xref: /btstack/src/ble/gatt_client.h (revision b3fcedb9c9ccbcc9680da165cd86f394be5d84a8)
1 /*
2  * Copyright (C) 2014 BlueKitchen GmbH
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the copyright holders nor the names of
14  *    contributors may be used to endorse or promote products derived
15  *    from this software without specific prior written permission.
16  * 4. Any redistribution, use, or modification is done solely for
17  *    personal benefit and not for any commercial purpose or for
18  *    monetary gain.
19  *
20  * THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
24  * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
26  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
27  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
30  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  *
33  * Please inquire about commercial licensing options at
34  * [email protected]
35  *
36  */
37 
38 
39 #ifndef btstack_gatt_client_h
40 #define btstack_gatt_client_h
41 
42 #include "hci.h"
43 
44 #if defined __cplusplus
45 extern "C" {
46 #endif
47 
48 typedef enum {
49     P_READY,
50     P_W2_SEND_SERVICE_QUERY,
51     P_W4_SERVICE_QUERY_RESULT,
52     P_W2_SEND_SERVICE_WITH_UUID_QUERY,
53     P_W4_SERVICE_WITH_UUID_RESULT,
54 
55     P_W2_SEND_ALL_CHARACTERISTICS_OF_SERVICE_QUERY,
56     P_W4_ALL_CHARACTERISTICS_OF_SERVICE_QUERY_RESULT,
57     P_W2_SEND_CHARACTERISTIC_WITH_UUID_QUERY,
58     P_W4_CHARACTERISTIC_WITH_UUID_QUERY_RESULT,
59 
60     P_W2_SEND_ALL_CHARACTERISTIC_DESCRIPTORS_QUERY,
61     P_W4_ALL_CHARACTERISTIC_DESCRIPTORS_QUERY_RESULT,
62 
63     P_W2_SEND_INCLUDED_SERVICE_QUERY,
64     P_W4_INCLUDED_SERVICE_QUERY_RESULT,
65     P_W2_SEND_INCLUDED_SERVICE_WITH_UUID_QUERY,
66     P_W4_INCLUDED_SERVICE_UUID_WITH_QUERY_RESULT,
67 
68     P_W2_SEND_READ_CHARACTERISTIC_VALUE_QUERY,
69     P_W4_READ_CHARACTERISTIC_VALUE_RESULT,
70 
71     P_W2_SEND_READ_BLOB_QUERY,
72     P_W4_READ_BLOB_RESULT,
73 
74     P_W2_SEND_READ_BY_TYPE_REQUEST,
75     P_W4_READ_BY_TYPE_RESPONSE,
76 
77     P_W2_SEND_READ_MULTIPLE_REQUEST,
78     P_W4_READ_MULTIPLE_RESPONSE,
79 
80     P_W2_SEND_WRITE_CHARACTERISTIC_VALUE,
81     P_W4_WRITE_CHARACTERISTIC_VALUE_RESULT,
82 
83     P_W2_PREPARE_WRITE,
84     P_W4_PREPARE_WRITE_RESULT,
85     P_W2_PREPARE_RELIABLE_WRITE,
86     P_W4_PREPARE_RELIABLE_WRITE_RESULT,
87 
88     P_W2_EXECUTE_PREPARED_WRITE,
89     P_W4_EXECUTE_PREPARED_WRITE_RESULT,
90     P_W2_CANCEL_PREPARED_WRITE,
91     P_W4_CANCEL_PREPARED_WRITE_RESULT,
92     P_W2_CANCEL_PREPARED_WRITE_DATA_MISMATCH,
93     P_W4_CANCEL_PREPARED_WRITE_DATA_MISMATCH_RESULT,
94 
95     P_W2_SEND_READ_CLIENT_CHARACTERISTIC_CONFIGURATION_QUERY,
96     P_W4_READ_CLIENT_CHARACTERISTIC_CONFIGURATION_QUERY_RESULT,
97     P_W2_WRITE_CLIENT_CHARACTERISTIC_CONFIGURATION,
98     P_W4_CLIENT_CHARACTERISTIC_CONFIGURATION_RESULT,
99 
100     P_W2_SEND_READ_CHARACTERISTIC_DESCRIPTOR_QUERY,
101     P_W4_READ_CHARACTERISTIC_DESCRIPTOR_RESULT,
102 
103     P_W2_SEND_READ_BLOB_CHARACTERISTIC_DESCRIPTOR_QUERY,
104     P_W4_READ_BLOB_CHARACTERISTIC_DESCRIPTOR_RESULT,
105 
106     P_W2_SEND_WRITE_CHARACTERISTIC_DESCRIPTOR,
107     P_W4_WRITE_CHARACTERISTIC_DESCRIPTOR_RESULT,
108 
109     // all long writes use this
110     P_W2_PREPARE_WRITE_CHARACTERISTIC_DESCRIPTOR,
111     P_W4_PREPARE_WRITE_CHARACTERISTIC_DESCRIPTOR_RESULT,
112     P_W2_EXECUTE_PREPARED_WRITE_CHARACTERISTIC_DESCRIPTOR,
113     P_W4_EXECUTE_PREPARED_WRITE_CHARACTERISTIC_DESCRIPTOR_RESULT,
