netdev - Re: [PATCH] IPv4 Multicast: prevent reception of mcast frames from unjoined groups

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Date:	Fri, 11 Jul 2008 13:35:49 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	David Stevens <dlstevens@...ibm.com>
Cc:	davem@...emloft.net, jmorris@...ei.org, kaber@...sh.net,
	kuznet@....inr.ac.ru, netdev@...r.kernel.org,
	netdev-owner@...r.kernel.org, pekkas@...core.fi,
	yoshfuji@...ux-ipv6.org
Subject: Re: [PATCH] IPv4 Multicast: prevent reception of mcast frames from
	unjoined groups

On Fri, Jul 11, 2008 at 10:16:41AM -0700, David Stevens wrote:
> netdev-owner@...r.kernel.org wrote on 07/11/2008 08:21:13 AM:
> 
> > The current ipv4 multicast code incorrectly allows frames destined to 
> any
> > multicast group to be received on any socket that is bound to 
> INADDR_ANY,
> > regardless of weather or not that socket is subscribed to that group.
> 
> NACK. As Alexey already quoted from me, multicasting just doesn't work
> that way, since the beginning of time.
> 
>                                                                 +-DLS

So you're saying that if I take a process, call bind, specifying INADDR_ANY, and
then call setsockopt(...,IP_ADD_MEMBERSHIP,...) specifying a multicast group X,
that I can expect to recieve messages from other multicast addresses that other
processes in the system have joined to?  That doesn't seem at all correct, and
it contradicts what you and I discussed privately.  As the code currently
stands, if you do the above in process A, joining mcast group X, and then start
a second process on the same system, joining mcast group Y, process A will
recieve mcast group Y frames.

Neil

-- 
/****************************************************
 * Neil Horman <nhorman@...driver.com>
 * Software Engineer, Red Hat
 ****************************************************/
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