netdev - Re: [PATCH] ipv6: address preservation on link down

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Date:	Fri, 9 Jan 2009 10:02:06 +0200
From:	"Rémi Denis-Courmont" 
	<remi.denis-courmont@...ia.com>
To:	"ext Stephen Hemminger" <shemminger@...tta.com>
Cc:	David Miller <davem@...emloft.net>, yoshfuji@...ux-ipv6.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH] ipv6: address preservation on link down

On Friday 09 January 2009 03:14:15 ext Stephen Hemminger, you wrote:
> When an interface goes down, IPV6 deletes all addresses unlike IPV4. This
> is a problem since it can break routing protocols and other applications.
> It looks like this was done to handle DAD, but is a big stick solution when
> other code is possible.
>
> The following patch changes the behaviour to delete link local addresses
> but keep all configured addresses and restart DAD when interface comes back
> up.

Let alone the backward compatibility problem for a minute. I have two _other_ 
problems with this:

1/ If DAD should fail when the interface is brought back up, wouldn't all the 
EAU-64 autoconfigured address become invalid, rather than just the link-local 
one?

2/ In some case the link-local address is assigned by userland, no different 
from the other ones. At least miredo is behaving this way.

-- 
Rémi Denis-Courmont
Maemo Software, Nokia Devices R&D
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