Bluetooth: Add a new L2CAP ERTM transmit state machine.

This implements a top-level transmit state machine with handlers for
the two ERTM states defined in the specification: XMIT and WAIT_F.

The state machine accepts an event and, optionally, a list of skbs to
transmit.  In addition to data transmission, the local busy state can
be modified, acks are processed, and monitor and retransmit timeouts
are handled.  This mirrors the structure of the state tables in the
spec.
Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

net/bluetooth/l2cap_core.c

@@ -73,6 +73,9 @@ static int l2cap_build_conf_req(struct l2cap_chan *chan, void *data);
 static void l2cap_send_disconn_req(struct l2cap_conn *conn,
 				   struct l2cap_chan *chan, int err);
 
+static int l2cap_tx(struct l2cap_chan *chan, struct l2cap_ctrl *control,
+		    struct sk_buff_head *skbs, u8 event);
+
 /* ---- L2CAP channels ---- */
 
 static struct l2cap_chan *__l2cap_get_chan_by_dcid(struct l2cap_conn *conn, u16 cid)
@@ -224,6 +227,19 @@ static inline void l2cap_chan_set_err(struct l2cap_chan *chan, int err)
 	release_sock(sk);
 }
 
+static struct sk_buff *l2cap_ertm_seq_in_queue(struct sk_buff_head *head,
+					       u16 seq)
+{
+	struct sk_buff *skb;
+
+	skb_queue_walk(head, skb) {
+		if (bt_cb(skb)->control.txseq == seq)
+			return skb;
+	}
+
+	return NULL;
+}
+
 /* ---- L2CAP sequence number lists ---- */
 
 /* For ERTM, ordered lists of sequence numbers must be tracked for
@@ -2120,16 +2136,15 @@ int l2cap_chan_send(struct l2cap_chan *chan, struct msghdr *msg, size_t len,
 		if (err)
 			break;
 
-		if (chan->mode == L2CAP_MODE_ERTM && chan->tx_send_head == NULL)
-			chan->tx_send_head = seg_queue.next;
-		skb_queue_splice_tail_init(&seg_queue, &chan->tx_q);
-
-		if (chan->mode == L2CAP_MODE_ERTM)
-			err = l2cap_ertm_send(chan);
-		else
+		if (chan->mode == L2CAP_MODE_ERTM) {
+			err = l2cap_tx(chan, 0, &seg_queue,
+				       L2CAP_EV_DATA_REQUEST);
+		} else {
+			skb_queue_splice_tail_init(&seg_queue, &chan->tx_q);
 			l2cap_streaming_send(chan);
+		}
 
-		if (err >= 0)
+		if (!err)
 			err = len;
 
 		/* If the skbs were not queued for sending, they'll still be in
@@ -2146,6 +2161,229 @@ int l2cap_chan_send(struct l2cap_chan *chan, struct msghdr *msg, size_t len,
 	return err;
 }
 
