xref: /btstack/src/l2cap.c (revision 8ea03fa51303fabecec620e09c83bf6a8749c598)
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 #include "debug.h"
44 
45 #include <stdarg.h>
46 #include <string.h>
47 
48 #include <stdio.h>
49 
50 // size of HCI ACL + L2CAP Header for regular data packets
51 #define COMPLETE_L2CAP_HEADER 8
52 
53 // minimum signaling MTU
54 #define L2CAP_MINIMAL_MTU 48
55 #define L2CAP_DEFAULT_MTU 672
56 
57 // offsets for L2CAP SIGNALING COMMANDS
58 #define L2CAP_SIGNALING_COMMAND_CODE_OFFSET   0
59 #define L2CAP_SIGNALING_COMMAND_SIGID_OFFSET  1
60 #define L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET 2
61 #define L2CAP_SIGNALING_COMMAND_DATA_OFFSET   4
62 
63 static void null_packet_handler(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size);
64 static void l2cap_packet_handler(uint8_t packet_type, uint8_t *packet, uint16_t size);
65 
66 static uint8_t * sig_buffer = NULL;
67 static linked_list_t l2cap_channels = NULL;
68 static linked_list_t l2cap_services = NULL;
69 static uint8_t * acl_buffer = NULL;
70 static void (*packet_handler) (void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size) = null_packet_handler;
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( HCI_ACL_3DH5_SIZE);
77 
78     //
79     // register callback with HCI
80     //
81     hci_register_packet_handler(&l2cap_packet_handler);
82 }
83 
84 
85 /** Register L2CAP packet handlers */
86 static void null_packet_handler(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
87 }
88 void l2cap_register_packet_handler(void (*handler)(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size)){
89     packet_handler = handler;
90 }
91 
92 //  notify client/protocol handler
93 void l2cap_dispatch(l2cap_channel_t *channel, uint8_t type, uint8_t * data, uint16_t size){
94     if (channel->packet_handler) {
95         (* (channel->packet_handler))(type, channel->local_cid, data, size);
96     } else {
97         (*packet_handler)(channel->connection, type, channel->local_cid, data, size);
98     }
99 }
100 
101 void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status) {
102     uint8_t event[17];
103     event[0] = L2CAP_EVENT_CHANNEL_OPENED;
104     event[1] = sizeof(event) - 2;
105     event[2] = status;
106     bt_flip_addr(&event[3], channel->address);
107     bt_store_16(event,  9, channel->handle);
108     bt_store_16(event, 11, channel->psm);
109     bt_store_16(event, 13, channel->local_cid);
110     bt_store_16(event, 15, channel->remote_cid);
111     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
112     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
113 }
114 
115 void l2cap_emit_channel_closed(l2cap_channel_t *channel) {
116     uint8_t event[4];
117     event[0] = L2CAP_EVENT_CHANNEL_CLOSED;
118     event[1] = sizeof(event) - 2;
119     bt_store_16(event, 2, channel->local_cid);
120     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
121     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
122 }
123 
124 void l2cap_emit_connection_request(l2cap_channel_t *channel) {
125     uint8_t event[16];
126     event[0] = L2CAP_EVENT_INCOMING_CONNECTION;
127     event[1] = sizeof(event) - 2;
128     bt_flip_addr(&event[2], channel->address);
129     bt_store_16(event,  8, channel->handle);
130     bt_store_16(event, 10, channel->psm);
131     bt_store_16(event, 12, channel->local_cid);
132     bt_store_16(event, 14, channel->remote_cid);
133     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
134     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
135 }
136 
137 void l2cap_emit_credits(l2cap_channel_t *channel, uint8_t credits) {
138     // track credits
139     channel->packets_granted += credits;
140     log_dbg("l2cap_emit_credits for cid %u, credits now: %u (+%u)\n", channel->local_cid, channel->packets_granted, credits);
141 
142     uint8_t event[5];
143     event[0] = L2CAP_EVENT_CREDITS;
144     event[1] = sizeof(event) - 2;
145     bt_store_16(event, 2, channel->local_cid);
146     event[4] = credits;
147     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
148     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
149 }
150 
151 void l2cap_hand_out_credits(){
152     linked_item_t *it;
153     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
154         if (!hci_number_free_acl_slots()) return;
155         l2cap_channel_t * channel = (l2cap_channel_t *) it;
156         if (channel->state != L2CAP_STATE_OPEN) continue;
157         if (hci_number_outgoing_packets(channel->handle) < 2 && channel->packets_granted == 0) {
158             l2cap_emit_credits(channel, 1);
