From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751265AbWDFQUy (ORCPT ); Thu, 6 Apr 2006 12:20:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751262AbWDFQUx (ORCPT ); Thu, 6 Apr 2006 12:20:53 -0400 Received: from adsl-67-116-42-147.dsl.sntc01.pacbell.net ([67.116.42.147]:29712 "EHLO avtrex.com") by vger.kernel.org with ESMTP id S1751265AbWDFQUw (ORCPT ); Thu, 6 Apr 2006 12:20:52 -0400 Message-ID: <44353F36.9070404@avtrex.com> Date: Thu, 06 Apr 2006 09:17:58 -0700 From: David Daney User-Agent: Mozilla Thunderbird 1.0.7 (Windows/20050923) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Janos Farkas CC: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, pgf@foxharp.boston.ma.us, freek@macfreek.nl Subject: Re: Broadcast ARP packets on link local addresses (Version2). References: <17460.13568.175877.44476@dl2.hq2.avtrex.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 06 Apr 2006 16:20:51.0412 (UTC) FILETIME=[12545140:01C65996] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Janos Farkas wrote: > On 2006-04-05 at 14:22:08, David Daney wrote: > >>The changes in this version are that it tests the source IP address >>instead of the destination. The test now matches the test described >>in the RFC. Also a small cleanup as suggested by Herbert Xu. >> >>Some comments on the first version of the patch suggested that I do >>'X' instead. Where 'X' was behavior different than that REQUIRED by >>the RFC (the RFC's always seem to capitalize the word 'required'). >> >>The reason that I implemented the behavior required by the RFC is so >>that a device running the kernel can pass compliance tests that >>mandate RFC compliance. > > > Sorry for chiming in this late in the discussion, but... Shouldn't it > be more correct to not depend on the ip address of the used network, > but to use the "scope" parameter of the given address? > RFC 3927 specifies the Ethernet arp broadcast behavior for only 169.254.0.0/16. Presumably you could set the scope parameter to local for addresses outside of that range or even for protocols other than Ethernet. Since broadcasting ARP packets usually adversely effects usable network bandwidth, we should probably only do it where it is absolutely required. The overhead of testing the value required by the RFC is quite low (3 machine instructions on i686 is the size of the entire patch), so using some proxy like the scope parameter would not even be a performance win. David Daney