Some rtnetlink applications

Waiting for interface up and down by binding to RTMGRP_LINK and watching for link up/down [when the network driver supports the netif_carrier* interface in 2.4 this allows HA failover and watching for network problems]
Maintaining an copy of the routing table.
Maintaining a table of the local IP addresses.
...

Waiting for interface up and down by binding to RTMGRP_LINK and watching for link up/down [when the network driver supports the netif_carrier* interface in 2.4 this allows HA failover and watching for network problems]