xref: /btstack/src/l2cap.c (revision 56081214e8a275b8daecd57cbbf96c0ec102a979)
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 #include "btstack_memory.h"
45 
46 #include <stdarg.h>
47 #include <string.h>
48 
49 #include <stdio.h>
50 
51 // nr of buffered acl packets in outgoing queue to get max performance
52 #define NR_BUFFERED_ACL_PACKETS 3
53 
54 // used to cache l2cap rejects, echo, and informational requests
55 #define NR_PENDING_SIGNALING_RESPONSES 3
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 // used to cache l2cap rejects, echo, and informational requests
67 static l2cap_signaling_response_t signaling_responses[NR_PENDING_SIGNALING_RESPONSES];
68 static int signaling_responses_pending;
69 
70 static linked_list_t l2cap_channels = NULL;
71 static linked_list_t l2cap_services = NULL;
72 static void (*packet_handler) (void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size) = null_packet_handler;
73 static int new_credits_blocked = 0;
74 
75 // prototypes
76 static void l2cap_finialize_channel_close(l2cap_channel_t *channel);
77 static l2cap_service_t * l2cap_get_service(uint16_t psm);
78 static void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status);
79 static void l2cap_emit_channel_closed(l2cap_channel_t *channel);
80 static void l2cap_emit_connection_request(l2cap_channel_t *channel);
81 static int l2cap_channel_ready_for_open(l2cap_channel_t *channel);
82 
83 
84 void l2cap_init(){
85 
86     new_credits_blocked = 0;
87     signaling_responses_pending = 0;
88 
89     //
90     // register callback with HCI
91     //
92     hci_register_packet_handler(&l2cap_packet_handler);
93 }
94 
95 
96 /** Register L2CAP packet handlers */
97 static void null_packet_handler(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
98 }
99 void l2cap_register_packet_handler(void (*handler)(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size)){
100     packet_handler = handler;
101 }
102 
103 //  notify client/protocol handler
104 void l2cap_dispatch(l2cap_channel_t *channel, uint8_t type, uint8_t * data, uint16_t size){
105     if (channel->packet_handler) {
106         (* (channel->packet_handler))(type, channel->local_cid, data, size);
107     } else {
108         (*packet_handler)(channel->connection, type, channel->local_cid, data, size);
109     }
110 }
111 
112 void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status) {
113     uint8_t event[21];
114     event[0] = L2CAP_EVENT_CHANNEL_OPENED;
115     event[1] = sizeof(event) - 2;
116     event[2] = status;
117     bt_flip_addr(&event[3], channel->address);
118     bt_store_16(event,  9, channel->handle);
119     bt_store_16(event, 11, channel->psm);
120     bt_store_16(event, 13, channel->local_cid);
121     bt_store_16(event, 15, channel->remote_cid);
122     bt_store_16(event, 17, channel->local_mtu);
123     bt_store_16(event, 19, channel->remote_mtu);
124     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
125     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
126 }
127 
128 void l2cap_emit_channel_closed(l2cap_channel_t *channel) {
129     uint8_t event[4];
130     event[0] = L2CAP_EVENT_CHANNEL_CLOSED;
131     event[1] = sizeof(event) - 2;
132     bt_store_16(event, 2, channel->local_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_connection_request(l2cap_channel_t *channel) {
138     uint8_t event[16];
139     event[0] = L2CAP_EVENT_INCOMING_CONNECTION;
140     event[1] = sizeof(event) - 2;
141     bt_flip_addr(&event[2], channel->address);
142     bt_store_16(event,  8, channel->handle);
143     bt_store_16(event, 10, channel->psm);
144     bt_store_16(event, 12, channel->local_cid);
145     bt_store_16(event, 14, channel->remote_cid);
146     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
147     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
148 }
149 
150 void l2cap_emit_credits(l2cap_channel_t *channel, uint8_t credits) {
151     // track credits
152     channel->packets_granted += credits;
153     // log_info("l2cap_emit_credits for cid %u, credits given: %u (+%u)\n", channel->local_cid, channel->packets_granted, credits);
154 
155     uint8_t event[5];
156     event[0] = L2CAP_EVENT_CREDITS;
157     event[1] = sizeof(event) - 2;
158     bt_store_16(event, 2, channel->local_cid);
159     event[4] = credits;
160     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
161     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
162 }
163 
164 void l2cap_block_new_credits(uint8_t blocked){
165     new_credits_blocked = blocked;
166 }
167 
168 void l2cap_hand_out_credits(void){
169 
170     if (new_credits_blocked) return;    // we're told not to. used by daemon
171 
172     linked_item_t *it;
173     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
174         if (!hci_number_free_acl_slots()) return;
175         l2cap_channel_t * channel = (l2cap_channel_t *) it;
176         if (channel->state != L2CAP_STATE_OPEN) continue;
