[PATCH v5 BlueZ 3/4] Bluetooth: L2CAP: Add BT_LE_CONN_PARAM socket option

["Felipe F. Tonello" <eu@felipetonello.com>]

There is a need for certain LE profiles (MIDI for example) to change the
current connection's parameters. In order to do that, this patch
introduces a new BT_LE_CONN_PARAM socket option for SOL_BLUETOOTH
protocol which allow user-space l2cap sockets to update the current
connection.

It necessary to expose all the connection parameters to user-space
because user-space are exposed to those values anyway, via PPCP
characteristic or particular profile specification.

If ROLE is SLAVE, then it will send a L2CAP_CONN_PARAM_UPDATE_REQ
signaling command to the MASTER, triggering proper LE parameter update
procedure. The connection parameters update will only occur upon a
successful L2CAP_CONN_PARAM_UPDATE_RSP sent by the MASTER.

If ROLE is MASTER, then immediately update the connection parameters.

Once the connection parameters are effective, a MGMT_EV_NEW_CONN_PARAM
event with the store_hint set is sent to user-space so an application
can store the connection parameters for persistence reasons.

Signed-off-by: Felipe F. Tonello <eu@felipetonello.com>
---
 include/net/bluetooth/bluetooth.h |   8 +++
 net/bluetooth/l2cap_sock.c        | 110 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 118 insertions(+)

diff --git a/include/net/bluetooth/bluetooth.h b/include/net/bluetooth/bluetooth.h
index 01487192f628..ce5b3abd3b27 100644
--- a/include/net/bluetooth/bluetooth.h
+++ b/include/net/bluetooth/bluetooth.h
@@ -122,6 +122,14 @@ struct bt_voice {
 #define BT_SNDMTU		12
 #define BT_RCVMTU		13
 
+#define BT_LE_CONN_PARAM	14
+struct bt_le_conn_param {
+	__u16 min_interval;
+	__u16 max_interval;
+	__u16 latency;
+	__u16 supervision_timeout;
+};
+
 __printf(1, 2)
 void bt_info(const char *fmt, ...);
 __printf(1, 2)
diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index 507b80d59dec..1e096bd9ddde 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -515,6 +515,47 @@ static int l2cap_sock_getsockopt(struct socket *sock, int level, int optname,
 	lock_sock(sk);
 
 	switch (optname) {
+	case BT_LE_CONN_PARAM: {
+		struct bt_le_conn_param conn_param;
+		struct hci_conn_params *params;
+		struct hci_conn *hcon;
+		struct hci_dev *hdev;
+
+		if (!chan->conn) {
+			err = -ENOTCONN;
+			break;
+		}
+
+		hcon = chan->conn->hcon;
+		hdev = hcon->hdev;
+		hci_dev_lock(hdev);
+
+		params = hci_conn_params_lookup(hdev, &hcon->dst,
+						hcon->dst_type);
+
+		memset(&conn_param, 0, sizeof(conn_param));
+
+		if (params) {
+			conn_param.min_interval = params->conn_min_interval;
+			conn_param.max_interval = params->conn_max_interval;
+			conn_param.latency = params->conn_latency;
+			conn_param.supervision_timeout =
+				params->supervision_timeout;
+		} else {
+			conn_param.min_interval = hdev->le_conn_min_interval;
+			conn_param.max_interval = hdev->le_conn_max_interval;
+			conn_param.latency = hdev->le_conn_latency;
+			conn_param.supervision_timeout = hdev->le_supv_timeout;
+		}
+
+		hci_dev_unlock(hdev);
+
+		len = min_t(unsigned int, len, sizeof(conn_param));
+		if (copy_to_user(optval, (char *)&conn_param, len))
+			err = -EFAULT;
+
+		break;
+	}
 	case BT_SECURITY:
 		if (chan->chan_type != L2CAP_CHAN_CONN_ORIENTED &&
 		    chan->chan_type != L2CAP_CHAN_FIXED &&
@@ -762,6 +803,75 @@ static int l2cap_sock_setsockopt(struct socket *sock, int level, int optname,
 	lock_sock(sk);
 
 	switch (optname) {
+	case BT_LE_CONN_PARAM: {
+		struct bt_le_conn_param conn_param;
+		struct hci_conn_params *hci_param;
+		struct hci_conn *hcon;
+		struct hci_dev *hdev;
+
+		len = min_t(unsigned int, sizeof(conn_param), optlen);
+		if (copy_from_user((char *)&conn_param, optval, len)) {
+			err = -EFAULT;
+			break;
+		}
+
+		if (!chan->conn) {
+			err = -ENOTCONN;
+			break;
+		}
+
+		err = hci_check_conn_params(conn_param.min_interval,
+					    conn_param.max_interval,
+					    conn_param.latency,
+					    conn_param.supervision_timeout);
+		if (err < 0) {
+			BT_ERR("Ignoring invalid connection parameters");
+			break;
+		}
+
+		hcon = chan->conn->hcon;
+		hdev = hcon->hdev;
+
+		hci_dev_lock(hdev);
+
+		/* we add new param in case it doesn't exist */
+		hci_param = hci_conn_params_add(hdev, &hcon->dst,
+						hcon->dst_type);
+		if (!hci_param) {
+			err = -ENOMEM;
+			BT_ERR("Failed to add connection parameters");
+			hci_dev_unlock(hcon->hdev);
+			break;
+		}
+
+		hci_dev_unlock(hdev);
+
+		/* Send a L2CAP connection parameters update request, if
+		 * the host role is slave.
+		 */
+		if (hcon->role == HCI_ROLE_SLAVE) {
+			l2cap_le_conn_update_req(chan->conn,
+						 conn_param.min_interval,
+						 conn_param.max_interval,
+						 conn_param.latency,
+						 conn_param.supervision_timeout);
+		} else {
+			/* this function also updates the hci_param value */
+			hci_le_conn_update(hcon, conn_param.min_interval,
+					   conn_param.max_interval,
+					   conn_param.latency,
+					   conn_param.supervision_timeout);
+
+			/* don't set the `store' hint */
+			mgmt_new_conn_param(hdev, &hcon->dst, hcon->dst_type,
+					    false, conn_param.min_interval,
+					    conn_param.max_interval,
+					    conn_param.latency,
+					    conn_param.supervision_timeout);
+		}
+		break;
+	}
+
 	case BT_SECURITY:
 		if (chan->chan_type != L2CAP_CHAN_CONN_ORIENTED &&
 		    chan->chan_type != L2CAP_CHAN_FIXED &&
-- 
2.12.2