backends/scanner: always filter by service_uuids

It was noted that on Linux, if another app was scanning at the same
time, BlueZ would trigger RSSI changes for all devices, even if they
they didn't match the service_uuids filter.

This change ensures that we always filter by service_uuids, even if
the OS isn't doing it for us.

On Windows, the OS wasn't filtering for us anyway, so we can just move
that code to the shared call_detection_callbacks() so that all backends
will make use of it.

Fixes: #1534

Author: dlech

CHANGELOG.rst

@@ -34,6 +34,7 @@ Fixed
 * Fixed using wrong value for ``tx_power`` in Android backend. Fixes #1532.
 * Fixed 4-character UUIDs not working on ``BleakClient.*_gatt_char`` methods. Fixes #1498.
 * Fixed race condition with getting max PDU size on Windows. Fixes #1497.
+* Fixed filtering advertisement data by service UUID when multiple apps are scanning. Fixes #1534.
 
 `0.21.1`_ (2023-09-08)
 ======================

bleak/backends/scanner.py

@@ -206,6 +206,24 @@ def call_detection_callbacks(
         Backend implementations should call this method when an advertisement
         event is received from the OS.
         """
+
+        # Backends will make best effort to filter out advertisements that
+        # don't match the service UUIDs, but if other apps are scanning at the
+        # same time or something like that, we may still receive advertisements
+        # that don't match. So we need to do more filtering here to get the
+        # expected behavior.
+
+        if self._service_uuids:
+            if not advertisement_data.service_uuids:
+                return
+
+            for uuid in advertisement_data.service_uuids:
+                if uuid in self._service_uuids:
+                    break
+            else:
+                # if there were no matching service uuids, the don't call the callback
+                return
+
         for callback in self._ad_callbacks.values():
             callback(device, advertisement_data)
 

bleak/backends/winrt/scanner.py

@@ -96,6 +96,11 @@ def __init__(
         else:
             self._scanning_mode = BluetoothLEScanningMode.ACTIVE
 
+        # Unfortunately, due to the way Windows handles filtering, we can't
+        # make use of the service_uuids filter here. If we did we would only
+        # get the advertisement data or the scan data, but not both, so would
+        # miss out on other essential data. Advanced users can pass their own
+        # filters though if they want to.
         self._signal_strength_filter = kwargs.get("SignalStrengthFilter", None)
         self._advertisement_filter = kwargs.get("AdvertisementFilter", None)
 
@@ -198,20 +203,6 @@ def _received_handler(
             bdaddr, local_name, raw_data, advertisement_data
         )
 
-        # On Windows, we have to fake service UUID filtering. If we were to pass
-        # a BluetoothLEAdvertisementFilter to the BluetoothLEAdvertisementWatcher
-        # with the service UUIDs appropriately set, we would no longer receive
-        # scan response data (which commonly contains the local device name).
-        # So we have to do it like this instead.
-
-        if self._service_uuids:
-            for uuid in uuids:
-                if uuid in self._service_uuids:
-                    break
-            else:
-                # if there were no matching service uuids, the don't call the callback
-                return
-
         self.call_detection_callbacks(device, advertisement_data)
 
     def _stopped_handler(self, sender, e):