+static void l2cap_process_reqseq(struct l2cap_chan *chan, u16 reqseq)
+{
+	struct sk_buff *acked_skb;
+	u16 ackseq;
+
+	BT_DBG("chan %p, reqseq %d", chan, reqseq);
+
+	if (chan->unacked_frames == 0 || reqseq == chan->expected_ack_seq)
+		return;
+
+	BT_DBG("expected_ack_seq %d, unacked_frames %d",
+	       chan->expected_ack_seq, chan->unacked_frames);
+
+	for (ackseq = chan->expected_ack_seq; ackseq != reqseq;
+	     ackseq = __next_seq(chan, ackseq)) {
+
+		acked_skb = l2cap_ertm_seq_in_queue(&chan->tx_q, ackseq);
+		if (acked_skb) {
+			skb_unlink(acked_skb, &chan->tx_q);
+			kfree_skb(acked_skb);
+			chan->unacked_frames--;
+		}
+	}
+
+	chan->expected_ack_seq = reqseq;
+
+	if (chan->unacked_frames == 0)
+		__clear_retrans_timer(chan);
+
+	BT_DBG("unacked_frames %d", (int) chan->unacked_frames);
+}
+
+static void l2cap_abort_rx_srej_sent(struct l2cap_chan *chan)
+{
+	BT_DBG("chan %p", chan);
+
+	chan->expected_tx_seq = chan->buffer_seq;
+	l2cap_seq_list_clear(&chan->srej_list);
+	skb_queue_purge(&chan->srej_q);
+	chan->rx_state = L2CAP_RX_STATE_RECV;
+}
+
+static int l2cap_tx_state_xmit(struct l2cap_chan *chan,
+			       struct l2cap_ctrl *control,
+			       struct sk_buff_head *skbs, u8 event)
+{
+	int err = 0;
+
+	BT_DBG("chan %p, control %p, skbs %p, event %d", chan, control, skbs,
+	       event);
+
+	switch (event) {
+	case L2CAP_EV_DATA_REQUEST:
+		if (chan->tx_send_head == NULL)
+			chan->tx_send_head = skb_peek(skbs);
+
+		skb_queue_splice_tail_init(skbs, &chan->tx_q);
+		l2cap_ertm_send(chan);
+		break;
+	case L2CAP_EV_LOCAL_BUSY_DETECTED:
+		BT_DBG("Enter LOCAL_BUSY");
+		set_bit(CONN_LOCAL_BUSY, &chan->conn_state);
+
+		if (chan->rx_state == L2CAP_RX_STATE_SREJ_SENT) {
+			/* The SREJ_SENT state must be aborted if we are to
+			 * enter the LOCAL_BUSY state.
+			 */
+			l2cap_abort_rx_srej_sent(chan);
+		}
+
+		l2cap_send_ack(chan);
+
+		break;
+	case L2CAP_EV_LOCAL_BUSY_CLEAR:
+		BT_DBG("Exit LOCAL_BUSY");
+		clear_bit(CONN_LOCAL_BUSY, &chan->conn_state);
+
+		if (test_bit(CONN_RNR_SENT, &chan->conn_state)) {
+			struct l2cap_ctrl local_control;
+
+			memset(&local_control, 0, sizeof(local_control));
+			local_control.sframe = 1;
+			local_control.super = L2CAP_SUPER_RR;
+			local_control.poll = 1;
+			local_control.reqseq = chan->buffer_seq;
+			l2cap_send_sframe(chan, 0);
+
+			chan->retry_count = 1;
+			__set_monitor_timer(chan);
+			chan->tx_state = L2CAP_TX_STATE_WAIT_F;
+		}
+		break;
+	case L2CAP_EV_RECV_REQSEQ_AND_FBIT:
+		l2cap_process_reqseq(chan, control->reqseq);
+		break;
+	case L2CAP_EV_EXPLICIT_POLL:
+		l2cap_send_rr_or_rnr(chan, 1);
+		chan->retry_count = 1;
+		__set_monitor_timer(chan);
+		__clear_ack_timer(chan);
+		chan->tx_state = L2CAP_TX_STATE_WAIT_F;
+		break;
+	case L2CAP_EV_RETRANS_TO:
+		l2cap_send_rr_or_rnr(chan, 1);
+		chan->retry_count = 1;
+		__set_monitor_timer(chan);
+		chan->tx_state = L2CAP_TX_STATE_WAIT_F;
+		break;
+	case L2CAP_EV_RECV_FBIT:
+		/* Nothing to process */
+		break;
+	default:
+		break;
+	}
+
+	return err;
+}
+
+static int l2cap_tx_state_wait_f(struct l2cap_chan *chan,
+				 struct l2cap_ctrl *control,
+				 struct sk_buff_head *skbs, u8 event)
+{
+	int err = 0;
+
+	BT_DBG("chan %p, control %p, skbs %p, event %d", chan, control, skbs,
+	       event);
+
+	switch (event) {
+	case L2CAP_EV_DATA_REQUEST:
+		if (chan->tx_send_head == NULL)
+			chan->tx_send_head = skb_peek(skbs);
+		/* Queue data, but don't send. */
+		skb_queue_splice_tail_init(skbs, &chan->tx_q);
+		break;
+	case L2CAP_EV_LOCAL_BUSY_DETECTED:
+		BT_DBG("Enter LOCAL_BUSY");
+		set_bit(CONN_LOCAL_BUSY, &chan->conn_state);
+
+		if (chan->rx_state == L2CAP_RX_STATE_SREJ_SENT) {
+			/* The SREJ_SENT state must be aborted if we are to
+			 * enter the LOCAL_BUSY state.
+			 */
+			l2cap_abort_rx_srej_sent(chan);
+		}
+
+		l2cap_send_ack(chan);
+
+		break;
+	case L2CAP_EV_LOCAL_BUSY_CLEAR:
+		BT_DBG("Exit LOCAL_BUSY");
+		clear_bit(CONN_LOCAL_BUSY, &chan->conn_state);
+
+		if (test_bit(CONN_RNR_SENT, &chan->conn_state)) {
+			struct l2cap_ctrl local_control;
+			memset(&local_control, 0, sizeof(local_control));
+			local_control.sframe = 1;
+			local_control.super = L2CAP_SUPER_RR;
+			local_control.poll = 1;
+			local_control.reqseq = chan->buffer_seq;
+			l2cap_send_sframe(chan, 0);
+
+			chan->retry_count = 1;
+			__set_monitor_timer(chan);
+			chan->tx_state = L2CAP_TX_STATE_WAIT_F;
+		}
+		break;
+	case L2CAP_EV_RECV_REQSEQ_AND_FBIT:
+		l2cap_process_reqseq(chan, control->reqseq);
+
+		/* Fall through */
+
+	case L2CAP_EV_RECV_FBIT:
+		if (control && control->final) {
+			__clear_monitor_timer(chan);
+			if (chan->unacked_frames > 0)
+				__set_retrans_timer(chan);
+			chan->retry_count = 0;
+			chan->tx_state = L2CAP_TX_STATE_XMIT;
+			BT_DBG("recv fbit tx_state 0x2.2%x", chan->tx_state);
+		}
+		break;
+	case L2CAP_EV_EXPLICIT_POLL:
+		/* Ignore */
+		break;
+	case L2CAP_EV_MONITOR_TO:
+		if (chan->max_tx == 0 || chan->retry_count < chan->max_tx) {
+			l2cap_send_rr_or_rnr(chan, 1);
+			__set_monitor_timer(chan);
+			chan->retry_count++;
+		} else {
+			l2cap_send_disconn_req(chan->conn, chan, ECONNABORTED);
+		}
+		break;
+	default:
+		break;
+	}
+
+	return err;
+}
+
+static int l2cap_tx(struct l2cap_chan *chan, struct l2cap_ctrl *control,
+		    struct sk_buff_head *skbs, u8 event)
+{
+	int err = 0;
+
+	BT_DBG("chan %p, control %p, skbs %p, event %d, state %d",
+	       chan, control, skbs, event, chan->tx_state);
+
+	switch (chan->tx_state) {
+	case L2CAP_TX_STATE_XMIT:
+		err = l2cap_tx_state_xmit(chan, control, skbs, event);
+		break;
+	case L2CAP_TX_STATE_WAIT_F:
+		err = l2cap_tx_state_wait_f(chan, control, skbs, event);
+		break;
+	default:
+		/* Ignore event */
+		break;
+	}
+
+	return err;
+}
+
 /* Copy frame to all raw sockets on that connection */
 static void l2cap_raw_recv(struct l2cap_conn *conn, struct sk_buff *skb)
 {