Relaiable ssh tunnel via systemd

[Thomas Güttler]

We try to run a reliable ssh tunnel vis systemd.

This is the unit configuration file:

{{{
[Unit]
Description=Tunnel For %i
After=network.target

[Service]
User=autossh
ExecStart=/usr/bin/ssh -o "ExitOnForwardFailure yes" -o "ServerAliveInterval 60" -N -R 40443:installserver:40443 -R 
8080:installserver:8080
ExecStartPre=-/usr/bin/ssh tunnel@%i "for pid in  $$(ps -u tunnel | grep sshd| cut -d' ' -f1); do kill -9 $$pid; echo 
kill old ssh process p
Restart=always
RestartSec=5s
StartLimitInterval=0

[Install]
WantedBy=multi-user.target
}}}

Unfortunately on some hosts we see this warning again and again:

Mar 13 23:11:14 remotehost sshd[10938]: error: bind: Address already in use
Mar 13 23:11:14 remotehost sshd[10938]: error: channel_setup_fwd_listener: cannot listen to port: 40443
Mar 13 23:11:14 remotehost sshd[10938]: error: bind: Address already in use
Mar 13 23:11:14 remotehost sshd[10938]: error: channel_setup_fwd_listener: cannot listen to port: 8080

Since we kill the old tunnel before starting a new, I don't understand why this error message occurs.

Any hints?

-- 
Thomas Guettler http://www.thomas-guettler.de/