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: Mat Martineau <mathew.j.martin...@linux.intel.com>
---
net/mptcp/options.c | 11 ++++++
net/mptcp/protocol.c | 87 +++++++++++++++++++++++++++++++++++++-------
net/mptcp/subflow.c | 11 ++++--
3 files changed, 92 insertions(+), 17 deletions(-)
diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 38583d1b9b5f..b4458ecd01f8 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -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;
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index b3350830e14d..f264ea15e081 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -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:
- ssk->sk_shutdown |= how;
- tcp_shutdown(ssk, how);
+ 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;
}
- __mptcp_flush_join_list(msk);
- msk->snd_data_fin_enable = 1;
+ /* 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_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);
+ }
+ } 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);
+
+ 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(sock->sk, tcp_sk, how);
+ }
}
/* Wake up anyone sleeping in poll. */
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index e645483d1200..7ab2a52ad150 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -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;
--
2.28.0
