xref: /btstack/src/ble/att_db.c (revision 3b9a211c6022a4d7d30c83db4a21110b27b84b95)
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 #include <string.h>
41 
42 #include "ble/att_db.h"
43 #include "ble/core.h"
44 #include "bluetooth.h"
45 #include "btstack_debug.h"
46 #include "btstack_util.h"
47 
48 // check for ENABLE_ATT_DELAYED_READ_RESPONSE -> ENABLE_ATT_DELAYED_RESPONSE,
49 #ifdef ENABLE_ATT_DELAYED_READ_RESPONSE
50     #error "ENABLE_ATT_DELAYED_READ_RESPONSE was replaced by ENABLE_ATT_DELAYED_RESPONSE. Please update btstack_config.h"
51 #endif
52 
53 typedef enum {
54     ATT_READ,
55     ATT_WRITE,
56 } att_operation_t;
57 
58 
59 static int is_Bluetooth_Base_UUID(uint8_t const *uuid){
60     // Bluetooth Base UUID 00000000-0000-1000-8000-00805F9B34FB in little endian
61     static const uint8_t bluetooth_base_uuid[] = { 0xfb, 0x34, 0x9b, 0x5f, 0x80, 0x00, 0x00, 0x80, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
62 
63     if (memcmp(&uuid[0],  &bluetooth_base_uuid[0], 12) != 0) return false;
64     if (memcmp(&uuid[14], &bluetooth_base_uuid[14], 2) != 0) return false;
65     return true;
66 
67 }
68 
69 static uint16_t uuid16_from_uuid(uint16_t uuid_len, uint8_t * uuid){
70     if (uuid_len == 2) return little_endian_read_16(uuid, 0);
71     if (!is_Bluetooth_Base_UUID(uuid)) return 0;
72     return little_endian_read_16(uuid, 12);
73 }
74 
75 // ATT Database
76 
77 // new java-style iterator
78 typedef struct att_iterator {
79     // private
80     uint8_t const * att_ptr;
81     // public
82     uint16_t size;
83     uint16_t flags;
84     uint16_t handle;
85     uint8_t  const * uuid;
86     uint16_t value_len;
87     uint8_t  const * value;
88 } att_iterator_t;
89 
90 static void att_persistent_ccc_cache(att_iterator_t * it);
91 
92 static uint8_t const * att_db = NULL;
93 static att_read_callback_t  att_read_callback  = NULL;
94 static att_write_callback_t att_write_callback = NULL;
95 static int      att_prepare_write_error_code   = 0;
96 static uint16_t att_prepare_write_error_handle = 0x0000;
97 
98 // single cache for att_is_persistent_ccc - stores flags before write callback
99 static uint16_t att_persistent_ccc_handle;
100 static uint16_t att_persistent_ccc_uuid16;
101 
102 static void att_iterator_init(att_iterator_t *it){
103     it->att_ptr = att_db;
104 }
105 
106 static bool att_iterator_has_next(att_iterator_t *it){
107     return it->att_ptr != NULL;
108 }
109 
110 static void att_iterator_fetch_next(att_iterator_t *it){
111     it->size   = little_endian_read_16(it->att_ptr, 0);
112     if (it->size == 0){
113         it->flags = 0;
114         it->handle = 0;
115         it->uuid = NULL;
116         it->value_len = 0;
117         it->value = NULL;
118         it->att_ptr = NULL;
119         return;
120     }
121     it->flags  = little_endian_read_16(it->att_ptr, 2);
122     it->handle = little_endian_read_16(it->att_ptr, 4);
123     it->uuid   = &it->att_ptr[6];
124     // handle 128 bit UUIDs
125     if ((it->flags & ATT_PROPERTY_UUID128) != 0){
126         it->value_len = it->size - 22;
127         it->value  = &it->att_ptr[22];
128     } else {
129         it->value_len = it->size - 8;
130         it->value  = &it->att_ptr[8];
131     }
132     // advance AFTER setting values
133     it->att_ptr += it->size;
134 }
135 
136 static int att_iterator_match_uuid16(att_iterator_t *it, uint16_t uuid){
137     if (it->handle == 0) return 0;
138     if (it->flags & ATT_PROPERTY_UUID128){
139         if (!is_Bluetooth_Base_UUID(it->uuid)) return 0;
140         return little_endian_read_16(it->uuid, 12) == uuid;
141     }
142     return little_endian_read_16(it->uuid, 0)  == uuid;
143 }
144 
145 static int att_iterator_match_uuid(att_iterator_t *it, uint8_t *uuid, uint16_t uuid_len){
146     if (it->handle == 0) return 0;
147     // input: UUID16
148     if (uuid_len == 2) {
149         return att_iterator_match_uuid16(it, little_endian_read_16(uuid, 0));
150     }
151     // input and db: UUID128
152     if ((it->flags & ATT_PROPERTY_UUID128) != 0){
153         return memcmp(it->uuid, uuid, 16) == 0;
154     }
155     // input: UUID128, db: UUID16
156     if (!is_Bluetooth_Base_UUID(uuid)) return 0;
157     return little_endian_read_16(uuid, 12) == little_endian_read_16(it->uuid, 0);
158 }
159 
160 
161 static int att_find_handle(att_iterator_t *it, uint16_t handle){
162     if (handle == 0) return 0;
163     att_iterator_init(it);
164     while (att_iterator_has_next(it)){
165         att_iterator_fetch_next(it);
166         if (it->handle != handle) continue;
167         return 1;
168     }
169     return 0;
170 }
171 
172 // experimental client API
173 uint16_t att_uuid_for_handle(uint16_t attribute_handle){
174     att_iterator_t it;
175     int ok = att_find_handle(&it, attribute_handle);
176     if (!ok) return 0;
177     if ((it.flags & ATT_PROPERTY_UUID128) != 0) return 0;
178     return little_endian_read_16(it.uuid, 0);
179 }
180 // end of client API
181 
182 static void att_update_value_len(att_iterator_t *it, hci_con_handle_t con_handle){
183     if ((it->flags & ATT_PROPERTY_DYNAMIC) == 0) return;
184     it->value_len = (*att_read_callback)(con_handle, it->handle, 0, NULL, 0);
185     return;
186 }
187 
188 // copy attribute value from offset into buffer with given size
189 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){
190 
191     // DYNAMIC
192     if ((it->flags & ATT_PROPERTY_DYNAMIC) != 0){
193         return (*att_read_callback)(con_handle, it->handle, offset, buffer, buffer_size);
194     }
195 
196     // STATIC
197     uint16_t bytes_to_copy = it->value_len - offset;
198     if (bytes_to_copy > buffer_size){
199         bytes_to_copy = buffer_size;
200     }
201     (void)memcpy(buffer, it->value, bytes_to_copy);
202     return bytes_to_copy;
203 }
204 
205 void att_set_db(uint8_t const * db){
206     // validate db version
207     if (db == NULL) return;
208     if (*db++ != ATT_DB_VERSION){
209         log_error("ATT DB version differs, please regenerate .h from .gatt file or update att_db_util.c");
210         return;
211     }
212     att_db = db;
213 }
214 
215 void att_set_read_callback(att_read_callback_t callback){
216     att_read_callback = callback;
217 }
218 
219 void att_set_write_callback(att_write_callback_t callback){
220     att_write_callback = callback;
221 }
222 
223 void att_dump_attributes(void){
224     att_iterator_t it;
225     att_iterator_init(&it);
226     uint8_t uuid128[16];
227     while (att_iterator_has_next(&it)){
228         att_iterator_fetch_next(&it);
229         if (it.handle == 0) {
230             log_info("Handle: END");
231             return;
232         }
233         log_info("Handle: 0x%04x, flags: 0x%04x, uuid: ", it.handle, it.flags);
234         if ((it.flags & ATT_PROPERTY_UUID128) != 0){
235             reverse_128(it.uuid, uuid128);
236             log_info("%s", uuid128_to_str(uuid128));
237         } else {
238             log_info("%04x", little_endian_read_16(it.uuid, 0));
239         }
240         log_info(", value_len: %u, value: ", it.value_len);
241         log_info_hexdump(it.value, it.value_len);
242     }
243 }
244 
245 static void att_prepare_write_reset(void){
246     att_prepare_write_error_code = 0;
247     att_prepare_write_error_handle = 0x0000;
248 }
249 
250 static void att_prepare_write_update_errors(uint8_t error_code, uint16_t handle){
251     // first ATT_ERROR_INVALID_ATTRIBUTE_VALUE_LENGTH has highest priority
252     if ((error_code == ATT_ERROR_INVALID_ATTRIBUTE_VALUE_LENGTH) && (error_code != att_prepare_write_error_code)){
253         att_prepare_write_error_code = error_code;
254         att_prepare_write_error_handle = handle;
255         return;
256     }
257     // first ATT_ERROR_INVALID_OFFSET is next
258     if ((error_code == ATT_ERROR_INVALID_OFFSET) && (att_prepare_write_error_code == 0)){
259         att_prepare_write_error_code = error_code;
260         att_prepare_write_error_handle = handle;
261         return;
262     }
263 }
264 
265 static uint16_t setup_error(uint8_t * response_buffer, uint16_t request, uint16_t handle, uint8_t error_code){
266     response_buffer[0] = ATT_ERROR_RESPONSE;
267     response_buffer[1] = request;
268     little_endian_store_16(response_buffer, 2, handle);
269     response_buffer[4] = error_code;
270     return 5;
271 }
272 
273 static inline uint16_t setup_error_read_not_permitted(uint8_t * response_buffer, uint16_t request, uint16_t start_handle){
274     return setup_error(response_buffer, request, start_handle, ATT_ERROR_READ_NOT_PERMITTED);
275 }
276 
277 static inline uint16_t setup_error_write_not_permitted(uint8_t * response_buffer, uint16_t request, uint16_t start_handle){
278     return setup_error(response_buffer, request, start_handle, ATT_ERROR_WRITE_NOT_PERMITTED);
279 }
280 
281 static inline uint16_t setup_error_atribute_not_found(uint8_t * response_buffer, uint16_t request, uint16_t start_handle){
282     return setup_error(response_buffer, request, start_handle, ATT_ERROR_ATTRIBUTE_NOT_FOUND);
283 }
284 
285 static inline uint16_t setup_error_invalid_handle(uint8_t * response_buffer, uint16_t request, uint16_t handle){
286     return setup_error(response_buffer, request, handle, ATT_ERROR_INVALID_HANDLE);
287 }
288 
289 static inline uint16_t setup_error_invalid_offset(uint8_t * response_buffer, uint16_t request, uint16_t handle){
290     return setup_error(response_buffer, request, handle, ATT_ERROR_INVALID_OFFSET);
291 }
292 
293 static inline uint16_t setup_error_invalid_pdu(uint8_t *response_buffer, uint16_t request) {
294     return setup_error(response_buffer, request, 0, ATT_ERROR_INVALID_PDU);
295 }
296 
297 static uint8_t att_validate_security(att_connection_t * att_connection, att_operation_t operation, att_iterator_t * it){
298     int required_security_level = 0;
299     int requires_secure_connection = 0;
300     switch (operation){
301         case ATT_READ:
302             if ((it->flags & ATT_PROPERTY_READ_PERMISSION_BIT_0) != 0){
303                 required_security_level |= 1;
304             }
305             if ((it->flags & ATT_PROPERTY_READ_PERMISSION_BIT_1) != 0){
306                 required_security_level |= 2;
307             }
308             if ((it->flags & ATT_PROPERTY_READ_PERMISSION_SC) != 0){
309                 requires_secure_connection = 1;
310             }
311             break;
312         case ATT_WRITE:
313             if ((it->flags & ATT_PROPERTY_WRITE_PERMISSION_BIT_0) != 0){
314                 required_security_level |= 1;
315             }
316             if ((it->flags & ATT_PROPERTY_WRITE_PERMISSION_BIT_1) != 0){
317                 required_security_level |= 2;
318             }
319             if ((it->flags & ATT_PROPERTY_WRITE_PERMISSION_SC) != 0){
320                 requires_secure_connection = 1;
321             }
322             break;
323     }
324 
325     int required_encryption_size = it->flags >> 12;
326     if (required_encryption_size != 0) required_encryption_size++;   // store -1 to fit into 4 bit
327 
328     log_debug("att_validate_security. flags 0x%04x (=> security level %u, key size %u) authorized %u, authenticated %u, encryption_key_size %u, secure connection %u",
329         it->flags, required_security_level, required_encryption_size, att_connection->authorized, att_connection->authenticated, att_connection->encryption_key_size, att_connection->secure_connection);
330 
331     int sc_missing = requires_secure_connection && (att_connection->secure_connection == 0);
332     switch (required_security_level){
333         case ATT_SECURITY_AUTHORIZED:
334             if ((att_connection->authorized == 0) || sc_missing){
335                 return ATT_ERROR_INSUFFICIENT_AUTHORIZATION;
336             }
337             /* fall through */
338         case ATT_SECURITY_AUTHENTICATED:
339             if ((att_connection->authenticated == 0) || sc_missing){
340                 return ATT_ERROR_INSUFFICIENT_AUTHENTICATION;
341             }
342             /* fall through */
343         case ATT_SECURITY_ENCRYPTED:
344             if ((required_encryption_size > 0) && ((att_connection->encryption_key_size == 0) || sc_missing)){
345                 return ATT_ERROR_INSUFFICIENT_ENCRYPTION;
346             }
347             if (required_encryption_size > att_connection->encryption_key_size){
348                 return ATT_ERROR_INSUFFICIENT_ENCRYPTION_KEY_SIZE;
349             }
350             break;
351         default:
352             break;
353     }
354     return ATT_ERROR_SUCCESS;
355 }
356 
357 //
358 // MARK: ATT_EXCHANGE_MTU_REQUEST
359 //
360 static uint16_t handle_exchange_mtu_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
361                                          uint8_t * response_buffer){
362 
363     if (request_len != 3) return setup_error_invalid_pdu(response_buffer, ATT_EXCHANGE_MTU_REQUEST);
364 
365     uint16_t client_rx_mtu = little_endian_read_16(request_buffer, 1);
366 
367     // find min(local max mtu, remote mtu) >= ATT_DEFAULT_MTU and use as mtu for this connection
368     uint16_t min_mtu = btstack_min(client_rx_mtu, att_connection->max_mtu);
369     uint16_t new_mtu = btstack_max(ATT_DEFAULT_MTU, min_mtu);
370     att_connection->mtu = new_mtu;
371 
372     response_buffer[0] = ATT_EXCHANGE_MTU_RESPONSE;
373     little_endian_store_16(response_buffer, 1, att_connection->mtu);
374     return 3;
375 }
376 
377 
378 //
379 // MARK: ATT_FIND_INFORMATION_REQUEST
380 //
381 // TODO: handle other types then GATT_PRIMARY_SERVICE_UUID and GATT_SECONDARY_SERVICE_UUID
382 //
383 static uint16_t handle_find_information_request2(att_connection_t * att_connection, uint8_t * response_buffer, uint16_t response_buffer_size,
384                                            uint16_t start_handle, uint16_t end_handle){
385 
386     UNUSED(att_connection);
387 
388     log_info("ATT_FIND_INFORMATION_REQUEST: from %04X to %04X", start_handle, end_handle);
389     uint8_t request_type = ATT_FIND_INFORMATION_REQUEST;
390 
391     if ((start_handle > end_handle) || (start_handle == 0)){
392         return setup_error_invalid_handle(response_buffer, request_type, start_handle);
393     }
394 
395     uint16_t offset   = 1;
396     uint16_t uuid_len = 0;
397 
398     att_iterator_t it;
399     att_iterator_init(&it);
400     while (att_iterator_has_next(&it)){
401         att_iterator_fetch_next(&it);
402         if (!it.handle) break;
403         if (it.handle > end_handle) break;
404         if (it.handle < start_handle) continue;
405 
406         // log_info("Handle 0x%04x", it.handle);
407 
408         uint16_t this_uuid_len = (it.flags & ATT_PROPERTY_UUID128) ? 16 : 2;
409 
410         // check if value has same len as last one if not first result
411         if (offset > 1){
412             if (this_uuid_len != uuid_len) {
413                 break;
414             }
415         }
416 
417         // first
418         if (offset == 1) {
419             uuid_len = this_uuid_len;
420             // set format field
421             response_buffer[offset] = (it.flags & ATT_PROPERTY_UUID128) ? 0x02 : 0x01;
422             offset++;
423         }
424 
425         // space?
