I have been tracking this issue in Ubuntu at:
https://bugs.launchpad.net/bugs/1752411
The root cause of this issue is a bug in 'host', in certain
circumstances the host command hangs and never returns. I can reproduce
this reliably.
The main case I have found is when an interface is up, but the link is
still down and a default route is installed in the state 'linkdown'.
This only happens if that is the route used to send packets to a
nameserver listed in resolv.conf
I haven't yet managed to debug what causes host to fail internally and
never timeout in this case, but a workaround is to modify
avahi-daemon-check-dns.sh to launch host under the 'timeout' command
with a 5 second timeout to ensure it doesn't block forever.
The real issue in host needs to be fixed, though, I have a machine that
reproduces this issue reliably if anyone is experience in bind9-host
debugging and I can reproduce it on demand.
- Trent
