fragroute intercepts, modifies, and rewrites egress traffic, implementing most of the attacks described in the Secure Networks "Insertion, Evasion, and Denial of Service: Eluding Network Intrusion Detection" paper. It features a simple ruleset language to delay, duplicate, drop, fragment, overlap, print, reorder, segment, source-route, or otherwise monkey with all outbound packets destined for a target host, with minimal support for randomized or probabilistic behaviour. This tool was written in good faith to aid in the testing of intrusion detection systems, firewalls, and basic TCP/IP stack behaviour.
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, network interface lookup and manipulation, and raw IP packet and Ethernet frame transmission.