[PATCH 5.11 123/306] mptcp: reset last_snd on subflow close

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

From: Florian Westphal <fw@strlen.de>

[ Upstream commit e0be4931f3fee2e04dec4013ea4f27ec2db8556f ]

Send logic caches last active subflow in the msk, so it needs to be
cleared when the cached subflow is closed.

Fixes: d5f49190def61c ("mptcp: allow picking different xmit subflows")
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/155
Reported-by: Christoph Paasch <redacted>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts <redacted>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Mat Martineau <redacted>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/mptcp/protocol.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 3cc7be259396..de89824a2a36 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c

@@ -2110,6 +2110,8 @@ static struct sock *mptcp_subflow_get_retrans(const struct mptcp_sock *msk)
 void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
 		       struct mptcp_subflow_context *subflow)
 {
+	struct mptcp_sock *msk = mptcp_sk(sk);
+
 	list_del(&subflow->node);
 
 	lock_sock_nested(ssk, SINGLE_DEPTH_NESTING);

@@ -2138,6 +2140,9 @@ void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
 	release_sock(ssk);
 
 	sock_put(ssk);
+
+	if (ssk == msk->last_snd)
+		msk->last_snd = NULL;
 }
 
 static unsigned int mptcp_sync_mss(struct sock *sk, u32 pmtu)

-- 
2.30.1