Packet filtering for 4.3BSD ?

[Patrick Barron]

I have a TCP/IP gateway running 4.3BSD, and I've just been told that it
has to be able to filter packets based on UDP and TCP port numbers, and
possibly on source and destination IP addresses.  Has anyone already modified
4.3BSD to do this sort of thing?  If so, I'd like to see the code...

Thanks,
--Pat Barron
  CMU Software Engineering Institute
  Systems and Network Engineering