159         }
160     }
161 }
162 
163 l2cap_channel_t * l2cap_get_channel_for_local_cid(uint16_t local_cid){
164     linked_item_t *it;
165     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
166         l2cap_channel_t * channel = (l2cap_channel_t *) it;
167         if ( channel->local_cid == local_cid) {
168             return channel;
169         }
170     }
171     return NULL;
172 }
173 
174 uint16_t l2cap_get_remote_mtu_for_local_cid(uint16_t local_cid){
175     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
176     if (channel) {
177         return channel->remote_mtu;
178     }
179     return 0;
180 }
181 
182 int l2cap_send_signaling_packet(hci_con_handle_t handle, L2CAP_SIGNALING_COMMANDS cmd, uint8_t identifier, ...){
183     // printf("l2cap_send_signaling_packet type %u\n", cmd);
184     va_list argptr;
185     va_start(argptr, identifier);
186     uint16_t len = l2cap_create_signaling_internal(sig_buffer, handle, cmd, identifier, argptr);
187     va_end(argptr);
188     return hci_send_acl_packet(sig_buffer, len);
189 }
190 
191 int l2cap_send_internal(uint16_t local_cid, uint8_t *data, uint16_t len){
192 
193     // check for free places on BT module
194     if (!hci_number_free_acl_slots()) {
195         log_dbg("l2cap_send_internal cid %u, BT module full <-----\n", local_cid);
196         return -1;
197     }
198     int err = 0;
199 
200     // find channel for local_cid, construct l2cap packet and send
201     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
202     if (channel) {
203         // track sending
204         ++channel->packets_outgoing;
205         if (channel->packets_granted > 0){
206             --channel->packets_granted;
207             // log_dbg("l2cap_send_internal cid %u, 1 credit used, credits left %u; outgoing count %u\n",
208             //        local_cid, channel->packets_granted, channel->packets_outgoing);
209         } else {
210             log_err("l2cap_send_internal cid %u, no credits!\n", local_cid);
211         }
212 
213         // 0 - Connection handle : PB=10 : BC=00
214         bt_store_16(acl_buffer, 0, channel->handle | (2 << 12) | (0 << 14));
215         // 2 - ACL length
216         bt_store_16(acl_buffer, 2,  len + 4);
217         // 4 - L2CAP packet length
218         bt_store_16(acl_buffer, 4,  len + 0);
219         // 6 - L2CAP channel DEST
220         bt_store_16(acl_buffer, 6, channel->remote_cid);
221         // 8 - data
222         memcpy(&acl_buffer[8], data, len);
223 
224         // send
225         err = hci_send_acl_packet(acl_buffer, len+8);
226     }
227     return err;
228 }
229 
230 // open outgoing L2CAP channel
231 void l2cap_create_channel_internal(void * connection, btstack_packet_handler_t packet_handler, bd_addr_t address, uint16_t psm){
232 
233     // alloc structure
234     l2cap_channel_t * chan = malloc(sizeof(l2cap_channel_t));
235     // TODO: emit error event
236     if (!chan) return;
237 
238     // fill in
239     BD_ADDR_COPY(chan->address, address);
240     chan->psm = psm;
241     chan->handle = 0;
242     chan->connection = connection;
243     chan->packet_handler = packet_handler;
244     chan->remote_mtu = L2CAP_MINIMAL_MTU;
245 
246     // flow control
247     chan->packets_granted = 0;
248     chan->packets_outgoing = 0;
249 
250     // set initial state
251     chan->state = L2CAP_STATE_CLOSED;
252     chan->sig_id = L2CAP_SIG_ID_INVALID;
253 
254     // add to connections list
255     linked_list_add(&l2cap_channels, (linked_item_t *) chan);
256 
257     // send connection request
258     // BD_ADDR, Packet_Type, Page_Scan_Repetition_Mode, Reserved, Clock_Offset, Allow_Role_Switch
259     hci_send_cmd(&hci_create_connection, address, 0x18, 0, 0, 0, 0);
260 }
261 
262 void l2cap_disconnect_internal(uint16_t local_cid, uint8_t reason){
263     // find channel for local_cid
264     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
265     if (channel) {
266         channel->sig_id = l2cap_next_sig_id();
267         l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->sig_id, channel->remote_cid, channel->local_cid);
268         channel->state = L2CAP_STATE_WAIT_DISCONNECT;
269     }
270 }
271 
272 static void l2cap_handle_connection_failed_for_addr(bd_addr_t address, uint8_t status){
273     linked_item_t *it;
274     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
275         l2cap_channel_t * channel = (l2cap_channel_t *) it;
276         if ( ! BD_ADDR_CMP( channel->address, address) ){
277             if (channel->state == L2CAP_STATE_CLOSED) {
278                 // failure, forward error code
