packets with syn/fin vs pf_norm.c

[Dag-Erling Smørgrav]

Jesper Wallin <jesper at hackunite.net> writes:
> First of all, I know that not dropping SYN/FIN isn't really a big deal, it
> just makes no sense. But since it doesn't make any sense, I don't see
> the reason why not to discard them.

It is not invalid for a TCP segment to have both SYN and FIN set.  See
for instance RFC 1644.

> I'm running pf on FreeBSD 5.4-RELEASE-p3 and I scrub any traffic. I've
> read some other posts on google and as far as I can tell, clearly invalid
> packets (like packets with SYN/RST set) is discared while scrub simply
> remove the FIN bit on packets with SYN/FIN.

It shouldn't, at least not unconditionally.

DES
-- 
Dag-Erling Smørgrav - des at des.no