Bluetooth: advertisement handling in new connect procedure

This change “Bluetooth: advertisement handling in new connect procedure” in Linux kernel is authored by Jakub Pawlowski <jpawlowski [at] google.com> on Fri Aug 7 20:22:54 2015 +0200.

Bluetooth: advertisement handling in new connect procedure

Currently, when trying to connect to already paired device that just
rotated its RPA MAC address, old address would be used and connection
would fail. In order to fix that, kernel must scan and receive
advertisement with fresh RPA before connecting.

This path makes sure that after advertisement is received from device that
we try to connect to, it is properly handled in check_pending_le_conn and
trigger connect attempt.

It also modifies hci_le_connect to make sure that connect attempt will be
properly continued.

Signed-off-by: Jakub Pawlowski <jpawlowski@google.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

This Linux change may have been applied to various maintained Linux releases and you can find Linux releases including commit 28a667c.

There are 109 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 net/bluetooth/hci_conn.c  | 52 +++++++++++++++++++++++++++++++++--------------
 net/bluetooth/hci_event.c | 51 ++++++++++++++++++++++++++--------------------
 net/bluetooth/mgmt.c      |  6 ++++++
 3 files changed, 72 insertions(+), 37 deletions(-)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 534feb7..85c6aa5 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -679,15 +679,18 @@ static void create_le_conn_complete(struct hci_dev *hdev, u8 status, u16 opcode)
 {
 	struct hci_conn *conn;
 
-	if (status == 0)
-		return;
+	hci_dev_lock(hdev);
+
+	conn = hci_lookup_le_connect(hdev);
+
+	if (!status) {
+		hci_connect_le_scan_cleanup(conn);
+		goto done;
+	}
 
 	BT_ERR("HCI request failed to create LE connection: status 0x%2.2x",
 	       status);
 
-	hci_dev_lock(hdev);
-
-	conn = hci_lookup_le_connect(hdev);
 	if (!conn)
 		goto done;
 
@@ -727,6 +730,7 @@ static void hci_req_add_le_create_conn(struct hci_request *req,
 	hci_req_add(req, HCI_OP_LE_CREATE_CONN, sizeof(cp), &cp);
 
 	conn->state = BT_CONNECT;
+	clear_bit(HCI_CONN_SCANNING, &conn->flags);
 }
 
 static void hci_req_directed_advertising(struct hci_request *req,
@@ -770,7 +774,7 @@ struct hci_conn *hci_connect_le(struct hci_dev *hdev, bdaddr_t *dst,
 				u8 role)
 {
 	struct hci_conn_params *params;
-	struct hci_conn *conn;
+	struct hci_conn *conn, *conn_unfinished;
 	struct smp_irk *irk;
 	struct hci_request req;
 	int err;
@@ -793,9 +797,17 @@ struct hci_conn *hci_connect_le(struct hci_dev *hdev, bdaddr_t *dst,
 	 * and return the object found.
 	 */
 	conn = hci_conn_hash_lookup_ba(hdev, LE_LINK, dst);
+	conn_unfinished = NULL;
 	if (conn) {
-		conn->pending_sec_level = sec_level;
-		goto done;
+		if (conn->state == BT_CONNECT &&
+		    test_bit(HCI_CONN_SCANNING, &conn->flags)) {
+			BT_DBG("will continue unfinished conn %pMR", dst);
+			conn_unfinished = conn;
+		} else {
+			if (conn->pending_sec_level < sec_level)
+				conn->pending_sec_level = sec_level;
+			goto done;
+		}
 	}
 
 	/* Since the controller supports only one LE connection attempt at a
@@ -808,10 +820,6 @@ struct hci_conn *hci_connect_le(struct hci_dev *hdev, bdaddr_t *dst,
 	 * resolving key, the connection needs to be established
 	 * to a resolvable random address.
 	 *
-	 * This uses the cached random resolvable address from
-	 * a previous scan. When no cached address is available,
-	 * try connecting to the identity address instead.
-	 *
 	 * Storing the resolvable random address is required here
 	 * to handle connection failures. The address will later
 	 * be resolved back into the original identity address
@@ -823,15 +831,23 @@ struct hci_conn *hci_connect_le(struct hci_dev *hdev, bdaddr_t *dst,
 		dst_type = ADDR_LE_DEV_RANDOM;
 	}
 
-	conn = hci_conn_add(hdev, LE_LINK, dst, role);
+	if (conn_unfinished) {
+		conn = conn_unfinished;
+		bacpy(&conn->dst, dst);
+	} else {
+		conn = hci_conn_add(hdev, LE_LINK, dst, role);
+	}
+
 	if (!conn)
 		return ERR_PTR(-ENOMEM);
 
 	conn->dst_type = dst_type;
 	conn->sec_level = BT_SECURITY_LOW;
-	conn->pending_sec_level = sec_level;
 	conn->conn_timeout = conn_timeout;
 
+	if (!conn_unfinished)
+		conn->pending_sec_level = sec_level;
+
 	hci_req_init(&req, hdev);
 
 	/* Disable advertising if we're active. For master role
@@ -896,7 +912,13 @@ struct hci_conn *hci_connect_le(struct hci_dev *hdev, bdaddr_t *dst,
 	}
 
 done:
-	hci_conn_hold(conn);
+	/* If this is continuation of connect started by hci_connect_le_scan,
+	 * it already called hci_conn_hold and calling it again would mess the
+	 * counter.
+	 */
+	if (!conn_unfinished)
+		hci_conn_hold(conn);
+
 	return conn;
 }
 
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 128c5b7..7ba35a9 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4640,42 +4640,49 @@ static struct hci_conn *check_pending_le_conn(struct hci_dev *hdev,
 	/* If we're not connectable only connect devices that we have in
 	 * our pend_le_conns list.
 	 */
-	params = hci_pend_le_action_lookup(&hdev->pend_le_conns,
-					   addr, addr_type);
+	params = hci_explicit_connect_lookup(hdev, addr, addr_type);
+
 	if (!params)
 		return NULL;
 
-	switch (params->auto_connect) {
-	case HCI_AUTO_CONN_DIRECT:
-		/* Only devices advertising with ADV_DIRECT_IND are
-		 * triggering a connection attempt. This is allowing
-		 * incoming connections from slave devices.
-		 */
-		if (adv_type != LE_ADV_DIRECT_IND)
+	if (!params->explicit_connect) {
+		switch (params->auto_connect) {
+		case HCI_AUTO_CONN_DIRECT:
+			/* Only devices advertising with ADV_DIRECT_IND are
+			 * triggering a connection attempt. This is allowing
+			 * incoming connections from slave devices.
+			 */
+			if (adv_type != LE_ADV_DIRECT_IND)
+				return NULL;
+			break;
+		case HCI_AUTO_CONN_ALWAYS:
+			/* Devices advertising with ADV_IND or ADV_DIRECT_IND
+			 * are triggering a connection attempt. This means
+			 * that incoming connectioms from slave device are
+			 * accepted and also outgoing connections to slave
+			 * devices are established when found.
+			 */
+			break;
+		default:
 			return NULL;
-		break;
-	case HCI_AUTO_CONN_ALWAYS:
-		/* Devices advertising with ADV_IND or ADV_DIRECT_IND
-		 * are triggering a connection attempt. This means
-		 * that incoming connectioms from slave device are
-		 * accepted and also outgoing connections to slave
-		 * devices are established when found.
-		 */
-		break;
-	default:
-		return NULL;
+		}
 	}
 
 	conn = hci_connect_le(hdev, addr, addr_type, BT_SECURITY_LOW,
 			      HCI_LE_AUTOCONN_TIMEOUT, HCI_ROLE_MASTER);
 	if (!IS_ERR(conn)) {
-		/* Store the pointer since we don't really have any
+		/* If HCI_AUTO_CONN_EXPLICIT is set, conn is already owned
+		 * by higher layer that tried to connect, if no then
+		 * store the pointer since we don't really have any
 		 * other owner of the object besides the params that
 		 * triggered it. This way we can abort the connection if
 		 * the parameters get removed and keep the reference
 		 * count consistent once the connection is established.
 		 */
-		params->conn = hci_conn_get(conn);
+
+		if (!params->explicit_connect)
+			params->conn = hci_conn_get(conn);
+
 		return conn;
 	}
 
diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
index 35418bb..5f5d785 100644
--- a/net/bluetooth/mgmt.c
+++ b/net/bluetooth/mgmt.c
@@ -6107,6 +6107,12 @@ static int hci_conn_params_set(struct hci_request *req, bdaddr_t *addr,
 	switch (auto_connect) {
 	case HCI_AUTO_CONN_DISABLED:
 	case HCI_AUTO_CONN_LINK_LOSS:
+		/* If auto connect is being disabled when we're trying to
+		 * connect to device, keep connecting.
+		 */
+		if (params->explicit_connect)
+			list_add(¶ms->action, &hdev->pend_le_conns);
+
 		__hci_update_background_scan(req);
 		break;
 	case HCI_AUTO_CONN_REPORT:

The commit for this change in Linux stable tree is 28a667c (patch).

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