Bluetooth: Refactor l2cap_ertm_send

The new implementation is aware of the new transmit state machine, and
uses struct l2cap_ctrl to compose ERTM headers.  It also has improved
error handling for allocation failures, and does not send the packet
until after all skb and channel data structures are updated.
Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

net/bluetooth/l2cap_core.c

@@ -1741,9 +1741,10 @@ static void l2cap_retransmit_one_frame(struct l2cap_chan *chan, u16 tx_seq)
 static int l2cap_ertm_send(struct l2cap_chan *chan)
 {
 	struct sk_buff *skb, *tx_skb;
-	u16 fcs;
-	u32 control;
-	int nsent = 0;
+	struct l2cap_ctrl *control;
+	int sent = 0;
+
+	BT_DBG("chan %p", chan);
 
 	if (chan->state != BT_CONNECTED)
 		return -ENOTCONN;
@@ -1751,61 +1752,57 @@ static int l2cap_ertm_send(struct l2cap_chan *chan)
 	if (test_bit(CONN_REMOTE_BUSY, &chan->conn_state))
 		return 0;
 
-	while ((skb = chan->tx_send_head) && (!l2cap_tx_window_full(chan))) {
-
-		if (bt_cb(skb)->control.retries == chan->remote_max_tx &&
-		    chan->remote_max_tx) {
-			l2cap_send_disconn_req(chan->conn, chan, ECONNABORTED);
-			break;
-		}
-
-		tx_skb = skb_clone(skb, GFP_ATOMIC);
+	while (chan->tx_send_head &&
+	       chan->unacked_frames < chan->remote_tx_win &&
+	       chan->tx_state == L2CAP_TX_STATE_XMIT) {
 
-		bt_cb(skb)->control.retries++;
+		skb = chan->tx_send_head;
 
-		control = __get_control(chan, tx_skb->data + L2CAP_HDR_SIZE);
-		control &= __get_sar_mask(chan);
+		bt_cb(skb)->control.retries = 1;
+		control = &bt_cb(skb)->control;
 
 		if (test_and_clear_bit(CONN_SEND_FBIT, &chan->conn_state))
-			control |= __set_ctrl_final(chan);
+			control->final = 1;
 
-		control |= __set_reqseq(chan, chan->buffer_seq);
-		control |= __set_txseq(chan, chan->next_tx_seq);
-		control |= __set_ctrl_sar(chan, bt_cb(skb)->control.sar);
+		control->reqseq = chan->buffer_seq;
+		chan->last_acked_seq = chan->buffer_seq;
+		control->txseq = chan->next_tx_seq;
 
-		__put_control(chan, control, tx_skb->data + L2CAP_HDR_SIZE);
+		__pack_control(chan, control, skb);
 
 		if (chan->fcs == L2CAP_FCS_CRC16) {
-			fcs = crc16(0, (u8 *)skb->data,
-						tx_skb->len - L2CAP_FCS_SIZE);
-			put_unaligned_le16(fcs, skb->data +
-						tx_skb->len - L2CAP_FCS_SIZE);
+			u16 fcs = crc16(0, (u8 *) skb->data, skb->len);
+			put_unaligned_le16(fcs, skb_put(skb, L2CAP_FCS_SIZE));
 		}
 
-		l2cap_do_send(chan, tx_skb);
+		/* Clone after data has been modified. Data is assumed to be
+		   read-only (for locking purposes) on cloned sk_buffs.
+		 */
+		tx_skb = skb_clone(skb, GFP_KERNEL);
 
-		__set_retrans_timer(chan);
+		if (!tx_skb)
+			break;
 
-		bt_cb(skb)->control.txseq = chan->next_tx_seq;
+		__set_retrans_timer(chan);
 
 		chan->next_tx_seq = __next_seq(chan, chan->next_tx_seq);
-
-		if (bt_cb(skb)->control.retries == 1) {
 		chan->unacked_frames++;
-
-			if (!nsent++)
-				__clear_ack_timer(chan);
-		}
-
 		chan->frames_sent++;
+		sent++;
 
 		if (skb_queue_is_last(&chan->tx_q, skb))
 			chan->tx_send_head = NULL;
 		else
 			chan->tx_send_head = skb_queue_next(&chan->tx_q, skb);
+
+		l2cap_do_send(chan, tx_skb);
+		BT_DBG("Sent txseq %d", (int)control->txseq);
 	}
 
-	return nsent;
+	BT_DBG("Sent %d, %d unacked, %d in ERTM queue", sent,
+	       (int) chan->unacked_frames, skb_queue_len(&chan->tx_q));
+
+	return sent;
 }
 
 static int l2cap_retransmit_frames(struct l2cap_chan *chan)
@@ -2009,7 +2006,11 @@ static struct sk_buff *l2cap_create_iframe_pdu(struct l2cap_chan *chan,
 	lh->cid = cpu_to_le16(chan->dcid);
 	lh->len = cpu_to_le16(len + (hlen - L2CAP_HDR_SIZE));
 
-	__put_control(chan, 0, skb_put(skb, __ctrl_size(chan)));
+	/* Control header is populated later */
+	if (test_bit(FLAG_EXT_CTRL, &chan->flags))
+		put_unaligned_le32(0, skb_put(skb, L2CAP_EXT_CTRL_SIZE));
+	else
+		put_unaligned_le16(0, skb_put(skb, L2CAP_ENH_CTRL_SIZE));
 
 	if (sdulen)
 		put_unaligned_le16(sdulen, skb_put(skb, L2CAP_SDULEN_SIZE));
@@ -2020,9 +2021,7 @@ static struct sk_buff *l2cap_create_iframe_pdu(struct l2cap_chan *chan,
 		return ERR_PTR(err);
 	}
 
-	if (chan->fcs == L2CAP_FCS_CRC16)
-		put_unaligned_le16(0, skb_put(skb, L2CAP_FCS_SIZE));
-
+	bt_cb(skb)->control.fcs = chan->fcs;
 	bt_cb(skb)->control.retries = 0;
 	return skb;
 }