This can be done on any systemd based system, this example is on a Raspberry PI running Raspbian (jessie).
# apt-get install autossh
Generate SSH key and copy it over
# ssh-keygen
# ssh-copy-id root@server
Create /etc/systemd/system/autossh.service
[Unit] Description=AutoSSH service After=network.target [Service] User=root Environment=AUTOSSH_PIDFILE=/tmp/autossh.pid ExecStart=/usr/bin/autossh -M 0 -f -N -T -q -o ServerAliveInterval=30 -o ServerAliveCountMax=3 -R 9993:localhost:22 root@server PIDFile=/tmp/autossh.pid Restart=always [Install] WantedBy=multi-user.target
Reload systemd
# systemctl daemon-reload
Enable/Start Service
# systemctl enable autossh
# systemctl start autossh
Now from “server” you should be able to reach your PI
# ssh localhost -p 9993