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[v1] Bluetooth: disable filter dup when scan for adv monitor

Message ID 20210519102745.v1.1.I69e82377dd94ad7cba0cde75bcac2dce62fbc542@changeid (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series [v1] Bluetooth: disable filter dup when scan for adv monitor | expand

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Commit Message

Howard Chung May 19, 2021, 2:28 a.m. UTC 
From: Yun-Hao Chung <howardchung@chromium.org>

Disable duplicates filter when scanning for advertisement monitor for
the following reasons. The scanning includes active scan and passive
scan.

For HW pattern filtering (ex. MSFT), some controllers ignore
RSSI_Sampling_Period when the duplicates filter is enabled.

For SW pattern filtering, when we're not doing interleaved scanning, it
is necessary to disable duplicates filter, otherwise hosts can only
receive one advertisement and it's impossible to know if a peer is still
in range.

Reviewed-by: Archie Pusaka <apusaka@chromium.org>

Signed-off-by: Yun-Hao Chung <howardchung@chromium.org>
---

 net/bluetooth/hci_request.c | 42 ++++++++++++++++++++++++++++++++-----
 1 file changed, 37 insertions(+), 5 deletions(-)

Comments

Marcel Holtmann May 19, 2021, 8:47 p.m. UTC | #1 
Hi Howard,

> Disable duplicates filter when scanning for advertisement monitor for
> the following reasons. The scanning includes active scan and passive
> scan.
> 
> For HW pattern filtering (ex. MSFT), some controllers ignore
> RSSI_Sampling_Period when the duplicates filter is enabled.
> 
> For SW pattern filtering, when we're not doing interleaved scanning, it
> is necessary to disable duplicates filter, otherwise hosts can only
> receive one advertisement and it's impossible to know if a peer is still
> in range.

can we be a bit more specific on which controller does what. I am not inclined to always disable duplicate filtering unless your controller doesn’t do what you want it to do.

I also disagree with the last statement. If the device moved out of range (or comes back for that matter) you should get a HCI_VS_MSFT_LE_Monitor_Device_Event event that tells you if a device is in range or not.

Device leaving:

> HCI Event: LE Meta Event (0x3e) plen 43
      LE Advertising Report (0x02)
        Num reports: 1
        Event type: Non connectable undirected - ADV_NONCONN_IND (0x03)
        Address type: Random (0x01)
        Address: 01:9A:1F:C0:30:15 (Non-Resolvable)
        Data length: 31
        Flags: 0x1a
          LE General Discoverable Mode
          Simultaneous LE and BR/EDR (Controller)
          Simultaneous LE and BR/EDR (Host)
        16-bit Service UUIDs (complete): 1 entry
          Apple, Inc. (0xfd6f)
        Service Data (UUID 0xfd6f): f47698ff9243617d917ac521b5fcfd436afdb285
        RSSI: -86 dBm (0xaa)
> HCI Event: Vendor (0xff) plen 18
        23 79 54 33 77 88 97 68 02 01 15 30 c0 1f 9a 01  #yT3w..h...0....
        00 00                                            ..              

Device coming back:

> HCI Event: Vendor (0xff) plen 18
        23 79 54 33 77 88 97 68 02 01 95 b9 0b 32 22 2a  #yT3w..h.....2"*
        00 01                                            ..              
> HCI Event: LE Meta Event (0x3e) plen 43
      LE Advertising Report (0x02)
        Num reports: 1
        Event type: Non connectable undirected - ADV_NONCONN_IND (0x03)
        Address type: Random (0x01)
        Address: 2A:22:32:0B:B9:95 (Non-Resolvable)
        Data length: 31
        Flags: 0x1a
          LE General Discoverable Mode
          Simultaneous LE and BR/EDR (Controller)
          Simultaneous LE and BR/EDR (Host)
        16-bit Service UUIDs (complete): 1 entry
          Apple, Inc. (0xfd6f)
        Service Data (UUID 0xfd6f): 0b861791a0fb7adcf8b45f951f7d4b7c7fc8e3fd
        RSSI: -27 dBm (0xe5)

Regards

Marcel
Howard Chung May 20, 2021, 3:23 a.m. UTC | #2 
Hi Marcel,
Thanks for the comments.