177         if (hci_number_outgoing_packets(channel->handle) < NR_BUFFERED_ACL_PACKETS && channel->packets_granted == 0) {
178             l2cap_emit_credits(channel, 1);
179         }
180     }
181 }
182 
183 l2cap_channel_t * l2cap_get_channel_for_local_cid(uint16_t local_cid){
184     linked_item_t *it;
185     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
186         l2cap_channel_t * channel = (l2cap_channel_t *) it;
187         if ( channel->local_cid == local_cid) {
188             return channel;
189         }
190     }
191     return NULL;
192 }
193 
194 int  l2cap_can_send_packet_now(uint16_t local_cid){
195     l2cap_channel_t *channel = l2cap_get_channel_for_local_cid(local_cid);
196     if (!channel) return 0;
197     if (!channel->packets_granted) return 0;
198     return hci_can_send_packet_now(HCI_ACL_DATA_PACKET);
199 }
200 
201 uint16_t l2cap_get_remote_mtu_for_local_cid(uint16_t local_cid){
202     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
203     if (channel) {
204         return channel->remote_mtu;
205     }
206     return 0;
207 }
208 
209 int l2cap_send_signaling_packet(hci_con_handle_t handle, L2CAP_SIGNALING_COMMANDS cmd, uint8_t identifier, ...){
210 
211     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
212         log_info("l2cap_send_signaling_packet, cannot send\n");
213         return BTSTACK_ACL_BUFFERS_FULL;
214     }
215 
216     // log_info("l2cap_send_signaling_packet type %u\n", cmd);
217     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
218     va_list argptr;
219     va_start(argptr, identifier);
220     uint16_t len = l2cap_create_signaling_internal(acl_buffer, handle, cmd, identifier, argptr);
221     va_end(argptr);
222     // log_info("l2cap_send_signaling_packet con %u!\n", handle);
223     return hci_send_acl_packet(acl_buffer, len);
224 }
225 
226 uint8_t *l2cap_get_outgoing_buffer(void){
227     return hci_get_outgoing_acl_packet_buffer() + COMPLETE_L2CAP_HEADER; // 8 bytes
228 }
229 
230 int l2cap_send_prepared(uint16_t local_cid, uint16_t len){
231 
232     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
233         log_info("l2cap_send_internal cid %u, cannot send\n", local_cid);
234         return BTSTACK_ACL_BUFFERS_FULL;
235     }
236 
237     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
238     if (!channel) {
239         log_error("l2cap_send_internal no channel for cid %u\n", local_cid);
240         return -1;   // TODO: define error
241     }
242 
243     if (channel->packets_granted == 0){
244         log_error("l2cap_send_internal cid %u, no credits!\n", local_cid);
245         return -1;  // TODO: define error
246     }
247 
248     --channel->packets_granted;
249 
250     log_debug("l2cap_send_internal cid %u, handle %u, 1 credit used, credits left %u;\n",
251                   local_cid, channel->handle, channel->packets_granted);
252 
253     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
254 
255     // 0 - Connection handle : PB=10 : BC=00
256     bt_store_16(acl_buffer, 0, channel->handle | (2 << 12) | (0 << 14));
257     // 2 - ACL length
258     bt_store_16(acl_buffer, 2,  len + 4);
259     // 4 - L2CAP packet length
260     bt_store_16(acl_buffer, 4,  len + 0);
261     // 6 - L2CAP channel DEST
262     bt_store_16(acl_buffer, 6, channel->remote_cid);
263     // send
264     int err = hci_send_acl_packet(acl_buffer, len+8);
265 
266     l2cap_hand_out_credits();
267 
268     return err;
269 }
270 
271 int l2cap_send_internal(uint16_t local_cid, uint8_t *data, uint16_t len){
272 
273     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
274         log_info("l2cap_send_internal cid %u, cannot send\n", local_cid);
275         return BTSTACK_ACL_BUFFERS_FULL;
276     }
277 
278     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
279 
280     memcpy(&acl_buffer[8], data, len);
281 
282     return l2cap_send_prepared(local_cid, len);
283 }
284 
285 
286 // MARK: L2CAP_RUN
287 // process outstanding signaling tasks
288 void l2cap_run(void){
289 
290     // check pending signaling responses
291     while (signaling_responses_pending){
292 
293         if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)) break;
294 
295         hci_con_handle_t handle = signaling_responses[0].handle;
296         uint8_t sig_id = signaling_responses[0].sig_id;
297         uint16_t infoType = signaling_responses[0].data;    // INFORMATION_REQUEST
298         uint16_t result   = signaling_responses[0].data;    // CONNECTION_REQUEST
299 
300         switch (signaling_responses[0].code){
301             case CONNECTION_REQUEST:
302                 l2cap_send_signaling_packet(handle, CONNECTION_RESPONSE, sig_id, 0, 0, result, 0);
303                 break;
304             case ECHO_REQUEST:
305                 l2cap_send_signaling_packet(handle, ECHO_RESPONSE, sig_id, 0, NULL);
306                 break;
307             case INFORMATION_REQUEST:
308                 if (infoType == 2) {
309                     uint32_t features = 0;
