Original Pre-Health Requriements

Router Requirements

A router is a node which has the routing feature turned on using lnetctl set routing 1 or the equivalent modprobe configuration.

1. Track the last time stamp any message was received on a local NI
2. if the NI hasn't received any traffic for a period of router_ping_timeout + MAX(live_router_check_interval, dead_router_check_interval) then it's marked down
   1. This is done so that other nodes using the gateway can mark the route down, given that avoid_asym_router_failure is set to 1.
3. Do not send messages to a peer which is marked down.
4. Set the peer status to up when messages are received
5. When messages are flowing through the router, query the peer NI a message is destined to every one second to determine if it has come back up again, and if so then set its status to alive.

Gateway Requirements

A gateway in this context is the peer NI created when adding a route on a node. For example: lnetctl route add --net tcp --gateway <gateway-NID>. Dealing with that peer-NI is somewhat of a special case.

1. Mark the gateway peer NI as down when the LND fails to send a message
   1. Note although the LND notifications happen for all peers peer NIs it is only pertinent on routers or for gateways.
2. Mark the gateway peer NI as up when we receive an unsolicited message or when we receive a REPLY for a PING sent from the router checker.
3. Mark the route as down if one of the gateway's interfaces, identified by the gateway peer NI, are down, provided the avoid_asym_router_failure is set to 1.

...