This HOWTO explains how to use the libiptc library included in the iptables package. This document can show you how to use short C or C++ programs to query the internal structure of the firewalling code, to check chains and rules, packet and byte counters, and in a second phase, if you are a little "brave", to modify them.
If you have suggestions to help make this document better, please submit your ideas to me at the following address: firstname.lastname@example.org.
While I wrote this HOWTO, I developed a simple bandwith meter using user-defined chains to get the data to be measured. This idea was conceived looking at monitor.pl, a simple perl program for bandwith measurement, written by Stef Coene at http://www.docum.org. I recommend this site to people interested in bandwidth control and measurement.