Bluetooth: Channel move request handling

On receipt of a channel move request, the request must be validated
based on the L2CAP mode, connection state, and controller
capabilities.  ERTM channels must have their state machines cleared
and transmission paused while the channel move takes place.

If the channel is being moved to an AMP controller then
an AMP physical link must be prepared.  Moving the channel back to
BR/EDR proceeds immediately.
Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Acked-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

net/bluetooth/l2cap_core.c

@@ -735,6 +735,12 @@ static void l2cap_send_cmd(struct l2cap_conn *conn, u8 ident, u8 code, u16 len,
 	hci_send_acl(conn->hchan, skb, flags);
 }
 
+static bool __chan_is_moving(struct l2cap_chan *chan)
+{
+	return chan->move_state != L2CAP_MOVE_STABLE &&
+	       chan->move_state != L2CAP_MOVE_WAIT_PREPARE;
+}
+
 static void l2cap_do_send(struct l2cap_chan *chan, struct sk_buff *skb)
 {
 	struct hci_conn *hcon = chan->conn->hcon;
@@ -996,6 +1002,41 @@ void l2cap_send_conn_req(struct l2cap_chan *chan)
 	l2cap_send_cmd(conn, chan->ident, L2CAP_CONN_REQ, sizeof(req), &req);
 }
 
+static void l2cap_move_setup(struct l2cap_chan *chan)
+{
+	struct sk_buff *skb;
+
+	BT_DBG("chan %p", chan);
+
+	if (chan->mode != L2CAP_MODE_ERTM)
+		return;
+
+	__clear_retrans_timer(chan);
+	__clear_monitor_timer(chan);
+	__clear_ack_timer(chan);
+
+	chan->retry_count = 0;
+	skb_queue_walk(&chan->tx_q, skb) {
+		if (bt_cb(skb)->control.retries)
+			bt_cb(skb)->control.retries = 1;
+		else
+			break;
+	}
+
+	chan->expected_tx_seq = chan->buffer_seq;
+
+	clear_bit(CONN_REJ_ACT, &chan->conn_state);
+	clear_bit(CONN_SREJ_ACT, &chan->conn_state);
+	l2cap_seq_list_clear(&chan->retrans_list);
+	l2cap_seq_list_clear(&chan->srej_list);
+	skb_queue_purge(&chan->srej_q);
+
+	chan->tx_state = L2CAP_TX_STATE_XMIT;
+	chan->rx_state = L2CAP_RX_STATE_MOVE;
+
+	set_bit(CONN_REMOTE_BUSY, &chan->conn_state);
+}
+
 static void l2cap_chan_ready(struct l2cap_chan *chan)
 {
 	/* This clears all conf flags, including CONF_NOT_COMPLETE */
@@ -4157,6 +4198,7 @@ static inline int l2cap_move_channel_req(struct l2cap_conn *conn,
 					 u16 cmd_len, void *data)
 {
 	struct l2cap_move_chan_req *req = data;
+	struct l2cap_chan *chan;
 	u16 icid = 0;
 	u16 result = L2CAP_MR_NOT_ALLOWED;
 
@@ -4170,9 +4212,78 @@ static inline int l2cap_move_channel_req(struct l2cap_conn *conn,
 	if (!enable_hs)
 		return -EINVAL;
 
-	/* Placeholder: Always refuse */
+	chan = l2cap_get_chan_by_dcid(conn, icid);
+	if (!chan) {
+		l2cap_send_move_chan_rsp(conn, cmd->ident, icid,
+					 L2CAP_MR_NOT_ALLOWED);
+		return 0;
+	}
+
+	if (chan->scid < L2CAP_CID_DYN_START ||
+	    chan->chan_policy == BT_CHANNEL_POLICY_BREDR_ONLY ||
+	    (chan->mode != L2CAP_MODE_ERTM &&
+	     chan->mode != L2CAP_MODE_STREAMING)) {
+		result = L2CAP_MR_NOT_ALLOWED;
+		goto send_move_response;
+	}
+
+	if (chan->local_amp_id == req->dest_amp_id) {
+		result = L2CAP_MR_SAME_ID;
+		goto send_move_response;
+	}
+
+	if (req->dest_amp_id) {
+		struct hci_dev *hdev;
+		hdev = hci_dev_get(req->dest_amp_id);
+		if (!hdev || hdev->dev_type != HCI_AMP ||
+		    !test_bit(HCI_UP, &hdev->flags)) {
+			if (hdev)
+				hci_dev_put(hdev);
+
+			result = L2CAP_MR_BAD_ID;
+			goto send_move_response;
+		}
+		hci_dev_put(hdev);
+	}
+
+	/* Detect a move collision.  Only send a collision response
+	 * if this side has "lost", otherwise proceed with the move.
+	 * The winner has the larger bd_addr.
+	 */
+	if ((__chan_is_moving(chan) ||
+	     chan->move_role != L2CAP_MOVE_ROLE_NONE) &&
+	    bacmp(conn->src, conn->dst) > 0) {
+		result = L2CAP_MR_COLLISION;
+		goto send_move_response;
+	}
+
+	chan->ident = cmd->ident;
+	chan->move_role = L2CAP_MOVE_ROLE_RESPONDER;
+	l2cap_move_setup(chan);
+	chan->move_id = req->dest_amp_id;
+	icid = chan->dcid;
+
+	if (!req->dest_amp_id) {
+		/* Moving to BR/EDR */
+		if (test_bit(CONN_LOCAL_BUSY, &chan->conn_state)) {
+			chan->move_state = L2CAP_MOVE_WAIT_LOCAL_BUSY;
+			result = L2CAP_MR_PEND;
+		} else {
+			chan->move_state = L2CAP_MOVE_WAIT_CONFIRM;
+			result = L2CAP_MR_SUCCESS;
+		}
+	} else {
+		chan->move_state = L2CAP_MOVE_WAIT_PREPARE;
+		/* Placeholder - uncomment when amp functions are available */
+		/*amp_accept_physical(chan, req->dest_amp_id);*/
+		result = L2CAP_MR_PEND;
+	}
+
+send_move_response:
 	l2cap_send_move_chan_rsp(conn, cmd->ident, icid, result);
 
+	l2cap_chan_unlock(chan);
+
 	return 0;
 }