279                 l2cap_emit_channel_opened(channel, status);
280                 // discard channel
281                 linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
282                 free (channel);
283             }
284         }
285     }
286 }
287 
288 static void l2cap_handle_connection_success_for_addr(bd_addr_t address, hci_con_handle_t handle){
289     linked_item_t *it;
290     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
291         l2cap_channel_t * channel = (l2cap_channel_t *) it;
292         if ( ! BD_ADDR_CMP( channel->address, address) ){
293             if (channel->state == L2CAP_STATE_CLOSED) {
294                 // success, start l2cap handshake
295                 channel->handle = handle;
296                 channel->sig_id = l2cap_next_sig_id();
297                 channel->local_cid = l2cap_next_local_cid();
298                 channel->state = L2CAP_STATE_WAIT_CONNECT_RSP;
299                 l2cap_send_signaling_packet( channel->handle, CONNECTION_REQUEST, channel->sig_id, channel->psm, channel->local_cid);
300             }
301         }
302     }
303 }
304 
305 void l2cap_event_handler( uint8_t *packet, uint16_t size ){
306 
307     bd_addr_t address;
308     hci_con_handle_t handle;
309     linked_item_t *it;
310     int i;
311 
312     switch(packet[0]){
313 
314         // handle connection complete events
315         case HCI_EVENT_CONNECTION_COMPLETE:
316             bt_flip_addr(address, &packet[5]);
317             if (packet[2] == 0){
318                 handle = READ_BT_16(packet, 3);
319                 l2cap_handle_connection_success_for_addr(address, handle);
320             } else {
321                 l2cap_handle_connection_failed_for_addr(address, packet[2]);
322             }
323             break;
324 
325         // handle successful create connection cancel command
326         case HCI_EVENT_COMMAND_COMPLETE:
327             if ( COMMAND_COMPLETE_EVENT(packet, hci_create_connection_cancel) ) {
328                 if (packet[5] == 0){
329                     bt_flip_addr(address, &packet[6]);
330                     // CONNECTION TERMINATED BY LOCAL HOST (0X16)
331                     l2cap_handle_connection_failed_for_addr(address, 0x16);
332                 }
333             }
334             break;
335 
336         // handle disconnection complete events
337         case HCI_EVENT_DISCONNECTION_COMPLETE:
338             // send l2cap disconnect events for all channels on this handle
339             handle = READ_BT_16(packet, 3);
340             // only access next element to allows for removal
341             for (it = (linked_item_t *) &l2cap_channels; it->next ; it = it->next){
342                 l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
343                 if ( channel->handle == handle ){
344                     // update prev item before free'ing next element
345                     it->next = it->next->next;
346                     l2cap_finialize_channel_close(channel);
347                 }
348             }
349             break;
350 
351         case HCI_EVENT_NUMBER_OF_COMPLETED_PACKETS:
352             for (i=0; i<packet[2];i++){
353                 handle = READ_BT_16(packet, 3 + 2*i);
354                 uint16_t num_packets = READ_BT_16(packet, 3 + packet[2]*2 + 2*i);
355                 while (num_packets) {
356 
357                     // find channels with max nr of pending outgoing packets
358                     l2cap_channel_t * fullest_channel = NULL;
359                     int max_nr_pending = 0;
360                     for (it = (linked_item_t *) &l2cap_channels; it->next ; it = it->next){
361                         l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
362                         if (channel->packets_outgoing > max_nr_pending){
363                             fullest_channel = channel;
364                             max_nr_pending  = channel->packets_outgoing;
365                         }
366                     }
367 
368                     // decrease packets
369                     if (fullest_channel) {
370                         fullest_channel->packets_outgoing--;
371                         // log_dbg("hci_number_completed_packet (l2cap) for cid %u, outgoing count %u\n",
372                         //        fullest_channel->local_cid, fullest_channel->packets_outgoing);
373                     } else {
374                         log_err("hci_number_completed_packet but no outgoing packet in records\n");
375                     }
376 
377                     // handled!
