From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761921AbYBACL7 (ORCPT ); Thu, 31 Jan 2008 21:11:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754083AbYBACLt (ORCPT ); Thu, 31 Jan 2008 21:11:49 -0500 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:54979 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753960AbYBACLs (ORCPT ); Thu, 31 Jan 2008 21:11:48 -0500 Date: Thu, 31 Jan 2008 18:12:09 -0800 (PST) Message-Id: <20080131.181209.193710785.davem@davemloft.net> To: davidn@davidnewall.com Cc: kaber@trash.net, kadlec@blackhole.kfki.hu, jeff.chua.linux@gmail.com, linux-kernel@vger.kernel.org, ole@ans.pl, cups-bugs@easysw.com, netfilter-devel@vger.kernel.org Subject: Re: cups slow on linux-2.6.24 From: David Miller In-Reply-To: <47A26C12.9020801@davidnewall.com> References: <47A21945.2050005@trash.net> <47A26C12.9020801@davidnewall.com> X-Mailer: Mew version 5.2 on Emacs 22.1 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: David Newall Date: Fri, 01 Feb 2008 11:17:14 +1030 > Patrick McHardy wrote: > > Jozsef Kadlecsik wrote: > >> Strange, but there are a lot of incorrect checksum packets. How does > >> it come on the loopback interface? > > > > Loopback doesn't perform full checksumming, so thats expected. > > The question remains: How do loopback packets get incorrect checksum? > Where and how can they get corrupted? There are zeros there, which is an incorrect checksum most of the time. Tcpdump is just not knowledgable about this and tries to validate the checksum as if it were computed correctly.