netdev - Re: echo > 0 .../disable_ipv6 broken in 2.6.37-rc4

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Date:	Wed, 08 Dec 2010 15:13:30 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Brian Haley <brian.haley@...com>
Cc:	netdev@...r.kernel.org, Mahesh Kelkar <maheshkelkar@...il.com>,
	Lorenzo Colitti <lorenzo@...gle.com>,
	Stephen Hemminger <shemminger@...tta.com>
Subject: Re: echo > 0 .../disable_ipv6 broken in 2.6.37-rc4

Brian Haley <brian.haley@...com> writes:

> This got broken in 2.6.34-rc1, and the most obvious culprit is this,
> although I haven't bisected it:
>
> commit dc2b99f71ef477a31020511876ab4403fb7c4420
> Author: stephen hemminger <shemminger@...tta.com>
> Date:   Mon Feb 8 19:48:05 2010 +0000
>
>     IPv6: keep permanent addresses on admin down
>
>     Permanent IPV6 addresses should not be removed when the link is
>     set to admin down, only when device is removed.
>
>     When link is lost permanent addresses should be marked as tentative
>     so that when link comes back they are subject to duplicate address
>     detection (if DAD was enabled for that address).
>
>     Other routing systems keep manually configured IPv6 addresses
>     when link is set down.
>
> Even though there was a bugfix update, it didn't help.
>
> I unfortunately won't be able to look at this more until at least Friday,
> I couldn't come up with a quick patch just looking quickly at
> addrconf_ifdown().

This is almost certainly it.
ip link set lo down
ip link set lo up

Is enough to break ping6 ::1.

I get the feeling the loopback address was not actually tested and
there is something different about it.

Eric
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