xref: /btstack/src/l2cap.c (revision c48b2a2cf14d777d2d8da7ec3a45007a1ec0b275)
1 /*
2  * Copyright (C) 2014 BlueKitchen GmbH
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the copyright holders nor the names of
14  *    contributors may be used to endorse or promote products derived
15  *    from this software without specific prior written permission.
16  * 4. Any redistribution, use, or modification is done solely for
17  *    personal benefit and not for any commercial purpose or for
18  *    monetary gain.
19  *
20  * THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
24  * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
26  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
27  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
30  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  *
33  * Please inquire about commercial licensing options at
34  * [email protected]
35  *
36  */
37 
38 /*
39  *  l2cap.c
40  *
41  *  Logical Link Control and Adaption Protocl (L2CAP)
42  *
43  *  Created by Matthias Ringwald on 5/16/09.
44  */
45 
46 #include "l2cap.h"
47 #include "hci.h"
48 #include "hci_dump.h"
49 #include "btstack_debug.h"
50 #include "btstack_event.h"
51 #include "btstack_memory.h"
52 
53 #include <stdarg.h>
54 #include <string.h>
55 
56 #include <stdio.h>
57 
58 // nr of buffered acl packets in outgoing queue to get max performance
59 #define NR_BUFFERED_ACL_PACKETS 3
60 
61 // used to cache l2cap rejects, echo, and informational requests
62 #define NR_PENDING_SIGNALING_RESPONSES 3
63 
64 // offsets for L2CAP SIGNALING COMMANDS
65 #define L2CAP_SIGNALING_COMMAND_CODE_OFFSET   0
66 #define L2CAP_SIGNALING_COMMAND_SIGID_OFFSET  1
67 #define L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET 2
68 #define L2CAP_SIGNALING_COMMAND_DATA_OFFSET   4
69 
70 // internal table
71 #define L2CAP_FIXED_CHANNEL_TABLE_INDEX_ATTRIBUTE_PROTOCOL 0
72 #define L2CAP_FIXED_CHANNEL_TABLE_INDEX_SECURITY_MANAGER_PROTOCOL  1
73 #define L2CAP_FIXED_CHANNEL_TABLE_INDEX_CONNECTIONLESS_CHANNEL 2
74 #define L2CAP_FIXED_CHANNEL_TABLE_SIZE (L2CAP_FIXED_CHANNEL_TABLE_INDEX_CONNECTIONLESS_CHANNEL+1)
75 
76 // prototypes
77 static void l2cap_finialize_channel_close(l2cap_channel_t *channel);
78 static inline l2cap_service_t * l2cap_get_service(uint16_t psm);
79 static void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status);
80 static void l2cap_emit_can_send_now(btstack_packet_handler_t packet_handler, uint16_t channel);
81 static void l2cap_emit_channel_closed(l2cap_channel_t *channel);
82 static void l2cap_emit_connection_request(l2cap_channel_t *channel);
83 static int  l2cap_channel_ready_for_open(l2cap_channel_t *channel);
84 static void l2cap_hci_event_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size);
85 static void l2cap_acl_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size );
86 static void l2cap_notify_channel_can_send(void);
87 
88 typedef struct l2cap_fixed_channel {
89     btstack_packet_handler_t callback;
90     uint8_t waiting_for_can_send_now;
91 } l2cap_fixed_channel_t;
92 
93 static btstack_linked_list_t l2cap_channels;
94 static btstack_linked_list_t l2cap_services;
95 static btstack_linked_list_t l2cap_le_channels;
96 static btstack_linked_list_t l2cap_le_services;
97 
98 // used to cache l2cap rejects, echo, and informational requests
99 static l2cap_signaling_response_t signaling_responses[NR_PENDING_SIGNALING_RESPONSES];
100 static int signaling_responses_pending;
101 
102 static uint8_t require_security_level2_for_outgoing_sdp;
103 
104 static btstack_packet_callback_registration_t hci_event_callback_registration;
105 
106 static btstack_packet_handler_t l2cap_event_packet_handler;
107 static l2cap_fixed_channel_t fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_SIZE];
108 
109 static uint16_t l2cap_fixed_channel_table_channel_id_for_index(int index){
110     switch (index){
111         case L2CAP_FIXED_CHANNEL_TABLE_INDEX_ATTRIBUTE_PROTOCOL:
112             return L2CAP_CID_ATTRIBUTE_PROTOCOL;
113         case L2CAP_FIXED_CHANNEL_TABLE_INDEX_SECURITY_MANAGER_PROTOCOL:
114             return L2CAP_CID_SECURITY_MANAGER_PROTOCOL;
115         case L2CAP_FIXED_CHANNEL_TABLE_INDEX_CONNECTIONLESS_CHANNEL:
116             return L2CAP_CID_CONNECTIONLESS_CHANNEL;
117         default:
118             return 0;
119     }
120 }
121 static int l2cap_fixed_channel_table_index_for_channel_id(uint16_t channel_id){
122     switch (channel_id){
123         case L2CAP_CID_ATTRIBUTE_PROTOCOL:
124             return L2CAP_FIXED_CHANNEL_TABLE_INDEX_ATTRIBUTE_PROTOCOL;
125         case L2CAP_CID_SECURITY_MANAGER_PROTOCOL:
126             return  L2CAP_FIXED_CHANNEL_TABLE_INDEX_SECURITY_MANAGER_PROTOCOL;
127         case L2CAP_CID_CONNECTIONLESS_CHANNEL:
128             return  L2CAP_FIXED_CHANNEL_TABLE_INDEX_CONNECTIONLESS_CHANNEL;
129         default:
130             return -1;
131         }
132 }
133 
134 static int l2cap_fixed_channel_table_index_is_le(int index){
135     if (index == L2CAP_CID_CONNECTIONLESS_CHANNEL) return 0;
136     return 1;
137 }
138 
139 void l2cap_init(void){
140     signaling_responses_pending = 0;
141 
142     l2cap_channels = NULL;
143     l2cap_services = NULL;
144     l2cap_le_services = NULL;
145     l2cap_le_channels = NULL;
146 
147     l2cap_event_packet_handler = NULL;
148     memset(fixed_channels, 0, sizeof(fixed_channels));
149 
150     require_security_level2_for_outgoing_sdp = 0;
151 
152     //
153     // register callback with HCI
154     //
155     hci_event_callback_registration.callback = &l2cap_hci_event_handler;
156     hci_add_event_handler(&hci_event_callback_registration);
157 
158     hci_register_acl_packet_handler(&l2cap_acl_handler);
159 
160     gap_connectable_control(0); // no services yet
161 }
162 
163 void l2cap_register_packet_handler(void (*handler)(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size)){
164     l2cap_event_packet_handler = handler;
165 }
166 
167 static void l2cap_dispatch_to_channel(l2cap_channel_t *channel, uint8_t type, uint8_t * data, uint16_t size){
168     (* (channel->packet_handler))(type, channel->local_cid, data, size);
169 }
170 
171 void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status) {
172     log_info("L2CAP_EVENT_CHANNEL_OPENED status 0x%x addr %s handle 0x%x psm 0x%x local_cid 0x%x remote_cid 0x%x local_mtu %u, remote_mtu %u, flush_timeout %u",
173              status, bd_addr_to_str(channel->address), channel->con_handle, channel->psm,
174              channel->local_cid, channel->remote_cid, channel->local_mtu, channel->remote_mtu, channel->flush_timeout);
175     uint8_t event[23];
176     event[0] = L2CAP_EVENT_CHANNEL_OPENED;
177     event[1] = sizeof(event) - 2;
178     event[2] = status;
179     reverse_bd_addr(channel->address, &event[3]);
180     little_endian_store_16(event,  9, channel->con_handle);
181     little_endian_store_16(event, 11, channel->psm);
182     little_endian_store_16(event, 13, channel->local_cid);
183     little_endian_store_16(event, 15, channel->remote_cid);
184     little_endian_store_16(event, 17, channel->local_mtu);
185     little_endian_store_16(event, 19, channel->remote_mtu);
186     little_endian_store_16(event, 21, channel->flush_timeout);
187     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
188     l2cap_dispatch_to_channel(channel, HCI_EVENT_PACKET, event, sizeof(event));
189 }
190 
191 void l2cap_emit_channel_closed(l2cap_channel_t *channel) {
192     log_info("L2CAP_EVENT_CHANNEL_CLOSED local_cid 0x%x", channel->local_cid);
193     uint8_t event[4];
194     event[0] = L2CAP_EVENT_CHANNEL_CLOSED;
195     event[1] = sizeof(event) - 2;
196     little_endian_store_16(event, 2, channel->local_cid);
197     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
198     l2cap_dispatch_to_channel(channel, HCI_EVENT_PACKET, event, sizeof(event));
199 }
200 
201 void l2cap_emit_connection_request(l2cap_channel_t *channel) {
202     log_info("L2CAP_EVENT_INCOMING_CONNECTION addr %s handle 0x%x psm 0x%x local_cid 0x%x remote_cid 0x%x",
203              bd_addr_to_str(channel->address), channel->con_handle,  channel->psm, channel->local_cid, channel->remote_cid);
204     uint8_t event[16];
205     event[0] = L2CAP_EVENT_INCOMING_CONNECTION;
206     event[1] = sizeof(event) - 2;
207     reverse_bd_addr(channel->address, &event[2]);
208     little_endian_store_16(event,  8, channel->con_handle);
209     little_endian_store_16(event, 10, channel->psm);
210     little_endian_store_16(event, 12, channel->local_cid);
211     little_endian_store_16(event, 14, channel->remote_cid);
212     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
213     l2cap_dispatch_to_channel(channel, HCI_EVENT_PACKET, event, sizeof(event));
214 }
215 
216 static void l2cap_emit_can_send_now(btstack_packet_handler_t packet_handler, uint16_t channel) {
217     log_info("L2CAP_EVENT_CHANNEL_CAN_SEND_NOW local_cid 0x%x", channel);
218     uint8_t event[4];
219     event[0] = L2CAP_EVENT_CAN_SEND_NOW;
220     event[1] = sizeof(event) - 2;
221     little_endian_store_16(event, 2, channel);
222     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
223     packet_handler(HCI_EVENT_PACKET, channel, event, sizeof(event));
224 }
225 
226 static void l2cap_emit_connection_parameter_update_response(hci_con_handle_t con_handle, uint16_t result){
227     uint8_t event[6];
228     event[0] = L2CAP_EVENT_CONNECTION_PARAMETER_UPDATE_RESPONSE;
229     event[1] = 4;
230     little_endian_store_16(event, 2, con_handle);
231     little_endian_store_16(event, 4, result);
232     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
233     if (!l2cap_event_packet_handler) return;
234     (*l2cap_event_packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
