xref: /btstack/src/l2cap.c (revision 00d93d799ac9d5a61fb938dc3b45b58c81fb38a2)
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 // offsets for L2CAP SIGNALING COMMANDS
53 #define L2CAP_SIGNALING_COMMAND_CODE_OFFSET   0
54 #define L2CAP_SIGNALING_COMMAND_SIGID_OFFSET  1
55 #define L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET 2
56 #define L2CAP_SIGNALING_COMMAND_DATA_OFFSET   4
57 
58 static void null_event_handler(connection_t * connection, uint8_t *packet, uint16_t size);
59 static void null_data_handler(connection_t * connection, uint16_t local_cid, uint8_t *packet, uint16_t size);
60 
61 static uint8_t * sig_buffer = NULL;
62 static linked_list_t l2cap_channels = NULL;
63 static linked_list_t l2cap_services = NULL;
64 static uint8_t * acl_buffer = NULL;
65 static void (*event_packet_handler) (connection_t * connection, uint8_t *packet, uint16_t size) = null_event_handler;
66 static void (*data_packet_handler)  (connection_t * connection, uint16_t local_cid, uint8_t *packet, uint16_t size) = null_data_handler;
67 static connection_t * capture_connection = NULL;
68 
69 static uint8_t config_options[] = { 1, 2, 150, 0}; // mtu = 48
70 
71 void l2cap_init(){
72     sig_buffer = malloc( 48 );
73     acl_buffer = malloc( 255 + 8 );
74 
75     //
76     // register callbacks with HCI
77     //
78     hci_register_event_packet_handler(&l2cap_event_handler);
79     hci_register_acl_packet_handler(&l2cap_acl_handler);
80 }
81 
82 
83 /** Register L2CAP packet handlers */
84 static void null_event_handler(connection_t * connection, uint8_t *packet, uint16_t size){
85 }
86 static void null_data_handler(connection_t * connection, uint16_t  local_cid, uint8_t *packet, uint16_t size){
87 }
88 void l2cap_register_event_packet_handler(void (*handler)(connection_t * connection, uint8_t *packet, uint16_t size)){
89     event_packet_handler = handler;
90 }
91 void l2cap_register_data_packet_handler  (void (*handler)(connection_t * connection, uint16_t local_cid, uint8_t *packet, uint16_t size)){
92     data_packet_handler = handler;
93 }
94 
95 int l2cap_send_signaling_packet(hci_con_handle_t handle, L2CAP_SIGNALING_COMMANDS cmd, uint8_t identifier, ...){
96     // printf("l2cap_send_signaling_packet type %u\n", cmd);
97     va_list argptr;
98     va_start(argptr, identifier);
99     uint16_t len = l2cap_create_signaling_internal(sig_buffer, handle, cmd, identifier, argptr);
100     va_end(argptr);
101     return hci_send_acl_packet(sig_buffer, len);
102 }
103 
104 l2cap_channel_t * l2cap_get_channel_for_local_cid(uint16_t local_cid){
105     linked_item_t *it;
106     l2cap_channel_t * channel;
107     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
108         channel = (l2cap_channel_t *) it;
109         if ( channel->local_cid == local_cid) {
110             return channel;
111         }
112     }
113     return NULL;
114 }
115 
116 // open outgoing L2CAP channel
117 void l2cap_create_channel_internal(connection_t * connection, bd_addr_t address, uint16_t psm){
118 
119     // alloc structure
120     l2cap_channel_t * chan = malloc(sizeof(l2cap_channel_t));
121     // TODO: emit error event
122     if (!chan) return;
123 
124     // fill in
125     BD_ADDR_COPY(chan->address, address);
126     chan->psm = psm;
127     chan->handle = 0;
128     chan->connection = connection;
129 
130     // set initial state
131     chan->state = L2CAP_STATE_CLOSED;
132     chan->sig_id = L2CAP_SIG_ID_INVALID;
133 
134     // add to connections list
135     linked_list_add(&l2cap_channels, (linked_item_t *) chan);
136 
137     // send connection request
138     // BD_ADDR, Packet_Type, Page_Scan_Repetition_Mode, Reserved, Clock_Offset, Allow_Role_Switch
139     hci_send_cmd(&hci_create_connection, address, 0x18, 0, 0, 0, 0);
140 }
141 
142 void l2cap_disconnect_internal(uint16_t local_cid, uint8_t reason){
143     // find channel for local_cid
144     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
145     if (channel) {
146         channel->sig_id = l2cap_next_sig_id();
147         l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->sig_id, channel->remote_cid, channel->local_cid);
148         channel->state = L2CAP_STATE_WAIT_DISCONNECT;
149     }
150 }
151 
152 static void l2cap_handle_connection_failed_for_addr(bd_addr_t address, uint8_t status){
153     linked_item_t *it;
154     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
155         l2cap_channel_t * channel = (l2cap_channel_t *) it;
156         if ( ! BD_ADDR_CMP( channel->address, address) ){
157             if (channel->state == L2CAP_STATE_CLOSED) {
158                 // failure, forward error code
159                 l2cap_emit_channel_opened(channel, status);
160                 // discard channel
161                 linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
162                 free (channel);
163             }
164         }
165     }
166 }
167 
168 static void l2cap_handle_connection_success_for_addr(bd_addr_t address, hci_con_handle_t handle){
169     linked_item_t *it;
170     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
171         l2cap_channel_t * channel = (l2cap_channel_t *) it;
172         if ( ! BD_ADDR_CMP( channel->address, address) ){
173             if (channel->state == L2CAP_STATE_CLOSED) {
174                 // success, start l2cap handshake
175                 channel->handle = handle;
176                 channel->sig_id = l2cap_next_sig_id();
177                 channel->local_cid = l2cap_next_local_cid();
178                 channel->state = L2CAP_STATE_WAIT_CONNECT_RSP;
179                 l2cap_send_signaling_packet( channel->handle, CONNECTION_REQUEST, channel->sig_id, channel->psm, channel->local_cid);
180             }
181         }
182     }
183 }
184 
185 void l2cap_event_handler( uint8_t *packet, uint16_t size ){
186 
187     bd_addr_t address;
188     hci_con_handle_t handle;
189 
190     switch(packet[0]){
191 
192         // handle connection complete events
193         case HCI_EVENT_CONNECTION_COMPLETE:
194             bt_flip_addr(address, &packet[5]);
195             if (packet[2] == 0){
196                 handle = READ_BT_16(packet, 3);
197                 l2cap_handle_connection_success_for_addr(address, handle);
198             } else {
199                 l2cap_handle_connection_failed_for_addr(address, packet[2]);
200             }
201             break;
202 
203         // handle successful create connection cancel command
204         case HCI_EVENT_COMMAND_COMPLETE:
205             if ( COMMAND_COMPLETE_EVENT(packet, hci_create_connection_cancel) ) {
206                 if (packet[5] == 0){
207                     bt_flip_addr(address, &packet[6]);
208                     // CONNECTION TERMINATED BY LOCAL HOST (0X16)
209                     l2cap_handle_connection_failed_for_addr(address, 0x16);
210                 }
211             }
212             break;
213 
214         // handle disconnection complete events
215         case HCI_EVENT_DISCONNECTION_COMPLETE:
216             // send l2cap disconnect events for all channels on this handle
217             handle = READ_BT_16(packet, 3);
218             linked_item_t *it;
219             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
220                 l2cap_channel_t * channel = (l2cap_channel_t *) it;
221                 if ( channel->handle == handle ){
222                     l2cap_finialize_channel_close(channel);
223                 }
224             }
225             break;
226 
227         // HCI Connection Timeouts
228         case L2CAP_EVENT_TIMEOUT_CHECK:
229             if (!capture_connection){
230                 hci_con_handle_t handle = READ_BT_16(packet, 2);
231                 linked_item_t *it;
232                 l2cap_channel_t * channel;
233                 int used = 0;
234                 for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
235                     channel = (l2cap_channel_t *) it;
236                     if (channel->handle == handle) {
237                         used = 1;
238                     }
239                 }
240                 if (!used) {
241                     hci_send_cmd(&hci_disconnect, handle, 0x13); // remote closed connection
242                 }
243             }
244             break;
245 
246         default:
247             break;
248     }
249 
250     // pass on
251     (*event_packet_handler)(NULL, packet, size);
252 }
253 
254 static void l2cap_handle_disconnect_request(l2cap_channel_t *channel, uint16_t identifier){
255     l2cap_send_signaling_packet( channel->handle, DISCONNECTION_RESPONSE, identifier, channel->remote_cid, channel->local_cid);
256     l2cap_finialize_channel_close(channel);
257 }
258 
259 static void l2cap_handle_connection_request(hci_con_handle_t handle, uint8_t sig_id, uint16_t psm, uint16_t source_cid){
260 
261     // printf("l2cap_handle_connection_request for handle %u, psm %u cid %u\n", handle, psm, source_cid);
