ipv6: don't accept node local multicast traffic from the wire

Erik Hugne's errata proposal (Errata ID: 3480) to RFC4291 has been
verified: http://www.rfc-editor.org/errata_search.php?eid=3480

We have to check for pkt_type and loopback flag because either the
packets are allowed to travel over the loopback interface (in which case
pkt_type is PACKET_HOST and IFF_LOOPBACK flag is set) or they travel
over a non-loopback interface back to us (in which case PACKET_TYPE is
PACKET_LOOPBACK and IFF_LOOPBACK flag is not set).

Cc: Erik Hugne <erik.hugne@ericsson.com>
Cc: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 0 deletions

diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index e33fe0ab2568..2bab2aa59745 100644
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -118,6 +118,18 @@ int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt
             ipv6_addr_loopback(&hdr->daddr))
                 goto err;
 
+        /* RFC4291 Errata ID: 3480
+         * Interface-Local scope spans only a single interface on a
+         * node and is useful only for loopback transmission of
+         * multicast.  Packets with interface-local scope received
+         * from another node must be discarded.
+         */
+        if (!(skb->pkt_type == PACKET_LOOPBACK ||
+              dev->flags & IFF_LOOPBACK) &&
+            ipv6_addr_is_multicast(&hdr->daddr) &&
+            IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 1)
+                goto err;
+
         /* RFC4291 2.7
          * Nodes must not originate a packet to a multicast address whose scope
          * field contains the reserved value 0; if such a packet is received, it