Comment 0 for bug 1584850

We got a situation where IPv6 was being used in a MAAS 1.9 subnet and the node failed to get a FQDN for its hostname.

Specifically, the call that failed was pyton's socket.gethostbyaddr(<hostname>), which is used by socket.getfqdn():

ubuntu@rectangular-structure:~$ python -c "import socket; print socket.gethostname()"
rectangular-structure

ubuntu@rectangular-structure:~$ python -c "import socket; print socket.gethostbyaddr(socket.gethostname())"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
socket.herror: [Errno 1] Unknown host
ubuntu@rectangular-structure:~$

A DNS traffic capture showed this:
146 2.859261 192.168.120.8 -> 198.18.173.40 DNS 88 Standard query 0x0e2a AAAA rectangular-structure.maas
147 2.859422 198.18.173.40 -> 192.168.120.8 DNS 146 Standard query response 0x0e2a AAAA rectangular-structure.maas AAAA 2001:4878:c1e0:603a:225:90ff:fe30:4b6c NS maas A 198.18.173.40
149 2.859831 192.168.120.8 -> 198.18.173.40 DNS 134 Standard query 0xd332 PTR c.6.b.4.0.3.e.f.f.f.0.9.5.2.2.0.a.3.0.6.0.e.1.c.8.7.8.4.1.0.0.2.ip6.arpa
150 2.860065 198.18.173.40 -> 192.168.120.8 DNS 196 Standard query response 0xd332 No such name PTR c.6.b.4.0.3.e.f.f.f.0.9.5.2.2.0.a.3.0.6.0.e.1.c.8.7.8.4.1.0.0.2.ip6.arpa SOA use1.akamai.com

We can see that the PTR for the IPv6 address does not exist. Looking at /etc/bind in the MAAS node, that's confirmed:
$ grep rectangular -r etc/
etc/bind/maas/zone.168.192.in-addr.arpa:8.120.168.192.in-addr.arpa. IN PTR rectangular-structure.maas.
etc/bind/maas/zone.maas:rectangular-structure IN A 192.168.120.8
etc/bind/maas/zone.maas:rectangular-structure IN AAAA 2001:4878:c1e0:603a:225:90ff:fe30:4b6c

I found it curious that MAAS would have the AAAA record, but not the corresponding PTR one, so I decided to file this bug about it.