xref: /btstack/src/l2cap.c (revision 91b99603acd89769b67646246bed2905175e23af)
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 
228     l2cap_hand_out_credits();
229 
230     return err;
231 }
232 
233 // open outgoing L2CAP channel
234 void l2cap_create_channel_internal(void * connection, btstack_packet_handler_t packet_handler, bd_addr_t address, uint16_t psm){
235 
236     // alloc structure
237     l2cap_channel_t * chan = malloc(sizeof(l2cap_channel_t));
238     // TODO: emit error event
239     if (!chan) return;
240 
241     // fill in
242     BD_ADDR_COPY(chan->address, address);
243     chan->psm = psm;
244     chan->handle = 0;
245     chan->connection = connection;
246     chan->packet_handler = packet_handler;
247     chan->remote_mtu = L2CAP_MINIMAL_MTU;
248 
249     // flow control
250     chan->packets_granted = 0;
251     chan->packets_outgoing = 0;
252 
253     // set initial state
254     chan->state = L2CAP_STATE_CLOSED;
255     chan->sig_id = L2CAP_SIG_ID_INVALID;
256 
257     // add to connections list
258     linked_list_add(&l2cap_channels, (linked_item_t *) chan);
259 
260     // send connection request
261     // BD_ADDR, Packet_Type, Page_Scan_Repetition_Mode, Reserved, Clock_Offset, Allow_Role_Switch
262     hci_send_cmd(&hci_create_connection, address, 0x18, 0, 0, 0, 0);
263 }
264 
265 void l2cap_disconnect_internal(uint16_t local_cid, uint8_t reason){
266     // find channel for local_cid
267     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
268     if (channel) {
269         channel->sig_id = l2cap_next_sig_id();
270         l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->sig_id, channel->remote_cid, channel->local_cid);
271         channel->state = L2CAP_STATE_WAIT_DISCONNECT;
272     }
273 }
274 
275 static void l2cap_handle_connection_failed_for_addr(bd_addr_t address, uint8_t status){
276     linked_item_t *it;
277     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
278         l2cap_channel_t * channel = (l2cap_channel_t *) it;
279         if ( ! BD_ADDR_CMP( channel->address, address) ){
280             if (channel->state == L2CAP_STATE_CLOSED) {
281                 // failure, forward error code
282                 l2cap_emit_channel_opened(channel, status);
283                 // discard channel
284                 linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
285                 free (channel);
286             }
287         }
288     }
289 }
290 
291 static void l2cap_handle_connection_success_for_addr(bd_addr_t address, hci_con_handle_t handle){
292     linked_item_t *it;
293     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
294         l2cap_channel_t * channel = (l2cap_channel_t *) it;
295         if ( ! BD_ADDR_CMP( channel->address, address) ){
296             if (channel->state == L2CAP_STATE_CLOSED) {
297                 // success, start l2cap handshake
298                 channel->handle = handle;
299                 channel->sig_id = l2cap_next_sig_id();
300                 channel->local_cid = l2cap_next_local_cid();
301                 channel->state = L2CAP_STATE_WAIT_CONNECT_RSP;
302                 l2cap_send_signaling_packet( channel->handle, CONNECTION_REQUEST, channel->sig_id, channel->psm, channel->local_cid);
303             }
304         }
305     }
306 }
307 
308 void l2cap_event_handler( uint8_t *packet, uint16_t size ){
309 
310     bd_addr_t address;
311     hci_con_handle_t handle;
312     linked_item_t *it;
313     int i;
314 
315     switch(packet[0]){
316 
317         // handle connection complete events
318         case HCI_EVENT_CONNECTION_COMPLETE:
319             bt_flip_addr(address, &packet[5]);
320             if (packet[2] == 0){
321                 handle = READ_BT_16(packet, 3);
322                 l2cap_handle_connection_success_for_addr(address, handle);
323             } else {
324                 l2cap_handle_connection_failed_for_addr(address, packet[2]);
325             }
326             break;
327 
328         // handle successful create connection cancel command
329         case HCI_EVENT_COMMAND_COMPLETE:
330             if ( COMMAND_COMPLETE_EVENT(packet, hci_create_connection_cancel) ) {
331                 if (packet[5] == 0){
332                     bt_flip_addr(address, &packet[6]);
333                     // CONNECTION TERMINATED BY LOCAL HOST (0X16)
334                     l2cap_handle_connection_failed_for_addr(address, 0x16);
335                 }
336             }
337             break;
338 
339         // handle disconnection complete events
340         case HCI_EVENT_DISCONNECTION_COMPLETE:
341             // send l2cap disconnect events for all channels on this handle
342             handle = READ_BT_16(packet, 3);
343             // only access next element to allows for removal
344             for (it = (linked_item_t *) &l2cap_channels; it->next ; it = it->next){
345                 l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
346                 if ( channel->handle == handle ){
347                     // update prev item before free'ing next element
348                     it->next = it->next->next;
349                     l2cap_finialize_channel_close(channel);
350                 }
