xref: /btstack/src/l2cap.c (revision 2784b77d474ef864ff76cf5ba5d03bc0e36dd7c8)
1 /*
2  * Copyright (C) 2009 by Matthias Ringwald
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  *
17  * THIS SOFTWARE IS PROVIDED BY MATTHIAS RINGWALD AND CONTRIBUTORS
18  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
19  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
20  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
21  * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
23  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
24  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
25  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
26  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
27  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28  * SUCH DAMAGE.
29  *
30  */
31 
32 /*
33  *  l2cap.c
34  *
35  *  Logical Link Control and Adaption Protocl (L2CAP)
36  *
37  *  Created by Matthias Ringwald on 5/16/09.
38  */
39 
40 #include "l2cap.h"
41 #include "hci.h"
42 #include "hci_dump.h"
43 
44 #include <stdarg.h>
45 #include <string.h>
46 
47 #include <stdio.h>
48 
49 // size of HCI ACL + L2CAP Header for regular data packets
50 #define COMPLETE_L2CAP_HEADER 8
51 
52 // minimum signaling MTU
53 #define L2CAP_MINIMAL_MTU 48
54 
55 // offsets for L2CAP SIGNALING COMMANDS
56 #define L2CAP_SIGNALING_COMMAND_CODE_OFFSET   0
57 #define L2CAP_SIGNALING_COMMAND_SIGID_OFFSET  1
58 #define L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET 2
59 #define L2CAP_SIGNALING_COMMAND_DATA_OFFSET   4
60 
61 static void null_event_handler(connection_t * connection, uint8_t *packet, uint16_t size);
62 static void null_data_handler(connection_t * connection, uint16_t local_cid, uint8_t *packet, uint16_t size);
63 
64 static uint8_t * sig_buffer = NULL;
65 static linked_list_t l2cap_channels = NULL;
66 static linked_list_t l2cap_services = NULL;
67 static uint8_t * acl_buffer = NULL;
68 static void (*event_packet_handler) (connection_t * connection, uint8_t *packet, uint16_t size) = null_event_handler;
69 static void (*data_packet_handler)  (connection_t * connection, uint16_t local_cid, uint8_t *packet, uint16_t size) = null_data_handler;
70 static connection_t * capture_connection = NULL;
71 
72 static uint8_t config_options[] = { 1, 2, 150, 0}; // mtu = 48
73 
74 void l2cap_init(){
75     sig_buffer = malloc( L2CAP_MINIMAL_MTU );
76     // acl_buffer = malloc( 255 + 8 );
77     acl_buffer = malloc( 400 + 8 );
78 
79     //
80     // register callbacks with HCI
81     //
82     hci_register_event_packet_handler(&l2cap_event_handler);
83     hci_register_acl_packet_handler(&l2cap_acl_handler);
84 }
85 
86 
87 /** Register L2CAP packet handlers */
88 static void null_event_handler(connection_t * connection, uint8_t *packet, uint16_t size){
89 }
90 static void null_data_handler(connection_t * connection, uint16_t  local_cid, uint8_t *packet, uint16_t size){
91 }
92 void l2cap_register_event_packet_handler(void (*handler)(connection_t * connection, uint8_t *packet, uint16_t size)){
93     event_packet_handler = handler;
94 }
95 void l2cap_register_data_packet_handler  (void (*handler)(connection_t * connection, uint16_t local_cid, uint8_t *packet, uint16_t size)){
96     data_packet_handler = handler;
97 }
98 
99 //  notify client/protocol handler
100 void l2cap_dispatch(l2cap_channel_t *channel, uint8_t type, uint8_t * data, uint16_t size){
101     if (channel->packet_handler) {
102         (* (channel->packet_handler))(type, channel->local_cid, data, size);
103     } else {
104         switch (type){
105             case HCI_EVENT_PACKET:
106                 (*event_packet_handler)(channel->connection, data, size);
107                 break;
108             case L2CAP_DATA_PACKET:
109                 (*data_packet_handler)(channel->connection, channel->local_cid, data, size);
110                 break;
111             default:
112                 // ??
