xref: /btstack/src/l2cap.c (revision 28ca2b4607e125f45dc135e6777e2b6822e52f41)
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     new_credits_blocked = 0;
86     signaling_responses_pending = 0;
87 
88     l2cap_channels = NULL;
89     l2cap_services = NULL;
90 
91     packet_handler = null_packet_handler;
92 
93     //
94     // register callback with HCI
95     //
96     hci_register_packet_handler(&l2cap_packet_handler);
97     hci_connectable_control(0); // no services yet
98 }
99 
100 
101 /** Register L2CAP packet handlers */
102 static void null_packet_handler(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
103 }
104 void l2cap_register_packet_handler(void (*handler)(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size)){
105     packet_handler = handler;
106 }
107 
108 //  notify client/protocol handler
109 void l2cap_dispatch(l2cap_channel_t *channel, uint8_t type, uint8_t * data, uint16_t size){
110     if (channel->packet_handler) {
111         (* (channel->packet_handler))(type, channel->local_cid, data, size);
112     } else {
113         (*packet_handler)(channel->connection, type, channel->local_cid, data, size);
114     }
115 }
116 
117 void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status) {
118     uint8_t event[21];
119     event[0] = L2CAP_EVENT_CHANNEL_OPENED;
120     event[1] = sizeof(event) - 2;
121     event[2] = status;
122     bt_flip_addr(&event[3], channel->address);
123     bt_store_16(event,  9, channel->handle);
124     bt_store_16(event, 11, channel->psm);
125     bt_store_16(event, 13, channel->local_cid);
126     bt_store_16(event, 15, channel->remote_cid);
127     bt_store_16(event, 17, channel->local_mtu);
128     bt_store_16(event, 19, channel->remote_mtu);
129     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
130     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
131 }
132 
133 void l2cap_emit_channel_closed(l2cap_channel_t *channel) {
134     uint8_t event[4];
135     event[0] = L2CAP_EVENT_CHANNEL_CLOSED;
136     event[1] = sizeof(event) - 2;
137     bt_store_16(event, 2, channel->local_cid);
138     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
139     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
140 }
141 
142 void l2cap_emit_connection_request(l2cap_channel_t *channel) {
143     uint8_t event[16];
144     event[0] = L2CAP_EVENT_INCOMING_CONNECTION;
145     event[1] = sizeof(event) - 2;
146     bt_flip_addr(&event[2], channel->address);
147     bt_store_16(event,  8, channel->handle);
148     bt_store_16(event, 10, channel->psm);
149     bt_store_16(event, 12, channel->local_cid);
150     bt_store_16(event, 14, channel->remote_cid);
151     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
152     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
153 }
154 
155 static void l2cap_emit_service_registered(void *connection, uint8_t status, uint16_t psm){
156     uint8_t event[5];
157     event[0] = L2CAP_EVENT_SERVICE_REGISTERED;
158     event[1] = sizeof(event) - 2;
159     event[2] = status;
160     bt_store_16(event, 3, psm);
161     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
162     (*packet_handler)(connection, HCI_EVENT_PACKET, 0, event, sizeof(event));
163 }
164 
165 void l2cap_emit_credits(l2cap_channel_t *channel, uint8_t credits) {
166     // track credits
167     channel->packets_granted += credits;
168     // log_info("l2cap_emit_credits for cid %u, credits given: %u (+%u)\n", channel->local_cid, channel->packets_granted, credits);
169 
170     uint8_t event[5];
171     event[0] = L2CAP_EVENT_CREDITS;
172     event[1] = sizeof(event) - 2;
173     bt_store_16(event, 2, channel->local_cid);
174     event[4] = credits;
175     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
176     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
177 }
178 
179 void l2cap_block_new_credits(uint8_t blocked){
180     new_credits_blocked = blocked;
181 }
182 
183 void l2cap_hand_out_credits(void){
184 
185     if (new_credits_blocked) return;    // we're told not to. used by daemon
186 
187     linked_item_t *it;
188     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
189         if (!hci_number_free_acl_slots()) return;
190         l2cap_channel_t * channel = (l2cap_channel_t *) it;
191         if (channel->state != L2CAP_STATE_OPEN) continue;
192         if (hci_number_outgoing_packets(channel->handle) < NR_BUFFERED_ACL_PACKETS && channel->packets_granted == 0) {
193             l2cap_emit_credits(channel, 1);
194         }
195     }
196 }
197 
198 l2cap_channel_t * l2cap_get_channel_for_local_cid(uint16_t local_cid){
199     linked_item_t *it;
200     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
201         l2cap_channel_t * channel = (l2cap_channel_t *) it;
202         if ( channel->local_cid == local_cid) {
203             return channel;
204         }
205     }
206     return NULL;
207 }
208 
209 int  l2cap_can_send_packet_now(uint16_t local_cid){
