[PATCH mptcp-next v4 4/8] mptcp: add the fallback check

[Geliang Tang <geliangtang@gmail.com>]

This patch added the fallback check in subflow_check_data_avail. Only do
the fallback when the msk isn't fallen back yet.

Signed-off-by: Geliang Tang <geliangtang@gmail.com>
---
 net/mptcp/subflow.c | 46 +++++++++++++++++++++++----------------------
 1 file changed, 24 insertions(+), 22 deletions(-)

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index b07803ed3053..89173f70707e 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -1164,35 +1164,37 @@ static bool subflow_check_data_avail(struct sock *ssk)
 	return false;
 
 fallback:
-	/* RFC 8684 section 3.7. */
-	if (subflow->send_mp_fail) {
-		if (mptcp_has_another_subflow(ssk) || !mptcp_is_data_contiguous(msk)) {
+	if (!__mptcp_check_fallback(msk)) {
+		/* RFC 8684 section 3.7. */
+		if (subflow->send_mp_fail) {
+			if (mptcp_has_another_subflow(ssk) || !mptcp_is_data_contiguous(msk)) {
+				ssk->sk_err = EBADMSG;
+				tcp_set_state(ssk, TCP_CLOSE);
+				subflow->reset_transient = 0;
+				subflow->reset_reason = MPTCP_RST_EMIDDLEBOX;
+				tcp_send_active_reset(ssk, GFP_ATOMIC);
+				while ((skb = skb_peek(&ssk->sk_receive_queue)))
+					sk_eat_skb(ssk, skb);
+			}
+			WRITE_ONCE(subflow->data_avail, 0);
+			return true;
+		}
+
+		if (subflow->mp_join || subflow->fully_established) {
+			/* fatal protocol error, close the socket.
+			 * subflow_error_report() will introduce the appropriate barriers
+			 */
 			ssk->sk_err = EBADMSG;
 			tcp_set_state(ssk, TCP_CLOSE);
 			subflow->reset_transient = 0;
-			subflow->reset_reason = MPTCP_RST_EMIDDLEBOX;
+			subflow->reset_reason = MPTCP_RST_EMPTCP;
 			tcp_send_active_reset(ssk, GFP_ATOMIC);
-			while ((skb = skb_peek(&ssk->sk_receive_queue)))
-				sk_eat_skb(ssk, skb);
+			WRITE_ONCE(subflow->data_avail, 0);
+			return false;
 		}
-		WRITE_ONCE(subflow->data_avail, 0);
-		return true;
-	}
 
-	if (subflow->mp_join || subflow->fully_established) {
-		/* fatal protocol error, close the socket.
-		 * subflow_error_report() will introduce the appropriate barriers
-		 */
-		ssk->sk_err = EBADMSG;
-		tcp_set_state(ssk, TCP_CLOSE);
-		subflow->reset_transient = 0;
-		subflow->reset_reason = MPTCP_RST_EMPTCP;
-		tcp_send_active_reset(ssk, GFP_ATOMIC);
-		WRITE_ONCE(subflow->data_avail, 0);
-		return false;
+		__mptcp_do_fallback(msk);
 	}
-
-	__mptcp_do_fallback(msk);
 	skb = skb_peek(&ssk->sk_receive_queue);
 	subflow->map_valid = 1;
 	subflow->map_seq = READ_ONCE(msk->ack_seq);
-- 
2.31.1