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From: NeilBrown <>
To: Steve Dickson <>
Cc: Chuck Lever <>,
	NFS <>,
	Carsten Ziepke <>
Subject: [PATCH - nfs-utils] Fix fallback from tcp to udp
Date: Tue, 18 Feb 2014 10:43:07 +1100	[thread overview]
Message-ID: <20140218104307.34205fc8@notabene.brown> (raw)

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Protocol negotiation in mount.nfs does not correctly negotiate with a
server which only support NFSv3 and UDP.

When mount.nfs attempts an NFSv4 mount and fails with ECONNREFUSED
it does not fall back to NFSv3, as this is not recognised as a
"does not support NFSv4" error.
However ECONNREFUSED is a clear indication that the server doesn't
support TCP, and ipso facto does not support NFSv4.
So ECONNREFUSED should trigger a fallback from v4 to v2/3.

Once we allow that error, NFSv3 is attempted and mount.nfs talks to
rpcbind and discovers that UDP should be used for v3 and the mount

Signed-off-by: NeilBrown <>
Reported-by: Carsten Ziepke <>

diff --git a/utils/mount/stropts.c b/utils/mount/stropts.c
index a642394d2f5a..6d4fd70b7b9e 100644
--- a/utils/mount/stropts.c
+++ b/utils/mount/stropts.c
@@ -807,6 +807,9 @@ static int nfs_autonegotiate(struct nfsmount_info *mi)
 		/* Linux servers prior to 2.6.25 may return
 		 * EPERM when NFS version 4 is not supported. */
 		goto fall_back;
+		/* UDP-Only servers won't support v4 */
+		goto fall_back;
 		return result;

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             reply	other threads:[~2014-02-17 23:43 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-02-17 23:43 NeilBrown [this message]
2014-02-20 17:50 ` Steve Dickson
2014-02-20 20:37   ` J. Bruce Fields
2014-02-20 20:42     ` J. Bruce Fields
2014-02-21  3:26     ` NeilBrown
2014-02-21 14:59       ` J. Bruce Fields
2014-02-21 15:22         ` Chuck Lever

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