235 }
236 
237 static l2cap_channel_t * l2cap_get_channel_for_local_cid(uint16_t local_cid){
238     btstack_linked_list_iterator_t it;
239     btstack_linked_list_iterator_init(&it, &l2cap_channels);
240     while (btstack_linked_list_iterator_has_next(&it)){
241         l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
242         if ( channel->local_cid == local_cid) {
243             return channel;
244         }
245     }
246     return NULL;
247 }
248 
249 static l2cap_channel_t * l2cap_get_le_channel_for_address_and_addr_type(bd_addr_t address, bd_addr_type_t address_type){
250     btstack_linked_list_iterator_t it;
251     btstack_linked_list_iterator_init(&it, &l2cap_le_channels);
252     while (btstack_linked_list_iterator_has_next(&it)){
253         l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
254         if (channel->address_type != address_type)  continue;
255         if (bd_addr_cmp(channel->address, address)) continue;
256         return channel;
257     }
258     return NULL;
259 }
260 
261 ///
262 
263 void l2cap_request_can_send_now_event(uint16_t local_cid){
264     l2cap_channel_t *channel = l2cap_get_channel_for_local_cid(local_cid);
265     if (!channel) return;
266     channel->waiting_for_can_send_now = 1;
267     l2cap_notify_channel_can_send();
268 }
269 
270 void l2cap_request_can_send_fix_channel_now_event(hci_con_handle_t con_handle, uint16_t channel_id){
271     int index = l2cap_fixed_channel_table_index_for_channel_id(channel_id);
272     if (index < 0) return;
273     fixed_channels[index].waiting_for_can_send_now = 1;
274     l2cap_notify_channel_can_send();
275 }
276 
277 ///
278 
279 int  l2cap_can_send_packet_now(uint16_t local_cid){
280     l2cap_channel_t *channel = l2cap_get_channel_for_local_cid(local_cid);
281     if (!channel) return 0;
282     return hci_can_send_acl_packet_now(channel->con_handle);
283 }
284 
285 int  l2cap_can_send_prepared_packet_now(uint16_t local_cid){
286     l2cap_channel_t *channel = l2cap_get_channel_for_local_cid(local_cid);
287     if (!channel) return 0;
288     return hci_can_send_prepared_acl_packet_now(channel->con_handle);
289 }
290 
291 int  l2cap_can_send_fixed_channel_packet_now(hci_con_handle_t con_handle, uint16_t channel_id){
292     return hci_can_send_acl_packet_now(con_handle);
293 }
294 
295 ///
296 
297 uint16_t l2cap_get_remote_mtu_for_local_cid(uint16_t local_cid){
298     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
299     if (channel) {
300         return channel->remote_mtu;
301     }
302     return 0;
303 }
304 
305 static l2cap_channel_t * l2cap_channel_for_rtx_timer(btstack_timer_source_t * ts){
306     btstack_linked_list_iterator_t it;
307     btstack_linked_list_iterator_init(&it, &l2cap_channels);
308     while (btstack_linked_list_iterator_has_next(&it)){
309         l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
310         if ( &channel->rtx == ts) {
311             return channel;
312         }
313     }
314     return NULL;
315 }
316 
317 static void l2cap_rtx_timeout(btstack_timer_source_t * ts){
318     l2cap_channel_t * channel = l2cap_channel_for_rtx_timer(ts);
319     if (!channel) return;
320 
321     log_info("l2cap_rtx_timeout for local cid 0x%02x", channel->local_cid);
322 
323     // "When terminating the channel, it is not necessary to send a L2CAP_DisconnectReq
324     //  and enter WAIT_DISCONNECT state. Channels can be transitioned directly to the CLOSED state."
325     // notify client
326     l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_RTX_TIMEOUT);
327 
328     // discard channel
329     // no need to stop timer here, it is removed from list during timer callback
330     btstack_linked_list_remove(&l2cap_channels, (btstack_linked_item_t *) channel);
331     btstack_memory_l2cap_channel_free(channel);
332 }
333 
334 static void l2cap_stop_rtx(l2cap_channel_t * channel){
335     log_info("l2cap_stop_rtx for local cid 0x%02x", channel->local_cid);
336     btstack_run_loop_remove_timer(&channel->rtx);
337 }
338 
339 static void l2cap_start_rtx(l2cap_channel_t * channel){
340     l2cap_stop_rtx(channel);
341     log_info("l2cap_start_rtx for local cid 0x%02x", channel->local_cid);
342     btstack_run_loop_set_timer_handler(&channel->rtx, l2cap_rtx_timeout);
343     btstack_run_loop_set_timer(&channel->rtx, L2CAP_RTX_TIMEOUT_MS);
344     btstack_run_loop_add_timer(&channel->rtx);
345 }
346 
347 static void l2cap_start_ertx(l2cap_channel_t * channel){
348     log_info("l2cap_start_ertx for local cid 0x%02x", channel->local_cid);
349     l2cap_stop_rtx(channel);
350     btstack_run_loop_set_timer_handler(&channel->rtx, l2cap_rtx_timeout);
351     btstack_run_loop_set_timer(&channel->rtx, L2CAP_ERTX_TIMEOUT_MS);
352     btstack_run_loop_add_timer(&channel->rtx);
353 }
354 
355 void l2cap_require_security_level_2_for_outgoing_sdp(void){
356     require_security_level2_for_outgoing_sdp = 1;
357 }
358 
359 static int l2cap_security_level_0_allowed_for_PSM(uint16_t psm){
360     return (psm == PSM_SDP) && (!require_security_level2_for_outgoing_sdp);
361 }
362 
363 static int l2cap_send_signaling_packet(hci_con_handle_t handle, L2CAP_SIGNALING_COMMANDS cmd, uint8_t identifier, ...){
364 
365     if (!hci_can_send_acl_packet_now(handle)){
366         log_info("l2cap_send_signaling_packet, cannot send");
367         return BTSTACK_ACL_BUFFERS_FULL;
368     }
369 
370     // log_info("l2cap_send_signaling_packet type %u", cmd);
371     hci_reserve_packet_buffer();
372     uint8_t *acl_buffer = hci_get_outgoing_packet_buffer();
373     va_list argptr;
374     va_start(argptr, identifier);
375     uint16_t len = l2cap_create_signaling_classic(acl_buffer, handle, cmd, identifier, argptr);
376     va_end(argptr);
377     // log_info("l2cap_send_signaling_packet con %u!", handle);
378     return hci_send_acl_packet_buffer(len);
379 }
380 
381 #ifdef ENABLE_BLE
382 static int l2cap_send_le_signaling_packet(hci_con_handle_t handle, L2CAP_SIGNALING_COMMANDS cmd, uint8_t identifier, ...){
383 
384     if (!hci_can_send_acl_packet_now(handle)){
385         log_info("l2cap_send_signaling_packet, cannot send");
386         return BTSTACK_ACL_BUFFERS_FULL;
387     }
388 
389     // log_info("l2cap_send_signaling_packet type %u", cmd);
390     hci_reserve_packet_buffer();
391     uint8_t *acl_buffer = hci_get_outgoing_packet_buffer();
392     va_list argptr;
393     va_start(argptr, identifier);
394     uint16_t len = l2cap_create_signaling_le(acl_buffer, handle, cmd, identifier, argptr);
395     va_end(argptr);
396     // log_info("l2cap_send_signaling_packet con %u!", handle);
397     return hci_send_acl_packet_buffer(len);
398 }
399 #endif
400 
401 uint8_t *l2cap_get_outgoing_buffer(void){
402     return hci_get_outgoing_packet_buffer() + COMPLETE_L2CAP_HEADER; // 8 bytes
403 }
404 
405 int l2cap_reserve_packet_buffer(void){
406     return hci_reserve_packet_buffer();
407 }
408 
409 void l2cap_release_packet_buffer(void){
410     hci_release_packet_buffer();
411 }
412 
413 
414 int l2cap_send_prepared(uint16_t local_cid, uint16_t len){
415 
416     if (!hci_is_packet_buffer_reserved()){
417         log_error("l2cap_send_prepared called without reserving packet first");
418         return BTSTACK_ACL_BUFFERS_FULL;
419     }
420 
421     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
422     if (!channel) {
423         log_error("l2cap_send_prepared no channel for cid 0x%02x", local_cid);
424         return -1;   // TODO: define error
425     }
426 
427     if (!hci_can_send_prepared_acl_packet_now(channel->con_handle)){
428         log_info("l2cap_send_prepared cid 0x%02x, cannot send", local_cid);
429         return BTSTACK_ACL_BUFFERS_FULL;
430     }
431 
432     log_debug("l2cap_send_prepared cid 0x%02x, handle %u, 1 credit used", local_cid, channel->con_handle);
433 
434     uint8_t *acl_buffer = hci_get_outgoing_packet_buffer();
435 
436     int pb = hci_non_flushable_packet_boundary_flag_supported() ? 0x00 : 0x02;
437 
438     // 0 - Connection handle : PB=pb : BC=00
439     little_endian_store_16(acl_buffer, 0, channel->con_handle | (pb << 12) | (0 << 14));
440     // 2 - ACL length
441     little_endian_store_16(acl_buffer, 2,  len + 4);
442     // 4 - L2CAP packet length
443     little_endian_store_16(acl_buffer, 4,  len + 0);
444     // 6 - L2CAP channel DEST
445     little_endian_store_16(acl_buffer, 6, channel->remote_cid);
446     // send
447     int err = hci_send_acl_packet_buffer(len+8);
448 
449     return err;
450 }
451 
452 int l2cap_send_prepared_connectionless(hci_con_handle_t con_handle, uint16_t cid, uint16_t len){
453 
454     if (!hci_is_packet_buffer_reserved()){
455         log_error("l2cap_send_prepared_connectionless called without reserving packet first");
456         return BTSTACK_ACL_BUFFERS_FULL;
457     }
458 
459     if (!hci_can_send_prepared_acl_packet_now(con_handle)){
460         log_info("l2cap_send_prepared_connectionless handle 0x%02x, cid 0x%02x, cannot send", con_handle, cid);
461         return BTSTACK_ACL_BUFFERS_FULL;
462     }
463 
464     log_debug("l2cap_send_prepared_connectionless handle %u, cid 0x%02x", con_handle, cid);
465 
466     uint8_t *acl_buffer = hci_get_outgoing_packet_buffer();
467 
468     int pb = hci_non_flushable_packet_boundary_flag_supported() ? 0x00 : 0x02;
469 
470     // 0 - Connection handle : PB=pb : BC=00
471     little_endian_store_16(acl_buffer, 0, con_handle | (pb << 12) | (0 << 14));
472     // 2 - ACL length
473     little_endian_store_16(acl_buffer, 2,  len + 4);
474     // 4 - L2CAP packet length
475     little_endian_store_16(acl_buffer, 4,  len + 0);
476     // 6 - L2CAP channel DEST
477     little_endian_store_16(acl_buffer, 6, cid);
478     // send
479     int err = hci_send_acl_packet_buffer(len+8);
480 
481     return err;
482 }
483 
484 int l2cap_send(uint16_t local_cid, uint8_t *data, uint16_t len){
485 
486     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
487     if (!channel) {
488         log_error("l2cap_send no channel for cid 0x%02x", local_cid);
489         return -1;   // TODO: define error
490     }
491 
492     if (len > channel->remote_mtu){
493         log_error("l2cap_send cid 0x%02x, data length exceeds remote MTU.", local_cid);
494         return L2CAP_DATA_LEN_EXCEEDS_REMOTE_MTU;
495     }
496 
497     if (!hci_can_send_acl_packet_now(channel->con_handle)){
498         log_info("l2cap_send cid 0x%02x, cannot send", local_cid);
499         return BTSTACK_ACL_BUFFERS_FULL;
500     }
501 
502     hci_reserve_packet_buffer();
503     uint8_t *acl_buffer = hci_get_outgoing_packet_buffer();
504 
505     memcpy(&acl_buffer[8], data, len);
506 
507     return l2cap_send_prepared(local_cid, len);
508 }
509 
510 int l2cap_send_connectionless(hci_con_handle_t con_handle, uint16_t cid, uint8_t *data, uint16_t len){
511 
512     if (!hci_can_send_acl_packet_now(con_handle)){
513         log_info("l2cap_send cid 0x%02x, cannot send", cid);
514         return BTSTACK_ACL_BUFFERS_FULL;
515     }
516 
517     hci_reserve_packet_buffer();
518     uint8_t *acl_buffer = hci_get_outgoing_packet_buffer();
519 
520     memcpy(&acl_buffer[8], data, len);
521 
522     return l2cap_send_prepared_connectionless(con_handle, cid, len);
523 }
524 
525 int l2cap_send_echo_request(hci_con_handle_t con_handle, uint8_t *data, uint16_t len){
526     return l2cap_send_signaling_packet(con_handle, ECHO_REQUEST, 0x77, len, data);
527 }
528 
529 static inline void channelStateVarSetFlag(l2cap_channel_t *channel, L2CAP_CHANNEL_STATE_VAR flag){
530     channel->state_var = (L2CAP_CHANNEL_STATE_VAR) (channel->state_var | flag);
531 }
532 
533 static inline void channelStateVarClearFlag(l2cap_channel_t *channel, L2CAP_CHANNEL_STATE_VAR flag){
534     channel->state_var = (L2CAP_CHANNEL_STATE_VAR) (channel->state_var & ~flag);
535 }
536 
537 
538 
539 // MARK: L2CAP_RUN
540 // process outstanding signaling tasks
541 static void l2cap_run(void){
542 
543     // log_info("l2cap_run: entered");
544 
545     // check pending signaling responses
546     while (signaling_responses_pending){
547 
548         hci_con_handle_t handle = signaling_responses[0].handle;
549 
550         if (!hci_can_send_acl_packet_now(handle)) break;
551 
552         uint8_t  sig_id = signaling_responses[0].sig_id;
553         uint16_t infoType = signaling_responses[0].data;    // INFORMATION_REQUEST
554         uint16_t result   = signaling_responses[0].data;    // CONNECTION_REQUEST, COMMAND_REJECT
555         uint8_t  response_code = signaling_responses[0].code;
556 
557         // remove first item before sending (to avoid sending response mutliple times)
558         signaling_responses_pending--;
559         int i;
560         for (i=0; i < signaling_responses_pending; i++){
561             memcpy(&signaling_responses[i], &signaling_responses[i+1], sizeof(l2cap_signaling_response_t));
562         }
563 
564         switch (response_code){
565             case CONNECTION_REQUEST:
566                 l2cap_send_signaling_packet(handle, CONNECTION_RESPONSE, sig_id, 0, 0, result, 0);
567                 // also disconnect if result is 0x0003 - security blocked
568                 if (result == 0x0003){
569                     hci_disconnect_security_block(handle);
570                 }
571                 break;
572             case ECHO_REQUEST:
573                 l2cap_send_signaling_packet(handle, ECHO_RESPONSE, sig_id, 0, NULL);
574                 break;
575             case INFORMATION_REQUEST:
576                 switch (infoType){
577                     case 1: { // Connectionless MTU
578                         uint16_t connectionless_mtu = hci_max_acl_data_packet_length();
579                         l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, sizeof(connectionless_mtu), &connectionless_mtu);
580                         break;
581                     }
582                     case 2: { // Extended Features Supported
583                         // extended features request supported, features: fixed channels, unicast connectionless data reception
584                         uint32_t features = 0x280;
585                         l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, sizeof(features), &features);
586                         break;
587                     }
588                     case 3: { // Fixed Channels Supported
589                         uint8_t map[8];
590                         memset(map, 0, 8);
591                         map[0] = 0x06;  // L2CAP Signaling Channel (0x02) + Connectionless reception (0x04)
592                         l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, sizeof(map), &map);
593                         break;
594                     }
595                     default:
596                         // all other types are not supported
597                         l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 1, 0, NULL);
598                         break;
599                 }
600                 break;
601             case COMMAND_REJECT:
602                 l2cap_send_signaling_packet(handle, COMMAND_REJECT, sig_id, result, 0, NULL);
603 #ifdef ENABLE_BLE
604             case COMMAND_REJECT_LE:
605                 l2cap_send_le_signaling_packet(handle, COMMAND_REJECT, sig_id, result, 0, NULL);
606                 break;
607 #endif
608             default:
609                 // should not happen
610                 break;
611         }
612     }
613 
614     uint8_t  config_options[4];
615     btstack_linked_list_iterator_t it;
616     btstack_linked_list_iterator_init(&it, &l2cap_channels);
617     while (btstack_linked_list_iterator_has_next(&it)){
618 
619         l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
620         // log_info("l2cap_run: channel %p, state %u, var 0x%02x", channel, channel->state, channel->state_var);
621         switch (channel->state){
622 
623             case L2CAP_STATE_WAIT_INCOMING_SECURITY_LEVEL_UPDATE:
624             case L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT:
625                 if (!hci_can_send_acl_packet_now(channel->con_handle)) break;
626                 if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONN_RESP_PEND) {
627                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONN_RESP_PEND);
628                     l2cap_send_signaling_packet(channel->con_handle, CONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid, 1, 0);
629                 }
630                 break;
631 
632             case L2CAP_STATE_WILL_SEND_CREATE_CONNECTION:
633                 if (!hci_can_send_command_packet_now()) break;
634                 // send connection request - set state first
635                 channel->state = L2CAP_STATE_WAIT_CONNECTION_COMPLETE;
636                 // BD_ADDR, Packet_Type, Page_Scan_Repetition_Mode, Reserved, Clock_Offset, Allow_Role_Switch
637                 hci_send_cmd(&hci_create_connection, channel->address, hci_usable_acl_packet_types(), 0, 0, 0, 1);
638                 break;
639 
640             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE:
641                 if (!hci_can_send_acl_packet_now(channel->con_handle)) break;
642                 channel->state = L2CAP_STATE_INVALID;
643                 l2cap_send_signaling_packet(channel->con_handle, CONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid, channel->reason, 0);
644                 // discard channel - l2cap_finialize_channel_close without sending l2cap close event
645                 l2cap_stop_rtx(channel);
646                 btstack_linked_list_iterator_remove(&it);
647                 btstack_memory_l2cap_channel_free(channel);
648                 break;
649 
650             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT:
651                 if (!hci_can_send_acl_packet_now(channel->con_handle)) break;
652                 channel->state = L2CAP_STATE_CONFIG;
653                 channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
654                 l2cap_send_signaling_packet(channel->con_handle, CONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid, 0, 0);
655                 break;
656 
657             case L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST:
658                 if (!hci_can_send_acl_packet_now(channel->con_handle)) break;
659                 // success, start l2cap handshake
660                 channel->local_sig_id = l2cap_next_sig_id();
661                 channel->state = L2CAP_STATE_WAIT_CONNECT_RSP;
662                 l2cap_send_signaling_packet( channel->con_handle, CONNECTION_REQUEST, channel->local_sig_id, channel->psm, channel->local_cid);
663                 l2cap_start_rtx(channel);
664                 break;
665 
666             case L2CAP_STATE_CONFIG:
667                 if (!hci_can_send_acl_packet_now(channel->con_handle)) break;
668                 if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP){
669                     uint16_t flags = 0;
670                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP);
671                     if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_CONT) {
672                         flags = 1;
673                     } else {
674                         channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP);
675                     }
676                     if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_INVALID){
