>FreeBSD and NetBSD support having packet filters as LKMs, so the
>register/deregister thing is kind of mandatory.

FYI, there is already a port of pf for FreeBSD 5:
  http://www.freshports.org/security/pf/

It has been ported by Pyun YongHyeon:
  http://pf4freebsd.love2party.net/

I do not know if it supports the register/deregister feature.

It would be nice if Kame and pf4freebsd could work together ;-)

Regards,
  Vincent
=20