On Thu, May 20, 2021 at 4:47 AM Marcel Holtmann <marcel@holtmann.org> wrote:
>
> Hi Howard,
>
> > Disable duplicates filter when scanning for advertisement monitor for
> > the following reasons. The scanning includes active scan and passive
> > scan.
> >
> > For HW pattern filtering (ex. MSFT), some controllers ignore
> > RSSI_Sampling_Period when the duplicates filter is enabled.
> >
> > For SW pattern filtering, when we're not doing interleaved scanning, it
> > is necessary to disable duplicates filter, otherwise hosts can only
> > receive one advertisement and it's impossible to know if a peer is still
> > in range.
>
> can we be a bit more specific on which controller does what. I am not inclined to always disable duplicate filtering unless your controller doesn’t do what you want it to do.

Will update the commit message and submit again.

>
> I also disagree with the last statement. If the device moved out of range (or comes back for that matter) you should get a HCI_VS_MSFT_LE_Monitor_Device_Event event that tells you if a device is in range or not.

The last statement is about software filtering, which is used when
MSFT is not supported. Software filtering in the kernel is basically
doing an LE passive scan. When the duplicate filter is enabled, some
controllers consider packets with the same address but different RSSIs
as duplicate thus not reporting to the host, which makes userspace not
able to tell if a peer is in range or not.
>
> Device leaving:
>
> > HCI Event: LE Meta Event (0x3e) plen 43
>       LE Advertising Report (0x02)
>         Num reports: 1
>         Event type: Non connectable undirected - ADV_NONCONN_IND (0x03)
>         Address type: Random (0x01)
>         Address: 01:9A:1F:C0:30:15 (Non-Resolvable)
>         Data length: 31
>         Flags: 0x1a
>           LE General Discoverable Mode
>           Simultaneous LE and BR/EDR (Controller)
>           Simultaneous LE and BR/EDR (Host)
>         16-bit Service UUIDs (complete): 1 entry
>           Apple, Inc. (0xfd6f)
>         Service Data (UUID 0xfd6f): f47698ff9243617d917ac521b5fcfd436afdb285
>         RSSI: -86 dBm (0xaa)
> > HCI Event: Vendor (0xff) plen 18
>         23 79 54 33 77 88 97 68 02 01 15 30 c0 1f 9a 01  #yT3w..h...0....
>         00 00                                            ..
>
> Device coming back:
>
> > HCI Event: Vendor (0xff) plen 18
>         23 79 54 33 77 88 97 68 02 01 95 b9 0b 32 22 2a  #yT3w..h.....2"*
>         00 01                                            ..
> > HCI Event: LE Meta Event (0x3e) plen 43
>       LE Advertising Report (0x02)
>         Num reports: 1
>         Event type: Non connectable undirected - ADV_NONCONN_IND (0x03)
>         Address type: Random (0x01)
>         Address: 2A:22:32:0B:B9:95 (Non-Resolvable)
>         Data length: 31
>         Flags: 0x1a
>           LE General Discoverable Mode
>           Simultaneous LE and BR/EDR (Controller)
>           Simultaneous LE and BR/EDR (Host)
>         16-bit Service UUIDs (complete): 1 entry
>           Apple, Inc. (0xfd6f)
>         Service Data (UUID 0xfd6f): 0b861791a0fb7adcf8b45f951f7d4b7c7fc8e3fd
>         RSSI: -27 dBm (0xe5)
>
> Regards
>
> Marcel
>
diff mbox series

Patch

diff --git a/net/bluetooth/hci_request.c b/net/bluetooth/hci_request.c
index fa9125b782f85..54be4f112ef55 100644
--- a/net/bluetooth/hci_request.c
+++ b/net/bluetooth/hci_request.c
@@ -932,7 +932,7 @@  static bool scan_use_rpa(struct hci_dev *hdev)
 
 static void hci_req_start_scan(struct hci_request *req, u8 type, u16 interval,
 			       u16 window, u8 own_addr_type, u8 filter_policy,
-			       bool addr_resolv)
+			       bool filter_dup, bool addr_resolv)
 {
 	struct hci_dev *hdev = req->hdev;
 
