rp2: Enable BTstack pairing/bonding support.

pi-anl · pi-anl · commit d6b8b4ed9c40 · 2025-06-11T10:46:01.000+10:00
BTstack automatically generates and manages ER/IR keys via TLV
storage, providing secure pairing and bonding functionality
without requiring manual key generation.

Signed-off-by: Andrew Leech &lt;andrew.leech@planetinnovation.com.au&gt;
diff --git a/extmod/btstack/modbluetooth_btstack.c b/extmod/btstack/modbluetooth_btstack.c
@@ -115,6 +115,18 @@ typedef struct _mp_btstack_active_connection_t {
     uint32_t last_encryption_update;
 } mp_btstack_active_connection_t;
 
+#endif // MICROPY_PY_BLUETOOTH_ENABLE_GATT_CLIENT
+
+#if MICROPY_PY_BLUETOOTH_ENABLE_PAIRING_BONDING
+// Encryption state tracking to prevent duplicate events
+typedef struct _encryption_state_cache_t {
+    btstack_linked_item_t *next; // Must be first field to match btstack_linked_item.
+
+    uint16_t conn_handle;
+    bool is_encrypted;
+    uint32_t last_update_ms;
+} encryption_state_cache_t;
+
 static mp_btstack_active_connection_t *create_active_connection(uint16_t conn_handle) {
     DEBUG_printf("create_active_connection: conn_handle=%d\n", conn_handle);
     mp_btstack_active_connection_t *conn = m_new(mp_btstack_active_connection_t, 1);
@@ -160,6 +172,60 @@ static void remove_active_connection(uint16_t conn_handle) {
 }
 #endif
 
+#if MICROPY_PY_BLUETOOTH_ENABLE_PAIRING_BONDING
+// Encryption state management functions
+static encryption_state_cache_t *find_encryption_state(uint16_t conn_handle) {
+    btstack_linked_list_iterator_t it;
+    btstack_linked_list_iterator_init(&it, &MP_STATE_PORT(bluetooth_btstack_root_pointers)->encryption_states);
+    encryption_state_cache_t *state = NULL;
+    while (btstack_linked_list_iterator_has_next(&it)) {
+        state = (encryption_state_cache_t *)btstack_linked_list_iterator_next(&it);
+        if (state->conn_handle == conn_handle) {
+            return state;
+        }
+    }
+    return NULL;
+}
+
+static encryption_state_cache_t *get_or_create_encryption_state(uint16_t conn_handle) {
+    encryption_state_cache_t *state = find_encryption_state(conn_handle);
+    if (!state) {
+        state = m_new(encryption_state_cache_t, 1);
+        state->conn_handle = conn_handle;
+        state->is_encrypted = false;
+        state->last_update_ms = 0;
+        btstack_linked_list_add(&MP_STATE_PORT(bluetooth_btstack_root_pointers)->encryption_states, (btstack_linked_item_t *)state);
+    }
+    return state;
+}
+
+static void remove_encryption_state(uint16_t conn_handle) {
+    encryption_state_cache_t *state = find_encryption_state(conn_handle);
+    if (state) {
+        btstack_linked_list_remove(&MP_STATE_PORT(bluetooth_btstack_root_pointers)->encryption_states, (btstack_linked_item_t *)state);
+        m_del(encryption_state_cache_t, state, 1);
+    }
+}
+
+static bool should_forward_encryption_event(uint16_t conn_handle, bool is_encrypted) {
+    encryption_state_cache_t *state = get_or_create_encryption_state(conn_handle);
+    uint32_t current_time = mp_hal_ticks_ms();
+
+    // Check if state has actually changed
+    if (state->is_encrypted == is_encrypted) {
+        // State hasn't changed - check if enough time has passed to allow duplicate
+        if (current_time - state->last_update_ms < 1000) { // 1 second minimum
+            return false; // Suppress duplicate event
+        }
+    }
+
+    // Update state and timestamp
+    state->is_encrypted = is_encrypted;
+    state->last_update_ms = current_time;
+    return true; // Forward the event
+}
+#endif // MICROPY_PY_BLUETOOTH_ENABLE_PAIRING_BONDING
+
 // This needs to be separate to btstack_packet_handler otherwise we get
 // dual-delivery of the HCI_EVENT_LE_META event.
 static void btstack_packet_handler_att_server(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size) {
@@ -339,8 +405,14 @@ static void btstack_packet_handler_generic(uint8_t packet_type, uint16_t channel
         }
         #endif
 
