xref: /btstack/src/l2cap.c (revision 6b64433e6a17b046d431031fa3995f31c29aa188)
1 /*
2  * Copyright (C) 2009-2012 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  * 4. Any redistribution, use, or modification is done solely for
17  *    personal benefit and not for any commercial purpose or for
18  *    monetary gain.
19  *
20  * THIS SOFTWARE IS PROVIDED BY MATTHIAS RINGWALD AND CONTRIBUTORS
21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
24  * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
26  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
27  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
30  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  *
33  * Please inquire about commercial licensing options at [email protected]
34  *
35  */
36 
37 /*
38  *  l2cap.c
39  *
40  *  Logical Link Control and Adaption Protocl (L2CAP)
41  *
42  *  Created by Matthias Ringwald on 5/16/09.
43  */
44 
45 #include "l2cap.h"
46 #include "hci.h"
47 #include "hci_dump.h"
48 #include "debug.h"
49 #include "btstack_memory.h"
50 
51 #include <stdarg.h>
52 #include <string.h>
53 
54 #include <stdio.h>
55 
56 // nr of buffered acl packets in outgoing queue to get max performance
57 #define NR_BUFFERED_ACL_PACKETS 3
58 
59 // used to cache l2cap rejects, echo, and informational requests
60 #define NR_PENDING_SIGNALING_RESPONSES 3
61 
62 // offsets for L2CAP SIGNALING COMMANDS
63 #define L2CAP_SIGNALING_COMMAND_CODE_OFFSET   0
64 #define L2CAP_SIGNALING_COMMAND_SIGID_OFFSET  1
65 #define L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET 2
66 #define L2CAP_SIGNALING_COMMAND_DATA_OFFSET   4
67 
68 static void null_packet_handler(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size);
69 static void l2cap_packet_handler(uint8_t packet_type, uint8_t *packet, uint16_t size);
70 
71 // used to cache l2cap rejects, echo, and informational requests
72 static l2cap_signaling_response_t signaling_responses[NR_PENDING_SIGNALING_RESPONSES];
73 static int signaling_responses_pending;
74 
75 static linked_list_t l2cap_channels = NULL;
76 static linked_list_t l2cap_services = NULL;
77 static void (*packet_handler) (void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size) = null_packet_handler;
78 static int new_credits_blocked = 0;
79 
80 static btstack_packet_handler_t attribute_protocol_packet_handler = NULL;
81 static btstack_packet_handler_t security_protocol_packet_handler = NULL;
82 
83 // prototypes
84 static void l2cap_finialize_channel_close(l2cap_channel_t *channel);
85 static l2cap_service_t * l2cap_get_service(uint16_t psm);
86 static void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status);
87 static void l2cap_emit_channel_closed(l2cap_channel_t *channel);
88 static void l2cap_emit_connection_request(l2cap_channel_t *channel);
89 static int l2cap_channel_ready_for_open(l2cap_channel_t *channel);
90 
91 
92 void l2cap_init(){
93     new_credits_blocked = 0;
94     signaling_responses_pending = 0;
95 
96     l2cap_channels = NULL;
97     l2cap_services = NULL;
98 
99     packet_handler = null_packet_handler;
100 
101     //
102     // register callback with HCI
103     //
104     hci_register_packet_handler(&l2cap_packet_handler);
105     hci_connectable_control(0); // no services yet
106 }
107 
108 
109 /** Register L2CAP packet handlers */
110 static void null_packet_handler(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
111 }
112 void l2cap_register_packet_handler(void (*handler)(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size)){
113     packet_handler = handler;
114 }
115 
116 //  notify client/protocol handler
117 void l2cap_dispatch(l2cap_channel_t *channel, uint8_t type, uint8_t * data, uint16_t size){
118     if (channel->packet_handler) {
119         (* (channel->packet_handler))(type, channel->local_cid, data, size);
120     } else {
121         (*packet_handler)(channel->connection, type, channel->local_cid, data, size);
122     }
123 }
124 
125 void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status) {
126     uint8_t event[21];
127     event[0] = L2CAP_EVENT_CHANNEL_OPENED;
128     event[1] = sizeof(event) - 2;
129     event[2] = status;
130     bt_flip_addr(&event[3], channel->address);
131     bt_store_16(event,  9, channel->handle);
132     bt_store_16(event, 11, channel->psm);
133     bt_store_16(event, 13, channel->local_cid);
134     bt_store_16(event, 15, channel->remote_cid);
135     bt_store_16(event, 17, channel->local_mtu);
136     bt_store_16(event, 19, channel->remote_mtu);
137     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
138     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
139 }
140 
141 void l2cap_emit_channel_closed(l2cap_channel_t *channel) {
142     uint8_t event[4];
143     event[0] = L2CAP_EVENT_CHANNEL_CLOSED;
144     event[1] = sizeof(event) - 2;
145     bt_store_16(event, 2, channel->local_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_connection_request(l2cap_channel_t *channel) {
151     uint8_t event[16];
152     event[0] = L2CAP_EVENT_INCOMING_CONNECTION;
153     event[1] = sizeof(event) - 2;
154     bt_flip_addr(&event[2], channel->address);
155     bt_store_16(event,  8, channel->handle);
156     bt_store_16(event, 10, channel->psm);
157     bt_store_16(event, 12, channel->local_cid);
158     bt_store_16(event, 14, channel->remote_cid);
159     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
160     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
161 }
162 
163 static void l2cap_emit_service_registered(void *connection, uint8_t status, uint16_t psm){
164     uint8_t event[5];
165     event[0] = L2CAP_EVENT_SERVICE_REGISTERED;
166     event[1] = sizeof(event) - 2;
167     event[2] = status;
168     bt_store_16(event, 3, psm);
169     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
170     (*packet_handler)(connection, HCI_EVENT_PACKET, 0, event, sizeof(event));
171 }
172 
173 void l2cap_emit_credits(l2cap_channel_t *channel, uint8_t credits) {
174     // track credits
175     channel->packets_granted += credits;
176     // log_info("l2cap_emit_credits for cid %u, credits given: %u (+%u)\n", channel->local_cid, channel->packets_granted, credits);
177 
178     uint8_t event[5];
179     event[0] = L2CAP_EVENT_CREDITS;
180     event[1] = sizeof(event) - 2;
181     bt_store_16(event, 2, channel->local_cid);
182     event[4] = credits;
183     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
184     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
185 }
186 
187 void l2cap_block_new_credits(uint8_t blocked){
188     new_credits_blocked = blocked;
189 }
190 
191 void l2cap_hand_out_credits(void){
192 
193     if (new_credits_blocked) return;    // we're told not to. used by daemon
194 
195     linked_item_t *it;
196     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
197         if (!hci_number_free_acl_slots()) return;
198         l2cap_channel_t * channel = (l2cap_channel_t *) it;
199         if (channel->state != L2CAP_STATE_OPEN) continue;
200         if (hci_number_outgoing_packets(channel->handle) < NR_BUFFERED_ACL_PACKETS && channel->packets_granted == 0) {
201             l2cap_emit_credits(channel, 1);
202         }
203     }
204 }
205 
206 l2cap_channel_t * l2cap_get_channel_for_local_cid(uint16_t local_cid){
207     linked_item_t *it;
208     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
209         l2cap_channel_t * channel = (l2cap_channel_t *) it;
210         if ( channel->local_cid == local_cid) {
211             return channel;
212         }
213     }
214     return NULL;
215 }
216 
217 int  l2cap_can_send_packet_now(uint16_t local_cid){
218     l2cap_channel_t *channel = l2cap_get_channel_for_local_cid(local_cid);
219     if (!channel) return 0;
220     if (!channel->packets_granted) return 0;
221     return hci_can_send_packet_now(HCI_ACL_DATA_PACKET);
222 }
223 
224 uint16_t l2cap_get_remote_mtu_for_local_cid(uint16_t local_cid){
225     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
226     if (channel) {
227         return channel->remote_mtu;
228     }
229     return 0;
230 }
231 
232 int l2cap_send_signaling_packet(hci_con_handle_t handle, L2CAP_SIGNALING_COMMANDS cmd, uint8_t identifier, ...){
233 
234     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
235         log_info("l2cap_send_signaling_packet, cannot send\n");
236         return BTSTACK_ACL_BUFFERS_FULL;
237     }
238 
239     // log_info("l2cap_send_signaling_packet type %u\n", cmd);
240     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
241     va_list argptr;
242     va_start(argptr, identifier);
243     uint16_t len = l2cap_create_signaling_internal(acl_buffer, handle, cmd, identifier, argptr);
244     va_end(argptr);
245     // log_info("l2cap_send_signaling_packet con %u!\n", handle);
246     return hci_send_acl_packet(acl_buffer, len);
247 }
248 
249 uint8_t *l2cap_get_outgoing_buffer(void){
250     return hci_get_outgoing_acl_packet_buffer() + COMPLETE_L2CAP_HEADER; // 8 bytes
251 }
252 
253 int l2cap_send_prepared(uint16_t local_cid, uint16_t len){
254 
255     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
256         log_info("l2cap_send_internal cid %u, cannot send\n", local_cid);
257         return BTSTACK_ACL_BUFFERS_FULL;
258     }
259 
260     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
261     if (!channel) {
262         log_error("l2cap_send_internal no channel for cid %u\n", local_cid);
263         return -1;   // TODO: define error
264     }
265 
266     if (channel->packets_granted == 0){
267         log_error("l2cap_send_internal cid %u, no credits!\n", local_cid);
268         return -1;  // TODO: define error
269     }
270 
271     --channel->packets_granted;
272 
273     log_debug("l2cap_send_internal cid %u, handle %u, 1 credit used, credits left %u;\n",
274                   local_cid, channel->handle, channel->packets_granted);
275 
276     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
277 
278     // 0 - Connection handle : PB=10 : BC=00
279     bt_store_16(acl_buffer, 0, channel->handle | (2 << 12) | (0 << 14));
280     // 2 - ACL length
281     bt_store_16(acl_buffer, 2,  len + 4);
282     // 4 - L2CAP packet length
283     bt_store_16(acl_buffer, 4,  len + 0);
284     // 6 - L2CAP channel DEST
285     bt_store_16(acl_buffer, 6, channel->remote_cid);
286     // send
287     int err = hci_send_acl_packet(acl_buffer, len+8);
288 
289     l2cap_hand_out_credits();
290 
291     return err;
292 }
293 
294 int l2cap_send_prepared_connectionless(uint16_t handle, uint16_t cid, uint16_t len){
295 
296     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
297         log_info("l2cap_send_prepared_to_handle cid %u, cannot send\n", cid);
298         return BTSTACK_ACL_BUFFERS_FULL;
299     }
300 
301     log_debug("l2cap_send_prepared_to_handle cid %u, handle %u\n", cid, handle);
302 
303     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
304 
305     // 0 - Connection handle : PB=10 : BC=00
306     bt_store_16(acl_buffer, 0, handle | (2 << 12) | (0 << 14));
307     // 2 - ACL length
308     bt_store_16(acl_buffer, 2,  len + 4);
309     // 4 - L2CAP packet length
310     bt_store_16(acl_buffer, 4,  len + 0);
311     // 6 - L2CAP channel DEST
312     bt_store_16(acl_buffer, 6, cid);
313     // send
314     int err = hci_send_acl_packet(acl_buffer, len+8);
315 
316     l2cap_hand_out_credits();
317 
318     return err;
319 }
320 
321 int l2cap_send_internal(uint16_t local_cid, uint8_t *data, uint16_t len){
322 
323     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
324         log_info("l2cap_send_internal cid %u, cannot send\n", local_cid);
325         return BTSTACK_ACL_BUFFERS_FULL;
326     }
327 
328     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
329 
330     memcpy(&acl_buffer[8], data, len);
331 
332     return l2cap_send_prepared(local_cid, len);
333 }
334 
335 int l2cap_send_connectionless(uint16_t handle, uint16_t cid, uint8_t *data, uint16_t len){
336 
337     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
338         log_info("l2cap_send_internal cid %u, cannot send\n", cid);
339         return BTSTACK_ACL_BUFFERS_FULL;
340     }
341 
342     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
343 
344     memcpy(&acl_buffer[8], data, len);
345 
346     return l2cap_send_prepared_connectionless(handle, cid, len);
347 }
348 
349 static inline void channelStateVarSetFlag(l2cap_channel_t *channel, L2CAP_CHANNEL_STATE_VAR flag){
350     channel->state_var = (L2CAP_CHANNEL_STATE_VAR) (channel->state_var | flag);
351 }
352 
353 static inline void channelStateVarClearFlag(l2cap_channel_t *channel, L2CAP_CHANNEL_STATE_VAR flag){
354     channel->state_var = (L2CAP_CHANNEL_STATE_VAR) (channel->state_var & ~flag);
355 }
356 
357 
358 
359 // MARK: L2CAP_RUN
360 // process outstanding signaling tasks
361 void l2cap_run(void){
362 
363     // check pending signaling responses
364     while (signaling_responses_pending){
365 
366         if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)) break;
367 
368         hci_con_handle_t handle = signaling_responses[0].handle;
369         uint8_t sig_id = signaling_responses[0].sig_id;
370         uint16_t infoType = signaling_responses[0].data;    // INFORMATION_REQUEST
371         uint16_t result   = signaling_responses[0].data;    // CONNECTION_REQUEST
372 
373         switch (signaling_responses[0].code){
374             case CONNECTION_REQUEST:
375                 l2cap_send_signaling_packet(handle, CONNECTION_RESPONSE, sig_id, 0, 0, result, 0);
376                 break;
377             case ECHO_REQUEST:
378                 l2cap_send_signaling_packet(handle, ECHO_RESPONSE, sig_id, 0, NULL);
379                 break;
380             case INFORMATION_REQUEST:
381                 if (infoType == 2) {
382                     uint32_t features = 0;
383                     // extended features request supported, however no features present
384                     l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, 4, &features);
385                 } else {
386                     // all other types are not supported
387                     l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 1, 0, NULL);
388                 }
389                 break;
390             default:
391                 // should not happen
392                 break;
393         }
394 
395         // remove first item
396         signaling_responses_pending--;
397         int i;
398         for (i=0; i < signaling_responses_pending; i++){
399             memcpy(&signaling_responses[i], &signaling_responses[i+1], sizeof(l2cap_signaling_response_t));
400         }
401     }
402 
403     uint8_t  config_options[4];
404     linked_item_t *it;
405     linked_item_t *next;
406     for (it = (linked_item_t *) l2cap_channels; it ; it = next){
407         next = it->next;    // cache next item as current item might get freed
408 
409         if (!hci_can_send_packet_now(HCI_COMMAND_DATA_PACKET)) break;
410         if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)) break;
411 
412         l2cap_channel_t * channel = (l2cap_channel_t *) it;
413 
414         // log_info("l2cap_run: state %u, var 0x%02x\n", channel->state, channel->state_var);
415 
416 
417         switch (channel->state){
418 
419             case L2CAP_STATE_WILL_SEND_CREATE_CONNECTION:
420                 // send connection request - set state first
421                 channel->state = L2CAP_STATE_WAIT_CONNECTION_COMPLETE;
422                 // BD_ADDR, Packet_Type, Page_Scan_Repetition_Mode, Reserved, Clock_Offset, Allow_Role_Switch
423                 hci_send_cmd(&hci_create_connection, channel->address, hci_usable_acl_packet_types(), 0, 0, 0, 1);
424                 break;
425 
426             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE:
427                 l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, 0, 0, channel->reason, 0);
428                 // discard channel - l2cap_finialize_channel_close without sending l2cap close event
429                 linked_list_remove(&l2cap_channels, (linked_item_t *) channel); // -- remove from list
430                 btstack_memory_l2cap_channel_free(channel);
431                 break;
432 
433             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT:
434                 channel->state = L2CAP_STATE_CONFIG;
435                 channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
436                 l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid, 0, 0);
437                 break;
438 
439             case L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST:
440                 // success, start l2cap handshake
441                 channel->local_sig_id = l2cap_next_sig_id();
442                 channel->state = L2CAP_STATE_WAIT_CONNECT_RSP;
443                 l2cap_send_signaling_packet( channel->handle, CONNECTION_REQUEST, channel->local_sig_id, channel->psm, channel->local_cid);
