flock failure on NFS from 5.3 client to 4.7 server

[Bruce Campbell]

NFS server:      FreeBSD 4.7
Old Mail server: FreeBSD 4.7, home directories mounted to NFS server
New Mail server: FreeBSD 5.3, home directories mounted to NFS server

After the mail server upgrade to 5.3, flock gives error "operation not supported" 
on nfs mounted home directories.  Example:

Jan 13 00:06:32 mail vacation[92816]: vacation: .vacation: Operation not supported

output from "truss"

open(".vacation.db",0x2,0640)                    = 3 (0x3)
fstat(3,0xbfbfd350)                              = 0 (0x0)
flock(0x3,0x2)                                   ERR#45 'Operation not supported'
close(3)                                         = 0 (0x0)

It appears someone else has done substantially more debugging than I:

  http://lists.freebsd.org/pipermail/freebsd-questions/2004-September/059777.html

but is seemingly no further ahead.

On our NFS server, rpc.statd is running, but rpc.lockd wasn't.  Started
it, still no worky.  Killed it, other 4.7 clients still flock fine.

Any suggestions for a fix or workaround so "vacation" works (which depends
on flock) ?

Thanks,

-- 
Bruce Campbell
Engineering Computing
CPH-2374B
University of Waterloo
(519)888-4567 ext 5889

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