From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rick Jones Subject: Re: Bad TCP checksum error Date: Fri, 26 Oct 2007 09:59:16 -0700 Message-ID: <47221CE4.70103@hp.com> References: <1a41e0840710260041u4ebeb1e3h521e740a78f7e0bf@mail.gmail.com> <1a41e0840710260903w33516f62kc53e5eb56e424d69@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: netfilter-devel@vger.kernel.org, netdev@vger.kernel.org, linux-net@vger.kernel.org, linux-kernel@vger.kernel.org, davidsen@tmr.com To: Gaurav Aggarwal Return-path: Received: from palrel12.hp.com ([156.153.255.237]:39117 "EHLO palrel12.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760187AbXJZQ7S (ORCPT ); Fri, 26 Oct 2007 12:59:18 -0400 In-Reply-To: <1a41e0840710260903w33516f62kc53e5eb56e424d69@mail.gmail.com> Sender: netfilter-devel-owner@vger.kernel.org List-Id: netfilter-devel.vger.kernel.org Checksum Offload on the NIC(s) can complicate things. First, if you are tracing on the sender, the tracepoint is before the NIC has computed the full checksum. IIRC only a partial checksum is passed-down to the NIC when CKO is in use. So, making certain your trace is from the "wire" or the receiver rather than the sender would be a good thing, and trying again with CKO disabled on the interface(s) (via ethtool) might be something worth looking at. Ultimately, doing the partial checksum modificiations in a CKO-friendly manner might be a good thing. rick jones