tcpcontrol is a very fast TCP access controller, designed to be used
with ucspi-tcp/tcpserver.

tcpcontrol provides the same basic services as tcp-wrappers/tcpd
provides for inetd: logging connections; rejecting connections from
certain hosts; setting new environment variables for connections from
certain hosts.

tcpcontrol is built for speed. Its rules are compiled into a hashed
format, so you can easily deal with thousands of different hosts. It
takes advantage of the TCP environment variables set up by tcpserver, so
(unlike tcpd) it doesn't do any extra DNS or port 113 lookups.