262     l2cap_service_t *service = l2cap_get_service(psm);
263     if (!service) {
264         // 0x0002 PSM not supported
265         // printf("l2cap_handle_connection_request no PSM for psm %u/n", psm);
266         l2cap_send_signaling_packet(handle, CONNECTION_RESPONSE, sig_id, 0, 0, 0x0002, 0);
267         return;
268     }
269 
270     hci_connection_t * hci_connection = connection_for_handle( handle );
271     if (!hci_connection) {
272         fprintf(stderr, "no hci_connection for handle %u\n", handle);
273         // TODO: emit error
274         return;
275     }
276     // alloc structure
277     // printf("l2cap_handle_connection_request register channel\n");
278     l2cap_channel_t * channel = malloc(sizeof(l2cap_channel_t));
279     // TODO: emit error event
280     if (!channel) return;
281 
282     // fill in
283     BD_ADDR_COPY(channel->address, hci_connection->address);
284     channel->psm = psm;
285     channel->handle = handle;
286     channel->connection = service->connection;
287     channel->local_cid  = l2cap_next_local_cid();
288     channel->remote_cid = source_cid;
289 
290     // set initial state
291     channel->state = L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT;
292 
293     // temp. store req sig id
294     channel->sig_id = sig_id;
295 
296     // add to connections list
297     linked_list_add(&l2cap_channels, (linked_item_t *) channel);
298 
299     // emit incoming connection request
300     l2cap_emit_connection_request(channel);
301 }
302 
303 void l2cap_accept_connection_internal(uint16_t local_cid){
304     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
305     if (!channel) {
306         fprintf(stderr, "l2cap_accept_connection_internal called but local_cid 0x%x not found", local_cid);
307         return;
308     }
309 
310     // accept connection
311     l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->sig_id, channel->local_cid, channel->remote_cid, 0, 0);
312 
313     // set real sig and state and start config
314     channel->sig_id = l2cap_next_sig_id();
315     channel->state  = L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ;
316     l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->sig_id, channel->remote_cid, 0, 4, &config_options);
317 
318     // printf("new state %u\n", channel->state);
319 }
320 
321 void l2cap_decline_connection_internal(uint16_t local_cid, uint8_t reason){
322     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid( local_cid);
323     if (!channel) {
324         fprintf(stderr, "l2cap_decline_connection_internal called but local_cid 0x%x not found", local_cid,reason);
325         return;
326     }
327     l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->sig_id, 0, 0, reason, 0);
328 
329     // discard channel
330     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
331     free (channel);
332 }
333 
334 void l2cap_signaling_handler_channel(l2cap_channel_t *channel, uint8_t *command){
335 
336     uint8_t code       = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
337     uint8_t identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
338     uint16_t len       = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
339     uint16_t result = 0;
340 
341     // printf("signaling handler code %u\n", code);
342 
343     switch (channel->state) {
344 
345         case L2CAP_STATE_WAIT_CONNECT_RSP:
346             switch (code){
347                 case CONNECTION_RESPONSE:
348                     result = READ_BT_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
349                     switch (result) {
350                         case 0:
351                             // successful connection
352                             channel->remote_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
353                             channel->sig_id = l2cap_next_sig_id();
354                             l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->sig_id, channel->remote_cid, 0, 4, &config_options);
355                             channel->state = L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ;
356                             break;
357                         case 1:
358                             // connection pending. get some coffee
359                             break;
360                         default:
361                             // map l2cap connection response result to BTstack status enumeration
