tipc: Enhance filtering of out-dated link reset messages

Ensure TIPC ignores an out-dated link reset message whose session
number predates the current session number. (Previously, TIPC only
ignored an out-date reset message whose session number was equal
to the current link session number.)

Out-dated link reset messages should not occur under normal circumstances;
however, they can be generated if a link endpoint is unable to send a
link reset message right away and queues it for later delivery, but the
queued message is not sent until after the link is established.

Thanks to Laser [gotolaser@gmail.com] for diagnosing the problem and
contributing a prototype patch.

Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

net/tipc/link.c

@@ -2045,8 +2045,8 @@ static void link_recv_proto_msg(struct link *l_ptr, struct sk_buff *buf)
 	case RESET_MSG:
 		if (!link_working_unknown(l_ptr) &&
 		    (l_ptr->peer_session != INVALID_SESSION)) {
-			if (msg_session(msg) == l_ptr->peer_session)
-				break; /* duplicate: ignore */
+			if (less_eq(msg_session(msg), l_ptr->peer_session))
+				break; /* duplicate or old reset: ignore */
 		}
 		/* fall thru' */
 	case ACTIVATE_MSG: