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From:   Pradeep <pradeepthomas@gmail.com>
Date:   Thu, 25 Mar 2021 10:03:03 -0700
Message-ID: <CAD8zhTC9Bk7GQoUtCz4FstknKEnyw4H1DsZXzUeekR5Bpgkkpw@mail.gmail.com>
Subject: Re: NFSv4 referrals with FQDN.
To:     Chuck Lever III <chuck.lever@oracle.com>
Cc:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>
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Thanks Chuck for confirming that. I will try to post a patch after testing.

On Wed, Mar 24, 2021 at 12:20 PM Chuck Lever III <chuck.lever@oracle.com> wrote:
>
>
>
> > On Mar 23, 2021, at 5:56 PM, Pradeep <pradeepthomas@gmail.com> wrote:
> >
> > Hello,
> >
> > While testing NFSv4 referrals, I noticed that if the server name in FS
> > locations does not have IPv4 mapping (server name has AAAA record for
> > IPv6; but no A record in DNS), the referral mount fails.
>
> IIRC, that is a known bug, but it has been rarely hit up to this point
> (only case I'm aware of is during testing, which is how I know about
> this issue).
>
> The DNS upcall needs to be fixed to handle this case properly. As Bruce
> likes to say, patches welcome!
>
>
> > With debug enabled, I get something like this:
> >
> > nfs_follow_referral: referral at /nfs_export_1
> > nfs4_path: path server-1.domain.com:/nfs_export_1 from nfs_path
> > nfs4_path: path component /nfs_export_1
> > nfs4_validate_fspath: comparing path /nfs_export_1 with fsroot /nfs_export_1
> > ==> dns_query((null),server-2.domain.com,19,(null))
> > call request_key(,server-2.domain.com,)
> > <== dns_query() = -126
> > nfs_follow_referral: done
> > nfs_do_refmount: done
> > RPC:       shutting down nfs client for server-1.domain.com
> > RPC:       rpc_release_client(ffff97fdf170c600)
> > RPC:       destroying nfs client for server-1.domain.com
> > <-- nfs_d_automount(): error -2
> >
> > It looks like NFS client does an upcall to "/sbin/key.dns_resolver".
> > "/sbin/key.dns_resolver" works if callout info is set to 'ipv6'.
> > Otherwise it fails too.
> >
> > Does this mean setups with only IPv6 records (AAAA records in DNS),
> > NFSv4 referrals won't work if server returns FQDN in referral? If
> > anyone has tried this and made it work, please let me know.
> >
> > Thanks,
> > Pradeep
>
> --
> Chuck Lever
>
>
>