From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kristian Evensen Subject: Re: Wrong MAC in redirected packet Date: Wed, 25 Mar 2009 20:56:10 +0100 Message-ID: <49CA8C5A.1030908@gmail.com> References: <17e3a8f80903250727q739fac53r6325a8eefff96a97@mail.gmail.com> <17e3a8f80903250800q15964da1gaf24ff1670ba3802@mail.gmail.com> <49CA8A6B.1020603@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netfilter-devel@vger.kernel.org To: Jan Engelhardt Return-path: Received: from mail-ew0-f165.google.com ([209.85.219.165]:37530 "EHLO mail-ew0-f165.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754552AbZCYTwA (ORCPT ); Wed, 25 Mar 2009 15:52:00 -0400 Received: by mail-ew0-f165.google.com with SMTP id 9so238269ewy.37 for ; Wed, 25 Mar 2009 12:51:58 -0700 (PDT) In-Reply-To: Sender: netfilter-devel-owner@vger.kernel.org List-ID: Jan Engelhardt skrev: > On Wednesday 2009-03-25 20:47, Kristian Evensen wrote: > >> However, I have noticed a similar problem when using my module on incoming >> packets in PREROUTING (on the multihomed receiver), the IP adress is changed >> (accoring to my dmesg-output) but then they are not heard from again. >> > > Probably dropped due to L3 or L4 checksum mismatches. While we try to > change the checksum, I have not verified it for all cases. > > Hm, I am noe sure. I recalculate the checksum (using csum_replace4 for l3 and inet....replace4 for l4) after modifying the destination IP, and when used with OUTPUT the checksum is correct. Since tcpdump/Wireshark outputs the packets before they are modified I haven't been able to verify this though. -Kristian