Firewalls the libdnet way

 I will need to design firewalls for both *BSD and Linux based systems and
was thinking about learning how to do that using the firewall capabilites
included in the libdnet package, so I don't have to be learning two
different ways to basically do the same thing. Once the same functionality
it is inyected into the kernel it doesn't (or shouldn't?) really matter the
way in which it was done.

 I have searched the Net for any documentation more extensive than the mere
4 pages of bare API presentation in Mike Schiffman's book.

 Can anyone point me to a more comprehensive treatment of the topic?

 Thanks