mptcp: Use MPTCP-level flag for sending DATA_FIN

Since DATA_FIN information is the same for every subflow, store it only
in the mptcp_sock.

Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/options.c

@@ -451,17 +451,22 @@ static bool mptcp_established_options_mp(struct sock *sk, struct sk_buff *skb,
 static void mptcp_write_data_fin(struct mptcp_subflow_context *subflow,
 				 struct sk_buff *skb, struct mptcp_ext *ext)
 {
+	u64 data_fin_tx_seq = READ_ONCE(mptcp_sk(subflow->conn)->write_seq);
+
 	if (!ext->use_map || !skb->len) {
 		/* RFC6824 requires a DSS mapping with specific values
 		 * if DATA_FIN is set but no data payload is mapped
 		 */
 		ext->data_fin = 1;
 		ext->use_map = 1;
 		ext->dsn64 = 1;
-		ext->data_seq = subflow->data_fin_tx_seq;
+		/* The write_seq value has already been incremented, so
+		 * the actual sequence number for the DATA_FIN is one less.
+		 */
+		ext->data_seq = data_fin_tx_seq - 1;
 		ext->subflow_seq = 0;
 		ext->data_len = 1;
-	} else if (ext->data_seq + ext->data_len == subflow->data_fin_tx_seq) {
+	} else if (ext->data_seq + ext->data_len == data_fin_tx_seq) {
 		/* If there's an existing DSS mapping and it is the
 		 * final mapping, DATA_FIN consumes 1 additional byte of
 		 * mapping space.
@@ -477,15 +482,17 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 					  struct mptcp_out_options *opts)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
+	struct mptcp_sock *msk = mptcp_sk(subflow->conn);
 	unsigned int dss_size = 0;
+	u64 snd_data_fin_enable;
 	struct mptcp_ext *mpext;
-	struct mptcp_sock *msk;
 	unsigned int ack_size;
 	bool ret = false;
 
 	mpext = skb ? mptcp_get_ext(skb) : NULL;
+	snd_data_fin_enable = READ_ONCE(msk->snd_data_fin_enable);
 
-	if (!skb || (mpext && mpext->use_map) || subflow->data_fin_tx_enable) {
+	if (!skb || (mpext && mpext->use_map) || snd_data_fin_enable) {
 		unsigned int map_size;
 
 		map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
@@ -495,7 +502,7 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 		if (mpext)
 			opts->ext_copy = *mpext;
 
-		if (skb && subflow->data_fin_tx_enable)
+		if (skb && snd_data_fin_enable)
 			mptcp_write_data_fin(subflow, skb, &opts->ext_copy);
 		ret = true;
 	}
@@ -504,7 +511,6 @@ static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
 	 * if the first subflow may have the already the remote key handy
 	 */
 	opts->ext_copy.use_ack = 0;
-	msk = mptcp_sk(subflow->conn);
 	if (!READ_ONCE(msk->can_ack)) {
 		*size = ALIGN(dss_size, 4);
 		return ret;

net/mptcp/protocol.c

@@ -1391,8 +1391,7 @@ static void mptcp_cancel_work(struct sock *sk)
 		sock_put(sk);
 }
 
-static void mptcp_subflow_shutdown(struct sock *ssk, int how,
-				   bool data_fin_tx_enable, u64 data_fin_tx_seq)
+static void mptcp_subflow_shutdown(struct sock *ssk, int how)
 {
 	lock_sock(ssk);
 
@@ -1405,14 +1404,6 @@ static void mptcp_subflow_shutdown(struct sock *ssk, int how,
 		tcp_disconnect(ssk, O_NONBLOCK);
 		break;
 	default:
-		if (data_fin_tx_enable) {
-			struct mptcp_subflow_context *subflow;
-
-			subflow = mptcp_subflow_ctx(ssk);
-			subflow->data_fin_tx_seq = data_fin_tx_seq;
-			subflow->data_fin_tx_enable = 1;
-		}
-
 		ssk->sk_shutdown |= how;
 		tcp_shutdown(ssk, how);
 		break;
@@ -1426,7 +1417,6 @@ static void mptcp_close(struct sock *sk, long timeout)
 	struct mptcp_subflow_context *subflow, *tmp;
 	struct mptcp_sock *msk = mptcp_sk(sk);
 	LIST_HEAD(conn_list);
-	u64 data_fin_tx_seq;
 
 	lock_sock(sk);
 
@@ -1440,17 +1430,14 @@ static void mptcp_close(struct sock *sk, long timeout)
 	spin_unlock_bh(&msk->join_list_lock);
 	list_splice_init(&msk->conn_list, &conn_list);
 
-	data_fin_tx_seq = msk->write_seq;
+	msk->snd_data_fin_enable = 1;
 
 	__mptcp_clear_xmit(sk);
 
 	release_sock(sk);
 
 	list_for_each_entry_safe(subflow, tmp, &conn_list, node) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
-
-		subflow->data_fin_tx_seq = data_fin_tx_seq;
-		subflow->data_fin_tx_enable = 1;
 		__mptcp_close_ssk(sk, ssk, subflow, timeout);
 	}
 
@@ -2146,10 +2133,12 @@ static int mptcp_shutdown(struct socket *sock, int how)
 	}
 
 	__mptcp_flush_join_list(msk);
+	msk->snd_data_fin_enable = 1;
+
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *tcp_sk = mptcp_subflow_tcp_sock(subflow);
 
-		mptcp_subflow_shutdown(tcp_sk, how, 1, msk->write_seq);
+		mptcp_subflow_shutdown(tcp_sk, how);
 	}
 
 	/* Wake up anyone sleeping in poll. */

net/mptcp/protocol.h

@@ -199,6 +199,7 @@ struct mptcp_sock {
 	unsigned long	flags;
 	bool		can_ack;
 	bool		fully_established;
+	bool		snd_data_fin_enable;
 	spinlock_t	join_list_lock;
 	struct work_struct work;
 	struct list_head conn_list;
@@ -291,10 +292,8 @@ struct mptcp_subflow_context {
 		backup : 1,
 		data_avail : 1,
 		rx_eof : 1,
-		data_fin_tx_enable : 1,
 		use_64bit_ack : 1, /* Set when we received a 64-bit DSN */
 		can_ack : 1;	    /* only after processing the remote a key */
-	u64	data_fin_tx_seq;
 	u32	remote_nonce;
 	u64	thmac;
 	u32	local_nonce;