5 files changed, 14 insertions, 3 deletions
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 1cf73e6f85ca..3dc964010fef 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -148,9 +148,7 @@ struct tcp_request_sock {
 	const struct tcp_request_sock_ops *af_specific;
 	u64				snt_synack; /* first SYNACK sent time */
 	bool				tfo_listener;
-#if IS_ENABLED(CONFIG_MPTCP)
 	bool				is_mptcp;
-#endif
 	u32				txhash;
 	u32				rcv_isn;
 	u32				snt_isn;
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 345b2b0ff618..9a4f6b16c9bc 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -349,6 +349,10 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	req->ts_recent		= tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
 	treq->snt_synack	= 0;
 	treq->tfo_listener	= false;
+
+	if (IS_ENABLED(CONFIG_MPTCP))
+		treq->is_mptcp = 0;
+
 	if (IS_ENABLED(CONFIG_SMC))
 		ireq->smc_ok = 0;
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index e8b840a4767e..e325b4506e25 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6637,6 +6637,9 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 
 	af_ops->init_req(req, sk, skb);
 
+	if (IS_ENABLED(CONFIG_MPTCP) && want_cookie)
+		tcp_rsk(req)->is_mptcp = 0;
+
 	if (security_inet_conn_request(sk, skb, req))
 		goto drop_and_free;
 
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 30915f6f31e3..13235a012388 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -178,6 +178,9 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	treq = tcp_rsk(req);
 	treq->tfo_listener = false;
 
+	if (IS_ENABLED(CONFIG_MPTCP))
+		treq->is_mptcp = 0;
+
 	if (security_inet_conn_request(sk, skb, req))
 		goto out_free;
 
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 205dca1c30b7..c90c0e6ffb82 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -186,6 +186,9 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 
 	pr_debug("listener=%p, req=%p, conn=%p", listener, req, listener->conn);
 
+	if (tcp_rsk(req)->is_mptcp == 0)
+		goto create_child;
+
 	/* if the sk is MP_CAPABLE, we try to fetch the client key */
 	subflow_req = mptcp_subflow_rsk(req);
 	if (subflow_req->mp_capable) {
@@ -769,7 +772,7 @@ static void subflow_ulp_clone(const struct request_sock *req,
 	struct mptcp_subflow_context *old_ctx = mptcp_subflow_ctx(newsk);
 	struct mptcp_subflow_context *new_ctx;
 
-	if (!subflow_req->mp_capable) {
+	if (!tcp_rsk(req)->is_mptcp || !subflow_req->mp_capable) {
 		subflow_ulp_fallback(newsk, old_ctx);
 		return;
 	}