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Date:   Wed, 19 May 2021 10:28:33 +0800
Message-Id: <20210519102745.v1.1.I69e82377dd94ad7cba0cde75bcac2dce62fbc542@changeid>
Mime-Version: 1.0
Subject: [PATCH v1] Bluetooth: disable filter dup when scan for adv monitor
From:   Howard Chung <howardchung@google.com>
To:     linux-bluetooth@vger.kernel.org, marcel@holtmann.org
Cc:     chromeos-bluetooth-upstreaming@chromium.org,
        Yun-Hao Chung <howardchung@chromium.org>,
        Archie Pusaka <apusaka@chromium.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

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(-)

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;
 }
 
-- 
2.31.1.751.gd2f1c929bd-goog