We set up designate-mdns so that it listens on an IPv6 socket, by setting "listen = [::]:5354" in the [service:mdns] section of designate.conf. (The background is that we have IPv6, but no IPv4 connectivity between regions, and we want to set up public-facing nameservers that can get zone data from designate in another region.) BIND 9 is used as the public-facing nameserver.
When a zone is created, it is added to designate-mdns, and then BIND 9 is told to create the zone as a slave and retrieve its contents from designate-mdns via zone transfer from port 5354. This happens even when BIND 9 connects over IPv4 to 127.0.0.1. Here is an extract of syslog on our designate server that shows the problem:
Nov 23 06:55:36 designate-0 named[11565]: received control channel command 'addzone designate-test2.simon.leinen.ch { type slave; masters { 127.0.0.1 port 5354;}; file "slave.designate-test2.simon.leinen.ch.49b88ec2-03ab-4a4f-83c9-ef2136ec16e6"; };'
Nov 23 06:55:36 designate-0 named[11565]: client 127.0.0.1#52994: received notify for zone 'designate-test2.simon.leinen.ch'
Nov 23 06:55:36 designate-0 named[11565]: zone designate-test2.simon.leinen.ch/IN: notify from 127.0.0.1#52994: no serial
Nov 23 06:55:36 designate-0 named[11565]: zone designate-test2.simon.leinen.ch/IN: Transfer started.
Nov 23 06:55:36 designate-0 named[11565]: transfer of 'designate-test2.simon.leinen.ch/IN' from 127.0.0.1#5354: connected using 127.0.0.1#37097
Nov 23 06:55:36 designate-0 designate-mdns[12125]: Traceback (most recent call last):
Nov 23 06:55:36 designate-0 designate-mdns[12125]: File "/usr/lib/python2.7/dist-packages/eventlet/hubs/hub.py", line 457, in fire_timers
Nov 23 06:55:36 designate-0 designate-mdns[12125]: timer()
Nov 23 06:55:36 designate-0 designate-mdns[12125]: File "/usr/lib/python2.7/dist-packages/eventlet/hubs/timer.py", line 58, in __call__
Nov 23 06:55:36 designate-0 designate-mdns[12125]: cb(*args, **kw)
Nov 23 06:55:36 designate-0 designate-mdns[12125]: File "/usr/lib/python2.7/dist-packages/eventlet/greenthread.py", line 214, in main
Nov 23 06:55:36 designate-0 designate-mdns[12125]: result = function(*args, **kwargs)
Nov 23 06:55:36 designate-0 designate-mdns[12125]: File "/usr/lib/python2.7/dist-packages/designate/service.py", line 365, in _dns_handle_tcp_conn
Nov 23 06:55:36 designate-0 designate-mdns[12125]: host, port = addr
Nov 23 06:55:36 designate-0 designate-mdns[12125]: ValueError: too many values to unpack
When we change the listen option to 0.0.0.0:5354, the problem goes away.
[EDITED TO ADD:] We use Ubuntu Cloud Archive packages under Ubuntu 16.04 LTS. For Designate, we use the "pike" version of UCA. The rest of our OpenStack installation still runs Newton.
The line
host, port = addr
assumes that "addr" (which is returned from socket.accept()) is a pair (2-tuple). But according to https:/