xref: /btstack/src/l2cap.c (revision 6218e6f12b65360502381e49940a9ac8941192a4)
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     // first check if we should hand out credits
139 
140     if (!hci_number_free_acl_slots() || hci_number_outgoing_packets(channel->handle) >= 2){
141         return; // not yet
142     }
143     // track credits
144     channel->packets_granted += credits;
145     log_dbg("l2cap_emit_credits for cid %u, credits now: %u (+%u)\n", channel->local_cid, channel->packets_granted, credits);
146 
147     uint8_t event[5];
148     event[0] = L2CAP_EVENT_CREDITS;
149     event[1] = sizeof(event) - 2;
150     bt_store_16(event, 2, channel->local_cid);
151     event[4] = credits;
152     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
153     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
154 }
155 
156 l2cap_channel_t * l2cap_get_channel_for_local_cid(uint16_t local_cid){
157     linked_item_t *it;
158     l2cap_channel_t * channel;
159     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
160         channel = (l2cap_channel_t *) it;
161         if ( channel->local_cid == local_cid) {
162             return channel;
163         }
164     }
165     return NULL;
166 }
167 
168 uint16_t l2cap_get_remote_mtu_for_local_cid(uint16_t local_cid){
169     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
170     if (channel) {
171         return channel->remote_mtu;
172     }
173     return 0;
174 }
175 
176 int l2cap_send_signaling_packet(hci_con_handle_t handle, L2CAP_SIGNALING_COMMANDS cmd, uint8_t identifier, ...){
177     // printf("l2cap_send_signaling_packet type %u\n", cmd);
178     va_list argptr;
179     va_start(argptr, identifier);
180     uint16_t len = l2cap_create_signaling_internal(sig_buffer, handle, cmd, identifier, argptr);
181     va_end(argptr);
182     return hci_send_acl_packet(sig_buffer, len);
183 }
184 
185 int l2cap_send_internal(uint16_t local_cid, uint8_t *data, uint16_t len){
186 
187     // check for free places on BT module
188     if (!hci_number_free_acl_slots()) return -1;
189 
190     int err = 0;
191 
192     // find channel for local_cid, construct l2cap packet and send
193     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
194     if (channel) {
195         // track sending
196         ++channel->packets_outgoing;
197         if (channel->packets_granted > 0){
198             --channel->packets_granted;
199         } else {
200             log_err("l2cap_send_internal cid %u, no credits!\n", local_cid);
201         }
202         log_dbg("l2cap_send_internal cid %u, 1 credit used, credits left %u; outgoing count %u\n",
203                 local_cid, channel->packets_granted, channel->packets_outgoing);
204 
205         // 0 - Connection handle : PB=10 : BC=00
206         bt_store_16(acl_buffer, 0, channel->handle | (2 << 12) | (0 << 14));
207         // 2 - ACL length
208         bt_store_16(acl_buffer, 2,  len + 4);
209         // 4 - L2CAP packet length
210         bt_store_16(acl_buffer, 4,  len + 0);
211         // 6 - L2CAP channel DEST
212         bt_store_16(acl_buffer, 6, channel->remote_cid);
213         // 8 - data
214         memcpy(&acl_buffer[8], data, len);
215 
216         // send
217         err = hci_send_acl_packet(acl_buffer, len+8);
218     }
219     return err;
220 }
221 
222 // open outgoing L2CAP channel
223 void l2cap_create_channel_internal(void * connection, btstack_packet_handler_t packet_handler, bd_addr_t address, uint16_t psm){
224 
225     // alloc structure
226     l2cap_channel_t * chan = malloc(sizeof(l2cap_channel_t));
227     // TODO: emit error event
228     if (!chan) return;
229 
230     // fill in
231     BD_ADDR_COPY(chan->address, address);
232     chan->psm = psm;
233     chan->handle = 0;
234     chan->connection = connection;
235     chan->packet_handler = packet_handler;
236     chan->remote_mtu = L2CAP_MINIMAL_MTU;
237 
238     // flow control
239     chan->packets_granted = 0;
240     chan->packets_outgoing = 0;
241 
242     // set initial state
243     chan->state = L2CAP_STATE_CLOSED;
244     chan->sig_id = L2CAP_SIG_ID_INVALID;
245 
246     // add to connections list
247     linked_list_add(&l2cap_channels, (linked_item_t *) chan);
248 
249     // send connection request
250     // BD_ADDR, Packet_Type, Page_Scan_Repetition_Mode, Reserved, Clock_Offset, Allow_Role_Switch
251     hci_send_cmd(&hci_create_connection, address, 0x18, 0, 0, 0, 0);
252 }
253 
254 void l2cap_disconnect_internal(uint16_t local_cid, uint8_t reason){
255     // find channel for local_cid
256     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
257     if (channel) {