426         if ((offset + 2 + uuid_len) > response_buffer_size) break;
427 
428         // store
429         little_endian_store_16(response_buffer, offset, it.handle);
430         offset += 2;
431 
432         (void)memcpy(response_buffer + offset, it.uuid, uuid_len);
433         offset += uuid_len;
434     }
435 
436     if (offset == 1){
437         return setup_error_atribute_not_found(response_buffer, request_type, start_handle);
438     }
439 
440     response_buffer[0] = ATT_FIND_INFORMATION_REPLY;
441     return offset;
442 }
443 
444 static uint16_t handle_find_information_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
445                                          uint8_t * response_buffer, uint16_t response_buffer_size){
446 
447     if (request_len != 5) return setup_error_invalid_pdu(response_buffer, ATT_FIND_INFORMATION_REQUEST);
448 
449     uint16_t start_handle = little_endian_read_16(request_buffer, 1);
450     uint16_t end_handle = little_endian_read_16(request_buffer, 3);
451     return handle_find_information_request2(att_connection, response_buffer, response_buffer_size, start_handle, end_handle);
452 }
453 
454 //
455 // MARK: ATT_FIND_BY_TYPE_VALUE
456 //
457 // "Only attributes with attribute handles between and including the Starting Handle parameter
458 // and the Ending Handle parameter that match the requested attri- bute type and the attribute
459 // value that have sufficient permissions to allow reading will be returned" -> (1)
460 //
461 // TODO: handle other types then GATT_PRIMARY_SERVICE_UUID and GATT_SECONDARY_SERVICE_UUID
462 //
463 // NOTE: doesn't handle DYNAMIC values
464 // NOTE: only supports 16 bit UUIDs
465 //
466 static uint16_t handle_find_by_type_value_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
467                                            uint8_t * response_buffer, uint16_t response_buffer_size){
468     UNUSED(att_connection);
469 
470     if (request_len < 7) return setup_error_invalid_pdu(response_buffer, ATT_FIND_BY_TYPE_VALUE_REQUEST);
471 
472     // parse request
473     uint16_t start_handle = little_endian_read_16(request_buffer, 1);
474     uint16_t end_handle = little_endian_read_16(request_buffer, 3);
475     uint16_t attribute_type = little_endian_read_16(request_buffer, 5);
476     const uint8_t *attribute_value = &request_buffer[7];
477     uint16_t attribute_len = request_len - 7;
478 
479     log_info("ATT_FIND_BY_TYPE_VALUE_REQUEST: from %04X to %04X, type %04X, value: ", start_handle, end_handle, attribute_type);
480     log_info_hexdump(attribute_value, attribute_len);
481     uint8_t request_type = ATT_FIND_BY_TYPE_VALUE_REQUEST;
482 
483     if ((start_handle > end_handle) || (start_handle == 0)){
484         return setup_error_invalid_handle(response_buffer, request_type, start_handle);
485     }
486 
487     uint16_t offset      = 1;
488     uint16_t in_group    = 0;
489     uint16_t prev_handle = 0;
490 
491     att_iterator_t it;
492     att_iterator_init(&it);
493     while (att_iterator_has_next(&it)){
494         att_iterator_fetch_next(&it);
495 
496         if (it.handle && (it.handle < start_handle)) continue;
497         if (it.handle > end_handle) break;  // (1)
498 
499         // close current tag, if within a group and a new service definition starts or we reach end of att db
500         if (in_group &&
501             ((it.handle == 0) || att_iterator_match_uuid16(&it, GATT_PRIMARY_SERVICE_UUID) || att_iterator_match_uuid16(&it, GATT_SECONDARY_SERVICE_UUID))){
502 
503             log_info("End of group, handle 0x%04x", prev_handle);
504             little_endian_store_16(response_buffer, offset, prev_handle);
505             offset += 2;
506             in_group = 0;
507 
508             // check if space for another handle pair available
509             if ((offset + 4) > response_buffer_size){
510                 break;
511             }
512         }
513 
514         // keep track of previous handle
515         prev_handle = it.handle;
516 
517         // does current attribute match
518         if (it.handle && att_iterator_match_uuid16(&it, attribute_type) && (attribute_len == it.value_len) && (memcmp(attribute_value, it.value, it.value_len) == 0)){
519             log_info("Begin of group, handle 0x%04x", it.handle);
520             little_endian_store_16(response_buffer, offset, it.handle);
521             offset += 2;
522             in_group = 1;
523         }
524     }
525 
526     if (offset == 1){
527         return setup_error_atribute_not_found(response_buffer, request_type, start_handle);
528     }
529 
530     response_buffer[0] = ATT_FIND_BY_TYPE_VALUE_RESPONSE;
531     return offset;
532 }
533 
534 //
535 // MARK: ATT_READ_BY_TYPE_REQUEST
536 //
537 static uint16_t handle_read_by_type_request2(att_connection_t * att_connection, uint8_t * response_buffer, uint16_t response_buffer_size,
538                                       uint16_t start_handle, uint16_t end_handle,
539                                       uint16_t attribute_type_len, uint8_t * attribute_type){
540 
541     log_info("ATT_READ_BY_TYPE_REQUEST: from %04X to %04X, type: ", start_handle, end_handle);
542     log_info_hexdump(attribute_type, attribute_type_len);
543     uint8_t request_type = ATT_READ_BY_TYPE_REQUEST;
544 
545     if ((start_handle > end_handle) || (start_handle == 0)){
546         return setup_error_invalid_handle(response_buffer, request_type, start_handle);
547     }
548 
549     uint16_t offset   = 1;
550     uint16_t pair_len = 0;
551 
552     att_iterator_t it;
553     att_iterator_init(&it);
554     uint8_t error_code = 0;
555     uint16_t first_matching_but_unreadable_handle = 0;
556 
557     while (att_iterator_has_next(&it)){
558         att_iterator_fetch_next(&it);
559 
560         if ((it.handle == 0 ) || (it.handle > end_handle)) break;
561 
562         if (it.handle < start_handle) continue;
563 
564         // does current attribute match
565         if (!att_iterator_match_uuid(&it, attribute_type, attribute_type_len)) continue;
566 
567         // skip handles that cannot be read but remember that there has been at least one
568         if ((it.flags & ATT_PROPERTY_READ) == 0) {
569             if (first_matching_but_unreadable_handle == 0) {
570                 first_matching_but_unreadable_handle = it.handle;
571             }
572             continue;
573         }
574 
575         // check security requirements
576         error_code = att_validate_security(att_connection, ATT_READ, &it);
577         if (error_code != 0) break;
578 
579         att_update_value_len(&it, att_connection->con_handle);
580 
581 #ifdef ENABLE_ATT_DELAYED_RESPONSE
582         if (it.value_len == ATT_READ_RESPONSE_PENDING){
583             return ATT_READ_RESPONSE_PENDING;
584         }
585 #endif
586 
587         // check if value has same len as last one
588         uint16_t this_pair_len = 2 + it.value_len;
589         if ((offset > 1) && (pair_len != this_pair_len)) {
590             break;
591         }
592 
593         // first
594         if (offset == 1) {
595             pair_len = this_pair_len;
596             response_buffer[offset] = pair_len;
597             offset++;
598         }
599 
600         // space?
