netdev - Re: IPv6 unique local address flushes on up/down

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Message-Id: <20080326.012039.59874360.yoshfuji@linux-ipv6.org>
Date:	Wed, 26 Mar 2008 01:20:39 +0900 (JST)
From:	YOSHIFUJI Hideaki / 吉藤英明 
	<yoshfuji@...ux-ipv6.org>
To:	chunkeey@....de
Cc:	hostap@...ts.shmoo.com, netdev@...r.kernel.org,
	yoshfuji@...ux-ipv6.org
Subject: Re: IPv6 unique local address flushes on up/down

In article <200803251707.52528.chunkeey@....de> (at Tue, 25 Mar 2008 17:07:52 +0100), Chr <chunkeey@....de> says:

> On Tuesday 25 March 2008 16:24:28 YOSHIFUJI Hideaki / 吉藤英明 wrote:
> > In article <200803251557.21563.chunkeey@....de> (at Tue, 25 Mar 2008 
> 15:57:21 +0100), Chr <chunkeey@....de> 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

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