netdev - Re: [PATCH] ipv4: do not cache looped multicasts

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Message-Id: <20121122.160821.1053003508424182997.davem@davemloft.net>
Date:	Thu, 22 Nov 2012 16:08:21 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	ja@....bg
Cc:	netdev@...r.kernel.org, mbizon@...ebox.fr
Subject: Re: [PATCH] ipv4: do not cache looped multicasts

From: Julian Anastasov <ja@....bg>
Date: Thu, 22 Nov 2012 23:04:14 +0200

> 	Starting from 3.6 we cache output routes for
> multicasts only when using route to 224/4. For local receivers
> we can set RTCF_LOCAL flag depending on the membership but
> in such case we use maddr and saddr which are not caching
> keys as before. Additionally, we can not use same place to
> cache routes that differ in RTCF_LOCAL flag value.
> 
> 	Fix it by caching only RTCF_MULTICAST entries
> without RTCF_LOCAL (send-only, no loopback). As a side effect,
> we avoid unneeded lookup for fnhe when not caching because
> multicasts are not redirected and they do not learn PMTU.
> 
> 	Thanks to Maxime Bizon for showing the caching
> problems in __mkroute_output for 3.6 kernels: different
> RTCF_LOCAL flag in cache can lead to wrong ip_mc_output or
> ip_output call and the visible problem is that traffic can
> not reach local receivers via loopback.
> 
> Reported-by: Maxime Bizon <mbizon@...ebox.fr>
> Tested-by: Maxime Bizon <mbizon@...ebox.fr>
> Signed-off-by: Julian Anastasov <ja@....bg>

Applied and queued up for -stable, thanks!
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