601         if ((offset + pair_len) > response_buffer_size) {
602             if (offset > 2) break;
603             it.value_len = response_buffer_size - 4;
604             response_buffer[1] = 2 + it.value_len;
605         }
606 
607         // store
608         little_endian_store_16(response_buffer, offset, it.handle);
609         offset += 2;
610         uint16_t bytes_copied = att_copy_value(&it, 0, response_buffer + offset, it.value_len, att_connection->con_handle);
611         offset += bytes_copied;
612     }
613 
614     // at least one attribute could be read
615     if (offset > 1){
616         response_buffer[0] = ATT_READ_BY_TYPE_RESPONSE;
617         return offset;
618     }
619 
620     // first attribute had an error
621     if (error_code != 0){
622         return setup_error(response_buffer, request_type, start_handle, error_code);
623     }
624 
625     // no other errors, but all found attributes had been non-readable
626     if (first_matching_but_unreadable_handle != 0){
627         return setup_error_read_not_permitted(response_buffer, request_type, first_matching_but_unreadable_handle);
628     }
629 
630     // attribute not found
631     return setup_error_atribute_not_found(response_buffer, request_type, start_handle);
632 }
633 
634 static uint16_t handle_read_by_type_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
635                                      uint8_t * response_buffer, uint16_t response_buffer_size){
636 
637     uint16_t attribute_type_len;
638     switch (request_len){
639         case 7:
640             attribute_type_len = 2;
641             break;
642         case 21:
643             attribute_type_len = 16;
644             break;
645         default:
646             return setup_error_invalid_pdu(response_buffer, ATT_READ_BY_TYPE_REQUEST);
647     }
648 
649     uint16_t start_handle = little_endian_read_16(request_buffer, 1);
650     uint16_t end_handle = little_endian_read_16(request_buffer, 3);
651     return handle_read_by_type_request2(att_connection, response_buffer, response_buffer_size, start_handle, end_handle, attribute_type_len, &request_buffer[5]);
652 }
653 
654 //
655 // MARK: ATT_READ_BY_TYPE_REQUEST
656 //
657 static uint16_t handle_read_request2(att_connection_t * att_connection, uint8_t * response_buffer, uint16_t response_buffer_size, uint16_t handle){
658 
659     log_info("ATT_READ_REQUEST: handle %04x", handle);
660     uint8_t request_type = ATT_READ_REQUEST;
661 
662     att_iterator_t it;
663     int ok = att_find_handle(&it, handle);
664     if (!ok){
665         return setup_error_invalid_handle(response_buffer, request_type, handle);
666     }
667 
668     // check if handle can be read
669     if ((it.flags & ATT_PROPERTY_READ) == 0) {
670         return setup_error_read_not_permitted(response_buffer, request_type, handle);
671     }
672 
673     // check security requirements
674     uint8_t error_code = att_validate_security(att_connection, ATT_READ, &it);
675     if (error_code) {
676         return setup_error(response_buffer, request_type, handle, error_code);
677     }
678 
679     att_update_value_len(&it, att_connection->con_handle);
680 
681 #ifdef ENABLE_ATT_DELAYED_RESPONSE
682     if (it.value_len == ATT_READ_RESPONSE_PENDING) return ATT_READ_RESPONSE_PENDING;
683 #endif
684 
685     // store
686     uint16_t offset   = 1;
687     uint16_t bytes_copied = att_copy_value(&it, 0, response_buffer + offset, response_buffer_size - offset, att_connection->con_handle);
688     offset += bytes_copied;
689 
690     response_buffer[0] = ATT_READ_RESPONSE;
691     return offset;
692 }
693 
694 static uint16_t handle_read_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
695                              uint8_t * response_buffer, uint16_t response_buffer_size){
696 
697     if (request_len != 3) return setup_error_invalid_pdu(response_buffer, ATT_READ_REQUEST);
698 
699     uint16_t handle = little_endian_read_16(request_buffer, 1);
700     return handle_read_request2(att_connection, response_buffer, response_buffer_size, handle);
701 }
702 
703 //s
704 // MARK: ATT_READ_BLOB_REQUEST 0x0c
705 //
706 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){
707     log_info("ATT_READ_BLOB_REQUEST: handle %04x, offset %u", handle, value_offset);
708     uint8_t request_type = ATT_READ_BLOB_REQUEST;
709 
710     att_iterator_t it;
711     int ok = att_find_handle(&it, handle);
712     if (!ok){
713         return setup_error_invalid_handle(response_buffer, request_type, handle);
714     }
715 
716     // check if handle can be read
717     if ((it.flags & ATT_PROPERTY_READ) == 0) {
718         return setup_error_read_not_permitted(response_buffer, request_type, handle);
719     }
720 
721     // check security requirements
722     uint8_t error_code = att_validate_security(att_connection, ATT_READ, &it);
723     if (error_code) {
724         return setup_error(response_buffer, request_type, handle, error_code);
725     }
726 
727     att_update_value_len(&it, att_connection->con_handle);
728 
729 #ifdef ENABLE_ATT_DELAYED_RESPONSE
730     if (it.value_len == ATT_READ_RESPONSE_PENDING) return ATT_READ_RESPONSE_PENDING;
731 #endif
732 
733     if (value_offset > it.value_len){
734         return setup_error_invalid_offset(response_buffer, request_type, handle);
735     }
736 
737     // store
738     uint16_t offset   = 1;
739     uint16_t bytes_copied = att_copy_value(&it, value_offset, response_buffer + offset, response_buffer_size - offset, att_connection->con_handle);
740     offset += bytes_copied;
741 
742     response_buffer[0] = ATT_READ_BLOB_RESPONSE;
743     return offset;
744 }
745 
746 static uint16_t handle_read_blob_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
747                                   uint8_t * response_buffer, uint16_t response_buffer_size){
748 
749     if (request_len != 5) return setup_error_invalid_pdu(response_buffer, ATT_READ_BLOB_REQUEST);
750 
751     uint16_t handle = little_endian_read_16(request_buffer, 1);
752     uint16_t value_offset = little_endian_read_16(request_buffer, 3);
753     return handle_read_blob_request2(att_connection, response_buffer, response_buffer_size, handle, value_offset);
754 }
755 
756 //
757 // MARK: ATT_READ_MULTIPLE_REQUEST 0x0e
758 //
759 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){
760     log_info("ATT_READ_MULTIPLE_REQUEST: num handles %u", num_handles);
761     uint8_t request_type = ATT_READ_MULTIPLE_REQUEST;
762 
763     // TODO: figure out which error to respond with
764     // if (num_handles < 2){
765     //     return setup_error(response_buffer, ATT_READ_MULTIPLE_REQUEST, handle, ???);
766     // }
767 
768     uint16_t offset   = 1;
769 
770     int i;
771     uint8_t error_code = 0;
772     uint16_t handle = 0;
773 
774 #ifdef ENABLE_ATT_DELAYED_RESPONSE
775     bool read_request_pending = false;
776 #endif
777 
778     for (i=0;i<num_handles;i++){
779         handle = little_endian_read_16(handles, i << 1);
780 
781         if (handle == 0){
782             return setup_error_invalid_handle(response_buffer, request_type, handle);
783         }
784 
785         att_iterator_t it;
786 
787         int ok = att_find_handle(&it, handle);
788         if (!ok){
789             return setup_error_invalid_handle(response_buffer, request_type, handle);
790         }
791 
792         // check if handle can be read
793         if ((it.flags & ATT_PROPERTY_READ) == 0) {
794             error_code = ATT_ERROR_READ_NOT_PERMITTED;
795             break;
796         }
797 
798         // check security requirements
799         error_code = att_validate_security(att_connection, ATT_READ, &it);
800         if (error_code) break;
801 
802         att_update_value_len(&it, att_connection->con_handle);
803 
804 #ifdef ENABLE_ATT_DELAYED_RESPONSE
805         if (it.value_len == ATT_READ_RESPONSE_PENDING) {
806             read_request_pending = true;
807         }
808         if (read_request_pending) continue;
809 #endif
810 
811         // store
812         uint16_t bytes_copied = att_copy_value(&it, 0, response_buffer + offset, response_buffer_size - offset, att_connection->con_handle);
813         offset += bytes_copied;
814     }
815 
816     if (error_code){
817         return setup_error(response_buffer, request_type, handle, error_code);
818     }
819 
820     response_buffer[0] = ATT_READ_MULTIPLE_RESPONSE;
821     return offset;
822 }
823 static uint16_t handle_read_multiple_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
824                                       uint8_t * response_buffer, uint16_t response_buffer_size){
825 
826     // 1 byte opcode + two or more attribute handles (2 bytes each)
827     if ( (request_len < 5) || ((request_len & 1) == 0) ) return setup_error_invalid_pdu(response_buffer,
828                                                                                         ATT_READ_MULTIPLE_REQUEST);
829 
830     int num_handles = (request_len - 1) >> 1;
831     return handle_read_multiple_request2(att_connection, response_buffer, response_buffer_size, num_handles, &request_buffer[1]);
832 }
833 
834 //
835 // MARK: ATT_READ_BY_GROUP_TYPE_REQUEST 0x10
836 //
837 // Only handles GATT_PRIMARY_SERVICE_UUID and GATT_SECONDARY_SERVICE_UUID
838 // Core v4.0, vol 3, part g, 2.5.3
839 // "The «Primary Service» and «Secondary Service» grouping types may be used in the Read By Group Type Request.
840 //  The «Characteristic» grouping type shall not be used in the ATT Read By Group Type Request."
841 //
842 // NOTE: doesn't handle DYNAMIC values
843 //
844 // NOTE: we don't check for security as PRIMARY and SECONDAY SERVICE definition shouldn't be protected
845 // Core 4.0, vol 3, part g, 8.1
846 // "The list of services and characteristics that a device supports is not considered private or
847 //  confidential information, and therefore the Service and Characteristic Discovery procedures
848 //  shall always be permitted. "
849 //
850 static uint16_t handle_read_by_group_type_request2(att_connection_t * att_connection, uint8_t * response_buffer, uint16_t response_buffer_size,
851                                             uint16_t start_handle, uint16_t end_handle,
852                                             uint16_t attribute_type_len, uint8_t * attribute_type){
853 
854     UNUSED(att_connection);
855 
856     log_info("ATT_READ_BY_GROUP_TYPE_REQUEST: from %04X to %04X, buffer size %u, type: ", start_handle, end_handle, response_buffer_size);
857     log_info_hexdump(attribute_type, attribute_type_len);
858     uint8_t request_type = ATT_READ_BY_GROUP_TYPE_REQUEST;
859 
860     if ((start_handle > end_handle) || (start_handle == 0)){
861         return setup_error_invalid_handle(response_buffer, request_type, start_handle);
862     }
863 
864     // assert UUID is primary or secondary service uuid
865     uint16_t uuid16 = uuid16_from_uuid(attribute_type_len, attribute_type);
866     if ((uuid16 != GATT_PRIMARY_SERVICE_UUID) && (uuid16 != GATT_SECONDARY_SERVICE_UUID)){
867         return setup_error(response_buffer, request_type, start_handle, ATT_ERROR_UNSUPPORTED_GROUP_TYPE);
868     }
869 
870     uint16_t offset   = 1;
871     uint16_t pair_len = 0;
872     uint16_t in_group = 0;
873     uint16_t group_start_handle = 0;
874     uint8_t const * group_start_value = NULL;
875     uint16_t prev_handle = 0;
876 
877     att_iterator_t it;
878     att_iterator_init(&it);
879     while (att_iterator_has_next(&it)){
880         att_iterator_fetch_next(&it);
881 
882         if (it.handle && (it.handle < start_handle)) continue;
883         if (it.handle > end_handle) break;  // (1)
884 
885         // log_info("Handle 0x%04x", it.handle);
886 
887         // close current tag, if within a group and a new service definition starts or we reach end of att db
888         if (in_group &&
889             ((it.handle == 0) || att_iterator_match_uuid16(&it, GATT_PRIMARY_SERVICE_UUID) || att_iterator_match_uuid16(&it, GATT_SECONDARY_SERVICE_UUID))){
890             // log_info("End of group, handle 0x%04x, val_len: %u", prev_handle, pair_len - 4);
891 
892             little_endian_store_16(response_buffer, offset, group_start_handle);
893             offset += 2;
894             little_endian_store_16(response_buffer, offset, prev_handle);
895             offset += 2;
896             (void)memcpy(response_buffer + offset, group_start_value,
897                          pair_len - 4);
898             offset += pair_len - 4;
899             in_group = 0;
900 
901             // check if space for another handle pair available
902             if ((offset + pair_len) > response_buffer_size){
903                 break;
904             }
905         }
906 
907         // keep track of previous handle
908         prev_handle = it.handle;
909 
910         // does current attribute match
911         // log_info("compare: %04x == %04x", *(uint16_t*) context->attribute_type, *(uint16_t*) uuid);
912         if (it.handle && att_iterator_match_uuid(&it, attribute_type, attribute_type_len)) {
913 
914             // check if value has same len as last one
915             uint16_t this_pair_len = 4 + it.value_len;
916             if (offset > 1){
917                 if (this_pair_len != pair_len) {
918                     break;
919                 }
920             }
921 
922             // log_info("Begin of group, handle 0x%04x", it.handle);
923 
924             // first
925             if (offset == 1) {
926                 pair_len = this_pair_len;
927                 response_buffer[offset] = this_pair_len;
928                 offset++;
929             }
930 
931             group_start_handle = it.handle;
932             group_start_value  = it.value;
933             in_group = 1;
934         }
935     }
936 
937     if (offset == 1){
938         return setup_error_atribute_not_found(response_buffer, request_type, start_handle);
939     }
940 
941     response_buffer[0] = ATT_READ_BY_GROUP_TYPE_RESPONSE;
942     return offset;
943 }
944 static uint16_t handle_read_by_group_type_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
945                                            uint8_t * response_buffer, uint16_t response_buffer_size){
946     uint16_t attribute_type_len;
947     switch (request_len){
948         case 7:
949             attribute_type_len = 2;
950             break;
951         case 21:
952             attribute_type_len = 16;
953             break;
954         default:
955             return setup_error_invalid_pdu(response_buffer, ATT_READ_BY_GROUP_TYPE_REQUEST);
956     }
957 
958     uint16_t start_handle = little_endian_read_16(request_buffer, 1);
959     uint16_t end_handle = little_endian_read_16(request_buffer, 3);
960     return handle_read_by_group_type_request2(att_connection, response_buffer, response_buffer_size, start_handle, end_handle, attribute_type_len, &request_buffer[5]);
961 }
962 
963 //
964 // MARK: ATT_WRITE_REQUEST 0x12
965 static uint16_t handle_write_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
966                               uint8_t * response_buffer, uint16_t response_buffer_size){
967 
968     UNUSED(response_buffer_size);
969 
970     if (request_len < 3) return setup_error_invalid_pdu(response_buffer, ATT_WRITE_REQUEST);
971 
972     uint8_t request_type = ATT_WRITE_REQUEST;
973 
974     uint16_t handle = little_endian_read_16(request_buffer, 1);
975     att_iterator_t it;
976     int ok = att_find_handle(&it, handle);
977     if (!ok) {
978         return setup_error_invalid_handle(response_buffer, request_type, handle);
979     }
980     if (att_write_callback == NULL) {
981         return setup_error_write_not_permitted(response_buffer, request_type, handle);
982     }