113                 break;
114         }
115     }
116 }
117 
118 void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status) {
119     uint8_t event[17];
120     event[0] = L2CAP_EVENT_CHANNEL_OPENED;
121     event[1] = sizeof(event) - 2;
122     event[2] = status;
123     bt_flip_addr(&event[3], channel->address);
124     bt_store_16(event,  9, channel->handle);
125     bt_store_16(event, 11, channel->psm);
126     bt_store_16(event, 13, channel->local_cid);
127     bt_store_16(event, 15, channel->remote_cid);
128     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
129     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
130 }
131 
132 void l2cap_emit_channel_closed(l2cap_channel_t *channel) {
133     uint8_t event[4];
134     event[0] = L2CAP_EVENT_CHANNEL_CLOSED;
135     event[1] = sizeof(event) - 2;
136     bt_store_16(event, 2, channel->local_cid);
137     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
138     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
139 }
140 
141 void l2cap_emit_connection_request(l2cap_channel_t *channel) {
142     uint8_t event[16];
143     event[0] = L2CAP_EVENT_INCOMING_CONNECTION;
144     event[1] = sizeof(event) - 2;
145     bt_flip_addr(&event[2], channel->address);
146     bt_store_16(event,  8, channel->handle);
147     bt_store_16(event, 10, channel->psm);
148     bt_store_16(event, 12, channel->local_cid);
149     bt_store_16(event, 14, channel->remote_cid);
150     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
151     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
152 }
153 
154 l2cap_channel_t * l2cap_get_channel_for_local_cid(uint16_t local_cid){
155     linked_item_t *it;
156     l2cap_channel_t * channel;
157     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
158         channel = (l2cap_channel_t *) it;
159         if ( channel->local_cid == local_cid) {
160             return channel;
161         }
162     }
163     return NULL;
164 }
165 
166 int l2cap_send_signaling_packet(hci_con_handle_t handle, L2CAP_SIGNALING_COMMANDS cmd, uint8_t identifier, ...){
167     // printf("l2cap_send_signaling_packet type %u\n", cmd);
168     va_list argptr;
169     va_start(argptr, identifier);
170     uint16_t len = l2cap_create_signaling_internal(sig_buffer, handle, cmd, identifier, argptr);
171     va_end(argptr);
172     return hci_send_acl_packet(sig_buffer, len);
173 }
174 
175 void l2cap_send_internal(uint16_t local_cid, uint8_t *data, uint16_t len){
176     // find channel for local_cid, construct l2cap packet and send
177     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
178     if (channel) {
179         // 0 - Connection handle : PB=10 : BC=00
180         bt_store_16(acl_buffer, 0, channel->handle | (2 << 12) | (0 << 14));
181         // 2 - ACL length
182         bt_store_16(acl_buffer, 2,  len + 4);
183         // 4 - L2CAP packet length
184         bt_store_16(acl_buffer, 4,  len + 0);
185         // 6 - L2CAP channel DEST
186         bt_store_16(acl_buffer, 6, channel->remote_cid);
187         // 8 - data
188         memcpy(&acl_buffer[8], data, len);
189         // send
190         hci_send_acl_packet(acl_buffer, len+8);
191     }
192 }
193 
194 // open outgoing L2CAP channel
195 void l2cap_create_channel_internal(connection_t * connection, bd_addr_t address, uint16_t psm){
196 
197     // alloc structure
198     l2cap_channel_t * chan = malloc(sizeof(l2cap_channel_t));
199     // TODO: emit error event
200     if (!chan) return;
201 
202     // fill in
203     BD_ADDR_COPY(chan->address, address);
204     chan->psm = psm;
205     chan->handle = 0;
206     chan->connection = connection;
207     chan->packet_handler = NULL;
208     chan->remote_mtu = L2CAP_MINIMAL_MTU;
209 
210     // set initial state
211     chan->state = L2CAP_STATE_CLOSED;
212     chan->sig_id = L2CAP_SIG_ID_INVALID;
213 
214     // add to connections list
215     linked_list_add(&l2cap_channels, (linked_item_t *) chan);
216 
217     // send connection request
218     // BD_ADDR, Packet_Type, Page_Scan_Repetition_Mode, Reserved, Clock_Offset, Allow_Role_Switch
219     hci_send_cmd(&hci_create_connection, address, 0x18, 0, 0, 0, 0);
220 }
221 
222 void l2cap_disconnect_internal(uint16_t local_cid, uint8_t reason){
223     // find channel for local_cid
224     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
225     if (channel) {
226         channel->sig_id = l2cap_next_sig_id();
227         l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->sig_id, channel->remote_cid, channel->local_cid);
228         channel->state = L2CAP_STATE_WAIT_DISCONNECT;
229     }
230 }
231 
232 static void l2cap_handle_connection_failed_for_addr(bd_addr_t address, uint8_t status){
233     linked_item_t *it;
234     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
235         l2cap_channel_t * channel = (l2cap_channel_t *) it;
236         if ( ! BD_ADDR_CMP( channel->address, address) ){
237             if (channel->state == L2CAP_STATE_CLOSED) {
238                 // failure, forward error code
239                 l2cap_emit_channel_opened(channel, status);
240                 // discard channel
241                 linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
242                 free (channel);
243             }
244         }