258         channel->sig_id = l2cap_next_sig_id();
259         l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->sig_id, channel->remote_cid, channel->local_cid);
260         channel->state = L2CAP_STATE_WAIT_DISCONNECT;
261     }
262 }
263 
264 static void l2cap_handle_connection_failed_for_addr(bd_addr_t address, uint8_t status){
265     linked_item_t *it;
266     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
267         l2cap_channel_t * channel = (l2cap_channel_t *) it;
268         if ( ! BD_ADDR_CMP( channel->address, address) ){
269             if (channel->state == L2CAP_STATE_CLOSED) {
270                 // failure, forward error code
271                 l2cap_emit_channel_opened(channel, status);
272                 // discard channel
273                 linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
274                 free (channel);
275             }
276         }
277     }
278 }
279 
280 static void l2cap_handle_connection_success_for_addr(bd_addr_t address, hci_con_handle_t handle){
281     linked_item_t *it;
282     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
283         l2cap_channel_t * channel = (l2cap_channel_t *) it;
284         if ( ! BD_ADDR_CMP( channel->address, address) ){
285             if (channel->state == L2CAP_STATE_CLOSED) {
286                 // success, start l2cap handshake
287                 channel->handle = handle;
288                 channel->sig_id = l2cap_next_sig_id();
289                 channel->local_cid = l2cap_next_local_cid();
290                 channel->state = L2CAP_STATE_WAIT_CONNECT_RSP;
291                 l2cap_send_signaling_packet( channel->handle, CONNECTION_REQUEST, channel->sig_id, channel->psm, channel->local_cid);
292             }
293         }
294     }
295 }
296 
297 void l2cap_event_handler( uint8_t *packet, uint16_t size ){
298 
299     bd_addr_t address;
300     hci_con_handle_t handle;
301     linked_item_t *it;
302     int i;
303 
304     switch(packet[0]){
305 
306         // handle connection complete events
307         case HCI_EVENT_CONNECTION_COMPLETE:
308             bt_flip_addr(address, &packet[5]);
309             if (packet[2] == 0){
310                 handle = READ_BT_16(packet, 3);
311                 l2cap_handle_connection_success_for_addr(address, handle);
312             } else {
313                 l2cap_handle_connection_failed_for_addr(address, packet[2]);
314             }
315             break;
316 
317         // handle successful create connection cancel command
318         case HCI_EVENT_COMMAND_COMPLETE:
319             if ( COMMAND_COMPLETE_EVENT(packet, hci_create_connection_cancel) ) {
320                 if (packet[5] == 0){
321                     bt_flip_addr(address, &packet[6]);
322                     // CONNECTION TERMINATED BY LOCAL HOST (0X16)
323                     l2cap_handle_connection_failed_for_addr(address, 0x16);
324                 }
325             }
326             break;
327 
328         // handle disconnection complete events
329         case HCI_EVENT_DISCONNECTION_COMPLETE:
330             // send l2cap disconnect events for all channels on this handle
331             handle = READ_BT_16(packet, 3);
332             // only access next element to allows for removal
333             for (it = (linked_item_t *) &l2cap_channels; it->next ; it = it->next){
334                 l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
335                 if ( channel->handle == handle ){
336                     // update prev item before free'ing next element
337                     it->next = it->next->next;
338                     l2cap_finialize_channel_close(channel);
339                 }
340             }
341             break;
342 
343         case HCI_EVENT_NUMBER_OF_COMPLETED_PACKETS:
344             for (i=0; i<packet[2];i++){
345                 handle = READ_BT_16(packet, 3 + 2*i);
346                 uint16_t num_packets = READ_BT_16(packet, 3 + packet[2]*2 + 2*i);
347                 while (num_packets) {
348                     num_packets--;
349                     // pick some slot
350                     l2cap_channel_t * oldest_channel = NULL;
351                     for (it = (linked_item_t *) &l2cap_channels; it->next ; it = it->next){
352                         l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
353                         if (channel->packets_outgoing){
354                             oldest_channel   = channel;
355                         }
356                     }
357                     // decrease packets and grant new credits
358                     if (oldest_channel) {
359                         oldest_channel->packets_outgoing--;
360 
361                         log_dbg("hci_number_completed_packet (l2cap) for cid %u, outgoing count %u\n",
362                                 oldest_channel->local_cid, oldest_channel->packets_outgoing);
363 
364                     } else {
365                         log_err("hci_number_completed_packet but no outgoing packet in records\n");
366                     }
367                 }
368             }
369             break;
370 
371         // HCI Connection Timeouts
372         case L2CAP_EVENT_TIMEOUT_CHECK:
373             handle = READ_BT_16(packet, 2);
374             l2cap_channel_t * channel;
375             int used = 0;
376             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
377                 channel = (l2cap_channel_t *) it;
378                 if (channel->handle == handle) {
379                     used = 1;
380                 }
381             }
382             if (!used) {
383                 hci_send_cmd(&hci_disconnect, handle, 0x13); // remote closed connection
384             }
385             break;
386 
387         default:
388             break;
389     }
390 
391     // pass on
392     (*packet_handler)(NULL, HCI_EVENT_PACKET, 0, packet, size);
393 }
394 
395 static void l2cap_handle_disconnect_request(l2cap_channel_t *channel, uint16_t identifier){
396     l2cap_send_signaling_packet( channel->handle, DISCONNECTION_RESPONSE, identifier, channel->local_cid, channel->remote_cid);
397     l2cap_finialize_channel_close(channel);
398 }
399 
400 static void l2cap_handle_connection_request(hci_con_handle_t handle, uint8_t sig_id, uint16_t psm, uint16_t source_cid){
401 
402     // printf("l2cap_handle_connection_request for handle %u, psm %u cid %u\n", handle, psm, source_cid);
403     l2cap_service_t *service = l2cap_get_service(psm);
404     if (!service) {
405         // 0x0002 PSM not supported
406         // printf("l2cap_handle_connection_request no PSM for psm %u/n", psm);
407         l2cap_send_signaling_packet(handle, CONNECTION_RESPONSE, sig_id, 0, 0, 0x0002, 0);
408         return;
409     }
410 
411     hci_connection_t * hci_connection = connection_for_handle( handle );
412     if (!hci_connection) {
413         fprintf(stderr, "no hci_connection for handle %u\n", handle);
414         // TODO: emit error
415         return;
416     }
417     // alloc structure
418     // printf("l2cap_handle_connection_request register channel\n");
419     l2cap_channel_t * channel = malloc(sizeof(l2cap_channel_t));
420     // TODO: emit error event
421     if (!channel) return;
422 
423     // fill in
424     BD_ADDR_COPY(channel->address, hci_connection->address);
425     channel->psm = psm;
426     channel->handle = handle;
427     channel->connection = service->connection;
428     channel->packet_handler = service->packet_handler;
429     channel->local_cid  = l2cap_next_local_cid();
430     channel->remote_cid = source_cid;
431     channel->remote_mtu = L2CAP_MINIMAL_MTU;
432 
433     // set initial state
434     channel->state = L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT;
435 
436     // temp. store req sig id
437     channel->sig_id = sig_id;
438 
439     // add to connections list
440     linked_list_add(&l2cap_channels, (linked_item_t *) channel);
441 
442     // emit incoming connection request
443     l2cap_emit_connection_request(channel);
444 }
445 
446 void l2cap_accept_connection_internal(uint16_t local_cid){
447     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
448     if (!channel) {
449         fprintf(stderr, "l2cap_accept_connection_internal called but local_cid 0x%x not found", local_cid);
450         return;
451     }
452 
453     // accept connection
454     l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->sig_id, channel->local_cid, channel->remote_cid, 0, 0);
455 
456     // set real sig and state and start config
457     channel->sig_id = l2cap_next_sig_id();
458     channel->state  = L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ;
459     l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->sig_id, channel->remote_cid, 0, 4, &config_options);
460 
461     // printf("new state %u\n", channel->state);
462 }
463 
464 void l2cap_decline_connection_internal(uint16_t local_cid, uint8_t reason){
465     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid( local_cid);
466     if (!channel) {
467         fprintf(stderr, "l2cap_decline_connection_internal called but local_cid 0x%x not found", local_cid);
468         return;
469     }
470     l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->sig_id, 0, 0, reason, 0);
471 
