1 files changed, 90 insertions, 92 deletions

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index a5ede357cfbc..be1de4084196 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -630,21 +630,20 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 
 	/* if the sk is MP_CAPABLE, we try to fetch the client key */
 	if (subflow_req->mp_capable) {
-		if (TCP_SKB_CB(skb)->seq != subflow_req->ssn_offset + 1) {
-			/* here we can receive and accept an in-window,
-			 * out-of-order pkt, which will not carry the MP_CAPABLE
-			 * opt even on mptcp enabled paths
-			 */
-			goto create_msk;
-		}
-
+		/* we can receive and accept an in-window, out-of-order pkt,
+		 * which may not carry the MP_CAPABLE opt even on mptcp enabled
+		 * paths: always try to extract the peer key, and fallback
+		 * for packets missing it.
+		 * Even OoO DSS packets coming legitly after dropped or
+		 * reordered MPC will cause fallback, but we don't have other
+		 * options.
+		 */
 		mptcp_get_options(skb, &mp_opt);
 		if (!mp_opt.mp_capable) {
 			fallback = true;
 			goto create_child;
 		}
 
-create_msk:
 		new_msk = mptcp_sk_clone(listener->conn, &mp_opt, req);
 		if (!new_msk)
 			fallback = true;
@@ -785,10 +784,10 @@ static u64 expand_seq(u64 old_seq, u16 old_data_len, u64 seq)
 	return seq | ((old_seq + old_data_len + 1) & GENMASK_ULL(63, 32));
 }
 
-static void warn_bad_map(struct mptcp_subflow_context *subflow, u32 ssn)
+static void dbg_bad_map(struct mptcp_subflow_context *subflow, u32 ssn)
 {
-	WARN_ONCE(1, "Bad mapping: ssn=%d map_seq=%d map_data_len=%d",
-		  ssn, subflow->map_subflow_seq, subflow->map_data_len);
+	pr_debug("Bad mapping: ssn=%d map_seq=%d map_data_len=%d",
+		 ssn, subflow->map_subflow_seq, subflow->map_data_len);
 }
 
 static bool skb_is_fully_mapped(struct sock *ssk, struct sk_buff *skb)
@@ -813,13 +812,13 @@ static bool validate_mapping(struct sock *ssk, struct sk_buff *skb)
 		/* Mapping covers data later in the subflow stream,
 		 * currently unsupported.
 		 */
-		warn_bad_map(subflow, ssn);
+		dbg_bad_map(subflow, ssn);
 		return false;
 	}
 	if (unlikely(!before(ssn, subflow->map_subflow_seq +
 				  subflow->map_data_len))) {
 		/* Mapping does covers past subflow data, invalid */
-		warn_bad_map(subflow, ssn + skb->len);
+		dbg_bad_map(subflow, ssn);
 		return false;
 	}
 	return true;
@@ -867,7 +866,6 @@ static enum mapping_status get_mapping_status(struct sock *ssk,
 
 	data_len = mpext->data_len;
 	if (data_len == 0) {
-		pr_err("Infinite mapping not handled");
 		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_INFINITEMAPRX);
 		return MAPPING_INVALID;
 	}
@@ -1002,7 +1000,7 @@ static bool subflow_check_data_avail(struct sock *ssk)
 	struct sk_buff *skb;
 
 	if (!skb_peek(&ssk->sk_receive_queue))
-		subflow->data_avail = 0;
+		WRITE_ONCE(subflow->data_avail, 0);
 	if (subflow->data_avail)
 		return true;
 