677                         l2cap_send_signaling_packet(channel->con_handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, flags, L2CAP_CONF_RESULT_UNKNOWN_OPTIONS, 0, NULL);
678                     } else if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_MTU){
679                         config_options[0] = 1; // MTU
680                         config_options[1] = 2; // len param
681                         little_endian_store_16( (uint8_t*)&config_options, 2, channel->remote_mtu);
682                         l2cap_send_signaling_packet(channel->con_handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, flags, 0, 4, &config_options);
683                         channelStateVarClearFlag(channel,L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_MTU);
684                     } else {
685                         l2cap_send_signaling_packet(channel->con_handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, flags, 0, 0, NULL);
686                     }
687                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_CONT);
688                 }
689                 else if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ){
690                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
691                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SENT_CONF_REQ);
692                     channel->local_sig_id = l2cap_next_sig_id();
693                     config_options[0] = 1; // MTU
694                     config_options[1] = 2; // len param
695                     little_endian_store_16( (uint8_t*)&config_options, 2, channel->local_mtu);
696                     l2cap_send_signaling_packet(channel->con_handle, CONFIGURE_REQUEST, channel->local_sig_id, channel->remote_cid, 0, 4, &config_options);
697                     l2cap_start_rtx(channel);
698                 }
699                 if (l2cap_channel_ready_for_open(channel)){
700                     channel->state = L2CAP_STATE_OPEN;
701                     l2cap_emit_channel_opened(channel, 0);  // success
702                 }
703                 break;
704 
705             case L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE:
706                 if (!hci_can_send_acl_packet_now(channel->con_handle)) break;
707                 channel->state = L2CAP_STATE_INVALID;
708                 l2cap_send_signaling_packet( channel->con_handle, DISCONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid);
709                 // we don't start an RTX timer for a disconnect - there's no point in closing the channel if the other side doesn't respond :)
710                 l2cap_finialize_channel_close(channel);  // -- remove from list
711                 break;
712 
713             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
714                 if (!hci_can_send_acl_packet_now(channel->con_handle)) break;
715                 channel->local_sig_id = l2cap_next_sig_id();
716                 channel->state = L2CAP_STATE_WAIT_DISCONNECT;
717                 l2cap_send_signaling_packet( channel->con_handle, DISCONNECTION_REQUEST, channel->local_sig_id, channel->remote_cid, channel->local_cid);
718                 break;
719             default:
720                 break;
721         }
722     }
723 
724 #ifdef ENABLE_BLE
725     btstack_linked_list_iterator_init(&it, &l2cap_le_channels);
726     while (btstack_linked_list_iterator_has_next(&it)){
727         l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
728         // log_info("l2cap_run: channel %p, state %u, var 0x%02x", channel, channel->state, channel->state_var);
729         switch (channel->state){
730             case L2CAP_STATE_WILL_SEND_LE_CONNECTION_REQUEST:
731                 if (!hci_can_send_acl_packet_now(channel->con_handle)) break;
732                 channel->state = L2CAP_STATE_WAIT_LE_CONNECTION_RESPONSE;
733                 // le psm, source cid, mtu, mps, initial credits
734                 l2cap_send_le_signaling_packet( channel->con_handle, LE_CREDIT_BASED_CONNECTION_REQUEST, channel->local_sig_id, channel->psm, channel->local_cid, 23, 23, 1);
735                 break;
736             default:
737                 break;
738         }
739     }
740 
741     // send l2cap con paramter update if necessary
742     hci_connections_get_iterator(&it);
743     while(btstack_linked_list_iterator_has_next(&it)){
744         hci_connection_t * connection = (hci_connection_t *) btstack_linked_list_iterator_next(&it);
745         if (connection->address_type != BD_ADDR_TYPE_LE_PUBLIC && connection->address_type != BD_ADDR_TYPE_LE_RANDOM) continue;
746         if (!hci_can_send_acl_packet_now(connection->con_handle)) continue;
747         switch (connection->le_con_parameter_update_state){
748             case CON_PARAMETER_UPDATE_SEND_REQUEST:
749                 connection->le_con_parameter_update_state = CON_PARAMETER_UPDATE_NONE;
750                 l2cap_send_le_signaling_packet(connection->con_handle, CONNECTION_PARAMETER_UPDATE_REQUEST, connection->le_con_param_update_identifier,
751                                                connection->le_conn_interval_min, connection->le_conn_interval_max, connection->le_conn_latency, connection->le_supervision_timeout);
752                 break;
753             case CON_PARAMETER_UPDATE_SEND_RESPONSE:
754                 connection->le_con_parameter_update_state = CON_PARAMETER_UPDATE_CHANGE_HCI_CON_PARAMETERS;
755                 l2cap_send_le_signaling_packet(connection->con_handle, CONNECTION_PARAMETER_UPDATE_RESPONSE, connection->le_con_param_update_identifier, 0);
756                 break;
757             case CON_PARAMETER_UPDATE_DENY:
758                 connection->le_con_parameter_update_state = CON_PARAMETER_UPDATE_NONE;
759                 l2cap_send_le_signaling_packet(connection->con_handle, CONNECTION_PARAMETER_UPDATE_RESPONSE, connection->le_con_param_update_identifier, 1);
760                 break;
761             default:
762                 break;
763         }
764 #if 0
765 void l2cap_le_run(void){
766     for all channels
767         switch(state):
768 
769     if outgoing transfer active
770         send next chunk
771         if done, notify app
772 }
773 #endif
774     }
775 #endif
776 
777     // log_info("l2cap_run: exit");
778 }
779 
780 uint16_t l2cap_max_mtu(void){
781     return HCI_ACL_PAYLOAD_SIZE - L2CAP_HEADER_SIZE;
782 }
783 
784 uint16_t l2cap_max_le_mtu(void){
785     return l2cap_max_mtu();
786 }
787 
788 static void l2cap_handle_connection_complete(hci_con_handle_t con_handle, l2cap_channel_t * channel){
789     if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
790         log_info("l2cap_handle_connection_complete expected state");
791         // success, start l2cap handshake
792         channel->con_handle = con_handle;
793         // check remote SSP feature first
794         channel->state = L2CAP_STATE_WAIT_REMOTE_SUPPORTED_FEATURES;
795     }
796 }
797 
798 #ifdef ENABLE_BLE
799 static void l2cap_handle_le_connection_complete(l2cap_channel_t * channel, uint8_t status, hci_con_handle_t con_handle){
800     if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
801         log_info("l2cap_le_handle_connection_complete expected state");
802         // TODO: bail if status != 0
803 
804         // success, start l2cap handshake
805         channel->con_handle = con_handle;
806         channel->state = L2CAP_STATE_WILL_SEND_LE_CONNECTION_REQUEST;
807     }
808 }
809 #endif
810 
811 
812 static void l2cap_handle_remote_supported_features_received(l2cap_channel_t * channel){
813     if (channel->state != L2CAP_STATE_WAIT_REMOTE_SUPPORTED_FEATURES) return;
814 
815     // we have been waiting for remote supported features, if both support SSP,
816     log_info("l2cap received remote supported features, sec_level_0_allowed for psm %u = %u", channel->psm, l2cap_security_level_0_allowed_for_PSM(channel->psm));
817     if (gap_ssp_supported_on_both_sides(channel->con_handle) && !l2cap_security_level_0_allowed_for_PSM(channel->psm)){
818         // request security level 2
819         channel->state = L2CAP_STATE_WAIT_OUTGOING_SECURITY_LEVEL_UPDATE;
820         gap_request_security_level(channel->con_handle, LEVEL_2);
821         return;
822     }
823     // fine, go ahead
824     channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST;
825 }
826 
827 static l2cap_channel_t * l2cap_create_channel_entry(btstack_packet_handler_t packet_handler, bd_addr_t address, bd_addr_type_t address_type,
828     uint16_t psm, uint16_t local_mtu, gap_security_level_t security_level){
829 
830     l2cap_channel_t * channel = btstack_memory_l2cap_channel_get();
831     if (!channel) {
832         return NULL;
833     }
834 
835      // Init memory (make valgrind happy)
836     memset(channel, 0, sizeof(l2cap_channel_t));
837 
838     // fill in
839     channel->packet_handler = packet_handler;
840     bd_addr_copy(channel->address, address);
841     channel->address_type = address_type;
842     channel->psm = psm;
843     channel->local_mtu  = local_mtu;
844     channel->remote_mtu = L2CAP_MINIMAL_MTU;
845     channel->required_security_level = security_level;
846 
847     //
848     channel->local_cid = l2cap_next_local_cid();
849     channel->con_handle = 0;
850 
851     // set initial state
852     channel->state = L2CAP_STATE_WILL_SEND_CREATE_CONNECTION;
853     channel->state_var = L2CAP_CHANNEL_STATE_VAR_NONE;
854     channel->remote_sig_id = L2CAP_SIG_ID_INVALID;
855     channel->local_sig_id = L2CAP_SIG_ID_INVALID;
856     return channel;
857 }
858 
859 /**
860  * @brief Creates L2CAP channel to the PSM of a remote device with baseband address. A new baseband connection will be initiated if necessary.
