFSRV_CLIENTHIGHWATER;
 static int nfsrv_nogsscallback = 0;