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 16:06:52 -0500 Message-ID: <4554E9EC.1070803@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> <4554BC17.8020809@hp.com> <20061110180534.GN29920@ftp.linux.org.uk> <20061110182031.GO29920@ftp.linux.org.uk> <4554CD40.3030801@hp.com> <20061110191715.GP29920@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 atlrel7.hp.com ([156.153.255.213]:23529 "EHLO atlrel7.hp.com") by vger.kernel.org with ESMTP id S966118AbWKJVmw (ORCPT ); Fri, 10 Nov 2006 16:42:52 -0500 To: Al Viro In-Reply-To: <20061110191715.GP29920@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 02:04:32PM -0500, Brian Haley wrote: >> Al Viro wrote: >>> so -= 1 is broken even on ia64 and it's *always* broken on big-endian >>> boxen. >> It's not broken in ia64, I've tested that, just don't have an x86 for >> testing right now. Can you please apply these changes and prove it's >> broken? This little trick has been done in other UNIXes for years >> without any problems. > > Could you fscking read what you've replied to? Your -=1 will turn 0 > into 0xffff instead of correct 0xfffe. IOW, it's broken in 1:65536 > cases. I looked again at your previous email: > Note that even on little-endian you want > 3 -> 2 > 2 -> 1 > 1 -> 0xffff > 0 -> 0xfffe That doesn't look right to me, but I'll take your word that there's one edge case out there I don't see (even though this worked on Alpha). Forget about the patch then. -Brian