378                     num_packets--;
379                 }
380             }
381             l2cap_hand_out_credits();
382             break;
383 
384         // HCI Connection Timeouts
385         case L2CAP_EVENT_TIMEOUT_CHECK:
386             handle = READ_BT_16(packet, 2);
387             l2cap_channel_t * channel;
388             int used = 0;
389             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
390                 channel = (l2cap_channel_t *) it;
391                 if (channel->handle == handle) {
392                     used = 1;
393                 }
394             }
395             if (!used) {
396                 hci_send_cmd(&hci_disconnect, handle, 0x13); // remote closed connection
397             }
398             break;
399 
400         default:
401             break;
402     }
403 
404     // pass on
405     (*packet_handler)(NULL, HCI_EVENT_PACKET, 0, packet, size);
406 }
407 
408 static void l2cap_handle_disconnect_request(l2cap_channel_t *channel, uint16_t identifier){
409     l2cap_send_signaling_packet( channel->handle, DISCONNECTION_RESPONSE, identifier, channel->local_cid, channel->remote_cid);
410     l2cap_finialize_channel_close(channel);
411 }
412 
413 static void l2cap_handle_connection_request(hci_con_handle_t handle, uint8_t sig_id, uint16_t psm, uint16_t source_cid){
414 
415     // printf("l2cap_handle_connection_request for handle %u, psm %u cid %u\n", handle, psm, source_cid);
416     l2cap_service_t *service = l2cap_get_service(psm);
417     if (!service) {
418         // 0x0002 PSM not supported
419         // printf("l2cap_handle_connection_request no PSM for psm %u/n", psm);
420         l2cap_send_signaling_packet(handle, CONNECTION_RESPONSE, sig_id, 0, 0, 0x0002, 0);
421         return;
422     }
423 
424     hci_connection_t * hci_connection = connection_for_handle( handle );
425     if (!hci_connection) {
426         fprintf(stderr, "no hci_connection for handle %u\n", handle);
427         // TODO: emit error
428         return;
429     }
430     // alloc structure
431     // printf("l2cap_handle_connection_request register channel\n");
432     l2cap_channel_t * channel = malloc(sizeof(l2cap_channel_t));
433     // TODO: emit error event
434     if (!channel) return;
435 
436     // fill in
437     BD_ADDR_COPY(channel->address, hci_connection->address);
438     channel->psm = psm;
439     channel->handle = handle;
440     channel->connection = service->connection;
441     channel->packet_handler = service->packet_handler;
442     channel->local_cid  = l2cap_next_local_cid();
443     channel->remote_cid = source_cid;
444     channel->remote_mtu = L2CAP_MINIMAL_MTU;
445 
446     // set initial state
447     channel->state = L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT;
448 
449     // temp. store req sig id
450     channel->sig_id = sig_id;
451 
452     // add to connections list
453     linked_list_add(&l2cap_channels, (linked_item_t *) channel);
454 
455     // emit incoming connection request
456     l2cap_emit_connection_request(channel);
457 }
458 
459 void l2cap_accept_connection_internal(uint16_t local_cid){
460     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
461     if (!channel) {
462         fprintf(stderr, "l2cap_accept_connection_internal called but local_cid 0x%x not found", local_cid);
463         return;
464     }
465 
466     // accept connection
467     l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->sig_id, channel->local_cid, channel->remote_cid, 0, 0);
468 
469     // set real sig and state and start config
470     channel->sig_id = l2cap_next_sig_id();
471     channel->state  = L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ;
472     l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->sig_id, channel->remote_cid, 0, 4, &config_options);
473 
474     // printf("new state %u\n", channel->state);
475 }
476 
477 void l2cap_decline_connection_internal(uint16_t local_cid, uint8_t reason){
478     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid( local_cid);
479     if (!channel) {
480         fprintf(stderr, "l2cap_decline_connection_internal called but local_cid 0x%x not found", local_cid);
481         return;
482     }
483     l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->sig_id, 0, 0, reason, 0);
484 
485     // discard channel
486     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
487     free (channel);
488 }
489 
490 void l2cap_signaling_handle_configure_request(l2cap_channel_t *channel, uint8_t *command){
491     // accept the other's configuration options
492     uint16_t end_pos = 4 + READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
493     uint16_t pos     = 8;
494     while (pos < end_pos){
