xref: /btstack/src/ble/att_db.c (revision 9d622fde0d99729ba17a695ac40958123a7717a3)
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 #define __BTSTACK_FILE__ "att_db.c"
39 
40 
41 #include <stdio.h>
42 #include <string.h>
43 
44 #include "ble/att_db.h"
45 #include "ble/core.h"
46 #include "bluetooth.h"
47 #include "btstack_debug.h"
48 #include "btstack_util.h"
49 
50 typedef enum {
51     ATT_READ,
52     ATT_WRITE,
53 } att_operation_t;
54 
55 // Buetooth Base UUID 00000000-0000-1000-8000-00805F9B34FB in little endian
56 static const uint8_t bluetooth_base_uuid[] = { 0xfb, 0x34, 0x9b, 0x5f, 0x80, 0x00, 0x00, 0x80, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
57 
58 
59 static int is_Bluetooth_Base_UUID(uint8_t const *uuid){
60     if (memcmp(&uuid[0],  &bluetooth_base_uuid[0], 12)) return 0;
61     if (memcmp(&uuid[14], &bluetooth_base_uuid[14], 2)) return 0;
62     return 1;
63 
64 }
65 
66 static uint16_t uuid16_from_uuid(uint16_t uuid_len, uint8_t * uuid){
67     if (uuid_len == 2) return little_endian_read_16(uuid, 0);
68     if (!is_Bluetooth_Base_UUID(uuid)) return 0;
69     return little_endian_read_16(uuid, 12);
70 }
71 
72 // ATT Database
73 
74 // new java-style iterator
75 typedef struct att_iterator {
76     // private
77     uint8_t const * att_ptr;
78     // public
79     uint16_t size;
80     uint16_t flags;
81     uint16_t handle;
82     uint8_t  const * uuid;
83     uint16_t value_len;
84     uint8_t  const * value;
85 } att_iterator_t;
86 
87 static void att_persistent_ccc_cache(att_iterator_t * it);
88 
89 static uint8_t const * att_db = NULL;
90 static att_read_callback_t  att_read_callback  = NULL;
91 static att_write_callback_t att_write_callback = NULL;
92 static uint8_t  att_prepare_write_error_code   = 0;
93 static uint16_t att_prepare_write_error_handle = 0x0000;
94 
95 // single cache for att_is_persistent_ccc - stores flags before write callback
96 static uint16_t att_persistent_ccc_handle;
97 static uint16_t att_persistent_ccc_uuid16;
98 
99 static void att_iterator_init(att_iterator_t *it){
100     it->att_ptr = att_db;
101 }
102 
103 static int att_iterator_has_next(att_iterator_t *it){
104     return it->att_ptr != NULL;
105 }
106 
107 static void att_iterator_fetch_next(att_iterator_t *it){
108     it->size   = little_endian_read_16(it->att_ptr, 0);
109     if (it->size == 0){
110         it->flags = 0;
111         it->handle = 0;
112         it->uuid = NULL;
113         it->value_len = 0;
114         it->value = NULL;
115         it->att_ptr = NULL;
116         return;
117     }
118     it->flags  = little_endian_read_16(it->att_ptr, 2);
119     it->handle = little_endian_read_16(it->att_ptr, 4);
120     it->uuid   = &it->att_ptr[6];
121     // handle 128 bit UUIDs
122     if (it->flags & ATT_PROPERTY_UUID128){
123         it->value_len = it->size - 22;
124         it->value  = &it->att_ptr[22];
125     } else {
126         it->value_len = it->size - 8;
127         it->value  = &it->att_ptr[8];
128     }
129     // advance AFTER setting values
130     it->att_ptr += it->size;
131 }
132 
133 static int att_iterator_match_uuid16(att_iterator_t *it, uint16_t uuid){
134     if (it->handle == 0) return 0;
135     if (it->flags & ATT_PROPERTY_UUID128){
136         if (!is_Bluetooth_Base_UUID(it->uuid)) return 0;
137         return little_endian_read_16(it->uuid, 12) == uuid;
138     }
139     return little_endian_read_16(it->uuid, 0)  == uuid;
140 }
141 
142 static int att_iterator_match_uuid(att_iterator_t *it, uint8_t *uuid, uint16_t uuid_len){
143     if (it->handle == 0) return 0;
144     // input: UUID16
145     if (uuid_len == 2) {
146         return att_iterator_match_uuid16(it, little_endian_read_16(uuid, 0));
147     }
148     // input and db: UUID128
149     if (it->flags & ATT_PROPERTY_UUID128){
150         return memcmp(it->uuid, uuid, 16) == 0;
151     }
152     // input: UUID128, db: UUID16
153     if (!is_Bluetooth_Base_UUID(uuid)) return 0;
154     return little_endian_read_16(uuid, 12) == little_endian_read_16(it->uuid, 0);
155 }
156 
157 
158 static int att_find_handle(att_iterator_t *it, uint16_t handle){
159     if (handle == 0) return 0;
160     att_iterator_init(it);
161     while (att_iterator_has_next(it)){
162         att_iterator_fetch_next(it);
163         if (it->handle != handle) continue;
164         return 1;
165     }
166     return 0;
167 }
168 
169 // experimental client API
170 uint16_t att_uuid_for_handle(uint16_t attribute_handle){
171     att_iterator_t it;
172     int ok = att_find_handle(&it, attribute_handle);
173     if (!ok) return 0;
174     if (it.flags & ATT_PROPERTY_UUID128) return 0;
175     return little_endian_read_16(it.uuid, 0);
176 }
177 // end of client API
178 
179 static void att_update_value_len(att_iterator_t *it, hci_con_handle_t con_handle){
180     if ((it->flags & ATT_PROPERTY_DYNAMIC) == 0) return;
181     it->value_len = (*att_read_callback)(con_handle, it->handle, 0, NULL, 0);
182     return;
183 }
184 
185 // copy attribute value from offset into buffer with given size
186 static int att_copy_value(att_iterator_t *it, uint16_t offset, uint8_t * buffer, uint16_t buffer_size, hci_con_handle_t con_handle){
187 
188     // DYNAMIC
189     if (it->flags & ATT_PROPERTY_DYNAMIC){
190         return (*att_read_callback)(con_handle, it->handle, offset, buffer, buffer_size);
191     }
192 
193     // STATIC
194     uint16_t bytes_to_copy = it->value_len - offset;
195     if (bytes_to_copy > buffer_size){
196         bytes_to_copy = buffer_size;
197     }
198     memcpy(buffer, it->value, bytes_to_copy);
199     return bytes_to_copy;
200 }
201 
202 void att_set_db(uint8_t const * db){
203     att_db = db;
204 }
205 
206 void att_set_read_callback(att_read_callback_t callback){
207     att_read_callback = callback;
208 }
209 
210 void att_set_write_callback(att_write_callback_t callback){
211     att_write_callback = callback;
212 }
213 
214 void att_dump_attributes(void){
215     att_iterator_t it;
216     att_iterator_init(&it);
217     uint8_t uuid128[16];
218     while (att_iterator_has_next(&it)){
219         att_iterator_fetch_next(&it);
220         if (it.handle == 0) {
221             log_info("Handle: END");
222             return;
223         }
224         log_info("Handle: 0x%04x, flags: 0x%04x, uuid: ", it.handle, it.flags);
225         if (it.flags & ATT_PROPERTY_UUID128){
226             reverse_128(it.uuid, uuid128);
