Re: [PATCH net 2/2] mptcp: better msk-level shutdown.

Instead of re-implementing most of inet_shutdown, re-use
such helper, and implement the MPTCP-specific bits at the
'proto' level.

The msk-level disconnect() can now be invoked, lets provide a
suitable implementation.

As a side effect, this fixes bad state management for listener
sockets. The latter could lead to division by 0 oops since
commit ea4ca586b16f ("mptcp: refine MPTCP-level ack scheduling").

Fixes: 43b54c6ee382 ("mptcp: Use full MPTCP-level disconnect state machine")
Fixes: ea4ca586b16f ("mptcp: refine MPTCP-level ack scheduling")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 net/mptcp/protocol.c | 62 ++++++++++++--------------------------------
 1 file changed, 17 insertions(+), 45 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 2ff8c7caf74f..81faeff8f3bb 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c

@@ -2642,11 +2642,12 @@ static void mptcp_copy_inaddrs(struct sock *msk, const struct sock *ssk)
 
 static int mptcp_disconnect(struct sock *sk, int flags)
 {
-	/* Should never be called.
-	 * inet_stream_connect() calls ->disconnect, but that
-	 * refers to the subflow socket, not the mptcp one.
-	 */
-	WARN_ON_ONCE(1);
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
+	__mptcp_flush_join_list(msk);
+	mptcp_for_each_subflow(msk, subflow)
+		tcp_disconnect(mptcp_subflow_tcp_sock(subflow), flags);