495         uint8_t type   = command[pos++];
496         uint8_t length = command[pos++];
497         // MTU { type(8): 1, len(8):2, MTU(16) }
498         if ((type & 0x7f) == 1 && length == 2){
499             channel->remote_mtu = READ_BT_16(command, pos);
500             // printf("l2cap cid %u, remote mtu %u\n", channel->local_cid, channel->remote_mtu);
501         }
502         pos += length;
503     }
504     uint8_t identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
505     // send back received options
506     // l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, identifier, channel->remote_cid, 0, 0, len-4, &command[8]);
507     // send back OK
508     l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, identifier, channel->remote_cid, 0, 0, 0, NULL);
509 }
510 
511 void l2cap_signaling_handler_channel(l2cap_channel_t *channel, uint8_t *command){
512 
513     uint8_t code       = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
514     uint8_t identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
515     uint16_t result = 0;
516 
517     // printf("signaling handler code %u\n", code);
518 
519     switch (channel->state) {
520 
521         case L2CAP_STATE_WAIT_CONNECT_RSP:
522             switch (code){
523                 case CONNECTION_RESPONSE:
524                     result = READ_BT_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
525                     switch (result) {
526                         case 0:
527                             // successful connection
528                             channel->remote_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
529                             channel->sig_id = l2cap_next_sig_id();
530                             l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->sig_id, channel->remote_cid, 0, 4, &config_options);
531                             channel->state = L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ;
532                             break;
533                         case 1:
534                             // connection pending. get some coffee
535                             break;
536                         default:
537                             // map l2cap connection response result to BTstack status enumeration
538                             l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result);
539                             break;
540                     }
541                     break;
542 
543                 case DISCONNECTION_REQUEST:
544                     l2cap_handle_disconnect_request(channel, identifier);
545                     break;
546 
547                 default:
548                     //@TODO: implement other signaling packets
549                     break;
550             }
551             break;
552 
553         case L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ:
554             switch (code) {
555                 case CONFIGURE_RESPONSE:
556                     channel->state = L2CAP_STATE_WAIT_CONFIG_REQ;
557                     break;
558                 case CONFIGURE_REQUEST:
559                     l2cap_signaling_handle_configure_request(channel, command);
560                     channel->state = L2CAP_STATE_WAIT_CONFIG_REQ_RSP;
561                     break;
562                 case DISCONNECTION_REQUEST:
563                     l2cap_handle_disconnect_request(channel, identifier);
564                     break;
565                 default:
566                     //@TODO: implement other signaling packets
567                     break;
568             }
569             break;
570 
571         case L2CAP_STATE_WAIT_CONFIG_REQ:
572             switch (code) {
573                 case CONFIGURE_REQUEST:
574                     l2cap_signaling_handle_configure_request(channel, command);
575                     channel->state = L2CAP_STATE_OPEN;
576                     l2cap_emit_channel_opened(channel, 0);  // success
577                     l2cap_emit_credits(channel, 1);
578                     break;
579                 case DISCONNECTION_REQUEST:
580                     l2cap_handle_disconnect_request(channel, identifier);
581                     break;
582                 default:
583                     //@TODO: implement other signaling packets
584                     break;
585             }
586             break;
587 
588         case L2CAP_STATE_WAIT_CONFIG_REQ_RSP:
589             switch (code) {
590                 case CONFIGURE_RESPONSE:
591                     channel->state = L2CAP_STATE_OPEN;
592                     l2cap_emit_channel_opened(channel, 0);  // success
593                     l2cap_emit_credits(channel, 1);
594                     break;
