From 58c0ecfd8d9871cfa35bcdbf3e7b3ee9ca62ea67 Mon Sep 17 00:00:00 2001
From: Daniel Borkmann <dborkman@redhat.com>
Date: Wed, 4 Sep 2013 00:19:40 +0200
Subject: [PATCH] net: ipv6: mld: implement RFC3810 MLDv2 mode only

RFC3810, 10. Security Considerations says under subsection 10.1.
Query Message:

  A forged Version 1 Query message will put MLDv2 listeners on that
  link in MLDv1 Host Compatibility Mode. This scenario can be avoided
  by providing MLDv2 hosts with a configuration option to ignore
  Version 1 messages completely.

Hence, implement a MLDv2-only mode that will ignore MLDv1 traffic:

  echo 2 > /proc/sys/net/ipv6/conf/ethX/force_mld_version  or
  echo 2 > /proc/sys/net/ipv6/conf/all/force_mld_version

Note that <all> device has a higher precedence as it was previously
also the case in the macro MLD_V1_SEEN() that would "short-circuit"
if condition on <all> case.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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