netdev - Re: [PATCH 1/3] [IPV6]: Event type in addrconf

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Date:	Sat, 22 Mar 2008 17:38:43 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	den@...nvz.org
Cc:	yoshfuji@...ux-ipv6.org, netdev@...r.kernel.org, kaber@...sh.net,
	containers@...ts.osdl.org, dlezcano@...ibm.com,
	benjamin.thery@...l.net
Subject: Re: [PATCH 1/3] [IPV6]: Event type in addrconf_ifdown is mis-used.

From: "Denis V. Lunev" <den@...nvz.org>
Date: Tue, 18 Mar 2008 17:35:23 +0300

> addrconf_ifdown is broken in respect to the usage of how parameter. This
> function is called with (event != NETDEV_DOWN) and (2) on the IPv6 stop.
> It the latter case inet6_dev from loopback device should be destroyed.
> 
> Signed-off-by: Denis V. Lunev <den@...nvz.org>

The code purposefully treats "2" specially because when IPV6 routes
are destroyed they are changed to point to the loopback device's
inet6_dev object.

This allows statistic bumping code to not have to check if it has a
NULL inet6_dev pointer or not, because that's now impossible.

Since ipv6 is not unloadable, addrconf_cleanup(), and thus the
"how == 2" case can only occur when ipv6 fails to load properly.
The only real consequence of this bug is that if ipv6 fails
to load properly, a subsequent successfull load of ipv6 will
leak the loopback device's inet6_dev object, which isn't that
much of a big deal.

I understand that for namespaces you have to deal with multiple
loopback devices, but you'll need to solve that problem while
still handling the wish of the ipv6 stack for inet6_dev objects
of loopback devices to be permanent and guarenteed to always
be around for the sake of statistics bumping.

I thus can't apply any of these patches until those issues are
resolved.
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