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Date:      Sun, 3 Sep 2000 21:39:03 -0700
From:      "Crist J . Clark" <cjclark@reflexnet.net>
To:        Dragos Ruiu <dr@kyx.net>
Cc:        Bill Fumerola <billf@chimesnet.com>, Darren Reed <avalon@coombs.anu.edu.au>, Robert Watson <rwatson@FreeBSD.ORG>, Nicolas <list@rachinsky.de>, freebsd-security@FreeBSD.ORG
Subject:   Re: ipfw and fragments
Message-ID:  <20000903213903.Q62475@149.211.6.64.reflexcom.com>
In-Reply-To: <0009031819571V.20066@smp.kyx.net>; from dr@kyx.net on Sun, Sep 03, 2000 at 05:32:00PM -0700
References:  <Pine.NEB.3.96L.1000903094614.69440A-100000@fledge.watson.org> <200009032010.HAA15013@cairo.anu.edu.au> <20000903173136.S33771@jade.chc-chimes.com> <0009031819571V.20066@smp.kyx.net>

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On Sun, Sep 03, 2000 at 05:32:00PM -0700, Dragos Ruiu wrote:
> On Sun, 03 Sep 2000, Bill Fumerola wrote:
> > On Mon, Sep 04, 2000 at 07:10:46AM +1100, Darren Reed wrote:
> > 
> > > It never reassembles and doesn't hold them in a buffer until they're
> > > all received either.
> > 
> > Which I still think is the proper behavior for both ipfw and ipfilter.
> > 
> 
> You don't have to buffer until they're reassembled.

Hmmm... Wha'?

> If you want to be
> rigorous, you may have to buffer in the case when you don't receive 
> the first segment first (in which case you would have to buffer until you
> received the first fragment with the headers that will let the firewall 
> decide if it should let the fragments through or not) but in practice 
> this is an extreme corner case, so  imho, you can cheat a little 
> and use a heuristic and say you won't buffer and if you don't receive 
> the first frag first too bad (because in practice mis-sequencing
> almost never occurs in the wild) - I don't know if there are any 
> RFC rules regarding this anyway, so you may even be able to
> declare this correct behaviour.  :-)

See RFC791, sec 3.2 and RFC1122, sec 3.3.2, 3.3.3.

Oh, and a totally unrelated topic, whose MUA puts _both_ my From: and
Reply-To: addresses in the recipients ensuring that I have received
each message in this thread twice?
-- 
Crist J. Clark                           cjclark@alum.mit.edu


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