444                 break;
445 
446             case L2CAP_STATE_CONFIG:
447                 if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP){
448                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP);
449                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP);
450                     l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, 0, 0, 0, NULL);
451                 }
452                 else if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ){
453                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
454                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SENT_CONF_REQ);
455                     channel->local_sig_id = l2cap_next_sig_id();
456                     config_options[0] = 1; // MTU
457                     config_options[1] = 2; // len param
458                     bt_store_16( (uint8_t*)&config_options, 2, channel->local_mtu);
459                     l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->local_sig_id, channel->remote_cid, 0, 4, &config_options);
460                 }
461                 if (l2cap_channel_ready_for_open(channel)){
462                     channel->state = L2CAP_STATE_OPEN;
463                     l2cap_emit_channel_opened(channel, 0);  // success
464                     l2cap_emit_credits(channel, 1);
465                 }
466                 break;
467 
468             case L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE:
469                 l2cap_send_signaling_packet( channel->handle, DISCONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid);
470                 l2cap_finialize_channel_close(channel);  // -- remove from list
471                 break;
472 
473             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
474                 channel->local_sig_id = l2cap_next_sig_id();
475                 channel->state = L2CAP_STATE_WAIT_DISCONNECT;
476                 l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->local_sig_id, channel->remote_cid, channel->local_cid);
477                 break;
478             default:
479                 break;
480         }
481     }
482 }
483 
484 uint16_t l2cap_max_mtu(void){
485     return hci_max_acl_data_packet_length() - L2CAP_HEADER_SIZE;
486 }
487 
488 // open outgoing L2CAP channel
489 void l2cap_create_channel_internal(void * connection, btstack_packet_handler_t packet_handler,
490                                    bd_addr_t address, uint16_t psm, uint16_t mtu){
491 
492     // alloc structure
493     l2cap_channel_t * chan = (l2cap_channel_t*) btstack_memory_l2cap_channel_get();
494     if (!chan) {
495         // emit error event
496         l2cap_channel_t dummy_channel;
497         BD_ADDR_COPY(dummy_channel.address, address);
498         dummy_channel.psm = psm;
499         l2cap_emit_channel_opened(&dummy_channel, BTSTACK_MEMORY_ALLOC_FAILED);
500         return;
501     }
502     // limit local mtu to max acl packet length
503     if (mtu > l2cap_max_mtu()) {
504         mtu = l2cap_max_mtu();
505     }
506 
507     // fill in
508     BD_ADDR_COPY(chan->address, address);
509     chan->psm = psm;
510     chan->handle = 0;
511     chan->connection = connection;
512     chan->packet_handler = packet_handler;
513     chan->remote_mtu = L2CAP_MINIMAL_MTU;
514     chan->local_mtu = mtu;
515     chan->packets_granted = 0;
516 
517     // set initial state
518     chan->state = L2CAP_STATE_WILL_SEND_CREATE_CONNECTION;
519     chan->state_var = L2CAP_CHANNEL_STATE_VAR_NONE;
520     chan->remote_sig_id = L2CAP_SIG_ID_INVALID;
521     chan->local_sig_id = L2CAP_SIG_ID_INVALID;
522 
523     // add to connections list
524     linked_list_add(&l2cap_channels, (linked_item_t *) chan);
525 
526     l2cap_run();
527 }
528 
529 void l2cap_disconnect_internal(uint16_t local_cid, uint8_t reason){
530     // find channel for local_cid
531     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
532     if (channel) {
533         channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST;
534     }
535     // process
536     l2cap_run();
537 }
538 
539 static void l2cap_handle_connection_failed_for_addr(bd_addr_t address, uint8_t status){
540     linked_item_t *it = (linked_item_t *) &l2cap_channels;
541     while (it->next){
542         l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
543         if ( ! BD_ADDR_CMP( channel->address, address) ){
544             if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
545                 // failure, forward error code
546                 l2cap_emit_channel_opened(channel, status);
547                 // discard channel
548                 it->next = it->next->next;
549                 btstack_memory_l2cap_channel_free(channel);
550             }
551         } else {
552             it = it->next;
553         }
554     }
555 }
556 
557 static void l2cap_handle_connection_success_for_addr(bd_addr_t address, hci_con_handle_t handle){
558     linked_item_t *it;
559     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
560         l2cap_channel_t * channel = (l2cap_channel_t *) it;
561         if ( ! BD_ADDR_CMP( channel->address, address) ){
562             if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
563                 // success, start l2cap handshake
564                 channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST;
565                 channel->handle = handle;
566                 channel->local_cid = l2cap_next_local_cid();
567             }
568         }
569     }
570     // process
571     l2cap_run();
572 }
573 
574 void l2cap_event_handler( uint8_t *packet, uint16_t size ){
575 
576     bd_addr_t address;