362                             l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result);
363                             break;
364                     }
365                     break;
366 
367                 case DISCONNECTION_REQUEST:
368                     l2cap_handle_disconnect_request(channel, identifier);
369                     break;
370 
371                 default:
372                     //@TODO: implement other signaling packets
373                     break;
374             }
375             break;
376 
377         case L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ:
378             switch (code) {
379                 case CONFIGURE_RESPONSE:
380                     channel->state = L2CAP_STATE_WAIT_CONFIG_REQ;
381                     break;
382                 case CONFIGURE_REQUEST:
383                     // accept the other's configuration options
384                     l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, identifier, channel->remote_cid, 0, 0, len-4, &command[8]);
385                     channel->state = L2CAP_STATE_WAIT_CONFIG_REQ_RSP;
386                     break;
387                 case DISCONNECTION_REQUEST:
388                     l2cap_handle_disconnect_request(channel, identifier);
389                     break;
390                 default:
391                     //@TODO: implement other signaling packets
392                     break;
393             }
394             break;
395 
396         case L2CAP_STATE_WAIT_CONFIG_REQ:
397             switch (code) {
398                 case CONFIGURE_REQUEST:
399                     // accept the other's configuration options
400                     l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, identifier, channel->remote_cid, 0, 0, len-4, &command[8]);
401                     channel->state = L2CAP_STATE_OPEN;
402                     l2cap_emit_channel_opened(channel, 0);  // success
403                     break;
404                 case DISCONNECTION_REQUEST:
405                     l2cap_handle_disconnect_request(channel, identifier);
406                     break;
407                 default:
408                     //@TODO: implement other signaling packets
409                     break;
410             }
411             break;
412 
413         case L2CAP_STATE_WAIT_CONFIG_REQ_RSP:
414             switch (code) {
415                 case CONFIGURE_RESPONSE:
416                     channel->state = L2CAP_STATE_OPEN;
417                     l2cap_emit_channel_opened(channel, 0);  // success
418                     break;
419                 case DISCONNECTION_REQUEST:
420                     l2cap_handle_disconnect_request(channel, identifier);
421                     break;
422                 default:
423                     //@TODO: implement other signaling packets
424                     break;
425             }
426             break;
427 
428         case L2CAP_STATE_WAIT_DISCONNECT:
429             switch (code) {
430                 case DISCONNECTION_RESPONSE:
431                     l2cap_finialize_channel_close(channel);
432                     break;
433                 case DISCONNECTION_REQUEST:
434                     l2cap_handle_disconnect_request(channel, identifier);
435                     break;
436                 default:
437                     //@TODO: implement other signaling packets
438                     break;
439             }
440             break;
441 
442         case L2CAP_STATE_CLOSED:
443             // @TODO handle incoming requests
444             break;
445 
446         case L2CAP_STATE_OPEN:
447             switch (code) {
448                 case DISCONNECTION_REQUEST:
449                     l2cap_handle_disconnect_request(channel, identifier);
450                     break;
451                 default:
452                     //@TODO: implement other signaling packets, e.g. re-configure
453                     break;
454             }
455             break;
456     }
457     // printf("new state %u\n", channel->state);
458 }
459 
460 
461 void l2cap_signaling_handler_dispatch( hci_con_handle_t handle, uint8_t * command){
462 
463     // get code, signalind identifier and command len
464     uint8_t code   = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
465     uint8_t sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
466     uint16_t len   = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
467 
468     // not for a particular channel, and not CONNECTION_REQUEST, ECHO_[REQUEST|RESPONSE], INFORMATION_REQUEST