861  * @param packet_handler
862  * @param address
863  * @param psm
864  * @param mtu
865  * @param local_cid
866  */
867 
868 uint8_t l2cap_create_channel(btstack_packet_handler_t channel_packet_handler, bd_addr_t address, uint16_t psm, uint16_t local_mtu, uint16_t * out_local_cid){
869     log_info("L2CAP_CREATE_CHANNEL addr %s psm 0x%x mtu %u", bd_addr_to_str(address), psm, local_mtu);
870 
871     if (local_mtu > l2cap_max_mtu()) {
872         local_mtu = l2cap_max_mtu();
873     }
874 
875     l2cap_channel_t * channel = l2cap_create_channel_entry(channel_packet_handler, address, BD_ADDR_TYPE_CLASSIC, psm, local_mtu, LEVEL_0);
876     if (!channel) {
877         return BTSTACK_MEMORY_ALLOC_FAILED;
878     }
879 
880     // add to connections list
881     btstack_linked_list_add(&l2cap_channels, (btstack_linked_item_t *) channel);
882 
883     // store local_cid
884     if (out_local_cid){
885        *out_local_cid = channel->local_cid;
886     }
887 
888     // check if hci connection is already usable
889     hci_connection_t * conn = hci_connection_for_bd_addr_and_type(address, BD_ADDR_TYPE_CLASSIC);
890     if (conn){
891         log_info("l2cap_create_channel, hci connection already exists");
892         l2cap_handle_connection_complete(conn->con_handle, channel);
893         // check if remote supported fearures are already received
894         if (conn->bonding_flags & BONDING_RECEIVED_REMOTE_FEATURES) {
895             l2cap_handle_remote_supported_features_received(channel);
896         }
897     }
898 
899     l2cap_run();
900 
901     return 0;
902 }
903 
904 void
905 l2cap_disconnect(uint16_t local_cid, uint8_t reason){
906     log_info("L2CAP_DISCONNECT local_cid 0x%x reason 0x%x", local_cid, reason);
907     // find channel for local_cid
908     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
909     if (channel) {
910         channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST;
911     }
912     // process
913     l2cap_run();
914 }
915 
916 static void l2cap_handle_connection_failed_for_addr(bd_addr_t address, uint8_t status){
917     btstack_linked_list_iterator_t it;
918     btstack_linked_list_iterator_init(&it, &l2cap_channels);
919     while (btstack_linked_list_iterator_has_next(&it)){
920         l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
921         if ( bd_addr_cmp( channel->address, address) != 0) continue;
922         // channel for this address found
923         switch (channel->state){
924             case L2CAP_STATE_WAIT_CONNECTION_COMPLETE:
925             case L2CAP_STATE_WILL_SEND_CREATE_CONNECTION:
926                 // failure, forward error code
927                 l2cap_emit_channel_opened(channel, status);
928                 // discard channel
929                 l2cap_stop_rtx(channel);
930                 btstack_linked_list_iterator_remove(&it);
931                 btstack_memory_l2cap_channel_free(channel);
932                 break;
933             default:
934                 break;
935         }
936     }
937 }
938 
939 static void l2cap_handle_connection_success_for_addr(bd_addr_t address, hci_con_handle_t handle){
940     btstack_linked_list_iterator_t it;
941     btstack_linked_list_iterator_init(&it, &l2cap_channels);
942     while (btstack_linked_list_iterator_has_next(&it)){
943         l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
944         if ( ! bd_addr_cmp( channel->address, address) ){
945             l2cap_handle_connection_complete(handle, channel);
946         }
947     }
948     // process
949     l2cap_run();
950 }
951 
952 static void l2cap_notify_channel_can_send(void){
953     btstack_linked_list_iterator_t it;
954     btstack_linked_list_iterator_init(&it, &l2cap_channels);
955     while (btstack_linked_list_iterator_has_next(&it)){
956         l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
957         if (!channel->waiting_for_can_send_now) continue;
958         if (!hci_can_send_acl_packet_now(channel->con_handle)) continue;
959         channel->waiting_for_can_send_now = 0;
960         l2cap_emit_can_send_now(channel->packet_handler, channel->local_cid);
961     }
962 
963     int i;
964     for (i=0;i<L2CAP_FIXED_CHANNEL_TABLE_SIZE;i++){
965         if (!fixed_channels[i].callback) continue;
966         if (!fixed_channels[i].waiting_for_can_send_now) continue;
967         int can_send;
968         if (l2cap_fixed_channel_table_index_is_le(i)){
969             can_send = hci_can_send_acl_le_packet_now();
970         } else {
971             can_send = hci_can_send_acl_classic_packet_now();
972         }
973         if (!can_send) continue;
974         fixed_channels[i].waiting_for_can_send_now = 0;
975         l2cap_emit_can_send_now(fixed_channels[i].callback, l2cap_fixed_channel_table_channel_id_for_index(i));
976     }
977 }
978 
979 static void l2cap_hci_event_handler(uint8_t packet_type, uint16_t cid, uint8_t *packet, uint16_t size){
980 
981     bd_addr_t address;
982     hci_con_handle_t handle;
983     btstack_linked_list_iterator_t it;
984     int hci_con_used;
985 
986     switch(hci_event_packet_get_type(packet)){
987 
988         // handle connection complete events
989         case HCI_EVENT_CONNECTION_COMPLETE:
990             reverse_bd_addr(&packet[5], address);
991             if (packet[2] == 0){
992                 handle = little_endian_read_16(packet, 3);
993                 l2cap_handle_connection_success_for_addr(address, handle);
994             } else {
995                 l2cap_handle_connection_failed_for_addr(address, packet[2]);
996             }
997             break;
998 
999         // handle successful create connection cancel command
1000         case HCI_EVENT_COMMAND_COMPLETE:
1001             if (HCI_EVENT_IS_COMMAND_COMPLETE(packet, hci_create_connection_cancel)) {
1002                 if (packet[5] == 0){
1003                     reverse_bd_addr(&packet[6], address);
1004                     // CONNECTION TERMINATED BY LOCAL HOST (0X16)
1005                     l2cap_handle_connection_failed_for_addr(address, 0x16);
1006                 }
1007             }
1008             l2cap_run();    // try sending signaling packets first
1009             break;
1010 
1011         case HCI_EVENT_COMMAND_STATUS:
1012             l2cap_run();    // try sending signaling packets first
1013             break;
1014 
1015         // handle disconnection complete events
1016         case HCI_EVENT_DISCONNECTION_COMPLETE:
1017             // send l2cap disconnect events for all channels on this handle and free them
1018             handle = little_endian_read_16(packet, 3);
1019             btstack_linked_list_iterator_init(&it, &l2cap_channels);
1020             while (btstack_linked_list_iterator_has_next(&it)){
1021                 l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
1022                 if (channel->con_handle != handle) continue;
1023                 l2cap_emit_channel_closed(channel);
1024                 l2cap_stop_rtx(channel);
1025                 btstack_linked_list_iterator_remove(&it);
1026                 btstack_memory_l2cap_channel_free(channel);
1027             }
1028             break;
1029 
1030         // Notify channel packet handler if they can send now
1031         case HCI_EVENT_TRANSPORT_PACKET_SENT:
1032         case HCI_EVENT_NUMBER_OF_COMPLETED_PACKETS:
1033             l2cap_run();    // try sending signaling packets first
1034             l2cap_notify_channel_can_send();
1035             break;
1036 
1037         // HCI Connection Timeouts
1038         case L2CAP_EVENT_TIMEOUT_CHECK:
1039             handle = little_endian_read_16(packet, 2);
1040             if (gap_get_connection_type(handle) != GAP_CONNECTION_ACL) break;
1041             if (hci_authentication_active_for_handle(handle)) break;
1042             hci_con_used = 0;
1043             btstack_linked_list_iterator_init(&it, &l2cap_channels);
1044             while (btstack_linked_list_iterator_has_next(&it)){
1045                 l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
1046                 if (channel->con_handle != handle) continue;
1047                 hci_con_used = 1;
1048                 break;
1049             }
1050             if (hci_con_used) break;
1051             if (!hci_can_send_command_packet_now()) break;
1052             hci_send_cmd(&hci_disconnect, handle, 0x13); // remote closed connection
1053             break;
1054 
1055         case HCI_EVENT_READ_REMOTE_SUPPORTED_FEATURES_COMPLETE:
1056             handle = little_endian_read_16(packet, 3);
1057             btstack_linked_list_iterator_init(&it, &l2cap_channels);
1058             while (btstack_linked_list_iterator_has_next(&it)){
1059                 l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
1060                 if (channel->con_handle != handle) continue;
1061                 l2cap_handle_remote_supported_features_received(channel);
1062                 break;
1063             }
1064             break;
1065 
1066 #ifdef ENABLE_BLE
1067         case HCI_EVENT_LE_META:
1068             switch (packet[2]){
1069                 int addr_type;
1070                 l2cap_channel_t * channel;
1071                 case HCI_SUBEVENT_LE_CONNECTION_COMPLETE:
1072                     // Connection management
1073                     reverse_bd_addr(&packet[8], address);
1074                     addr_type = (bd_addr_type_t)packet[7];
1075                     log_info("L2CAP - LE Connection_complete (status=%u) type %u, %s", packet[3], addr_type, bd_addr_to_str(address));
1076                     // get l2cap_channel
1077                     // also pass in status
1078                     channel = l2cap_get_le_channel_for_address_and_addr_type(address, addr_type);
1079                     if (!channel) break;
1080                     l2cap_handle_le_connection_complete(channel, packet[3], little_endian_read_16(packet, 4));
1081                     break;
1082                 default:
1083                     break;
1084             }
1085             break;
1086 #endif
1087 
1088         case GAP_EVENT_SECURITY_LEVEL:
1089             handle = little_endian_read_16(packet, 2);
1090             log_info("l2cap - security level update");
1091             btstack_linked_list_iterator_init(&it, &l2cap_channels);
1092             while (btstack_linked_list_iterator_has_next(&it)){
1093                 l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
1094                 if (channel->con_handle != handle) continue;
1095 
1096                 log_info("l2cap - state %u", channel->state);
1097 
1098                 gap_security_level_t actual_level = (gap_security_level_t) packet[4];
1099                 gap_security_level_t required_level = channel->required_security_level;
1100 
1101                 switch (channel->state){
1102                     case L2CAP_STATE_WAIT_INCOMING_SECURITY_LEVEL_UPDATE:
1103                         if (actual_level >= required_level){
1104                             channel->state = L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT;
1105                             l2cap_emit_connection_request(channel);
1106                         } else {
1107                             channel->reason = 0x0003; // security block
1108                             channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE;
1109                         }
1110                         break;
1111 
1112                     case L2CAP_STATE_WAIT_OUTGOING_SECURITY_LEVEL_UPDATE:
1113                         if (actual_level >= required_level){
1114                             channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST;
1115                         } else {
1116                             // disconnnect, authentication not good enough
1117                             hci_disconnect_security_block(handle);
1118                         }
1119                         break;
1120 
1121                     default:
1122                         break;
1123                 }
1124             }
1125             break;
1126 
1127         default:
1128             break;
1129     }
1130 
1131     l2cap_run();
1132 }
1133 
1134 static void l2cap_handle_disconnect_request(l2cap_channel_t *channel, uint16_t identifier){
1135     channel->remote_sig_id = identifier;
1136     channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE;
1137     l2cap_run();
1138 }
1139 
1140 static void l2cap_register_signaling_response(hci_con_handle_t handle, uint8_t code, uint8_t sig_id, uint16_t data){
1141     // Vol 3, Part A, 4.3: "The DCID and SCID fields shall be ignored when the result field indi- cates the connection was refused."
1142     if (signaling_responses_pending < NR_PENDING_SIGNALING_RESPONSES) {
1143         signaling_responses[signaling_responses_pending].handle = handle;
1144         signaling_responses[signaling_responses_pending].code = code;
1145         signaling_responses[signaling_responses_pending].sig_id = sig_id;
1146         signaling_responses[signaling_responses_pending].data = data;
1147         signaling_responses_pending++;
1148         l2cap_run();
1149     }
1150 }
1151 
1152 static void l2cap_handle_connection_request(hci_con_handle_t handle, uint8_t sig_id, uint16_t psm, uint16_t source_cid){
1153 
1154     // log_info("l2cap_handle_connection_request for handle %u, psm %u cid 0x%02x", handle, psm, source_cid);
1155     l2cap_service_t *service = l2cap_get_service(psm);
1156     if (!service) {
1157         // 0x0002 PSM not supported
1158         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0002);
1159         return;
1160     }
1161 
1162     hci_connection_t * hci_connection = hci_connection_for_handle( handle );
1163     if (!hci_connection) {
1164         //
1165         log_error("no hci_connection for handle %u", handle);
1166         return;
1167     }
1168 
1169     // alloc structure
1170     // log_info("l2cap_handle_connection_request register channel");
1171     l2cap_channel_t * channel = l2cap_create_channel_entry(service->packet_handler, hci_connection->address, BD_ADDR_TYPE_CLASSIC,
1172     psm, service->mtu, service->required_security_level);
1173     if (!channel){
1174         // 0x0004 No resources available
1175         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0004);
1176         return;
1177     }
1178 
1179     channel->con_handle = handle;
1180     channel->remote_cid = source_cid;
1181     channel->remote_sig_id = sig_id;
1182 
1183     // limit local mtu to max acl packet length - l2cap header
1184     if (channel->local_mtu > l2cap_max_mtu()) {
1185         channel->local_mtu = l2cap_max_mtu();
1186     }
1187 
1188     // set initial state
1189     channel->state =     L2CAP_STATE_WAIT_INCOMING_SECURITY_LEVEL_UPDATE;
1190     channel->state_var = L2CAP_CHANNEL_STATE_VAR_SEND_CONN_RESP_PEND;
1191 
1192     // add to connections list
1193     btstack_linked_list_add(&l2cap_channels, (btstack_linked_item_t *) channel);
1194 
1195     // assert security requirements
1196     gap_request_security_level(handle, channel->required_security_level);
1197 }
1198 
1199 void l2cap_accept_connection(uint16_t local_cid){
1200     log_info("L2CAP_ACCEPT_CONNECTION local_cid 0x%x", local_cid);
1201     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
1202     if (!channel) {
1203         log_error("l2cap_accept_connection called but local_cid 0x%x not found", local_cid);
1204         return;
1205     }
1206 
1207     channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT;
1208 
1209     // process
1210     l2cap_run();
1211 }
1212 
1213 void l2cap_decline_connection(uint16_t local_cid){
1214     log_info("L2CAP_DECLINE_CONNECTION local_cid 0x%x", local_cid);
1215     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid( local_cid);
1216     if (!channel) {
1217         log_error( "l2cap_decline_connection called but local_cid 0x%x not found", local_cid);
1218         return;
1219     }
1220     channel->state  = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE;
1221     channel->reason = 0x04; // no resources available
1222     l2cap_run();
1223 }
1224 
1225 static void l2cap_signaling_handle_configure_request(l2cap_channel_t *channel, uint8_t *command){
1226 
1227     channel->remote_sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
1228 
1229     uint16_t flags = little_endian_read_16(command, 6);
1230     if (flags & 1) {
1231         channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_CONT);
1232     }
1233 
1234     // accept the other's configuration options
1235     uint16_t end_pos = 4 + little_endian_read_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
1236     uint16_t pos     = 8;
1237     while (pos < end_pos){
1238         uint8_t option_hint = command[pos] >> 7;
1239         uint8_t option_type = command[pos] & 0x7f;
1240         log_info("l2cap cid %u, hint %u, type %u", channel->local_cid, option_hint, option_type);
1241         pos++;
1242         uint8_t length = command[pos++];
1243         // MTU { type(8): 1, len(8):2, MTU(16) }
1244         if (option_type == 1 && length == 2){
1245             channel->remote_mtu = little_endian_read_16(command, pos);
1246             // log_info("l2cap cid 0x%02x, remote mtu %u", channel->local_cid, channel->remote_mtu);
1247             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_MTU);
1248         }
1249         // Flush timeout { type(8):2, len(8): 2, Flush Timeout(16)}
1250         if (option_type == 2 && length == 2){
1251             channel->flush_timeout = little_endian_read_16(command, pos);
1252         }
1253         // check for unknown options
1254         if (option_hint == 0 && (option_type == 0 || option_type >= 0x07)){
1255             log_info("l2cap cid %u, unknown options", channel->local_cid);
1256             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_INVALID);
1257         }
1258         pos += length;
1259     }
1260 }
1261 
1262 static int l2cap_channel_ready_for_open(l2cap_channel_t *channel){
1263     // log_info("l2cap_channel_ready_for_open 0x%02x", channel->state_var);
1264     if ((channel->state_var & L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_RSP) == 0) return 0;
1265     if ((channel->state_var & L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP) == 0) return 0;
1266     // addition check that fixes re-entrance issue causing l2cap event channel opened twice
1267     if (channel->state == L2CAP_STATE_OPEN) return 0;
1268     return 1;
1269 }
1270 
1271 
1272 static void l2cap_signaling_handler_channel(l2cap_channel_t *channel, uint8_t *command){
1273 
1274     uint8_t  code       = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
1275     uint8_t  identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
1276     uint16_t result = 0;
1277 
1278     log_info("L2CAP signaling handler code %u, state %u", code, channel->state);
1279 
1280     // handle DISCONNECT REQUESTS seperately
1281     if (code == DISCONNECTION_REQUEST){
1282         switch (channel->state){
1283             case L2CAP_STATE_CONFIG:
1284             case L2CAP_STATE_OPEN:
1285             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
1286             case L2CAP_STATE_WAIT_DISCONNECT:
1287                 l2cap_handle_disconnect_request(channel, identifier);
1288                 break;
1289 
1290             default:
1291                 // ignore in other states
1292                 break;
1293         }
1294         return;
1295     }
1296 
1297     // @STATEMACHINE(l2cap)
1298     switch (channel->state) {
1299 
1300         case L2CAP_STATE_WAIT_CONNECT_RSP:
1301             switch (code){
1302                 case CONNECTION_RESPONSE:
1303                     l2cap_stop_rtx(channel);
1304                     result = little_endian_read_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
1305                     switch (result) {
1306                         case 0:
1307                             // successful connection
1308                             channel->remote_cid = little_endian_read_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
1309                             channel->state = L2CAP_STATE_CONFIG;
1310                             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
1311                             break;
1312                         case 1:
1313                             // connection pending. get some coffee, but start the ERTX
1314                             l2cap_start_ertx(channel);
1315                             break;
1316                         default:
1317                             // channel closed
1318                             channel->state = L2CAP_STATE_CLOSED;
1319                             // map l2cap connection response result to BTstack status enumeration
1320                             l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result);
1321 
1322                             // drop link key if security block
1323                             if (L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result == L2CAP_CONNECTION_RESPONSE_RESULT_REFUSED_SECURITY){
1324                                 gap_drop_link_key_for_bd_addr(channel->address);
1325                             }
1326 
1327                             // discard channel
1328                             btstack_linked_list_remove(&l2cap_channels, (btstack_linked_item_t *) channel);
1329                             btstack_memory_l2cap_channel_free(channel);
1330                             break;
1331                     }
1332                     break;
1333 
1334                 default:
1335                     //@TODO: implement other signaling packets
1336                     break;
1337             }
1338             break;
1339 
1340         case L2CAP_STATE_CONFIG:
1341             result = little_endian_read_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
1342             switch (code) {
1343                 case CONFIGURE_REQUEST:
1344                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP);
1345                     l2cap_signaling_handle_configure_request(channel, command);
1346                     if (!(channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_CONT)){
1347                         // only done if continuation not set
1348                         channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_REQ);
1349                     }
1350                     break;
1351                 case CONFIGURE_RESPONSE:
1352                     l2cap_stop_rtx(channel);
1353                     switch (result){
1354                         case 0: // success
1355                             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_RSP);
1356                             break;
1357                         case 4: // pending
