[bluetooth_proxy] Add an advertisement filter hook (#19220)

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>

esphome/components/bluetooth_proxy/__init__.py

@@ -395,6 +395,17 @@ async def _to_code_ble_hub(config: ConfigType) -> None:
     await _connections_to_code(var, config)
 
 
+def enable_advertisement_filter() -> None:
+    """Compile the advertisement filter hook into bluetooth_proxy.
+
+    Called by external filtering components from to_code(). The define behind
+    this is an implementation detail; do not emit it directly.
+
+    Public API for external components. Do not remove.
+    """
+    cg.add_define("USE_BLUETOOTH_PROXY_ADVERTISEMENT_FILTER")
+
+
 async def to_code(config: ConfigType) -> None:
     if CORE.is_esp32:
         await _to_code_esp32(config)

esphome/components/bluetooth_proxy/bluetooth_proxy.cpp

@@ -94,6 +94,15 @@ void BluetoothProxy::on_raw_advertisement_(const ble_device_base::RawAdvertiseme
   if (!api::global_api_server->is_connected() || this->api_connection_ == nullptr)
     return;
 
+#ifdef USE_BLUETOOTH_PROXY_ADVERTISEMENT_FILTER
+  // Ask the filter before the packet is queued, so a dropped advertisement never
+  // reaches the batch or the network.
+  if (this->advertisement_filter_.is_set() && !this->advertisement_filter_.should_forward(raw)) {
+    ESP_LOGVV(TAG, "Filtered packet from %012" PRIX64, raw.address);
+    return;
+  }
+#endif
+
   auto &adv = this->response_.advertisements[this->response_.advertisements_len];
   adv.address = raw.address;
   adv.rssi = raw.rssi;
@@ -184,6 +193,9 @@ void BluetoothProxy::dump_config() {
                 "  Adapter MAC: %s",
                 scan_mode, mac_out);
 #endif
+#ifdef USE_BLUETOOTH_PROXY_ADVERTISEMENT_FILTER
+  ESP_LOGCONFIG(TAG, "  Advertisement filter: %s", YESNO(this->advertisement_filter_.is_set()));
+#endif
 }
 
 #ifdef USE_BLUETOOTH_PROXY_CONNECTIONS

esphome/components/bluetooth_proxy/bluetooth_proxy.h

@@ -97,6 +97,29 @@ static_assert(pending_reply_round_trips(0xABCD112233445566ULL, 0x000011223344556
 static_assert(PendingReply{}.empty());
 #endif
 
+#ifdef USE_BLUETOOTH_PROXY_ADVERTISEMENT_FILTER
+/// Predicate slot letting an external component drop advertisements before they
+/// are queued for the API. Same shape as
+/// ble_device_base::RawAdvertisementCallback. Runs on the advertisement hot
+/// path, so it must be cheap and must not block.
+///
+/// Usage:
+///   proxy->set_advertisement_filter({this, [](void *self, const ble_device_base::RawAdvertisement &adv) {
+///     return static_cast<MyFilter *>(self)->should_forward(adv);
+///   }});
+///
+/// Returning false drops the advertisement. Not called at all while the API is
+/// disconnected, which matters to a stateful filter. Compiled in only when an
+/// external component calls bluetooth_proxy.enable_advertisement_filter().
+struct AdvertisementFilter {
+  void *instance{nullptr};
+  bool (*fn)(void *instance, const ble_device_base::RawAdvertisement &adv){nullptr};
+  /// A default-constructed slot is "no filter"; the proxy guards on this.
+  bool is_set() const { return this->fn != nullptr; }
+  bool should_forward(const ble_device_base::RawAdvertisement &adv) const { return this->fn(this->instance, adv); }
+};
+#endif  // USE_BLUETOOTH_PROXY_ADVERTISEMENT_FILTER
+
 class BluetoothProxy final : public Component {
 #ifdef USE_BLUETOOTH_PROXY_CONNECTIONS
   // Allow the connection to update connections_free_response_
@@ -162,6 +185,11 @@ class BluetoothProxy final : public Component {
   void set_active(bool active) { this->active_ = active; }
   bool has_active() { return this->active_; }
 
+#ifdef USE_BLUETOOTH_PROXY_ADVERTISEMENT_FILTER
+  /// One subscriber; a later call replaces an earlier one.
+  void set_advertisement_filter(AdvertisementFilter filter) { this->advertisement_filter_ = filter; }
+#endif
+
   uint32_t get_legacy_version() const {
     if (!this->active_) {
       return LEGACY_PASSIVE_ONLY_VERSION;
@@ -330,6 +358,10 @@ class BluetoothProxy final : public Component {
   // start on an even word, closing two alignment holes.
   uint32_t last_advertisement_flush_time_{0};
 
+#ifdef USE_BLUETOOTH_PROXY_ADVERTISEMENT_FILTER
+  AdvertisementFilter advertisement_filter_{};
+#endif
+
   // BLE advertisement batching
   api::BluetoothLERawAdvertisementsResponse response_;
 

esphome/core/defines.h

@@ -329,6 +329,8 @@
 #else
 #define BLUETOOTH_PROXY_MAX_CONNECTIONS 0
 #endif
+// Defined here so static analysis parses the slot and its call site.
+#define USE_BLUETOOTH_PROXY_ADVERTISEMENT_FILTER
 #define BLUETOOTH_PROXY_ADVERTISEMENT_BATCH_SIZE 16
 #endif
 

tests/component_tests/bluetooth_proxy/test_advertisement_filter.py

@@ -0,0 +1,13 @@
+"""The codegen hook external filtering components use to turn on the filter slot."""
+
+from esphome.components import bluetooth_proxy
+from esphome.core import CORE
+
+
+def test_enable_advertisement_filter_emits_define() -> None:
+    """External components call this rather than emitting the define."""
+    bluetooth_proxy.enable_advertisement_filter()
+
+    assert "USE_BLUETOOTH_PROXY_ADVERTISEMENT_FILTER" in {
+        define.name for define in CORE.defines
+    }

tests/components/bluetooth_proxy/test-advertisement-filter.esp32-s3-idf.yaml

@@ -0,0 +1,12 @@
+# Compile the gated filter path; no external component is in-tree to call
+# enable_advertisement_filter(), so the define is forced here.
+<<: !include common.yaml
+
+esphome:
+  build_flags:
+    - "-DUSE_BLUETOOTH_PROXY_ADVERTISEMENT_FILTER"
+
+esp32_ble_tracker:
+
+bluetooth_proxy:
+  active: true