DNS not working for IPv6-only host names when using Miredo

[Martin Rosenau]

When IPv6 is only available using "miredo" (I don't know about the case of native IPv6) "systemd-resolve" seems not to query for AAAA entries when AF_UNSPEC or simply a NULL pointer is passed to getaddrinfo().

This has the effect that tools that support both IPv4 and IPv6 and use AF_UNSPEC or NULL will simply fail to connect IPv6-only servers when the name has to be resolved via DNS.

(The problem was occurring with the Firefox web browser.)

(The AAAA record is however queried if AF_INET6 is explicitly passed to that function.)

A possible quick fix is to modify the /etc/nsswitch.conf:

  Before: "hosts: ... resolve [!UNAVAIL=return] dns"
  After: "hosts: ... resolve dns"
  Or even remove "resolve" completely: "hosts: ... dns"

However it would be better to create the possibility to configure how the system should behave in the case of AF_UNSPEC:

- Only ask for the A record
- Only ask for the AAAA record
- Ask for both, prefer A
- Ask for both, prefer AAAA

[Steve Langasek (vorlon)]

systemd-resolve is not part of resolvconf, it is part of systemd; reassigning.

A possible quick fix is to modify the /etc/nsswitch.conf:

  Or even remove "resolve" completely: "hosts: ... dns"

We are not installing libnss-resolve by default in Ubuntu, we are using systemd-resolved as a DNS resolver only. Perhaps the solution for you is to remove the libnss-resolve package from your system? Why do you have it installed?

[Martin Rosenau (martin-djr)]

At least I did not install this packet manually.

Maybe there is another packet that I have installed depending on libnss-resolve...