ipv6: Drop packets for loopback address from outside of the box.

[ Based upon original report and patch by Karsten Keil.  Karsten
  has verified that this fixes the TAHI test case "ICMPv6 test
  v6LC.5.1.2 Part F". -DaveM ]

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 15 insertions, 0 deletions

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index e0a612bc9c4e..f422f7218e1c 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -367,6 +367,12 @@ static inline int ipv6_addr_any(const struct in6_addr *a)
                  a->s6_addr32[2] | a->s6_addr32[3] ) == 0); 
 }
 
+static inline int ipv6_addr_loopback(const struct in6_addr *a)
+{
+        return ((a->s6_addr32[0] | a->s6_addr32[1] |
+                 a->s6_addr32[2] | (a->s6_addr32[3] ^ htonl(1))) == 0);
+}
+
 static inline int ipv6_addr_v4mapped(const struct in6_addr *a)
 {
         return ((a->s6_addr32[0] | a->s6_addr32[1] |
diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index 4e5c8615832c..17eb48b8e329 100644
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -102,6 +102,15 @@ int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt
         if (hdr->version != 6)
                 goto err;
 
+        /*
+         * RFC4291 2.5.3
+         * A packet received on an interface with a destination address
+         * of loopback must be dropped.
+         */
+        if (!(dev->flags & IFF_LOOPBACK) &&
+            ipv6_addr_loopback(&hdr->daddr))
+                goto err;
+
         skb->transport_header = skb->network_header + sizeof(*hdr);
         IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);