@@ -1013,21 +1011,11 @@ static bool subflow_check_data_avail(struct sock *ssk)
 
 		status = get_mapping_status(ssk, msk);
 		trace_subflow_check_data_avail(status, skb_peek(&ssk->sk_receive_queue));
-		if (status == MAPPING_INVALID) {
-			ssk->sk_err = EBADMSG;
-			goto fatal;
-		}
-		if (status == MAPPING_DUMMY) {
-			__mptcp_do_fallback(msk);
-			skb = skb_peek(&ssk->sk_receive_queue);
-			subflow->map_valid = 1;
-			subflow->map_seq = READ_ONCE(msk->ack_seq);
-			subflow->map_data_len = skb->len;
-			subflow->map_subflow_seq = tcp_sk(ssk)->copied_seq -
-						   subflow->ssn_offset;
-			subflow->data_avail = MPTCP_SUBFLOW_DATA_AVAIL;
-			return true;
-		}
+		if (unlikely(status == MAPPING_INVALID))
+			goto fallback;
+
+		if (unlikely(status == MAPPING_DUMMY))
+			goto fallback;
 
 		if (status != MAPPING_OK)
 			goto no_data;
@@ -1040,10 +1028,8 @@ static bool subflow_check_data_avail(struct sock *ssk)
 		 * MP_CAPABLE-based mapping
 		 */
 		if (unlikely(!READ_ONCE(msk->can_ack))) {
-			if (!subflow->mpc_map) {
-				ssk->sk_err = EBADMSG;
-				goto fatal;
-			}
+			if (!subflow->mpc_map)
+				goto fallback;
 			WRITE_ONCE(msk->remote_key, subflow->remote_key);
 			WRITE_ONCE(msk->ack_seq, subflow->map_seq);
 			WRITE_ONCE(msk->can_ack, true);
@@ -1053,35 +1039,43 @@ static bool subflow_check_data_avail(struct sock *ssk)
 		ack_seq = mptcp_subflow_get_mapped_dsn(subflow);
 		pr_debug("msk ack_seq=%llx subflow ack_seq=%llx", old_ack,
 			 ack_seq);
-		if (ack_seq == old_ack) {
-			subflow->data_avail = MPTCP_SUBFLOW_DATA_AVAIL;
-			break;
-		} else if (after64(ack_seq, old_ack)) {
-			subflow->data_avail = MPTCP_SUBFLOW_OOO_DATA;
-			break;
+		if (unlikely(before64(ack_seq, old_ack))) {
+			mptcp_subflow_discard_data(ssk, skb, old_ack - ack_seq);
+			continue;
 		}
 
-		/* only accept in-sequence mapping. Old values are spurious
-		 * retransmission
-		 */
-		mptcp_subflow_discard_data(ssk, skb, old_ack - ack_seq);
+		WRITE_ONCE(subflow->data_avail, MPTCP_SUBFLOW_DATA_AVAIL);
+		break;
 	}
 	return true;
 
 no_data:
 	subflow_sched_work_if_closed(msk, ssk);
 	return false;
-fatal:
-	/* fatal protocol error, close the socket */
-	/* This barrier is coupled with smp_rmb() in tcp_poll() */
-	smp_wmb();
-	ssk->sk_error_report(ssk);
-	tcp_set_state(ssk, TCP_CLOSE);
-	subflow->reset_transient = 0;
-	subflow->reset_reason = MPTCP_RST_EMPTCP;
-	tcp_send_active_reset(ssk, GFP_ATOMIC);
-	subflow->data_avail = 0;
-	return false;
+
+fallback:
+	/* RFC 8684 section 3.7. */
+	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);
+	skb = skb_peek(&ssk->sk_receive_queue);
+	subflow->map_valid = 1;
+	subflow->map_seq = READ_ONCE(msk->ack_seq);
+	subflow->map_data_len = skb->len;
+	subflow->map_subflow_seq = tcp_sk(ssk)->copied_seq - subflow->ssn_offset;
+	WRITE_ONCE(subflow->data_avail, MPTCP_SUBFLOW_DATA_AVAIL);
+	return true;
 }
 
