xref: /btstack/src/l2cap.c (revision 5628cf69b5a59a9cf27711ff0736732db872c35a)
1 /*
2  * Copyright (C) 2014 BlueKitchen GmbH
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the copyright holders nor the names of
14  *    contributors may be used to endorse or promote products derived
15  *    from this software without specific prior written permission.
16  * 4. Any redistribution, use, or modification is done solely for
17  *    personal benefit and not for any commercial purpose or for
18  *    monetary gain.
19  *
20  * THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
24  * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
26  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
27  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
30  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  *
33  * Please inquire about commercial licensing options at
34  * [email protected]
35  *
36  */
37 
38 /*
39  *  l2cap.c
40  *
41  *  Logical Link Control and Adaption Protocl (L2CAP)
42  *
43  *  Created by Matthias Ringwald on 5/16/09.
44  */
45 
46 #include "l2cap.h"
47 #include "hci.h"
48 #include "hci_dump.h"
49 #include "btstack_debug.h"
50 #include "btstack_memory.h"
51 
52 #include <stdarg.h>
53 #include <string.h>
54 
55 #include <stdio.h>
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 3
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 // internal table
70 #define L2CAP_FIXED_CHANNEL_TABLE_INDEX_ATTRIBUTE_PROTOCOL 0
71 #define L2CAP_FIXED_CHANNEL_TABLE_INDEX_SECURITY_MANAGER_PROTOCOL  1
72 #define L2CAP_FIXED_CHANNEL_TABLE_INDEX_CONNECTIONLESS_CHANNEL 2
73 #define L2CAP_FIXED_CHANNEL_TABLE_SIZE (L2CAP_FIXED_CHANNEL_TABLE_INDEX_CONNECTIONLESS_CHANNEL+1)
74 
75 // prototypes
76 static void l2cap_finialize_channel_close(l2cap_channel_t *channel);
77 static inline 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_can_send_now(l2cap_channel_t *channel);
80 static void l2cap_emit_channel_closed(l2cap_channel_t *channel);
81 static void l2cap_emit_connection_request(l2cap_channel_t *channel);
82 static int  l2cap_channel_ready_for_open(l2cap_channel_t *channel);
83 static void l2cap_hci_event_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size);
84 static void l2cap_acl_handler(uint8_t packet_type, uint8_t *packet, uint16_t size );
85 
86 typedef struct l2cap_fixed_channel {
87     btstack_packet_handler_t callback;
88     // uint8_t waiting_for_can_send_now;
89 } l2cap_fixed_channel_t;
90 
91 static btstack_linked_list_t l2cap_channels;
92 static btstack_linked_list_t l2cap_services;
93 static btstack_linked_list_t l2cap_le_channels;
94 static btstack_linked_list_t l2cap_le_services;
95 
96 // used to cache l2cap rejects, echo, and informational requests
97 static l2cap_signaling_response_t signaling_responses[NR_PENDING_SIGNALING_RESPONSES];
98 static int signaling_responses_pending;
99 
100 static uint8_t require_security_level2_for_outgoing_sdp;
101 
102 static btstack_packet_callback_registration_t hci_event_callback_registration;
103 
104 static btstack_packet_handler_t l2cap_event_packet_handler;
105 static l2cap_fixed_channel_t fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_SIZE];
106 
107 // static btstack_packet_handler_t fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_INDEX_ATTRIBUTE_PROTOCOL];
108 // static btstack_packet_handler_t fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_INDEX_SECURITY_MANAGER_PROTOCOL];
109 // static btstack_packet_handler_t fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_INDEX_CONNECTIONLESS_CHANNEL];
110 
111 static int l2cap_fixed_channel_table_index_for_channel_id(uint16_t channel_id){
112     switch (channel_id){
113         case L2CAP_CID_ATTRIBUTE_PROTOCOL:
114             return L2CAP_FIXED_CHANNEL_TABLE_INDEX_ATTRIBUTE_PROTOCOL;
115         case L2CAP_CID_SECURITY_MANAGER_PROTOCOL:
116             return  L2CAP_FIXED_CHANNEL_TABLE_INDEX_SECURITY_MANAGER_PROTOCOL;
117         case L2CAP_CID_CONNECTIONLESS_CHANNEL:
118             return  L2CAP_FIXED_CHANNEL_TABLE_INDEX_CONNECTIONLESS_CHANNEL;
119         default:
120             return -1;
121         }
122 }
123 
124 void l2cap_init(void){
