[MPTCP] [PATCH mptcp-net] mptcp: fix DATA_FIN processing for orphaned sockets.

[MPTCP] [PATCH mptcp-net] mptcp: fix DATA_FIN processing for orphaned sockets.

[Paolo Abeni]

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Currently we move orphaned msk socket directly from FIN_WAIT2
state to close, with the rationale that incoming additional
data could be just dropped by the TCP stack/TW sockets.

Anyhow we miss sending MPTCP-level ack on incoming DATA_FIN,
and that may hang the peers.

Fixes: e16163b6e2b7 ("mptcp: refactor shutdown and close")
Signed-off-by: Paolo Abeni <pabeni(a)redhat.com>
---
I hope nobody is keeping track of nr of follow-ups x commit,
because the referenced one could score a world record :(((
---
 net/mptcp/protocol.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index ee5a2981df6da..f15c79ff6a53c 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2297,13 +2297,12 @@ static void mptcp_worker(struct work_struct *work)
 	__mptcp_check_send_data_fin(sk);
 	mptcp_check_data_fin(sk);
 
-	/* if the msk data is completely acked, or the socket timedout,
-	 * there is no point in keeping around an orphaned sk
+	/* There is no point in keeping aroud an orphaned sk timedout or closed,
+	 * but we need the msk around to reply to incoming DATA_FIN, even if
+	 * orphaned and in FIN_WAIT2 state
 	 */
 	if (sock_flag(sk, SOCK_DEAD) &&
-	    (mptcp_check_close_timeout(sk) ||
-	    (state != sk->sk_state &&
-	    ((1 << inet_sk_state_load(sk)) & (TCPF_CLOSE | TCPF_FIN_WAIT2))))) {
+	    (mptcp_check_close_timeout(sk) || sk->sk_state == TCP_CLOSE)) {
 		inet_sk_state_store(sk, TCP_CLOSE);
 		__mptcp_destroy_sock(sk);
 		goto unlock;
-- 
2.26.2