310                     // extended features request supported, however no features present
311                     l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, 4, &features);
312                 } else {
313                     // all other types are not supported
314                     l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 1, 0, NULL);
315                 }
316                 break;
317             default:
318                 // should not happen
319                 break;
320         }
321 
322         // remove first item
323         signaling_responses_pending--;
324         int i;
325         for (i=0; i < signaling_responses_pending; i++){
326             memcpy(&signaling_responses[i], &signaling_responses[i+1], sizeof(l2cap_signaling_response_t));
327         }
328     }
329 
330     uint8_t  config_options[4];
331     linked_item_t *it;
332     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
333 
334         if (!hci_can_send_packet_now(HCI_COMMAND_DATA_PACKET)) break;
335         if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)) break;
336 
337         l2cap_channel_t * channel = (l2cap_channel_t *) it;
338 
339         // log_info("l2cap_run: state %u, var 0x%02x\n", channel->state, channel->state_var);
340 
341 
342         switch (channel->state){
343 
344             case L2CAP_STATE_WILL_SEND_CREATE_CONNECTION:
345                 // send connection request - set state first
346                 channel->state = L2CAP_STATE_WAIT_CONNECTION_COMPLETE;
347                 // BD_ADDR, Packet_Type, Page_Scan_Repetition_Mode, Reserved, Clock_Offset, Allow_Role_Switch
348                 hci_send_cmd(&hci_create_connection, channel->address, hci_usable_acl_packet_types(), 0, 0, 0, 1);
349                 break;
350 
351             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE:
352                 l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, 0, 0, channel->reason, 0);
353                 // discard channel - l2cap_finialize_channel_close without sending l2cap close event
354                 linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
355                 btstack_memory_l2cap_channel_free(channel);
356                 break;
357 
358             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT:
359                 channel->state = L2CAP_STATE_CONFIG;
360                 channel->state_var |= L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ;
361                 l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid, 0, 0);
362                 break;
363 
364             case L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST:
365                 // success, start l2cap handshake
366                 channel->local_sig_id = l2cap_next_sig_id();
367                 channel->state = L2CAP_STATE_WAIT_CONNECT_RSP;
368                 l2cap_send_signaling_packet( channel->handle, CONNECTION_REQUEST, channel->local_sig_id, channel->psm, channel->local_cid);
369                 break;
370 
371             case L2CAP_STATE_CONFIG:
372                 if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP){
373                     channel->state_var &= ~L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP;
374                     channel->state_var |= L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP;
375                     l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, 0, 0, 0, NULL);
376                 }
377                 else if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ){
378                     channel->state_var &= ~L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ;
379                     channel->state_var |= L2CAP_CHANNEL_STATE_VAR_SENT_CONF_REQ;
380                     channel->local_sig_id = l2cap_next_sig_id();
381                     config_options[0] = 1; // MTU
382                     config_options[1] = 2; // len param
383                     bt_store_16( (uint8_t*)&config_options, 2, channel->local_mtu);
384                     l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->local_sig_id, channel->remote_cid, 0, 4, &config_options);
385                 }
386                 if (l2cap_channel_ready_for_open(channel)){
387                     channel->state = L2CAP_STATE_OPEN;
388                     l2cap_emit_channel_opened(channel, 0);  // success
389                     l2cap_emit_credits(channel, 1);
390                 }
391                 break;
392 
393             case L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE:
394                 l2cap_send_signaling_packet( channel->handle, DISCONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid);
395                 l2cap_finialize_channel_close(channel);
396                 break;
397 
398             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
399                 channel->local_sig_id = l2cap_next_sig_id();
400                 channel->state = L2CAP_STATE_WAIT_DISCONNECT;
