From: Patrick McHardy <kaber@trash.net>
To: Luca Pesce <pesce.luca@gmail.com>
Cc: netfilter-devel@vger.kernel.org
Subject: Re: xt_TCPMSS target dropping SYN packets with data: suggested mod
Date: Wed, 15 Jul 2009 17:38:05 +0200 [thread overview]
Message-ID: <4A5DF7DD.2050908@trash.net> (raw)
In-Reply-To: <873dce860907090641n31254e30g48886aefbbc6474e@mail.gmail.com>
Luca Pesce wrote:
> Hi all,
> I have a question and a possible patch/mod for target TCPMSS (xt_TCPMSS.c).
> At the very beginning of function tcpmss_mangle_packet(), the skb containing the
> TCP SYN packet is checked to see if it is containing data (on a side note, SYN
> with data is quite unusual...); if so, the packet is drastically dropped.
> The reason is explained in RR's comment to the code, I am copy/pasting the
> beginning of this function with the length check at the bottom of this mail.
> RR says that we cannot change MSS on a packet which is already carrying data
> (it would be too late): could we relax this check, seeing if the tcp payload is
> less than the MSS we are about to set?
We probably could change that. I'm wondering though, did you actually
see this in real life? It doesn't seem like a very useful feature,
considering all the stacks supporting syn cookies.
next prev parent reply other threads:[~2009-07-15 15:38 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-09 13:41 xt_TCPMSS target dropping SYN packets with data: suggested mod Luca Pesce
2009-07-15 15:38 ` Patrick McHardy [this message]
2009-07-16 7:15 ` Luca Pesce
2009-07-16 11:17 ` Pascal Hambourg
2009-07-17 7:44 ` Luca Pesce
2009-07-17 9:46 ` Pascal Hambourg
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