Commit 43b54c6e authored by Mat Martineau's avatar Mat Martineau Committed by David S. Miller
Browse files

mptcp: Use full MPTCP-level disconnect state machine 



RFC 8684 appendix D describes the connection state machine for
MPTCP. This patch implements the DATA_FIN / DATA_ACK exchanges and
MPTCP-level socket state changes described in that appendix, rather than
simply sending DATA_FIN along with TCP FIN when disconnecting subflows.

DATA_FIN is now sent and acknowledged before shutting down the
subflows. Received DATA_FIN information (if not part of a data packet)
is written to the MPTCP socket when the incoming DSS option is parsed by
the subflow, and the MPTCP worker is scheduled to process the
flag. DATA_FIN received as part of a full DSS mapping will be handled
when the mapping is processed.

The DATA_FIN is acknowledged by the worker if the reader is caught
up. If there is still data to be moved to the MPTCP-level queue, ack_seq
will be incremented to account for the DATA_FIN when it reaches the end
of the stream and a DATA_ACK will be sent to the peer.

Signed-off-by: default avatarMat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 16a9a9da

net/mptcp/options.c

+11 −0
Original line number Diff line number Diff line
@@ -868,6 +868,17 @@ void mptcp_incoming_options(struct sock *sk, struct sk_buff *skb, 
	if (mp_opt.use_ack)

		update_una(msk, &mp_opt);



	/* Zero-length packets, like bare ACKs carrying a DATA_FIN, are

	 * dropped by the caller and not propagated to the MPTCP layer.

	 * Copy the DATA_FIN information now.

	 */

	if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {

		if (mp_opt.data_fin && mp_opt.data_len == 1 &&

		    mptcp_update_rcv_data_fin(msk, mp_opt.data_seq) &&

		    schedule_work(&msk->work))

			sock_hold(subflow->conn);

	}



	mpext = skb_ext_add(skb, SKB_EXT_MPTCP);

	if (!mpext)

		return;

net/mptcp/protocol.c

+73 −14
Original line number Diff line number Diff line
@@ -381,6 +381,15 @@ static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk, 


	*bytes = moved;



	/* If the moves have caught up with the DATA_FIN sequence number

	 * it's time to ack the DATA_FIN and change socket state, but

	 * this is not a good place to change state. Let the workqueue

	 * do it.

	 */

	if (mptcp_pending_data_fin(sk, NULL) &&

	    schedule_work(&msk->work))

		sock_hold(sk);



	return done;

}
@@ -466,7 +475,8 @@ void mptcp_data_acked(struct sock *sk) 
{

	mptcp_reset_timer(sk);



	if (!sk_stream_is_writeable(sk) &&

	if ((!sk_stream_is_writeable(sk) ||

	     (inet_sk_state_load(sk) != TCP_ESTABLISHED)) &&

	    schedule_work(&mptcp_sk(sk)->work))

		sock_hold(sk);

}
@@ -1384,6 +1394,7 @@ static void mptcp_worker(struct work_struct *work) 


	lock_sock(sk);

	mptcp_clean_una(sk);

	mptcp_check_data_fin_ack(sk);

	__mptcp_flush_join_list(msk);

	__mptcp_move_skbs(msk);
@@ -1393,6 +1404,8 @@ static void mptcp_worker(struct work_struct *work) 
	if (test_and_clear_bit(MPTCP_WORK_EOF, &msk->flags))

		mptcp_check_for_eof(msk);



	mptcp_check_data_fin(sk);



	if (!test_and_clear_bit(MPTCP_WORK_RTX, &msk->flags))

		goto unlock;
@@ -1515,7 +1528,7 @@ static void mptcp_cancel_work(struct sock *sk) 
		sock_put(sk);

}



static void mptcp_subflow_shutdown(struct sock *ssk, int how)

static void mptcp_subflow_shutdown(struct sock *sk, struct sock *ssk, int how)

{

	lock_sock(ssk);
@@ -1528,8 +1541,15 @@ static void mptcp_subflow_shutdown(struct sock *ssk, int how) 
		tcp_disconnect(ssk, O_NONBLOCK);

		break;

	default:

		if (__mptcp_check_fallback(mptcp_sk(sk))) {

			pr_debug("Fallback");

			ssk->sk_shutdown |= how;

			tcp_shutdown(ssk, how);

		} else {

			pr_debug("Sending DATA_FIN on subflow %p", ssk);

			mptcp_set_timeout(sk, ssk);

			tcp_send_ack(ssk);

		}

		break;

	}
@@ -1570,9 +1590,35 @@ static void mptcp_close(struct sock *sk, long timeout) 
	LIST_HEAD(conn_list);



	lock_sock(sk);

	sk->sk_shutdown = SHUTDOWN_MASK;



	if (sk->sk_state == TCP_LISTEN) {

		inet_sk_state_store(sk, TCP_CLOSE);

		goto cleanup;