401                 l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->local_sig_id, channel->remote_cid, channel->local_cid);
402                 break;
403             default:
404                 break;
405         }
406     }
407 }
408 
409 uint16_t l2cap_max_mtu(void){
410     return hci_max_acl_data_packet_length() - L2CAP_HEADER_SIZE;
411 }
412 
413 // open outgoing L2CAP channel
414 void l2cap_create_channel_internal(void * connection, btstack_packet_handler_t packet_handler,
415                                    bd_addr_t address, uint16_t psm, uint16_t mtu){
416 
417     // alloc structure
418     l2cap_channel_t * chan = btstack_memory_l2cap_channel_get();
419     if (!chan) {
420         // emit error event
421         l2cap_channel_t dummy_channel;
422         BD_ADDR_COPY(dummy_channel.address, address);
423         dummy_channel.psm = psm;
424         l2cap_emit_channel_opened(&dummy_channel, BTSTACK_MEMORY_ALLOC_FAILED);
425         return;
426     }
427     // limit local mtu to max acl packet length
428     if (mtu > l2cap_max_mtu()) {
429         mtu = l2cap_max_mtu();
430     }
431 
432     // fill in
433     BD_ADDR_COPY(chan->address, address);
434     chan->psm = psm;
435     chan->handle = 0;
436     chan->connection = connection;
437     chan->packet_handler = packet_handler;
438     chan->remote_mtu = L2CAP_MINIMAL_MTU;
439     chan->local_mtu = mtu;
440     chan->packets_granted = 0;
441 
442     // set initial state
443     chan->state = L2CAP_STATE_WILL_SEND_CREATE_CONNECTION;
444     chan->state_var = L2CAP_CHANNEL_STATE_VAR_NONE;
445     chan->remote_sig_id = L2CAP_SIG_ID_INVALID;
446     chan->local_sig_id = L2CAP_SIG_ID_INVALID;
447 
448     // add to connections list
449     linked_list_add(&l2cap_channels, (linked_item_t *) chan);
450 
451     l2cap_run();
452 }
453 
454 void l2cap_disconnect_internal(uint16_t local_cid, uint8_t reason){
455     // find channel for local_cid
456     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
457     if (channel) {
458         channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST;
459     }
460     // process
461     l2cap_run();
462 }
463 
464 static void l2cap_handle_connection_failed_for_addr(bd_addr_t address, uint8_t status){
465     linked_item_t *it = (linked_item_t *) &l2cap_channels;
466     while (it->next){
467         l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
468         if ( ! BD_ADDR_CMP( channel->address, address) ){
469             if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
470                 // failure, forward error code
471                 l2cap_emit_channel_opened(channel, status);
472                 // discard channel
473                 it->next = it->next->next;
474                 btstack_memory_l2cap_channel_free(channel);
475             }
476         } else {
477             it = it->next;
478         }
479     }
480 }
481 
482 static void l2cap_handle_connection_success_for_addr(bd_addr_t address, hci_con_handle_t handle){
483     linked_item_t *it;
484     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
485         l2cap_channel_t * channel = (l2cap_channel_t *) it;
486         if ( ! BD_ADDR_CMP( channel->address, address) ){
487             if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
488                 // success, start l2cap handshake
489                 channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST;
490                 channel->handle = handle;
491                 channel->local_cid = l2cap_next_local_cid();
492             }
493         }
494     }
495     // process
496     l2cap_run();
497 }
498 
499 void l2cap_event_handler( uint8_t *packet, uint16_t size ){
500 
501     bd_addr_t address;
502     hci_con_handle_t handle;
503     l2cap_channel_t * channel;
504     linked_item_t *it;
505     int hci_con_used;
506 
507     switch(packet[0]){
508 
509         // handle connection complete events
510         case HCI_EVENT_CONNECTION_COMPLETE:
511             bt_flip_addr(address, &packet[5]);
512             if (packet[2] == 0){
513                 handle = READ_BT_16(packet, 3);
514                 l2cap_handle_connection_success_for_addr(address, handle);
515             } else {
516                 l2cap_handle_connection_failed_for_addr(address, packet[2]);
517             }
518             break;
519 
520         // handle successful create connection cancel command
521         case HCI_EVENT_COMMAND_COMPLETE:
522             if ( COMMAND_COMPLETE_EVENT(packet, hci_create_connection_cancel) ) {
523                 if (packet[5] == 0){
524                     bt_flip_addr(address, &packet[6]);
525                     // CONNECTION TERMINATED BY LOCAL HOST (0X16)
526                     l2cap_handle_connection_failed_for_addr(address, 0x16);
527                 }
528             }
529             l2cap_run();    // try sending signaling packets first
530             break;
531 
532         case HCI_EVENT_COMMAND_STATUS:
533             l2cap_run();    // try sending signaling packets first
534             break;
535 
536         // handle disconnection complete events
537         case HCI_EVENT_DISCONNECTION_COMPLETE:
538             // send l2cap disconnect events for all channels on this handle
539             handle = READ_BT_16(packet, 3);
540             it = (linked_item_t *) &l2cap_channels;
541             while (it->next){
542                 l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
543                 if ( channel->handle == handle ){
544                     // update prev item before free'ing next element - don't call l2cap_finalize_channel_close
545                     it->next = it->next->next;
546                     l2cap_emit_channel_closed(channel);
547                     btstack_memory_l2cap_channel_free(channel);
548                 } else {
549                     it = it->next;
550                 }
551             }
552             break;
553 
554         case HCI_EVENT_NUMBER_OF_COMPLETED_PACKETS:
555             l2cap_run();    // try sending signaling packets first
556             l2cap_hand_out_credits();
557             break;
558 
559         // HCI Connection Timeouts
560         case L2CAP_EVENT_TIMEOUT_CHECK:
561             handle = READ_BT_16(packet, 2);
562             if (hci_authentication_active_for_handle(handle)) break;
563             hci_con_used = 0;
564             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
565                 channel = (l2cap_channel_t *) it;
566                 if (channel->handle == handle) {
567                     hci_con_used = 1;
568                 }
569             }
570             if (hci_con_used) break;
571             if (!hci_can_send_packet_now(HCI_COMMAND_DATA_PACKET)) break;
572             hci_send_cmd(&hci_disconnect, handle, 0x13); // remote closed connection
573             break;
574 
575         case DAEMON_EVENT_HCI_PACKET_SENT:
576             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
577                 channel = (l2cap_channel_t *) it;
578                 if (channel->packet_handler) {
579                     (* (channel->packet_handler))(HCI_EVENT_PACKET, channel->local_cid, packet, size);
580                 }
581             }
582             break;
583 
584         default:
585             break;
586     }
587 
588     // pass on
589     (*packet_handler)(NULL, HCI_EVENT_PACKET, 0, packet, size);
590 }
591 
592 static void l2cap_handle_disconnect_request(l2cap_channel_t *channel, uint16_t identifier){
593     channel->remote_sig_id = identifier;
594     channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE;
595     l2cap_run();
596 }
597 
598 static void l2cap_register_signaling_response(hci_con_handle_t handle, uint8_t code, uint8_t sig_id, uint16_t data){
599     if (signaling_responses_pending < NR_PENDING_SIGNALING_RESPONSES) {
600         signaling_responses[signaling_responses_pending].handle = handle;
601         signaling_responses[signaling_responses_pending].code = code;
602         signaling_responses[signaling_responses_pending].sig_id = sig_id;
603         signaling_responses[signaling_responses_pending].data = data;
604         signaling_responses_pending++;
605         l2cap_run();
606     }
607 }
608 
609 static void l2cap_handle_connection_request(hci_con_handle_t handle, uint8_t sig_id, uint16_t psm, uint16_t source_cid){
610 
611     // log_info("l2cap_handle_connection_request for handle %u, psm %u cid %u\n", handle, psm, source_cid);
612     l2cap_service_t *service = l2cap_get_service(psm);
613     if (!service) {
614         // 0x0002 PSM not supported
615         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0002);
616         return;
617     }
618 
619     hci_connection_t * hci_connection = connection_for_handle( handle );
620     if (!hci_connection) {
621         //
622         log_error("no hci_connection for handle %u\n", handle);
623         return;
624     }
625     // alloc structure
626     // log_info("l2cap_handle_connection_request register channel\n");
627     l2cap_channel_t * channel = btstack_memory_l2cap_channel_get();
628     if (!channel){
629         // 0x0004 No resources available
630         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0004);
631         return;
632     }
633 
634     // fill in
635     BD_ADDR_COPY(channel->address, hci_connection->address);
636     channel->psm = psm;
637     channel->handle = handle;
638     channel->connection = service->connection;
639     channel->packet_handler = service->packet_handler;
640     channel->local_cid  = l2cap_next_local_cid();
641     channel->remote_cid = source_cid;
642     channel->local_mtu  = service->mtu;
643     channel->remote_mtu = L2CAP_DEFAULT_MTU;
644     channel->packets_granted = 0;
645     channel->remote_sig_id = sig_id;
646 
647     // limit local mtu to max acl packet length
648     if (channel->local_mtu > l2cap_max_mtu()) {
