RE: [PATCH] IGMP: Inhibit reports for local multicast groups

Hi Andrew
IGMP snooping is designed to prevent hosts on a local network from receiving traffic for a multicast group they have not explicitly joined.   Link-Local multicast traffic should not have an IGMP client since it is reserved for routing protocols.  One would expect that IGMP snooping needs to ignore local multicast traffic in the reserved range intended for routers since there should be no IGMP client to make "join" requests.

Regards

Philip

-----Original Message-----
From: Andrew Lunn [mailto:andrew@lunn.ch]
Sent: Thursday, August 13, 2015 5:06 PM
To: Philip Downey
Cc: David Miller; kuznet@ms2.inr.ac.ru; jmorris@namei.org; yoshfuji@linux-
ipv6.org; kaber@trash.net; linux-kernel@vger.kernel.org;
netdev@vger.kernel.org
Subject: Re: [PATCH] IGMP: Inhibit reports for local multicast groups

On Thu, Aug 13, 2015 at 02:48:23PM +0000, Philip Downey wrote:

quoted

Hi David
Thanks for taking the time to review and comment.
This is my first upstream request so please forgive any ignorance on my

part.   I have added a new proposed commit wording below with a view to
agreeing the content before resubmitting the patch.

quoted

I hope it is sufficient to address your concerns.

   IGMP: Inhibit reports for local multicast groups

    The range of addresses between 224.0.0.0 and 224.0.0.255
    inclusive, is reserved for the use of routing protocols and other
    low-level topology discovery or maintenance protocols, such as
    gateway discovery and group membership reporting.  Multicast
    routers should not forward any multicast datagram with   destination
    addresses in this range, regardless of its TTL.

    Currently, IGMP reports are generated for this reserved range of
    addresses even though a router will ignore this information since
    it has no purpose.

Hi Philip

What about switches which are doing IGMP snooping?

     Andrew