114 
115     // gatt reliable write API use this (manual version of the above)
116     P_W2_PREPARE_WRITE_SINGLE,
117     P_W4_PREPARE_WRITE_SINGLE_RESULT,
118 
119     P_W4_CMAC_READY,
120     P_W4_CMAC_RESULT,
121     P_W2_SEND_SIGNED_WRITE,
122     P_W4_SEND_SINGED_WRITE_DONE,
123 } gatt_client_state_t;
124 
125 
126 typedef enum{
127     SEND_MTU_EXCHANGE,
128     SENT_MTU_EXCHANGE,
129     MTU_EXCHANGED
130 } gatt_client_mtu_t;
131 
132 typedef struct gatt_client{
133     btstack_linked_item_t    item;
134     // TODO: rename gatt_client_state -> state
135     gatt_client_state_t gatt_client_state;
136 
137     // user callback
138     btstack_packet_handler_t callback;
139 
140     hci_con_handle_t con_handle;
141 
142     uint8_t   address_type;
143     bd_addr_t address;
144     uint16_t mtu;
145     gatt_client_mtu_t mtu_state;
146 
147     uint16_t uuid16;
148     uint8_t  uuid128[16];
149 
150     uint16_t start_group_handle;
151     uint16_t end_group_handle;
152 
153     uint16_t query_start_handle;
154     uint16_t query_end_handle;
155 
156     uint8_t  characteristic_properties;
157     uint16_t characteristic_start_handle;
158 
159     uint16_t attribute_handle;
160     uint16_t attribute_offset;
161     uint16_t attribute_length;
162     uint8_t* attribute_value;
163 
164     // read multiple characteristic values
165     uint16_t    read_multiple_handle_count;
166     uint16_t  * read_multiple_handles;
167 
168     uint16_t client_characteristic_configuration_handle;
169     uint8_t  client_characteristic_configuration_value[2];
170 
171     uint8_t  filter_with_uuid;
172     uint8_t  send_confirmation;
173 
174     int      le_device_index;
175     uint8_t  cmac[8];
176 
177     btstack_timer_source_t gc_timeout;
178 } gatt_client_t;
179 
180 typedef struct gatt_client_notification {
181     btstack_linked_item_t    item;
182     btstack_packet_handler_t callback;
183     hci_con_handle_t con_handle;
184     uint16_t attribute_handle;
185 } gatt_client_notification_t;
186 
187 /* API_START */
188 
189 typedef struct {
190     uint16_t start_group_handle;
191     uint16_t end_group_handle;
192     uint16_t uuid16;
193     uint8_t  uuid128[16];
194 } gatt_client_service_t;
195 
196 typedef struct {
197     uint16_t start_handle;
198     uint16_t value_handle;
199     uint16_t end_handle;
200     uint16_t properties;
201     uint16_t uuid16;
202     uint8_t  uuid128[16];
203 } gatt_client_characteristic_t;
204 
205 typedef struct {
206     uint16_t handle;
207     uint16_t uuid16;
208     uint8_t  uuid128[16];
209 } gatt_client_characteristic_descriptor_t;
210 
211 /**
212  * @brief Set up GATT client.
213  */
214 void gatt_client_init(void);
215 
216 /**
217  * @brief MTU is available after the first query has completed. If status is equal to 0, it returns the real value, otherwise the default value of 23.
218  */
219 uint8_t gatt_client_get_mtu(hci_con_handle_t con_handle, uint16_t * mtu);
220 
221 /**
222  * @brief Returns if the GATT client is ready to receive a query. It is used with daemon.
223  */
224 int gatt_client_is_ready(hci_con_handle_t con_handle);
225 
226 /**
227  * @brief Discovers all primary services. For each found service, an le_service_event_t with type set to GATT_EVENT_SERVICE_QUERY_RESULT will be generated and passed to the registered callback. The gatt_complete_event_t, with type set to GATT_EVENT_QUERY_COMPLETE, marks the end of discovery.