227             log_info("%s", uuid128_to_str(uuid128));
228         } else {
229             log_info("%04x", little_endian_read_16(it.uuid, 0));
230         }
231         log_info(", value_len: %u, value: ", it.value_len);
232         log_info_hexdump(it.value, it.value_len);
233     }
234 }
235 
236 static void att_prepare_write_reset(void){
237     att_prepare_write_error_code = 0;
238     att_prepare_write_error_handle = 0x0000;
239 }
240 
241 static void att_prepare_write_update_errors(uint8_t error_code, uint16_t handle){
242     // first ATT_ERROR_INVALID_ATTRIBUTE_VALUE_LENGTH has highest priority
243     if (error_code == ATT_ERROR_INVALID_ATTRIBUTE_VALUE_LENGTH && error_code != att_prepare_write_error_code){
244         att_prepare_write_error_code = error_code;
245         att_prepare_write_error_handle = handle;
246         return;
247     }
248     // first ATT_ERROR_INVALID_OFFSET is next
249     if (error_code == ATT_ERROR_INVALID_OFFSET && att_prepare_write_error_code == 0){
250         att_prepare_write_error_code = error_code;
251         att_prepare_write_error_handle = handle;
252         return;
253     }
254 }
255 
256 static uint16_t setup_error(uint8_t * response_buffer, uint16_t request, uint16_t handle, uint8_t error_code){
257     response_buffer[0] = ATT_ERROR_RESPONSE;
258     response_buffer[1] = request;
259     little_endian_store_16(response_buffer, 2, handle);
260     response_buffer[4] = error_code;
261     return 5;
262 }
263 
264 static inline uint16_t setup_error_read_not_permitted(uint8_t * response_buffer, uint16_t request, uint16_t start_handle){
265     return setup_error(response_buffer, request, start_handle, ATT_ERROR_READ_NOT_PERMITTED);
266 }
267 
268 static inline uint16_t setup_error_write_not_permitted(uint8_t * response_buffer, uint16_t request, uint16_t start_handle){
269     return setup_error(response_buffer, request, start_handle, ATT_ERROR_WRITE_NOT_PERMITTED);
270 }
271 
272 static inline uint16_t setup_error_atribute_not_found(uint8_t * response_buffer, uint16_t request, uint16_t start_handle){
273     return setup_error(response_buffer, request, start_handle, ATT_ERROR_ATTRIBUTE_NOT_FOUND);
274 }
275 
276 static inline uint16_t setup_error_invalid_handle(uint8_t * response_buffer, uint16_t request, uint16_t handle){
277     return setup_error(response_buffer, request, handle, ATT_ERROR_INVALID_HANDLE);
278 }
279 
280 static inline uint16_t setup_error_invalid_offset(uint8_t * response_buffer, uint16_t request, uint16_t handle){
281     return setup_error(response_buffer, request, handle, ATT_ERROR_INVALID_OFFSET);
282 }
283 
284 static uint8_t att_validate_security(att_connection_t * att_connection, att_operation_t operation, att_iterator_t * it){
285     UNUSED(operation);
286     int required_encryption_size = it->flags >> 12;
287     if (required_encryption_size) required_encryption_size++;   // store -1 to fit into 4 bit
288     log_debug("att_validate_security. flags 0x%04x - req enc size %u, authorized %u, authenticated %u, encryption_key_size %u",
289         it->flags, required_encryption_size, att_connection->authorized, att_connection->authenticated, att_connection->encryption_key_size);
290     if ((it->flags & ATT_PROPERTY_AUTHENTICATION_REQUIRED) && att_connection->authenticated == 0) {
291         return ATT_ERROR_INSUFFICIENT_AUTHENTICATION;
292     }
293     if ((it->flags & ATT_PROPERTY_AUTHORIZATION_REQUIRED) && att_connection->authorized == 0) {
294         return ATT_ERROR_INSUFFICIENT_AUTHORIZATION;
295     }
296     if (required_encryption_size > 0 && att_connection->encryption_key_size == 0){
297         return ATT_ERROR_INSUFFICIENT_ENCRYPTION;
298     }
299     if (required_encryption_size > att_connection->encryption_key_size){
300         return ATT_ERROR_INSUFFICIENT_ENCRYPTION_KEY_SIZE;
301     }
302     return 0;
303 }
304 
305 //
306 // MARK: ATT_EXCHANGE_MTU_REQUEST
307 //
308 static uint16_t handle_exchange_mtu_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
309                                          uint8_t * response_buffer){
310 
311     UNUSED(request_len);
312 
313     uint16_t client_rx_mtu = little_endian_read_16(request_buffer, 1);
314 
315     // find min(local max mtu, remote mtu) and use as mtu for this connection
316     if (client_rx_mtu < att_connection->max_mtu){
317         att_connection->mtu = client_rx_mtu;
318     } else {
319         att_connection->mtu = att_connection->max_mtu;
320     }
321 
322     response_buffer[0] = ATT_EXCHANGE_MTU_RESPONSE;
323     little_endian_store_16(response_buffer, 1, att_connection->mtu);
324     return 3;
325 }
326 
327 
328 //
329 // MARK: ATT_FIND_INFORMATION_REQUEST
330 //
331 // TODO: handle other types then GATT_PRIMARY_SERVICE_UUID and GATT_SECONDARY_SERVICE_UUID
332 //
333 static uint16_t handle_find_information_request2(att_connection_t * att_connection, uint8_t * response_buffer, uint16_t response_buffer_size,
334                                            uint16_t start_handle, uint16_t end_handle){
335 
336     UNUSED(att_connection);
337 
338     log_info("ATT_FIND_INFORMATION_REQUEST: from %04X to %04X", start_handle, end_handle);
339     uint8_t request_type = ATT_FIND_INFORMATION_REQUEST;
340 
341     if (start_handle > end_handle || start_handle == 0){
342         return setup_error_invalid_handle(response_buffer, request_type, start_handle);
343     }
344 
345     uint16_t offset   = 1;
346     uint16_t uuid_len = 0;
347 
348     att_iterator_t it;
349     att_iterator_init(&it);
350     while (att_iterator_has_next(&it)){
351         att_iterator_fetch_next(&it);
352         if (!it.handle) break;
353         if (it.handle > end_handle) break;
354         if (it.handle < start_handle) continue;
355 
356         // log_info("Handle 0x%04x", it.handle);
357 
358         uint16_t this_uuid_len = (it.flags & ATT_PROPERTY_UUID128) ? 16 : 2;
359 
360         // check if value has same len as last one if not first result
361         if (offset > 1){
362             if (this_uuid_len != uuid_len) {
363                 break;
364             }
365         }
366 
367         // first
368         if (offset == 1) {
369             uuid_len = this_uuid_len;
370             // set format field
371             response_buffer[offset] = (it.flags & ATT_PROPERTY_UUID128) ? 0x02 : 0x01;
372             offset++;
373         }
374 
375         // space?