125     signaling_responses_pending = 0;
126 
127     l2cap_channels = NULL;
128     l2cap_services = NULL;
129     l2cap_le_services = NULL;
130     l2cap_le_channels = NULL;
131 
132     l2cap_event_packet_handler = NULL;
133     memset(fixed_channels, 0, sizeof(fixed_channels));
134 
135     require_security_level2_for_outgoing_sdp = 0;
136 
137     //
138     // register callback with HCI
139     //
140     hci_event_callback_registration.callback = &l2cap_hci_event_handler;
141     hci_add_event_handler(&hci_event_callback_registration);
142 
143     hci_register_acl_packet_handler(&l2cap_acl_handler);
144 
145     hci_connectable_control(0); // no services yet
146 }
147 
148 void l2cap_register_packet_handler(void (*handler)(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size)){
149     l2cap_event_packet_handler = handler;
150 }
151 
152 static void l2cap_dispatch_to_channel(l2cap_channel_t *channel, uint8_t type, uint8_t * data, uint16_t size){
153     (* (channel->packet_handler))(type, channel->local_cid, data, size);
154 }
155 
156 void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status) {
157     log_info("L2CAP_EVENT_CHANNEL_OPENED status 0x%x addr %s handle 0x%x psm 0x%x local_cid 0x%x remote_cid 0x%x local_mtu %u, remote_mtu %u, flush_timeout %u",
158              status, bd_addr_to_str(channel->address), channel->handle, channel->psm,
159              channel->local_cid, channel->remote_cid, channel->local_mtu, channel->remote_mtu, channel->flush_timeout);
160     uint8_t event[23];
161     event[0] = L2CAP_EVENT_CHANNEL_OPENED;
162     event[1] = sizeof(event) - 2;
163     event[2] = status;
164     bt_flip_addr(&event[3], channel->address);
165     little_endian_store_16(event,  9, channel->handle);
166     little_endian_store_16(event, 11, channel->psm);
167     little_endian_store_16(event, 13, channel->local_cid);
168     little_endian_store_16(event, 15, channel->remote_cid);
169     little_endian_store_16(event, 17, channel->local_mtu);
170     little_endian_store_16(event, 19, channel->remote_mtu);
171     little_endian_store_16(event, 21, channel->flush_timeout);
172     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
173     l2cap_dispatch_to_channel(channel, HCI_EVENT_PACKET, event, sizeof(event));
174 
175     // if channel opened successfully, also send can send now if possible
176     if (status) return;
177     if (hci_can_send_acl_packet_now(channel->handle)){
178         l2cap_emit_can_send_now(channel);
179     } else {
180         channel->waiting_for_can_send_now = 1;
181     }
182 }
183 
184 void l2cap_emit_channel_closed(l2cap_channel_t *channel) {
185     log_info("L2CAP_EVENT_CHANNEL_CLOSED local_cid 0x%x", channel->local_cid);
186     uint8_t event[4];
187     event[0] = L2CAP_EVENT_CHANNEL_CLOSED;
188     event[1] = sizeof(event) - 2;
189     little_endian_store_16(event, 2, channel->local_cid);
190     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
191     l2cap_dispatch_to_channel(channel, HCI_EVENT_PACKET, event, sizeof(event));
192 }
193 
194 void l2cap_emit_connection_request(l2cap_channel_t *channel) {
195     log_info("L2CAP_EVENT_INCOMING_CONNECTION addr %s handle 0x%x psm 0x%x local_cid 0x%x remote_cid 0x%x",
196              bd_addr_to_str(channel->address), channel->handle,  channel->psm, channel->local_cid, channel->remote_cid);
197     uint8_t event[16];
198     event[0] = L2CAP_EVENT_INCOMING_CONNECTION;
199     event[1] = sizeof(event) - 2;
200     bt_flip_addr(&event[2], channel->address);
201     little_endian_store_16(event,  8, channel->handle);
202     little_endian_store_16(event, 10, channel->psm);
203     little_endian_store_16(event, 12, channel->local_cid);
204     little_endian_store_16(event, 14, channel->remote_cid);
205     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
206     l2cap_dispatch_to_channel(channel, HCI_EVENT_PACKET, event, sizeof(event));
207 }
208 
209 static void l2cap_emit_can_send_now(l2cap_channel_t *channel) {
210     log_info("L2CAP_EVENT_CHANNEL_CAN_SEND_NOW local_cid 0x%x", channel->local_cid);
211     uint8_t event[4];
212     event[0] = L2CAP_EVENT_CAN_SEND_NOW;