228  */
229 uint8_t gatt_client_discover_primary_services(btstack_packet_handler_t callback, hci_con_handle_t con_handle);
230 
231 /**
232  * @brief Discovers a specific primary service given its UUID. This service may exist multiple times. For each found service, an le_service_event_t with type set to GATT_EVENT_SERVICE_QUERY_RESULT will be generated and passed to the registered callback. The gatt_complete_event_t, with type set to GATT_EVENT_QUERY_COMPLETE, marks the end of discovery.
233  */
234 uint8_t gatt_client_discover_primary_services_by_uuid16(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t uuid16);
235 uint8_t gatt_client_discover_primary_services_by_uuid128(btstack_packet_handler_t callback, hci_con_handle_t con_handle, const uint8_t  * uuid);
236 
237 /**
238  * @brief Finds included services within the specified service. For each found included service, an le_service_event_t with type set to GATT_EVENT_INCLUDED_SERVICE_QUERY_RESULT will be generated and passed to the registered callback. The gatt_complete_event_t with type set to GATT_EVENT_QUERY_COMPLETE, marks the end of discovery. Information about included service type (primary/secondary) can be retrieved either by sending an ATT find information request for the returned start group handle (returning the handle and the UUID for primary or secondary service) or by comparing the service to the list of all primary services.
239  */
240 uint8_t gatt_client_find_included_services_for_service(btstack_packet_handler_t callback, hci_con_handle_t con_handle, gatt_client_service_t  *service);
241 
242 /**
243  * @brief Discovers all characteristics within the specified service. For each found characteristic, an le_characteristics_event_t with type set to GATT_EVENT_CHARACTERISTIC_QUERY_RESULT will be generated and passed to the registered callback. The gatt_complete_event_t with type set to GATT_EVENT_QUERY_COMPLETE, marks the end of discovery.
244  */
245 uint8_t gatt_client_discover_characteristics_for_service(btstack_packet_handler_t callback, hci_con_handle_t con_handle, gatt_client_service_t  *service);
246 
247 /**
248  * @brief The following four functions are used to discover all characteristics within the specified service or handle range, and return those that match the given UUID. For each found characteristic, an le_characteristic_event_t with type set to GATT_EVENT_CHARACTERISTIC_QUERY_RESULT will be generated and passed to the registered callback. The gatt_complete_event_t with type set to GATT_EVENT_QUERY_COMPLETE, marks the end of discovery.
249  */
250 uint8_t gatt_client_discover_characteristics_for_handle_range_by_uuid16(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t start_handle, uint16_t end_handle, uint16_t uuid16);
251 uint8_t gatt_client_discover_characteristics_for_handle_range_by_uuid128(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t start_handle, uint16_t end_handle, uint8_t  * uuid);
252 uint8_t gatt_client_discover_characteristics_for_service_by_uuid16 (btstack_packet_handler_t callback, hci_con_handle_t con_handle, gatt_client_service_t  *service, uint16_t  uuid16);
253 uint8_t gatt_client_discover_characteristics_for_service_by_uuid128(btstack_packet_handler_t callback, hci_con_handle_t con_handle, gatt_client_service_t  *service, uint8_t  * uuid128);
254 
255 /**
256  * @brief Discovers attribute handle and UUID of a characteristic descriptor within the specified characteristic. For each found descriptor, an le_characteristic_descriptor_event_t with type set to GATT_EVENT_ALL_CHARACTERISTIC_DESCRIPTORS_QUERY_RESULT will be generated and passed to the registered callback. The gatt_complete_event_t with type set to GATT_EVENT_QUERY_COMPLETE, marks the end of discovery.
257  */
258 uint8_t gatt_client_discover_characteristic_descriptors(btstack_packet_handler_t callback, hci_con_handle_t con_handle, gatt_client_characteristic_t  *characteristic);
259 
260 /**
261  * @brief Reads the characteristic value using the characteristic's value handle. If the characteristic value is found, an le_characteristic_value_event_t with type set to GATT_EVENT_CHARACTERISTIC_VALUE_QUERY_RESULT will be generated and passed to the registered callback. The gatt_complete_event_t with type set to GATT_EVENT_QUERY_COMPLETE, marks the end of read.
