Patch "tcp: count CLOSE-WAIT sockets for TCP_MIB_CURRESTAB" has been added to the 6.9-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    tcp: count CLOSE-WAIT sockets for TCP_MIB_CURRESTAB

to the 6.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tcp-count-close-wait-sockets-for-tcp_mib_currestab.patch
and it can be found in the queue-6.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 3cc0e03cbc4e4bebe9c627aacac1a24192290b13
Author: Jason Xing <kernelxing@xxxxxxxxxxx>
Date:   Tue Jun 4 01:02:16 2024 +0800

    tcp: count CLOSE-WAIT sockets for TCP_MIB_CURRESTAB
    
    [ Upstream commit a46d0ea5c94205f40ecf912d1bb7806a8a64704f ]
    
    According to RFC 1213, we should also take CLOSE-WAIT sockets into
    consideration:
    
      "tcpCurrEstab OBJECT-TYPE
       ...
       The number of TCP connections for which the current state
       is either ESTABLISHED or CLOSE- WAIT."
    
    After this, CurrEstab counter will display the total number of
    ESTABLISHED and CLOSE-WAIT sockets.
    
    The logic of counting
    When we increment the counter?
    a) if we change the state to ESTABLISHED.
    b) if we change the state from SYN-RECEIVED to CLOSE-WAIT.
    
    When we decrement the counter?
    a) if the socket leaves ESTABLISHED and will never go into CLOSE-WAIT,
    say, on the client side, changing from ESTABLISHED to FIN-WAIT-1.
    b) if the socket leaves CLOSE-WAIT, say, on the server side, changing
    from CLOSE-WAIT to LAST-ACK.
    
    Please note: there are two chances that old state of socket can be changed
    to CLOSE-WAIT in tcp_fin(). One is SYN-RECV, the other is ESTABLISHED.
    So we have to take care of the former case.
    
    Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
    Signed-off-by: Jason Xing <kernelxing@xxxxxxxxxxx>
    Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 5c79836e4c9e7..77ee1eda3fd86 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2640,6 +2640,10 @@ 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)
@@ -2651,7 +2655,7 @@ 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);
 	}