245     }
246 }
247 
248 static void l2cap_handle_connection_success_for_addr(bd_addr_t address, hci_con_handle_t handle){
249     linked_item_t *it;
250     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
251         l2cap_channel_t * channel = (l2cap_channel_t *) it;
252         if ( ! BD_ADDR_CMP( channel->address, address) ){
253             if (channel->state == L2CAP_STATE_CLOSED) {
254                 // success, start l2cap handshake
255                 channel->handle = handle;
256                 channel->sig_id = l2cap_next_sig_id();
257                 channel->local_cid = l2cap_next_local_cid();
258                 channel->state = L2CAP_STATE_WAIT_CONNECT_RSP;
259                 l2cap_send_signaling_packet( channel->handle, CONNECTION_REQUEST, channel->sig_id, channel->psm, channel->local_cid);
260             }
261         }
262     }
263 }
264 
265 void l2cap_event_handler( uint8_t *packet, uint16_t size ){
266 
267     bd_addr_t address;
268     hci_con_handle_t handle;
269 
270     switch(packet[0]){
271 
272         // handle connection complete events
273         case HCI_EVENT_CONNECTION_COMPLETE:
274             bt_flip_addr(address, &packet[5]);
275             if (packet[2] == 0){
276                 handle = READ_BT_16(packet, 3);
277                 l2cap_handle_connection_success_for_addr(address, handle);
278             } else {
279                 l2cap_handle_connection_failed_for_addr(address, packet[2]);
280             }
281             break;
282 
283         // handle successful create connection cancel command
284         case HCI_EVENT_COMMAND_COMPLETE:
285             if ( COMMAND_COMPLETE_EVENT(packet, hci_create_connection_cancel) ) {
286                 if (packet[5] == 0){
287                     bt_flip_addr(address, &packet[6]);
288                     // CONNECTION TERMINATED BY LOCAL HOST (0X16)
289                     l2cap_handle_connection_failed_for_addr(address, 0x16);
290                 }
291             }
292             break;
293 
294         // handle disconnection complete events
295         case HCI_EVENT_DISCONNECTION_COMPLETE:
296             // send l2cap disconnect events for all channels on this handle
297             handle = READ_BT_16(packet, 3);
298             linked_item_t *it;
299             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
300                 l2cap_channel_t * channel = (l2cap_channel_t *) it;
301                 if ( channel->handle == handle ){
302                     l2cap_finialize_channel_close(channel);
303                 }
304             }
305             break;
306 
307         // HCI Connection Timeouts
308         case L2CAP_EVENT_TIMEOUT_CHECK:
309             if (!capture_connection){
310                 hci_con_handle_t handle = READ_BT_16(packet, 2);
311                 linked_item_t *it;
312                 l2cap_channel_t * channel;
313                 int used = 0;
314                 for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
315                     channel = (l2cap_channel_t *) it;
316                     if (channel->handle == handle) {
317                         used = 1;
318                     }
319                 }
320                 if (!used) {
321                     hci_send_cmd(&hci_disconnect, handle, 0x13); // remote closed connection
322                 }
323             }
324             break;
325 
326         default:
327             break;
328     }
329 
330     // pass on
331     (*event_packet_handler)(NULL, packet, size);
332 }
333 
334 static void l2cap_handle_disconnect_request(l2cap_channel_t *channel, uint16_t identifier){
335     l2cap_send_signaling_packet( channel->handle, DISCONNECTION_RESPONSE, identifier, channel->local_cid, channel->remote_cid);
336     l2cap_finialize_channel_close(channel);
337 }
338 
339 static void l2cap_handle_connection_request(hci_con_handle_t handle, uint8_t sig_id, uint16_t psm, uint16_t source_cid){
340 
341     // printf("l2cap_handle_connection_request for handle %u, psm %u cid %u\n", handle, psm, source_cid);
342     l2cap_service_t *service = l2cap_get_service(psm);
343     if (!service) {
344         // 0x0002 PSM not supported
345         // printf("l2cap_handle_connection_request no PSM for psm %u/n", psm);
346         l2cap_send_signaling_packet(handle, CONNECTION_RESPONSE, sig_id, 0, 0, 0x0002, 0);
347         return;
348     }
349 
350     hci_connection_t * hci_connection = connection_for_handle( handle );
351     if (!hci_connection) {
352         fprintf(stderr, "no hci_connection for handle %u\n", handle);
353         // TODO: emit error
354         return;
355     }
356     // alloc structure
357     // printf("l2cap_handle_connection_request register channel\n");
358     l2cap_channel_t * channel = malloc(sizeof(l2cap_channel_t));
359     // TODO: emit error event
360     if (!channel) return;
361 
362     // fill in
363     BD_ADDR_COPY(channel->address, hci_connection->address);
364     channel->psm = psm;
365     channel->handle = handle;
366     channel->connection = service->connection;
367     channel->packet_handler = service->packet_handler;
368     channel->local_cid  = l2cap_next_local_cid();
369     channel->remote_cid = source_cid;
370     channel->remote_mtu = L2CAP_MINIMAL_MTU;
371 
372     // set initial state
373     channel->state = L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT;
374 
375     // temp. store req sig id
376     channel->sig_id = sig_id;
377 
378     // add to connections list
379     linked_list_add(&l2cap_channels, (linked_item_t *) channel);
380 
381     // emit incoming connection request
382     l2cap_emit_connection_request(channel);
383 }
384 
385 void l2cap_accept_connection_internal(uint16_t local_cid){
386     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
387     if (!channel) {
388         fprintf(stderr, "l2cap_accept_connection_internal called but local_cid 0x%x not found", local_cid);
389         return;
390     }
391 
392     // accept connection
393     l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->sig_id, channel->local_cid, channel->remote_cid, 0, 0);
394 
395     // set real sig and state and start config
396     channel->sig_id = l2cap_next_sig_id();
397     channel->state  = L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ;
398     l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->sig_id, channel->remote_cid, 0, 4, &config_options);
399 
400     // printf("new state %u\n", channel->state);
401 }
402 
403 void l2cap_decline_connection_internal(uint16_t local_cid, uint8_t reason){
404     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid( local_cid);
405     if (!channel) {
406         fprintf(stderr, "l2cap_decline_connection_internal called but local_cid 0x%x not found", local_cid,reason);
407         return;
408     }
409     l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->sig_id, 0, 0, reason, 0);
410 
411     // discard channel
412     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
413     free (channel);
414 }
415 
416 void l2cap_signaling_handle_configure_request(l2cap_channel_t *channel, uint8_t *command){
417     // accept the other's configuration options
418     uint16_t len       = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
419     uint8_t identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
420     l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, identifier, channel->remote_cid, 0, 0, len-4, &command[8]);
421 }
422 
423 void l2cap_signaling_handler_channel(l2cap_channel_t *channel, uint8_t *command){
424 
425     uint8_t code       = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
426     uint8_t identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
427     uint16_t result = 0;
428 
429     // printf("signaling handler code %u\n", code);
430 
431     switch (channel->state) {
432 
433         case L2CAP_STATE_WAIT_CONNECT_RSP:
434             switch (code){
435                 case CONNECTION_RESPONSE:
436                     result = READ_BT_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
437                     switch (result) {
438                         case 0:
439                             // successful connection
440                             channel->remote_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
441                             channel->sig_id = l2cap_next_sig_id();
442                             l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->sig_id, channel->remote_cid, 0, 4, &config_options);
443                             channel->state = L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ;
444                             break;
445                         case 1:
446                             // connection pending. get some coffee
447                             break;
448                         default:
449                             // map l2cap connection response result to BTstack status enumeration
450                             l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result);
451                             break;
452                     }
453                     break;
454 
455                 case DISCONNECTION_REQUEST:
456                     l2cap_handle_disconnect_request(channel, identifier);
457                     break;
458 
459                 default:
460                     //@TODO: implement other signaling packets
461                     break;
462             }
463             break;
464 
465         case L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ:
466             switch (code) {
467                 case CONFIGURE_RESPONSE:
468                     channel->state = L2CAP_STATE_WAIT_CONFIG_REQ;
469                     break;
470                 case CONFIGURE_REQUEST:
471                     l2cap_signaling_handle_configure_request(channel, command);
472                     channel->state = L2CAP_STATE_WAIT_CONFIG_REQ_RSP;
473                     break;
474                 case DISCONNECTION_REQUEST:
475                     l2cap_handle_disconnect_request(channel, identifier);
476                     break;
477                 default:
478                     //@TODO: implement other signaling packets
479                     break;
480             }
481             break;
482 
483         case L2CAP_STATE_WAIT_CONFIG_REQ:
484             switch (code) {
485                 case CONFIGURE_REQUEST:
486                     l2cap_signaling_handle_configure_request(channel, command);
487                     channel->state = L2CAP_STATE_OPEN;