351             }
352             break;
353 
354         case HCI_EVENT_NUMBER_OF_COMPLETED_PACKETS:
355             for (i=0; i<packet[2];i++){
356                 handle = READ_BT_16(packet, 3 + 2*i);
357                 uint16_t num_packets = READ_BT_16(packet, 3 + packet[2]*2 + 2*i);
358                 while (num_packets) {
359 
360                     // find channels with max nr of pending outgoing packets
361                     l2cap_channel_t * fullest_channel = NULL;
362                     int max_nr_pending = 0;
363                     for (it = (linked_item_t *) &l2cap_channels; it->next ; it = it->next){
364                         l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
365                         if (channel->packets_outgoing > max_nr_pending){
366                             fullest_channel = channel;
367                             max_nr_pending  = channel->packets_outgoing;
368                         }
369                     }
370 
371                     // decrease packets
372                     if (fullest_channel) {
373                         fullest_channel->packets_outgoing--;
374                         // log_dbg("hci_number_completed_packet (l2cap) for cid %u, outgoing count %u\n",
375                         //        fullest_channel->local_cid, fullest_channel->packets_outgoing);
376                     } else {
377                         log_err("hci_number_completed_packet but no outgoing packet in records\n");
378                     }
379 
380                     // handled!
381                     num_packets--;
382                 }
383             }
384             l2cap_hand_out_credits();
385             break;
386 
387         // HCI Connection Timeouts
388         case L2CAP_EVENT_TIMEOUT_CHECK:
389             handle = READ_BT_16(packet, 2);
390             l2cap_channel_t * channel;
391             int used = 0;
392             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
393                 channel = (l2cap_channel_t *) it;
394                 if (channel->handle == handle) {
395                     used = 1;
396                 }
397             }
398             if (!used) {
399                 hci_send_cmd(&hci_disconnect, handle, 0x13); // remote closed connection
400             }
401             break;
402 
403         default:
404             break;
405     }
406 
407     // pass on
408     (*packet_handler)(NULL, HCI_EVENT_PACKET, 0, packet, size);
409 }
410 
411 static void l2cap_handle_disconnect_request(l2cap_channel_t *channel, uint16_t identifier){
412     l2cap_send_signaling_packet( channel->handle, DISCONNECTION_RESPONSE, identifier, channel->local_cid, channel->remote_cid);
413     l2cap_finialize_channel_close(channel);
414 }
415 
416 static void l2cap_handle_connection_request(hci_con_handle_t handle, uint8_t sig_id, uint16_t psm, uint16_t source_cid){
417 
418     // printf("l2cap_handle_connection_request for handle %u, psm %u cid %u\n", handle, psm, source_cid);
419     l2cap_service_t *service = l2cap_get_service(psm);
420     if (!service) {
421         // 0x0002 PSM not supported
422         // printf("l2cap_handle_connection_request no PSM for psm %u/n", psm);
423         l2cap_send_signaling_packet(handle, CONNECTION_RESPONSE, sig_id, 0, 0, 0x0002, 0);
424         return;
425     }
426 
427     hci_connection_t * hci_connection = connection_for_handle( handle );
428     if (!hci_connection) {
429         fprintf(stderr, "no hci_connection for handle %u\n", handle);
430         // TODO: emit error
431         return;
432     }
433     // alloc structure
434     // printf("l2cap_handle_connection_request register channel\n");
435     l2cap_channel_t * channel = malloc(sizeof(l2cap_channel_t));
436     // TODO: emit error event
437     if (!channel) return;
438 
439     // fill in
440     BD_ADDR_COPY(channel->address, hci_connection->address);
441     channel->psm = psm;
442     channel->handle = handle;
443     channel->connection = service->connection;
444     channel->packet_handler = service->packet_handler;
445     channel->local_cid  = l2cap_next_local_cid();
446     channel->remote_cid = source_cid;
447     channel->remote_mtu = L2CAP_MINIMAL_MTU;
448 
449     // set initial state
450     channel->state = L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT;
451 
452     // temp. store req sig id
453     channel->sig_id = sig_id;
454 
455     // add to connections list
456     linked_list_add(&l2cap_channels, (linked_item_t *) channel);
457 
458     // emit incoming connection request
459     l2cap_emit_connection_request(channel);
460 }
461 
462 void l2cap_accept_connection_internal(uint16_t local_cid){
463     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
464     if (!channel) {
465         fprintf(stderr, "l2cap_accept_connection_internal called but local_cid 0x%x not found", local_cid);
466         return;
467     }
468 
469     // accept connection
470     l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->sig_id, channel->local_cid, channel->remote_cid, 0, 0);
471 
472     // set real sig and state and start config
473     channel->sig_id = l2cap_next_sig_id();
474     channel->state  = L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ;
