xref: /btstack/src/l2cap.c (revision 39bda6d5dbeb6c6c8d80a1b09d40c6b7f1272502)
1 /*
2  * Copyright (C) 2009 by Matthias Ringwald
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the copyright holders nor the names of
14  *    contributors may be used to endorse or promote products derived
15  *    from this software without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY MATTHIAS RINGWALD AND CONTRIBUTORS
18  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
19  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
20  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
21  * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
23  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
24  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
25  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
26  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
27  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28  * SUCH DAMAGE.
29  *
30  */
31 
32 /*
33  *  l2cap.c
34  *
35  *  Logical Link Control and Adaption Protocl (L2CAP)
36  *
37  *  Created by Matthias Ringwald on 5/16/09.
38  */
39 
40 #include "l2cap.h"
41 #include "hci.h"
42 #include "hci_dump.h"
43 #include "debug.h"
44 
45 #include <stdarg.h>
46 #include <string.h>
47 
48 #include <stdio.h>
49 
50 // size of HCI ACL + L2CAP Header for regular data packets
51 #define COMPLETE_L2CAP_HEADER 8
52 
53 // minimum signaling MTU
54 #define L2CAP_MINIMAL_MTU 48
55 #define L2CAP_DEFAULT_MTU 672
56 
57 // nr of buffered acl packets in outgoing queue to get max performance
58 #define NR_BUFFERED_ACL_PACKETS 3
59 
60 // used to cache l2cap rejects, echo, and informational requests
61 #define NR_PENDING_SIGNALING_RESPONSES 10
62 
63 // offsets for L2CAP SIGNALING COMMANDS
64 #define L2CAP_SIGNALING_COMMAND_CODE_OFFSET   0
65 #define L2CAP_SIGNALING_COMMAND_SIGID_OFFSET  1
66 #define L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET 2
67 #define L2CAP_SIGNALING_COMMAND_DATA_OFFSET   4
68 
69 typedef enum {
70     L2CAP_STATE_CLOSED = 1,           // no baseband
71     L2CAP_STATE_WILL_SEND_CREATE_CONNECTION,
72     L2CAP_STATE_WAIT_CONNECTION_COMPLETE,
73     L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT,
74     L2CAP_STATE_WAIT_CONNECT_RSP, // from peer
75     L2CAP_STATE_WAIT_CONFIG_REQ_OR_SEND_CONFIG_REQ,
76     L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ,
77     L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_WILL_SEND_CONFIG_REQ_RSP,
78     L2CAP_STATE_WAIT_CONFIG_REQ_RSP,
79     L2CAP_STATE_WAIT_CONFIG_REQ,
80     L2CAP_STATE_OPEN,
81     L2CAP_STATE_WAIT_DISCONNECT,  // from application
82     L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST,
83     L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE,
84     L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT,
85     L2CAP_STATE_WILL_SEND_CONFIG_REQ,
86     L2CAP_STATE_WILL_SEND_CONFIG_REQ_RSP,
87     L2CAP_STATE_WILL_SEND_CONFIG_REQ_AND_CONFIG_REQ_RSP,
88     L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST,
89     L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE,
90 } L2CAP_STATE;
91 
92 // info regarding an actual coneection
93 typedef struct {
94     // linked list - assert: first field
95     linked_item_t    item;
96 
97     L2CAP_STATE state;
98 
99     bd_addr_t address;
100     hci_con_handle_t handle;
101 
102     uint8_t   remote_sig_id;    // used by other side, needed for delayed response
103     uint8_t   local_sig_id;     // own signaling identifier
104 
105     uint16_t  local_cid;
106     uint16_t  remote_cid;
107 
108     uint16_t  local_mtu;
109     uint16_t  remote_mtu;
110 
111     uint16_t  psm;
112 
113     uint8_t   packets_granted;    // number of L2CAP/ACL packets client is allowed to send
114 
115     uint8_t   reason; // used in decline internal
116 
117     // client connection
118     void * connection;
119 
120     // internal connection
121     btstack_packet_handler_t packet_handler;
122 
123 } l2cap_channel_t;
124 
125 // info regarding potential connections
126 typedef struct {
127     // linked list - assert: first field
128     linked_item_t    item;
129 
130     // service id
131     uint16_t  psm;
132 
133     // incoming MTU
134     uint16_t mtu;
135 
136     // client connection
137     void *connection;
138 
139     // internal connection
140     btstack_packet_handler_t packet_handler;
141 
142 } l2cap_service_t;
143 
144 
145 typedef struct l2cap_signaling_response {
146     hci_con_handle_t handle;
147     uint8_t  sig_id;
148     uint8_t  code;
149     uint16_t infoType;
150 } l2cap_signaling_response_t;
151 
152 static void null_packet_handler(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size);
153 static void l2cap_packet_handler(uint8_t packet_type, uint8_t *packet, uint16_t size);
154 
155 // used to cache l2cap rejects, echo, and informational requests
156 static l2cap_signaling_response_t signaling_responses[NR_PENDING_SIGNALING_RESPONSES];
157 static int signaling_responses_pending;
158 
159 static uint8_t * sig_buffer = NULL;
160 static linked_list_t l2cap_channels = NULL;
161 static linked_list_t l2cap_services = NULL;
162 static uint8_t * acl_buffer = NULL;
163 static void (*packet_handler) (void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size) = null_packet_handler;
164 static int new_credits_blocked = 0;
165 
166 
167 // prototypes
168 void l2cap_finialize_channel_close(l2cap_channel_t *channel);
169 l2cap_service_t * l2cap_get_service(uint16_t psm);
170 void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status);
171 void l2cap_emit_channel_closed(l2cap_channel_t *channel);
172 void l2cap_emit_connection_request(l2cap_channel_t *channel);
173 
174 
175 void l2cap_init(){
176     sig_buffer = malloc( L2CAP_MINIMAL_MTU );
177     acl_buffer = malloc( HCI_ACL_3DH5_SIZE);
178 
179     new_credits_blocked = 0;
180     signaling_responses_pending = 0;
181 
182     //
183     // register callback with HCI
184     //
185     hci_register_packet_handler(&l2cap_packet_handler);
186 }
187 
188 
189 /** Register L2CAP packet handlers */
190 static void null_packet_handler(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
191 }
192 void l2cap_register_packet_handler(void (*handler)(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size)){
193     packet_handler = handler;
194 }
195 
196 //  notify client/protocol handler
197 void l2cap_dispatch(l2cap_channel_t *channel, uint8_t type, uint8_t * data, uint16_t size){
198     if (channel->packet_handler) {
199         (* (channel->packet_handler))(type, channel->local_cid, data, size);
200     } else {
201         (*packet_handler)(channel->connection, type, channel->local_cid, data, size);
202     }
203 }
204 
205 void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status) {
206     uint8_t event[21];
207     event[0] = L2CAP_EVENT_CHANNEL_OPENED;
208     event[1] = sizeof(event) - 2;
209     event[2] = status;
210     bt_flip_addr(&event[3], channel->address);
211     bt_store_16(event,  9, channel->handle);
212     bt_store_16(event, 11, channel->psm);
213     bt_store_16(event, 13, channel->local_cid);
214     bt_store_16(event, 15, channel->remote_cid);
215     bt_store_16(event, 17, channel->local_mtu);
216     bt_store_16(event, 19, channel->remote_mtu);
217     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
218     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
219 }
220 
221 void l2cap_emit_channel_closed(l2cap_channel_t *channel) {
222     uint8_t event[4];
223     event[0] = L2CAP_EVENT_CHANNEL_CLOSED;
224     event[1] = sizeof(event) - 2;
225     bt_store_16(event, 2, channel->local_cid);
226     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
227     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
228 }
229 
230 void l2cap_emit_connection_request(l2cap_channel_t *channel) {
231     uint8_t event[16];
232     event[0] = L2CAP_EVENT_INCOMING_CONNECTION;
233     event[1] = sizeof(event) - 2;
234     bt_flip_addr(&event[2], channel->address);
235     bt_store_16(event,  8, channel->handle);
236     bt_store_16(event, 10, channel->psm);
237     bt_store_16(event, 12, channel->local_cid);
238     bt_store_16(event, 14, channel->remote_cid);
239     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
240     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
241 }
242 
243 void l2cap_emit_credits(l2cap_channel_t *channel, uint8_t credits) {
244     // track credits
245     channel->packets_granted += credits;
246     // log_dbg("l2cap_emit_credits for cid %u, credits given: %u (+%u)\n", channel->local_cid, channel->packets_granted, credits);
247 
248     uint8_t event[5];
249     event[0] = L2CAP_EVENT_CREDITS;
250     event[1] = sizeof(event) - 2;
251     bt_store_16(event, 2, channel->local_cid);
252     event[4] = credits;
253     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
254     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
255 }
256 
257 void l2cap_block_new_credits(uint8_t blocked){
258     new_credits_blocked = blocked;
259 }
260 
261 void l2cap_hand_out_credits(void){
262 
263     if (new_credits_blocked) return;    // we're told not to. used by daemon
264 
265     linked_item_t *it;
266     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
267         if (!hci_number_free_acl_slots()) return;
268         l2cap_channel_t * channel = (l2cap_channel_t *) it;
269         if (channel->state != L2CAP_STATE_OPEN) continue;
270         if (hci_number_outgoing_packets(channel->handle) < NR_BUFFERED_ACL_PACKETS && channel->packets_granted == 0) {
271             l2cap_emit_credits(channel, 1);
272         }
273     }
274 }
275 
276 l2cap_channel_t * l2cap_get_channel_for_local_cid(uint16_t local_cid){
277     linked_item_t *it;
278     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
279         l2cap_channel_t * channel = (l2cap_channel_t *) it;
280         if ( channel->local_cid == local_cid) {
281             return channel;
282         }
283     }
284     return NULL;
285 }
286 
287 int  l2cap_can_send_packet_now(uint16_t local_cid){
288     l2cap_channel_t *channel = l2cap_get_channel_for_local_cid(local_cid);
289     if (!channel) return 0;
290     if (!channel->packets_granted) return 0;
291     return hci_can_send_packet_now(HCI_ACL_DATA_PACKET);
292 }
293 
294 uint16_t l2cap_get_remote_mtu_for_local_cid(uint16_t local_cid){
295     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
296     if (channel) {
297         return channel->remote_mtu;
298     }
299     return 0;
300 }
301 
302 int l2cap_send_signaling_packet(hci_con_handle_t handle, L2CAP_SIGNALING_COMMANDS cmd, uint8_t identifier, ...){
303     // log_dbg("l2cap_send_signaling_packet type %u\n", cmd);
304     va_list argptr;
305     va_start(argptr, identifier);
306     uint16_t len = l2cap_create_signaling_internal(sig_buffer, handle, cmd, identifier, argptr);
307     va_end(argptr);
308     // log_dbg("l2cap_send_signaling_packet con %u!\n", handle);
309     return hci_send_acl_packet(sig_buffer, len);
310 }
311 
312 int l2cap_send_internal(uint16_t local_cid, uint8_t *data, uint16_t len){
313 
314     // check for free places on BT module
315     if (!hci_number_free_acl_slots()) {
316         log_dbg("l2cap_send_internal cid %u, BT module full <-----\n", local_cid);
317         return BTSTACK_ACL_BUFFERS_FULL;
318     }
319     int err = 0;
320 
321     // find channel for local_cid, construct l2cap packet and send
322     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
323     if (channel) {
324         if (channel->packets_granted > 0){
325             --channel->packets_granted;
326             // log_dbg("l2cap_send_internal cid %u, handle %u, 1 credit used, credits left %u;\n",
327             //        local_cid, channel->handle, channel->packets_granted);
328         } else {
329             log_err("l2cap_send_internal cid %u, no credits!\n", local_cid);
330         }
331 
332         // 0 - Connection handle : PB=10 : BC=00
333         bt_store_16(acl_buffer, 0, channel->handle | (2 << 12) | (0 << 14));
334         // 2 - ACL length
335         bt_store_16(acl_buffer, 2,  len + 4);
336         // 4 - L2CAP packet length
337         bt_store_16(acl_buffer, 4,  len + 0);
338         // 6 - L2CAP channel DEST
339         bt_store_16(acl_buffer, 6, channel->remote_cid);
340         // 8 - data
341         memcpy(&acl_buffer[8], data, len);
342 
343         // send
344         err = hci_send_acl_packet(acl_buffer, len+8);
345     }
346 
347     l2cap_hand_out_credits();
348 
349     return err;
350 }
351 
352 // MARK: L2CAP_RUN
353 // process outstanding signaling tasks
354 void l2cap_run(void){
355 
356     // check pending signaling responses
357     while (signaling_responses_pending){
358 
359         if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)) break;
360 
361         hci_con_handle_t handle = signaling_responses[0].handle;
362         uint8_t sig_id = signaling_responses[0].sig_id;
363         uint8_t infoType = signaling_responses[0].infoType;
364 
365         switch (signaling_responses[0].code){
366             case ECHO_REQUEST:
367                 l2cap_send_signaling_packet(handle, ECHO_RESPONSE, sig_id, 0, NULL);
368                 break;
369             case INFORMATION_REQUEST:
370                 if (infoType == 2) {
371                     uint32_t features = 0;
372                     // extended features request supported, however no features present
373                     l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, 4, &features);
374                 } else {
375                     // all other types are not supported
376                     l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 1, 0, NULL);
377                 }
378                 break;
379             default:
380                 // should not happen
381                 break;
382         }
383 
384         // remove first item
385         signaling_responses_pending--;
386         int i;
387         for (i=0; i < signaling_responses_pending; i++){
388             signaling_responses[i] = signaling_responses[i+1];
389         }
390     }
391 
392     uint8_t  config_options[4];
393     linked_item_t *it;
394     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
395 
396         if (!hci_can_send_packet_now(HCI_COMMAND_DATA_PACKET)) break;
397         if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)) break;
398 
399         l2cap_channel_t * channel = (l2cap_channel_t *) it;
400         switch (channel->state){
401 
402             case L2CAP_STATE_WILL_SEND_CREATE_CONNECTION:
403                 // send connection request - set state first
404                 channel->state = L2CAP_STATE_WAIT_CONNECTION_COMPLETE;
405                 // BD_ADDR, Packet_Type, Page_Scan_Repetition_Mode, Reserved, Clock_Offset, Allow_Role_Switch
406                 hci_send_cmd(&hci_create_connection, channel->address, 0xcc18, 0, 0, 0, 1);
407                 break;
408 
409             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE:
410                 l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, 0, 0, channel->reason, 0);
411                 // discard channel - l2cap_finialize_channel_close without sending l2cap close event
412                 linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
413                 free (channel);
414                 break;
415 
416             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT:
417                 l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid, 0, 0);
418                 channel->state = L2CAP_STATE_WAIT_CONFIG_REQ_OR_SEND_CONFIG_REQ;
419                 break;
420 
421             case L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST:
422                 // success, start l2cap handshake
423                 channel->local_sig_id = l2cap_next_sig_id();
424                 l2cap_send_signaling_packet( channel->handle, CONNECTION_REQUEST, channel->local_sig_id, channel->psm, channel->local_cid);
425                 channel->state = L2CAP_STATE_WAIT_CONNECT_RSP;
426                 break;
427 
428             case L2CAP_STATE_WAIT_CONFIG_REQ_OR_SEND_CONFIG_REQ:
429                 // after connection response was received
430                 channel->local_sig_id = l2cap_next_sig_id();
431                 config_options[0] = 1; // MTU
432                 config_options[1] = 2; // len param
433                 bt_store_16( (uint8_t*)&config_options, 2, channel->local_mtu);
434                 l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->local_sig_id, channel->remote_cid, 0, 4, &config_options);
435                 channel->state = L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ;
436                 break;
437 
438             case L2CAP_STATE_WILL_SEND_CONFIG_REQ:
439                 channel->local_sig_id = l2cap_next_sig_id();
440                 config_options[0] = 1; // MTU
441                 config_options[1] = 2; // len param
442                 bt_store_16( (uint8_t*)&config_options, 2, channel->local_mtu);
443                 l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->local_sig_id, channel->remote_cid, 0, 4, &config_options);
444                 channel->state = L2CAP_STATE_WAIT_CONFIG_REQ_RSP;
445                 break;
446 
447             case L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_WILL_SEND_CONFIG_REQ_RSP:
448                 l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, 0, 0, 0, NULL);
449                 channel->state = L2CAP_STATE_WAIT_CONFIG_REQ_RSP;
450                 break;
451 
452             case L2CAP_STATE_WILL_SEND_CONFIG_REQ_RSP:
453                 l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, 0, 0, 0, NULL);
454                 channel->state = L2CAP_STATE_OPEN;
455                 l2cap_emit_channel_opened(channel, 0);  // success
456                 l2cap_emit_credits(channel, 1);
457                 break;
458 
459             case L2CAP_STATE_WILL_SEND_CONFIG_REQ_AND_CONFIG_REQ_RSP:
460                 l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, 0, 0, 0, NULL);
461                 channel->state = L2CAP_STATE_WILL_SEND_CONFIG_REQ;
462                 break;
463 
464             case L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE:
465                 l2cap_send_signaling_packet( channel->handle, DISCONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid);
466                 l2cap_finialize_channel_close(channel);
467                 break;
468 
469             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
470                 channel->local_sig_id = l2cap_next_sig_id();
471                 l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->local_sig_id, channel->remote_cid, channel->local_cid);
472                 channel->state = L2CAP_STATE_WAIT_DISCONNECT;
473                 break;
474             default:
475                 break;
476         }
477     }
478 }
479 
480 static uint16_t l2cap_max_l2cap_mtu(void){
481     return hci_max_acl_data_packet_length()-4;  // 4 bytes for L2CAP header
482 }
483 
484 // open outgoing L2CAP channel
485 void l2cap_create_channel_internal(void * connection, btstack_packet_handler_t packet_handler,
486                                    bd_addr_t address, uint16_t psm, uint16_t mtu){
487 
488     // alloc structure
489     l2cap_channel_t * chan = malloc(sizeof(l2cap_channel_t));
490     // TODO: emit error event
491     if (!chan) return;
492 
493     // limit local mtu to max acl packet length
494     if (mtu > l2cap_max_l2cap_mtu()) {
495         mtu = l2cap_max_l2cap_mtu();
496     }
497 
498     // fill in
499     BD_ADDR_COPY(chan->address, address);
500     chan->psm = psm;
501     chan->handle = 0;
502     chan->connection = connection;
503     chan->packet_handler = packet_handler;
504     chan->remote_mtu = L2CAP_MINIMAL_MTU;
505     chan->local_mtu = mtu;
506     chan->packets_granted = 0;
507 
508     // set initial state
509     chan->state = L2CAP_STATE_WILL_SEND_CREATE_CONNECTION;
510     chan->remote_sig_id = L2CAP_SIG_ID_INVALID;
511     chan->local_sig_id = L2CAP_SIG_ID_INVALID;
512 
513     // add to connections list
514     linked_list_add(&l2cap_channels, (linked_item_t *) chan);
515 
516     l2cap_run();
517 }
518 
519 void l2cap_disconnect_internal(uint16_t local_cid, uint8_t reason){
520     // find channel for local_cid
521     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
522     if (channel) {
523         channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST;
524     }
525     // process
526     l2cap_run();
527 }
528 
529 static void l2cap_handle_connection_failed_for_addr(bd_addr_t address, uint8_t status){
530     linked_item_t *it = (linked_item_t *) &l2cap_channels;
531     while (it->next){
532         l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
533         if ( ! BD_ADDR_CMP( channel->address, address) ){
534             if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
535                 // failure, forward error code
536                 l2cap_emit_channel_opened(channel, status);
537                 // discard channel
538                 it->next = it->next->next;
539                 free (channel);
540             }
541         } else {
542             it = it->next;
543         }
544     }
545 }
546 
547 static void l2cap_handle_connection_success_for_addr(bd_addr_t address, hci_con_handle_t handle){
548     linked_item_t *it;
549     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
550         l2cap_channel_t * channel = (l2cap_channel_t *) it;
551         if ( ! BD_ADDR_CMP( channel->address, address) ){
552             if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
553                 // success, start l2cap handshake
554                 channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST;
555                 channel->handle = handle;
556                 channel->local_cid = l2cap_next_local_cid();
557             }
558         }
559     }
560     // process
561     l2cap_run();
562 }
563 
564 void l2cap_event_handler( uint8_t *packet, uint16_t size ){
565 
566     bd_addr_t address;
567     hci_con_handle_t handle;
568     linked_item_t *it;
569 
570     switch(packet[0]){
571 
572         // handle connection complete events
573         case HCI_EVENT_CONNECTION_COMPLETE:
574             bt_flip_addr(address, &packet[5]);
575             if (packet[2] == 0){
576                 handle = READ_BT_16(packet, 3);
577                 l2cap_handle_connection_success_for_addr(address, handle);
578             } else {
579                 l2cap_handle_connection_failed_for_addr(address, packet[2]);
580             }
581             break;
582 
583         // handle successful create connection cancel command
584         case HCI_EVENT_COMMAND_COMPLETE:
585             if ( COMMAND_COMPLETE_EVENT(packet, hci_create_connection_cancel) ) {
586                 if (packet[5] == 0){
587                     bt_flip_addr(address, &packet[6]);
588                     // CONNECTION TERMINATED BY LOCAL HOST (0X16)
589                     l2cap_handle_connection_failed_for_addr(address, 0x16);
590                 }
591             }
592             l2cap_run();    // try sending signaling packets first
593             break;
594 
595         case HCI_EVENT_COMMAND_STATUS:
596             l2cap_run();    // try sending signaling packets first
597             break;
598 
599         // handle disconnection complete events
600         case HCI_EVENT_DISCONNECTION_COMPLETE:
601             // send l2cap disconnect events for all channels on this handle
602             handle = READ_BT_16(packet, 3);
603             it = (linked_item_t *) &l2cap_channels;
604             while (it->next){
605                 l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
606                 if ( channel->handle == handle ){
607                     // update prev item before free'ing next element - don't call l2cap_finalize_channel_close
608                     it->next = it->next->next;
609                     l2cap_emit_channel_closed(channel);
610                     free (channel);
611                 } else {
612                     it = it->next;
613                 }
614             }
615             break;
616 
617         case HCI_EVENT_NUMBER_OF_COMPLETED_PACKETS:
618             l2cap_run();    // try sending signaling packets first
619             l2cap_hand_out_credits();
620             break;
621 
622         // HCI Connection Timeouts
623         case L2CAP_EVENT_TIMEOUT_CHECK:
624             handle = READ_BT_16(packet, 2);
625             if (hci_authentication_active_for_handle(handle)) break;
626             l2cap_channel_t * channel;
627             int used = 0;
628             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
629                 channel = (l2cap_channel_t *) it;
630                 if (channel->handle == handle) {
631                     used = 1;
632                 }
633             }
634             if (used) break;
635             if (!hci_can_send_packet_now(HCI_COMMAND_DATA_PACKET)) break;
636             hci_send_cmd(&hci_disconnect, handle, 0x13); // remote closed connection
637             break;
638 
639         default:
640             break;
641     }
642 
643     // pass on
644     (*packet_handler)(NULL, HCI_EVENT_PACKET, 0, packet, size);
645 }
646 
647 static void l2cap_handle_disconnect_request(l2cap_channel_t *channel, uint16_t identifier){
648     channel->remote_sig_id = identifier;
649     channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE;
650     l2cap_run();
651 }
652 
653 static void l2cap_handle_connection_request(hci_con_handle_t handle, uint8_t sig_id, uint16_t psm, uint16_t source_cid){
654 
655     // log_dbg("l2cap_handle_connection_request for handle %u, psm %u cid %u\n", handle, psm, source_cid);
656     l2cap_service_t *service = l2cap_get_service(psm);
657     if (!service) {
658         // 0x0002 PSM not supported
659         // log_dbg("l2cap_handle_connection_request no PSM for psm %u/n", psm);
660         l2cap_send_signaling_packet(handle, CONNECTION_RESPONSE, sig_id, 0, 0, 0x0002, 0);
661         return;
662     }
663 
664     hci_connection_t * hci_connection = connection_for_handle( handle );
665     if (!hci_connection) {
666         log_err("no hci_connection for handle %u\n", handle);
667         // TODO: emit error
668         return;
669     }
670     // alloc structure
671     // log_dbg("l2cap_handle_connection_request register channel\n");
672     l2cap_channel_t * channel = malloc(sizeof(l2cap_channel_t));
673     // TODO: emit error event
674     if (!channel) return;
675 
676     // fill in
677     BD_ADDR_COPY(channel->address, hci_connection->address);
678     channel->psm = psm;
679     channel->handle = handle;
680     channel->connection = service->connection;
681     channel->packet_handler = service->packet_handler;
682     channel->local_cid  = l2cap_next_local_cid();
683     channel->remote_cid = source_cid;
684     channel->local_mtu  = service->mtu;
685     channel->remote_mtu = L2CAP_DEFAULT_MTU;
686     channel->packets_granted = 0;
687     channel->remote_sig_id = sig_id;
688 
689     // limit local mtu to max acl packet length
690     if (channel->local_mtu > l2cap_max_l2cap_mtu()) {
691         channel->local_mtu = l2cap_max_l2cap_mtu();
692     }
693 
694     // set initial state
695     channel->state = L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT;
696 
697     // add to connections list
698     linked_list_add(&l2cap_channels, (linked_item_t *) channel);
699 
700     // emit incoming connection request
701     l2cap_emit_connection_request(channel);
702 }
703 
704 void l2cap_accept_connection_internal(uint16_t local_cid){
705     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
706     if (!channel) {
707         log_err("l2cap_accept_connection_internal called but local_cid 0x%x not found", local_cid);
708         return;
709     }
710 
711     channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT;
712 
713     // process
714     l2cap_run();
715 }
716 
717 void l2cap_decline_connection_internal(uint16_t local_cid, uint8_t reason){
718     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid( local_cid);
719     if (!channel) {
720         log_err( "l2cap_decline_connection_internal called but local_cid 0x%x not found", local_cid);
721         return;
722     }
723     channel->state  = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE;
724     channel->reason = reason;
725     l2cap_run();
726 }
727 
728 void l2cap_signaling_handle_configure_request(l2cap_channel_t *channel, uint8_t *command){
729 
730     channel->remote_sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
731 
732     // accept the other's configuration options
733     uint16_t end_pos = 4 + READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
734     uint16_t pos     = 8;
735     while (pos < end_pos){
736         uint8_t type   = command[pos++];
737         uint8_t length = command[pos++];
738         // MTU { type(8): 1, len(8):2, MTU(16) }
739         if ((type & 0x7f) == 1 && length == 2){
740             channel->remote_mtu = READ_BT_16(command, pos);
741             // log_dbg("l2cap cid %u, remote mtu %u\n", channel->local_cid, channel->remote_mtu);
742         }
743         pos += length;
744     }
745 }
746 
747 void l2cap_signaling_handler_channel(l2cap_channel_t *channel, uint8_t *command){
748 
749     uint8_t  code       = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
750     uint8_t  identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
751     uint16_t result = 0;
752 
753     log_dbg("signaling handler code %u, state %u\n", code, channel->state);
754 
755     // handle DISCONNECT REQUESTS seperately
756     if (code == DISCONNECTION_REQUEST){
757         switch (channel->state){
758             case L2CAP_STATE_WAIT_CONFIG_REQ_OR_SEND_CONFIG_REQ:
759             case L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_WILL_SEND_CONFIG_REQ_RSP:
760             case L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ:
761             case L2CAP_STATE_WAIT_CONFIG_REQ:
762             case L2CAP_STATE_WAIT_CONFIG_REQ_RSP:
763             case L2CAP_STATE_WILL_SEND_CONFIG_REQ:
764             case L2CAP_STATE_WILL_SEND_CONFIG_REQ_RSP:
765             case L2CAP_STATE_WILL_SEND_CONFIG_REQ_AND_CONFIG_REQ_RSP:
766             case L2CAP_STATE_OPEN:
767             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
768             case L2CAP_STATE_WAIT_DISCONNECT:
769                 l2cap_handle_disconnect_request(channel, identifier);
770                 break;
771 
772             default:
773                 // ignore in other states
774                 break;
775         }
776         return;
777     }
778 
779     switch (channel->state) {
780 
781         case L2CAP_STATE_WAIT_CONNECT_RSP:
782             switch (code){
783                 case CONNECTION_RESPONSE:
784                     result = READ_BT_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
785                     switch (result) {
786                         case 0:
787                             // successful connection
788                             channel->remote_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
789                             channel->state = L2CAP_STATE_WAIT_CONFIG_REQ_OR_SEND_CONFIG_REQ;
790 #if 0
791     channel->state = L2CAP_STATE_OPEN;
792     l2cap_emit_channel_opened(channel, 0);  // success
793     l2cap_emit_credits(channel, 1);
794 #endif
795                             break;
796                         case 1:
797                             // connection pending. get some coffee
798                             break;
799                         default:
800                             // channel closed
801                             channel->state = L2CAP_STATE_CLOSED;
802 
803                             // map l2cap connection response result to BTstack status enumeration
804                             l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result);
805 
806                             // drop link key if security block
807                             if (L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result == L2CAP_CONNECTION_RESPONSE_RESULT_REFUSED_SECURITY){
808                                 hci_drop_link_key_for_bd_addr(&channel->address);
809                             }
810 
811                             // discard channel
812                             linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
813                             free (channel);
814                             break;
815                     }
816                     break;
817 
818                 default:
819                     //@TODO: implement other signaling packets
820                     break;
821             }
822             break;
823 
824         case L2CAP_STATE_WAIT_CONFIG_REQ_OR_SEND_CONFIG_REQ:
825             switch (code) {
826                 case CONFIGURE_REQUEST:
827                     l2cap_signaling_handle_configure_request(channel, command);
828                     channel->state = L2CAP_STATE_WILL_SEND_CONFIG_REQ_AND_CONFIG_REQ_RSP;
829                     break;
830                 default:
831                     //@TODO: implement other signaling packets
832                     break;
833             }
834             break;
835 
836         case L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_CONFIG_REQ:
837             switch (code) {
838                 case CONFIGURE_RESPONSE:
839                     channel->state = L2CAP_STATE_WAIT_CONFIG_REQ;
840                     break;
841                 case CONFIGURE_REQUEST:
842                     l2cap_signaling_handle_configure_request(channel, command);
843                     channel->state = L2CAP_STATE_WAIT_CONFIG_REQ_RSP_OR_WILL_SEND_CONFIG_REQ_RSP;
844                     break;
845                 default:
846                     //@TODO: implement other signaling packets
847                     break;
848             }
849             break;
850 
851         case L2CAP_STATE_WAIT_CONFIG_REQ:
852             switch (code) {
853                 case CONFIGURE_REQUEST:
854                     l2cap_signaling_handle_configure_request(channel, command);
855                     channel->state = L2CAP_STATE_WILL_SEND_CONFIG_REQ_RSP;
856                     break;
857                 default:
858                     //@TODO: implement other signaling packets
859                     break;
860             }
861             break;
862 
863         case L2CAP_STATE_WAIT_CONFIG_REQ_RSP:
864             switch (code) {
865                 case CONFIGURE_RESPONSE:
866                     channel->state = L2CAP_STATE_OPEN;
867                     l2cap_emit_channel_opened(channel, 0);  // success
868                     l2cap_emit_credits(channel, 1);
869                     break;
870                 default:
871                     //@TODO: implement other signaling packets
872                     break;
873             }
874             break;
875 
876         case L2CAP_STATE_WAIT_DISCONNECT:
877             switch (code) {
878                 case DISCONNECTION_RESPONSE:
879                     l2cap_finialize_channel_close(channel);
880                     break;
881                 default:
882                     //@TODO: implement other signaling packets
883                     break;
884             }
885             break;
886 
887         case L2CAP_STATE_CLOSED:
888             // @TODO handle incoming requests
889             break;
890 
891         case L2CAP_STATE_OPEN:
892             //@TODO: implement other signaling packets, e.g. re-configure
893             break;
894         default:
895             break;
896     }
897     // log_dbg("new state %u\n", channel->state);
898 }
899 
900 
901 void l2cap_signaling_handler_dispatch( hci_con_handle_t handle, uint8_t * command){
902 
903     // get code, signalind identifier and command len
904     uint8_t code   = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
905     uint8_t sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
906 
907     // not for a particular channel, and not CONNECTION_REQUEST, ECHO_[REQUEST|RESPONSE], INFORMATION_REQUEST
908     if (code < 1 || code == ECHO_RESPONSE || code > INFORMATION_REQUEST){
909         return;
910     }
911 
912     // general commands without an assigned channel
913     switch(code) {
914 
915         case CONNECTION_REQUEST: {
916             uint16_t psm =        READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
917             uint16_t source_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+2);
918             l2cap_handle_connection_request(handle, sig_id, psm, source_cid);
919             return;
920         }
921 
922         case ECHO_REQUEST: {
923             if (signaling_responses_pending < NR_PENDING_SIGNALING_RESPONSES) {
924                 signaling_responses[signaling_responses_pending].handle = handle;
925                 signaling_responses[signaling_responses_pending].code = code;
926                 signaling_responses[signaling_responses_pending].sig_id = sig_id;
927                 signaling_responses_pending++;
928             }
929             l2cap_run();
930             return;
931         }
932 
933         case INFORMATION_REQUEST: {
934             if (signaling_responses_pending < NR_PENDING_SIGNALING_RESPONSES) {
935                 // we neither support connectionless L2CAP data nor support any flow control modes yet
936                 uint16_t infoType = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
937                 signaling_responses[signaling_responses_pending].handle = handle;
938                 signaling_responses[signaling_responses_pending].code = code;
939                 signaling_responses[signaling_responses_pending].sig_id = sig_id;
940                 signaling_responses[signaling_responses_pending].infoType = infoType;
941                 signaling_responses_pending++;
942             }
943             l2cap_run();
944             return;
945         }
946 
947         default:
948             break;
949     }
950 
951 
952     // Get potential destination CID
953     uint16_t dest_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
954 
955     // Find channel for this sig_id and connection handle
956     linked_item_t *it;
957     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
958         l2cap_channel_t * channel = (l2cap_channel_t *) it;
959         if (channel->handle == handle) {
960             if (code & 1) {
961                 // match odd commands (responses) by previous signaling identifier
962                 if (channel->local_sig_id == sig_id) {
963                     l2cap_signaling_handler_channel(channel, command);
964                     break;
965                 }
966             } else {
967                 // match even commands (requests) by local channel id
968                 if (channel->local_cid == dest_cid) {
969                     l2cap_signaling_handler_channel(channel, command);
970                     break;
971                 }
972             }
973         }
974     }
975 }
976 
977 void l2cap_acl_handler( uint8_t *packet, uint16_t size ){
978 
979     // Get Channel ID
980     uint16_t channel_id = READ_L2CAP_CHANNEL_ID(packet);
981 
982     // Signaling Packet?
