netdev - Re: [RFC PATCH 06/10] ipv6: Avoid deleting RTF_CACHE route from ip6_route

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Message-ID: <20150420193304.GD2416462@devbig242.prn2.facebook.com>
Date:	Mon, 20 Apr 2015 12:33:05 -0700
From:	Martin KaFai Lau <kafai@...com>
To:	David Miller <davem@...emloft.net>
CC:	<netdev@...r.kernel.org>, <hannes@...essinduktion.org>,
	<kernel-team@...com>
Subject: Re: [RFC PATCH 06/10] ipv6: Avoid deleting RTF_CACHE route from
 ip6_route_del()

On Mon, Apr 20, 2015 at 02:23:05PM -0400, David Miller wrote:
> From: Martin KaFai Lau <kafai@...com>
> Date: Fri, 10 Apr 2015 18:54:09 -0700
> 
> > Before patch 'Allow pmtu update on /128 via gateway route',
> > RTF_CACHE route was not created for DST_HOST.  It also requires changes on both
> > delete code path and rt6_select() code patch.
> > 
> > This patch fixes the delete code path to avoid deleting the RTF_CACHE
> > route by 'ip -6 r del...'
> > 
> > Signed-off-by: Martin KaFai Lau <kafai@...com>
> > Reviewed-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
> 
> If a cached route was created in response to say a PMTU event, and
> it's a clone/copy/cow of the route we are being asked to delete,
> it absolutely should be removed.
> 
> In fact this is a critically important aspect of removing routes
> from the table.
When a non-clone routes are removed, its clones are removed together by
fib6_prune_clones() in fib6_del().

Hence, 'ip -6 r del' will remove a route and its clones.
'ip -6 r flush table cache will only remove RTF_CACHE routes.

I will fix up the commit message.

Thanks,
--Martin
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