From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A279BC3A5A1 for ; Thu, 22 Aug 2019 22:57:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5A31D21848 for ; Thu, 22 Aug 2019 22:57:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405459AbfHVW5o (ORCPT ); Thu, 22 Aug 2019 18:57:44 -0400 Received: from shards.monkeyblade.net ([23.128.96.9]:50114 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405430AbfHVW5n (ORCPT ); Thu, 22 Aug 2019 18:57:43 -0400 Received: from localhost (unknown [IPv6:2601:601:9f80:35cd::d71]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id A12AB153952E3; Thu, 22 Aug 2019 15:57:42 -0700 (PDT) Date: Thu, 22 Aug 2019 15:57:42 -0700 (PDT) Message-Id: <20190822.155742.2103304070969355809.davem@davemloft.net> To: liudongxu3@huawei.com Cc: kuznet@ms2.inr.ac.ru, yoshfuji@linux-ipv6.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] net: Add the same IP detection for duplicate address. From: David Miller In-Reply-To: <20190821032000.10540-1-liudongxu3@huawei.com> References: <20190821032000.10540-1-liudongxu3@huawei.com> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Thu, 22 Aug 2019 15:57:42 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dongxu Liu Date: Wed, 21 Aug 2019 11:20:00 +0800 > The network sends an ARP REQUEST packet to determine > whether there is a host with the same IP. > Windows and some other hosts may send the source IP > address instead of 0. > When IN_DEV_ORCONF(in_dev, DROP_GRATUITOUS_ARP) is enable, > the REQUEST will be dropped. > When IN_DEV_ORCONF(in_dev, DROP_GRATUITOUS_ARP) is disable, > The case should be added to the IP conflict handling process. > > Signed-off-by: Dongxu Liu Even documents like RFC 5227 talk about there being a zero source protocol address here (read the last two paragraphis of section 1.2. "relationship to 826"): ==================== An ARP Probe with an all-zero 'sender IP address' may ostensibly be merely asking an innocent question ("Is anyone using this address?"), but an intelligent implementation that knows how IPv4 Address Conflict Detection works should be able to recognize this question as the precursor to claiming the address. ==================== I do not understand why we have to add a special case for an implementation that has decided, after so many decades of our existing behavior, to put something of than zero in the source protocol address. I'm not applying this, I do not see a legitimate justification for this change at all. Sorry.