Index: usr.sbin/rpc.lockd/Makefile
===================================================================
RCS file: /mnt2/ncvs/src/usr.sbin/rpc.lockd/Makefile,v
retrieving revision 1.19
diff -u -u -r1.19 Makefile
--- usr.sbin/rpc.lockd/Makefile	26 Oct 2003 06:10:44 -0000	1.19
+++ usr.sbin/rpc.lockd/Makefile	7 Nov 2003 07:24:11 -0000
@@ -9,6 +9,15 @@
 CFLAGS+= -I. -I${DESTDIR}/usr/include/rpcsvc
 #WARNS?= 2
 
+# At least as of 2.4.23 and 2.6.0pre2, the Linux kernel violates the NFS locking
+# protocol by only accepting cookies of size 8 bytes (the spec allows for up to
+# 1k in size).  By default FreeBSD uses 16 byte cookies; to interoperate with
+# broken Linux NFS lockd implementations, uncomment the line below, add
+# 'options LINUX_BROKEN_NFS_LOCKING' to your kernel and rebuild the kernel and
+# world.
+#
+#CFLAGS+= -DLINUX_BROKEN_NFS_LOCKING 
+
 DPADD=	${LIBRPCSVC} ${LIBUTIL}
 LDADD=	-lrpcsvc -lutil
 
Index: sys/conf/NOTES
===================================================================
RCS file: /mnt2/ncvs/src/sys/conf/NOTES,v
retrieving revision 1.1186
diff -u -u -r1.1186 NOTES
--- sys/conf/NOTES	5 Nov 2003 14:32:27 -0000	1.1186
+++ sys/conf/NOTES	7 Nov 2003 07:22:08 -0000
@@ -767,6 +767,18 @@
 options 	NFS_WDELAYHASHSIZ=16	# and with this
 options 	NFS_DEBUG		# Enable NFS Debugging
 
+# Linux kernels (as of at least 2.4.23 and 2.6.0pre2) do not conform to
+# the NFS locking protocol, and only accept cookies of size 8 bytes.
+# By default FreeBSD uses 16-byte cookies; the following enables
+# compatibility with the Linux rpc.lockd implementation at the cost of
+# removing protection against PID recycling.
+#
+# If you enable this option in your kernel then you must also edit
+# usr.sbin/rpc.lockd/Makefile and uncomment the corresponding line,
+# and rebuild the world.
+#
+options		LINUX_BROKEN_NFS_LOCKING
+
 # Coda stuff:
 options 	CODA			#CODA filesystem.
 device		vcoda	4		#coda minicache <-> venus comm.
Index: sys/conf/options
===================================================================
RCS file: /mnt2/ncvs/src/sys/conf/options,v
retrieving revision 1.424
diff -u -u -r1.424 options
--- sys/conf/options	5 Nov 2003 14:37:48 -0000	1.424
+++ sys/conf/options	7 Nov 2003 04:01:40 -0000
@@ -196,6 +196,7 @@
 # filesystems will be enabled - but look below.
 NFSCLIENT	opt_nfs.h
 NFSSERVER	opt_nfs.h
+LINUX_BROKEN_NFS_LOCKING	opt_nfs.h
 
 # filesystems and libiconv bridge
 CD9660_ICONV	opt_dontuse.h
Index: sys/nfsclient/nfs_lock.c
===================================================================
RCS file: /mnt2/ncvs/src/sys/nfsclient/nfs_lock.c,v
retrieving revision 1.38
diff -u -u -r1.38 nfs_lock.c
--- sys/nfsclient/nfs_lock.c	27 Jul 2003 17:04:56 -0000	1.38
+++ sys/nfsclient/nfs_lock.c	7 Nov 2003 07:12:23 -0000
@@ -117,7 +117,9 @@
 		p->p_nlminfo->pid_start = p->p_stats->p_start;
 		timevaladd(&p->p_nlminfo->pid_start, &boottime);
 	}
+#ifndef LINUX_BROKEN_NFS_LOCKING
 	msg.lm_msg_ident.pid_start = p->p_nlminfo->pid_start;
+#endif
 	msg.lm_msg_ident.msg_seq = ++(p->p_nlminfo->msg_seq);
 
 	msg.lm_fl = *fl;
@@ -264,9 +266,11 @@
 	 * is sort of like writing on a pipe after the reader has closed it.
 	 */
 	if (targetp->p_nlminfo == NULL ||
-	    ((ansp->la_msg_ident.msg_seq != -1) &&
-	      (timevalcmp(&targetp->p_nlminfo->pid_start,
+	    ((ansp->la_msg_ident.msg_seq != -1) && (
+#ifndef LINUX_BROKEN_NFS_LOCKING
+	      timevalcmp(&targetp->p_nlminfo->pid_start,
 			&ansp->la_msg_ident.pid_start, !=) ||
+#endif
 	       targetp->p_nlminfo->msg_seq != ansp->la_msg_ident.msg_seq))) {
 		PROC_UNLOCK(targetp);
 		return (EPIPE);
Index: sys/nfsclient/nfs_lock.h
===================================================================
RCS file: /mnt2/ncvs/src/sys/nfsclient/nfs_lock.h,v
retrieving revision 1.5
diff -u -u -r1.5 nfs_lock.h
--- sys/nfsclient/nfs_lock.h	15 Aug 2002 21:52:22 -0000	1.5
+++ sys/nfsclient/nfs_lock.h	7 Nov 2003 07:23:29 -0000
@@ -51,10 +51,19 @@
  * a particular message to lockd.  A sequence number is used to differentiate
  * multiple messages from the same process.  A process start time is used to
  * detect the unlikely, but possible, event of the recycling of a pid.
+ * 
+ * Linux's implementation of NFS NLM locks is buggy: it doesn't support lock
+ * cookies longer than 8 bytes in size.  See the comment in
+ * <http://lxr.linux.no/source/include/linux/lockd/xdr.h> before the
+ * definition of 'struct nlm_cookie': "NLM cookies. Technically they can be 1K,
+ * Nobody uses over 8 bytes however." (except FreeBSD, MacOS X and possibly
+ * others).
  */
 struct lockd_msg_ident {
 	pid_t		pid;            /* The process ID. */
+#ifndef LINUX_BROKEN_NFS_LOCKING
 	struct timeval	pid_start;	/* Start time of process id */
+#endif
 	int		msg_seq;	/* Sequence number of message */
 };