tcpdump

Tcpdump uses libpcap, a system-independent interface for user-level packet capture. The program is loosely based on SMI's "etherfind" although none of the etherfind code remains. It was originally as part of an ongoing research project to investigate and improve tcp and internet gateway performance. The parts of the program originally taken from Sun's etherfind were later re-written. To insure that there would be no vestige of proprietary code in tcpdump, these pieces were written from the specification given by the manual entry, with no access to the source of tcpdump or etherfind.