This is a port of ifstated(8) from OpenBSD. From the manpage: *** The ifstated daemon runs commands in response to network state changes, which it determines by monitoring interface link state or running exter- nal tests. For example, it can be used with carp(4) to change running services or to ensure that carp(4) interfaces stay in sync, or with pf(4) to test server or link availability and modify translation or routing rules. *** It has been modified to use FreeBSD's kqueue/kevent mechanism and sysctl. Matthew George