577     hci_con_handle_t handle;
578     l2cap_channel_t * channel;
579     linked_item_t *it;
580     int hci_con_used;
581 
582     switch(packet[0]){
583 
584         // handle connection complete events
585         case HCI_EVENT_CONNECTION_COMPLETE:
586             bt_flip_addr(address, &packet[5]);
587             if (packet[2] == 0){
588                 handle = READ_BT_16(packet, 3);
589                 l2cap_handle_connection_success_for_addr(address, handle);
590             } else {
591                 l2cap_handle_connection_failed_for_addr(address, packet[2]);
592             }
593             break;
594 
595         // handle successful create connection cancel command
596         case HCI_EVENT_COMMAND_COMPLETE:
597             if ( COMMAND_COMPLETE_EVENT(packet, hci_create_connection_cancel) ) {
598                 if (packet[5] == 0){
599                     bt_flip_addr(address, &packet[6]);
600                     // CONNECTION TERMINATED BY LOCAL HOST (0X16)
601                     l2cap_handle_connection_failed_for_addr(address, 0x16);
602                 }
603             }
604             l2cap_run();    // try sending signaling packets first
605             break;
606 
607         case HCI_EVENT_COMMAND_STATUS:
608             l2cap_run();    // try sending signaling packets first
609             break;
610 
611         // handle disconnection complete events
612         case HCI_EVENT_DISCONNECTION_COMPLETE:
613             // send l2cap disconnect events for all channels on this handle
614             handle = READ_BT_16(packet, 3);
615             it = (linked_item_t *) &l2cap_channels;
616             while (it->next){
617                 l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
618                 if ( channel->handle == handle ){
619                     // update prev item before free'ing next element - don't call l2cap_finalize_channel_close
620                     it->next = it->next->next;
621                     l2cap_emit_channel_closed(channel);
622                     btstack_memory_l2cap_channel_free(channel);
623                 } else {
624                     it = it->next;
625                 }
626             }
627             break;
628 
629         case HCI_EVENT_NUMBER_OF_COMPLETED_PACKETS:
630             l2cap_run();    // try sending signaling packets first
631             l2cap_hand_out_credits();
632             break;
633 
634         // HCI Connection Timeouts
635         case L2CAP_EVENT_TIMEOUT_CHECK:
636             handle = READ_BT_16(packet, 2);
637             if (hci_authentication_active_for_handle(handle)) break;
638             hci_con_used = 0;
639             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
640                 channel = (l2cap_channel_t *) it;
641                 if (channel->handle == handle) {
642                     hci_con_used = 1;
643                 }
644             }
645             if (hci_con_used) break;
646             if (!hci_can_send_packet_now(HCI_COMMAND_DATA_PACKET)) break;
647             hci_send_cmd(&hci_disconnect, handle, 0x13); // remote closed connection
648             break;
649 
650         case DAEMON_EVENT_HCI_PACKET_SENT:
651             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
652                 channel = (l2cap_channel_t *) it;
653                 if (channel->packet_handler) {
654                     (* (channel->packet_handler))(HCI_EVENT_PACKET, channel->local_cid, packet, size);
655                 }
656             }
657             if (attribute_protocol_packet_handler) {
658                 (*attribute_protocol_packet_handler)(HCI_EVENT_PACKET, 0, packet, size);
659             }
660             if (security_protocol_packet_handler) {
661                 (*security_protocol_packet_handler)(HCI_EVENT_PACKET, 0, packet, size);
662             }
663             break;
664 
665         default:
666             break;
667     }
668 
669     // pass on
670     (*packet_handler)(NULL, HCI_EVENT_PACKET, 0, packet, size);
671 }
672 
673 static void l2cap_handle_disconnect_request(l2cap_channel_t *channel, uint16_t identifier){
674     channel->remote_sig_id = identifier;
675     channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE;
676     l2cap_run();
677 }
678 
679 static void l2cap_register_signaling_response(hci_con_handle_t handle, uint8_t code, uint8_t sig_id, uint16_t data){
680     if (signaling_responses_pending < NR_PENDING_SIGNALING_RESPONSES) {
681         signaling_responses[signaling_responses_pending].handle = handle;
682         signaling_responses[signaling_responses_pending].code = code;
683         signaling_responses[signaling_responses_pending].sig_id = sig_id;
684         signaling_responses[signaling_responses_pending].data = data;
685         signaling_responses_pending++;
686         l2cap_run();
687     }
688 }
689 
690 static void l2cap_handle_connection_request(hci_con_handle_t handle, uint8_t sig_id, uint16_t psm, uint16_t source_cid){
691 
692     // log_info("l2cap_handle_connection_request for handle %u, psm %u cid %u\n", handle, psm, source_cid);
693     l2cap_service_t *service = l2cap_get_service(psm);
694     if (!service) {
695         // 0x0002 PSM not supported
696         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0002);
697         return;
698     }
699 
700     hci_connection_t * hci_connection = connection_for_handle( handle );
701     if (!hci_connection) {
702         //
703         log_error("no hci_connection for handle %u\n", handle);
704         return;
705     }
706     // alloc structure
707     // log_info("l2cap_handle_connection_request register channel\n");
708     l2cap_channel_t * channel = (l2cap_channel_t*) btstack_memory_l2cap_channel_get();
709     if (!channel){
710         // 0x0004 No resources available
711         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0004);
712         return;
713     }
714 
715     // fill in
716     BD_ADDR_COPY(channel->address, hci_connection->address);
717     channel->psm = psm;
718     channel->handle = handle;
719     channel->connection = service->connection;
720     channel->packet_handler = service->packet_handler;
721     channel->local_cid  = l2cap_next_local_cid();
722     channel->remote_cid = source_cid;
723     channel->local_mtu  = service->mtu;
724     channel->remote_mtu = L2CAP_DEFAULT_MTU;
725     channel->packets_granted = 0;
726     channel->remote_sig_id = sig_id;
727 
728     // limit local mtu to max acl packet length
729     if (channel->local_mtu > l2cap_max_mtu()) {
730         channel->local_mtu = l2cap_max_mtu();
731     }
732 
733     // set initial state
734     channel->state = L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT;
735     channel->state_var = L2CAP_CHANNEL_STATE_VAR_NONE;
736 
737     // add to connections list
738     linked_list_add(&l2cap_channels, (linked_item_t *) channel);
739 
740     // emit incoming connection request
741     l2cap_emit_connection_request(channel);
742 }
743 
744 void l2cap_accept_connection_internal(uint16_t local_cid){
745     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
746     if (!channel) {
747         log_error("l2cap_accept_connection_internal called but local_cid 0x%x not found", local_cid);
748         return;
749     }
750 
751     channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT;
752 
753     // process
754     l2cap_run();
755 }
756 
757 void l2cap_decline_connection_internal(uint16_t local_cid, uint8_t reason){
758     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid( local_cid);
759     if (!channel) {
760         log_error( "l2cap_decline_connection_internal called but local_cid 0x%x not found", local_cid);
761         return;
762     }
763     channel->state  = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE;
764     channel->reason = reason;
765     l2cap_run();
766 }
767 
768 void l2cap_signaling_handle_configure_request(l2cap_channel_t *channel, uint8_t *command){
769 
770     channel->remote_sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
771 
772     // accept the other's configuration options
773     uint16_t end_pos = 4 + READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
774     uint16_t pos     = 8;
775     while (pos < end_pos){
776         uint8_t type   = command[pos++];
777         uint8_t length = command[pos++];
778         // MTU { type(8): 1, len(8):2, MTU(16) }
779         if ((type & 0x7f) == 1 && length == 2){
780             channel->remote_mtu = READ_BT_16(command, pos);
781             // log_info("l2cap cid %u, remote mtu %u\n", channel->local_cid, channel->remote_mtu);
782         }
783         pos += length;
784     }
785 }
786 
787 static int l2cap_channel_ready_for_open(l2cap_channel_t *channel){
788     // log_info("l2cap_channel_ready_for_open 0x%02x\n", channel->state_var);
789     if ((channel->state_var & L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_RSP) == 0) return 0;
790     if ((channel->state_var & L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP) == 0) return 0;
791     return 1;
792 }
793 
794 
795 void l2cap_signaling_handler_channel(l2cap_channel_t *channel, uint8_t *command){
796 
797     uint8_t  code       = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
798     uint8_t  identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
799     uint16_t result = 0;
800 
801     log_info("L2CAP signaling handler code %u, state %u\n", code, channel->state);
802 
803     // handle DISCONNECT REQUESTS seperately
804     if (code == DISCONNECTION_REQUEST){
805         switch (channel->state){
806             case L2CAP_STATE_CONFIG:
807             case L2CAP_STATE_OPEN:
808             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
809             case L2CAP_STATE_WAIT_DISCONNECT:
810                 l2cap_handle_disconnect_request(channel, identifier);
811                 break;
812 
813             default:
814                 // ignore in other states
815                 break;
816         }
817         return;
818     }
819 
820     // @STATEMACHINE(l2cap)
821     switch (channel->state) {
822 
823         case L2CAP_STATE_WAIT_CONNECT_RSP:
824             switch (code){
825                 case CONNECTION_RESPONSE:
826                     result = READ_BT_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
827                     switch (result) {
828                         case 0:
829                             // successful connection
830                             channel->remote_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
831                             channel->state = L2CAP_STATE_CONFIG;
832                             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
833                             break;
834                         case 1:
835                             // connection pending. get some coffee
836                             break;
837                         default:
838                             // channel closed
839                             channel->state = L2CAP_STATE_CLOSED;
840 
841                             // map l2cap connection response result to BTstack status enumeration
842                             l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result);
843 
844                             // drop link key if security block
