bluetooth: rpc: reclaim GATT buffer on bt_disable

bt_enable() fails after a few bt_enable() -> bt_disable()
cycles because:
1. bt_enable() registers static services on the host device
2. on the host, the service data is allocated from shared
   GATT memory buffer and the memory used by a service is
   never released.
3. eventually, the GATT memory buffer is exhausted and 1
   fails.

Fix the most common scenario where only static services
are used, or all dynamic services are registered at once
by implementing the following changes:
1. in bt_disable(), unregister all static services
2. on the host, reset the GATT memory buffer if the last
   registered service has just been unregistered.

Signed-off-by: Damian Krolik <[email protected]>

Author: Damian-Nordic

subsys/bluetooth/rpc/client/bt_rpc_gap_client.c

@@ -150,6 +150,10 @@ int bt_disable(void)
 	nrf_rpc_cbor_cmd_no_err(&bt_rpc_grp, BT_DISABLE_RPC_CMD, &ctx, nrf_rpc_rsp_decode_i32,
 				&result);
 
+	if (IS_ENABLED(CONFIG_BT_CONN) && (result == 0)) {
+		result = bt_rpc_gatt_uninit();
+	}
+
 	return result;
 }
 

subsys/bluetooth/rpc/client/bt_rpc_gatt_client.c

@@ -683,38 +683,58 @@ int bt_rpc_gatt_init(void)
 	return 0;
 }
 
-#if defined(CONFIG_BT_GATT_DYNAMIC_DB)
-int bt_gatt_service_register(struct bt_gatt_service *svc)
-{
-	return send_service(svc);
-}
-
-int bt_gatt_service_unregister(struct bt_gatt_service *svc)
+static int remove_service(const struct bt_gatt_service *svc)
 {
 	struct nrf_rpc_cbor_ctx ctx;
 	int result;
 	size_t buffer_size_max = 3;
 	uint16_t svc_index;
 	int err;
 
-	NRF_RPC_CBOR_ALLOC(&bt_rpc_grp, ctx, buffer_size_max);
-
 	err = bt_rpc_gatt_service_to_index(svc, &svc_index);
 	if (err) {
 		return err;
 	}
 
+	NRF_RPC_CBOR_ALLOC(&bt_rpc_grp, ctx, buffer_size_max);
 	nrf_rpc_encode_uint(&ctx, svc_index);
-
-	nrf_rpc_cbor_cmd_no_err(&bt_rpc_grp, BT_RPC_GATT_SERVICE_UNREGISTER_RPC_CMD,
-				&ctx, nrf_rpc_rsp_decode_i32, &result);
+	nrf_rpc_cbor_cmd_no_err(&bt_rpc_grp, BT_RPC_GATT_SERVICE_UNREGISTER_RPC_CMD, &ctx,
+				nrf_rpc_rsp_decode_i32, &result);
 
 	if (result) {
 		return result;
 	}
 
 	return bt_rpc_gatt_remove_service(svc);
 }
+
+int bt_rpc_gatt_uninit(void)
+{
+	int err = 0;
+
+	STRUCT_SECTION_FOREACH(bt_gatt_service_static, svc)
+	{
+		int rc = remove_service((const struct bt_gatt_service *)svc);
+
+		/* Continue removing services even if removing one fails. */
+		if (err == 0) {
+			err = rc;
+		}
+	}
+
+	return err;
+}
+
+#if defined(CONFIG_BT_GATT_DYNAMIC_DB)
+int bt_gatt_service_register(struct bt_gatt_service *svc)
+{
+	return send_service(svc);
+}
+
+int bt_gatt_service_unregister(struct bt_gatt_service *svc)
+{
+	return remove_service(svc);
+}
 #endif /* defined(CONFIG_BT_GATT_DYNAMIC_DB) */
 
 static size_t bt_gatt_notify_params_buf_size(const struct bt_gatt_notify_params *data)

subsys/bluetooth/rpc/client/bt_rpc_gatt_client.h

@@ -20,14 +20,25 @@ extern "C" {
 
 /** @brief Initialize GATT functionality over RPC.
  *
- * This function registers all GATT static services and its attribute on a host.
- * Serives are registered as dynamic services on a host.
+ * This function registers all GATT static services and its attributes on the host.
+ *
+ * @note On the host, the client's static services are represented as dynamic services.
  *
  * @retval 0 If the operation was successful.
  *           Otherwise, a (negative) error code is returned.
  */
 int bt_rpc_gatt_init(void);
 
+/** @brief Uninitialize GATT functionality over RPC.
+ *
+ * This function reverses the operations performed by :c:func:`bt_rpc_gatt_init`.
+ * Specifically, it unregisters all GATT static services on the host.
+ *
+ * @retval 0 If the operation was successful.
+ *           Otherwise, a (negative) error code is returned.
+ */
+int bt_rpc_gatt_uninit(void);
+
 #ifdef __cplusplus
 }
 #endif

subsys/bluetooth/rpc/host/bt_rpc_gatt_host.c

@@ -740,6 +740,16 @@ static void bt_rpc_gatt_service_unregister_rpc_handler(const struct nrf_rpc_grou
 		result = bt_rpc_gatt_remove_service(svc);
 	}
 
+	if (!result && (bt_rpc_gatt_get_service_by_index(0) == NULL)) {
+		/*
+		 * The last service has been unregistered, so we can reclaim the entire GATT buffer.
+		 * Ideally, each dynamic service would use a separate buffer so that unregistering
+		 * a single service releases all its resources right away, but this requires
+		 * rewriting the GATT attribute memory management.
+		 */
+		net_buf_simple_reset(&gatt_buffer);
+	}
+
 	nrf_rpc_rsp_send_int(group, result);
 	return;
 decoding_error: