From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brian Haley Subject: Re: [PATCH] IPv6: optimize echo reply checksum calculation Date: Fri, 10 Nov 2006 12:51:19 -0500 Message-ID: <4554BC17.8020809@hp.com> References: <20061108221332.GI29920@ftp.linux.org.uk> <45536622.90708@hp.com> <20061109.151402.15590179.davem@davemloft.net> <4554A811.5060402@hp.com> <20061110173422.GM29920@ftp.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: David Miller , netdev@vger.kernel.org Return-path: Received: from atlrel8.hp.com ([156.153.255.206]:33974 "EHLO atlrel8.hp.com") by vger.kernel.org with ESMTP id S1161906AbWKJRvV (ORCPT ); Fri, 10 Nov 2006 12:51:21 -0500 To: Al Viro In-Reply-To: <20061110173422.GM29920@ftp.linux.org.uk> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Al Viro wrote: > On Fri, Nov 10, 2006 at 11:25:53AM -0500, Brian Haley wrote: >> Since the only difference between echo requests and echo replies is the >> ICMPv6 type value (which is a difference of 1), just subtracting one >> from the request checksum will result in the correct checksum for the reply. > > Um, no. That will *not* result in correct checksum. Please, RTFRFC 1071. I verified this works for echo request/reply on my IA64 box, double-checked with ethereal/wireshark. Is there something specific in RFC 1071 that I should be looking for? -Brian