376         if (offset + 2 + uuid_len > response_buffer_size) break;
377 
378         // store
379         little_endian_store_16(response_buffer, offset, it.handle);
380         offset += 2;
381 
382         memcpy(response_buffer + offset, it.uuid, uuid_len);
383         offset += uuid_len;
384     }
385 
386     if (offset == 1){
387         return setup_error_atribute_not_found(response_buffer, request_type, start_handle);
388     }
389 
390     response_buffer[0] = ATT_FIND_INFORMATION_REPLY;
391     return offset;
392 }
393 
394 static uint16_t handle_find_information_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
395                                          uint8_t * response_buffer, uint16_t response_buffer_size){
396     UNUSED(request_len);
397     return handle_find_information_request2(att_connection, response_buffer, response_buffer_size, little_endian_read_16(request_buffer, 1), little_endian_read_16(request_buffer, 3));
398 }
399 
400 //
401 // MARK: ATT_FIND_BY_TYPE_VALUE
402 //
403 // "Only attributes with attribute handles between and including the Starting Handle parameter
404 // and the Ending Handle parameter that match the requested attri- bute type and the attribute
405 // value that have sufficient permissions to allow reading will be returned" -> (1)
406 //
407 // TODO: handle other types then GATT_PRIMARY_SERVICE_UUID and GATT_SECONDARY_SERVICE_UUID
408 //
409 // NOTE: doesn't handle DYNAMIC values
410 // NOTE: only supports 16 bit UUIDs
411 //
412 static uint16_t handle_find_by_type_value_request2(att_connection_t * att_connection, uint8_t * response_buffer, uint16_t response_buffer_size,
413                                            uint16_t start_handle, uint16_t end_handle,
414                                            uint16_t attribute_type, uint16_t attribute_len, uint8_t* attribute_value){
415 
416     UNUSED(att_connection);
417 
418     log_info("ATT_FIND_BY_TYPE_VALUE_REQUEST: from %04X to %04X, type %04X, value: ", start_handle, end_handle, attribute_type);
419     log_info_hexdump(attribute_value, attribute_len);
420     uint8_t request_type = ATT_FIND_BY_TYPE_VALUE_REQUEST;
421 
422     if (start_handle > end_handle || start_handle == 0){
423         return setup_error_invalid_handle(response_buffer, request_type, start_handle);
424     }
425 
426     uint16_t offset      = 1;
427     uint16_t in_group    = 0;
428     uint16_t prev_handle = 0;
429 
430     att_iterator_t it;
431     att_iterator_init(&it);
432     while (att_iterator_has_next(&it)){
433         att_iterator_fetch_next(&it);
434 
435         if (it.handle && it.handle < start_handle) continue;
436         if (it.handle > end_handle) break;  // (1)
437 
438         // close current tag, if within a group and a new service definition starts or we reach end of att db
439         if (in_group &&
440             (it.handle == 0 || att_iterator_match_uuid16(&it, GATT_PRIMARY_SERVICE_UUID) || att_iterator_match_uuid16(&it, GATT_SECONDARY_SERVICE_UUID))){
441 
442             log_info("End of group, handle 0x%04x", prev_handle);
443             little_endian_store_16(response_buffer, offset, prev_handle);
444             offset += 2;
445             in_group = 0;
446 
447             // check if space for another handle pair available
448             if (offset + 4 > response_buffer_size){
449                 break;
450             }
451         }
452 
453         // keep track of previous handle
454         prev_handle = it.handle;
455 
456         // does current attribute match
457         if (it.handle && att_iterator_match_uuid16(&it, attribute_type) && attribute_len == it.value_len && memcmp(attribute_value, it.value, it.value_len) == 0){
458             log_info("Begin of group, handle 0x%04x", it.handle);
459             little_endian_store_16(response_buffer, offset, it.handle);
460             offset += 2;
461             in_group = 1;
462         }
463     }
464 
465     if (offset == 1){
466         return setup_error_atribute_not_found(response_buffer, request_type, start_handle);
467     }
468 
469     response_buffer[0] = ATT_FIND_BY_TYPE_VALUE_RESPONSE;
470     return offset;
471 }
472 
473 static uint16_t handle_find_by_type_value_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
474                                            uint8_t * response_buffer, uint16_t response_buffer_size){
475     int attribute_len = request_len - 7;
476     return handle_find_by_type_value_request2(att_connection, response_buffer, response_buffer_size, little_endian_read_16(request_buffer, 1),
477                                               little_endian_read_16(request_buffer, 3), little_endian_read_16(request_buffer, 5), attribute_len, &request_buffer[7]);
478 }
479 
480 //
481 // MARK: ATT_READ_BY_TYPE_REQUEST
482 //
483 static uint16_t handle_read_by_type_request2(att_connection_t * att_connection, uint8_t * response_buffer, uint16_t response_buffer_size,
484                                       uint16_t start_handle, uint16_t end_handle,
485                                       uint16_t attribute_type_len, uint8_t * attribute_type){
486 
487     log_info("ATT_READ_BY_TYPE_REQUEST: from %04X to %04X, type: ", start_handle, end_handle);
488     log_info_hexdump(attribute_type, attribute_type_len);
489     uint8_t request_type = ATT_READ_BY_TYPE_REQUEST;
490 
491     if (start_handle > end_handle || start_handle == 0){
492         return setup_error_invalid_handle(response_buffer, request_type, start_handle);
493     }
494 
495     uint16_t offset   = 1;
496     uint16_t pair_len = 0;
497 
498     att_iterator_t it;
499     att_iterator_init(&it);
500     uint8_t error_code = 0;
501     uint16_t first_matching_but_unreadable_handle = 0;
502 
503 #ifdef ENABLE_ATT_DELAYED_READ_RESPONSE
504     int read_request_pending = 0;
505 #endif
506 
507     while (att_iterator_has_next(&it)){
508         att_iterator_fetch_next(&it);
509 
510         if (!it.handle) break;
511         if (it.handle < start_handle) continue;
512         if (it.handle > end_handle) break;  // (1)
513 
514         // does current attribute match
515         if (!att_iterator_match_uuid(&it, attribute_type, attribute_type_len)) continue;
516 
517         // skip handles that cannot be read but rembember that there has been at least one
518         if ((it.flags & ATT_PROPERTY_READ) == 0) {
519             if (first_matching_but_unreadable_handle == 0) {
520                 first_matching_but_unreadable_handle = it.handle;
521             }
522             continue;
523         }
524 
525         // check security requirements
526         if ((it.flags & ATT_DB_FLAGS_READ_WITHOUT_AUTHENTICATION) == 0){
527             error_code = att_validate_security(att_connection, ATT_READ, &it);
528             if (error_code) break;
529         }
530 
531         att_update_value_len(&it, att_connection->con_handle);
532 
533 #ifdef ENABLE_ATT_DELAYED_READ_RESPONSE
534         if (it.value_len == ATT_READ_RESPONSE_PENDING){
535             read_request_pending = 1;
536         }
537         if (read_request_pending) continue;
538 #endif
539 
540         // check if value has same len as last one
541         uint16_t this_pair_len = 2 + it.value_len;
542         if (offset > 1){
543             if (pair_len != this_pair_len) {
544                 break;
545             }
546         }
547 
548         // first
549         if (offset == 1) {
550             pair_len = this_pair_len;
551             response_buffer[offset] = pair_len;
552             offset++;
553         }
554 
555         // space?
556         if (offset + pair_len > response_buffer_size) {
557             if (offset > 2) break;
558             it.value_len = response_buffer_size - 4;
559             response_buffer[1] = 2 + it.value_len;
560         }
561 
562         // store
563         little_endian_store_16(response_buffer, offset, it.handle);
564         offset += 2;
565         uint16_t bytes_copied = att_copy_value(&it, 0, response_buffer + offset, it.value_len, att_connection->con_handle);
566         offset += bytes_copied;
567     }
568 
569 #ifdef ENABLE_ATT_DELAYED_READ_RESPONSE
570     if (read_request_pending) return ATT_READ_RESPONSE_PENDING;
571 #endif
572 
573     // at least one attribute could be read
574     if (offset > 1){
575         response_buffer[0] = ATT_READ_BY_TYPE_RESPONSE;
576         return offset;
577     }
578 
579     // first attribute had an error
580     if (error_code){
581         return setup_error(response_buffer, request_type, start_handle, error_code);
582     }
583 
584     // no other errors, but all found attributes had been non-readable
585     if (first_matching_but_unreadable_handle){
586         return setup_error_read_not_permitted(response_buffer, request_type, first_matching_but_unreadable_handle);
587     }
588 
589     // attribute not found
590     return setup_error_atribute_not_found(response_buffer, request_type, start_handle);
591 }
592 
593 static uint16_t handle_read_by_type_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
594                                      uint8_t * response_buffer, uint16_t response_buffer_size){
595     int attribute_type_len;
596     if (request_len <= 7){
597         attribute_type_len = 2;
598     } else {
599         attribute_type_len = 16;
600     }
601     return handle_read_by_type_request2(att_connection, response_buffer, response_buffer_size, little_endian_read_16(request_buffer, 1), little_endian_read_16(request_buffer, 3), attribute_type_len, &request_buffer[5]);
602 }
603 
604 //
605 // MARK: ATT_READ_BY_TYPE_REQUEST
606 //
607 static uint16_t handle_read_request2(att_connection_t * att_connection, uint8_t * response_buffer, uint16_t response_buffer_size, uint16_t handle){
608 
609     log_info("ATT_READ_REQUEST: handle %04x", handle);
610     uint8_t request_type = ATT_READ_REQUEST;
611 
612     att_iterator_t it;
613     int ok = att_find_handle(&it, handle);
614     if (!ok){
615         return setup_error_invalid_handle(response_buffer, request_type, handle);
616     }
617 
618     // check if handle can be read
619     if ((it.flags & ATT_PROPERTY_READ) == 0) {
620         return setup_error_read_not_permitted(response_buffer, request_type, handle);
621     }
622 
623     // check security requirements
624     if ((it.flags & ATT_DB_FLAGS_READ_WITHOUT_AUTHENTICATION) == 0){
625         uint8_t error_code = att_validate_security(att_connection, ATT_READ, &it);
626         if (error_code) {
627             return setup_error(response_buffer, request_type, handle, error_code);
628         }
629     }
630 
631     att_update_value_len(&it, att_connection->con_handle);
632 
633 #ifdef ENABLE_ATT_DELAYED_READ_RESPONSE
634     if (it.value_len == ATT_READ_RESPONSE_PENDING) return ATT_READ_RESPONSE_PENDING;
635 #endif
636 
637     uint16_t offset   = 1;
638     // limit data
639     if (offset + it.value_len > response_buffer_size) {
640         it.value_len = response_buffer_size - 1;
641     }
642 
643     // store
644     uint16_t bytes_copied = att_copy_value(&it, 0, response_buffer + offset, it.value_len, att_connection->con_handle);
645     offset += bytes_copied;
646 
647     response_buffer[0] = ATT_READ_RESPONSE;
648     return offset;
649 }
650 
651 static uint16_t handle_read_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
652                              uint8_t * response_buffer, uint16_t response_buffer_size){
653     UNUSED(request_len);
654     return handle_read_request2(att_connection, response_buffer, response_buffer_size, little_endian_read_16(request_buffer, 1));
655 }
656 
657 //
658 // MARK: ATT_READ_BLOB_REQUEST 0x0c
659 //
660 static uint16_t handle_read_blob_request2(att_connection_t * att_connection, uint8_t * response_buffer, uint16_t response_buffer_size, uint16_t handle, uint16_t value_offset){
661     log_info("ATT_READ_BLOB_REQUEST: handle %04x, offset %u", handle, value_offset);
662     uint8_t request_type = ATT_READ_BLOB_REQUEST;
663 
664     att_iterator_t it;
665     int ok = att_find_handle(&it, handle);
666     if (!ok){
667         return setup_error_invalid_handle(response_buffer, request_type, handle);
668     }
669 
670     // check if handle can be read
671     if ((it.flags & ATT_PROPERTY_READ) == 0) {
672         return setup_error_read_not_permitted(response_buffer, request_type, handle);
673     }
674 
675     // check security requirements
676     if ((it.flags & ATT_DB_FLAGS_READ_WITHOUT_AUTHENTICATION) == 0){