1358                             l2cap_start_ertx(channel);
1359                             break;
1360                         default:
1361                             // retry on negative result
1362                             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
1363                             break;
1364                     }
1365                     break;
1366                 default:
1367                     break;
1368             }
1369             if (l2cap_channel_ready_for_open(channel)){
1370                 // for open:
1371                 channel->state = L2CAP_STATE_OPEN;
1372                 l2cap_emit_channel_opened(channel, 0);
1373             }
1374             break;
1375 
1376         case L2CAP_STATE_WAIT_DISCONNECT:
1377             switch (code) {
1378                 case DISCONNECTION_RESPONSE:
1379                     l2cap_finialize_channel_close(channel);
1380                     break;
1381                 default:
1382                     //@TODO: implement other signaling packets
1383                     break;
1384             }
1385             break;
1386 
1387         case L2CAP_STATE_CLOSED:
1388             // @TODO handle incoming requests
1389             break;
1390 
1391         case L2CAP_STATE_OPEN:
1392             //@TODO: implement other signaling packets, e.g. re-configure
1393             break;
1394         default:
1395             break;
1396     }
1397     // log_info("new state %u", channel->state);
1398 }
1399 
1400 
1401 static void l2cap_signaling_handler_dispatch( hci_con_handle_t handle, uint8_t * command){
1402 
1403     // get code, signalind identifier and command len
1404     uint8_t code   = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
1405     uint8_t sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
1406 
1407     // not for a particular channel, and not CONNECTION_REQUEST, ECHO_[REQUEST|RESPONSE], INFORMATION_REQUEST
1408     if (code < 1 || code == ECHO_RESPONSE || code > INFORMATION_REQUEST){
1409         l2cap_register_signaling_response(handle, COMMAND_REJECT, sig_id, L2CAP_REJ_CMD_UNKNOWN);
1410         return;
1411     }
1412 
1413     // general commands without an assigned channel
1414     switch(code) {
1415 
1416         case CONNECTION_REQUEST: {
1417             uint16_t psm =        little_endian_read_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
1418             uint16_t source_cid = little_endian_read_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+2);
1419             l2cap_handle_connection_request(handle, sig_id, psm, source_cid);
1420             return;
1421         }
1422 
1423         case ECHO_REQUEST:
1424             l2cap_register_signaling_response(handle, code, sig_id, 0);
1425             return;
1426 
1427         case INFORMATION_REQUEST: {
1428             uint16_t infoType = little_endian_read_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
1429             l2cap_register_signaling_response(handle, code, sig_id, infoType);
1430             return;
1431         }
1432 
1433         default:
1434             break;
1435     }
1436 
1437 
1438     // Get potential destination CID
1439     uint16_t dest_cid = little_endian_read_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
1440 
1441     // Find channel for this sig_id and connection handle
1442     btstack_linked_list_iterator_t it;
1443     btstack_linked_list_iterator_init(&it, &l2cap_channels);
1444     while (btstack_linked_list_iterator_has_next(&it)){
1445         l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
1446         if (channel->con_handle != handle) continue;
1447         if (code & 1) {
1448             // match odd commands (responses) by previous signaling identifier
1449             if (channel->local_sig_id == sig_id) {
1450                 l2cap_signaling_handler_channel(channel, command);
1451                 break;
1452             }
1453         } else {
1454             // match even commands (requests) by local channel id
1455             if (channel->local_cid == dest_cid) {
1456                 l2cap_signaling_handler_channel(channel, command);
1457                 break;
1458             }
1459         }
1460     }
1461 }
1462 
1463 // @returns valid
1464 static int l2cap_le_signaling_handler_dispatch(hci_con_handle_t handle, uint8_t * command, uint8_t sig_id){
1465     uint16_t result;
1466     uint8_t event[10];
1467 
1468     switch (command[0]){
1469 
1470         case CONNECTION_PARAMETER_UPDATE_RESPONSE:
1471             result = little_endian_read_16(command, 4);
1472             l2cap_emit_connection_parameter_update_response(handle, result);
1473             break;
1474 
1475         case CONNECTION_PARAMETER_UPDATE_REQUEST:
1476             hci_connection_t * connection = hci_connection_for_handle(handle);
1477             if (connection){
1478                 if (connection->role != HCI_ROLE_MASTER){
1479                     // reject command without notifying upper layer when not in master role
1480                     return 0;
1481                 }
1482                 int update_parameter = 1;
1483                 le_connection_parameter_range_t existing_range;
1484                 gap_get_connection_parameter_range(&existing_range);
1485                 uint16_t le_conn_interval_min = little_endian_read_16(command,8);
1486                 uint16_t le_conn_interval_max = little_endian_read_16(command,10);
1487                 uint16_t le_conn_latency = little_endian_read_16(command,12);
1488                 uint16_t le_supervision_timeout = little_endian_read_16(command,14);
1489 
1490                 if (le_conn_interval_min < existing_range.le_conn_interval_min) update_parameter = 0;
1491                 if (le_conn_interval_max > existing_range.le_conn_interval_max) update_parameter = 0;
1492 
1493                 if (le_conn_latency < existing_range.le_conn_latency_min) update_parameter = 0;
1494                 if (le_conn_latency > existing_range.le_conn_latency_max) update_parameter = 0;
1495 
1496                 if (le_supervision_timeout < existing_range.le_supervision_timeout_min) update_parameter = 0;
1497                 if (le_supervision_timeout > existing_range.le_supervision_timeout_max) update_parameter = 0;
1498 
1499                 if (update_parameter){
1500                     connection->le_con_parameter_update_state = CON_PARAMETER_UPDATE_SEND_RESPONSE;
1501                     connection->le_conn_interval_min = le_conn_interval_min;
1502                     connection->le_conn_interval_max = le_conn_interval_max;
1503                     connection->le_conn_latency = le_conn_latency;
1504                     connection->le_supervision_timeout = le_supervision_timeout;
1505                 } else {
1506                     connection->le_con_parameter_update_state = CON_PARAMETER_UPDATE_DENY;
1507                 }
1508                 connection->le_con_param_update_identifier = sig_id;
1509             }
1510 
1511             if (!l2cap_event_packet_handler) break;
1512 
1513             event[0] = L2CAP_EVENT_CONNECTION_PARAMETER_UPDATE_REQUEST;
1514             event[1] = 8;
1515             memcpy(&event[2], &command[4], 8);
1516             hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
1517             (*l2cap_event_packet_handler)( HCI_EVENT_PACKET, 0, event, sizeof(event));
1518             break;
1519 
1520         default:
1521             // command unknown -> reject command
1522             return 0;
1523     }
1524     return 1;
1525 }
1526 
1527 static void l2cap_acl_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size ){
1528 
1529     // Get Channel ID
1530     uint16_t channel_id = READ_L2CAP_CHANNEL_ID(packet);
1531     uint8_t sig_id;
1532     hci_con_handle_t handle = READ_ACL_CONNECTION_HANDLE(packet);
1533     int valid;
1534 
1535     switch (channel_id) {
1536 
1537         case L2CAP_CID_SIGNALING: {
1538             uint16_t command_offset = 8;
1539             while (command_offset < size) {
1540 
1541                 // handle signaling commands
1542                 l2cap_signaling_handler_dispatch(handle, &packet[command_offset]);
1543 
1544                 // increment command_offset
1545                 command_offset += L2CAP_SIGNALING_COMMAND_DATA_OFFSET + little_endian_read_16(packet, command_offset + L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
1546             }
1547             break;
1548         }
1549 
1550         case L2CAP_CID_SIGNALING_LE:
1551             sig_id = packet[COMPLETE_L2CAP_HEADER + 1];
1552             valid  = l2cap_le_signaling_handler_dispatch(handle, &packet[COMPLETE_L2CAP_HEADER], sig_id);
1553             if (!valid){
1554                 l2cap_register_signaling_response(handle, COMMAND_REJECT_LE, sig_id, L2CAP_REJ_CMD_UNKNOWN);
1555             }
1556             break;
1557 
1558         case L2CAP_CID_ATTRIBUTE_PROTOCOL:
1559             if (fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_INDEX_ATTRIBUTE_PROTOCOL].callback) {
1560                 (*fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_INDEX_ATTRIBUTE_PROTOCOL].callback)(ATT_DATA_PACKET, handle, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1561             }
1562             break;
1563 
1564         case L2CAP_CID_SECURITY_MANAGER_PROTOCOL:
1565             if (fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_INDEX_SECURITY_MANAGER_PROTOCOL].callback) {
1566                 (*fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_INDEX_SECURITY_MANAGER_PROTOCOL].callback)(SM_DATA_PACKET, handle, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1567             }
1568             break;
1569 
1570         case L2CAP_CID_CONNECTIONLESS_CHANNEL:
1571             if (fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_INDEX_CONNECTIONLESS_CHANNEL].callback) {
1572                 (*fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_INDEX_CONNECTIONLESS_CHANNEL].callback)(UCD_DATA_PACKET, handle, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1573             }
1574             break;
1575 
