mptcp: don't orphan ssk in mptcp_close()

All of the subflows of a msk will be orphaned in mptcp_close(), which
means the subflows are in DEAD state. After then, DATA_FIN will be sent,
and the other side will response with a DATA_ACK for this DATA_FIN.

However, if the other side still has pending data, the data that received
on these subflows will not be passed to the msk, as they are DEAD and
subflow_data_ready() will not be called in tcp_data_ready(). Therefore,
these data can't be acked, and they will be retransmitted again and again,
until timeout.

Fix this by setting ssk->sk_socket and ssk->sk_wq to 'NULL', instead of
orphaning the subflows in __mptcp_close(), as Paolo suggested.

Fixes: e16163b6e2b7 ("mptcp: refactor shutdown and close")
Reviewed-by: Biao Jiang <benbjiang@tencent.com>
Reviewed-by: Mengen Sun <mengensun@tencent.com>
Signed-off-by: Menglong Dong <imagedong@tencent.com>
Reviewed-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index b6dc6e2..1dbc625 100644 (file)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2354,12 +2354,7 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
                goto out;
        }
 
-       /* if we are invoked by the msk cleanup code, the subflow is
-        * already orphaned
-        */
-       if (ssk->sk_socket)
-               sock_orphan(ssk);
-
+       sock_orphan(ssk);
        subflow->disposable = 1;
 
        /* if ssk hit tcp_done(), tcp_cleanup_ulp() cleared the related ops
@@ -2940,7 +2935,11 @@ cleanup:
                if (ssk == msk->first)
                        subflow->fail_tout = 0;
 
-               sock_orphan(ssk);
+               /* detach from the parent socket, but allow data_ready to
+                * push incoming data into the mptcp stack, to properly ack it
+                */
+               ssk->sk_socket = NULL;
+               ssk->sk_wq = NULL;
                unlock_sock_fast(ssk, slow);
        }
        sock_orphan(sk);