262  */
263 uint8_t gatt_client_read_value_of_characteristic(btstack_packet_handler_t callback, hci_con_handle_t con_handle, gatt_client_characteristic_t  *characteristic);
264 uint8_t gatt_client_read_value_of_characteristic_using_value_handle(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t characteristic_value_handle);
265 
266 /**
267  * @brief Reads the characteric value of all characteristics with the uuid. For each found, an le_characteristic_value_event_t with type set to GATT_EVENT_CHARACTERISTIC_VALUE_QUERY_RESULT will be generated and passed to the registered callback. The gatt_complete_event_t with type set to GATT_EVENT_QUERY_COMPLETE, marks the end of read.
268  */
269 uint8_t gatt_client_read_value_of_characteristics_by_uuid16(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t start_handle, uint16_t end_handle, uint16_t uuid16);
270 uint8_t gatt_client_read_value_of_characteristics_by_uuid128(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t start_handle, uint16_t end_handle, uint8_t * uuid128);
271 
272 /**
273  * @brief Reads the long characteristic value using the characteristic's value handle. The value will be returned in several blobs. For each blob, an le_characteristic_value_event_t with type set to GATT_EVENT_CHARACTERISTIC_VALUE_QUERY_RESULT and updated value offset will be generated and passed to the registered callback. The gatt_complete_event_t with type set to GATT_EVENT_QUERY_COMPLETE, mark the end of read.
274  */
275 uint8_t gatt_client_read_long_value_of_characteristic(btstack_packet_handler_t callback, hci_con_handle_t con_handle, gatt_client_characteristic_t  *characteristic);
276 uint8_t gatt_client_read_long_value_of_characteristic_using_value_handle(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t characteristic_value_handle);
277 uint8_t gatt_client_read_long_value_of_characteristic_using_value_handle_with_offset(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t characteristic_value_handle, uint16_t offset);
278 
279 /*
280  * @brief Read multiple characteristic values
281  * @param number handles
282  * @param list_of_handles list of handles
283  */
284 uint8_t gatt_client_read_multiple_characteristic_values(btstack_packet_handler_t callback, hci_con_handle_t con_handle, int num_value_handles, uint16_t * value_handles);
285 
286 /**
287  * @brief Writes the characteristic value using the characteristic's value handle without an acknowledgment that the write was successfully performed.
288  */
289 uint8_t gatt_client_write_value_of_characteristic_without_response(hci_con_handle_t con_handle, uint16_t characteristic_value_handle, uint16_t length, uint8_t  * data);
290 
291 /**
292  * @brief Writes the authenticated characteristic value using the characteristic's value handle without an acknowledgment that the write was successfully performed.
293  */
294 uint8_t gatt_client_signed_write_without_response(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t handle, uint16_t message_len, uint8_t  * message);
295 
296 /**
297  * @brief Writes the characteristic value using the characteristic's value handle. The gatt_complete_event_t with type set to GATT_EVENT_QUERY_COMPLETE, marks the end of write. The write is successfully performed, if the event's status field is set to 0.
298  */
299 uint8_t gatt_client_write_value_of_characteristic(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t characteristic_value_handle, uint16_t length, uint8_t  * data);
300 uint8_t gatt_client_write_long_value_of_characteristic(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t characteristic_value_handle, uint16_t length, uint8_t  * data);
301 uint8_t gatt_client_write_long_value_of_characteristic_with_offset(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t characteristic_value_handle, uint16_t offset, uint16_t length, uint8_t  * data);
302 
303 /**
304  * @brief Writes of the long characteristic value using the characteristic's value handle. It uses server response to validate that the write was correctly received. The gatt_complete_event_t with type set to GATT_EVENT_QUERY_COMPLETE marks the end of write. The write is successfully performed, if the event's status field is set to 0.
305  */
306 uint8_t gatt_client_reliable_write_long_value_of_characteristic(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t characteristic_value_handle, uint16_t length, uint8_t  * data);
307 
308 /**
309  * @brief Reads the characteristic descriptor using its handle. If the characteristic descriptor is found, an le_characteristic_descriptor_event_t with type set to GATT_EVENT_CHARACTERISTIC_DESCRIPTOR_QUERY_RESULT will be generated and passed to the registered callback. The gatt_complete_event_t with type set to GATT_EVENT_QUERY_COMPLETE, marks the end of read.
