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

[Christof Koehler <christof.koehler@bccms.uni-bremen.de>]

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 as
> linked from sourceforge.
> Might even be that glibc does actually no longer contain any rpc
> functionality ?
> https://archives.gentoo.org/gentoo-dev/message/186be8dc9753d18aafc9a5a616b3b991
> 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 ?
> 
> > 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/
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-- 
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/
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