gap: ENABLE_EXPLICIT_LINK_KEY_REPLY allows for asynchronous link key lookup by application

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - HCI Dump: Support BTSnoop format in hci_dump_posix_fs.c for format = HCI_DUMP_BTSNOOP
 - HCI Dump RTT STDOUT: drop messages if RTT buffer is full and RTT is configured for non-blocking
 - hci_cmd: support variable length fields and arrayed parameters
+- GAP: ENABLE_EXPLICIT_LINK_KEY_REPLY allows for asynchronous link key lookup by application
 - POSIX: btstack_signal allows to register for callback on signal, e.g. ctrl-c
 - Windows: btstack_stdin_window_register_ctrl_c_callback allows to register for ctrl-c
 - A2DP: allow to register media codec validator for sink and source with:

doc/manual/docs-template/how_to.md

@@ -110,6 +110,7 @@ ENABLE_CONTROLLER_WARM_BOOT      | Enable stack startup without power cycle (if
 ENABLE_SEGGER_RTT                | Use SEGGER RTT for console output and packet log, see [additional options](#sec:rttConfiguration)
 ENABLE_EXPLICIT_CONNECTABLE_MODE_CONTROL | Disable calls to control Connectable Mode by L2CAP
 ENABLE_EXPLICIT_IO_CAPABILITIES_REPLY | Let application trigger sending IO Capabilities (Negative) Reply
+ENABLE_EXPLICIT_LINK_KEY_REPLY | Let application trigger sending Link Key (Negative) Response, allows for asynchronous link key lookup
 ENABLE_CLASSIC_OOB_PAIRING       | Enable support for classic Out-of-Band (OOB) pairing
 ENABLE_A2DP_SOURCE_EXPLICIT_CONFIG | Let application configure stream endpoint (skip auto-config of SBC endpoint)
 ENABLE_AVDTP_ACCEPTOR_EXPLICIT_START_STREAM_CONFIRMATION | allow accept or reject of stream start on A2DP_SUBEVENT_START_STREAM_REQUESTED

src/gap.h

@@ -844,6 +844,16 @@ uint8_t gap_ssp_io_capabilities_response(const bd_addr_t addr);
  */
 uint8_t gap_ssp_io_capabilities_negative(const bd_addr_t addr);
 
+/**
+ * Send Link Key Reponse
+ * @note Link Key (Negative) Reply is sent automaticallyu unless ENABLE_EXPLICIT_LINK_KEY_RESPONSE
+ * @param addr
+ * @param link_key
+ * @param type or INVALID_LINK_KEY if link key not available
+ * @return 0 if ok
+ */
+ uint8_t gap_send_link_key_response(const bd_addr_t addr, link_key_t link_key, link_key_type_t type);
+
 /**
  * @brief Enter Sniff mode
  * @param con_handle

src/hci.c

@@ -2827,6 +2827,7 @@ static void event_handler(uint8_t *packet, uint16_t size){
             break;
 
         case HCI_EVENT_LINK_KEY_REQUEST:
+#ifndef ENABLE_EXPLICIT_LINK_KEY_REPLY
             hci_event_link_key_request_get_bd_addr(packet, addr);
             conn = hci_connection_for_bd_addr_and_type(addr, BD_ADDR_TYPE_ACL);
             if (!conn) break;
@@ -6533,8 +6534,7 @@ int gap_ssp_confirmation_negative(const bd_addr_t addr){
     return gap_pairing_set_state_and_run(addr, GAP_PAIRING_STATE_SEND_CONFIRMATION_NEGATIVE);
 }
 
-#ifdef ENABLE_EXPLICIT_IO_CAPABILITIES_REPLY
-
+#if defined(ENABLE_EXPLICIT_IO_CAPABILITIES_REPLY) || defined(ENABLE_EXPLICIT_LINK_KEY_REPLY)
 static uint8_t gap_set_auth_flag_and_run(const bd_addr_t addr, hci_authentication_flags_t flag){
     hci_connection_t * conn = hci_connection_for_bd_addr_and_type(addr, BD_ADDR_TYPE_ACL);
     if (!conn) return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
@@ -6542,7 +6542,9 @@ static uint8_t gap_set_auth_flag_and_run(const bd_addr_t addr, hci_authenticatio
     hci_run();
     return ERROR_CODE_SUCCESS;
 }
+#endif
 
+#ifdef ENABLE_EXPLICIT_IO_CAPABILITIES_REPLY
 uint8_t gap_ssp_io_capabilities_response(const bd_addr_t addr){
     return gap_set_auth_flag_and_run(addr, AUTH_FLAG_SEND_IO_CAPABILITIES_REPLY);
 }
@@ -6588,6 +6590,20 @@ void gap_ssp_generate_oob_data(void){
 
 #endif
 
+#ifdef ENABLE_EXPLICIT_LINK_KEY_REPLY
+uint8_t gap_send_link_key_response(const bd_addr_t addr, link_key_t link_key, link_key_type_t type){
+    hci_connection_t * connection = hci_connection_for_bd_addr_and_type(addr, BD_ADDR_TYPE_ACL);
+    if (connection == NULL) {
+        return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
+    }
+
+    memcpy(connection->link_key, link_key, sizeof(link_key_t));
+    connection->link_key_type = type;
+
+    return gap_set_auth_flag_and_run(addr, AUTH_FLAG_HANDLE_LINK_KEY_REQUEST);
+}
+
+#endif // ENABLE_EXPLICIT_LINK_KEY_REPLY
 /**
  * @brief Set inquiry mode: standard, with RSSI, with RSSI + Extended Inquiry Results. Has to be called before power on.
  * @param inquiry_mode see bluetooth_defines.h