xref: /btstack/src/l2cap.c (revision 4bb582b6c900ce90007a94e26c401226fab6db54)
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 // size of HCI ACL + L2CAP Header for regular data packets
52 #define COMPLETE_L2CAP_HEADER 8
53 
54 // minimum signaling MTU
55 #define L2CAP_MINIMAL_MTU 48
56 #define L2CAP_DEFAULT_MTU 672
57 
58 // nr of buffered acl packets in outgoing queue to get max performance
59 #define NR_BUFFERED_ACL_PACKETS 3
60 
61 // used to cache l2cap rejects, echo, and informational requests
62 #define NR_PENDING_SIGNALING_RESPONSES 5
63 
64 // offsets for L2CAP SIGNALING COMMANDS
65 #define L2CAP_SIGNALING_COMMAND_CODE_OFFSET   0
66 #define L2CAP_SIGNALING_COMMAND_SIGID_OFFSET  1
67 #define L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET 2
68 #define L2CAP_SIGNALING_COMMAND_DATA_OFFSET   4
69 
70 static void null_packet_handler(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size);
71 static void l2cap_packet_handler(uint8_t packet_type, uint8_t *packet, uint16_t size);
72 
73 // used to cache l2cap rejects, echo, and informational requests
74 static l2cap_signaling_response_t signaling_responses[NR_PENDING_SIGNALING_RESPONSES];
75 static int signaling_responses_pending;
76 
77 // static buffers
78 static uint8_t sig_buffer[L2CAP_MINIMAL_MTU];
79 static uint8_t acl_buffer[HCI_ACL_3DH5_SIZE];
80 
81 static linked_list_t l2cap_channels = NULL;
82 static linked_list_t l2cap_services = NULL;
83 static void (*packet_handler) (void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size) = null_packet_handler;
84 static int new_credits_blocked = 0;
85 
86 // prototypes
87 static void l2cap_finialize_channel_close(l2cap_channel_t *channel);
88 static l2cap_service_t * l2cap_get_service(uint16_t psm);
89 static void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status);
90 static void l2cap_emit_channel_closed(l2cap_channel_t *channel);
91 static void l2cap_emit_connection_request(l2cap_channel_t *channel);
92 static int l2cap_channel_ready_for_open(l2cap_channel_t *channel);
93 
94 
95 void l2cap_init(){
96 
97     new_credits_blocked = 0;
98     signaling_responses_pending = 0;
99 
100     //
101     // register callback with HCI
102     //
103     hci_register_packet_handler(&l2cap_packet_handler);
104 }
105 
106 
107 /** Register L2CAP packet handlers */
108 static void null_packet_handler(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
109 }
110 void l2cap_register_packet_handler(void (*handler)(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size)){
111     packet_handler = handler;
112 }
113 
114 //  notify client/protocol handler
115 void l2cap_dispatch(l2cap_channel_t *channel, uint8_t type, uint8_t * data, uint16_t size){
116     if (channel->packet_handler) {
117         (* (channel->packet_handler))(type, channel->local_cid, data, size);
118     } else {
119         (*packet_handler)(channel->connection, type, channel->local_cid, data, size);
120     }
121 }
122 
123 void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status) {
124     uint8_t event[21];
125     event[0] = L2CAP_EVENT_CHANNEL_OPENED;
126     event[1] = sizeof(event) - 2;
127     event[2] = status;
128     bt_flip_addr(&event[3], channel->address);
129     bt_store_16(event,  9, channel->handle);
130     bt_store_16(event, 11, channel->psm);
131     bt_store_16(event, 13, channel->local_cid);
132     bt_store_16(event, 15, channel->remote_cid);
133     bt_store_16(event, 17, channel->local_mtu);
134     bt_store_16(event, 19, channel->remote_mtu);
135     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
136     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
137 }
138 
139 void l2cap_emit_channel_closed(l2cap_channel_t *channel) {
140     uint8_t event[4];
141     event[0] = L2CAP_EVENT_CHANNEL_CLOSED;
142     event[1] = sizeof(event) - 2;
143     bt_store_16(event, 2, channel->local_cid);
144     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
145     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
146 }
147 
148 void l2cap_emit_connection_request(l2cap_channel_t *channel) {
149     uint8_t event[16];
150     event[0] = L2CAP_EVENT_INCOMING_CONNECTION;
151     event[1] = sizeof(event) - 2;
152     bt_flip_addr(&event[2], channel->address);
153     bt_store_16(event,  8, channel->handle);
154     bt_store_16(event, 10, channel->psm);
155     bt_store_16(event, 12, channel->local_cid);
156     bt_store_16(event, 14, channel->remote_cid);
157     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
158     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
159 }
160 
161 void l2cap_emit_credits(l2cap_channel_t *channel, uint8_t credits) {
162     // track credits
163     channel->packets_granted += credits;
164     // log_info("l2cap_emit_credits for cid %u, credits given: %u (+%u)\n", channel->local_cid, channel->packets_granted, credits);
165 
166     uint8_t event[5];
167     event[0] = L2CAP_EVENT_CREDITS;
168     event[1] = sizeof(event) - 2;
169     bt_store_16(event, 2, channel->local_cid);
170     event[4] = credits;
171     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
172     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
173 }
174 
175 void l2cap_block_new_credits(uint8_t blocked){
176     new_credits_blocked = blocked;
177 }
178 
179 void l2cap_hand_out_credits(void){
180 
181     if (new_credits_blocked) return;    // we're told not to. used by daemon
182 
183     linked_item_t *it;
184     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
185         if (!hci_number_free_acl_slots()) return;
186         l2cap_channel_t * channel = (l2cap_channel_t *) it;
187         if (channel->state != L2CAP_STATE_OPEN) continue;
188         if (hci_number_outgoing_packets(channel->handle) < NR_BUFFERED_ACL_PACKETS && channel->packets_granted == 0) {
189             l2cap_emit_credits(channel, 1);
190         }
191     }
192 }
193 
194 l2cap_channel_t * l2cap_get_channel_for_local_cid(uint16_t local_cid){
195     linked_item_t *it;
196     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
197         l2cap_channel_t * channel = (l2cap_channel_t *) it;
198         if ( channel->local_cid == local_cid) {
199             return channel;
200         }
201     }
202     return NULL;
203 }
204 
205 int  l2cap_can_send_packet_now(uint16_t local_cid){
206     l2cap_channel_t *channel = l2cap_get_channel_for_local_cid(local_cid);
207     if (!channel) return 0;
208     if (!channel->packets_granted) return 0;
209     return hci_can_send_packet_now(HCI_ACL_DATA_PACKET);
210 }
211 
212 uint16_t l2cap_get_remote_mtu_for_local_cid(uint16_t local_cid){
213     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
214     if (channel) {
215         return channel->remote_mtu;
216     }
217     return 0;
218 }
219 
220 int l2cap_send_signaling_packet(hci_con_handle_t handle, L2CAP_SIGNALING_COMMANDS cmd, uint8_t identifier, ...){
221     // log_info("l2cap_send_signaling_packet type %u\n", cmd);
222     va_list argptr;
223     va_start(argptr, identifier);
224     uint16_t len = l2cap_create_signaling_internal(sig_buffer, handle, cmd, identifier, argptr);
225     va_end(argptr);
226     // log_info("l2cap_send_signaling_packet con %u!\n", handle);
227     return hci_send_acl_packet(sig_buffer, len);
228 }
229 
230 int l2cap_send_internal(uint16_t local_cid, uint8_t *data, uint16_t len){
231 
232     // check for free places on BT module
233     if (!hci_number_free_acl_slots()) {
234         log_info("l2cap_send_internal cid %u, BT module full <-----\n", local_cid);
235         return BTSTACK_ACL_BUFFERS_FULL;
236     }
237     int err = 0;
238 
239     // find channel for local_cid, construct l2cap packet and send
240     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
241     if (channel) {
242         if (channel->packets_granted > 0){
243             --channel->packets_granted;
244             // log_info("l2cap_send_internal cid %u, handle %u, 1 credit used, credits left %u;\n",
245             //        local_cid, channel->handle, channel->packets_granted);
246         } else {
247             log_error("l2cap_send_internal cid %u, no credits!\n", local_cid);
248         }
249 
250         // 0 - Connection handle : PB=10 : BC=00
251         bt_store_16(acl_buffer, 0, channel->handle | (2 << 12) | (0 << 14));
252         // 2 - ACL length
253         bt_store_16(acl_buffer, 2,  len + 4);
254         // 4 - L2CAP packet length
255         bt_store_16(acl_buffer, 4,  len + 0);
256         // 6 - L2CAP channel DEST
257         bt_store_16(acl_buffer, 6, channel->remote_cid);
258         // 8 - data
259         memcpy(&acl_buffer[8], data, len);
260 
261         // send
262         err = hci_send_acl_packet(acl_buffer, len+8);
263     }
264 
265     l2cap_hand_out_credits();
266 
267     return err;
268 }
269 
270 // MARK: L2CAP_RUN
271 // process outstanding signaling tasks
272 void l2cap_run(void){
273 
274     // check pending signaling responses
275     while (signaling_responses_pending){
276 
277         if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)) break;
278 
279         hci_con_handle_t handle = signaling_responses[0].handle;
280         uint8_t sig_id = signaling_responses[0].sig_id;
281         uint16_t infoType = signaling_responses[0].data;    // INFORMATION_REQUEST
282         uint16_t result   = signaling_responses[0].data;    // CONNECTION_REQUEST
283 
284         switch (signaling_responses[0].code){
285             case CONNECTION_REQUEST:
286                 l2cap_send_signaling_packet(handle, CONNECTION_RESPONSE, sig_id, 0, 0, result, 0);
287                 break;
288             case ECHO_REQUEST:
289                 l2cap_send_signaling_packet(handle, ECHO_RESPONSE, sig_id, 0, NULL);
290                 break;
291             case INFORMATION_REQUEST:
292                 if (infoType == 2) {
293                     uint32_t features = 0;
294                     // extended features request supported, however no features present
295                     l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, 4, &features);
296                 } else {
297                     // all other types are not supported
298                     l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 1, 0, NULL);
299                 }
300                 break;
301             default:
302                 // should not happen
303                 break;
304         }
305 
306         // remove first item
307         signaling_responses_pending--;
308         int i;
309         for (i=0; i < signaling_responses_pending; i++){
310             signaling_responses[i] = signaling_responses[i+1];
311         }
312     }
313 
314     uint8_t  config_options[4];
315     linked_item_t *it;
316     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
317 
318         if (!hci_can_send_packet_now(HCI_COMMAND_DATA_PACKET)) break;
319         if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)) break;
320 
321         l2cap_channel_t * channel = (l2cap_channel_t *) it;
322 
323         // log_info("l2cap_run: state %u, var 0x%02x\n", channel->state, channel->state_var);
324 
325         switch (channel->state){
326 
327             case L2CAP_STATE_WILL_SEND_CREATE_CONNECTION:
328                 // send connection request - set state first
329                 channel->state = L2CAP_STATE_WAIT_CONNECTION_COMPLETE;
330                 // BD_ADDR, Packet_Type, Page_Scan_Repetition_Mode, Reserved, Clock_Offset, Allow_Role_Switch
331                 hci_send_cmd(&hci_create_connection, channel->address, 0xcc18, 0, 0, 0, 1);
332                 break;
333 
334             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE:
335                 l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, 0, 0, channel->reason, 0);
336                 // discard channel - l2cap_finialize_channel_close without sending l2cap close event
337                 linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
338                 btstack_memory_l2cap_channel_free(channel);
339                 break;
340 
341             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT:
342                 channel->state = L2CAP_STATE_CONFIG;
343                 channel->state_var |= L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ;
344                 l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid, 0, 0);
345                 break;
346 
347             case L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST:
348                 // success, start l2cap handshake
349                 channel->local_sig_id = l2cap_next_sig_id();
350                 channel->state = L2CAP_STATE_WAIT_CONNECT_RSP;
351                 l2cap_send_signaling_packet( channel->handle, CONNECTION_REQUEST, channel->local_sig_id, channel->psm, channel->local_cid);
352                 break;
353 
354             case L2CAP_STATE_CONFIG:
355                 if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP){
356                     channel->state_var &= ~L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP;
357                     channel->state_var |= L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP;
358                     l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, 0, 0, 0, NULL);
359                 }
360                 else if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ){
361                     channel->state_var &= ~L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ;
362                     channel->state_var |= L2CAP_CHANNEL_STATE_VAR_SENT_CONF_REQ;
363                     channel->local_sig_id = l2cap_next_sig_id();
364                     config_options[0] = 1; // MTU
365                     config_options[1] = 2; // len param
366                     bt_store_16( (uint8_t*)&config_options, 2, channel->local_mtu);
367                     l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->local_sig_id, channel->remote_cid, 0, 4, &config_options);
368                 }
369                 if (l2cap_channel_ready_for_open(channel)){
370                     channel->state = L2CAP_STATE_OPEN;
371                     l2cap_emit_channel_opened(channel, 0);  // success
372                     l2cap_emit_credits(channel, 1);
373                 }
374                 break;
375 
376             case L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE:
377                 l2cap_send_signaling_packet( channel->handle, DISCONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid);
378                 l2cap_finialize_channel_close(channel);
379                 break;
380 
381             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
382                 channel->local_sig_id = l2cap_next_sig_id();
383                 channel->state = L2CAP_STATE_WAIT_DISCONNECT;
384                 l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->local_sig_id, channel->remote_cid, channel->local_cid);
385                 break;
386             default:
387                 break;
388         }
389     }
390 }
391 
392 static uint16_t l2cap_max_l2cap_mtu(void){
393     return hci_max_acl_data_packet_length()-4;  // 4 bytes for L2CAP header
394 }
395 
396 // open outgoing L2CAP channel
397 void l2cap_create_channel_internal(void * connection, btstack_packet_handler_t packet_handler,
398                                    bd_addr_t address, uint16_t psm, uint16_t mtu){
399 
400     // alloc structure
401     l2cap_channel_t * chan = btstack_memory_l2cap_channel_get();
402     if (!chan) {
403         // emit error event
404         l2cap_channel_t dummy_channel;
405         BD_ADDR_COPY(dummy_channel.address, address);
406         dummy_channel.psm = psm;
407         l2cap_emit_channel_opened(&dummy_channel, BTSTACK_MEMORY_ALLOC_FAILED);
408         return;
409     }
410     // limit local mtu to max acl packet length
411     if (mtu > l2cap_max_l2cap_mtu()) {
412         mtu = l2cap_max_l2cap_mtu();
413     }
414 
415     // fill in
416     BD_ADDR_COPY(chan->address, address);
417     chan->psm = psm;
418     chan->handle = 0;
419     chan->connection = connection;
420     chan->packet_handler = packet_handler;
421     chan->remote_mtu = L2CAP_MINIMAL_MTU;
422     chan->local_mtu = mtu;
423     chan->packets_granted = 0;
424 
425     // set initial state
426     chan->state = L2CAP_STATE_WILL_SEND_CREATE_CONNECTION;
427     chan->state_var = L2CAP_CHANNEL_STATE_VAR_NONE;
428     chan->remote_sig_id = L2CAP_SIG_ID_INVALID;
429     chan->local_sig_id = L2CAP_SIG_ID_INVALID;
430 
431     // add to connections list
432     linked_list_add(&l2cap_channels, (linked_item_t *) chan);
433 
434     l2cap_run();
435 }
436 
437 void l2cap_disconnect_internal(uint16_t local_cid, uint8_t reason){
438     // find channel for local_cid
439     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
440     if (channel) {
441         channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST;
442     }
443     // process
444     l2cap_run();
445 }
446 
447 static void l2cap_handle_connection_failed_for_addr(bd_addr_t address, uint8_t status){
448     linked_item_t *it = (linked_item_t *) &l2cap_channels;
449     while (it->next){
450         l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
451         if ( ! BD_ADDR_CMP( channel->address, address) ){
452             if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
453                 // failure, forward error code
454                 l2cap_emit_channel_opened(channel, status);
455                 // discard channel
456                 it->next = it->next->next;
457                 btstack_memory_l2cap_channel_free(channel);
458             }
459         } else {
460             it = it->next;
461         }
462     }
463 }
464 
465 static void l2cap_handle_connection_success_for_addr(bd_addr_t address, hci_con_handle_t handle){
466     linked_item_t *it;
467     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
468         l2cap_channel_t * channel = (l2cap_channel_t *) it;
469         if ( ! BD_ADDR_CMP( channel->address, address) ){
470             if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
471                 // success, start l2cap handshake
472                 channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST;
473                 channel->handle = handle;
474                 channel->local_cid = l2cap_next_local_cid();
475             }
476         }
477     }
478     // process
479     l2cap_run();
480 }
481 
482 void l2cap_event_handler( uint8_t *packet, uint16_t size ){
483 
484     bd_addr_t address;
485     hci_con_handle_t handle;
486     l2cap_channel_t * channel;
487     linked_item_t *it;
488     int hci_con_used;
489 
490     switch(packet[0]){
491 
492         // handle connection complete events
493         case HCI_EVENT_CONNECTION_COMPLETE:
494             bt_flip_addr(address, &packet[5]);
495             if (packet[2] == 0){
496                 handle = READ_BT_16(packet, 3);
497                 l2cap_handle_connection_success_for_addr(address, handle);
498             } else {
499                 l2cap_handle_connection_failed_for_addr(address, packet[2]);
500             }
501             break;
502 
503         // handle successful create connection cancel command
504         case HCI_EVENT_COMMAND_COMPLETE:
505             if ( COMMAND_COMPLETE_EVENT(packet, hci_create_connection_cancel) ) {
506                 if (packet[5] == 0){
507                     bt_flip_addr(address, &packet[6]);
508                     // CONNECTION TERMINATED BY LOCAL HOST (0X16)
509                     l2cap_handle_connection_failed_for_addr(address, 0x16);
510                 }
511             }
512             l2cap_run();    // try sending signaling packets first
513             break;
514 
515         case HCI_EVENT_COMMAND_STATUS:
516             l2cap_run();    // try sending signaling packets first
517             break;
518 
519         // handle disconnection complete events
520         case HCI_EVENT_DISCONNECTION_COMPLETE:
521             // send l2cap disconnect events for all channels on this handle
522             handle = READ_BT_16(packet, 3);
523             it = (linked_item_t *) &l2cap_channels;
524             while (it->next){
525                 l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
526                 if ( channel->handle == handle ){
527                     // update prev item before free'ing next element - don't call l2cap_finalize_channel_close
528                     it->next = it->next->next;
529                     l2cap_emit_channel_closed(channel);
530                     btstack_memory_l2cap_channel_free(channel);
531                 } else {
532                     it = it->next;
533                 }
534             }
535             break;
536 
537         case HCI_EVENT_NUMBER_OF_COMPLETED_PACKETS:
538             l2cap_run();    // try sending signaling packets first
539             l2cap_hand_out_credits();
540             break;
541 
542         // HCI Connection Timeouts
543         case L2CAP_EVENT_TIMEOUT_CHECK:
544             handle = READ_BT_16(packet, 2);
545             if (hci_authentication_active_for_handle(handle)) break;
546             hci_con_used = 0;
547             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
548                 channel = (l2cap_channel_t *) it;
549                 if (channel->handle == handle) {
550                     hci_con_used = 1;
551                 }
552             }
553             if (hci_con_used) break;
554             if (!hci_can_send_packet_now(HCI_COMMAND_DATA_PACKET)) break;
555             hci_send_cmd(&hci_disconnect, handle, 0x13); // remote closed connection
556             break;
557 
558         case DAEMON_EVENT_HCI_PACKET_SENT:
559             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
560                 channel = (l2cap_channel_t *) it;
561                 if (channel->packet_handler) {
562                     (* (channel->packet_handler))(HCI_EVENT_PACKET, channel->local_cid, packet, size);
563                 }
564             }
565             break;
566 
567         default:
568             break;
569     }
570 
571     // pass on
572     (*packet_handler)(NULL, HCI_EVENT_PACKET, 0, packet, size);
573 }
574 
575 static void l2cap_handle_disconnect_request(l2cap_channel_t *channel, uint16_t identifier){
576     channel->remote_sig_id = identifier;
577     channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE;
578     l2cap_run();
579 }
580 
581 static void l2cap_register_signaling_response(hci_con_handle_t handle, uint8_t code, uint8_t sig_id, uint16_t data){
582     if (signaling_responses_pending < NR_PENDING_SIGNALING_RESPONSES) {
583         signaling_responses[signaling_responses_pending].handle = handle;
584         signaling_responses[signaling_responses_pending].code = code;
585         signaling_responses[signaling_responses_pending].sig_id = sig_id;
586         signaling_responses[signaling_responses_pending].data = data;
587         signaling_responses_pending++;
588         l2cap_run();
589     }
590 }
591 
592 static void l2cap_handle_connection_request(hci_con_handle_t handle, uint8_t sig_id, uint16_t psm, uint16_t source_cid){
593 
594     // log_info("l2cap_handle_connection_request for handle %u, psm %u cid %u\n", handle, psm, source_cid);
595     l2cap_service_t *service = l2cap_get_service(psm);
596     if (!service) {
597         // 0x0002 PSM not supported
598         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0002);
599         return;
600     }
601 
602     hci_connection_t * hci_connection = connection_for_handle( handle );
603     if (!hci_connection) {
604         //
605         log_error("no hci_connection for handle %u\n", handle);
606         return;
607     }
608     // alloc structure
609     // log_info("l2cap_handle_connection_request register channel\n");
610     l2cap_channel_t * channel = btstack_memory_l2cap_channel_get();
611     if (!channel){
612         // 0x0004 No resources available
613         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0004);
614         return;
615     }
616 
617     // fill in
618     BD_ADDR_COPY(channel->address, hci_connection->address);
619     channel->psm = psm;
620     channel->handle = handle;
621     channel->connection = service->connection;
622     channel->packet_handler = service->packet_handler;
623     channel->local_cid  = l2cap_next_local_cid();
624     channel->remote_cid = source_cid;
625     channel->local_mtu  = service->mtu;
626     channel->remote_mtu = L2CAP_DEFAULT_MTU;
627     channel->packets_granted = 0;
628     channel->remote_sig_id = sig_id;
629 
630     // limit local mtu to max acl packet length
631     if (channel->local_mtu > l2cap_max_l2cap_mtu()) {
632         channel->local_mtu = l2cap_max_l2cap_mtu();
633     }
634 
635     // set initial state
636     channel->state = L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT;
637     channel->state_var = L2CAP_CHANNEL_STATE_VAR_NONE;
638 
639     // add to connections list
640     linked_list_add(&l2cap_channels, (linked_item_t *) channel);
641 
642     // emit incoming connection request
643     l2cap_emit_connection_request(channel);
644 }
645 
646 void l2cap_accept_connection_internal(uint16_t local_cid){
647     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
648     if (!channel) {
649         log_error("l2cap_accept_connection_internal called but local_cid 0x%x not found", local_cid);
650         return;
651     }
652 
653     channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT;
654 
655     // process
656     l2cap_run();
657 }
658 
659 void l2cap_decline_connection_internal(uint16_t local_cid, uint8_t reason){
660     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid( local_cid);
661     if (!channel) {
662         log_error( "l2cap_decline_connection_internal called but local_cid 0x%x not found", local_cid);
663         return;
664     }
665     channel->state  = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE;
666     channel->reason = reason;
667     l2cap_run();
668 }
669 
670 void l2cap_signaling_handle_configure_request(l2cap_channel_t *channel, uint8_t *command){
671 
672     channel->remote_sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
673 
674     // accept the other's configuration options
675     uint16_t end_pos = 4 + READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
676     uint16_t pos     = 8;
677     while (pos < end_pos){
678         uint8_t type   = command[pos++];
679         uint8_t length = command[pos++];
680         // MTU { type(8): 1, len(8):2, MTU(16) }
681         if ((type & 0x7f) == 1 && length == 2){
682             channel->remote_mtu = READ_BT_16(command, pos);
683             // log_info("l2cap cid %u, remote mtu %u\n", channel->local_cid, channel->remote_mtu);
684         }
685         pos += length;
686     }
687 }
688 
689 static int l2cap_channel_ready_for_open(l2cap_channel_t *channel){
690     // log_info("l2cap_channel_ready_for_open 0x%02x\n", channel->state_var);
691     if ((channel->state_var & L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_RSP) == 0) return 0;
692     if ((channel->state_var & L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP) == 0) return 0;
693     return 1;
694 }
695 
696 
697 void l2cap_signaling_handler_channel(l2cap_channel_t *channel, uint8_t *command){
698 
699     uint8_t  code       = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
700     uint8_t  identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
701     uint16_t result = 0;
702 
703     log_info("signaling handler code %u, state %u\n", code, channel->state);
704 
705     // handle DISCONNECT REQUESTS seperately
706     if (code == DISCONNECTION_REQUEST){
707         switch (channel->state){
708             case L2CAP_STATE_CONFIG:
709             case L2CAP_STATE_OPEN:
710             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
711             case L2CAP_STATE_WAIT_DISCONNECT:
712                 l2cap_handle_disconnect_request(channel, identifier);
713                 break;
714 
715             default:
716                 // ignore in other states
717                 break;
718         }
719         return;
720     }
721 
722     switch (channel->state) {
723 
724         case L2CAP_STATE_WAIT_CONNECT_RSP:
725             switch (code){
726                 case CONNECTION_RESPONSE:
727                     result = READ_BT_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
728                     switch (result) {
729                         case 0:
730                             // successful connection
731                             channel->remote_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
732                             channel->state = L2CAP_STATE_CONFIG;
733                             channel->state_var |= L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ;
734                             break;
735                         case 1:
736                             // connection pending. get some coffee
737                             break;
738                         default:
739                             // channel closed
740                             channel->state = L2CAP_STATE_CLOSED;
741 
742                             // map l2cap connection response result to BTstack status enumeration
743                             l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result);
744 
745                             // drop link key if security block
746                             if (L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result == L2CAP_CONNECTION_RESPONSE_RESULT_REFUSED_SECURITY){
747                                 hci_drop_link_key_for_bd_addr(&channel->address);
748                             }
749 
750                             // discard channel
751                             linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
752                             btstack_memory_l2cap_channel_free(channel);
753                             break;
754                     }
755                     break;
756 
757                 default:
758                     //@TODO: implement other signaling packets
759                     break;
760             }
761             break;
762 
763         case L2CAP_STATE_CONFIG:
764             switch (code) {
765                 case CONFIGURE_REQUEST:
766                     channel->state_var |= L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_REQ;
767                     channel->state_var |= L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP;
768                     l2cap_signaling_handle_configure_request(channel, command);
769                     break;
770                 case CONFIGURE_RESPONSE:
771                     channel->state_var |= L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_RSP;
772                     break;
773                 default:
774                     break;
775             }
776             if (l2cap_channel_ready_for_open(channel)){
777                 // for open:
778                 channel->state = L2CAP_STATE_OPEN;
779                 l2cap_emit_channel_opened(channel, 0);
780                 l2cap_emit_credits(channel, 1);
781             }
782             break;
783 
784         case L2CAP_STATE_WAIT_DISCONNECT:
785             switch (code) {
786                 case DISCONNECTION_RESPONSE:
787                     l2cap_finialize_channel_close(channel);
788                     break;
789                 default:
790                     //@TODO: implement other signaling packets
791                     break;
792             }
793             break;
794 
795         case L2CAP_STATE_CLOSED:
796             // @TODO handle incoming requests
797             break;
798 
799         case L2CAP_STATE_OPEN:
800             //@TODO: implement other signaling packets, e.g. re-configure
801             break;
802         default:
803             break;
804     }
805     // log_info("new state %u\n", channel->state);
806 }
807 
808 
809 void l2cap_signaling_handler_dispatch( hci_con_handle_t handle, uint8_t * command){
810 
811     // get code, signalind identifier and command len
812     uint8_t code   = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
813     uint8_t sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
814 
815     // not for a particular channel, and not CONNECTION_REQUEST, ECHO_[REQUEST|RESPONSE], INFORMATION_REQUEST
816     if (code < 1 || code == ECHO_RESPONSE || code > INFORMATION_REQUEST){
817         return;
818     }
819 
820     // general commands without an assigned channel
821     switch(code) {
822 
823         case CONNECTION_REQUEST: {
824             uint16_t psm =        READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
825             uint16_t source_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+2);
826             l2cap_handle_connection_request(handle, sig_id, psm, source_cid);
827             return;
828         }
829 
830         case ECHO_REQUEST:
831             l2cap_register_signaling_response(handle, code, sig_id, 0);
832             return;
833 
834         case INFORMATION_REQUEST: {
835             uint16_t infoType = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
836             l2cap_register_signaling_response(handle, code, sig_id, infoType);
837             return;
838         }
839 
840         default:
841             break;
842     }
843 
844 
845     // Get potential destination CID
846     uint16_t dest_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
847 
848     // Find channel for this sig_id and connection handle
849     linked_item_t *it;
850     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
851         l2cap_channel_t * channel = (l2cap_channel_t *) it;
852         if (channel->handle == handle) {
853             if (code & 1) {
854                 // match odd commands (responses) by previous signaling identifier
855                 if (channel->local_sig_id == sig_id) {
856                     l2cap_signaling_handler_channel(channel, command);
857                     break;
858                 }
859             } else {
860                 // match even commands (requests) by local channel id
861                 if (channel->local_cid == dest_cid) {
862                     l2cap_signaling_handler_channel(channel, command);
863                     break;
864                 }
865             }
866         }
867     }
868 }
869 
870 void l2cap_acl_handler( uint8_t *packet, uint16_t size ){
871 
872     // Get Channel ID
873     uint16_t channel_id = READ_L2CAP_CHANNEL_ID(packet);
874 
875     // Signaling Packet?
876     if (channel_id == 1) {
877 
878         // Get Connection
879         hci_con_handle_t handle = READ_ACL_CONNECTION_HANDLE(packet);
880 
881         uint16_t command_offset = 8;
882         while (command_offset < size) {
883 
884             // handle signaling commands
885             l2cap_signaling_handler_dispatch(handle, &packet[command_offset]);
886 
887             // increment command_offset
888             command_offset += L2CAP_SIGNALING_COMMAND_DATA_OFFSET + READ_BT_16(packet, command_offset + L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
889         }
890 
891         l2cap_run();
892 
893         return;
894     }
895 
896     // Find channel for this channel_id and connection handle
897     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(channel_id);
898     if (channel) {
899         l2cap_dispatch(channel, L2CAP_DATA_PACKET, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
900     }
901 }
902 
903 static void l2cap_packet_handler(uint8_t packet_type, uint8_t *packet, uint16_t size){
904     switch (packet_type) {
905         case HCI_EVENT_PACKET:
906             l2cap_event_handler(packet, size);
907             break;
908         case HCI_ACL_DATA_PACKET:
909             l2cap_acl_handler(packet, size);
910             break;
911         default:
912             break;
913     }
914 }
915 
916 // finalize closed channel - l2cap_handle_disconnect_request & DISCONNECTION_RESPONSE
917 void l2cap_finialize_channel_close(l2cap_channel_t *channel){
918     channel->state = L2CAP_STATE_CLOSED;
919     l2cap_emit_channel_closed(channel);
920     // discard channel
921     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
922     btstack_memory_l2cap_channel_free(channel);
923 }
924 
925 l2cap_service_t * l2cap_get_service(uint16_t psm){
926     linked_item_t *it;
927 
928     // close open channels
929     for (it = (linked_item_t *) l2cap_services; it ; it = it->next){
930         l2cap_service_t * service = ((l2cap_service_t *) it);
931         if ( service->psm == psm){
932             return service;
933         };
934     }
935     return NULL;
936 }
937 
938 void l2cap_register_service_internal(void *connection, btstack_packet_handler_t packet_handler, uint16_t psm, uint16_t mtu){
939     // check for alread registered psm
940     // TODO: emit error event
941     l2cap_service_t *service = l2cap_get_service(psm);
942     if (service) {
943         log_error("l2cap_register_service_internal: PSM %u already registered\n", psm);
944         return;
945     }
946 
947     // alloc structure
948     // TODO: emit error event
949     service = btstack_memory_l2cap_service_get();
950     if (!service) {
951         log_error("l2cap_register_service_internal: no memory for l2cap_service_t\n");
952         return;
953     }
954 
955     // fill in
956     service->psm = psm;
957     service->mtu = mtu;
958     service->connection = connection;
959     service->packet_handler = packet_handler;
960 
961     // add to services list
962     linked_list_add(&l2cap_services, (linked_item_t *) service);
963 }
964 
965 void l2cap_unregister_service_internal(void *connection, uint16_t psm){
966     l2cap_service_t *service = l2cap_get_service(psm);
967     if (!service) return;
968     linked_list_remove(&l2cap_services, (linked_item_t *) service);
969     btstack_memory_l2cap_service_free(service);
970 }
971 
972 //
973 void l2cap_close_connection(void *connection){
974     linked_item_t *it;
975 
976     // close open channels - note to myself: no channel is freed, so no new for fancy iterator tricks
977     l2cap_channel_t * channel;
978     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
979         channel = (l2cap_channel_t *) it;
980         if (channel->connection == connection) {
981             channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST;
982         }
983     }
984 
985     // unregister services
986     it = (linked_item_t *) &l2cap_services;
987     while (it->next) {
988         l2cap_service_t * service = (l2cap_service_t *) it->next;
989         if (service->connection == connection){
990             it->next = it->next->next;
991             btstack_memory_l2cap_service_free(service);
992         } else {
993             it = it->next;
994         }
995     }
996 
997     // process
998     l2cap_run();
999 }
1000