From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Frederic Sowa Subject: Re: why are IPv6 addresses removed on link down Date: Tue, 13 Jan 2015 16:09:51 +0100 Message-ID: <1421161791.13626.33.camel@redhat.com> References: <54B4A7E4.7030301@gmail.com> <20150112231021.316648e3@urahara> <1421145346.13626.12.camel@redhat.com> <54B50873.4090907@miraclelinux.com> <54B50C71.7090007@miraclelinux.com> <1421152613.13626.24.camel@redhat.com> <54B53187.7080306@gmail.com> <20150113150048.GA28371@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: David Ahern , YOSHIFUJI Hideaki , Stephen Hemminger , "netdev@vger.kernel.org" To: Sowmini Varadhan Return-path: Received: from mx1.redhat.com ([209.132.183.28]:49836 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752277AbbAMPKD (ORCPT ); Tue, 13 Jan 2015 10:10:03 -0500 In-Reply-To: <20150113150048.GA28371@oracle.com> Sender: netdev-owner@vger.kernel.org List-ID: On Di, 2015-01-13 at 10:00 -0500, Sowmini Varadhan wrote: > On (01/13/15 07:53), David Ahern wrote: > > > > The current code seems inconsistent: I can put an IPv6 address on a > > link in the down state. On a link up the address is retained. Only > > on a subsequent link down is it removed. If DAD or anything else is > > the reason for the current logic then why allow an address to be > > assigned in the down state? Similarly that it currently seems to > > work ok then it suggests the right thing is done on a link up in > > which case a flush is not needed. > > > > Bottom line is there a harm in removing the flush? If there is no > > harm will mainline kernel take a patch to do that or is your > > backward compatibility concern enough to block it? > > Does some of this have to do with the manner in which this interacts > with SLAAC? I recall that there were two schools of thought for doing > DAD when SLAAC is present: one says it is sufficient to just do DAD > on the interface-id, the other requies DAD on the whole 128-bit IPv6 > address. I'm not sure which choice linux makes. Yes, it does have something to do with it. But I didn't understand what you meant by doing DAD on the interface-id. If you look at the patches I just posted, only addresses which are in link-local and not in permanent state will be flushed. I also need to do research on how to safely approach this, I don't know, yet. Bye, Hannes