From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: Should linux send netlink message as it is deleting that routing entry? Date: Fri, 11 Apr 2014 11:30:42 -0700 Message-ID: <20140411113042.4328c39c@nehalam.linuxnetplumber.net> References: <534654FE.3040804@gmail.com> <5347B2C4.6040103@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, "David S. Miller" , ebiederm@xmission.com, ja@ssi.bg, "Yang, Zhangle (Eric)" , "Tao, Yue" , "Zadoyan, Grant" , eric.dumazet@gmail.com, socketcan@hartkopp.net, hannes@stressinduktion.org, cwang@twopensource.com To: zhuyj Return-path: Received: from mail-pb0-f44.google.com ([209.85.160.44]:49841 "EHLO mail-pb0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752807AbaDKSaq (ORCPT ); Fri, 11 Apr 2014 14:30:46 -0400 Received: by mail-pb0-f44.google.com with SMTP id rp16so5727672pbb.31 for ; Fri, 11 Apr 2014 11:30:45 -0700 (PDT) In-Reply-To: <5347B2C4.6040103@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 11 Apr 2014 17:15:48 +0800 zhuyj wrote: > > With ubuntu 12.04, I run the following to reproduce this defect. > > > > 1) Configure an interface > > ifconfig eth1 150.0.0.1/24 up > > > > 2) Add routing entry via that interface address > > route add -net 200.0.0.0/24 gw 150.0.0.1 > > > > 3) Change the ip address on that interface as shown below. > > ifconfig eth1 151.0.0.1/24 up > > > > 4) Check netlink messages with "ip monitor all". There is no route > > delete netlink message. > > With IPv4 there are several cases where there is a non-notified implicit route withdrawal. This is not something that can be fixed. There are two issues: 1. with large backbone size route tables (ie 1M routes), the number of notification messages becomes a bottleneck and would be unreliable 2. the existing routing daemons (quagga, bird, etc) all understand/expect the existing semantics