475     l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->sig_id, channel->remote_cid, 0, 4, &config_options);
476 
477     // printf("new state %u\n", channel->state);
478 }
479 
480 void l2cap_decline_connection_internal(uint16_t local_cid, uint8_t reason){
481     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid( local_cid);
482     if (!channel) {
483         fprintf(stderr, "l2cap_decline_connection_internal called but local_cid 0x%x not found", local_cid);
484         return;
485     }
486     l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->sig_id, 0, 0, reason, 0);
487 
488     // discard channel
489     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
490     free (channel);
491 }
492 
493 void l2cap_signaling_handle_configure_request(l2cap_channel_t *channel, uint8_t *command){
494     // accept the other's configuration options
495     uint16_t end_pos = 4 + READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
496     uint16_t pos     = 8;
497     while (pos < end_pos){
498         uint8_t type   = command[pos++];
499         uint8_t length = command[pos++];
500         // MTU { type(8): 1, len(8):2, MTU(16) }
501         if ((type & 0x7f) == 1 && length == 2){
502             channel->remote_mtu = READ_BT_16(command, pos);
503             // printf("l2cap cid %u, remote mtu %u\n", channel->local_cid, channel->remote_mtu);
504         }
505         pos += length;
506     }
507     uint8_t identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
508     // send back received options
509     // l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, identifier, channel->remote_cid, 0, 0, len-4, &command[8]);
510     // send back OK
511     l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, identifier, channel->remote_cid, 0, 0, 0, NULL);
512 }
513 
514 void l2cap_signaling_handler_channel(l2cap_channel_t *channel, uint8_t *command){
515 
516     uint8_t code       = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
517     uint8_t identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
518     uint16_t result = 0;
519 
520     // printf("signaling handler code %u\n", code);
521 
522     switch (channel->state) {
523 
524         case L2CAP_STATE_WAIT_CONNECT_RSP:
525             switch (code){
526                 case CONNECTION_RESPONSE:
527                     result = READ_BT_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
528                     switch (result) {
529                         case 0:
530                             // successful connection
531                             channel->remote_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
532                             channel->sig_id = l2cap_next_sig_id();
533                             l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->sig_id, channel->remote_cid, 0, 4, &config_options);
534                             channel->state = L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ;
535                             break;
536                         case 1:
537                             // connection pending. get some coffee
538                             break;
539                         default:
540                             // map l2cap connection response result to BTstack status enumeration
541                             l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result);
542                             break;
543                     }
544                     break;
545 
546                 case DISCONNECTION_REQUEST:
547                     l2cap_handle_disconnect_request(channel, identifier);
548                     break;
549 
550                 default:
551                     //@TODO: implement other signaling packets
552                     break;
553             }
554             break;
555 
556         case L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ:
557             switch (code) {
558                 case CONFIGURE_RESPONSE:
559                     channel->state = L2CAP_STATE_WAIT_CONFIG_REQ;
560                     break;
561                 case CONFIGURE_REQUEST:
562                     l2cap_signaling_handle_configure_request(channel, command);
563                     channel->state = L2CAP_STATE_WAIT_CONFIG_REQ_RSP;
564                     break;
565                 case DISCONNECTION_REQUEST:
566                     l2cap_handle_disconnect_request(channel, identifier);
567                     break;
568                 default:
569                     //@TODO: implement other signaling packets
570                     break;
571             }
572             break;
573 
574         case L2CAP_STATE_WAIT_CONFIG_REQ:
575             switch (code) {
576                 case CONFIGURE_REQUEST:
577                     l2cap_signaling_handle_configure_request(channel, command);
578                     channel->state = L2CAP_STATE_OPEN;
579                     l2cap_emit_channel_opened(channel, 0);  // success
580                     l2cap_emit_credits(channel, 1);
581                     break;
582                 case DISCONNECTION_REQUEST:
583                     l2cap_handle_disconnect_request(channel, identifier);
584                     break;
585                 default:
586                     //@TODO: implement other signaling packets
587                     break;
588             }
589             break;
590 
591         case L2CAP_STATE_WAIT_CONFIG_REQ_RSP:
592             switch (code) {
593                 case CONFIGURE_RESPONSE:
594                     channel->state = L2CAP_STATE_OPEN;
595                     l2cap_emit_channel_opened(channel, 0);  // success
596                     l2cap_emit_credits(channel, 1);
597                     break;
598                 case DISCONNECTION_REQUEST:
599                     l2cap_handle_disconnect_request(channel, identifier);
600                     break;
601                 default:
602                     //@TODO: implement other signaling packets
603                     break;
604             }
605             break;
606 
607         case L2CAP_STATE_WAIT_DISCONNECT:
608             switch (code) {
609                 case DISCONNECTION_RESPONSE:
610                     l2cap_finialize_channel_close(channel);
611                     break;
612                 case DISCONNECTION_REQUEST:
613                     l2cap_handle_disconnect_request(channel, identifier);
614                     break;
615                 default:
616                     //@TODO: implement other signaling packets
617                     break;
618             }
619             break;
620 
621         case L2CAP_STATE_CLOSED:
622             // @TODO handle incoming requests
623             break;
624 
625         case L2CAP_STATE_OPEN:
626             switch (code) {
627                 case DISCONNECTION_REQUEST:
628                     l2cap_handle_disconnect_request(channel, identifier);
629                     break;
630                 default:
631                     //@TODO: implement other signaling packets, e.g. re-configure
632                     break;
633             }
634             break;
635         default:
636             break;
637     }
638     // printf("new state %u\n", channel->state);
639 }
640 
641 
642 void l2cap_signaling_handler_dispatch( hci_con_handle_t handle, uint8_t * command){
643 
644     // get code, signalind identifier and command len
645     uint8_t code   = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
646     uint8_t sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
647     uint16_t len   = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
648 
649     // not for a particular channel, and not CONNECTION_REQUEST, ECHO_[REQUEST|RESPONSE], INFORMATION_REQUEST
650     if (code < 1 || code == ECHO_RESPONSE || code > INFORMATION_REQUEST){
651         return;
652     }
653 
654     // general commands without an assigned channel
655     switch(code) {
656 
657         case CONNECTION_REQUEST: {
658             uint16_t psm =        READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
659             uint16_t source_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+2);
660             l2cap_handle_connection_request(handle, sig_id, psm, source_cid);
661             break;
662         }
663 
664         case ECHO_REQUEST: {
665             // send back packet
666             l2cap_send_signaling_packet(handle, ECHO_RESPONSE, sig_id, len, &command[L2CAP_SIGNALING_COMMAND_DATA_OFFSET]);
667             break;
668         }
669 
670         case INFORMATION_REQUEST: {
671             // we neither support connectionless L2CAP data nor support any flow control modes yet
672             uint16_t infoType = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
673             if (infoType == 2) {
674                 uint32_t features = 0;
675                 // extended features request supported, however no features present
676                 l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, 4, &features);
677             } else {
678                 // all other types are not supported
679                 l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 1, 0, NULL);
680             }
681             break;;
682         }
683 
684         default:
685             break;
686     }
687 
688 
689     // Get potential destination CID
690     uint16_t dest_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
691 
692     // Find channel for this sig_id and connection handle
693     linked_item_t *it;
694     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
695         l2cap_channel_t * channel = (l2cap_channel_t *) it;
696         if (channel->handle == handle) {
697             if (code & 1) {
698                 // match odd commands by previous signaling identifier
699                 if (channel->sig_id == sig_id) {
700                     l2cap_signaling_handler_channel(channel, command);
701                 }
702             } else {
703                 // match even commands by local channel id
704                 if (channel->local_cid == dest_cid) {
705                     l2cap_signaling_handler_channel(channel, command);
706                 }
707             }
708         }
709     }
710 }
711 
712 void l2cap_acl_handler( uint8_t *packet, uint16_t size ){
713 
714     // Get Channel ID
715     uint16_t channel_id = READ_L2CAP_CHANNEL_ID(packet);
716 
717     // Signaling Packet?