213     event[1] = sizeof(event) - 2;
214     little_endian_store_16(event, 2, channel->local_cid);
215     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
216     l2cap_dispatch_to_channel(channel, HCI_EVENT_PACKET, event, sizeof(event));
217 }
218 
219 static void l2cap_emit_connection_parameter_update_response(uint16_t handle, uint16_t result){
220     uint8_t event[6];
221     event[0] = L2CAP_EVENT_CONNECTION_PARAMETER_UPDATE_RESPONSE;
222     event[1] = 4;
223     little_endian_store_16(event, 2, handle);
224     little_endian_store_16(event, 4, result);
225     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
226     if (!l2cap_event_packet_handler) return;
227     (*l2cap_event_packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
228 }
229 
230 static l2cap_channel_t * l2cap_get_channel_for_local_cid(uint16_t local_cid){
231     btstack_linked_list_iterator_t it;
232     btstack_linked_list_iterator_init(&it, &l2cap_channels);
233     while (btstack_linked_list_iterator_has_next(&it)){
234         l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
235         if ( channel->local_cid == local_cid) {
236             return channel;
237         }
238     }
239     return NULL;
240 }
241 
242 int  l2cap_can_send_packet_now(uint16_t local_cid){
243     l2cap_channel_t *channel = l2cap_get_channel_for_local_cid(local_cid);
244     if (!channel) return 0;
245     int can_send = hci_can_send_acl_packet_now(channel->handle);
246     if (!can_send){
247         channel->waiting_for_can_send_now = 1;
248     }
249     return can_send;
250 }
251 
252 int  l2cap_can_send_prepared_packet_now(uint16_t local_cid){
253     l2cap_channel_t *channel = l2cap_get_channel_for_local_cid(local_cid);
254     if (!channel) return 0;
255     int can_send = hci_can_send_prepared_acl_packet_now(channel->handle);
256     if (!can_send){
257         channel->waiting_for_can_send_now = 1;
258     }
259     return can_send;
260 }
261 
262 int  l2cap_can_send_fixed_channel_packet_now(uint16_t handle){
263     return hci_can_send_acl_packet_now(handle);
264 }
265 
266 uint16_t l2cap_get_remote_mtu_for_local_cid(uint16_t local_cid){
267     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
268     if (channel) {
269         return channel->remote_mtu;
270     }
271     return 0;
272 }
273 
274 static l2cap_channel_t * l2cap_channel_for_rtx_timer(btstack_timer_source_t * ts){
275     btstack_linked_list_iterator_t it;
276     btstack_linked_list_iterator_init(&it, &l2cap_channels);
277     while (btstack_linked_list_iterator_has_next(&it)){
278         l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
279         if ( &channel->rtx == ts) {
280             return channel;
281         }
282     }
283     return NULL;
284 }
285 
286 static void l2cap_rtx_timeout(btstack_timer_source_t * ts){
287     l2cap_channel_t * channel = l2cap_channel_for_rtx_timer(ts);
288     if (!ts) return;
289 
290     log_info("l2cap_rtx_timeout for local cid 0x%02x", channel->local_cid);
291 
292     // "When terminating the channel, it is not necessary to send a L2CAP_DisconnectReq
293     //  and enter WAIT_DISCONNECT state. Channels can be transitioned directly to the CLOSED state."
294     // notify client
295     l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_RTX_TIMEOUT);
296 
297     // discard channel
298     // no need to stop timer here, it is removed from list during timer callback
299     btstack_linked_list_remove(&l2cap_channels, (btstack_linked_item_t *) channel);
300     btstack_memory_l2cap_channel_free(channel);
301 }
302 
303 static void l2cap_stop_rtx(l2cap_channel_t * channel){
304     log_info("l2cap_stop_rtx for local cid 0x%02x", channel->local_cid);
305     btstack_run_loop_remove_timer(&channel->rtx);
306 }
307 
308 static void l2cap_start_rtx(l2cap_channel_t * channel){
309     l2cap_stop_rtx(channel);
310     log_info("l2cap_start_rtx for local cid 0x%02x", channel->local_cid);
311     btstack_run_loop_set_timer_handler(&channel->rtx, l2cap_rtx_timeout);
312     btstack_run_loop_set_timer(&channel->rtx, L2CAP_RTX_TIMEOUT_MS);
313     btstack_run_loop_add_timer(&channel->rtx);
314 }
315 