469     if (code < 1 || code == ECHO_RESPONSE || code > INFORMATION_REQUEST){
470         return;
471     }
472 
473     // general commands without an assigned channel
474     switch(code) {
475 
476         case CONNECTION_REQUEST: {
477             uint16_t psm =        READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
478             uint16_t source_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+2);
479             l2cap_handle_connection_request(handle, sig_id, psm, source_cid);
480             break;
481         }
482 
483         case ECHO_REQUEST: {
484             // send back packet
485             l2cap_send_signaling_packet(handle, ECHO_RESPONSE, sig_id, len, &command[L2CAP_SIGNALING_COMMAND_DATA_OFFSET]);
486             break;
487         }
488 
489         case INFORMATION_REQUEST: {
490             // we neither support connectionless L2CAP data nor support any flow control modes yet
491             uint16_t infoType = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
492             if (infoType == 2) {
493                 uint32_t features = 0;
494                 // extended features request supported, however no features present
495                 l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, 4, &features);
496             } else {
497                 // all other types are not supported
498                 l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 1, 0, NULL);
499             }
500             break;;
501         }
502 
503         default:
504             break;
505     }
506 
507 
508     // Get potential destination CID
509     uint16_t dest_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
510 
511     // Find channel for this sig_id and connection handle
512     linked_item_t *it;
513     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
514         l2cap_channel_t * channel = (l2cap_channel_t *) it;
515         if (channel->handle == handle) {
516             if (code & 1) {
517                 // match odd commands by previous signaling identifier
518                 if (channel->sig_id == sig_id) {
519                     l2cap_signaling_handler_channel(channel, command);
520                 }
521             } else {
522                 // match even commands by local channel id
523                 if (channel->local_cid == dest_cid) {
524                     l2cap_signaling_handler_channel(channel, command);
525                 }
526             }
527         }
528     }
529 }
530 
531 void l2cap_acl_handler( uint8_t *packet, uint16_t size ){
532 
533     // Capturing?
534     if (capture_connection) {
535         (*data_packet_handler)(capture_connection, 0, packet, size);
536         return;
537     }
538 
539     // Get Channel ID
540     uint16_t channel_id = READ_L2CAP_CHANNEL_ID(packet);
541 
542     // Signaling Packet?
543     if (channel_id == 1) {
544 
545         // Get Connection
546         hci_con_handle_t handle = READ_ACL_CONNECTION_HANDLE(packet);
547 
548         uint16_t command_offset = 8;
549         while (command_offset < size) {
550 
551             // handle signaling commands
552             l2cap_signaling_handler_dispatch(handle, &packet[command_offset]);
553 
554             // increment command_offset
555             command_offset += L2CAP_SIGNALING_COMMAND_DATA_OFFSET + READ_BT_16(packet, command_offset + L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
556         }
557         return;
558     }
559 
560     // Find channel for this channel_id and connection handle
561     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(channel_id);
562     if (channel) {
563         (*data_packet_handler)(channel->connection, channel_id, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
564     }
565 }
566 
567 
568 // finalize closed channel
569 void l2cap_finialize_channel_close(l2cap_channel_t *channel){
570     channel->state = L2CAP_STATE_CLOSED;
571     l2cap_emit_channel_closed(channel);
572 
573     // discard channel
574     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
575     free (channel);
576 }
577 
578 l2cap_service_t * l2cap_get_service(uint16_t psm){
579     linked_item_t *it;
580 
581     // close open channels
582     for (it = (linked_item_t *) l2cap_services; it ; it = it->next){
583         l2cap_service_t * service = ((l2cap_service_t *) it);
584         if ( service->psm == psm){
585             return service;
