[Unit]
Description=Phone Home Reverse SSH Service
ConditionPathExists=|/usr/bin
After=network.target

[Service]
User=sshtunnel
ExecStart=/usr/bin/ssh -NTC -o ServerAliveInterval=60 -o ExitOnForwardFailure=yes -o StrictHostKeyChecking=no -i /home/sshtunnel/.ssh/id_rsa -R 22223:localhost:22 user@remote-ssh-server
# Restart every >2 seconds to avoid StartLimitInterval failure
RestartSec=3
Restart=always

[Install]
WantedBy=multi-user.target