472     // discard channel
473     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
474     free (channel);
475 }
476 
477 void l2cap_signaling_handle_configure_request(l2cap_channel_t *channel, uint8_t *command){
478     // accept the other's configuration options
479     uint16_t end_pos = 4 + READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
480     uint16_t pos     = 8;
481     while (pos < end_pos){
482         uint8_t type   = command[pos++];
483         uint8_t length = command[pos++];
484         // MTU { type(8): 1, len(8):2, MTU(16) }
485         if ((type & 0x7f) == 1 && length == 2){
486             channel->remote_mtu = READ_BT_16(command, pos);
487             // printf("l2cap cid %u, remote mtu %u\n", channel->local_cid, channel->remote_mtu);
488         }
489         pos += length;
490     }
491     uint8_t identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
492     // send back received options
493     // l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, identifier, channel->remote_cid, 0, 0, len-4, &command[8]);
494     // send back OK
495     l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, identifier, channel->remote_cid, 0, 0, 0, NULL);
496 }
497 
498 void l2cap_signaling_handler_channel(l2cap_channel_t *channel, uint8_t *command){
499 
500     uint8_t code       = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
501     uint8_t identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
502     uint16_t result = 0;
503 
504     // printf("signaling handler code %u\n", code);
505 
506     switch (channel->state) {
507 
508         case L2CAP_STATE_WAIT_CONNECT_RSP:
509             switch (code){
510                 case CONNECTION_RESPONSE:
511                     result = READ_BT_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
512                     switch (result) {
513                         case 0:
514                             // successful connection
515                             channel->remote_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
516                             channel->sig_id = l2cap_next_sig_id();
517                             l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->sig_id, channel->remote_cid, 0, 4, &config_options);
518                             channel->state = L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ;
519                             break;
520                         case 1:
521                             // connection pending. get some coffee
522                             break;
523                         default:
524                             // map l2cap connection response result to BTstack status enumeration
525                             l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result);
526                             break;
527                     }
528                     break;
529 
530                 case DISCONNECTION_REQUEST:
531                     l2cap_handle_disconnect_request(channel, identifier);
532                     break;
533 
534                 default:
535                     //@TODO: implement other signaling packets
536                     break;
537             }
538             break;
539 
540         case L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ:
541             switch (code) {
542                 case CONFIGURE_RESPONSE:
543                     channel->state = L2CAP_STATE_WAIT_CONFIG_REQ;
544                     break;
545                 case CONFIGURE_REQUEST:
546                     l2cap_signaling_handle_configure_request(channel, command);
547                     channel->state = L2CAP_STATE_WAIT_CONFIG_REQ_RSP;
548                     break;
549                 case DISCONNECTION_REQUEST:
550                     l2cap_handle_disconnect_request(channel, identifier);
551                     break;
552                 default:
553                     //@TODO: implement other signaling packets
554                     break;
555             }
556             break;
557 
558         case L2CAP_STATE_WAIT_CONFIG_REQ:
559             switch (code) {
560                 case CONFIGURE_REQUEST:
561                     l2cap_signaling_handle_configure_request(channel, command);
562                     channel->state = L2CAP_STATE_OPEN;
563                     l2cap_emit_channel_opened(channel, 0);  // success
564                     l2cap_emit_credits(channel, 1);
565                     break;
566                 case DISCONNECTION_REQUEST:
567                     l2cap_handle_disconnect_request(channel, identifier);
568                     break;
569                 default:
570                     //@TODO: implement other signaling packets
571                     break;
572             }
573             break;
574 
575         case L2CAP_STATE_WAIT_CONFIG_REQ_RSP:
576             switch (code) {
577                 case CONFIGURE_RESPONSE:
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_DISCONNECT:
592             switch (code) {
593                 case DISCONNECTION_RESPONSE:
594                     l2cap_finialize_channel_close(channel);
595                     break;
596                 case DISCONNECTION_REQUEST:
597                     l2cap_handle_disconnect_request(channel, identifier);
598                     break;
599                 default:
600                     //@TODO: implement other signaling packets
601                     break;
602             }
603             break;
604 
605         case L2CAP_STATE_CLOSED:
606             // @TODO handle incoming requests
607             break;
608 
609         case L2CAP_STATE_OPEN:
610             switch (code) {
611                 case DISCONNECTION_REQUEST:
612                     l2cap_handle_disconnect_request(channel, identifier);
613                     break;
614                 default:
615                     //@TODO: implement other signaling packets, e.g. re-configure
616                     break;
617             }
618             break;
619         default:
620             break;
621     }
622     // printf("new state %u\n", channel->state);
623 }
624 
625 
626 void l2cap_signaling_handler_dispatch( hci_con_handle_t handle, uint8_t * command){
627 
628     // get code, signalind identifier and command len
629     uint8_t code   = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
630     uint8_t sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
631     uint16_t len   = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
632 
633     // not for a particular channel, and not CONNECTION_REQUEST, ECHO_[REQUEST|RESPONSE], INFORMATION_REQUEST
634     if (code < 1 || code == ECHO_RESPONSE || code > INFORMATION_REQUEST){
635         return;
636     }
637 
638     // general commands without an assigned channel
639     switch(code) {
640 
641         case CONNECTION_REQUEST: {
642             uint16_t psm =        READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
643             uint16_t source_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+2);
644             l2cap_handle_connection_request(handle, sig_id, psm, source_cid);
645             break;
646         }
647 
648         case ECHO_REQUEST: {
649             // send back packet
650             l2cap_send_signaling_packet(handle, ECHO_RESPONSE, sig_id, len, &command[L2CAP_SIGNALING_COMMAND_DATA_OFFSET]);
651             break;
652         }
653 
654         case INFORMATION_REQUEST: {
655             // we neither support connectionless L2CAP data nor support any flow control modes yet
656             uint16_t infoType = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
657             if (infoType == 2) {
658                 uint32_t features = 0;
659                 // extended features request supported, however no features present
660                 l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, 4, &features);
661             } else {
662                 // all other types are not supported
663                 l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 1, 0, NULL);
664             }
665             break;;
666         }
667 
668         default:
669             break;
670     }
671 
672 
673     // Get potential destination CID
674     uint16_t dest_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
675 
676     // Find channel for this sig_id and connection handle
677     linked_item_t *it;
678     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
679         l2cap_channel_t * channel = (l2cap_channel_t *) it;
680         if (channel->handle == handle) {
681             if (code & 1) {
682                 // match odd commands by previous signaling identifier
683                 if (channel->sig_id == sig_id) {
684                     l2cap_signaling_handler_channel(channel, command);
685                 }
686             } else {
687                 // match even commands by local channel id
688                 if (channel->local_cid == dest_cid) {
689                     l2cap_signaling_handler_channel(channel, command);
690                 }
691             }
692         }
693     }
694 }
695 
696 void l2cap_acl_handler( uint8_t *packet, uint16_t size ){
697 
698     // Get Channel ID
699     uint16_t channel_id = READ_L2CAP_CHANNEL_ID(packet);
700 
701     // Signaling Packet?