845                             if (L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result == L2CAP_CONNECTION_RESPONSE_RESULT_REFUSED_SECURITY){
846                                 hci_drop_link_key_for_bd_addr(&channel->address);
847                             }
848 
849                             // discard channel
850                             linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
851                             btstack_memory_l2cap_channel_free(channel);
852                             break;
853                     }
854                     break;
855 
856                 default:
857                     //@TODO: implement other signaling packets
858                     break;
859             }
860             break;
861 
862         case L2CAP_STATE_CONFIG:
863             switch (code) {
864                 case CONFIGURE_REQUEST:
865                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_REQ);
866                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP);
867                     l2cap_signaling_handle_configure_request(channel, command);
868                     break;
869                 case CONFIGURE_RESPONSE:
870                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_RSP);
871                     break;
872                 default:
873                     break;
874             }
875             if (l2cap_channel_ready_for_open(channel)){
876                 // for open:
877                 channel->state = L2CAP_STATE_OPEN;
878                 l2cap_emit_channel_opened(channel, 0);
879                 l2cap_emit_credits(channel, 1);
880             }
881             break;
882 
883         case L2CAP_STATE_WAIT_DISCONNECT:
884             switch (code) {
885                 case DISCONNECTION_RESPONSE:
886                     l2cap_finialize_channel_close(channel);
887                     break;
888                 default:
889                     //@TODO: implement other signaling packets
890                     break;
891             }
892             break;
893 
894         case L2CAP_STATE_CLOSED:
895             // @TODO handle incoming requests
896             break;
897 
898         case L2CAP_STATE_OPEN:
899             //@TODO: implement other signaling packets, e.g. re-configure
900             break;
901         default:
902             break;
903     }
904     // log_info("new state %u\n", channel->state);
905 }
906 
907 
908 void l2cap_signaling_handler_dispatch( hci_con_handle_t handle, uint8_t * command){
909 
910     // get code, signalind identifier and command len
911     uint8_t code   = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
912     uint8_t sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
913 
914     // not for a particular channel, and not CONNECTION_REQUEST, ECHO_[REQUEST|RESPONSE], INFORMATION_REQUEST
915     if (code < 1 || code == ECHO_RESPONSE || code > INFORMATION_REQUEST){
916         return;
917     }
918 
919     // general commands without an assigned channel
920     switch(code) {
921 
922         case CONNECTION_REQUEST: {
923             uint16_t psm =        READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
924             uint16_t source_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+2);
925             l2cap_handle_connection_request(handle, sig_id, psm, source_cid);
926             return;
927         }
928 
929         case ECHO_REQUEST:
930             l2cap_register_signaling_response(handle, code, sig_id, 0);
931             return;
932 
933         case INFORMATION_REQUEST: {
934             uint16_t infoType = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
935             l2cap_register_signaling_response(handle, code, sig_id, infoType);
936             return;
937         }
938 
939         default:
940             break;
941     }
942 
943 
944     // Get potential destination CID
945     uint16_t dest_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
946 
947     // Find channel for this sig_id and connection handle
948     linked_item_t *it;
949     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
950         l2cap_channel_t * channel = (l2cap_channel_t *) it;
951         if (channel->handle == handle) {
952             if (code & 1) {
953                 // match odd commands (responses) by previous signaling identifier
954                 if (channel->local_sig_id == sig_id) {
955                     l2cap_signaling_handler_channel(channel, command);
956                     break;
957                 }
958             } else {
959                 // match even commands (requests) by local channel id
960                 if (channel->local_cid == dest_cid) {
961                     l2cap_signaling_handler_channel(channel, command);
962                     break;
963                 }
964             }
965         }
966     }
967 }
968 
969 void l2cap_acl_handler( uint8_t *packet, uint16_t size ){
970 
971     // Get Channel ID
972     uint16_t channel_id = READ_L2CAP_CHANNEL_ID(packet);
973     hci_con_handle_t handle = READ_ACL_CONNECTION_HANDLE(packet);
974 
975     switch (channel_id) {
976 
977         case L2CAP_CID_SIGNALING: {
978 
979             uint16_t command_offset = 8;
980             while (command_offset < size) {
981 
982                 // handle signaling commands
983                 l2cap_signaling_handler_dispatch(handle, &packet[command_offset]);
984 
985                 // increment command_offset
986                 command_offset += L2CAP_SIGNALING_COMMAND_DATA_OFFSET + READ_BT_16(packet, command_offset + L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