677         uint8_t error_code = att_validate_security(att_connection, ATT_READ, &it);
678         if (error_code) {
679             return setup_error(response_buffer, request_type, handle, error_code);
680         }
681     }
682 
683     att_update_value_len(&it, att_connection->con_handle);
684 
685 #ifdef ENABLE_ATT_DELAYED_READ_RESPONSE
686     if (it.value_len == ATT_READ_RESPONSE_PENDING) return ATT_READ_RESPONSE_PENDING;
687 #endif
688 
689     if (value_offset > it.value_len){
690         return setup_error_invalid_offset(response_buffer, request_type, handle);
691     }
692 
693     // limit data
694     uint16_t offset   = 1;
695     if (offset + it.value_len - value_offset > response_buffer_size) {
696         it.value_len = response_buffer_size - 1 + value_offset;
697     }
698 
699     // store
700     uint16_t bytes_copied = att_copy_value(&it, value_offset, response_buffer + offset, it.value_len - value_offset, att_connection->con_handle);
701     offset += bytes_copied;
702 
703     response_buffer[0] = ATT_READ_BLOB_RESPONSE;
704     return offset;
705 }
706 
707 static uint16_t handle_read_blob_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
708                                   uint8_t * response_buffer, uint16_t response_buffer_size){
709     UNUSED(request_len);
710     return handle_read_blob_request2(att_connection, response_buffer, response_buffer_size, little_endian_read_16(request_buffer, 1), little_endian_read_16(request_buffer, 3));
711 }
712 
713 //
714 // MARK: ATT_READ_MULTIPLE_REQUEST 0x0e
715 //
716 static uint16_t handle_read_multiple_request2(att_connection_t * att_connection, uint8_t * response_buffer, uint16_t response_buffer_size, uint16_t num_handles, uint8_t * handles){
717     log_info("ATT_READ_MULTIPLE_REQUEST: num handles %u", num_handles);
718     uint8_t request_type = ATT_READ_MULTIPLE_REQUEST;
719 
720     // TODO: figure out which error to respond with
721     // if (num_handles < 2){
722     //     return setup_error(response_buffer, ATT_READ_MULTIPLE_REQUEST, handle, ???);
723     // }
724 
725     uint16_t offset   = 1;
726 
727     int i;
728     uint8_t error_code = 0;
729     uint16_t handle = 0;
730 
731 #ifdef ENABLE_ATT_DELAYED_READ_RESPONSE
732     int read_request_pending = 0;
733 #endif
734 
735     for (i=0;i<num_handles;i++){
736         handle = little_endian_read_16(handles, i << 1);
737 
738         if (handle == 0){
739             return setup_error_invalid_handle(response_buffer, request_type, handle);
740         }
741 
742         att_iterator_t it;
743 
744         int ok = att_find_handle(&it, handle);
745         if (!ok){
746             return setup_error_invalid_handle(response_buffer, request_type, handle);
747         }
748 
749         // check if handle can be read
750         if ((it.flags & ATT_PROPERTY_READ) == 0) {
751             error_code = ATT_ERROR_READ_NOT_PERMITTED;
752             break;
753         }
754 
755         // check security requirements
756         if ((it.flags & ATT_DB_FLAGS_READ_WITHOUT_AUTHENTICATION) == 0){
757             error_code = att_validate_security(att_connection, ATT_READ, &it);
758             if (error_code) break;
759         }
760         att_update_value_len(&it, att_connection->con_handle);
761 
762 #ifdef ENABLE_ATT_DELAYED_READ_RESPONSE
763         if (it.value_len == ATT_READ_RESPONSE_PENDING) {
764             read_request_pending = 1;
765         }
766         if (read_request_pending) continue;
767 #endif
768 
769         // limit data
770         if (offset + it.value_len > response_buffer_size) {
771             it.value_len = response_buffer_size - 1;
772         }
773 
774         // store
775         uint16_t bytes_copied = att_copy_value(&it, 0, response_buffer + offset, it.value_len, att_connection->con_handle);
776         offset += bytes_copied;
777     }
778 
779     if (error_code){
780         return setup_error(response_buffer, request_type, handle, error_code);
781     }
782 
783     response_buffer[0] = ATT_READ_MULTIPLE_RESPONSE;
784     return offset;
785 }
786 static uint16_t handle_read_multiple_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
787                                       uint8_t * response_buffer, uint16_t response_buffer_size){
788     int num_handles = (request_len - 1) >> 1;
789     return handle_read_multiple_request2(att_connection, response_buffer, response_buffer_size, num_handles, &request_buffer[1]);
790 }
791 
792 //
793 // MARK: ATT_READ_BY_GROUP_TYPE_REQUEST 0x10
794 //
795 // Only handles GATT_PRIMARY_SERVICE_UUID and GATT_SECONDARY_SERVICE_UUID
796 // Core v4.0, vol 3, part g, 2.5.3
797 // "The «Primary Service» and «Secondary Service» grouping types may be used in the Read By Group Type Request.
798 //  The «Characteristic» grouping type shall not be used in the ATT Read By Group Type Request."