210     l2cap_channel_t *channel = l2cap_get_channel_for_local_cid(local_cid);
211     if (!channel) return 0;
212     if (!channel->packets_granted) return 0;
213     return hci_can_send_packet_now(HCI_ACL_DATA_PACKET);
214 }
215 
216 uint16_t l2cap_get_remote_mtu_for_local_cid(uint16_t local_cid){
217     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
218     if (channel) {
219         return channel->remote_mtu;
220     }
221     return 0;
222 }
223 
224 int l2cap_send_signaling_packet(hci_con_handle_t handle, L2CAP_SIGNALING_COMMANDS cmd, uint8_t identifier, ...){
225 
226     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
227         log_info("l2cap_send_signaling_packet, cannot send\n");
228         return BTSTACK_ACL_BUFFERS_FULL;
229     }
230 
231     // log_info("l2cap_send_signaling_packet type %u\n", cmd);
232     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
233     va_list argptr;
234     va_start(argptr, identifier);
235     uint16_t len = l2cap_create_signaling_internal(acl_buffer, handle, cmd, identifier, argptr);
236     va_end(argptr);
237     // log_info("l2cap_send_signaling_packet con %u!\n", handle);
238     return hci_send_acl_packet(acl_buffer, len);
239 }
240 
241 uint8_t *l2cap_get_outgoing_buffer(void){
242     return hci_get_outgoing_acl_packet_buffer() + COMPLETE_L2CAP_HEADER; // 8 bytes
243 }
244 
245 int l2cap_send_prepared(uint16_t local_cid, uint16_t len){
246 
247     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
248         log_info("l2cap_send_internal cid %u, cannot send\n", local_cid);
249         return BTSTACK_ACL_BUFFERS_FULL;
250     }
251 
252     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
253     if (!channel) {
254         log_error("l2cap_send_internal no channel for cid %u\n", local_cid);
255         return -1;   // TODO: define error
256     }
257 
258     if (channel->packets_granted == 0){
259         log_error("l2cap_send_internal cid %u, no credits!\n", local_cid);
260         return -1;  // TODO: define error
261     }
262 
263     --channel->packets_granted;
264 
265     log_debug("l2cap_send_internal cid %u, handle %u, 1 credit used, credits left %u;\n",
266                   local_cid, channel->handle, channel->packets_granted);
267 
268     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
269 
270     // 0 - Connection handle : PB=10 : BC=00
271     bt_store_16(acl_buffer, 0, channel->handle | (2 << 12) | (0 << 14));
272     // 2 - ACL length
273     bt_store_16(acl_buffer, 2,  len + 4);
274     // 4 - L2CAP packet length
275     bt_store_16(acl_buffer, 4,  len + 0);
276     // 6 - L2CAP channel DEST
277     bt_store_16(acl_buffer, 6, channel->remote_cid);
278     // send
279     int err = hci_send_acl_packet(acl_buffer, len+8);
280 
281     l2cap_hand_out_credits();
282 
283     return err;
284 }
285 
286 int l2cap_send_internal(uint16_t local_cid, uint8_t *data, uint16_t len){
287 
288     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
289         log_info("l2cap_send_internal cid %u, cannot send\n", local_cid);
290         return BTSTACK_ACL_BUFFERS_FULL;
291     }
292 
293     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
294 
295     memcpy(&acl_buffer[8], data, len);
296 
297     return l2cap_send_prepared(local_cid, len);
298 }
299 
300 static inline void channelStateVarSetFlag(l2cap_channel_t *channel, L2CAP_CHANNEL_STATE_VAR flag){
301     channel->state_var = (L2CAP_CHANNEL_STATE_VAR) (channel->state_var | flag);
302 }
303 
304 static inline void channelStateVarClearFlag(l2cap_channel_t *channel, L2CAP_CHANNEL_STATE_VAR flag){
305     channel->state_var = (L2CAP_CHANNEL_STATE_VAR) (channel->state_var & ~flag);
306 }
307 
308 
309 
310 // MARK: L2CAP_RUN
311 // process outstanding signaling tasks
312 void l2cap_run(void){
313 
314     // check pending signaling responses
315     while (signaling_responses_pending){
316 
317         if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)) break;
318 
319         hci_con_handle_t handle = signaling_responses[0].handle;
320         uint8_t sig_id = signaling_responses[0].sig_id;
321         uint16_t infoType = signaling_responses[0].data;    // INFORMATION_REQUEST
322         uint16_t result   = signaling_responses[0].data;    // CONNECTION_REQUEST
323 
324         switch (signaling_responses[0].code){
325             case CONNECTION_REQUEST:
326                 l2cap_send_signaling_packet(handle, CONNECTION_RESPONSE, sig_id, 0, 0, result, 0);
327                 break;
328             case ECHO_REQUEST:
329                 l2cap_send_signaling_packet(handle, ECHO_RESPONSE, sig_id, 0, NULL);
330                 break;
331             case INFORMATION_REQUEST:
332                 if (infoType == 2) {
333                     uint32_t features = 0;
334                     // extended features request supported, however no features present
335                     l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, 4, &features);
336                 } else {
337                     // all other types are not supported
338                     l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 1, 0, NULL);
339                 }
340                 break;
341             default:
342                 // should not happen
343                 break;
344         }
345 
346         // remove first item
347         signaling_responses_pending--;
348         int i;
349         for (i=0; i < signaling_responses_pending; i++){
350             memcpy(&signaling_responses[i], &signaling_responses[i+1], sizeof(l2cap_signaling_response_t));
351         }
352     }
353 
354     uint8_t  config_options[4];
355     linked_item_t *it;
356     linked_item_t *next;
357     for (it = (linked_item_t *) l2cap_channels; it ; it = next){
358         next = it->next;    // cache next item as current item might get freed
359 
360         if (!hci_can_send_packet_now(HCI_COMMAND_DATA_PACKET)) break;
361         if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)) break;
362 
363         l2cap_channel_t * channel = (l2cap_channel_t *) it;
364 
365         // log_info("l2cap_run: state %u, var 0x%02x\n", channel->state, channel->state_var);
366 
367 
368         switch (channel->state){
369 
370             case L2CAP_STATE_WILL_SEND_CREATE_CONNECTION:
371                 // send connection request - set state first
372                 channel->state = L2CAP_STATE_WAIT_CONNECTION_COMPLETE;
373                 // BD_ADDR, Packet_Type, Page_Scan_Repetition_Mode, Reserved, Clock_Offset, Allow_Role_Switch
374                 hci_send_cmd(&hci_create_connection, channel->address, hci_usable_acl_packet_types(), 0, 0, 0, 1);
375                 break;
376 
377             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE:
378                 l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, 0, 0, channel->reason, 0);
379                 // discard channel - l2cap_finialize_channel_close without sending l2cap close event
380                 linked_list_remove(&l2cap_channels, (linked_item_t *) channel); // -- remove from list
381                 btstack_memory_l2cap_channel_free(channel);
382                 break;
383 
384             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT:
385                 channel->state = L2CAP_STATE_CONFIG;
386                 channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
387                 l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid, 0, 0);
388                 break;
389 
390             case L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST:
391                 // success, start l2cap handshake
392                 channel->local_sig_id = l2cap_next_sig_id();
393                 channel->state = L2CAP_STATE_WAIT_CONNECT_RSP;
394                 l2cap_send_signaling_packet( channel->handle, CONNECTION_REQUEST, channel->local_sig_id, channel->psm, channel->local_cid);
395                 break;
396 
397             case L2CAP_STATE_CONFIG:
398                 if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP){
399                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP);
400                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP);
401                     l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, 0, 0, 0, NULL);
402                 }
403                 else if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ){
404                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
405                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SENT_CONF_REQ);
406                     channel->local_sig_id = l2cap_next_sig_id();
407                     config_options[0] = 1; // MTU
408                     config_options[1] = 2; // len param
409                     bt_store_16( (uint8_t*)&config_options, 2, channel->local_mtu);
410                     l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->local_sig_id, channel->remote_cid, 0, 4, &config_options);
411                 }
412                 if (l2cap_channel_ready_for_open(channel)){
413                     channel->state = L2CAP_STATE_OPEN;
414                     l2cap_emit_channel_opened(channel, 0);  // success
415                     l2cap_emit_credits(channel, 1);
416                 }
417                 break;
418 
419             case L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE:
420                 l2cap_send_signaling_packet( channel->handle, DISCONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid);
421                 l2cap_finialize_channel_close(channel);  // -- remove from list
422                 break;
423 
424             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
425                 channel->local_sig_id = l2cap_next_sig_id();
426                 channel->state = L2CAP_STATE_WAIT_DISCONNECT;
427                 l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->local_sig_id, channel->remote_cid, channel->local_cid);
428                 break;
429             default:
430                 break;
431         }
432     }
433 }
434 
435 uint16_t l2cap_max_mtu(void){
436     return hci_max_acl_data_packet_length() - L2CAP_HEADER_SIZE;
437 }
438 
439 // open outgoing L2CAP channel
440 void l2cap_create_channel_internal(void * connection, btstack_packet_handler_t packet_handler,
441                                    bd_addr_t address, uint16_t psm, uint16_t mtu){
442 
443     // alloc structure
444     l2cap_channel_t * chan = (l2cap_channel_t*) btstack_memory_l2cap_channel_get();
445     if (!chan) {
446         // emit error event
447         l2cap_channel_t dummy_channel;
448         BD_ADDR_COPY(dummy_channel.address, address);
449         dummy_channel.psm = psm;
450         l2cap_emit_channel_opened(&dummy_channel, BTSTACK_MEMORY_ALLOC_FAILED);
451         return;
452     }
453     // limit local mtu to max acl packet length
454     if (mtu > l2cap_max_mtu()) {
455         mtu = l2cap_max_mtu();
456     }
457 
458     // fill in
459     BD_ADDR_COPY(chan->address, address);
460     chan->psm = psm;
461     chan->handle = 0;
462     chan->connection = connection;
463     chan->packet_handler = packet_handler;
464     chan->remote_mtu = L2CAP_MINIMAL_MTU;
465     chan->local_mtu = mtu;
466     chan->packets_granted = 0;
467 
468     // set initial state
469     chan->state = L2CAP_STATE_WILL_SEND_CREATE_CONNECTION;
470     chan->state_var = L2CAP_CHANNEL_STATE_VAR_NONE;
471     chan->remote_sig_id = L2CAP_SIG_ID_INVALID;
472     chan->local_sig_id = L2CAP_SIG_ID_INVALID;
473 
474     // add to connections list
475     linked_list_add(&l2cap_channels, (linked_item_t *) chan);
476 
477     l2cap_run();
478 }
479 
480 void l2cap_disconnect_internal(uint16_t local_cid, uint8_t reason){
481     // find channel for local_cid
482     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
483     if (channel) {
484         channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST;
485     }
486     // process
487     l2cap_run();
488 }
489 
490 static void l2cap_handle_connection_failed_for_addr(bd_addr_t address, uint8_t status){
491     linked_item_t *it = (linked_item_t *) &l2cap_channels;
492     while (it->next){
493         l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
494         if ( ! BD_ADDR_CMP( channel->address, address) ){
495             if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
496                 // failure, forward error code
497                 l2cap_emit_channel_opened(channel, status);
498                 // discard channel
499                 it->next = it->next->next;
500                 btstack_memory_l2cap_channel_free(channel);
501             }
502         } else {
503             it = it->next;
504         }
505     }
506 }
507 
508 static void l2cap_handle_connection_success_for_addr(bd_addr_t address, hci_con_handle_t handle){
509     linked_item_t *it;
510     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
511         l2cap_channel_t * channel = (l2cap_channel_t *) it;
512         if ( ! BD_ADDR_CMP( channel->address, address) ){
513             if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
514                 // success, start l2cap handshake
515                 channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST;
516                 channel->handle = handle;
517                 channel->local_cid = l2cap_next_local_cid();
518             }
519         }
520     }
521     // process
522     l2cap_run();
523 }
524 
525 void l2cap_event_handler( uint8_t *packet, uint16_t size ){
526 
527     bd_addr_t address;
528     hci_con_handle_t handle;
529     l2cap_channel_t * channel;
530     linked_item_t *it;
531     int hci_con_used;
532 
533     switch(packet[0]){
534 
535         // handle connection complete events
536         case HCI_EVENT_CONNECTION_COMPLETE:
537             bt_flip_addr(address, &packet[5]);
538             if (packet[2] == 0){
539                 handle = READ_BT_16(packet, 3);
540                 l2cap_handle_connection_success_for_addr(address, handle);
541             } else {
542                 l2cap_handle_connection_failed_for_addr(address, packet[2]);
543             }
544             break;
545 
546         // handle successful create connection cancel command
547         case HCI_EVENT_COMMAND_COMPLETE:
548             if ( COMMAND_COMPLETE_EVENT(packet, hci_create_connection_cancel) ) {
549                 if (packet[5] == 0){
550                     bt_flip_addr(address, &packet[6]);
551                     // CONNECTION TERMINATED BY LOCAL HOST (0X16)
552                     l2cap_handle_connection_failed_for_addr(address, 0x16);
553                 }
554             }
555             l2cap_run();    // try sending signaling packets first
556             break;
557 
558         case HCI_EVENT_COMMAND_STATUS:
559             l2cap_run();    // try sending signaling packets first
560             break;
561 
562         // handle disconnection complete events
563         case HCI_EVENT_DISCONNECTION_COMPLETE:
564             // send l2cap disconnect events for all channels on this handle
565             handle = READ_BT_16(packet, 3);
566             it = (linked_item_t *) &l2cap_channels;
567             while (it->next){
568                 l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
569                 if ( channel->handle == handle ){
570                     // update prev item before free'ing next element - don't call l2cap_finalize_channel_close
571                     it->next = it->next->next;
572                     l2cap_emit_channel_closed(channel);
573                     btstack_memory_l2cap_channel_free(channel);
574                 } else {
575                     it = it->next;
576                 }
577             }
578             break;
579 
580         case HCI_EVENT_NUMBER_OF_COMPLETED_PACKETS:
581             l2cap_run();    // try sending signaling packets first
582             l2cap_hand_out_credits();
583             break;
584 
585         // HCI Connection Timeouts
586         case L2CAP_EVENT_TIMEOUT_CHECK:
587             handle = READ_BT_16(packet, 2);
588             if (hci_authentication_active_for_handle(handle)) break;
589             hci_con_used = 0;
590             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
591                 channel = (l2cap_channel_t *) it;
592                 if (channel->handle == handle) {
593                     hci_con_used = 1;
594                 }
595             }
596             if (hci_con_used) break;
597             if (!hci_can_send_packet_now(HCI_COMMAND_DATA_PACKET)) break;
598             hci_send_cmd(&hci_disconnect, handle, 0x13); // remote closed connection
599             break;
600 
601         case DAEMON_EVENT_HCI_PACKET_SENT:
602             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
603                 channel = (l2cap_channel_t *) it;
604                 if (channel->packet_handler) {
605                     (* (channel->packet_handler))(HCI_EVENT_PACKET, channel->local_cid, packet, size);
606                 }
607             }
608             break;
609 
610         default:
611             break;
612     }
613 
614     // pass on
615     (*packet_handler)(NULL, HCI_EVENT_PACKET, 0, packet, size);
616 }
617 
618 static void l2cap_handle_disconnect_request(l2cap_channel_t *channel, uint16_t identifier){
619     channel->remote_sig_id = identifier;
620     channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE;
621     l2cap_run();
622 }
623 
624 static void l2cap_register_signaling_response(hci_con_handle_t handle, uint8_t code, uint8_t sig_id, uint16_t data){
625     if (signaling_responses_pending < NR_PENDING_SIGNALING_RESPONSES) {
626         signaling_responses[signaling_responses_pending].handle = handle;
627         signaling_responses[signaling_responses_pending].code = code;
628         signaling_responses[signaling_responses_pending].sig_id = sig_id;
629         signaling_responses[signaling_responses_pending].data = data;
630         signaling_responses_pending++;
631         l2cap_run();
632     }
633 }
634 
635 static void l2cap_handle_connection_request(hci_con_handle_t handle, uint8_t sig_id, uint16_t psm, uint16_t source_cid){
636 
637     // log_info("l2cap_handle_connection_request for handle %u, psm %u cid %u\n", handle, psm, source_cid);
638     l2cap_service_t *service = l2cap_get_service(psm);
639     if (!service) {
640         // 0x0002 PSM not supported
641         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0002);
642         return;
643     }
644 
645     hci_connection_t * hci_connection = connection_for_handle( handle );
646     if (!hci_connection) {
647         //
648         log_error("no hci_connection for handle %u\n", handle);
649         return;
650     }
651     // alloc structure
652     // log_info("l2cap_handle_connection_request register channel\n");
653     l2cap_channel_t * channel = (l2cap_channel_t*) btstack_memory_l2cap_channel_get();
654     if (!channel){
655         // 0x0004 No resources available
656         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0004);
657         return;
658     }
659 
660     // fill in
661     BD_ADDR_COPY(channel->address, hci_connection->address);
662     channel->psm = psm;
663     channel->handle = handle;
664     channel->connection = service->connection;
665     channel->packet_handler = service->packet_handler;
666     channel->local_cid  = l2cap_next_local_cid();
667     channel->remote_cid = source_cid;
668     channel->local_mtu  = service->mtu;
669     channel->remote_mtu = L2CAP_DEFAULT_MTU;
670     channel->packets_granted = 0;
671     channel->remote_sig_id = sig_id;
672 
673     // limit local mtu to max acl packet length
