I did some testing using strace and looking at backtraces of why "host" is stuck, and it's not immediately clear to me why it's getting stuck. Will need to look more in depth into it tracing it's actual execution - it's multi threaded and using poll so not super straight forward from the trace for someone unfamiliar with the code-base.
I did test that when it happens, the network interfaces are up and systemd-resolved is started - and I can see a sendmsg/recvmsg appear to succeed to the systemd stub resolver and my local SNS server. I also tried explicitly setting the timeout with host -W 5 (this should be the default, but wanted to test as there is a -w indefinite option). However the 'host' command always works when I log into the system while the other commands are still stuck in the background - so something strange is going on. What does work, is executing 'host' under /usr/bin/timeout. Given the severity of this issue (makes startup hang without SSH for several minutes, and blocks everything else from starting up seemingly forever), I would suggest that we should ship a fix for bionic to use timeout to work around the issue for now. /usr/lib/avahi/avahi-daemon-check-dns.sh : dns_has_local() OUT=`LC_ALL=C /usr/bin/timeout 5 host -t soa local. 2>&1` ** Changed in: openconnect (Ubuntu) Status: Confirmed => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1752411 Title: bind9-host, avahi-daemon-check-dns.sh hang forever causes network connections to get stuck To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/1752411/+subscriptions -- ubuntu-bugs mailing list email@example.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs