Bluetooth: Interleave with allowlist scan

This patch implements the interleaving between allowlist scan and
no-filter scan. It'll be used to save power when at least one monitor is
registered and at least one pending connection or one device to be
scanned for.

The durations of the allowlist scan and the no-filter scan are
controlled by MGMT command: Set Default System Configuration. The
default values are set randomly for now.
Signed-off-by: NHoward Chung <howardchung@google.com>
Reviewed-by: NAlain Michaud <alainm@chromium.org>
Reviewed-by: NManish Mandlik <mmandlik@chromium.org>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>
Signed-off-by: NJohan Hedberg <johan.hedberg@intel.com>

include/net/bluetooth/hci_core.h

@@ -361,6 +361,8 @@ struct hci_dev {
 	__u8		ssp_debug_mode;
 	__u8		hw_error_code;
 	__u32		clock;
+	__u16		advmon_allowlist_duration;
+	__u16		advmon_no_filter_duration;
 
 	__u16		devid_source;
 	__u16		devid_vendor;
@@ -542,6 +544,14 @@ struct hci_dev {
 	struct delayed_work	rpa_expired;
 	bdaddr_t		rpa;
 
+	enum {
+		INTERLEAVE_SCAN_NONE,
+		INTERLEAVE_SCAN_NO_FILTER,
+		INTERLEAVE_SCAN_ALLOWLIST
+	} interleave_scan_state;
+
+	struct delayed_work	interleave_scan;
+
 #if IS_ENABLED(CONFIG_BT_LEDS)
 	struct led_trigger	*power_led;
 #endif

net/bluetooth/hci_core.c

@@ -3592,6 +3592,9 @@ struct hci_dev *hci_alloc_dev(void)
 	hdev->cur_adv_instance = 0x00;
 	hdev->adv_instance_timeout = 0;
 
+	hdev->advmon_allowlist_duration = 300;
+	hdev->advmon_no_filter_duration = 500;
+
 	hdev->sniff_max_interval = 800;
 	hdev->sniff_min_interval = 80;
 

net/bluetooth/hci_request.c

@@ -378,6 +378,53 @@ void __hci_req_write_fast_connectable(struct hci_request *req, bool enable)
 		hci_req_add(req, HCI_OP_WRITE_PAGE_SCAN_TYPE, 1, &type);
 }
 
+static void start_interleave_scan(struct hci_dev *hdev)
+{
+	hdev->interleave_scan_state = INTERLEAVE_SCAN_NO_FILTER;
+	queue_delayed_work(hdev->req_workqueue,
+			   &hdev->interleave_scan, 0);
+}
+
+static bool is_interleave_scanning(struct hci_dev *hdev)
+{
+	return hdev->interleave_scan_state != INTERLEAVE_SCAN_NONE;
+}
+
+static void cancel_interleave_scan(struct hci_dev *hdev)
+{
+	bt_dev_dbg(hdev, "cancelling interleave scan");
+
+	cancel_delayed_work_sync(&hdev->interleave_scan);
+
+	hdev->interleave_scan_state = INTERLEAVE_SCAN_NONE;
+}
+
+/* Return true if interleave_scan wasn't started until exiting this function,
+ * otherwise, return false
+ */
+static bool __hci_update_interleaved_scan(struct hci_dev *hdev)
+{
+	/* If there is at least one ADV monitors and one pending LE connection
+	 * or one device to be scanned for, we should alternate between
+	 * allowlist scan and one without any filters to save power.
+	 */
+	bool use_interleaving = hci_is_adv_monitoring(hdev) &&
+				!(list_empty(&hdev->pend_le_conns) &&
+				  list_empty(&hdev->pend_le_reports));
+	bool is_interleaving = is_interleave_scanning(hdev);
+
+	if (use_interleaving && !is_interleaving) {
+		start_interleave_scan(hdev);
+		bt_dev_dbg(hdev, "starting interleave scan");
+		return true;
+	}
+
+	if (!use_interleaving && is_interleaving)
+		cancel_interleave_scan(hdev);
+
+	return false;
+}
+
 /* This function controls the background scanning based on hdev->pend_le_conns
  * list. If there are pending LE connection we start the background scanning,
  * otherwise we stop it.
@@ -450,8 +497,7 @@ static void __hci_update_background_scan(struct hci_request *req)
 			hci_req_add_le_scan_disable(req, false);
 
 		hci_req_add_le_passive_scan(req);
-
-		BT_DBG("%s starting background scanning", hdev->name);
+		bt_dev_dbg(hdev, "starting background scanning");
 	}
 }
 
@@ -848,12 +894,17 @@ static u8 update_white_list(struct hci_request *req)
 			return 0x00;
 	}
 
-	/* Once the controller offloading of advertisement monitor is in place,
-	 * the if condition should include the support of MSFT extension
-	 * support. If suspend is ongoing, whitelist should be the default to
-	 * prevent waking by random advertisements.
+	/* Use the allowlist unless the following conditions are all true:
+	 * - We are not currently suspending
+	 * - There are 1 or more ADV monitors registered
+	 * - Interleaved scanning is not currently using the allowlist
+	 *
+	 * Once the controller offloading of advertisement monitor is in place,
+	 * the above condition should include the support of MSFT extension
+	 * support.
 	 */
-	if (!idr_is_empty(&hdev->adv_monitors_idr) && !hdev->suspended)
+	if (!idr_is_empty(&hdev->adv_monitors_idr) && !hdev->suspended &&
+	    hdev->interleave_scan_state != INTERLEAVE_SCAN_ALLOWLIST)
 		return 0x00;
 
 	/* Select filter policy to use white list */
@@ -1006,6 +1057,10 @@ void hci_req_add_le_passive_scan(struct hci_request *req)
 				      &own_addr_type))
 		return;
 
+	if (__hci_update_interleaved_scan(hdev))
+		return;
+
+	bt_dev_dbg(hdev, "interleave state %d", hdev->interleave_scan_state);
 	/* Adding or removing entries from the white list must
 	 * happen before enabling scanning. The controller does
 	 * not allow white list modification while scanning.
@@ -1870,6 +1925,62 @@ static void adv_timeout_expire(struct work_struct *work)
 	hci_dev_unlock(hdev);
 }
 
+static int hci_req_add_le_interleaved_scan(struct hci_request *req,
+					   unsigned long opt)
+{
+	struct hci_dev *hdev = req->hdev;
+	int ret = 0;
+
+	hci_dev_lock(hdev);
+
+	if (hci_dev_test_flag(hdev, HCI_LE_SCAN))
+		hci_req_add_le_scan_disable(req, false);
+	hci_req_add_le_passive_scan(req);
+
+	switch (hdev->interleave_scan_state) {
+	case INTERLEAVE_SCAN_ALLOWLIST:
+		bt_dev_dbg(hdev, "next state: allowlist");
+		hdev->interleave_scan_state = INTERLEAVE_SCAN_NO_FILTER;
+		break;
+	case INTERLEAVE_SCAN_NO_FILTER:
+		bt_dev_dbg(hdev, "next state: no filter");
+		hdev->interleave_scan_state = INTERLEAVE_SCAN_ALLOWLIST;
+		break;
+	case INTERLEAVE_SCAN_NONE:
+		BT_ERR("unexpected error");
+		ret = -1;
+	}
+
+	hci_dev_unlock(hdev);
+
+	return ret;
+}
+
+static void interleave_scan_work(struct work_struct *work)
+{
+	struct hci_dev *hdev = container_of(work, struct hci_dev,
+					    interleave_scan.work);
+	u8 status;
+	unsigned long timeout;
+
+	if (hdev->interleave_scan_state == INTERLEAVE_SCAN_ALLOWLIST) {
+		timeout = msecs_to_jiffies(hdev->advmon_allowlist_duration);
+	} else if (hdev->interleave_scan_state == INTERLEAVE_SCAN_NO_FILTER) {
+		timeout = msecs_to_jiffies(hdev->advmon_no_filter_duration);
+	} else {
+		bt_dev_err(hdev, "unexpected error");
+		return;
+	}
+
+	hci_req_sync(hdev, hci_req_add_le_interleaved_scan, 0,
+		     HCI_CMD_TIMEOUT, &status);
+
+	/* Don't continue interleaving if it was canceled */
+	if (is_interleave_scanning(hdev))
+		queue_delayed_work(hdev->req_workqueue,
+				   &hdev->interleave_scan, timeout);
+}
+
 int hci_get_random_address(struct hci_dev *hdev, bool require_privacy,
 			   bool use_rpa, struct adv_info *adv_instance,
 			   u8 *own_addr_type, bdaddr_t *rand_addr)
@@ -3297,6 +3408,7 @@ void hci_request_setup(struct hci_dev *hdev)
 	INIT_DELAYED_WORK(&hdev->le_scan_disable, le_scan_disable_work);
 	INIT_DELAYED_WORK(&hdev->le_scan_restart, le_scan_restart_work);
 	INIT_DELAYED_WORK(&hdev->adv_instance_expire, adv_timeout_expire);
+	INIT_DELAYED_WORK(&hdev->interleave_scan, interleave_scan_work);
 }
 
 void hci_request_cancel_all(struct hci_dev *hdev)
@@ -3316,4 +3428,6 @@ void hci_request_cancel_all(struct hci_dev *hdev)
 		cancel_delayed_work_sync(&hdev->adv_instance_expire);
 		hdev->adv_instance_timeout = 0;
 	}
+
+	cancel_interleave_scan(hdev);
 }

net/bluetooth/mgmt_config.c

@@ -67,6 +67,8 @@ int read_def_system_config(struct sock *sk, struct hci_dev *hdev, void *data,
 		HDEV_PARAM_U16(0x001a, le_supv_timeout),
 		HDEV_PARAM_U16_JIFFIES_TO_MSECS(0x001b,
 						def_le_autoconnect_timeout),
+		HDEV_PARAM_U16(0x001d, advmon_allowlist_duration),
+		HDEV_PARAM_U16(0x001e, advmon_no_filter_duration),
 	};
 	struct mgmt_rp_read_def_system_config *rp = (void *)params;
 
@@ -138,6 +140,8 @@ int set_def_system_config(struct sock *sk, struct hci_dev *hdev, void *data,
 		case 0x0019:
 		case 0x001a:
 		case 0x001b:
+		case 0x001d:
+		case 0x001e:
 			if (len != sizeof(u16)) {
 				bt_dev_warn(hdev, "invalid length %d, exp %zu for type %d",
 					    len, sizeof(u16), type);
@@ -251,6 +255,12 @@ int set_def_system_config(struct sock *sk, struct hci_dev *hdev, void *data,
 			hdev->def_le_autoconnect_timeout =
 					msecs_to_jiffies(TLV_GET_LE16(buffer));
 			break;
+		case 0x0001d:
+			hdev->advmon_allowlist_duration = TLV_GET_LE16(buffer);
+			break;
+		case 0x0001e:
+			hdev->advmon_no_filter_duration = TLV_GET_LE16(buffer);
+			break;
 		default:
 			bt_dev_warn(hdev, "unsupported parameter %u", type);
 			break;