674     if (channel->local_mtu > l2cap_max_mtu()) {
675         channel->local_mtu = l2cap_max_mtu();
676     }
677 
678     // set initial state
679     channel->state = L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT;
680     channel->state_var = L2CAP_CHANNEL_STATE_VAR_NONE;
681 
682     // add to connections list
683     linked_list_add(&l2cap_channels, (linked_item_t *) channel);
684 
685     // emit incoming connection request
686     l2cap_emit_connection_request(channel);
687 }
688 
689 void l2cap_accept_connection_internal(uint16_t local_cid){
690     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
691     if (!channel) {
692         log_error("l2cap_accept_connection_internal called but local_cid 0x%x not found", local_cid);
693         return;
694     }
695 
696     channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT;
697 
698     // process
699     l2cap_run();
700 }
701 
702 void l2cap_decline_connection_internal(uint16_t local_cid, uint8_t reason){
703     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid( local_cid);
704     if (!channel) {
705         log_error( "l2cap_decline_connection_internal called but local_cid 0x%x not found", local_cid);
706         return;
707     }
708     channel->state  = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE;
709     channel->reason = reason;
710     l2cap_run();
711 }
712 
713 void l2cap_signaling_handle_configure_request(l2cap_channel_t *channel, uint8_t *command){
714 
715     channel->remote_sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
716 
717     // accept the other's configuration options
718     uint16_t end_pos = 4 + READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
719     uint16_t pos     = 8;
720     while (pos < end_pos){
721         uint8_t type   = command[pos++];
722         uint8_t length = command[pos++];
723         // MTU { type(8): 1, len(8):2, MTU(16) }
724         if ((type & 0x7f) == 1 && length == 2){
725             channel->remote_mtu = READ_BT_16(command, pos);
726             // log_info("l2cap cid %u, remote mtu %u\n", channel->local_cid, channel->remote_mtu);
727         }
728         pos += length;
729     }
730 }
731 
732 static int l2cap_channel_ready_for_open(l2cap_channel_t *channel){
733     // log_info("l2cap_channel_ready_for_open 0x%02x\n", channel->state_var);
734     if ((channel->state_var & L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_RSP) == 0) return 0;
735     if ((channel->state_var & L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP) == 0) return 0;
736     return 1;
737 }
738 
739 
740 void l2cap_signaling_handler_channel(l2cap_channel_t *channel, uint8_t *command){
741 
742     uint8_t  code       = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
743     uint8_t  identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
744     uint16_t result = 0;
745 
746     log_info("L2CAP signaling handler code %u, state %u\n", code, channel->state);
747 
748     // handle DISCONNECT REQUESTS seperately
749     if (code == DISCONNECTION_REQUEST){
750         switch (channel->state){
751             case L2CAP_STATE_CONFIG:
752             case L2CAP_STATE_OPEN:
753             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
754             case L2CAP_STATE_WAIT_DISCONNECT:
755                 l2cap_handle_disconnect_request(channel, identifier);
756                 break;
757 
758             default:
759                 // ignore in other states
760                 break;
761         }
762         return;
763     }
764 
765     // @STATEMACHINE(l2cap)
766     switch (channel->state) {
767 
768         case L2CAP_STATE_WAIT_CONNECT_RSP:
769             switch (code){
770                 case CONNECTION_RESPONSE:
771                     result = READ_BT_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
772                     switch (result) {
773                         case 0:
774                             // successful connection
775                             channel->remote_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
776                             channel->state = L2CAP_STATE_CONFIG;
777                             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
778                             break;
779                         case 1:
780                             // connection pending. get some coffee
781                             break;
782                         default:
783                             // channel closed
784                             channel->state = L2CAP_STATE_CLOSED;
785 
786                             // map l2cap connection response result to BTstack status enumeration
787                             l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result);
788 
789                             // drop link key if security block
790                             if (L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result == L2CAP_CONNECTION_RESPONSE_RESULT_REFUSED_SECURITY){