@@ -997,7 +997,7 @@  static void hci_req_start_scan(struct hci_request *req, u8 type, u16 interval,
 
 		memset(&ext_enable_cp, 0, sizeof(ext_enable_cp));
 		ext_enable_cp.enable = LE_SCAN_ENABLE;
-		ext_enable_cp.filter_dup = LE_SCAN_FILTER_DUP_ENABLE;
+		ext_enable_cp.filter_dup = filter_dup;
 
 		hci_req_add(req, HCI_OP_LE_SET_EXT_SCAN_ENABLE,
 			    sizeof(ext_enable_cp), &ext_enable_cp);
@@ -1016,7 +1016,7 @@  static void hci_req_start_scan(struct hci_request *req, u8 type, u16 interval,
 
 		memset(&enable_cp, 0, sizeof(enable_cp));
 		enable_cp.enable = LE_SCAN_ENABLE;
-		enable_cp.filter_dup = LE_SCAN_FILTER_DUP_ENABLE;
+		enable_cp.filter_dup = filter_dup;
 		hci_req_add(req, HCI_OP_LE_SET_SCAN_ENABLE, sizeof(enable_cp),
 			    &enable_cp);
 	}
@@ -1053,6 +1053,8 @@  void hci_req_add_le_passive_scan(struct hci_request *req)
 	u8 own_addr_type;
 	u8 filter_policy;
 	u16 window, interval;
+	/* Default is to enable duplicates filter */
+	u8 filter_dup = LE_SCAN_FILTER_DUP_ENABLE;
 	/* Background scanning should run with address resolution */
 	bool addr_resolv = true;
 
@@ -1106,6 +1108,19 @@  void hci_req_add_le_passive_scan(struct hci_request *req)
 	} else if (hci_is_adv_monitoring(hdev)) {
 		window = hdev->le_scan_window_adv_monitor;
 		interval = hdev->le_scan_int_adv_monitor;
+
+		/* Disable duplicates filter when scanning for advertisement
+		 * monitor for the following reasons.
+		 *
+		 * For HW pattern filtering (ex. MSFT), some controllers ignore
+		 * RSSI_Sampling_Period when the duplicates filter is enabled.
+		 *
+		 * For SW pattern filtering, when we're not doing interleaved
+		 * scanning, it is necessary to disable duplicates filter,
+		 * otherwise hosts can only receive one advertisement and it's
+		 * impossible to know if a peer is still in range.
+		 */
+		filter_dup = LE_SCAN_FILTER_DUP_DISABLE;
 	} else {
 		window = hdev->le_scan_window;
 		interval = hdev->le_scan_interval;
@@ -1113,7 +1128,8 @@  void hci_req_add_le_passive_scan(struct hci_request *req)
 
 	bt_dev_dbg(hdev, "LE passive scan with whitelist = %d", filter_policy);
 	hci_req_start_scan(req, LE_SCAN_PASSIVE, interval, window,
-			   own_addr_type, filter_policy, addr_resolv);
+			   own_addr_type, filter_policy, filter_dup,
+			   addr_resolv);
 }
 
 static bool adv_instance_is_scannable(struct hci_dev *hdev, u8 instance)
@@ -3135,6 +3151,8 @@  static int active_scan(struct hci_request *req, unsigned long opt)
 	u8 own_addr_type;
 	/* White list is not used for discovery */
 	u8 filter_policy = 0x00;
+	/* Default is to enable duplicates filter */
+	u8 filter_dup = LE_SCAN_FILTER_DUP_ENABLE;
 	/* Discovery doesn't require controller address resolution */
 	bool addr_resolv = false;
 	int err;
@@ -3159,9 +3177,23 @@  static int active_scan(struct hci_request *req, unsigned long opt)
 	if (err < 0)
 		own_addr_type = ADDR_LE_DEV_PUBLIC;
 
+	if (hci_is_adv_monitoring(hdev)) {
+		/* Duplicate filter should be disabled when some advertisement
+		 * monitor is activated, otherwise AdvMon can only receive one
+		 * advertisement for one peer(*) during active scanning, and
+		 * might report loss to these peers.
+		 *
+		 * Note that different controllers have different meanings of
+		 * |duplicate|. Some of them consider packets with the same
+		 * address as duplicate, and others consider packets with the
+		 * same address and the same RSSI as duplicate.
+		 */
+		filter_dup = LE_SCAN_FILTER_DUP_DISABLE;
+	}
+
 	hci_req_start_scan(req, LE_SCAN_ACTIVE, interval,
 			   hdev->le_scan_window_discovery, own_addr_type,
-			   filter_policy, addr_resolv);
+			   filter_policy, filter_dup, addr_resolv);
 	return 0;
 }