 bool mptcp_subflow_data_available(struct sock *sk)
@@ -1092,7 +1086,7 @@ bool mptcp_subflow_data_available(struct sock *sk)
 	if (subflow->map_valid &&
 	    mptcp_subflow_get_map_offset(subflow) >= subflow->map_data_len) {
 		subflow->map_valid = 0;
-		subflow->data_avail = 0;
+		WRITE_ONCE(subflow->data_avail, 0);
 
 		pr_debug("Done with mapping: seq=%u data_len=%u",
 			 subflow->map_subflow_seq,
@@ -1120,41 +1114,6 @@ void mptcp_space(const struct sock *ssk, int *space, int *full_space)
 	*full_space = tcp_full_space(sk);
 }
 
-static void subflow_data_ready(struct sock *sk)
-{
-	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
-	u16 state = 1 << inet_sk_state_load(sk);
-	struct sock *parent = subflow->conn;
-	struct mptcp_sock *msk;
-
-	msk = mptcp_sk(parent);
-	if (state & TCPF_LISTEN) {
-		/* MPJ subflow are removed from accept queue before reaching here,
-		 * avoid stray wakeups
-		 */
-		if (reqsk_queue_empty(&inet_csk(sk)->icsk_accept_queue))
-			return;
-
-		set_bit(MPTCP_DATA_READY, &msk->flags);
-		parent->sk_data_ready(parent);
-		return;
-	}
-
-	WARN_ON_ONCE(!__mptcp_check_fallback(msk) && !subflow->mp_capable &&
-		     !subflow->mp_join && !(state & TCPF_CLOSE));
-
-	if (mptcp_subflow_data_available(sk))
-		mptcp_data_ready(parent, sk);
-}
-
-static void subflow_write_space(struct sock *ssk)
-{
-	struct sock *sk = mptcp_subflow_ctx(ssk)->conn;
-
-	mptcp_propagate_sndbuf(sk, ssk);
-	mptcp_write_space(sk);
-}
-
 void __mptcp_error_report(struct sock *sk)
 {
 	struct mptcp_subflow_context *subflow;
@@ -1195,6 +1154,43 @@ static void subflow_error_report(struct sock *ssk)
 	mptcp_data_unlock(sk);
 }
 
+static void subflow_data_ready(struct sock *sk)
+{
+	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	u16 state = 1 << inet_sk_state_load(sk);
+	struct sock *parent = subflow->conn;
+	struct mptcp_sock *msk;
+
+	msk = mptcp_sk(parent);
+	if (state & TCPF_LISTEN) {
+		/* MPJ subflow are removed from accept queue before reaching here,
+		 * avoid stray wakeups
+		 */
+		if (reqsk_queue_empty(&inet_csk(sk)->icsk_accept_queue))
+			return;
+
+		set_bit(MPTCP_DATA_READY, &msk->flags);
+		parent->sk_data_ready(parent);
+		return;
+	}
+
+	WARN_ON_ONCE(!__mptcp_check_fallback(msk) && !subflow->mp_capable &&
+		     !subflow->mp_join && !(state & TCPF_CLOSE));
+
+	if (mptcp_subflow_data_available(sk))
+		mptcp_data_ready(parent, sk);
+	else if (unlikely(sk->sk_err))
+		subflow_error_report(sk);
+}
+
+static void subflow_write_space(struct sock *ssk)
+{
+	struct sock *sk = mptcp_subflow_ctx(ssk)->conn;
+
+	mptcp_propagate_sndbuf(sk, ssk);
+	mptcp_write_space(sk);
+}
+
 static struct inet_connection_sock_af_ops *
 subflow_default_af_ops(struct sock *sk)
 {
@@ -1505,6 +1501,8 @@ static void subflow_state_change(struct sock *sk)
 	 */
 	if (mptcp_subflow_data_available(sk))
 		mptcp_data_ready(parent, sk);
+	else if (unlikely(sk->sk_err))
+		subflow_error_report(sk);
 
 	subflow_sched_work_if_closed(mptcp_sk(parent), sk);