Public bug reported:

Hello everybody,

I would like to report the following behaviour which is IMO a bug.

1. Working scenario without autofs:
NFS client with ipv4 and static GUA (global unique address) and  ULA (unique 
local address) ipv6 addresses. NFS server also with ipv4  and static GUA and 
ULA. DNS contains complete and consistent (forward/reverse lookup) information.

So considering ipv6 both server and client are multi-homed which is a legal 
configuration 
with ipv6. Without autofs a simple mount -tnfs4 -o proto=tcp6 ... on the client 
works as expected, the correct source and destination addresses are chosen 
according to RFC 6724/3484 (removing/adding server ULA/GUA AAAA record in DNS 
to test).

2. Working scenario with autofs:
DNS AAAA entry for the server is either the GUA or the ULA but not both. The 
server is not multi-homed. In this case mounting via autofs uses ipv6 and the 
correct IP addresses (ULA or GUA) are selected for the mount according to the 
RFC.

3. Non-working scenario with autofs:
DNS contains ULA and GUA (two AAAA entries) for server, the server is 
multi-homed. However, due to RFC 6724/3484 address selection rules are clearly 
defined. Attempting to mount the same export as in 2. in this situation reverts 
to ipv4 instead of using ipv6 with source and destination addresses according 
to the RFC. No other configuration changes on server or client.


After reading https://bugs.launchpad.net/ubuntu/+source/autofs/+bug/1101779 I 
tried to recompile an autofs package with --with-libtirpc. Unfortunately this 
recompiled package fails with

automount[20444]: open_mount:247: parse(sun): cannot open mount module nfs 
(/usr/lib/x86_64-linux-gnu/autofs/mount_nfs.so: undefined symbol: 
clnt_dg_create)
automount[20444]: lookup(file): failed to open parse context

If someone has a solution for this and thinks --with-libtirpc would help
or yield additional information I can test again.

I cannot test the scenario mentioned in 1101779 at the moment in a
production environment by removing the servers ipv4 address.


What you expected to happen: Mount via ipv6 in scenario 3 as in scenario 2.
What happened instead: Mount via ipv4 in scenario 3.

Best Regards

Christof

# lsb_release -rd
Description:    Ubuntu 14.04.4 LTS
Release:        14.04

# apt-cache policy autofs
autofs:
  Installed: 5.0.7-3ubuntu3.2
  Candidate: 5.0.7-3ubuntu3.2
  Version table:
 *** 5.0.7-3ubuntu3.2 0
        500 http://de.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 
Packages
        100 /var/lib/dpkg/status
     5.0.7-3ubuntu3 0
        500 http://de.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages

** Affects: autofs (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1564380

Title:
  autofs reverts to mount via ipv4 for multi-homed ipv6 server

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