	} else if (sk->sk_state == TCP_CLOSE) {

		goto cleanup;

	}



	if (__mptcp_check_fallback(msk)) {

		goto update_state;

	} else if (mptcp_close_state(sk)) {

		pr_debug("Sending DATA_FIN sk=%p", sk);

		WRITE_ONCE(msk->write_seq, msk->write_seq + 1);

		WRITE_ONCE(msk->snd_data_fin_enable, 1);



		mptcp_for_each_subflow(msk, subflow) {

			struct sock *tcp_sk = mptcp_subflow_tcp_sock(subflow);



			mptcp_subflow_shutdown(sk, tcp_sk, SHUTDOWN_MASK);

		}

	}



	sk_stream_wait_close(sk, timeout);



update_state:

	inet_sk_state_store(sk, TCP_CLOSE);



cleanup:

	/* be sure to always acquire the join list lock, to sync vs

	 * mptcp_finish_join().

	 */
@@ -1581,8 +1627,6 @@ static void mptcp_close(struct sock *sk, long timeout) 
	spin_unlock_bh(&msk->join_list_lock);

	list_splice_init(&msk->conn_list, &conn_list);



	msk->snd_data_fin_enable = 1;



	__mptcp_clear_xmit(sk);



	release_sock(sk);
@@ -2265,11 +2309,8 @@ static int mptcp_shutdown(struct socket *sock, int how) 
	pr_debug("sk=%p, how=%d", msk, how);



	lock_sock(sock->sk);

	if (how == SHUT_WR || how == SHUT_RDWR)

		inet_sk_state_store(sock->sk, TCP_FIN_WAIT1);



	how++;



	if ((how & ~SHUTDOWN_MASK) || !how) {

		ret = -EINVAL;

		goto out_unlock;
@@ -2283,13 +2324,31 @@ static int mptcp_shutdown(struct socket *sock, int how) 
			sock->state = SS_CONNECTED;

	}



	/* If we've already sent a FIN, or it's a closed state, skip this. */

	if (__mptcp_check_fallback(msk)) {

		if (how == SHUT_WR || how == SHUT_RDWR)

			inet_sk_state_store(sock->sk, TCP_FIN_WAIT1);



		mptcp_for_each_subflow(msk, subflow) {

			struct sock *tcp_sk = mptcp_subflow_tcp_sock(subflow);



			mptcp_subflow_shutdown(sock->sk, tcp_sk, how);

		}

	} else if ((how & SEND_SHUTDOWN) &&

		   ((1 << sock->sk->sk_state) &

		    (TCPF_ESTABLISHED | TCPF_SYN_SENT |

		     TCPF_SYN_RECV | TCPF_CLOSE_WAIT)) &&

		   mptcp_close_state(sock->sk)) {

		__mptcp_flush_join_list(msk);

	msk->snd_data_fin_enable = 1;



		WRITE_ONCE(msk->write_seq, msk->write_seq + 1);

		WRITE_ONCE(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);

			mptcp_subflow_shutdown(sock->sk, tcp_sk, how);

		}

	}



	/* Wake up anyone sleeping in poll. */

net/mptcp/subflow.c

+8 −3
Original line number Diff line number Diff line
@@ -598,7 +598,8 @@ static bool validate_mapping(struct sock *ssk, struct sk_buff *skb) 
	return true;

}



static enum mapping_status get_mapping_status(struct sock *ssk)

static enum mapping_status get_mapping_status(struct sock *ssk,

					      struct mptcp_sock *msk)

{

	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);

	struct mptcp_ext *mpext;
@@ -648,7 +649,8 @@ static enum mapping_status get_mapping_status(struct sock *ssk) 


	if (mpext->data_fin == 1) {

		if (data_len == 1) {

			pr_debug("DATA_FIN with no payload");

			mptcp_update_rcv_data_fin(msk, mpext->data_seq);

			pr_debug("DATA_FIN with no payload seq=%llu", mpext->data_seq);

			if (subflow->map_valid) {

				/* A DATA_FIN might arrive in a DSS

				 * option before the previous mapping
@@ -660,6 +662,9 @@ static enum mapping_status get_mapping_status(struct sock *ssk) 
			} else {

				return MAPPING_DATA_FIN;

			}

		} else {

			mptcp_update_rcv_data_fin(msk, mpext->data_seq + data_len);

			pr_debug("DATA_FIN with mapping seq=%llu", mpext->data_seq + data_len);

		}



		/* Adjust for DATA_FIN using 1 byte of sequence space */
@@ -748,7 +753,7 @@ static bool subflow_check_data_avail(struct sock *ssk) 
		u64 ack_seq;

		u64 old_ack;



		status = get_mapping_status(ssk);

		status = get_mapping_status(ssk, msk);

		pr_debug("msk=%p ssk=%p status=%d", msk, ssk, status);

		if (status == MAPPING_INVALID) {

			ssk->sk_err = EBADMSG;

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