tipc: fix link acknowledge logic in receive path

Link state acks triggered from the receive path is done before
the last received packet have been processed by the link layer.
The effect of this is that the last received packet will not be
included in the ack. This causes problems if the link window is
set to TIPC_MIN_LINK_WIN, where the ack interval will be equal to
the link tolerance, and the link enters a stop-and-go behavior.
We move the ack logic to after link state processing, just before
the packet is delivered to higher layers.

Signed-off-by: Erik Hugne <erik.hugne@ericsson.com>
Signed-off-by: Carl Sigurjonsson <carl.sigurjonsson@ericsson.com>
Reviewed-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/link.c

@@ -1422,11 +1422,6 @@ void tipc_rcv(struct sk_buff *head, struct tipc_bearer *b_ptr)
 		if (unlikely(!list_empty(&l_ptr->waiting_ports)))
 			tipc_link_wakeup_ports(l_ptr, 0);
 
-		if (unlikely(++l_ptr->unacked_window >= TIPC_MIN_LINK_WIN)) {
-			l_ptr->stats.sent_acks++;
-			tipc_link_proto_xmit(l_ptr, STATE_MSG, 0, 0, 0, 0, 0);
-		}
-
 		/* Process the incoming packet */
 		if (unlikely(!link_working_working(l_ptr))) {
 			if (msg_user(msg) == LINK_PROTOCOL) {
@@ -1460,6 +1455,11 @@ void tipc_rcv(struct sk_buff *head, struct tipc_bearer *b_ptr)
 		if (unlikely(l_ptr->oldest_deferred_in))
 			head = link_insert_deferred_queue(l_ptr, head);
 
+		if (unlikely(++l_ptr->unacked_window >= TIPC_MIN_LINK_WIN)) {
+			l_ptr->stats.sent_acks++;
+			tipc_link_proto_xmit(l_ptr, STATE_MSG, 0, 0, 0, 0, 0);
+		}
+
 		if (tipc_link_prepare_input(l_ptr, &buf)) {
 			tipc_node_unlock(n_ptr);
 			continue;