488                     l2cap_emit_channel_opened(channel, 0);  // success
489                     break;
490                 case DISCONNECTION_REQUEST:
491                     l2cap_handle_disconnect_request(channel, identifier);
492                     break;
493                 default:
494                     //@TODO: implement other signaling packets
495                     break;
496             }
497             break;
498 
499         case L2CAP_STATE_WAIT_CONFIG_REQ_RSP:
500             switch (code) {
501                 case CONFIGURE_RESPONSE:
502                     channel->state = L2CAP_STATE_OPEN;
503                     l2cap_emit_channel_opened(channel, 0);  // success
504                     break;
505                 case DISCONNECTION_REQUEST:
506                     l2cap_handle_disconnect_request(channel, identifier);
507                     break;
508                 default:
509                     //@TODO: implement other signaling packets
510                     break;
511             }
512             break;
513 
514         case L2CAP_STATE_WAIT_DISCONNECT:
515             switch (code) {
516                 case DISCONNECTION_RESPONSE:
517                     l2cap_finialize_channel_close(channel);
518                     break;
519                 case DISCONNECTION_REQUEST:
520                     l2cap_handle_disconnect_request(channel, identifier);
521                     break;
522                 default:
523                     //@TODO: implement other signaling packets
524                     break;
525             }
526             break;
527 
528         case L2CAP_STATE_CLOSED:
529             // @TODO handle incoming requests
530             break;
531 
532         case L2CAP_STATE_OPEN:
533             switch (code) {
534                 case DISCONNECTION_REQUEST:
535                     l2cap_handle_disconnect_request(channel, identifier);
536                     break;
537                 default:
538                     //@TODO: implement other signaling packets, e.g. re-configure
539                     break;
540             }
541             break;
542     }
543     // printf("new state %u\n", channel->state);
544 }
545 
546 
547 void l2cap_signaling_handler_dispatch( hci_con_handle_t handle, uint8_t * command){
548 
549     // get code, signalind identifier and command len
550     uint8_t code   = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
551     uint8_t sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
552     uint16_t len   = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
553 
554     // not for a particular channel, and not CONNECTION_REQUEST, ECHO_[REQUEST|RESPONSE], INFORMATION_REQUEST
555     if (code < 1 || code == ECHO_RESPONSE || code > INFORMATION_REQUEST){
556         return;
557     }
558 
559     // general commands without an assigned channel
560     switch(code) {
561 
562         case CONNECTION_REQUEST: {
563             uint16_t psm =        READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
564             uint16_t source_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+2);
565             l2cap_handle_connection_request(handle, sig_id, psm, source_cid);
566             break;
567         }
568 
569         case ECHO_REQUEST: {
570             // send back packet
571             l2cap_send_signaling_packet(handle, ECHO_RESPONSE, sig_id, len, &command[L2CAP_SIGNALING_COMMAND_DATA_OFFSET]);
572             break;
573         }
574 
575         case INFORMATION_REQUEST: {
576             // we neither support connectionless L2CAP data nor support any flow control modes yet
577             uint16_t infoType = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
578             if (infoType == 2) {
579                 uint32_t features = 0;
580                 // extended features request supported, however no features present
581                 l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, 4, &features);
582             } else {
583                 // all other types are not supported
584                 l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 1, 0, NULL);
585             }
586             break;;
587         }
588 
589         default:
590             break;
591     }
592 
593 
594     // Get potential destination CID
595     uint16_t dest_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
596 
597     // Find channel for this sig_id and connection handle
598     linked_item_t *it;
599     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
600         l2cap_channel_t * channel = (l2cap_channel_t *) it;
601         if (channel->handle == handle) {
602             if (code & 1) {
603                 // match odd commands by previous signaling identifier
604                 if (channel->sig_id == sig_id) {
605                     l2cap_signaling_handler_channel(channel, command);
606                 }
607             } else {
608                 // match even commands by local channel id
609                 if (channel->local_cid == dest_cid) {
610                     l2cap_signaling_handler_channel(channel, command);
611                 }
612             }
613         }
614     }
615 }
616 
617 void l2cap_acl_handler( uint8_t *packet, uint16_t size ){
618 
619     // Capturing?
