Red Hat Bugzilla – Bug 56767
sessions hang on exit
Last modified: 2007-04-18 12:38:27 EDT
I've noticed this problem for several releases of Red Hat and finally remembered to bugzilla it, since it's still present in a fully up-to-date RH 7.2 box. remote ssh sessions will occasionally "hang" for me when exiting. After I ssh into a remote system, do my work, and then type logout (or exit or...), the connection will remain open even though I'm no longer logged into the remote system. The only way to close the ssh session is to kill the ssh process on the client. I've not noticed any pattern about the server versions to which I'm connecting that exhibit this problem. Some are Red Hat, but I also see it with non-RH servers running various releases of openssh 2.x / 3.x.
If you started up background processes while logged in, they may still be connected to the pseudo-terminal which holds your login. sshd doesn't close the connection, because it has no way of knowing that backgrounded processes won't be sending data which you need to get.
I've had similar problems with skipjack that I downloaded and installed yesterday. Before with rh72 i've never had problems like this. A couple of times sshd have hanged and not returned my terminal when exiting, and one time it also stoped to accept new logins. I had to restart sshd at the machin locally. I have not seen any pattern of when it hangs so this comment is not of much use. I've seen this in /var/log/secure but I don't know if it's related: Apr 22 08:54:08 zigo2 sshd[916]: Server listening on 0.0.0.0 port 22. Apr 22 08:54:32 zigo2 sshd[1163]: Could not reverse map address 192.168.0.3. Apr 22 08:54:35 zigo2 sshd[1163]: Accepted password for root from 192.168.0.3 port 49809 ssh2 Apr 22 09:08:15 zigo2 sshd[1363]: Could not write ident string to 192.168.0.3 Apr 22 09:09:17 zigo2 sshd[1381]: Did not receive identification string from 192.168.0.3 Apr 22 09:12:44 zigo2 sshd[1393]: Did not receive identification string from 192.168.0.3 Apr 22 10:08:18 zigo2 sshd[1163]: session_input_channel_req: no session 0 req window-change Apr 22 10:08:35 zigo2 sshd[1886]: Could not reverse map address 192.168.0.3. Apr 22 10:08:37 zigo2 sshd[1886]: Accepted password for root from 192.168.0.3 port 57578 ssh2 Apr 22 10:09:07 zigo2 sshd[1163]: session_input_channel_req: no session 0 req window-change Apr 22 10:09:10 zigo2 last message repeated 2 times Apr 22 10:09:53 zigo2 sshd[916]: Received signal 15; terminating. Apr 22 10:12:01 zigo2 sshd[2057]: Server listening on 0.0.0.0 port 22. You can see the signal 15 where I went and restarted sshd at the console of the machine, before there is a strange message, and during this time I could not log in at all with ssh. Also I find it strange that is is listening on 0.0.0.0, but maybe that is what it should be. I can still login when it says that. I don't have any reverse lookup for 198.168.0.3 (and no line in /etc/hosts) yet since this is a fresh install. But it's still the case that it works 10 times and hangs the 11:th so I don't think that is the problem. Maybe I should open a new bug since I only see this in skipjack (openssh-3.1p1-2) and not in 7.2. ps. I'm pretty sure I don't have any background processes or anything when it happens.
Closing, since I've not seen lately