987             }
988             break;
989         }
990 
991         case L2CAP_CID_ATTRIBUTE_PROTOCOL:
992             if (attribute_protocol_packet_handler) {
993                 (*attribute_protocol_packet_handler)(ATT_DATA_PACKET, handle, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
994             }
995             break;
996 
997         case L2CAP_CID_SECURITY_MANAGER_PROTOCOL:
998             if (security_protocol_packet_handler) {
999                 (*security_protocol_packet_handler)(SM_DATA_PACKET, handle, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1000             }
1001             break;
1002 
1003         default: {
1004             // Find channel for this channel_id and connection handle
1005             l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(channel_id);
1006             if (channel) {
1007                 l2cap_dispatch(channel, L2CAP_DATA_PACKET, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1008             }
1009             break;
1010         }
1011     }
1012 
1013     l2cap_run();
1014 }
1015 
1016 static void l2cap_packet_handler(uint8_t packet_type, uint8_t *packet, uint16_t size){
1017     switch (packet_type) {
1018         case HCI_EVENT_PACKET:
1019             l2cap_event_handler(packet, size);
1020             break;
1021         case HCI_ACL_DATA_PACKET:
1022             l2cap_acl_handler(packet, size);
1023             break;
1024         default:
1025             break;
1026     }
1027 }
1028 
1029 // finalize closed channel - l2cap_handle_disconnect_request & DISCONNECTION_RESPONSE
1030 void l2cap_finialize_channel_close(l2cap_channel_t *channel){
1031     channel->state = L2CAP_STATE_CLOSED;
1032     l2cap_emit_channel_closed(channel);
1033     // discard channel
1034     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
1035     btstack_memory_l2cap_channel_free(channel);
1036 }
1037 
1038 l2cap_service_t * l2cap_get_service(uint16_t psm){
1039     linked_item_t *it;
1040 
1041     // close open channels
1042     for (it = (linked_item_t *) l2cap_services; it ; it = it->next){
1043         l2cap_service_t * service = ((l2cap_service_t *) it);
1044         if ( service->psm == psm){
1045             return service;
1046         };
1047     }
1048     return NULL;
1049 }
1050 
1051 void l2cap_register_service_internal(void *connection, btstack_packet_handler_t packet_handler, uint16_t psm, uint16_t mtu){
1052     // check for alread registered psm
1053     // TODO: emit error event
1054     l2cap_service_t *service = l2cap_get_service(psm);
1055     if (service) {
1056         log_error("l2cap_register_service_internal: PSM %u already registered\n", psm);
1057         l2cap_emit_service_registered(connection, L2CAP_SERVICE_ALREADY_REGISTERED, psm);
1058         return;
1059     }
1060 
1061     // alloc structure
1062     // TODO: emit error event
1063     service = (l2cap_service_t *) btstack_memory_l2cap_service_get();
1064     if (!service) {
1065         log_error("l2cap_register_service_internal: no memory for l2cap_service_t\n");
1066         l2cap_emit_service_registered(connection, BTSTACK_MEMORY_ALLOC_FAILED, psm);
1067         return;
1068     }
1069 
1070     // fill in
1071     service->psm = psm;
1072     service->mtu = mtu;
1073     service->connection = connection;
1074     service->packet_handler = packet_handler;
1075 
1076     // add to services list
1077     linked_list_add(&l2cap_services, (linked_item_t *) service);
1078 
1079     // enable page scan
1080     hci_connectable_control(1);
1081 
1082     // done
1083     l2cap_emit_service_registered(connection, 0, psm);
1084 }
1085 
1086 void l2cap_unregister_service_internal(void *connection, uint16_t psm){
1087     l2cap_service_t *service = l2cap_get_service(psm);
1088     if (!service) return;
1089     linked_list_remove(&l2cap_services, (linked_item_t *) service);
1090     btstack_memory_l2cap_service_free(service);
1091 
1092     // disable page scan when no services registered
1093     if (!linked_list_empty(&l2cap_services)) return;
1094     hci_connectable_control(0);
1095 }
1096 
1097 //
1098 void l2cap_close_connection(void *connection){
1099     linked_item_t *it;
1100 
1101     // close open channels - note to myself: no channel is freed, so no new for fancy iterator tricks
1102     l2cap_channel_t * channel;
1103     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
1104         channel = (l2cap_channel_t *) it;
1105         if (channel->connection == connection) {
1106             channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST;
1107         }
1108     }
1109 
1110     // unregister services
1111     it = (linked_item_t *) &l2cap_services;
1112     while (it->next) {
1113         l2cap_service_t * service = (l2cap_service_t *) it->next;
1114         if (service->connection == connection){
1115             it->next = it->next->next;
1116             btstack_memory_l2cap_service_free(service);
1117         } else {
1118             it = it->next;
1119         }
1120     }
1121 
1122     // process
1123     l2cap_run();
1124 }
1125 
1126 // Bluetooth 4.0 - allows to register handler for Attribute Protocol and Security Manager Protocol
1127 void l2cap_register_fixed_channel(btstack_packet_handler_t packet_handler, uint16_t channel_id) {
1128     switch(channel_id){
1129         case L2CAP_CID_ATTRIBUTE_PROTOCOL:
1130             attribute_protocol_packet_handler = packet_handler;
1131             break;
1132         case L2CAP_CID_SECURITY_MANAGER_PROTOCOL:
1133             security_protocol_packet_handler = packet_handler;
1134             break;
1135     }
1136 }
1137 
1138