Merge branch 'tcp-mptcp-close-wait'

Jason Xing says:

====================
tcp/mptcp: count CLOSE-WAIT for CurrEstab

Taking CLOSE-WAIT sockets into CurrEstab counters is in accordance with RFC
1213, as suggested by Eric and Neal.

v5
Link: https://lore.kernel.org/all/20240531091753.75930-1-kerneljasonxing@gmail.com/
1. add more detailed comment (Matthieu)

v4
Link: https://lore.kernel.org/all/20240530131308.59737-1-kerneljasonxing@gmail.com/
1. correct the Fixes: tag in patch [2/2]. (Eric)

Previous discussion
Link: https://lore.kernel.org/all/20240529033104.33882-1-kerneljasonxing@gmail.com/
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp.c

@@ -2649,6 +2649,10 @@ void tcp_set_state(struct sock *sk, int state)
 		if (oldstate != TCP_ESTABLISHED)
 			TCP_INC_STATS(sock_net(sk), TCP_MIB_CURRESTAB);
 		break;
+	case TCP_CLOSE_WAIT:
+		if (oldstate == TCP_SYN_RECV)
+			TCP_INC_STATS(sock_net(sk), TCP_MIB_CURRESTAB);
+		break;
 
 	case TCP_CLOSE:
 		if (oldstate == TCP_CLOSE_WAIT || oldstate == TCP_ESTABLISHED)
@@ -2660,7 +2664,7 @@ void tcp_set_state(struct sock *sk, int state)
 			inet_put_port(sk);
 		fallthrough;
 	default:
-		if (oldstate == TCP_ESTABLISHED)
+		if (oldstate == TCP_ESTABLISHED || oldstate == TCP_CLOSE_WAIT)
 			TCP_DEC_STATS(sock_net(sk), TCP_MIB_CURRESTAB);
 	}
 

net/mptcp/protocol.c

@@ -2916,9 +2916,14 @@ void mptcp_set_state(struct sock *sk, int state)
 		if (oldstate != TCP_ESTABLISHED)
 			MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_CURRESTAB);
 		break;
-
+	case TCP_CLOSE_WAIT:
+		/* Unlike TCP, MPTCP sk would not have the TCP_SYN_RECV state:
+		 * MPTCP "accepted" sockets will be created later on. So no
+		 * transition from TCP_SYN_RECV to TCP_CLOSE_WAIT.
+		 */
+		break;
 	default:
-		if (oldstate == TCP_ESTABLISHED)
+		if (oldstate == TCP_ESTABLISHED || oldstate == TCP_CLOSE_WAIT)
 			MPTCP_DEC_STATS(sock_net(sk), MPTCP_MIB_CURRESTAB);
 	}