make a service systemd unit follow the interface state

[Anton Gubarkov]

Hi,

I have a rather stupid server that fails to resume its listening on the interface when the interface cycles down/up.
I have a unit for this server that WantedBy multi-user.target and everything works fine when this service is started while my notebook is connected online.

I want the service to stop when my zerotier interface goes down. It is pretty easy achieved by adding BindTo=sys-subsystem-net-devices-ztzlge64hc.device into the [Unit] section.
I also want the service to start every time the interface goes up. I can't figure out how to do it.

I tried After=sys-subsystem-net-devices-ztzlge64hc.device, WantedBy=sys-subsystem-net-devices-ztzlge64hc.device - to no avail...

there is a vague reference that I can use udev events to start the service, however I couldn't find any documentation about it. Anyway, I have a systemd device unit that follows the interface's state...