983     if ((it.flags & ATT_PROPERTY_WRITE) == 0) {
984         return setup_error_write_not_permitted(response_buffer, request_type, handle);
985     }
986     if ((it.flags & ATT_PROPERTY_DYNAMIC) == 0) {
987         return setup_error_write_not_permitted(response_buffer, request_type, handle);
988     }
989     // check security requirements
990     int error_code = att_validate_security(att_connection, ATT_WRITE, &it);
991     if (error_code) {
992         return setup_error(response_buffer, request_type, handle, error_code);
993     }
994     att_persistent_ccc_cache(&it);
995     error_code = (*att_write_callback)(att_connection->con_handle, handle, ATT_TRANSACTION_MODE_NONE, 0, request_buffer + 3, request_len - 3);
996 
997 #ifdef ENABLE_ATT_DELAYED_RESPONSE
998     if (error_code == ATT_ERROR_WRITE_RESPONSE_PENDING) return ATT_INTERNAL_WRITE_RESPONSE_PENDING;
999 #endif
1000 
1001     if (error_code) {
1002         return setup_error(response_buffer, request_type, handle, error_code);
1003     }
1004     response_buffer[0] = ATT_WRITE_RESPONSE;
1005     return 1;
1006 }
1007 
1008 //
1009 // MARK: ATT_PREPARE_WRITE_REQUEST 0x16
1010 static uint16_t handle_prepare_write_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
1011                                       uint8_t * response_buffer, uint16_t response_buffer_size){
1012 
1013     uint8_t request_type = ATT_PREPARE_WRITE_REQUEST;
1014 
1015     if (request_len < 5) return setup_error_invalid_pdu(response_buffer, request_type);
1016 
1017     uint16_t handle = little_endian_read_16(request_buffer, 1);
1018     uint16_t offset = little_endian_read_16(request_buffer, 3);
1019     if (att_write_callback == NULL) {
1020         return setup_error_write_not_permitted(response_buffer, request_type, handle);
1021     }
1022     att_iterator_t it;
1023     if (att_find_handle(&it, handle) == 0) {
1024         return setup_error_invalid_handle(response_buffer, request_type, handle);
1025     }
1026     if ((it.flags & ATT_PROPERTY_WRITE) == 0) {
1027         return setup_error_write_not_permitted(response_buffer, request_type, handle);
1028     }
1029     if ((it.flags & ATT_PROPERTY_DYNAMIC) == 0) {
1030         return setup_error_write_not_permitted(response_buffer, request_type, handle);
1031     }
1032     // check security requirements
1033     int error_code = att_validate_security(att_connection, ATT_WRITE, &it);
1034     if (error_code) {
1035         return setup_error(response_buffer, request_type, handle, error_code);
1036     }
1037 
1038     error_code = (*att_write_callback)(att_connection->con_handle, handle, ATT_TRANSACTION_MODE_ACTIVE, offset, request_buffer + 5, request_len - 5);
1039     switch (error_code){
1040         case 0:
1041             break;
1042         case ATT_ERROR_INVALID_OFFSET:
1043         case ATT_ERROR_INVALID_ATTRIBUTE_VALUE_LENGTH:
1044             // postpone to execute write request
1045             att_prepare_write_update_errors(error_code, handle);
1046             break;
1047 #ifdef ENABLE_ATT_DELAYED_RESPONSE
1048         case ATT_ERROR_WRITE_RESPONSE_PENDING:
1049             return ATT_INTERNAL_WRITE_RESPONSE_PENDING;
1050 #endif
1051         default:
1052             return setup_error(response_buffer, request_type, handle, error_code);
1053     }
1054 
1055     // response: echo request
1056     uint16_t bytes_to_echo = btstack_min(request_len, response_buffer_size);
1057     (void)memcpy(response_buffer, request_buffer, bytes_to_echo);
1058     response_buffer[0] = ATT_PREPARE_WRITE_RESPONSE;
1059     return request_len;
1060 }
1061 
1062 /*
1063  * @brief transcation queue of prepared writes, e.g., after disconnect
1064  */
1065 void att_clear_transaction_queue(att_connection_t * att_connection){
1066     (*att_write_callback)(att_connection->con_handle, 0, ATT_TRANSACTION_MODE_CANCEL, 0, NULL, 0);
1067 }
1068 
1069 // MARK: ATT_EXECUTE_WRITE_REQUEST 0x18
1070 // NOTE: security has been verified by handle_prepare_write_request
1071 static uint16_t handle_execute_write_request(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len,
1072                                       uint8_t * response_buffer, uint16_t response_buffer_size){
1073 
1074     UNUSED(response_buffer_size);
1075 
1076     uint8_t request_type = ATT_EXECUTE_WRITE_REQUEST;
1077 
1078     if (request_len < 2) return setup_error_invalid_pdu(response_buffer, request_type);
1079 
1080     if (att_write_callback == NULL) {
1081         return setup_error_write_not_permitted(response_buffer, request_type, 0);
1082     }
1083 
1084     if (request_buffer[1]) {
1085         // validate queued write
1086         if (att_prepare_write_error_code == 0){
1087             att_prepare_write_error_code = (*att_write_callback)(att_connection->con_handle, 0, ATT_TRANSACTION_MODE_VALIDATE, 0, NULL, 0);
1088         }
1089 #ifdef ENABLE_ATT_DELAYED_RESPONSE
1090         if (att_prepare_write_error_code == ATT_ERROR_WRITE_RESPONSE_PENDING) return ATT_INTERNAL_WRITE_RESPONSE_PENDING;
1091 #endif
1092         // deliver queued errors
1093         if (att_prepare_write_error_code){
1094             att_clear_transaction_queue(att_connection);
1095             uint8_t  error_code = att_prepare_write_error_code;
1096             uint16_t handle     = att_prepare_write_error_handle;
1097             att_prepare_write_reset();
1098             return setup_error(response_buffer, request_type, handle, error_code);
1099         }
1100         att_write_callback(att_connection->con_handle, 0, ATT_TRANSACTION_MODE_EXECUTE, 0, NULL, 0);
1101     } else {
1102         att_clear_transaction_queue(att_connection);
1103     }
1104     response_buffer[0] = ATT_EXECUTE_WRITE_RESPONSE;
1105     return 1;
1106 }
1107 
1108 // MARK: ATT_WRITE_COMMAND 0x52
1109 // Core 4.0, vol 3, part F, 3.4.5.3
1110 // "No Error Response or Write Response shall be sent in response to this command"
1111 static void handle_write_command(att_connection_t * att_connection, uint8_t * request_buffer,  uint16_t request_len, uint16_t required_flags){
1112 
1113     if (request_len < 3) return;
1114 
1115     uint16_t handle = little_endian_read_16(request_buffer, 1);
1116     if (att_write_callback == NULL) return;
1117 
1118     att_iterator_t it;
1119     int ok = att_find_handle(&it, handle);
1120     if (!ok) return;
1121     if ((it.flags & ATT_PROPERTY_DYNAMIC) == 0) return;
1122     if ((it.flags & required_flags) == 0) return;
1123     if (att_validate_security(att_connection, ATT_WRITE, &it)) return;
1124     att_persistent_ccc_cache(&it);
1125     (*att_write_callback)(att_connection->con_handle, handle, ATT_TRANSACTION_MODE_NONE, 0, request_buffer + 3, request_len - 3);
1126 }
1127 
1128 // MARK: helper for ATT_HANDLE_VALUE_NOTIFICATION and ATT_HANDLE_VALUE_INDICATION
1129 static uint16_t prepare_handle_value(att_connection_t * att_connection,
1130                                      uint16_t handle,
1131                                      const uint8_t *value,
1132                                      uint16_t value_len,
1133                                      uint8_t * response_buffer){
1134     little_endian_store_16(response_buffer, 1, handle);
1135     if (value_len > (att_connection->mtu - 3)){
1136         value_len = att_connection->mtu - 3;
1137     }
1138     (void)memcpy(&response_buffer[3], value, value_len);
1139     return value_len + 3;
1140 }
1141 
1142 // MARK: ATT_HANDLE_VALUE_NOTIFICATION 0x1b
1143 uint16_t att_prepare_handle_value_notification(att_connection_t * att_connection,
1144                                                uint16_t handle,
1145                                                const uint8_t *value,
1146                                                uint16_t value_len,
1147                                                uint8_t * response_buffer){
1148 