620     if (capture_connection) {
621         (*data_packet_handler)(capture_connection, 0, packet, size);
622         return;
623     }
624 
625     // Get Channel ID
626     uint16_t channel_id = READ_L2CAP_CHANNEL_ID(packet);
627 
628     // Signaling Packet?
629     if (channel_id == 1) {
630 
631         // Get Connection
632         hci_con_handle_t handle = READ_ACL_CONNECTION_HANDLE(packet);
633 
634         uint16_t command_offset = 8;
635         while (command_offset < size) {
636 
637             // handle signaling commands
638             l2cap_signaling_handler_dispatch(handle, &packet[command_offset]);
639 
640             // increment command_offset
641             command_offset += L2CAP_SIGNALING_COMMAND_DATA_OFFSET + READ_BT_16(packet, command_offset + L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
642         }
643         return;
644     }
645 
646     // Find channel for this channel_id and connection handle
647     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(channel_id);
648     if (channel) {
649         l2cap_dispatch(channel, L2CAP_DATA_PACKET, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
650     }
651 }
652 
653 
654 // finalize closed channel
655 void l2cap_finialize_channel_close(l2cap_channel_t *channel){
656     channel->state = L2CAP_STATE_CLOSED;
657     l2cap_emit_channel_closed(channel);
658 
659     // discard channel
660     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
661     free (channel);
662 }
663 
664 l2cap_service_t * l2cap_get_service(uint16_t psm){
665     linked_item_t *it;
666 
667     // close open channels
668     for (it = (linked_item_t *) l2cap_services; it ; it = it->next){
669         l2cap_service_t * service = ((l2cap_service_t *) it);
670         if ( service->psm == psm){
671             return service;
672         };
673     }
674     return NULL;
675 }
676 
677 void l2cap_register_service_internal(connection_t *connection, btstack_packet_handler_t packet_handler, uint16_t psm, uint16_t mtu){
678     // check for alread registered psm // TODO: emit error event
679     l2cap_service_t *service = l2cap_get_service(psm);
680     if (service) return;
681 
682     // alloc structure     // TODO: emit error event
683     service = malloc(sizeof(l2cap_service_t));
684     if (!service) return;
685 
686     // fill in
687     service->psm = psm;
688     service->mtu = mtu;
689     service->connection = connection;
690     service->packet_handler = packet_handler;
691 
692     // add to services list
693     linked_list_add(&l2cap_services, (linked_item_t *) service);
694 }
695 
696 void l2cap_unregister_service_internal(connection_t *connection, uint16_t psm){
697     l2cap_service_t *service = l2cap_get_service(psm);
698     if (!service) return;
699     linked_list_remove(&l2cap_services, (linked_item_t *) service);
700     free(service);
701 }
702 
703 //
704 void l2cap_close_connection(connection_t *connection){
705     linked_item_t *it;
706 
707     // close open channels
708     l2cap_channel_t * channel;
709     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
710         channel = (l2cap_channel_t *) it;
711         if (channel->connection == connection) {
712             channel->sig_id = l2cap_next_sig_id();
713             l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->sig_id, channel->remote_cid, channel->local_cid);
714             channel->state = L2CAP_STATE_WAIT_DISCONNECT;
715         }
716     }
717 
718     // unregister services
719     it = (linked_item_t *) &l2cap_services;
720     while (it->next){
721         l2cap_service_t * service = (l2cap_service_t *) it->next;
722         if (service->connection == connection){
723             it->next = it->next->next;
724             free(service);
725         } else {
726             it = it->next;
727         }
728     }
729 }
730 
731 
732 void l2cap_set_capture_connection(connection_t * connection){
733     capture_connection = connection;
734 }
735 
736