799 //
800 // NOTE: doesn't handle DYNAMIC values
801 //
802 // NOTE: we don't check for security as PRIMARY and SECONDAY SERVICE definition shouldn't be protected
803 // Core 4.0, vol 3, part g, 8.1
804 // "The list of services and characteristics that a device supports is not considered private or
805 //  confidential information, and therefore the Service and Characteristic Discovery procedures
806 //  shall always be permitted. "
807 //
808 static uint16_t handle_read_by_group_type_request2(att_connection_t * att_connection, uint8_t * response_buffer, uint16_t response_buffer_size,
809                                             uint16_t start_handle, uint16_t end_handle,
810                                             uint16_t attribute_type_len, uint8_t * attribute_type){
811 
812     UNUSED(att_connection);
813 
814     log_info("ATT_READ_BY_GROUP_TYPE_REQUEST: from %04X to %04X, buffer size %u, type: ", start_handle, end_handle, response_buffer_size);
815     log_info_hexdump(attribute_type, attribute_type_len);
816     uint8_t request_type = ATT_READ_BY_GROUP_TYPE_REQUEST;
817 
818     if (start_handle > end_handle || start_handle == 0){
819         return setup_error_invalid_handle(response_buffer, request_type, start_handle);
820     }
821 
822     // assert UUID is primary or secondary service uuid
823     uint16_t uuid16 = uuid16_from_uuid(attribute_type_len, attribute_type);
824     if (uuid16 != GATT_PRIMARY_SERVICE_UUID && uuid16 != GATT_SECONDARY_SERVICE_UUID){
825         return setup_error(response_buffer, request_type, start_handle, ATT_ERROR_UNSUPPORTED_GROUP_TYPE);
826     }
827 
828     uint16_t offset   = 1;
829     uint16_t pair_len = 0;
830     uint16_t in_group = 0;
831     uint16_t group_start_handle = 0;
832     uint8_t const * group_start_value = NULL;
833     uint16_t prev_handle = 0;
834 
835     att_iterator_t it;
836     att_iterator_init(&it);
837     while (att_iterator_has_next(&it)){
838         att_iterator_fetch_next(&it);
839 
840         if (it.handle && it.handle < start_handle) continue;
841         if (it.handle > end_handle) break;  // (1)
842 
843         // log_info("Handle 0x%04x", it.handle);
844 
845         // close current tag, if within a group and a new service definition starts or we reach end of att db
846         if (in_group &&
847             (it.handle == 0 || att_iterator_match_uuid16(&it, GATT_PRIMARY_SERVICE_UUID) || att_iterator_match_uuid16(&it, GATT_SECONDARY_SERVICE_UUID))){
848             // log_info("End of group, handle 0x%04x, val_len: %u", prev_handle, pair_len - 4);
849 
850             little_endian_store_16(response_buffer, offset, group_start_handle);
851             offset += 2;
852             little_endian_store_16(response_buffer, offset, prev_handle);
853             offset += 2;
854             memcpy(response_buffer + offset, group_start_value, pair_len - 4);
855             offset += pair_len - 4;
856             in_group = 0;
857 
858             // check if space for another handle pair available
859             if (offset + pair_len > response_buffer_size){
860                 break;
861             }
862         }
863 
864         // keep track of previous handle
865         prev_handle = it.handle;
866 
867         // does current attribute match
868         // log_info("compare: %04x == %04x", *(uint16_t*) context->attribute_type, *(uint16_t*) uuid);
869         if (it.handle && att_iterator_match_uuid(&it, attribute_type, attribute_type_len)) {
870 
871             // check if value has same len as last one
872             uint16_t this_pair_len = 4 + it.value_len;
873             if (offset > 1){
874                 if (this_pair_len != pair_len) {
875                     break;
876                 }
877             }
878 
879             // log_info("Begin of group, handle 0x%04x", it.handle);
880 
881             // first
882             if (offset == 1) {
883                 pair_len = this_pair_len;
884                 response_buffer[offset] = this_pair_len;
885                 offset++;
886             }
887 
888             group_start_handle = it.handle;
889             group_start_value  = it.value;
890             in_group = 1;
891         }
892     }
893 
894     if (offset == 1){
895         return setup_error_atribute_not_found(response_buffer, request_type, start_handle);
896     }
897 
898     response_buffer[0] = ATT_READ_BY_GROUP_TYPE_RESPONSE;
899     return offset;
900 }
901 static uint16_t handle_read_by_group_type_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
902                                            uint8_t * response_buffer, uint16_t response_buffer_size){
903     int attribute_type_len;
904     if (request_len <= 7){
905         attribute_type_len = 2;
906     } else {
907         attribute_type_len = 16;
908     }
909     return handle_read_by_group_type_request2(att_connection, response_buffer, response_buffer_size, little_endian_read_16(request_buffer, 1), little_endian_read_16(request_buffer, 3), attribute_type_len, &request_buffer[5]);
910 }
911 
912 //
913 // MARK: ATT_WRITE_REQUEST 0x12
914 static uint16_t handle_write_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
915                               uint8_t * response_buffer, uint16_t response_buffer_size){
916 
917     UNUSED(response_buffer_size);
918 
919     uint8_t request_type = ATT_WRITE_REQUEST;
920 
921     uint16_t handle = little_endian_read_16(request_buffer, 1);
922     att_iterator_t it;
923     int ok = att_find_handle(&it, handle);
924     if (!ok) {
925         return setup_error_invalid_handle(response_buffer, request_type, handle);
926     }
927     if (!att_write_callback) {
928         return setup_error_write_not_permitted(response_buffer, request_type, handle);
929     }
930     if ((it.flags & ATT_PROPERTY_WRITE) == 0) {
931         return setup_error_write_not_permitted(response_buffer, request_type, handle);
932     }
933     if ((it.flags & ATT_PROPERTY_DYNAMIC) == 0) {
934         return setup_error_write_not_permitted(response_buffer, request_type, handle);
935     }
936     // check security requirements
937     uint8_t error_code = att_validate_security(att_connection, ATT_WRITE, &it);
938     if (error_code) {
939         return setup_error(response_buffer, request_type, handle, error_code);
940     }
941     att_persistent_ccc_cache(&it);
942     error_code = (*att_write_callback)(att_connection->con_handle, handle, ATT_TRANSACTION_MODE_NONE, 0, request_buffer + 3, request_len - 3);
943     if (error_code) {
944         return setup_error(response_buffer, request_type, handle, error_code);
945     }
946     response_buffer[0] = ATT_WRITE_RESPONSE;
947     return 1;
948 }
949 
950 //
951 // MARK: ATT_PREPARE_WRITE_REQUEST 0x16
952 static uint16_t handle_prepare_write_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
953                                       uint8_t * response_buffer, uint16_t response_buffer_size){
954 
955     UNUSED(response_buffer_size);
956 
957     uint8_t request_type = ATT_PREPARE_WRITE_REQUEST;
958 
959     uint16_t handle = little_endian_read_16(request_buffer, 1);
960     uint16_t offset = little_endian_read_16(request_buffer, 3);
961     if (!att_write_callback) {
962         return setup_error_write_not_permitted(response_buffer, request_type, handle);
963     }
964     att_iterator_t it;
965     int ok = att_find_handle(&it, handle);
966     if (!ok) {
967         return setup_error_invalid_handle(response_buffer, request_type, handle);
968     }
969     if ((it.flags & ATT_PROPERTY_WRITE) == 0) {
970         return setup_error_write_not_permitted(response_buffer, request_type, handle);
971     }
972     if ((it.flags & ATT_PROPERTY_DYNAMIC) == 0) {
973         return setup_error_write_not_permitted(response_buffer, request_type, handle);
974     }
975     // check security requirements
976     uint8_t error_code = att_validate_security(att_connection, ATT_WRITE, &it);
977     if (error_code) {
978         return setup_error(response_buffer, request_type, handle, error_code);
979     }
980 
981     error_code = (*att_write_callback)(att_connection->con_handle, handle, ATT_TRANSACTION_MODE_ACTIVE, offset, request_buffer + 5, request_len - 5);
982     switch (error_code){
983         case 0:
984             break;
985         case ATT_ERROR_INVALID_OFFSET:
986         case ATT_ERROR_INVALID_ATTRIBUTE_VALUE_LENGTH:
987             // postpone to execute write request
988             att_prepare_write_update_errors(error_code, handle);
989             break;
990         default:
991             return setup_error(response_buffer, request_type, handle, error_code);
992     }
993 
994     // response: echo request
995     memcpy(response_buffer, request_buffer, request_len);
996     response_buffer[0] = ATT_PREPARE_WRITE_RESPONSE;
997     return request_len;
998 }
999 
1000 /*
1001  * @brief transcation queue of prepared writes, e.g., after disconnect
1002  */
1003 void att_clear_transaction_queue(att_connection_t * att_connection){
1004     (*att_write_callback)(att_connection->con_handle, 0, ATT_TRANSACTION_MODE_CANCEL, 0, NULL, 0);
1005 }
1006 
1007 // MARK: ATT_EXECUTE_WRITE_REQUEST 0x18
1008 // NOTE: security has been verified by handle_prepare_write_request
1009 static uint16_t handle_execute_write_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
1010                                       uint8_t * response_buffer, uint16_t response_buffer_size){
1011 
1012     UNUSED(request_len);
1013     UNUSED(response_buffer_size);
1014 
1015     uint8_t request_type = ATT_EXECUTE_WRITE_REQUEST;
1016     if (request_buffer[1]) {
1017         // validate queued write
1018         if (att_prepare_write_error_code == 0){
1019             att_prepare_write_error_code = (*att_write_callback)(att_connection->con_handle, 0, ATT_TRANSACTION_MODE_VALIDATE, 0, NULL, 0);
1020         }
1021         // deliver queued errors
1022         if (att_prepare_write_error_code){
1023             att_clear_transaction_queue(att_connection);
1024             uint8_t  error_code = att_prepare_write_error_code;
1025             uint16_t handle     = att_prepare_write_error_handle;
1026             att_prepare_write_reset();
1027             return setup_error(response_buffer, request_type, handle, error_code);
1028         }
1029         att_write_callback(att_connection->con_handle, 0, ATT_TRANSACTION_MODE_EXECUTE, 0, NULL, 0);
1030     } else {
1031         att_clear_transaction_queue(att_connection);
1032     }
1033     response_buffer[0] = ATT_EXECUTE_WRITE_RESPONSE;
1034     return 1;
1035 }
1036 
1037 // MARK: ATT_WRITE_COMMAND 0x52
1038 // Core 4.0, vol 3, part F, 3.4.5.3
1039 // "No Error Response or Write Response shall be sent in response to this command"
1040 static void handle_write_command(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
1041                                            uint8_t * response_buffer, uint16_t response_buffer_size){
1042 
1043     UNUSED(response_buffer);
1044     UNUSED(response_buffer_size);
1045 
1046     uint16_t handle = little_endian_read_16(request_buffer, 1);
1047     if (!att_write_callback) return;
1048 
1049     att_iterator_t it;
1050     int ok = att_find_handle(&it, handle);
1051     if (!ok) return;
1052     if ((it.flags & ATT_PROPERTY_DYNAMIC) == 0) return;
1053     if ((it.flags & ATT_PROPERTY_WRITE_WITHOUT_RESPONSE) == 0) return;
1054     if (att_validate_security(att_connection, ATT_WRITE, &it)) return;
1055     att_persistent_ccc_cache(&it);
1056     (*att_write_callback)(att_connection->con_handle, handle, ATT_TRANSACTION_MODE_NONE, 0, request_buffer + 3, request_len - 3);
1057 }
1058 
1059 // MARK: helper for ATT_HANDLE_VALUE_NOTIFICATION and ATT_HANDLE_VALUE_INDICATION
1060 static uint16_t prepare_handle_value(att_connection_t * att_connection,
1061                                      uint16_t handle,
1062                                      uint8_t *value,
1063                                      uint16_t value_len,
1064                                      uint8_t * response_buffer){
1065     little_endian_store_16(response_buffer, 1, handle);
1066     if (value_len > att_connection->mtu - 3){
1067         value_len = att_connection->mtu - 3;
1068     }
1069     memcpy(&response_buffer[3], value, value_len);
1070     return value_len + 3;
1071 }
1072 
1073 // MARK: ATT_HANDLE_VALUE_NOTIFICATION 0x1b
1074 uint16_t att_prepare_handle_value_notification(att_connection_t * att_connection,
1075                                                uint16_t handle,
1076                                                uint8_t *value,
1077                                                uint16_t value_len,
1078                                                uint8_t * response_buffer){
1079 
1080     response_buffer[0] = ATT_HANDLE_VALUE_NOTIFICATION;
1081     return prepare_handle_value(att_connection, handle, value, value_len, response_buffer);
1082 }
1083 
1084 // MARK: ATT_HANDLE_VALUE_INDICATION 0x1d
1085 uint16_t att_prepare_handle_value_indication(att_connection_t * att_connection,
1086                                              uint16_t handle,
1087                                              uint8_t *value,
1088                                              uint16_t value_len,
1089                                              uint8_t * response_buffer){
1090 
1091     response_buffer[0] = ATT_HANDLE_VALUE_INDICATION;
1092     return prepare_handle_value(att_connection, handle, value, value_len, response_buffer);
1093 }
1094 
1095 // MARK: Dispatcher
1096 uint16_t att_handle_request(att_connection_t * att_connection,
1097                             uint8_t * request_buffer,
1098                             uint16_t request_len,
1099                             uint8_t * response_buffer){
1100     uint16_t response_len = 0;
1101     uint16_t response_buffer_size = att_connection->mtu;
1102 
1103     switch (request_buffer[0]){
1104         case ATT_EXCHANGE_MTU_REQUEST:
1105             response_len = handle_exchange_mtu_request(att_connection, request_buffer, request_len, response_buffer);
1106             break;
1107         case ATT_FIND_INFORMATION_REQUEST:
1108             response_len = handle_find_information_request(att_connection, request_buffer, request_len,response_buffer, response_buffer_size);
1109             break;
1110         case ATT_FIND_BY_TYPE_VALUE_REQUEST:
1111             response_len = handle_find_by_type_value_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1112             break;
1113         case ATT_READ_BY_TYPE_REQUEST:
1114             response_len = handle_read_by_type_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1115             break;
1116         case ATT_READ_REQUEST:
1117             response_len = handle_read_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1118             break;
1119         case ATT_READ_BLOB_REQUEST:
1120             response_len = handle_read_blob_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1121             break;
1122         case ATT_READ_MULTIPLE_REQUEST:
1123             response_len = handle_read_multiple_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1124             break;
1125         case ATT_READ_BY_GROUP_TYPE_REQUEST:
1126             response_len = handle_read_by_group_type_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1127             break;
1128         case ATT_WRITE_REQUEST:
1129             response_len = handle_write_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1130             break;
1131         case ATT_PREPARE_WRITE_REQUEST:
1132             response_len = handle_prepare_write_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1133             break;
1134         case ATT_EXECUTE_WRITE_REQUEST:
1135             response_len = handle_execute_write_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1136             break;
1137         case ATT_WRITE_COMMAND:
1138             handle_write_command(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1139             break;
1140 #ifdef ENABLE_LE_SIGNED_WRITE
1141         case ATT_SIGNED_WRITE_COMMAND:
1142             log_info("handle_signed_write_command preprocessed by att_server.c");
1143             break;
1144 #endif
1145         default:
1146             log_info("Unhandled ATT Command: %02X, DATA: ", request_buffer[0]);
1147             log_info_hexdump(&request_buffer[9], request_len-9);
1148             break;
1149     }
1150     return response_len;
1151 }
1152 
1153 // returns 1 if service found. only primary service.