791                                 hci_drop_link_key_for_bd_addr(&channel->address);
792                             }
793 
794                             // discard channel
795                             linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
796                             btstack_memory_l2cap_channel_free(channel);
797                             break;
798                     }
799                     break;
800 
801                 default:
802                     //@TODO: implement other signaling packets
803                     break;
804             }
805             break;
806 
807         case L2CAP_STATE_CONFIG:
808             switch (code) {
809                 case CONFIGURE_REQUEST:
810                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_REQ);
811                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP);
812                     l2cap_signaling_handle_configure_request(channel, command);
813                     break;
814                 case CONFIGURE_RESPONSE:
815                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_RSP);
816                     break;
817                 default:
818                     break;
819             }
820             if (l2cap_channel_ready_for_open(channel)){
821                 // for open:
822                 channel->state = L2CAP_STATE_OPEN;
823                 l2cap_emit_channel_opened(channel, 0);
824                 l2cap_emit_credits(channel, 1);
825             }
826             break;
827 
828         case L2CAP_STATE_WAIT_DISCONNECT:
829             switch (code) {
830                 case DISCONNECTION_RESPONSE:
831                     l2cap_finialize_channel_close(channel);
832                     break;
833                 default:
834                     //@TODO: implement other signaling packets
835                     break;
836             }
837             break;
838 
839         case L2CAP_STATE_CLOSED:
840             // @TODO handle incoming requests
841             break;
842 
843         case L2CAP_STATE_OPEN:
844             //@TODO: implement other signaling packets, e.g. re-configure
845             break;
846         default:
847             break;
848     }
849     // log_info("new state %u\n", channel->state);
850 }
851 
852 
853 void l2cap_signaling_handler_dispatch( hci_con_handle_t handle, uint8_t * command){
854 
855     // get code, signalind identifier and command len
856     uint8_t code   = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
857     uint8_t sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
858 
859     // not for a particular channel, and not CONNECTION_REQUEST, ECHO_[REQUEST|RESPONSE], INFORMATION_REQUEST
860     if (code < 1 || code == ECHO_RESPONSE || code > INFORMATION_REQUEST){
861         return;
862     }
863 
864     // general commands without an assigned channel
865     switch(code) {
866 
867         case CONNECTION_REQUEST: {
868             uint16_t psm =        READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
869             uint16_t source_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+2);
870             l2cap_handle_connection_request(handle, sig_id, psm, source_cid);
871             return;
872         }
873 
874         case ECHO_REQUEST:
875             l2cap_register_signaling_response(handle, code, sig_id, 0);
876             return;
877 
878         case INFORMATION_REQUEST: {
879             uint16_t infoType = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
880             l2cap_register_signaling_response(handle, code, sig_id, infoType);
881             return;
882         }
883 
884         default:
885             break;
886     }
887 
888 
889     // Get potential destination CID
890     uint16_t dest_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
891 
892     // Find channel for this sig_id and connection handle
893     linked_item_t *it;
894     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
895         l2cap_channel_t * channel = (l2cap_channel_t *) it;
896         if (channel->handle == handle) {
897             if (code & 1) {
898                 // match odd commands (responses) by previous signaling identifier
899                 if (channel->local_sig_id == sig_id) {
900                     l2cap_signaling_handler_channel(channel, command);
901                     break;
902                 }
903             } else {
904                 // match even commands (requests) by local channel id
905                 if (channel->local_cid == dest_cid) {
906                     l2cap_signaling_handler_channel(channel, command);
907                     break;
908                 }
909             }
910         }
911     }
912 }
913 
914 void l2cap_acl_handler( uint8_t *packet, uint16_t size ){
915 
916     // Get Channel ID
917     uint16_t channel_id = READ_L2CAP_CHANNEL_ID(packet);
918 
919     // Signaling Packet?