1149     response_buffer[0] = ATT_HANDLE_VALUE_NOTIFICATION;
1150     return prepare_handle_value(att_connection, handle, value, value_len, response_buffer);
1151 }
1152 
1153 // MARK: ATT_HANDLE_VALUE_INDICATION 0x1d
1154 uint16_t att_prepare_handle_value_indication(att_connection_t * att_connection,
1155                                              uint16_t handle,
1156                                              const uint8_t *value,
1157                                              uint16_t value_len,
1158                                              uint8_t * response_buffer){
1159 
1160     response_buffer[0] = ATT_HANDLE_VALUE_INDICATION;
1161     return prepare_handle_value(att_connection, handle, value, value_len, response_buffer);
1162 }
1163 
1164 // MARK: Dispatcher
1165 uint16_t att_handle_request(att_connection_t * att_connection,
1166                             uint8_t * request_buffer,
1167                             uint16_t request_len,
1168                             uint8_t * response_buffer){
1169     uint16_t response_len = 0;
1170     uint16_t response_buffer_size = att_connection->mtu;
1171 
1172     switch (request_buffer[0]){
1173         case ATT_EXCHANGE_MTU_REQUEST:
1174             response_len = handle_exchange_mtu_request(att_connection, request_buffer, request_len, response_buffer);
1175             break;
1176         case ATT_FIND_INFORMATION_REQUEST:
1177             response_len = handle_find_information_request(att_connection, request_buffer, request_len,response_buffer, response_buffer_size);
1178             break;
1179         case ATT_FIND_BY_TYPE_VALUE_REQUEST:
1180             response_len = handle_find_by_type_value_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1181             break;
1182         case ATT_READ_BY_TYPE_REQUEST:
1183             response_len = handle_read_by_type_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1184             break;
1185         case ATT_READ_REQUEST:
1186             response_len = handle_read_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1187             break;
1188         case ATT_READ_BLOB_REQUEST:
1189             response_len = handle_read_blob_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1190             break;
1191         case ATT_READ_MULTIPLE_REQUEST:
1192             response_len = handle_read_multiple_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1193             break;
1194         case ATT_READ_BY_GROUP_TYPE_REQUEST:
1195             response_len = handle_read_by_group_type_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1196             break;
1197         case ATT_WRITE_REQUEST:
1198             response_len = handle_write_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1199             break;
1200         case ATT_PREPARE_WRITE_REQUEST:
1201             response_len = handle_prepare_write_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1202             break;
1203         case ATT_EXECUTE_WRITE_REQUEST:
1204             response_len = handle_execute_write_request(att_connection, request_buffer, request_len, response_buffer, response_buffer_size);
1205             break;
1206         case ATT_WRITE_COMMAND:
1207             handle_write_command(att_connection, request_buffer, request_len, ATT_PROPERTY_WRITE_WITHOUT_RESPONSE);
1208             break;
1209 #ifdef ENABLE_LE_SIGNED_WRITE
1210         case ATT_SIGNED_WRITE_COMMAND:
1211             handle_write_command(att_connection, request_buffer, request_len, ATT_PROPERTY_AUTHENTICATED_SIGNED_WRITE);
1212             break;
1213 #endif
1214         default:
1215             log_info("Unhandled ATT Command: %02X, DATA: ", request_buffer[0]);
1216             log_info_hexdump(&request_buffer[9], request_len-9);
1217             break;
1218     }
1219     return response_len;
1220 }
1221 
1222 // returns 1 if service found. only primary service.
1223 bool gatt_server_get_get_handle_range_for_service_with_uuid16(uint16_t uuid16, uint16_t * start_handle, uint16_t * end_handle){
1224     uint16_t in_group    = 0;
1225     uint16_t prev_handle = 0;
1226 
1227     uint8_t attribute_value[2];
1228     int attribute_len = sizeof(attribute_value);
1229     little_endian_store_16(attribute_value, 0, uuid16);
1230 
1231     att_iterator_t it;
1232     att_iterator_init(&it);
1233     while (att_iterator_has_next(&it)){
1234         att_iterator_fetch_next(&it);
1235         int new_service_started = att_iterator_match_uuid16(&it, GATT_PRIMARY_SERVICE_UUID) || att_iterator_match_uuid16(&it, GATT_SECONDARY_SERVICE_UUID);
1236 
1237         // close current tag, if within a group and a new service definition starts or we reach end of att db
1238         if (in_group &&
1239             ((it.handle == 0) || new_service_started)){
1240             *end_handle = prev_handle;
1241             return true;
1242         }
1243 
1244         // keep track of previous handle
1245         prev_handle = it.handle;
1246 
1247         // check if found
1248         if (it.handle && new_service_started && (attribute_len == it.value_len) && (memcmp(attribute_value, it.value, it.value_len) == 0)){
1249             *start_handle = it.handle;
1250             in_group = true;
1251         }
1252     }
1253     return false;
1254 }
1255 
1256 // returns false if not found
1257 uint16_t gatt_server_get_value_handle_for_characteristic_with_uuid16(uint16_t start_handle, uint16_t end_handle, uint16_t uuid16){
1258     att_iterator_t it;
1259     att_iterator_init(&it);
1260     while (att_iterator_has_next(&it)){
1261         att_iterator_fetch_next(&it);
1262         if (it.handle && (it.handle < start_handle)) continue;
1263         if (it.handle > end_handle) break;  // (1)
1264         if (it.handle == 0) break;
1265         if (att_iterator_match_uuid16(&it, uuid16)) return it.handle;
1266     }
1267     return 0;
1268 }
1269 
1270 uint16_t gatt_server_get_descriptor_handle_for_characteristic_with_uuid16(uint16_t start_handle, uint16_t end_handle, uint16_t characteristic_uuid16, uint16_t descriptor_uuid16){
1271     att_iterator_t it;
1272     att_iterator_init(&it);
1273     int characteristic_found = 0;
1274     while (att_iterator_has_next(&it)){
1275         att_iterator_fetch_next(&it);
1276         if (it.handle && (it.handle < start_handle)) continue;
1277         if (it.handle > end_handle) break;  // (1)
1278         if (it.handle == 0) break;
1279         if (att_iterator_match_uuid16(&it, characteristic_uuid16)){
1280             characteristic_found = 1;
1281             continue;
1282         }
1283         if (att_iterator_match_uuid16(&it, GATT_PRIMARY_SERVICE_UUID)
1284          || att_iterator_match_uuid16(&it, GATT_SECONDARY_SERVICE_UUID)
1285          || att_iterator_match_uuid16(&it, GATT_CHARACTERISTICS_UUID)){
1286             if (characteristic_found) break;
1287             continue;
1288         }
1289         if (characteristic_found && att_iterator_match_uuid16(&it, descriptor_uuid16)){
1290             return it.handle;
1291         }
1292     }
1293     return 0;
1294 }
1295 
1296 // returns 0 if not found
1297 uint16_t gatt_server_get_client_configuration_handle_for_characteristic_with_uuid16(uint16_t start_handle, uint16_t end_handle, uint16_t characteristic_uuid16){
1298     return gatt_server_get_descriptor_handle_for_characteristic_with_uuid16(start_handle, end_handle, characteristic_uuid16, GATT_CLIENT_CHARACTERISTICS_CONFIGURATION);
1299 }
1300 // returns 0 if not found
1301 
1302 uint16_t gatt_server_get_server_configuration_handle_for_characteristic_with_uuid16(uint16_t start_handle, uint16_t end_handle, uint16_t characteristic_uuid16){
1303     return gatt_server_get_descriptor_handle_for_characteristic_with_uuid16(start_handle, end_handle, characteristic_uuid16, GATT_SERVER_CHARACTERISTICS_CONFIGURATION);
1304 }
1305 
1306 // returns 1 if service found. only primary service.
