Re: autofs reverts to IPv4 for multi-homed IPv6 server ?

[Ian Kent <raven@themaw.net>]

On Thu, 2016-04-07 at 16:19 +0200, Christof Koehler wrote:
> Hello everybody,
> 
> I am on ubuntu 14.04 with autofs 5.0.7 and I observe an (for me)
> unexpected behaviour as detailed below. Apparently using autofs NFS4
> mounts fall back to using IPv4 addresses although valid IPv6 addresses
> are available under certain circumstances, while a plain mount works
> as
> expected.

Can you provide a full debug log.

It might be autofs interfering with the mount but mount.nfs(8) is a more
likely candidate.

> 
> Setup:
> ------
> Both, NFS server and client, are configured with an IPv4 address and
> an
> IPv6 GUA and IPv6 ULA. For brevity I will shorten the IPv4 address to
> 192, the GUA to 2001 and the ULA to fd5f  below. I will only change
> the
> DNS AAAA record in the following, the network configuration on
> server/client or the A records never change. Server and client have
> always working IPv4 and IPv6 GUA and ULA.
> 
> Test with mount:
> ----------------
> Using a plain "mount  -t nfs4 server:/locals /mnt/disk1/" on the
> client
> gives depending on the DNS entries for the server the expected
> source/target selection:
> 
> Server DNS entry|	client address used to mount
> 2001		|	2001
> fd5f		|	fd5f
> 2001+fd5f	|	fd5f
> 
> So in all cases RFC 6724/3484 is observed selecting the addresses.
> Please note that the server has two AAAA records (multi-homed) in the
> last test.
> 
> Test with autofs:
> -----------------
> A map lookup will yield "-fstype=nfs4,rw,intr,nosuid,soft,nodev
> server:/locals"
> for the mount. Now I change again the servers AAAA records with the
> following result:
> 
> Server DNS entry|	client address used to mount
> 2001		|	2001
> fd5f		|	fd5f
> 2001+fd5f	|	192
> 
> For a multi-homed NFS4 server autofs apparently falls back to IPv4
> although valid IPv6 options exist. As shown above just mounting
> without
> autofs would stick to RFC 6724/3484 instead. I believe that autofs
> should 
> also select fd5f ULAs in the multi-homed case.
> 
> Is this a known behaviour ? Do any workarounds exist ? I could not
> find
> anything.
> 
> I tried to compile autofs 5.1.1 with --with-libtirpc because
> of https://bugs.launchpad.net/ubuntu/+source/autofs/+bug/1101779 but
> could not get the binary to work. I filed a bug report for the
> behaviour
> described above 
> https://bugs.launchpad.net/ubuntu/+source/autofs/+bug/1564380
> but suspect that this is better suited for this list.
> 
> Best Regards
> 
> Christof
> 
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