look up:
http://l7-filter.sourceforge.net/


and i wan't to add my own drivers.
examples:i have a md5628 modem,but routeros can't support it
so i wan't to complie driver for my modem.
but i don't know how to load drivers modules in routeros?
who can help me?


i use lfs ,use kernel 2.4.23 and gcc 2.95

http://www.mikrotik.com/forum/viewtopic.php?t=949

there are lots of open source projects to build up a router.

regards.
  matthias