649         channel->local_mtu = l2cap_max_mtu();
650     }
651 
652     // set initial state
653     channel->state = L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT;
654     channel->state_var = L2CAP_CHANNEL_STATE_VAR_NONE;
655 
656     // add to connections list
657     linked_list_add(&l2cap_channels, (linked_item_t *) channel);
658 
659     // emit incoming connection request
660     l2cap_emit_connection_request(channel);
661 }
662 
663 void l2cap_accept_connection_internal(uint16_t local_cid){
664     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
665     if (!channel) {
666         log_error("l2cap_accept_connection_internal called but local_cid 0x%x not found", local_cid);
667         return;
668     }
669 
670     channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT;
671 
672     // process
673     l2cap_run();
674 }
675 
676 void l2cap_decline_connection_internal(uint16_t local_cid, uint8_t reason){
677     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid( local_cid);
678     if (!channel) {
679         log_error( "l2cap_decline_connection_internal called but local_cid 0x%x not found", local_cid);
680         return;
681     }
682     channel->state  = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE;
683     channel->reason = reason;
684     l2cap_run();
685 }
686 
687 void l2cap_signaling_handle_configure_request(l2cap_channel_t *channel, uint8_t *command){
688 
689     channel->remote_sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
690 
691     // accept the other's configuration options
692     uint16_t end_pos = 4 + READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
693     uint16_t pos     = 8;
694     while (pos < end_pos){
695         uint8_t type   = command[pos++];
696         uint8_t length = command[pos++];
697         // MTU { type(8): 1, len(8):2, MTU(16) }
698         if ((type & 0x7f) == 1 && length == 2){
699             channel->remote_mtu = READ_BT_16(command, pos);
700             // log_info("l2cap cid %u, remote mtu %u\n", channel->local_cid, channel->remote_mtu);
701         }
702         pos += length;
703     }
704 }
705 
706 static int l2cap_channel_ready_for_open(l2cap_channel_t *channel){
707     // log_info("l2cap_channel_ready_for_open 0x%02x\n", channel->state_var);
708     if ((channel->state_var & L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_RSP) == 0) return 0;
709     if ((channel->state_var & L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP) == 0) return 0;
710     return 1;
711 }
712 
713 
714 void l2cap_signaling_handler_channel(l2cap_channel_t *channel, uint8_t *command){
715 
716     uint8_t  code       = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
717     uint8_t  identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
718     uint16_t result = 0;
719 
720     log_info("signaling handler code %u, state %u\n", code, channel->state);
721 
722     // handle DISCONNECT REQUESTS seperately
723     if (code == DISCONNECTION_REQUEST){
724         switch (channel->state){
725             case L2CAP_STATE_CONFIG:
726             case L2CAP_STATE_OPEN:
727             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
728             case L2CAP_STATE_WAIT_DISCONNECT:
729                 l2cap_handle_disconnect_request(channel, identifier);
730                 break;
731 
732             default:
733                 // ignore in other states
734                 break;
735         }
736         return;
737     }
738 
739     // @STATEMACHINE(l2cap)
740     switch (channel->state) {
741 
742         case L2CAP_STATE_WAIT_CONNECT_RSP:
743             switch (code){
744                 case CONNECTION_RESPONSE:
745                     result = READ_BT_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
746                     switch (result) {
747                         case 0:
748                             // successful connection
749                             channel->remote_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
750                             channel->state = L2CAP_STATE_CONFIG;
751                             channel->state_var |= L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ;
752                             break;
753                         case 1:
754                             // connection pending. get some coffee
755                             break;
756                         default:
757                             // channel closed
758                             channel->state = L2CAP_STATE_CLOSED;
759 
760                             // map l2cap connection response result to BTstack status enumeration
761                             l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result);
762 
763                             // drop link key if security block
764                             if (L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result == L2CAP_CONNECTION_RESPONSE_RESULT_REFUSED_SECURITY){
765                                 hci_drop_link_key_for_bd_addr(&channel->address);
766                             }
767 
768                             // discard channel
769                             linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
770                             btstack_memory_l2cap_channel_free(channel);
771                             break;
772                     }
773                     break;
774 
775                 default:
776                     //@TODO: implement other signaling packets
777                     break;
778             }
779             break;
780 
781         case L2CAP_STATE_CONFIG:
782             switch (code) {
783                 case CONFIGURE_REQUEST:
784                     channel->state_var |= L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_REQ;
785                     channel->state_var |= L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP;
786                     l2cap_signaling_handle_configure_request(channel, command);
787                     break;
788                 case CONFIGURE_RESPONSE:
789                     channel->state_var |= L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_RSP;
790                     break;
791                 default:
792                     break;
793             }
794             if (l2cap_channel_ready_for_open(channel)){
795                 // for open:
796                 channel->state = L2CAP_STATE_OPEN;
797                 l2cap_emit_channel_opened(channel, 0);
798                 l2cap_emit_credits(channel, 1);
799             }
800             break;
801 
802         case L2CAP_STATE_WAIT_DISCONNECT:
803             switch (code) {
804                 case DISCONNECTION_RESPONSE:
805                     l2cap_finialize_channel_close(channel);
806                     break;
807                 default:
808                     //@TODO: implement other signaling packets
809                     break;
810             }
811             break;
812 
813         case L2CAP_STATE_CLOSED:
814             // @TODO handle incoming requests
815             break;
816 
817         case L2CAP_STATE_OPEN:
818             //@TODO: implement other signaling packets, e.g. re-configure
819             break;
820         default:
821             break;
822     }
823     // log_info("new state %u\n", channel->state);
824 }
825 
826 
827 void l2cap_signaling_handler_dispatch( hci_con_handle_t handle, uint8_t * command){
828 
829     // get code, signalind identifier and command len
830     uint8_t code   = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
831     uint8_t sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
832 
833     // not for a particular channel, and not CONNECTION_REQUEST, ECHO_[REQUEST|RESPONSE], INFORMATION_REQUEST
834     if (code < 1 || code == ECHO_RESPONSE || code > INFORMATION_REQUEST){
835         return;
836     }
837 
838     // general commands without an assigned channel
839     switch(code) {
840 
841         case CONNECTION_REQUEST: {
842             uint16_t psm =        READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
843             uint16_t source_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+2);
844             l2cap_handle_connection_request(handle, sig_id, psm, source_cid);
845             return;
846         }
847 
848         case ECHO_REQUEST:
849             l2cap_register_signaling_response(handle, code, sig_id, 0);
850             return;
851 
852         case INFORMATION_REQUEST: {
853             uint16_t infoType = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
854             l2cap_register_signaling_response(handle, code, sig_id, infoType);
855             return;
856         }
857 
858         default:
859             break;
860     }
861 
862 
863     // Get potential destination CID
864     uint16_t dest_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
865 
866     // Find channel for this sig_id and connection handle
867     linked_item_t *it;
868     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
869         l2cap_channel_t * channel = (l2cap_channel_t *) it;
870         if (channel->handle == handle) {
871             if (code & 1) {
872                 // match odd commands (responses) by previous signaling identifier
873                 if (channel->local_sig_id == sig_id) {
874                     l2cap_signaling_handler_channel(channel, command);
875                     break;
876                 }
877             } else {
878                 // match even commands (requests) by local channel id
879                 if (channel->local_cid == dest_cid) {
880                     l2cap_signaling_handler_channel(channel, command);
881                     break;
882                 }
883             }
884         }
885     }
886 }
887 
888 void l2cap_acl_handler( uint8_t *packet, uint16_t size ){
889 
890     // Get Channel ID
891     uint16_t channel_id = READ_L2CAP_CHANNEL_ID(packet);
892 
893     // Signaling Packet?
894     if (channel_id == 1) {
895 
896         // Get Connection
897         hci_con_handle_t handle = READ_ACL_CONNECTION_HANDLE(packet);
898 
899         uint16_t command_offset = 8;
900         while (command_offset < size) {
901 
902             // handle signaling commands
903             l2cap_signaling_handler_dispatch(handle, &packet[command_offset]);
904 
905             // increment command_offset
906             command_offset += L2CAP_SIGNALING_COMMAND_DATA_OFFSET + READ_BT_16(packet, command_offset + L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
907         }
908 
909         l2cap_run();
910 
911         return;
912     }
913 
914     // Find channel for this channel_id and connection handle
915     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(channel_id);
916     if (channel) {
917         l2cap_dispatch(channel, L2CAP_DATA_PACKET, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
918     }
919 }
920 
921 static void l2cap_packet_handler(uint8_t packet_type, uint8_t *packet, uint16_t size){
922     switch (packet_type) {
923         case HCI_EVENT_PACKET:
924             l2cap_event_handler(packet, size);
925             break;
926         case HCI_ACL_DATA_PACKET:
927             l2cap_acl_handler(packet, size);
928             break;
929         default:
930             break;
931     }
932 }
933 
934 // finalize closed channel - l2cap_handle_disconnect_request & DISCONNECTION_RESPONSE
935 void l2cap_finialize_channel_close(l2cap_channel_t *channel){
936     channel->state = L2CAP_STATE_CLOSED;
937     l2cap_emit_channel_closed(channel);
938     // discard channel
939     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
940     btstack_memory_l2cap_channel_free(channel);
941 }
942 
943 l2cap_service_t * l2cap_get_service(uint16_t psm){
944     linked_item_t *it;
945 
946     // close open channels
947     for (it = (linked_item_t *) l2cap_services; it ; it = it->next){
948         l2cap_service_t * service = ((l2cap_service_t *) it);
949         if ( service->psm == psm){
950             return service;
951         };
952     }
953     return NULL;
954 }
955 
956 void l2cap_register_service_internal(void *connection, btstack_packet_handler_t packet_handler, uint16_t psm, uint16_t mtu){
957     // check for alread registered psm
958     // TODO: emit error event
959     l2cap_service_t *service = l2cap_get_service(psm);
960     if (service) {
961         log_error("l2cap_register_service_internal: PSM %u already registered\n", psm);
962         return;
963     }
964 
965     // alloc structure
966     // TODO: emit error event
967     service = btstack_memory_l2cap_service_get();
968     if (!service) {
969         log_error("l2cap_register_service_internal: no memory for l2cap_service_t\n");
970         return;
971     }
972 
973     // fill in
974     service->psm = psm;
975     service->mtu = mtu;
976     service->connection = connection;
977     service->packet_handler = packet_handler;
978 
979     // add to services list
980     linked_list_add(&l2cap_services, (linked_item_t *) service);
981 }
982 
983 void l2cap_unregister_service_internal(void *connection, uint16_t psm){
984     l2cap_service_t *service = l2cap_get_service(psm);
985     if (!service) return;
986     linked_list_remove(&l2cap_services, (linked_item_t *) service);
987     btstack_memory_l2cap_service_free(service);
988 }
989 
990 //
991 void l2cap_close_connection(void *connection){
992     linked_item_t *it;
993 
994     // close open channels - note to myself: no channel is freed, so no new for fancy iterator tricks
995     l2cap_channel_t * channel;
996     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
997         channel = (l2cap_channel_t *) it;
998         if (channel->connection == connection) {
999             channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST;
1000         }
1001     }
1002 
1003     // unregister services
1004     it = (linked_item_t *) &l2cap_services;
1005     while (it->next) {
1006         l2cap_service_t * service = (l2cap_service_t *) it->next;
1007         if (service->connection == connection){
1008             it->next = it->next->next;
1009             btstack_memory_l2cap_service_free(service);
1010         } else {
1011             it = it->next;
1012         }
1013     }
1014 
1015     // process
1016     l2cap_run();
1017 }
1018