netdev - Re: [PATCH 1/1] igmp: fix ip_mc_clear_src to not reset ip_mc

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Date:	Mon, 16 May 2011 14:03:59 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	vfalico@...hat.com
Cc:	mmarek@...e.cz, kuznet@....inr.ac.ru, pekkas@...core.fi,
	jmorris@...ei.org, yoshfuji@...ux-ipv6.org, kaber@...sh.net,
	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, dlstevens@...ibm.com
Subject: Re: [PATCH 1/1] igmp: fix ip_mc_clear_src to not reset
 ip_mc_list->sf{mode,count}

From: Veaceslav Falico <vfalico@...hat.com>
Date: Sun, 15 May 2011 18:59:45 +0200

> ip_mc_clear_src resets the imc->sfcount and imc->sfmode, without taking into
> account the current number of sockets listening on that multicast struct, which
> can lead to bogus routes for local listeners.
> 
> On NETDEV_DOWN/UP event, if there were 3 multicast listeners for that interface's
> address, the imc->sfcount[MCAST_EXCLUDE] will be reset to 1. And after that a
> listener socket destroys, multicast traffic will not be delivered to local
> listeners because __mkroute_output drops the local flag for the route (by
> checking ip_check_mc).
> 
> Signed-off-by: Veaceslav Falico <vfalico@...hat.com>

David, please take a look at this.  Thanks.

> diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
> index 1fd3d9c..b14f371 100644
> --- a/net/ipv4/igmp.c
> +++ b/net/ipv4/igmp.c
> @@ -1775,9 +1775,6 @@ static void ip_mc_clear_src(struct ip_mc_list *pmc)
>  		kfree(psf);
>  	}
>  	pmc->sources = NULL;
> -	pmc->sfmode = MCAST_EXCLUDE;
> -	pmc->sfcount[MCAST_INCLUDE] = 0;
> -	pmc->sfcount[MCAST_EXCLUDE] = 1;
>  }
>  
>  
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