Re: Migration with "--p2p --tunnelled" hanging in v6.9.0

On Wed, Nov 25, 2020 at 10:55 AM Christian Ehrhardt <christian.ehrhardt(a)canonical.com&gt; wrote: > > On Tue, Nov 24, 2020 at 4:30 PM Peter Krempa <pkrempa(a)redhat.com&gt; wrote: > > > > On Tue, Nov 24, 2020 at 16:05:53 +0100, Christian Ehrhardt wrote: > > > Hi, > > > > [...] > > BTW to reduce the scope what to think about - I have rebuilt 6.8 as > well it works. > Thereby I can confirm that the offending change should be in between > 6.8.0 -> 6.9.0. I was able to get this working in git bisect builds from git between v6.8 / v6.9. I identified the following offending commit: 7d959c30 rpc: Fix virt-ssh-helper detection Ok that makes a bit of sense, first we had in 6.8 f8ec7c84 rpc: use new virt-ssh-helper binary for remote tunnelling That makes it related to tunneling which matches our broken use-case. The identified commit "7d959c30 rpc: Fix virt-ssh-helper detection" might finally really enable the new helper and that is then broken? With that knowledge I was able to confirm that it really is the native mode $ virsh migrate --unsafe --live --p2p --tunnelled h-migr-test qemu+ssh://testkvm-hirsute-to/system?proxy=netcat <works> $ virsh migrate --unsafe --live --p2p --tunnelled h-migr-test qemu+ssh://testkvm-hirsute-to/system?proxy=native <hangs> I recently discussed with Andrea if we'd need apparmor rules for virt-ssh-helper, but there are no denials nor libvirt log entries related to virt-ssh-helper. But we don't need such rules since it is spawned on the ssh login and not under libvirtd itself. PS output of the hanging receiving virt-ssh-helper (looks not too unhappy): Source: 4 0 41305 1 20 0 1627796 23360 poll_s Ssl ? 0:05 /usr/sbin/libvirtd 0 0 41523 41305 20 0 9272 4984 poll_s S ? 0:02 \_ ssh -T -e none -- testkvm-hirsute-to sh -c 'virt-ssh-helper 'qemu:///system'' Target 4 0 213 1 20 0 13276 4132 poll_s Ss ? 0:00 sshd: /usr/sbin/sshd -D [listener] 0 of 250-500 startups 4 0 35148 213 20 0 19048 11320 poll_s Ss ? 0:02 \_ sshd: root@notty 4 0 35206 35148 20 0 2584 544 do_wai Ss ? 0:00 \_ sh -c virt-ssh-helper qemu:///system 0 0 35207 35206 20 0 81348 26684 - R ? 0:34 \_ virt-ssh-helper qemu:///system I've looked at it with strace [1] and gdb for backtraces [2] - it is not dead or stuck and keeps working. Could it be just so slow that it appears to hang until it times out? Or is the event mechanism having issues and it wakes up too rarely?