From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Duyck Subject: Re: [BUG] net/ipv4: inconsistent routing table Date: Wed, 5 Aug 2015 10:45:18 -0700 Message-ID: <55C24BAE.7090702@gmail.com> References: <55C1D207.3040905@iogearbox.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org To: Daniel Borkmann , Zang MingJie Return-path: In-Reply-To: <55C1D207.3040905@iogearbox.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 08/05/2015 02:06 AM, Daniel Borkmann wrote: > [ please cc netdev ] > > On 08/05/2015 10:56 AM, Zang MingJie wrote: >> Hi: >> >> I found a bug when remove an ip address which is referenced by a >> routing entry. >> >> step to reproduce: >> >> ip li add type dummy >> ip li set dummy0 up >> ip ad add 10.0.0.1/24 dev dummy0 >> ip ad add 10.0.0.2/24 dev dummy0 Okay, so up to this point you have 2 addresses on the same subnet that are now on dummy0. >> ip ro add default via 10.0.0.2/24 This makes the default route go through 10.0.0.2. >> ip ad del 10.0.0.2/24 dev dummy0 Then you remove 10.0.0.2 from the local system, however since 10.0.0.1 is on the same subnet dummy0 would still be the correct interface to access 10.0.0.2 it is just no longer local to the system. >> after deleting the secondary ip address, the routing entry still >> pointing to 10.0.0.2 You didn't delete the default routing entry so why would you expect it to change? All you did is remove 10.0.0.2 from the local system. I believe the assumption is that 10.0.0.2 is still out there somewhere, it just isn't on the local system anymore. >> # ip ro >> default via 10.0.0.2 dev dummy0 >> 10.0.0.0/24 dev dummy0 proto kernel scope link src 10.0.0.1 This matches up with what I would expect. 10.0.0.2 is the default gateway and it is accessible from dummy0 since 10.0.0.0/24 is accessible from dummy0. >> but actually, kernel considers the default route is directly connected. >> >> # ip ro get 1.1.1.1 >> 1.1.1.1 dev dummy0 src 10.0.0.1 >> cache I'm not sure how you came to the "directly connected" conclusion. It is still routing things out through 10.0.0.2 from 10.0.0.1. Maybe your example would work better if you used 10.0.0.1 and 10.0.1.1 instead. Then I think you might be able to better see that when you delete the second address the route would be broken. - Alex