This code is heavily based on, even stolen from Dug Song's excellent fragroute utility. I've taken a perfectly good application and converted it into a packet editing library for my own needs. Any bugs are my fault. Any praises really should go to Dug. Please consider all files here under the original fragroute LICENSE, with the added caveat that any changes are: Copyright 2008-2010, Aaron Turner Copyright 2013, Fred Klassen - AppNeta Notes: Fragroute runs as a daemon which intercepts packets by modifying the host operating systems routing table, redirecting packets destined to the target IP over the loopback interface. Packets reaching the loopback interface are then read using libpcap/BPF filter processed according to the fragroute rule set and then resent out the configured interface. libfragroute works differently. First, we do away with any changes to the host routing table. Secondly, packets are not sent out any interface, but are read back by the caller. The API should look something like this: ctx = fragroute_init(mtu, ); // init library // process a packet fragroute_process(ctx, char *pktbuff, int pktsize) // read resulting fragments while ((ret = fragroute_read(ctx, char **fragment)) > 0) { // do something with fragment } else { // no more fragments }