983     if (channel_id == 1) {
984 
985         // Get Connection
986         hci_con_handle_t handle = READ_ACL_CONNECTION_HANDLE(packet);
987 
988         uint16_t command_offset = 8;
989         while (command_offset < size) {
990 
991             // handle signaling commands
992             l2cap_signaling_handler_dispatch(handle, &packet[command_offset]);
993 
994             // increment command_offset
995             command_offset += L2CAP_SIGNALING_COMMAND_DATA_OFFSET + READ_BT_16(packet, command_offset + L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
996         }
997 
998         l2cap_run();
999 
1000         return;
1001     }
1002 
1003     // Find channel for this channel_id and connection handle
1004     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(channel_id);
1005     if (channel) {
1006         l2cap_dispatch(channel, L2CAP_DATA_PACKET, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1007     }
1008 }
1009 
1010 static void l2cap_packet_handler(uint8_t packet_type, uint8_t *packet, uint16_t size){
1011     switch (packet_type) {
1012         case HCI_EVENT_PACKET:
1013             l2cap_event_handler(packet, size);
1014             break;
1015         case HCI_ACL_DATA_PACKET:
1016             l2cap_acl_handler(packet, size);
1017             break;
1018         default:
1019             break;
1020     }
1021 }
1022 
1023 // finalize closed channel - l2cap_handle_disconnect_request & DISCONNECTION_RESPONSE
1024 void l2cap_finialize_channel_close(l2cap_channel_t *channel){
1025     channel->state = L2CAP_STATE_CLOSED;
1026     l2cap_emit_channel_closed(channel);
1027     // discard channel
1028     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
1029     free (channel);
1030 }
1031 
1032 l2cap_service_t * l2cap_get_service(uint16_t psm){
1033     linked_item_t *it;
1034 
1035     // close open channels
1036     for (it = (linked_item_t *) l2cap_services; it ; it = it->next){
1037         l2cap_service_t * service = ((l2cap_service_t *) it);
1038         if ( service->psm == psm){
1039             return service;
1040         };
1041     }
1042     return NULL;
1043 }
1044 
1045 void l2cap_register_service_internal(void *connection, btstack_packet_handler_t packet_handler, uint16_t psm, uint16_t mtu){
1046     // check for alread registered psm // TODO: emit error event
1047     l2cap_service_t *service = l2cap_get_service(psm);
1048     if (service) return;
1049 
1050     // alloc structure     // TODO: emit error event
1051     service = malloc(sizeof(l2cap_service_t));
1052     if (!service) return;
1053 
1054     // fill in
1055     service->psm = psm;
1056     service->mtu = mtu;
1057     service->connection = connection;
1058     service->packet_handler = packet_handler;
1059 
1060     // add to services list
1061     linked_list_add(&l2cap_services, (linked_item_t *) service);
1062 }
1063 
1064 void l2cap_unregister_service_internal(void *connection, uint16_t psm){
1065     l2cap_service_t *service = l2cap_get_service(psm);
1066     if (!service) return;
1067     linked_list_remove(&l2cap_services, (linked_item_t *) service);
1068     free(service);
1069 }
1070 
1071 //
1072 void l2cap_close_connection(void *connection){
1073     linked_item_t *it;
1074 
1075     // close open channels - note to myself: no channel is freed, so no new for fancy iterator tricks
1076     l2cap_channel_t * channel;
1077     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
1078         channel = (l2cap_channel_t *) it;
1079         if (channel->connection == connection) {
1080             channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST;
1081         }
1082     }
1083 
1084     // unregister services
1085     it = (linked_item_t *) &l2cap_services;
1086     while (it->next) {
1087         l2cap_service_t * service = (l2cap_service_t *) it->next;
1088         if (service->connection == connection){
1089             it->next = it->next->next;
1090             free(service);
1091         } else {
1092             it = it->next;
1093         }
1094     }
1095 
1096     // process
1097     l2cap_run();
1098 }
1099