1307 int gatt_server_get_get_handle_range_for_service_with_uuid128(const uint8_t * uuid128, uint16_t * start_handle, uint16_t * end_handle){
1308     uint16_t in_group    = 0;
1309     uint16_t prev_handle = 0;
1310 
1311     uint8_t attribute_value[16];
1312     int attribute_len = sizeof(attribute_value);
1313     reverse_128(uuid128, attribute_value);
1314 
1315     att_iterator_t it;
1316     att_iterator_init(&it);
1317     while (att_iterator_has_next(&it)){
1318         att_iterator_fetch_next(&it);
1319         int new_service_started = att_iterator_match_uuid16(&it, GATT_PRIMARY_SERVICE_UUID) || att_iterator_match_uuid16(&it, GATT_SECONDARY_SERVICE_UUID);
1320 
1321         // close current tag, if within a group and a new service definition starts or we reach end of att db
1322         if (in_group &&
1323             ((it.handle == 0) || new_service_started)){
1324             *end_handle = prev_handle;
1325             return 1;
1326         }
1327 
1328         // keep track of previous handle
1329         prev_handle = it.handle;
1330 
1331         // check if found
1332         if (it.handle && new_service_started && (attribute_len == it.value_len) && (memcmp(attribute_value, it.value, it.value_len) == 0)){
1333             *start_handle = it.handle;
1334             in_group = 1;
1335         }
1336     }
1337     return 0;
1338 }
1339 
1340 // returns 0 if not found
1341 uint16_t gatt_server_get_value_handle_for_characteristic_with_uuid128(uint16_t start_handle, uint16_t end_handle, const uint8_t * uuid128){
1342     uint8_t attribute_value[16];
1343     reverse_128(uuid128, attribute_value);
1344     att_iterator_t it;
1345     att_iterator_init(&it);
1346     while (att_iterator_has_next(&it)){
1347         att_iterator_fetch_next(&it);
1348         if (it.handle && (it.handle < start_handle)) continue;
1349         if (it.handle > end_handle) break;  // (1)
1350         if (it.handle == 0) break;
1351         if (att_iterator_match_uuid(&it, attribute_value, 16)) return it.handle;
1352     }
1353     return 0;
1354 }
1355 
1356 // returns 0 if not found
1357 uint16_t gatt_server_get_client_configuration_handle_for_characteristic_with_uuid128(uint16_t start_handle, uint16_t end_handle, const uint8_t * uuid128){
1358     uint8_t attribute_value[16];
1359     reverse_128(uuid128, attribute_value);
1360     att_iterator_t it;
1361     att_iterator_init(&it);
1362     int characteristic_found = 0;
1363     while (att_iterator_has_next(&it)){
1364         att_iterator_fetch_next(&it);
1365         if (it.handle && (it.handle < start_handle)) continue;
1366         if (it.handle > end_handle) break;  // (1)
1367         if (it.handle == 0) break;
1368         if (att_iterator_match_uuid(&it, attribute_value, 16)){
1369             characteristic_found = 1;
1370             continue;
1371         }
1372         if (att_iterator_match_uuid16(&it, GATT_PRIMARY_SERVICE_UUID)
1373          || att_iterator_match_uuid16(&it, GATT_SECONDARY_SERVICE_UUID)
1374          || att_iterator_match_uuid16(&it, GATT_CHARACTERISTICS_UUID)){
1375             if (characteristic_found) break;
1376             continue;
1377         }
1378         if (characteristic_found && att_iterator_match_uuid16(&it, GATT_CLIENT_CHARACTERISTICS_CONFIGURATION)){
1379             return it.handle;
1380         }
1381     }
1382     return 0;
1383 }
1384 
1385 
1386 // 1-item cache to optimize query during write_callback
1387 static void att_persistent_ccc_cache(att_iterator_t * it){
1388     att_persistent_ccc_handle = it->handle;
1389     if (it->flags & ATT_PROPERTY_UUID128){
1390         att_persistent_ccc_uuid16 = 0;
1391     } else {
1392         att_persistent_ccc_uuid16 = little_endian_read_16(it->uuid, 0);
1393     }
1394 }
1395 
1396 bool att_is_persistent_ccc(uint16_t handle){
1397     if (handle != att_persistent_ccc_handle){
1398         att_iterator_t it;
1399         int ok = att_find_handle(&it, handle);
1400         if (!ok) return false;
1401         att_persistent_ccc_cache(&it);
1402     }
1403     return att_persistent_ccc_uuid16 == GATT_CLIENT_CHARACTERISTICS_CONFIGURATION;
1404 }
1405 
1406 // att_read_callback helpers
1407 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){
1408     if (buffer){
1409         uint16_t bytes_to_copy = btstack_min(blob_size - offset, buffer_size);
1410         (void)memcpy(buffer, &blob[offset], bytes_to_copy);
1411         return bytes_to_copy;
1412     } else {
1413         return blob_size;
1414     }
1415 }
1416 
1417 uint16_t att_read_callback_handle_little_endian_32(uint32_t value, uint16_t offset, uint8_t * buffer, uint16_t buffer_size){
1418     uint8_t value_buffer[4];
1419     little_endian_store_32(value_buffer, 0, value);
1420     return att_read_callback_handle_blob(value_buffer, sizeof(value_buffer), offset, buffer, buffer_size);
1421 }
1422 
1423 uint16_t att_read_callback_handle_little_endian_16(uint16_t value, uint16_t offset, uint8_t * buffer, uint16_t buffer_size){
1424     uint8_t value_buffer[2];
1425     little_endian_store_16(value_buffer, 0, value);
1426     return att_read_callback_handle_blob(value_buffer, sizeof(value_buffer), offset, buffer, buffer_size);
1427 }
1428 
1429 uint16_t att_read_callback_handle_byte(uint8_t value, uint16_t offset, uint8_t * buffer, uint16_t buffer_size){
1430     uint8_t value_buffer[1];
1431     value_buffer[0] = value;
1432     return att_read_callback_handle_blob(value_buffer, sizeof(value_buffer), offset, buffer, buffer_size);
1433 }
1434