This patch added a new struct member mp_fail_response_expect in struct
mptcp_subflow_context to support MP_FAIL response. In the single subflow
with checksum error and contiguous data special case, a MP_FAIL sent in
response to another MP_FAIL.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 net/mptcp/pm.c       | 10 +++++++++-
 net/mptcp/protocol.h |  1 +
 net/mptcp/subflow.c  |  2 ++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
index d0d31d5c198a..f5f4561f332a 100644
--- a/net/mptcp/pm.c
+++ b/net/mptcp/pm.c
@@ -279,8 +279,16 @@ void mptcp_pm_mp_fail_received(struct sock *sk, u64 fail_seq)
 
 	pr_debug("fail_seq=%llu", fail_seq);
 
-	if (!mptcp_has_another_subflow(sk) && READ_ONCE(msk->allow_infinite_fallback))
+	if (mptcp_has_another_subflow(sk) || !READ_ONCE(msk->allow_infinite_fallback))
+		return;
+
+	if (!READ_ONCE(subflow->mp_fail_response_expect)) {
+		pr_debug("send MP_FAIL response and infinite map");
+
+		subflow->send_mp_fail = 1;
+		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPFAILTX);
 		subflow->send_infinite_map = 1;
+	}
 }
 
 /* path manager helpers */
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index c8bada4537e2..83f0205f0d95 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -456,6 +456,7 @@ struct mptcp_subflow_context {
 		stale : 1,	    /* unable to snd/rcv data, do not use for xmit */
 		local_id_valid : 1; /* local_id is correctly initialized */
 	enum mptcp_data_avail data_avail;
+	bool	mp_fail_response_expect;
 	u32	remote_nonce;
 	u64	thmac;
 	u32	local_nonce;
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 30ffb00661bb..ca2352ad20d4 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -1217,6 +1217,8 @@ static bool subflow_check_data_avail(struct sock *ssk)
 				tcp_send_active_reset(ssk, GFP_ATOMIC);
 				while ((skb = skb_peek(&ssk->sk_receive_queue)))
 					sk_eat_skb(ssk, skb);
+			} else {
+				WRITE_ONCE(subflow->mp_fail_response_expect, true);
 			}
 			WRITE_ONCE(subflow->data_avail, MPTCP_SUBFLOW_NODATA);
 			return true;
-- 
2.34.1