Bluetooth: Add implementation for retransmitting all unacked frames

This adds l2cap_ertm_resend to retransmit frames based on the sequence
numbers in chan->retrans_list.  If the retransmit limit is reached for
any individual frame is reached, the connection is dropped.  skbs that
are cloned already are copied to avoid modifying shared data (this is
uncommon).  To retransmit all frames, l2cap_retransmit_all now builds
a list of all unacked sequence numbers and then calls
l2cap_ertm_resend.

Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

net/bluetooth/l2cap_core.c

@@ -1760,10 +1760,114 @@ static int l2cap_ertm_send(struct l2cap_chan *chan)
 	return sent;
 }
 
+static void l2cap_ertm_resend(struct l2cap_chan *chan)
+{
+	struct l2cap_ctrl control;
+	struct sk_buff *skb;
+	struct sk_buff *tx_skb;
+	u16 seq;
+
+	BT_DBG("chan %p", chan);
+
+	if (test_bit(CONN_REMOTE_BUSY, &chan->conn_state))
+		return;
+
+	while (chan->retrans_list.head != L2CAP_SEQ_LIST_CLEAR) {
+		seq = l2cap_seq_list_pop(&chan->retrans_list);
+
+		skb = l2cap_ertm_seq_in_queue(&chan->tx_q, seq);
+		if (!skb) {
+			BT_DBG("Error: Can't retransmit seq %d, frame missing",
+				seq);
+			continue;
+		}
+
+		bt_cb(skb)->control.retries++;
+		control = bt_cb(skb)->control;
+
+		if (chan->max_tx != 0 &&
+		    bt_cb(skb)->control.retries > chan->max_tx) {
+			BT_DBG("Retry limit exceeded (%d)", chan->max_tx);
+			l2cap_send_disconn_req(chan->conn, chan, ECONNRESET);
+			l2cap_seq_list_clear(&chan->retrans_list);
+			break;
+		}
+
+		control.reqseq = chan->buffer_seq;
+		if (test_and_clear_bit(CONN_SEND_FBIT, &chan->conn_state))
+			control.final = 1;
+		else
+			control.final = 0;
+
+		if (skb_cloned(skb)) {
+			/* Cloned sk_buffs are read-only, so we need a
+			 * writeable copy
+			 */
+			tx_skb = skb_copy(skb, GFP_ATOMIC);
+		} else {
+			tx_skb = skb_clone(skb, GFP_ATOMIC);
+		}
+
+		if (!tx_skb) {
+			l2cap_seq_list_clear(&chan->retrans_list);
+			break;
+		}
+
+		/* Update skb contents */
+		if (test_bit(FLAG_EXT_CTRL, &chan->flags)) {
+			put_unaligned_le32(__pack_extended_control(&control),
+					   tx_skb->data + L2CAP_HDR_SIZE);
+		} else {
+			put_unaligned_le16(__pack_enhanced_control(&control),
+					   tx_skb->data + L2CAP_HDR_SIZE);
+		}
+
+		if (chan->fcs == L2CAP_FCS_CRC16) {
+			u16 fcs = crc16(0, (u8 *) tx_skb->data, tx_skb->len);
+			put_unaligned_le16(fcs, skb_put(tx_skb,
+							L2CAP_FCS_SIZE));
+		}
+
+		l2cap_do_send(chan, tx_skb);
+
+		BT_DBG("Resent txseq %d", control.txseq);
+
+		chan->last_acked_seq = chan->buffer_seq;
+	}
+}
+
 static void l2cap_retransmit_all(struct l2cap_chan *chan,
 				 struct l2cap_ctrl *control)
 {
-	/* Placeholder */
+	struct sk_buff *skb;
+
+	BT_DBG("chan %p, control %p", chan, control);
+
+	if (control->poll)
+		set_bit(CONN_SEND_FBIT, &chan->conn_state);
+
+	l2cap_seq_list_clear(&chan->retrans_list);
+
+	if (test_bit(CONN_REMOTE_BUSY, &chan->conn_state))
+		return;
+
+	if (chan->unacked_frames) {
+		skb_queue_walk(&chan->tx_q, skb) {
+			if (bt_cb(skb)->control.txseq == control->reqseq ||
+				skb == chan->tx_send_head)
+				break;
+		}
+
+		skb_queue_walk_from(&chan->tx_q, skb) {
+			if (skb == chan->tx_send_head)
+				break;
+
+			l2cap_seq_list_append(&chan->retrans_list,
+					      bt_cb(skb)->control.txseq);
+		}
+
+		l2cap_ertm_resend(chan);
+	}
 }
 
 static void l2cap_send_ack(struct l2cap_chan *chan)