On Tue, 31 Aug 2010 12:38:09 -0400
Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
> >>
> >>> + /* OK to try different protocols. Lets see
> >>> + * what portmap thinks.
> >>> + */
> >>> + int oldfake = mi->fake;
> >>> + int res;
> >>> + mi->fake = 1;
> >>> + res = nfs_try_mount_v3v2(mi);
> >>
> >> If you just want to probe the server's portmapper, I think you can use nfs_probe_bothports() directly.
> >>
> >
> > Not quite. You would need to wrap it in a loop over all addresses in
> > md->address, and would need to worry about the mounthost option. It seems
> > easier to just call nfs_try_mount_v3v2 which already does this.
>
> /me smacks forehead
>
> Complexity that I guess we have to live with. A comment that explains the oldfake hack would be helpful.
And often trying to write such a comment can make it clear why the code was a
bad idea in the first place.... :-)
Rather than write a comment I wouldn't believe myself, here is something
quite different - my third draft.
This is on top of the nice tidy-up patches you posted earlier.
It uses nfs_getport to make very focussed requests to portmap.
Two things I'm still not really sure about:
1/ RDMA. How does that interact with fallback. Do we only support v4 over
RDMA? That would be nice was we could simply avoid fallback in that case.
2/ IPv6. I should possibly be checking if v3v2 are available via UDP6 as well
as UDP - and similarly if v4 has become available via TCP6?? Or is that
all magically handled somewhere under the hood?
Thanks,
NeilBrown
>From 60dae9b9c14869ae630db683e2524ad230064b19 Mon Sep 17 00:00:00 2001
From: Neil Brown <neilb@xxxxxxx>
Date: Tue, 7 Sep 2010 11:23:02 +1000
Subject: [PATCH] mount: correctly handle fallback for ECONNREFUSED during mount attempt.
If we get ECONNREFUSED when attempting a v4 mount, it could be that
the server just isn't ready yet (the current assumption) or it could
be that the server only support UDP - and thus only v3/v2. The latter
possibility isn't handled currently.
So if we get ECONNREFUSED when fallback is an option, check with
portmap/rpcbind to see if it could be that case that v2/v3 are
supported over UDP, and v4 still is not. In that case, fall back to v2v3.
I'm not at all sure if IPv6 possibilities are RDMA are handled correctly..
Signed-off-by: NeilBrown <neilb@xxxxxxx>
diff --git a/utils/mount/stropts.c b/utils/mount/stropts.c
index 9e29a19..5ebcf3e 100644
--- a/utils/mount/stropts.c
+++ b/utils/mount/stropts.c
@@ -750,6 +750,7 @@ static int nfs_autonegotiate(struct nfsmount_info *mi)
{
unsigned long protocol;
int result;
+ struct addrinfo *ai;
/*
* If UDP was requested from the command line, try
@@ -796,6 +797,33 @@ 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;
+ case ECONNREFUSED:
+ /* Either the server doesn't accept TCP connections,
+ * or it just isn't quite ready yet.
+ * In the first case, fall back to v3v2, in the second
+ * return failure - as this isn't a permanent error
+ * the attempt will be retried.
+ * To determine which, we need to check with portmap/rpcbind.
+ * If v2 or v3 are supported on UDP, but v4 isn't on TCP then fall-back.
+ */
+ for (ai = mi->address; ai != NULL; ai = ai->ai_next) {
+ if (nfs_getport(ai->ai_addr, ai->ai_addrlen,
+ NFS_PROGRAM, 3, IPPROTO_UDP) != 0 ||
+ nfs_getport(ai->ai_addr, ai->ai_addrlen,
+ NFS_PROGRAM, 2, IPPROTO_UDP) != 0) {
+ if (nfs_getport(ai->ai_addr, ai->ai_addrlen,
+ NFS_PROGRAM, 4, IPPROTO_TCP) != 0) {
+ /* v4 support is almost online, wait for it. */
+ errno = ECONNREFUSED;
+ return result;
+ } else
+ /* v2/v3 is supported, but v4 isn't, fall_back */
+ goto fall_back;
+ }
+ }
+ /* portmap is not responding yet either, so just try again */
+ errno = ECONNREFUSED;
+ return result;
default:
return result;
}
--
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