fatal: ssh_dispatch_run_fatal: Connection reset by peer [preauth]

[Damien Miller]

On Mon, 4 May 2015, Christian Hesse wrote:

> Hello everybody,
> 
> I have systemd set up to listen on ssh socket (:::22), the connection is
> handled to sshd via socket activation. Usually this works perfectly fine.
> 
> However the service is checked from nagios. Sometimes the host logs:
> 
> systemd[1]: Started OpenSSH Per-Connection Daemon ([::1]:60865).
> systemd[1]: Starting OpenSSH Per-Connection Daemon ([::1]:60865)...
> systemd[1]: Started OpenSSH Per-Connection Daemon (127.0.0.1:41286).
> systemd[1]: Starting OpenSSH Per-Connection Daemon (127.0.0.1:41286)...
> sshd[2854]: Connection closed by ::1 [preauth]
> sshd[2855]: fatal: ssh_dispatch_run_fatal: Connection reset by peer [preauth]
> 
> Looks like this happens if we have two incoming connection (::1 and
> 127.0.0.1 are checked) at the some time.
> Why does this happen? Who's fault is it? As these are TCP connections I would
> expect it is not a problem to know what packet belongs to what connection.

You might need to look at server debug output and/or tcpdumps to see
what is going on here, but it looks like whatever is making the connections
is gracefully closing one but unceremoniously dropping the other.

BTW openssh HEAD has a more useful error message for connections closed
by TCP reset.

-d