netdev - Re: 3.6 routing cache regression, multicast loopback broken

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Date:	Thu, 22 Nov 2012 15:04:16 +0100
From:	Maxime Bizon <mbizon@...ebox.fr>
To:	Julian Anastasov <ja@....bg>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: 3.6 routing cache regression, multicast loopback broken


On Wed, 2012-11-21 at 02:35 +0200, Julian Anastasov wrote:

Hi,

> 	Do you also have CONFIG_IP_MROUTE enabled? I see the

I don't

> problem with caching both "RTCF_MULTICAST | RTCF_LOCAL" and
> "RTCF_MULTICAST" flags to same place but I'm not sure in the
> sequence of route lookups for your setup. ip_mc_output does
> not care about RTCF_LOCAL when CONFIG_IP_MROUTE is disabled,
> so in this case it should loop the packet even on wrong
> caching (without RTCF_LOCAL flag).

but the problem here was that dst was using ip_output() instead of
ip_mc_output().

> 	Can you try the following patch. If it does not
> solve the problem we have to add some debugs in __mkroute_output.
> And I'm not sure if this is fatal only when CONFIG_IP_MROUTE
> is enabled, I have to spend more time to check the code.
> As an optimization, the patch avoids lookup for fnhe
> when multicast is not cached because multicasts are
> not redirected and they do not learn PMTU.
> 
> 	The patch is not tested. I'll update the commit
> message after your tests.

the patch fixes the problem, and it looks valid to me.

thanks !

-- 
Maxime


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