TRIPP is a utility to rewrite incoming and outgoing IP packets.
Since it can rewrite both headers and payload, it can be used to
configure the tcp/ip stack behavior in order to perform various
tasks mainly intended for network tests, simulations and development.
It is configured via a small rule-based language, which allows the user to intercept
packets, set arbitrary header values, increment or decrement numeric header fields,
set an arbitrary payload, rewrite parts of the payload, or fragment, multiply, or drop packets.
It is totally user-level and doesn't require any kernel module.