1576         default: {
1577             // Find channel for this channel_id and connection handle
1578             l2cap_channel_t * l2cap_channel = l2cap_get_channel_for_local_cid(channel_id);
1579             if (l2cap_channel) {
1580                 l2cap_dispatch_to_channel(l2cap_channel, L2CAP_DATA_PACKET, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1581             }
1582             break;
1583         }
1584     }
1585 
1586     l2cap_run();
1587 }
1588 
1589 // finalize closed channel - l2cap_handle_disconnect_request & DISCONNECTION_RESPONSE
1590 void l2cap_finialize_channel_close(l2cap_channel_t * channel){
1591     channel->state = L2CAP_STATE_CLOSED;
1592     l2cap_emit_channel_closed(channel);
1593     // discard channel
1594     l2cap_stop_rtx(channel);
1595     btstack_linked_list_remove(&l2cap_channels, (btstack_linked_item_t *) channel);
1596     btstack_memory_l2cap_channel_free(channel);
1597 }
1598 
1599 static l2cap_service_t * l2cap_get_service_internal(btstack_linked_list_t * services, uint16_t psm){
1600     btstack_linked_list_iterator_t it;
1601     btstack_linked_list_iterator_init(&it, services);
1602     while (btstack_linked_list_iterator_has_next(&it)){
1603         l2cap_service_t * service = (l2cap_service_t *) btstack_linked_list_iterator_next(&it);
1604         if ( service->psm == psm){
1605             return service;
1606         };
1607     }
1608     return NULL;
1609 }
1610 
1611 static inline l2cap_service_t * l2cap_get_service(uint16_t psm){
1612     return l2cap_get_service_internal(&l2cap_services, psm);
1613 }
1614 
1615 
1616 uint8_t l2cap_register_service(btstack_packet_handler_t service_packet_handler, uint16_t psm, uint16_t mtu, gap_security_level_t security_level){
1617 
1618     log_info("L2CAP_REGISTER_SERVICE psm 0x%x mtu %u", psm, mtu);
1619 
1620     // check for alread registered psm
1621     l2cap_service_t *service = l2cap_get_service(psm);
1622     if (service) {
1623         log_error("l2cap_register_service: PSM %u already registered", psm);
1624         return L2CAP_SERVICE_ALREADY_REGISTERED;
1625     }
1626 
1627     // alloc structure
1628     service = btstack_memory_l2cap_service_get();
1629     if (!service) {
1630         log_error("l2cap_register_service: no memory for l2cap_service_t");
1631         return BTSTACK_MEMORY_ALLOC_FAILED;
1632     }
1633 
1634     // fill in
1635     service->psm = psm;
1636     service->mtu = mtu;
1637     service->packet_handler = service_packet_handler;
1638     service->required_security_level = security_level;
1639 
1640     // add to services list
1641     btstack_linked_list_add(&l2cap_services, (btstack_linked_item_t *) service);
1642 
1643     // enable page scan
1644     gap_connectable_control(1);
1645 
1646     return 0;
1647 }
1648 
1649 uint8_t l2cap_unregister_service(uint16_t psm){
1650 
1651     log_info("L2CAP_UNREGISTER_SERVICE psm 0x%x", psm);
1652 
1653     l2cap_service_t *service = l2cap_get_service(psm);
1654     if (!service) return L2CAP_SERVICE_DOES_NOT_EXIST;
1655     btstack_linked_list_remove(&l2cap_services, (btstack_linked_item_t *) service);
1656     btstack_memory_l2cap_service_free(service);
1657 
1658     // disable page scan when no services registered
1659     if (btstack_linked_list_empty(&l2cap_services)) {
1660         gap_connectable_control(0);
1661     }
1662     return 0;
1663 }
1664 
1665 // Bluetooth 4.0 - allows to register handler for Attribute Protocol and Security Manager Protocol
1666 void l2cap_register_fixed_channel(btstack_packet_handler_t the_packet_handler, uint16_t channel_id) {
1667     int index = l2cap_fixed_channel_table_index_for_channel_id(channel_id);
1668     if (index < 0) return;
1669     fixed_channels[index].callback = the_packet_handler;
1670 }
1671 
1672 #ifdef ENABLE_BLE
1673 
1674 static inline l2cap_service_t * l2cap_le_get_service(uint16_t psm){
1675     return l2cap_get_service_internal(&l2cap_le_services, psm);
1676 }
1677 
1678 uint8_t l2cap_le_register_service(btstack_packet_handler_t packet_handler, uint16_t psm, gap_security_level_t security_level){
1679 
1680     log_info("L2CAP_LE_REGISTER_SERVICE psm 0x%x", psm);
1681 
1682     // check for alread registered psm
1683     l2cap_service_t *service = l2cap_le_get_service(psm);
1684     if (service) {
1685         return L2CAP_SERVICE_ALREADY_REGISTERED;
1686     }
1687 
1688     // alloc structure
1689     service = btstack_memory_l2cap_service_get();
1690     if (!service) {
1691         log_error("l2cap_register_service_internal: no memory for l2cap_service_t");
1692         return BTSTACK_MEMORY_ALLOC_FAILED;
1693     }
1694 
1695     // fill in
1696     service->psm = psm;
1697     service->mtu = 0;
1698     service->packet_handler = packet_handler;
1699     service->required_security_level = security_level;
1700 
1701     // add to services list
1702     btstack_linked_list_add(&l2cap_le_services, (btstack_linked_item_t *) service);
1703 
1704     // done
1705     return 0;
1706 }
1707 
1708 uint8_t l2cap_le_unregister_service(uint16_t psm) {
1709     log_info("L2CAP_LE_UNREGISTER_SERVICE psm 0x%x", psm);
1710     l2cap_service_t *service = l2cap_le_get_service(psm);
1711     if (!service) return L2CAP_SERVICE_DOES_NOT_EXIST;
1712 
1713     btstack_linked_list_remove(&l2cap_le_services, (btstack_linked_item_t *) service);
1714     btstack_memory_l2cap_service_free(service);
1715     return 0;
1716 }
1717 
1718 uint8_t l2cap_le_accept_connection(uint16_t local_cid, uint8_t * receive_sdu_buffer, uint16_t mtu, uint16_t initial_credits){
1719     // get connection
1720     // bail if missing
1721     // set mtu and receive buffer
1722     // check state
1723     // set state accept connection
1724     // l2cap_le_run()
1725     return 0;
1726 }
1727 
1728 /**
1729  * @brief Deny incoming LE Data Channel connection due to resource constraints
1730  * @param local_cid             L2CAP LE Data Channel Identifier
1731  */
1732 
1733 uint8_t l2cap_le_decline_connection(uint16_t local_cid){
1734     // get connection
1735     // bail if missing
1736     // check state
1737     // set state decline connection
1738     // l2cap_le_run()
1739     return 0;
1740 }
1741 
1742 uint8_t l2cap_le_create_channel(btstack_packet_handler_t packet_handler, bd_addr_t address, bd_addr_type_t address_type,
1743     uint16_t psm, uint8_t * receive_sdu_buffer, uint16_t mtu, uint16_t initial_credits, gap_security_level_t security_level,
1744     uint16_t * out_local_cid) {
1745 
1746     log_info("L2CAP_LE_CREATE_CHANNEL addr %s psm 0x%x mtu %u", bd_addr_to_str(address), psm, mtu);
1747 
1748     l2cap_channel_t * channel = l2cap_create_channel_entry(packet_handler, address, address_type, psm, mtu, LEVEL_0);
1749     if (!channel) {
1750         return BTSTACK_MEMORY_ALLOC_FAILED;
1751     }
1752 
1753     // store local_cid
1754     if (out_local_cid){
1755        *out_local_cid = channel->local_cid;
1756     }
1757 
1758     // add to connections list
1759     btstack_linked_list_add(&l2cap_le_channels, (btstack_linked_item_t *) channel);
1760 
1761     // check if hci connection is already usable
1762     hci_connection_t * conn = hci_connection_for_bd_addr_and_type(address, address_type);
1763 
1764     channel->state = L2CAP_STATE_WAIT_CONNECTION_COMPLETE;
1765 
1766     if (conn){
1767         log_info("l2cap_le_create_channel, hci connection already exists");
1768         l2cap_handle_le_connection_complete(channel, 0, conn->con_handle);
1769     } else {
1770 
1771         //
1772         // TODO: start timer
1773         // ..
1774 
1775         // start connection
1776         uint8_t res = gap_auto_connection_start(address_type, address);
1777         if (res){
1778             // discard channel object
1779             btstack_linked_list_remove(&l2cap_channels, (btstack_linked_item_t *) channel);
1780             btstack_memory_l2cap_channel_free(channel);
1781             return res;
1782         }
1783     }
1784     return 0;
1785 }
1786 
1787 /**
1788  * @brief Provide credtis for LE Data Channel
1789  * @param local_cid             L2CAP LE Data Channel Identifier
1790  * @param credits               Number additional credits for peer
1791  */
1792 uint8_t l2cap_le_provide_credits(uint16_t cid, uint16_t credits){
1793     // get connection
1794     // bail if missing
1795     // check state
1796     // check incoming credits + credits <= 0xffff
1797     // set credits_granted
1798     // l2cap_le_run()
1799     return 0;
1800 }
1801 
1802 /**
1803  * @brief Check if outgoing buffer is available and that there's space on the Bluetooth module
1804  * @param local_cid             L2CAP LE Data Channel Identifier
1805  */
1806 int l2cap_le_can_send_now(uint16_t cid){
1807     // check if data can be sent via le at all
1808     return 0;
1809 }
1810 
1811 /**
1812  * @brief Request emission of L2CAP_EVENT_CAN_SEND_NOW as soon as possible
1813  * @note L2CAP_EVENT_CAN_SEND_NOW might be emitted during call to this function
1814  *       so packet handler should be ready to handle it
1815  * @param local_cid             L2CAP LE Data Channel Identifier
1816  */
1817 uint8_t l2cap_le_request_can_send_now_event(uint16_t cid){
1818     // same as for non-le
1819     return 0;
1820 }
1821 
1822 /**
1823  * @brief Send data via LE Data Channel
1824  * @note Since data larger then the maximum PDU needs to be segmented into multiple PDUs, data needs to stay valid until ... event
1825  * @param local_cid             L2CAP LE Data Channel Identifier
1826  * @param data                  data to send
1827  * @param size                  data size
1828  */
1829 uint8_t l2cap_le_send_data(uint16_t cid, uint8_t * data, uint16_t size){
1830     // check if no outgoing data is pending
1831     // store info
1832     // l2cap_le_run()
1833     return 0;
1834 }
1835 
1836 /**
1837  * @brief Disconnect from LE Data Channel
1838  * @param local_cid             L2CAP LE Data Channel Identifier
1839  */
1840 uint8_t l2cap_le_disconnect(uint16_t cid)
1841 {
1842     // find channel
1843     // check state
1844     // set state SEND_DISCONNECT
1845     return 0;
1846 }
1847 
1848 #endif
1849