718     if (channel_id == 1) {
719 
720         // Get Connection
721         hci_con_handle_t handle = READ_ACL_CONNECTION_HANDLE(packet);
722 
723         uint16_t command_offset = 8;
724         while (command_offset < size) {
725 
726             // handle signaling commands
727             l2cap_signaling_handler_dispatch(handle, &packet[command_offset]);
728 
729             // increment command_offset
730             command_offset += L2CAP_SIGNALING_COMMAND_DATA_OFFSET + READ_BT_16(packet, command_offset + L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
731         }
732         return;
733     }
734 
735     // Find channel for this channel_id and connection handle
736     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(channel_id);
737     if (channel) {
738         l2cap_dispatch(channel, L2CAP_DATA_PACKET, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
739     }
740 }
741 
742 static void l2cap_packet_handler(uint8_t packet_type, uint8_t *packet, uint16_t size){
743     switch (packet_type) {
744         case HCI_EVENT_PACKET:
745             l2cap_event_handler(packet, size);
746             break;
747         case HCI_ACL_DATA_PACKET:
748             l2cap_acl_handler(packet, size);
749             break;
750         default:
751             break;
752     }
753 }
754 
755 // finalize closed channel
756 void l2cap_finialize_channel_close(l2cap_channel_t *channel){
757     channel->state = L2CAP_STATE_CLOSED;
758     l2cap_emit_channel_closed(channel);
759 
760     // discard channel
761     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
762     free (channel);
763 }
764 
765 l2cap_service_t * l2cap_get_service(uint16_t psm){
766     linked_item_t *it;
767 
768     // close open channels
769     for (it = (linked_item_t *) l2cap_services; it ; it = it->next){
770         l2cap_service_t * service = ((l2cap_service_t *) it);
771         if ( service->psm == psm){
772             return service;
773         };
774     }
775     return NULL;
776 }
777 
778 void l2cap_register_service_internal(void *connection, btstack_packet_handler_t packet_handler, uint16_t psm, uint16_t mtu){
779     // check for alread registered psm // TODO: emit error event
780     l2cap_service_t *service = l2cap_get_service(psm);
781     if (service) return;
782 
783     // alloc structure     // TODO: emit error event
784     service = malloc(sizeof(l2cap_service_t));
785     if (!service) return;
786 
787     // fill in
788     service->psm = psm;
789     service->mtu = mtu;
790     service->connection = connection;
791     service->packet_handler = packet_handler;
792 
793     // add to services list
794     linked_list_add(&l2cap_services, (linked_item_t *) service);
795 }
796 
797 void l2cap_unregister_service_internal(void *connection, uint16_t psm){
798     l2cap_service_t *service = l2cap_get_service(psm);
799     if (!service) return;
800     linked_list_remove(&l2cap_services, (linked_item_t *) service);
801     free(service);
802 }
803 
804 //
805 void l2cap_close_connection(void *connection){
806     linked_item_t *it;
807 
808     // close open channels
809     l2cap_channel_t * channel;
810     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
811         channel = (l2cap_channel_t *) it;
812         if (channel->connection == connection) {
813             channel->sig_id = l2cap_next_sig_id();
814             l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->sig_id, channel->remote_cid, channel->local_cid);
815             channel->state = L2CAP_STATE_WAIT_DISCONNECT;
816         }
817     }
818 
819     // unregister services
820     it = (linked_item_t *) &l2cap_services;
821     while (it->next){
822         l2cap_service_t * service = (l2cap_service_t *) it->next;
823         if (service->connection == connection){
824             it->next = it->next->next;
825             free(service);
826         } else {
827             it = it->next;
828         }
829     }
830 }
831