595                 case DISCONNECTION_REQUEST:
596                     l2cap_handle_disconnect_request(channel, identifier);
597                     break;
598                 default:
599                     //@TODO: implement other signaling packets
600                     break;
601             }
602             break;
603 
604         case L2CAP_STATE_WAIT_DISCONNECT:
605             switch (code) {
606                 case DISCONNECTION_RESPONSE:
607                     l2cap_finialize_channel_close(channel);
608                     break;
609                 case DISCONNECTION_REQUEST:
610                     l2cap_handle_disconnect_request(channel, identifier);
611                     break;
612                 default:
613                     //@TODO: implement other signaling packets
614                     break;
615             }
616             break;
617 
618         case L2CAP_STATE_CLOSED:
619             // @TODO handle incoming requests
620             break;
621 
622         case L2CAP_STATE_OPEN:
623             switch (code) {
624                 case DISCONNECTION_REQUEST:
625                     l2cap_handle_disconnect_request(channel, identifier);
626                     break;
627                 default:
628                     //@TODO: implement other signaling packets, e.g. re-configure
629                     break;
630             }
631             break;
632         default:
633             break;
634     }
635     // printf("new state %u\n", channel->state);
636 }
637 
638 
639 void l2cap_signaling_handler_dispatch( hci_con_handle_t handle, uint8_t * command){
640 
641     // get code, signalind identifier and command len
642     uint8_t code   = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
643     uint8_t sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
644     uint16_t len   = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
645 
646     // not for a particular channel, and not CONNECTION_REQUEST, ECHO_[REQUEST|RESPONSE], INFORMATION_REQUEST
647     if (code < 1 || code == ECHO_RESPONSE || code > INFORMATION_REQUEST){
648         return;
649     }
650 
651     // general commands without an assigned channel
652     switch(code) {
653 
654         case CONNECTION_REQUEST: {
655             uint16_t psm =        READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
656             uint16_t source_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+2);
657             l2cap_handle_connection_request(handle, sig_id, psm, source_cid);
658             break;
659         }
660 
661         case ECHO_REQUEST: {
662             // send back packet
663             l2cap_send_signaling_packet(handle, ECHO_RESPONSE, sig_id, len, &command[L2CAP_SIGNALING_COMMAND_DATA_OFFSET]);
664             break;
665         }
666 
667         case INFORMATION_REQUEST: {
668             // we neither support connectionless L2CAP data nor support any flow control modes yet
669             uint16_t infoType = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
670             if (infoType == 2) {
671                 uint32_t features = 0;
672                 // extended features request supported, however no features present
673                 l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, 4, &features);
674             } else {
675                 // all other types are not supported
676                 l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 1, 0, NULL);
677             }
678             break;;
679         }
680 
681         default:
682             break;
683     }
684 
685 
686     // Get potential destination CID
687     uint16_t dest_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
688 
689     // Find channel for this sig_id and connection handle
690     linked_item_t *it;
691     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
692         l2cap_channel_t * channel = (l2cap_channel_t *) it;
693         if (channel->handle == handle) {
694             if (code & 1) {
695                 // match odd commands by previous signaling identifier
696                 if (channel->sig_id == sig_id) {
697                     l2cap_signaling_handler_channel(channel, command);
698                 }
699             } else {
700                 // match even commands by local channel id
701                 if (channel->local_cid == dest_cid) {
702                     l2cap_signaling_handler_channel(channel, command);
703                 }
704             }
705         }
706     }
707 }
708 
709 void l2cap_acl_handler( uint8_t *packet, uint16_t size ){
710 
711     // Get Channel ID
712     uint16_t channel_id = READ_L2CAP_CHANNEL_ID(packet);
713 
714     // Signaling Packet?
