Provided in PR pkg/20058 by V. Hari <bit5hift at ethernet dot tk>, slightly
edited by me.
libdnet provides a simplified, portable interface to several low-level
networking routines, including
* network address manipulation
* kernel arp(4) cache and route(4) table lookup and manipulation
* network firewalling (IP filter, ipfw, ipchains, pf, ...)
* network interface lookup and manipulation
* raw IP packet and Ethernet frame transmission