586         };
587     }
588     return NULL;
589 }
590 
591 void l2cap_register_service_internal(connection_t *connection, uint16_t psm, uint16_t mtu){
592     // check for alread registered psm // TODO: emit error event
593     l2cap_service_t *service = l2cap_get_service(psm);
594     if (service) return;
595 
596     // alloc structure     // TODO: emit error event
597     service = malloc(sizeof(l2cap_service_t));
598     if (!service) return;
599 
600     // fill in
601     service->psm = psm;
602     service->mtu = mtu;
603     service->connection = connection;
604 
605     // add to services list
606     linked_list_add(&l2cap_services, (linked_item_t *) service);
607 }
608 
609 void l2cap_unregister_service_internal(connection_t *connection, uint16_t psm){
610     l2cap_service_t *service = l2cap_get_service(psm);
611     if (!service) return;
612     linked_list_remove(&l2cap_services, (linked_item_t *) service);
613     free(service);
614 }
615 
616 //
617 void l2cap_close_connection(connection_t *connection){
618     linked_item_t *it;
619 
620     // close open channels
621     l2cap_channel_t * channel;
622     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
623         channel = (l2cap_channel_t *) it;
624         if (channel->connection == connection) {
625             channel->sig_id = l2cap_next_sig_id();
626             l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->sig_id, channel->remote_cid, channel->local_cid);
627             channel->state = L2CAP_STATE_WAIT_DISCONNECT;
628         }
629     }
630 
631     // unregister services
632     l2cap_service_t *service;
633     for (it = (linked_item_t *) l2cap_services; it ; ){
634         service = (l2cap_service_t *) it->next;
635         if (service->connection == connection){
636             it->next = service->item.next;
637             free(service);
638         } else {
639             it = it->next;
640         }
641     }
642 }
643 
644 //  notify client
645 void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status) {
646     uint8_t event[17];
647     event[0] = L2CAP_EVENT_CHANNEL_OPENED;
648     event[1] = sizeof(event) - 2;
649     event[2] = status;
650     bt_flip_addr(&event[3], channel->address);
651     bt_store_16(event,  9, channel->handle);
652     bt_store_16(event, 11, channel->psm);
653     bt_store_16(event, 13, channel->local_cid);
654     bt_store_16(event, 15, channel->remote_cid);
655     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
656     (*event_packet_handler)(channel->connection, event, sizeof(event));
657 }
658 
659 void l2cap_emit_channel_closed(l2cap_channel_t *channel) {
660     uint8_t event[4];
661     event[0] = L2CAP_EVENT_CHANNEL_CLOSED;
662     event[1] = sizeof(event) - 2;
663     bt_store_16(event, 2, channel->local_cid);
664     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
665     (*event_packet_handler)(channel->connection, event, sizeof(event));
666 }
667 
668 void l2cap_emit_connection_request(l2cap_channel_t *channel) {
669     uint8_t event[16];
670     event[0] = L2CAP_EVENT_INCOMING_CONNECTION;
671     event[1] = sizeof(event) - 2;
672     bt_flip_addr(&event[2], channel->address);
673     bt_store_16(event,  8, channel->handle);
674     bt_store_16(event, 10, channel->psm);
675     bt_store_16(event, 12, channel->local_cid);
676     bt_store_16(event, 14, channel->remote_cid);
677     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
678     (*event_packet_handler)(channel->connection, event, sizeof(event));
679 }
680 
681 void l2cap_send_internal(uint16_t local_cid, uint8_t *data, uint16_t len){
682     // find channel for local_cid, construct l2cap packet and send
683     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
684     if (channel) {
685          // 0 - Connection handle : PB=10 : BC=00
686          bt_store_16(acl_buffer, 0, channel->handle | (2 << 12) | (0 << 14));
687          // 2 - ACL length
688          bt_store_16(acl_buffer, 2,  len + 4);
689          // 4 - L2CAP packet length
690          bt_store_16(acl_buffer, 4,  len + 0);
691          // 6 - L2CAP channel DEST
692          bt_store_16(acl_buffer, 6, channel->remote_cid);
693          // 8 - data
694          memcpy(&acl_buffer[8], data, len);
695          // send
696          hci_send_acl_packet(acl_buffer, len+8);
697      }
698 }
699 
700 void l2cap_set_capture_connection(connection_t * connection){
701     capture_connection = connection;
702 }
703 
704