ssh connection hangs after < 1s

1
votes

I have a weird ssh issue that I haven't encountered previously.

Remote connections to a machine (theseus) hang after < 1s.

  • Connecting from theseus to theseus (ssh user@localhost or ssh user@ip) is fine.
  • Connecting from theseus => other machine is fine.
  • theseus => other machine => theseus connects but hangs after <1s.
  • session negotiation looks ok in /var/log/auth.log (sshd says "session opened for user", systemd-logind says "new session # of user", there doesn't seem to be an error after that)
  • from othermachine ssh user@theseus 'while date +%s.%N; do sleep 0.1 || break; done' shows ~0.75s worth of output
  • the process continues running on theseus after this time, but I get no output, I can ctrl + c the process

I reinstalled ssh-server and client on theseus and the only edit I've made to sshd_config is UseDns no.

sshopenssh