From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sowmini Varadhan Subject: Re: why are IPv6 addresses removed on link down Date: Tue, 13 Jan 2015 10:00:48 -0500 Message-ID: <20150113150048.GA28371@oracle.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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Hannes Frederic Sowa , YOSHIFUJI Hideaki , Stephen Hemminger , "netdev@vger.kernel.org" To: David Ahern Return-path: Received: from userp1040.oracle.com ([156.151.31.81]:20948 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751378AbbAMPBD (ORCPT ); Tue, 13 Jan 2015 10:01:03 -0500 Content-Disposition: inline In-Reply-To: <54B53187.7080306@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: 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. --Sowmini