[IPV6]: Send ICMPv6 error on scope violations.

When an IPv6 router is forwarding a packet with a link-local scope source
address off-link, RFC 4007 requires it to send an ICMPv6 destination
unreachable with code 2 ("not neighbor"), but Linux doesn't. Fix below.

Signed-off-by: David L Stevens <dlstevens@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 3 deletions

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index f508171bab73..4704b5fc3085 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -463,10 +463,17 @@ int ip6_forward(struct sk_buff *skb)
                  */
                 if (xrlim_allow(dst, 1*HZ))
                         ndisc_send_redirect(skb, n, target);
-        } else if (ipv6_addr_type(&hdr->saddr)&(IPV6_ADDR_MULTICAST|IPV6_ADDR_LOOPBACK
-                                                |IPV6_ADDR_LINKLOCAL)) {
+        } else {
+                int addrtype = ipv6_addr_type(&hdr->saddr);
+
                 /* This check is security critical. */
-                goto error;
+                if (addrtype & (IPV6_ADDR_MULTICAST|IPV6_ADDR_LOOPBACK))
+                        goto error;
+                if (addrtype & IPV6_ADDR_LINKLOCAL) {
+                        icmpv6_send(skb, ICMPV6_DEST_UNREACH,
+                                ICMPV6_NOT_NEIGHBOUR, 0, skb->dev);
+                        goto error;
+                }
         }
 
         if (skb->len > dst_mtu(dst)) {