702     if (channel_id == 1) {
703 
704         // Get Connection
705         hci_con_handle_t handle = READ_ACL_CONNECTION_HANDLE(packet);
706 
707         uint16_t command_offset = 8;
708         while (command_offset < size) {
709 
710             // handle signaling commands
711             l2cap_signaling_handler_dispatch(handle, &packet[command_offset]);
712 
713             // increment command_offset
714             command_offset += L2CAP_SIGNALING_COMMAND_DATA_OFFSET + READ_BT_16(packet, command_offset + L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
715         }
716         return;
717     }
718 
719     // Find channel for this channel_id and connection handle
720     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(channel_id);
721     if (channel) {
722         l2cap_dispatch(channel, L2CAP_DATA_PACKET, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
723     }
724 }
725 
726 static void l2cap_packet_handler(uint8_t packet_type, uint8_t *packet, uint16_t size){
727     switch (packet_type) {
728         case HCI_EVENT_PACKET:
729             l2cap_event_handler(packet, size);
730             break;
731         case HCI_ACL_DATA_PACKET:
732             l2cap_acl_handler(packet, size);
733             break;
734         default:
735             break;
736     }
737 }
738 
739 // finalize closed channel
740 void l2cap_finialize_channel_close(l2cap_channel_t *channel){
741     channel->state = L2CAP_STATE_CLOSED;
742     l2cap_emit_channel_closed(channel);
743 
744     // discard channel
745     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
746     free (channel);
747 }
748 
749 l2cap_service_t * l2cap_get_service(uint16_t psm){
750     linked_item_t *it;
751 
752     // close open channels
753     for (it = (linked_item_t *) l2cap_services; it ; it = it->next){
754         l2cap_service_t * service = ((l2cap_service_t *) it);
755         if ( service->psm == psm){
756             return service;
757         };
758     }
759     return NULL;
760 }
761 
762 void l2cap_register_service_internal(void *connection, btstack_packet_handler_t packet_handler, uint16_t psm, uint16_t mtu){
763     // check for alread registered psm // TODO: emit error event
764     l2cap_service_t *service = l2cap_get_service(psm);
765     if (service) return;
766 
767     // alloc structure     // TODO: emit error event
768     service = malloc(sizeof(l2cap_service_t));
769     if (!service) return;
770 
771     // fill in
772     service->psm = psm;
773     service->mtu = mtu;
774     service->connection = connection;
775     service->packet_handler = packet_handler;
776 
777     // add to services list
778     linked_list_add(&l2cap_services, (linked_item_t *) service);
779 }
780 
781 void l2cap_unregister_service_internal(void *connection, uint16_t psm){
782     l2cap_service_t *service = l2cap_get_service(psm);
783     if (!service) return;
784     linked_list_remove(&l2cap_services, (linked_item_t *) service);
785     free(service);
786 }
787 
788 //
789 void l2cap_close_connection(void *connection){
790     linked_item_t *it;
791 
792     // close open channels
793     l2cap_channel_t * channel;
794     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
795         channel = (l2cap_channel_t *) it;
796         if (channel->connection == connection) {
797             channel->sig_id = l2cap_next_sig_id();
798             l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->sig_id, channel->remote_cid, channel->local_cid);
799             channel->state = L2CAP_STATE_WAIT_DISCONNECT;
800         }
801     }
802 
803     // unregister services
804     it = (linked_item_t *) &l2cap_services;
805     while (it->next){
806         l2cap_service_t * service = (l2cap_service_t *) it->next;
807         if (service->connection == connection){
808             it->next = it->next->next;
809             free(service);
810         } else {
811             it = it->next;
812         }
813     }
814 }
815