920     if (channel_id == 1) {
921 
922         // Get Connection
923         hci_con_handle_t handle = READ_ACL_CONNECTION_HANDLE(packet);
924 
925         uint16_t command_offset = 8;
926         while (command_offset < size) {
927 
928             // handle signaling commands
929             l2cap_signaling_handler_dispatch(handle, &packet[command_offset]);
930 
931             // increment command_offset
932             command_offset += L2CAP_SIGNALING_COMMAND_DATA_OFFSET + READ_BT_16(packet, command_offset + L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
933         }
934 
935         l2cap_run();
936 
937         return;
938     }
939 
940     // Find channel for this channel_id and connection handle
941     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(channel_id);
942     if (channel) {
943         l2cap_dispatch(channel, L2CAP_DATA_PACKET, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
944     }
945 }
946 
947 static void l2cap_packet_handler(uint8_t packet_type, uint8_t *packet, uint16_t size){
948     switch (packet_type) {
949         case HCI_EVENT_PACKET:
950             l2cap_event_handler(packet, size);
951             break;
952         case HCI_ACL_DATA_PACKET:
953             l2cap_acl_handler(packet, size);
954             break;
955         default:
956             break;
957     }
958 }
959 
960 // finalize closed channel - l2cap_handle_disconnect_request & DISCONNECTION_RESPONSE
961 void l2cap_finialize_channel_close(l2cap_channel_t *channel){
962     channel->state = L2CAP_STATE_CLOSED;
963     l2cap_emit_channel_closed(channel);
964     // discard channel
965     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
966     btstack_memory_l2cap_channel_free(channel);
967 }
968 
969 l2cap_service_t * l2cap_get_service(uint16_t psm){
970     linked_item_t *it;
971 
972     // close open channels
973     for (it = (linked_item_t *) l2cap_services; it ; it = it->next){
974         l2cap_service_t * service = ((l2cap_service_t *) it);
975         if ( service->psm == psm){
976             return service;
977         };
978     }
979     return NULL;
980 }
981 
982 void l2cap_register_service_internal(void *connection, btstack_packet_handler_t packet_handler, uint16_t psm, uint16_t mtu){
983     // check for alread registered psm
984     // TODO: emit error event
985     l2cap_service_t *service = l2cap_get_service(psm);
986     if (service) {
987         log_error("l2cap_register_service_internal: PSM %u already registered\n", psm);
988         l2cap_emit_service_registered(connection, L2CAP_SERVICE_ALREADY_REGISTERED, psm);
989         return;
990     }
991 
992     // alloc structure
993     // TODO: emit error event
994     service = (l2cap_service_t *) btstack_memory_l2cap_service_get();
995     if (!service) {
996         log_error("l2cap_register_service_internal: no memory for l2cap_service_t\n");
997         l2cap_emit_service_registered(connection, BTSTACK_MEMORY_ALLOC_FAILED, psm);
998         return;
999     }
1000 
1001     // fill in
1002     service->psm = psm;
1003     service->mtu = mtu;
1004     service->connection = connection;
1005     service->packet_handler = packet_handler;
1006 
1007     // add to services list
1008     linked_list_add(&l2cap_services, (linked_item_t *) service);
1009 
1010     // enable page scan
1011     hci_connectable_control(1);
1012 
1013     // done
1014     l2cap_emit_service_registered(connection, 0, psm);
1015 }
1016 
1017 void l2cap_unregister_service_internal(void *connection, uint16_t psm){
1018     l2cap_service_t *service = l2cap_get_service(psm);
1019     if (!service) return;
1020     linked_list_remove(&l2cap_services, (linked_item_t *) service);
1021     btstack_memory_l2cap_service_free(service);
1022 
1023     // disable page scan when no services registered
1024     if (!linked_list_empty(&l2cap_services)) return;
1025     hci_connectable_control(0);
1026 }
1027 
1028 //
1029 void l2cap_close_connection(void *connection){
1030     linked_item_t *it;
1031 
1032     // close open channels - note to myself: no channel is freed, so no new for fancy iterator tricks
1033     l2cap_channel_t * channel;
1034     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
1035         channel = (l2cap_channel_t *) it;
1036         if (channel->connection == connection) {
1037             channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST;
1038         }
1039     }
1040 
1041     // unregister services
1042     it = (linked_item_t *) &l2cap_services;
1043     while (it->next) {
1044         l2cap_service_t * service = (l2cap_service_t *) it->next;
1045         if (service->connection == connection){
1046             it->next = it->next->next;
1047             btstack_memory_l2cap_service_free(service);
1048         } else {
1049             it = it->next;
1050         }
1051     }
1052 
1053     // process
1054     l2cap_run();
1055 }
1056