From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chr Subject: Re: IPv6 unique local address flushes on up/down Date: Tue, 25 Mar 2008 18:16:31 +0100 Message-ID: <200803251816.31709.chunkeey@web.de> References: <200803251557.21563.chunkeey@web.de> <200803251707.52528.chunkeey@web.de> <20080326.012039.59874360.yoshfuji@linux-ipv6.org> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-2022-jp" Content-Transfer-Encoding: 7bit Cc: hostap@lists.shmoo.com, netdev@vger.kernel.org To: YOSHIFUJI Hideaki / =?iso-2022-jp?q?=1B=24B5HF=231QL=40=1B=28B?= Return-path: Received: from fmmailgate01.web.de ([217.72.192.221]:49839 "EHLO fmmailgate01.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755185AbYCYRSQ (ORCPT ); Tue, 25 Mar 2008 13:18:16 -0400 In-Reply-To: <20080326.012039.59874360.yoshfuji@linux-ipv6.org> Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: On Tuesday 25 March 2008 17:20:39 YOSHIFUJI Hideaki / 吉藤英明 wrote: > In article <200803251707.52528.chunkeey@web.de> (at Tue, 25 Mar 2008 17:07:52 +0100), Chr says: > > On Tuesday 25 March 2008 16:24:28 YOSHIFUJI Hideaki / 吉藤英明 wrote: > > > In article <200803251557.21563.chunkeey@web.de> (at Tue, 25 Mar 2008 > > > > 15:57:21 +0100), Chr says: > > > > Now my question, which _one_ should we fix the applications or the > > > > stack?! I think the network stack, but I don't know if there are RFC > > > > about this issue... or is there already some flag/setting which I've > > > > missed so far? > > > > > > Well..., in fact, this is known as an uneasy-to-fix issue. > > > The behavior han not been changed for long time, so you definately > > > need to have work-around for this issue, anyway. > > > > > > From specification point of view, we need to re-perform DAD (duplicate > > > address detection) after down-up cycle or even link-down and up. > > > One possible way is to add "tentative" flag for static addresses > > > (instead of purging them) when the interface is going down and > > > reperform DAD for all of such addresses when the interface is coming > > > up. If the link is being down, we might want to use "Optimistic" DAD > > > instead. > > > > Ah yeah, ok... I guess... alright! ... > > > > but another question, about this issue form the userspace side. > > > > Since I'm going to use the stateful DHCPv6 way... I'm wondering how I can > > set the tentative flag from userspace? > > Tentative flag cannot be set from userspace. > So, if we're going this way, we might need new flag for "admin" or > "static" or something alike for manual / static addresses > (including link-local addresses, probably). > > --yoshfuji ok, this is a blocker... so, what about a "static flag" per interface instead of per addresses (maybe add something like /proc/sys/net/ipv6/conf/ethX/address_flush). So that on the first initialization of the interface (modprobe time) we create always generate a link-local address (like now)... But then on every down/up cycle we check the _new_ static flag. if it is not set then we do the _old_ behaviour... (flushing everything) and if it is set we just leave everything in place.... (and on "up", we just use the old link-local again instead of making a new one) Will this work? or are there some pitfalls with this approach? Regards, Christian