715     if (channel_id == 1) {
716 
717         // Get Connection
718         hci_con_handle_t handle = READ_ACL_CONNECTION_HANDLE(packet);
719 
720         uint16_t command_offset = 8;
721         while (command_offset < size) {
722 
723             // handle signaling commands
724             l2cap_signaling_handler_dispatch(handle, &packet[command_offset]);
725 
726             // increment command_offset
727             command_offset += L2CAP_SIGNALING_COMMAND_DATA_OFFSET + READ_BT_16(packet, command_offset + L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
728         }
729         return;
730     }
731 
732     // Find channel for this channel_id and connection handle
733     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(channel_id);
734     if (channel) {
735         l2cap_dispatch(channel, L2CAP_DATA_PACKET, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
736     }
737 }
738 
739 static void l2cap_packet_handler(uint8_t packet_type, uint8_t *packet, uint16_t size){
740     switch (packet_type) {
741         case HCI_EVENT_PACKET:
742             l2cap_event_handler(packet, size);
743             break;
744         case HCI_ACL_DATA_PACKET:
745             l2cap_acl_handler(packet, size);
746             break;
747         default:
748             break;
749     }
750 }
751 
752 // finalize closed channel
753 void l2cap_finialize_channel_close(l2cap_channel_t *channel){
754     channel->state = L2CAP_STATE_CLOSED;
755     l2cap_emit_channel_closed(channel);
756 
757     // discard channel
758     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
759     free (channel);
760 }
761 
762 l2cap_service_t * l2cap_get_service(uint16_t psm){
763     linked_item_t *it;
764 
765     // close open channels
766     for (it = (linked_item_t *) l2cap_services; it ; it = it->next){
767         l2cap_service_t * service = ((l2cap_service_t *) it);
768         if ( service->psm == psm){
769             return service;
770         };
771     }
772     return NULL;
773 }
774 
775 void l2cap_register_service_internal(void *connection, btstack_packet_handler_t packet_handler, uint16_t psm, uint16_t mtu){
776     // check for alread registered psm // TODO: emit error event
777     l2cap_service_t *service = l2cap_get_service(psm);
778     if (service) return;
779 
780     // alloc structure     // TODO: emit error event
781     service = malloc(sizeof(l2cap_service_t));
782     if (!service) return;
783 
784     // fill in
785     service->psm = psm;
786     service->mtu = mtu;
787     service->connection = connection;
788     service->packet_handler = packet_handler;
789 
790     // add to services list
791     linked_list_add(&l2cap_services, (linked_item_t *) service);
792 }
793 
794 void l2cap_unregister_service_internal(void *connection, uint16_t psm){
795     l2cap_service_t *service = l2cap_get_service(psm);
796     if (!service) return;
797     linked_list_remove(&l2cap_services, (linked_item_t *) service);
798     free(service);
799 }
800 
801 //
802 void l2cap_close_connection(void *connection){
803     linked_item_t *it;
804 
805     // close open channels
806     l2cap_channel_t * channel;
807     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
808         channel = (l2cap_channel_t *) it;
809         if (channel->connection == connection) {
810             channel->sig_id = l2cap_next_sig_id();
811             l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->sig_id, channel->remote_cid, channel->local_cid);
812             channel->state = L2CAP_STATE_WAIT_DISCONNECT;
813         }
814     }
815 
816     // unregister services
817     it = (linked_item_t *) &l2cap_services;
818     while (it->next){
819         l2cap_service_t * service = (l2cap_service_t *) it->next;
820         if (service->connection == connection){
821             it->next = it->next->next;
822             free(service);
823         } else {
824             it = it->next;
825         }
826     }
827 }
828