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

[Ian Kent <raven@themaw.net>]

On Mon, 2016-04-11 at 18:35 +0200, Christof Koehler wrote:
> Oops, replace 0.25.2 by 0.2.5 ... Sorry.
> 
> On Mon, Apr 11, 2016 at 06:32:41PM +0200, Christof Koehler wrote:
> > Hello,
> > 
> > I will try to consolidate the answer in a single email without
> > messing
> > up the quoting too much.
> > 
> > > But we can't really start to work out what needs to be done unless
> > > libtirpc is being used.
> > 
> > > And I think the best chance is to use 5.1.1 and possibly back port
> > > any
> > > changes.
> > 
> > > As I say, the only other thing we can do is add some targeted
> > > debug
> > > logging and see if we can spot what is going wrong.
> > 
> > I will then stick to the plan to defer this
> > until ubuntu 16.04 has been released which should contain autofs
> > 5.1.1
> > and libtirpc 0.25.2. From the libtirpc git repo and the sourceforge
> > page
> > I see that 0.25.2 is from 2014, but not even debian unstable is
> > using a newer version (and from the changelog things like gss_api
> > support are the main changes ?). 
> > 
> > I will use a virtual machine with ubuntu 16.04 (or if preferable
> > debian 
> > testing or unstable) and then start experimenting. In that
> > environment we 
> > can do to autofs and also libtirpc (and nfs-common if necessary)
> > whatever 
> > is needed to get the necessary information. 
> > 
> > I will let you know when I start with that and what the baseline
> > with
> > the original packages of the distribution and simple rebuild of
> > autofs
> > --with-libtirpc is.
> > 
> > > > Apr  8 18:05:25 core324 automount[963]: get_nfs_info: called
> > > > with host
> > > > core330(fd5f:852:a27c:1261:2000::118) proto 6 version 0x40
> > > > Apr  8 18:05:25 core324 automount[963]: get_nfs_info: called
> > > > with host
> > > > core330(2001:638:708:1261:2000::118) proto 6 version 0x40
> > > > Apr  8 18:05:25 core324 automount[963]: mount(nfs): no hosts
> > > > available
> > 
> > > Sadly that doesn't tell us much either, only that the rpc
> > > communication
> > > has failed to get a result in some expected way.
> > 
> > Well, at least it shows that this autofs built at least is somehow
> > aware of
> > all the different IP adresses and trying the IPv4 one first. Of
> > course
> > no other conclusions can be drawn from this.
> > 
> > > That's right, as I say the RPC communication isn't failing in an
> > > unexpected way so we aren't seeing any error messages.
> > > 
> > > About all that can be done is to add a patch that adds some extra
> > > logging to try and get to the bottom of it.
> > 
> > That should be possible with a virtual machine as mentioned above.
> > 
> > > The first thing that stands out is that if libtirpc is not being
> > > used
> > > all IPv6 hosts will be ignored because (my impression is that)
> > > glibc RPC
> > > doesn't support IPv6.
> > 
> > The libtirpc documentation says that libtirpc is needed for IPv6
> > ready
> > rpc support, http://nfsv4.bullopensource.org/doc/tirpc_rpcbind.php a
> > s
> > linked from sourceforge.
> > Might even be that glibc does actually no longer contain any rpc
> > functionality ?
> > https://archives.gentoo.org/gentoo-dev/message/186be8dc9753d18aafc9a
> > 5a616b3b991
> > This would be supported by information on the tirpc web page
> > mentioned
> > above.
> > 
> > As far as I understand your analysis you are saying the IPv6
> > mount in the "2001" case is just working by accident, right ?

Basically, yes.

The code that determines if there are multiple addresses for a host has
a mistake in it. If it was working correctly I think you would have seen
both mounts as IPv4.

Fixing that mistake is possibly going to be part of a larger change for
this so I'll leave it for now.

> > 
> > > It's mount.nfs(8) mounting from the IPv6 address (when given a
> > > host name
> > > not an address) in the former case and not autofs that's getting
> > > you an
> > > IPv6 mount. And, AFAICS, the mount.nfs your using does use
> > > libtirpc.
> > Yes.
> > # ldd /sbin/mount.nfs4|grep tirpc
> >         libtirpc.so.1 => /lib/x86_64-linux-gnu/libtirpc.so.1
> > (0x00007ffff7d9d000)
> > and libtirpc is a hard package dependency of nfs-common.
> > 
> > Best Regards
> > 
> > Christof
> > -- 
> > Dr. rer. nat. Christof Köhler       email: 
> > c.koehler@bccms.uni-bremen.de
> > Universitaet Bremen/ BCCMS          phone:  +49-(0)421-218-62334
> > Am Fallturm 1/ TAB/ Raum 3.12       fax: +49-(0)421-218-62770
> > 28359 Bremen  
> > 
> > PGP: http://www.bccms.uni-bremen.de/cms/people/c_koehler/
> > --
> > To unsubscribe from this list: send the line "unsubscribe autofs" in
> 
--
To unsubscribe from this list: send the line "unsubscribe autofs" in