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Date:   Sun, 2 Oct 2022 14:35:42 +0200
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To:     linux-nfs@vger.kernel.org
From:   Manfred Schwarb <manfred99@gmx.ch>
Subject: nfs4.1+: workaround for defunct clientaddr?
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Hi,

I have 2 boxes connected with 2 network cards each, one
crossover connection and one connection via LAN.
I want to use the crossover connection for backup,
so I want to be able to select exactly this wire when
doing my NFS backup transfers. Everything interconnected via NFS4.1
and automount.

Now the thing is, if there is an already existing connection
via LAN, I am not able to select the crossover connection,
there is some session reuse against my will.

automount config:
/net/192.168.99.1  -fstype=nfs4,nfsvers=4,minorversion=1,clientaddr=192.168.99.100   /  192.168.99.1:/
/net2/192.168.98.1 -fstype=nfs4,nfsvers=4,minorversion=1,clientaddr=192.168.98.100   /  192.168.98.1:/

mount -l:
192.168.99.1:/data on /net/192.168.99.1/data type nfs4 (...,clientaddr=192.168.99.100,addr=192.168.99.1)
192.168.99.1:/data on /net2/192.168.98.1/data type nfs4 (...,clientaddr=192.168.99.100,addr=192.168.99.1)

As you see, both connections are on "192.168.99.1:/data", and the backup runs
over the same wire as all user communication, which is not desired.
This even happens if I explicitly set some clientaddr= option.

Now I found two workarounds:
- downgrade to NFS 4.0, clientaddr seems to work with it
- choose different NFS versions, i.e. one connection with
  minorversion=1 and the other with minorversion=2

Both possibilities seem a bit lame to me.
Are there some other (recommended) variants which do what I want?

It seems different minor versions result in different "nfs4_unique_id" values,
and therefore no session sharing occurs. But why do different network
interfaces (via explicitly set clientaddr= by user) not result in different
"nfs4_unique_id" values?

Thanks for any comments and advice,
Manfred