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>
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 005b22f..c916568d 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -1112,11 +1112,34 @@
return true;
}
+static int mld_force_mld_version(const struct inet6_dev *idev)
+{
+ /* Normally, both are 0 here. If enforcement to a particular is
+ * being used, individual device enforcement will have a lower
+ * precedence over 'all' device (.../conf/all/force_mld_version).
+ */
+
+ if (dev_net(idev->dev)->ipv6.devconf_all->force_mld_version != 0)
+ return dev_net(idev->dev)->ipv6.devconf_all->force_mld_version;
+ else
+ return idev->cnf.force_mld_version;
+}
+
+static bool mld_in_v2_mode_only(const struct inet6_dev *idev)
+{
+ return mld_force_mld_version(idev) == 2;
+}
+
+static bool mld_in_v1_mode_only(const struct inet6_dev *idev)
+{
+ return mld_force_mld_version(idev) == 1;
+}
+
static bool mld_in_v1_mode(const struct inet6_dev *idev)
{
- if (dev_net(idev->dev)->ipv6.devconf_all->force_mld_version == 1)
- return true;
- if (idev->cnf.force_mld_version == 1)
+ if (mld_in_v2_mode_only(idev))
+ return false;
+ if (mld_in_v1_mode_only(idev))
return true;
if (idev->mc_v1_seen && time_before(jiffies, idev->mc_v1_seen))
return true;
@@ -1223,7 +1246,6 @@
return -EINVAL;
idev = __in6_dev_get(skb->dev);
-
if (idev == NULL)
return 0;
@@ -1236,6 +1258,10 @@
return -EINVAL;
if (len == MLD_V1_QUERY_LEN) {
+ /* Ignore v1 queries */
+ if (mld_in_v2_mode_only(idev))
+ return 0;
+
/* MLDv1 router present */
max_delay = msecs_to_jiffies(ntohs(mld->mld_maxdelay));