310  */
311 uint8_t gatt_client_read_characteristic_descriptor(btstack_packet_handler_t callback, hci_con_handle_t con_handle, gatt_client_characteristic_descriptor_t  * descriptor);
312 uint8_t gatt_client_read_characteristic_descriptor_using_descriptor_handle(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t descriptor_handle);
313 
314 /**
315  * @brief Reads the long characteristic descriptor using its handle. It will be returned in several blobs. For each blob, an le_characteristic_descriptor_event_t with type set to GATT_EVENT_CHARACTERISTIC_DESCRIPTOR_QUERY_RESULT will be generated and passed to the registered callback. The gatt_complete_event_t with type set to GATT_EVENT_QUERY_COMPLETE, marks the end of read.
316  */
317 uint8_t gatt_client_read_long_characteristic_descriptor(btstack_packet_handler_t callback, hci_con_handle_t con_handle, gatt_client_characteristic_descriptor_t  * descriptor);
318 uint8_t gatt_client_read_long_characteristic_descriptor_using_descriptor_handle(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t descriptor_handle);
319 uint8_t gatt_client_read_long_characteristic_descriptor_using_descriptor_handle_with_offset(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t descriptor_handle, uint16_t offset);
320 
321 /**
322  * @brief Writes the characteristic descriptor using its handle. The gatt_complete_event_t with type set to GATT_EVENT_QUERY_COMPLETE, marks the end of write. The write is successfully performed, if the event's status field is set to 0.
323  */
324 uint8_t gatt_client_write_characteristic_descriptor(btstack_packet_handler_t callback, hci_con_handle_t con_handle, gatt_client_characteristic_descriptor_t  * descriptor, uint16_t length, uint8_t  * data);
325 uint8_t gatt_client_write_characteristic_descriptor_using_descriptor_handle(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t descriptor_handle, uint16_t length, uint8_t  * data);
326 uint8_t gatt_client_write_long_characteristic_descriptor(btstack_packet_handler_t callback, hci_con_handle_t con_handle, gatt_client_characteristic_descriptor_t  * descriptor, uint16_t length, uint8_t  * data);
327 uint8_t gatt_client_write_long_characteristic_descriptor_using_descriptor_handle(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t descriptor_handle, uint16_t length, uint8_t  * data);
328 uint8_t gatt_client_write_long_characteristic_descriptor_using_descriptor_handle_with_offset(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t descriptor_handle, uint16_t offset, uint16_t length, uint8_t  * data);
329 
330 /**
331  * @brief Writes the client characteristic configuration of the specified characteristic. It is used to subscribe for notifications or indications of the characteristic value. For notifications or indications specify: GATT_CLIENT_CHARACTERISTICS_CONFIGURATION_NOTIFICATION resp. GATT_CLIENT_CHARACTERISTICS_CONFIGURATION_INDICATION as configuration value.
332  */
333 uint8_t gatt_client_write_client_characteristic_configuration(btstack_packet_handler_t callback, hci_con_handle_t con_handle, gatt_client_characteristic_t * characteristic, uint16_t configuration);
334 
335 /**
336  * @brief Register for notifications and indications of a characteristic enabled by gatt_client_write_client_characteristic_configuration
337  * @param notification struct used to store registration
338  * @param packet_handler
339  * @param con_handle
340  * @param characteristic
341  */
342 void gatt_client_listen_for_characteristic_value_updates(gatt_client_notification_t * notification, btstack_packet_handler_t packet_handler, hci_con_handle_t con_handle, gatt_client_characteristic_t * characteristic);
343 
344 /**
345  * @brief -> gatt complete event
346  */
347 uint8_t gatt_client_prepare_write(btstack_packet_handler_t callback, hci_con_handle_t con_handle, uint16_t attribute_handle, uint16_t offset, uint16_t length, uint8_t * data);
348 
349 /**
350  * @brief -> gatt complete event
351  */
352 uint8_t gatt_client_execute_write(btstack_packet_handler_t callback, hci_con_handle_t con_handle);
353 
354 /**
355  * @brief -> gatt complete event
356  */
357 uint8_t gatt_client_cancel_write(btstack_packet_handler_t callback, hci_con_handle_t con_handle);
358 
359 /* API_END */
360 
361 // used by generated btstack_event.c
362 
363 void gatt_client_deserialize_service(const uint8_t *packet, int offset, gatt_client_service_t *service);
364 void gatt_client_deserialize_characteristic(const uint8_t * packet, int offset, gatt_client_characteristic_t * characteristic);
365 void gatt_client_deserialize_characteristic_descriptor(const uint8_t * packet, int offset, gatt_client_characteristic_descriptor_t * descriptor);
366 
367 // only used for testing
368 void gatt_client_pts_suppress_mtu_exchange(void);
369 
370 #if defined __cplusplus
371 }
372 #endif
373 
374 #endif
375