1154 int gatt_server_get_get_handle_range_for_service_with_uuid16(uint16_t uuid16, uint16_t * start_handle, uint16_t * end_handle){
1155     uint16_t in_group    = 0;
1156     uint16_t prev_handle = 0;
1157 
1158     uint8_t attribute_value[2];
1159     int attribute_len = sizeof(attribute_value);
1160     little_endian_store_16(attribute_value, 0, uuid16);
1161 
1162     att_iterator_t it;
1163     att_iterator_init(&it);
1164     while (att_iterator_has_next(&it)){
1165         att_iterator_fetch_next(&it);
1166         int new_service_started = att_iterator_match_uuid16(&it, GATT_PRIMARY_SERVICE_UUID) || att_iterator_match_uuid16(&it, GATT_SECONDARY_SERVICE_UUID);
1167 
1168         // close current tag, if within a group and a new service definition starts or we reach end of att db
1169         if (in_group &&
1170             (it.handle == 0 || new_service_started)){
1171             *end_handle = prev_handle;
1172             return 1;
1173         }
1174 
1175         // keep track of previous handle
1176         prev_handle = it.handle;
1177 
1178         // check if found
1179         if (it.handle && new_service_started && attribute_len == it.value_len && memcmp(attribute_value, it.value, it.value_len) == 0){
1180             *start_handle = it.handle;
1181             in_group = 1;
1182         }
1183     }
1184     return 0;
1185 }
1186 
1187 // returns 0 if not found
1188 uint16_t gatt_server_get_value_handle_for_characteristic_with_uuid16(uint16_t start_handle, uint16_t end_handle, uint16_t uuid16){
1189     att_iterator_t it;
1190     att_iterator_init(&it);
1191     while (att_iterator_has_next(&it)){
1192         att_iterator_fetch_next(&it);
1193         if (it.handle && it.handle < start_handle) continue;
1194         if (it.handle > end_handle) break;  // (1)
1195         if (it.handle == 0) break;
1196         if (att_iterator_match_uuid16(&it, uuid16)) return it.handle;
1197     }
1198     return 0;
1199 }
1200 
1201 // returns 0 if not found
1202 uint16_t gatt_server_get_client_configuration_handle_for_characteristic_with_uuid16(uint16_t start_handle, uint16_t end_handle, uint16_t uuid16){
1203     att_iterator_t it;
1204     att_iterator_init(&it);
1205     int characteristic_found = 0;
1206     while (att_iterator_has_next(&it)){
1207         att_iterator_fetch_next(&it);
1208         if (it.handle && it.handle < start_handle) continue;
1209         if (it.handle > end_handle) break;  // (1)
1210         if (it.handle == 0) break;
1211         if (att_iterator_match_uuid16(&it, uuid16)){
1212             characteristic_found = 1;
1213             continue;
1214         }
1215         if (att_iterator_match_uuid16(&it, GATT_PRIMARY_SERVICE_UUID)
1216          || att_iterator_match_uuid16(&it, GATT_SECONDARY_SERVICE_UUID)
1217          || att_iterator_match_uuid16(&it, GATT_CHARACTERISTICS_UUID)){
1218             if (characteristic_found) break;
1219             continue;
1220         }
1221         if (att_iterator_match_uuid16(&it, GATT_CLIENT_CHARACTERISTICS_CONFIGURATION)){
1222             return it.handle;
1223         }
1224     }
1225     return 0;
1226 }
1227 
1228 // 1-item cache to optimize query during write_callback
1229 static void att_persistent_ccc_cache(att_iterator_t * it){
1230     att_persistent_ccc_handle = it->handle;
1231     if (it->flags & ATT_PROPERTY_UUID128){
1232         att_persistent_ccc_uuid16 = 0;
1233     } else {
1234         att_persistent_ccc_uuid16 = little_endian_read_16(it->uuid, 0);
1235     }
1236 }
1237 
1238 int att_is_persistent_ccc(uint16_t handle){
1239     if (handle != att_persistent_ccc_handle){
1240         att_iterator_t it;
1241         int ok = att_find_handle(&it, handle);
1242         if (!ok) return 0;
1243         att_persistent_ccc_cache(&it);
1244     }
1245     return att_persistent_ccc_uuid16 == GATT_CLIENT_CHARACTERISTICS_CONFIGURATION;
1246 }
1247 
1248 // att_read_callback helpers
1249 uint16_t att_read_callback_handle_blob(const uint8_t * blob, uint16_t blob_size, uint16_t offset, uint8_t * buffer, uint16_t buffer_size){
1250     if (buffer){
1251         uint16_t bytes_to_copy = btstack_min(blob_size - offset, buffer_size);
1252         memcpy(buffer, &blob[offset], bytes_to_copy);
1253         return bytes_to_copy;
1254     } else {
1255         return blob_size;
1256     }
1257 }
1258 
1259 uint16_t att_read_callback_handle_little_endian_32(uint32_t value, uint16_t offset, uint8_t * buffer, uint16_t buffer_size){
1260     uint8_t value_buffer[4];
1261     little_endian_store_32(value_buffer, 0, value);
1262     return att_read_callback_handle_blob(value_buffer, sizeof(value_buffer), offset, buffer, buffer_size);
1263 }
1264 
1265 uint16_t att_read_callback_handle_little_endian_16(uint16_t value, uint16_t offset, uint8_t * buffer, uint16_t buffer_size){
1266     uint8_t value_buffer[2];
1267     little_endian_store_16(value_buffer, 0, value);
1268     return att_read_callback_handle_blob(value_buffer, sizeof(value_buffer), offset, buffer, buffer_size);
1269 }
1270 
1271 uint16_t att_read_callback_handle_byte(uint8_t value, uint16_t offset, uint8_t * buffer, uint16_t buffer_size){
1272     uint8_t value_buffer[1];
1273     value_buffer[0] = value;
1274     return att_read_callback_handle_blob(value_buffer, sizeof(value_buffer), offset, buffer, buffer_size);
1275 }
1276