rxrpc: Fix loss of final ack on shutdown

Fix the loss of transmission of a call's final ack when a socket gets shut
down.  This means that the server will retransmit the last data packet or
send a ping ack and then get an ICMP indicating the port got closed.  The
server will then view this as a failure.

Fixes: 3136ef49 ("rxrpc: Delay terminal ACK transmission on a client call")
Signed-off-by: David Howells <dhowells@redhat.com>

net/rxrpc/ar-internal.h

@@ -831,6 +831,7 @@ void rxrpc_clean_up_local_conns(struct rxrpc_local *);
  * conn_event.c
  */
 void rxrpc_process_connection(struct work_struct *);
+void rxrpc_process_delayed_final_acks(struct rxrpc_connection *, bool);
 
 /*
  * conn_object.c

net/rxrpc/conn_client.c

@@ -906,6 +906,9 @@ static void rxrpc_unbundle_conn(struct rxrpc_connection *conn)
 
 	_enter("C=%x", conn->debug_id);
 
+	if (conn->flags & RXRPC_CONN_FINAL_ACK_MASK)
+		rxrpc_process_delayed_final_acks(conn, true);
+
 	spin_lock(&bundle->channel_lock);
 	bindex = conn->bundle_shift / RXRPC_MAXCALLS;
 	if (bundle->conns[bindex] == conn) {

net/rxrpc/conn_event.c

@@ -397,7 +397,7 @@ static void rxrpc_secure_connection(struct rxrpc_connection *conn)
 /*
  * Process delayed final ACKs that we haven't subsumed into a subsequent call.
  */
-static void rxrpc_process_delayed_final_acks(struct rxrpc_connection *conn)
+void rxrpc_process_delayed_final_acks(struct rxrpc_connection *conn, bool force)
 {
 	unsigned long j = jiffies, next_j;
 	unsigned int channel;
@@ -416,7 +416,7 @@ static void rxrpc_process_delayed_final_acks(struct rxrpc_connection *conn)
 		smp_rmb(); /* vs rxrpc_disconnect_client_call */
 		ack_at = READ_ONCE(chan->final_ack_at);
 
-		if (time_before(j, ack_at)) {
+		if (time_before(j, ack_at) && !force) {
 			if (time_before(ack_at, next_j)) {
 				next_j = ack_at;
 				set = true;
@@ -450,7 +450,7 @@ static void rxrpc_do_process_connection(struct rxrpc_connection *conn)
 
 	/* Process delayed ACKs whose time has come. */
 	if (conn->flags & RXRPC_CONN_FINAL_ACK_MASK)
-		rxrpc_process_delayed_final_acks(conn);
+		rxrpc_process_delayed_final_acks(conn, false);
 
 	/* go through the conn-level event packets, releasing the ref on this
 	 * connection that each one has when we've finished with it */