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Date:      Mon, 6 May 2002 17:28:57 +0200
From:      "Karsten W. Rohrbach" <karsten@rohrbach.de>
To:        Jens Rehsack <rehsack@liwing.de>
Cc:        Michael Riexinger <mailinglists@grindking.de>, freebsd-stable@freebsd.org
Subject:   Re: ipfilter problem
Message-ID:  <20020506172856.A97107@mail.webmonster.de>
In-Reply-To: <3CD67F4E.E7A27EEE@liwing.de>; from rehsack@liwing.de on Mon, May 06, 2002 at 03:04:14PM %2B0200
References:  <20020504223450.GA1025@grind.grind.dom> <20020505152314.B73550@mail.webmonster.de> <20020505133204.GA667@grind.grind.dom> <20020505184630.A76286@mail.webmonster.de> <3CD5B662.26298116@liwing.de> <20020506020820.A82377@mail.webmonster.de> <3CD64534.672CD6A7@liwing.de> <20020506114555.C91849@mail.webmonster.de> <3CD67F4E.E7A27EEE@liwing.de>

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Jens Rehsack(rehsack@liwing.de)@2002.05.06 15:04:14 +0000:
> "Karsten W. Rohrbach" wrote:
> > pass in quick on isp0 proto tcp from any to any port =3D 80 flags S/SA =
keep state
> >                         # we want state added when establishing a
> >                         # session, not for every tcp packet that passes
> >                         # this rule
> If you read your own statement above you can cut the flags, because all d=
ynamic
> rules added "quick" before this rule/line, so this rule is never parsed f=
or
> any already matched ...

valid point, my reasoning was wrong (worse: it hurts so bad, that i
wonder why nobody else intervened ;-)

the reasoning about "why flags S/SA" boils down to the point that no
out-of-session packet should be allowed to create a state. session
establishment is restricted to SYN/SYN+ACK packets, nothing more. IIRC,
the state will just hang there until it times out, but it will be there
and use a slot in the state table; ipfilter will not pass a matching
packet because of the incomplete session state which is tracked in the=20
state table, anyway.

regards,
/k

--=20
> Experience is a teacher that gives the examination first and the
> lesson afterwards.=20
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