On May 31, 2012, at 9:03 AM, Jeff Layton wrote:
> If a NFS mount attempt fails with an ETIMEDOUT error, the mount.nfs code
> doesn't currently attempt the next address in the list. For a NFSv4 mount
> the initial mount() call almost always ends up going over
> NFS_DEF_FG_TIMEOUT_MINUTES and the mount is never retried.
>
> For a v3 mount, it ends up continually retrying against the same IPv6
> address, and never tries the IPv4 address. Eventually it gives up once
> it hits the NFS_DEF_FG_TIMEOUT_MINUTES timeout.
>
> It's possible that a server is just unreachable via IPv6 (due to a
> routing misconfiguration for instance), or is dropping IPv6 frames on
> the floor. In that situation, it might still be reachable via IPv4 and
> trying the next address could have allowed the mount to succeed.
>
> Fix this by treating ETIMEDOUT in a similar fashion to ECONNREFUSED.
> Have the client try the next address in the list before giving up and
> returning an error.
Bzzzzt. AF fallback is only legal to do if the admin did not specify a netid.
Can you demonstrate that your patch works correctly if an IPv6 netid is specified? "Correctly" here means that no fallback occurs.
> Our QA folks noticed this after a routing problem in one of our test
> labs. I was able to reproduce it by having the server drop incoming
> IPv6 frames from the client's address.
>
> With this patch, the mount eventually succeeds over IPv4 instead of
> returning an error.
>
> Cc: Chuck Lever <chuck.lever@xxxxxxxxxx>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> utils/mount/stropts.c | 2 ++
> 1 files changed, 2 insertions(+), 0 deletions(-)
>
> diff --git a/utils/mount/stropts.c b/utils/mount/stropts.c
> index e09aa7c..0aa9a75 100644
> --- a/utils/mount/stropts.c
> +++ b/utils/mount/stropts.c
> @@ -665,6 +665,7 @@ static int nfs_try_mount_v3v2(struct nfsmount_info *mi)
> case ECONNREFUSED:
> case EOPNOTSUPP:
> case EHOSTUNREACH:
> + case ETIMEDOUT:
> continue;
> default:
> goto out;
> @@ -752,6 +753,7 @@ static int nfs_try_mount_v4(struct nfsmount_info *mi)
> switch (errno) {
> case ECONNREFUSED:
> case EHOSTUNREACH:
> + case ETIMEDOUT:
> continue;
> default:
> goto out;
> --
> 1.7.1
>
--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
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