[TIPC]: Links now validate destination node specified by incoming messages.

This fix prevents link flopping and name table inconsistency problems arising
when a node is assigned a different <Z.C.N> value than it used previously.
(Changing the <Z.C.N> value causes other nodes to have two link endpoints
sending to the same MAC address using two different destination <Z.C.N> values,
requiring the receiving node to filter out the unwanted messages.)

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Per Liden <per.liden@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/link.c

@@ -1720,6 +1720,11 @@ void tipc_recv_msg(struct sk_buff *head, struct tipc_bearer *tb_ptr)
 			link_recv_non_seq(buf);
 			continue;
 		}
+		
+		if (unlikely(!msg_short(msg) &&
+			     (msg_destnode(msg) != tipc_own_addr)))
+			goto cont;
+		
 		n_ptr = tipc_node_find(msg_prevnode(msg));
 		if (unlikely(!n_ptr))
 			goto cont;