link_watchdog - Atlantic777/mpudp GitHub Wiki

Monitor link status. There are at least 3 states for a link.

1. Link is present in the OS, but down
2. Link is present in the OS, and up
3. Link is present, UP and running

This are possible transitions:

1. up and running link disappears
2. present link which was up becomes down
3. present link disappears
4. up and running link goes down

Assume all links present, up and running for now.