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

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Date:	Tue, 25 Mar 2008 17:07:52 +0100
From:	Chr <chunkeey@....de>
To:	YOSHIFUJI Hideaki /
	 吉藤英明 
	<yoshfuji@...ux-ipv6.org>
Cc:	hostap@...ts.shmoo.com, netdev@...r.kernel.org, chunkeey@....de
Subject: Re: IPv6 unique local address flushes on up/down

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?

Because the DHCPv6 Client uses the ip utility to add the ipv6 address too.
And unlike the _static_ setting for the router, this _stateful_ 
autoconf-address should be flushed on ifup/down, right? 

And according to the manual page of my iproute (debian sid - from 2008-01-08). 
the ip utility doesn't have this "set flag xy for address zw" capability at 
all... 

so how can I _possibly_ set it, or prevent from being set? 
Or do I miss some good and obvious point here again?! 

Regards,
	Christian


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