-        mp_bluetooth_gatts_on_encryption_update(conn_handle,
-            encrypted, authenticated, bonded, desc->sm_actual_encryption_key_size);
+        // Use encryption state cache to prevent duplicate events
+        if (should_forward_encryption_event(conn_handle, encrypted)) {
+            DEBUG_printf("  --> forwarding encryption event: encrypted=%d, authenticated=%d, bonded=%d\n", encrypted, authenticated, bonded);
+            mp_bluetooth_gatts_on_encryption_update(conn_handle,
+                encrypted, authenticated, bonded, desc->sm_actual_encryption_key_size);
+        } else {
+            DEBUG_printf("  --> suppressing duplicate encryption event for conn_handle=%d\n", conn_handle);
+        }
     } else if (event_type == SM_EVENT_PASSKEY_DISPLAY_NUMBER) {
         mp_bluetooth_gap_on_passkey_action(sm_event_passkey_display_number_get_handle(packet), MP_BLUETOOTH_PASSKEY_ACTION_DISPLAY, sm_event_passkey_display_number_get_passkey(packet));
     } else if (event_type == SM_EVENT_PASSKEY_INPUT_NUMBER) {
@@ -365,6 +437,9 @@ static void btstack_packet_handler_generic(uint8_t packet_type, uint16_t channel
         #if MICROPY_PY_BLUETOOTH_ENABLE_GATT_CLIENT
         remove_active_connection(conn_handle);
         #endif
+        #if MICROPY_PY_BLUETOOTH_ENABLE_PAIRING_BONDING
+        remove_encryption_state(conn_handle);
+        #endif
     #if MICROPY_PY_BLUETOOTH_ENABLE_CENTRAL_MODE
     } else if (event_type == GAP_EVENT_ADVERTISING_REPORT) {
         DEBUG_printf("  --> gap advertising report\n");
@@ -712,18 +787,7 @@ int mp_bluetooth_init(void) {
     le_device_db_init();
     sm_init();
 
-    // Set cryptographically secure ER/IR keys for bonding
-    #if MICROPY_PY_BLUETOOTH_ENABLE_PAIRING_BONDING
-    // Use port-specific secure key generation
-    extern void mp_bluetooth_btstack_port_set_er_ir_keys(void);
-    mp_bluetooth_btstack_port_set_er_ir_keys();
-    #else
-    // Set blank ER/IR keys to suppress BTstack warning when pairing is disabled
-    sm_key_t dummy_key;
-    memset(dummy_key, 0, sizeof(dummy_key));
-    sm_set_er(dummy_key);
-    sm_set_ir(dummy_key);
-    #endif
+    // BTstack will automatically generate and store ER/IR keys via TLV when pairing is enabled
 
     #if MICROPY_PY_BLUETOOTH_ENABLE_GATT_CLIENT
     gatt_client_init();
diff --git a/extmod/btstack/modbluetooth_btstack.h b/extmod/btstack/modbluetooth_btstack.h
@@ -42,6 +42,9 @@ typedef struct _mp_bluetooth_btstack_root_pointers_t {
     // Characteristic (and descriptor) value storage.
     mp_gatts_db_t gatts_db;
 
+    // Encryption state cache for all connections (prevents duplicate events).
+    btstack_linked_list_t encryption_states;
+
     #if MICROPY_PY_BLUETOOTH_ENABLE_GATT_CLIENT
     // Registration for notify/indicate events.
     gatt_client_notification_t notification;
diff --git a/ports/rp2/CMakeLists.txt b/ports/rp2/CMakeLists.txt
@@ -332,6 +332,7 @@ if(MICROPY_PY_BLUETOOTH)
         MICROPY_PY_BLUETOOTH=1
         MICROPY_PY_BLUETOOTH_USE_SYNC_EVENTS=1
         MICROPY_PY_BLUETOOTH_ENABLE_CENTRAL_MODE=1
+        MICROPY_PY_BLUETOOTH_ENABLE_PAIRING_BONDING=1
     )
 endif()
 

Original file line number	Diff line number	Diff line change
`@@ -332,6 +332,7 @@ if(MICROPY_PY_BLUETOOTH)`
`332`	`332`	`MICROPY_PY_BLUETOOTH=1`
`333`	`333`	`MICROPY_PY_BLUETOOTH_USE_SYNC_EVENTS=1`
`334`	`334`	`MICROPY_PY_BLUETOOTH_ENABLE_CENTRAL_MODE=1`
	`335`	`+ MICROPY_PY_BLUETOOTH_ENABLE_PAIRING_BONDING=1`
`335`	`336`	`)`
`336`	`337`	`endif()`
`337`	`338`