316 static void l2cap_start_ertx(l2cap_channel_t * channel){
317     log_info("l2cap_start_ertx for local cid 0x%02x", channel->local_cid);
318     l2cap_stop_rtx(channel);
319     btstack_run_loop_set_timer_handler(&channel->rtx, l2cap_rtx_timeout);
320     btstack_run_loop_set_timer(&channel->rtx, L2CAP_ERTX_TIMEOUT_MS);
321     btstack_run_loop_add_timer(&channel->rtx);
322 }
323 
324 void l2cap_require_security_level_2_for_outgoing_sdp(void){
325     require_security_level2_for_outgoing_sdp = 1;
326 }
327 
328 static int l2cap_security_level_0_allowed_for_PSM(uint16_t psm){
329     return (psm == PSM_SDP) && (!require_security_level2_for_outgoing_sdp);
330 }
331 
332 static int l2cap_send_signaling_packet(hci_con_handle_t handle, L2CAP_SIGNALING_COMMANDS cmd, uint8_t identifier, ...){
333 
334     if (!hci_can_send_acl_packet_now(handle)){
335         log_info("l2cap_send_signaling_packet, cannot send");
336         return BTSTACK_ACL_BUFFERS_FULL;
337     }
338 
339     // log_info("l2cap_send_signaling_packet type %u", cmd);
340     hci_reserve_packet_buffer();
341     uint8_t *acl_buffer = hci_get_outgoing_packet_buffer();
342     va_list argptr;
343     va_start(argptr, identifier);
344     uint16_t len = l2cap_create_signaling_classic(acl_buffer, handle, cmd, identifier, argptr);
345     va_end(argptr);
346     // log_info("l2cap_send_signaling_packet con %u!", handle);
347     return hci_send_acl_packet_buffer(len);
348 }
349 
350 #ifdef ENABLE_BLE
351 static int l2cap_send_le_signaling_packet(hci_con_handle_t handle, L2CAP_SIGNALING_COMMANDS cmd, uint8_t identifier, ...){
352 
353     if (!hci_can_send_acl_packet_now(handle)){
354         log_info("l2cap_send_signaling_packet, cannot send");
355         return BTSTACK_ACL_BUFFERS_FULL;
356     }
357 
358     // log_info("l2cap_send_signaling_packet type %u", cmd);
359     hci_reserve_packet_buffer();
360     uint8_t *acl_buffer = hci_get_outgoing_packet_buffer();
361     va_list argptr;
362     va_start(argptr, identifier);
363     uint16_t len = l2cap_create_signaling_le(acl_buffer, handle, cmd, identifier, argptr);
364     va_end(argptr);
365     // log_info("l2cap_send_signaling_packet con %u!", handle);
366     return hci_send_acl_packet_buffer(len);
367 }
368 #endif
369 
370 uint8_t *l2cap_get_outgoing_buffer(void){
371     return hci_get_outgoing_packet_buffer() + COMPLETE_L2CAP_HEADER; // 8 bytes
372 }
373 
374 int l2cap_reserve_packet_buffer(void){
375     return hci_reserve_packet_buffer();
376 }
377 
378 void l2cap_release_packet_buffer(void){
379     hci_release_packet_buffer();
380 }
381 
382 
383 int l2cap_send_prepared(uint16_t local_cid, uint16_t len){
384 
385     if (!hci_is_packet_buffer_reserved()){
386         log_error("l2cap_send_prepared called without reserving packet first");
387         return BTSTACK_ACL_BUFFERS_FULL;
388     }
389 
390     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
391     if (!channel) {
392         log_error("l2cap_send_prepared no channel for cid 0x%02x", local_cid);
393         return -1;   // TODO: define error
394     }
395 
396     if (!hci_can_send_prepared_acl_packet_now(channel->handle)){
397         log_info("l2cap_send_prepared cid 0x%02x, cannot send", local_cid);
398         return BTSTACK_ACL_BUFFERS_FULL;
399     }
400 
401     log_debug("l2cap_send_prepared cid 0x%02x, handle %u, 1 credit used", local_cid, channel->handle);
402 
403     uint8_t *acl_buffer = hci_get_outgoing_packet_buffer();
404 
405     int pb = hci_non_flushable_packet_boundary_flag_supported() ? 0x00 : 0x02;
406 
407     // 0 - Connection handle : PB=pb : BC=00
408     little_endian_store_16(acl_buffer, 0, channel->handle | (pb << 12) | (0 << 14));
409     // 2 - ACL length
410     little_endian_store_16(acl_buffer, 2,  len + 4);
411     // 4 - L2CAP packet length
412     little_endian_store_16(acl_buffer, 4,  len + 0);
413     // 6 - L2CAP channel DEST
414     little_endian_store_16(acl_buffer, 6, channel->remote_cid);
415     // send
416     int err = hci_send_acl_packet_buffer(len+8);
417 
418     return err;
419 }
420 
421 int l2cap_send_prepared_connectionless(uint16_t handle, uint16_t cid, uint16_t len){
422 
423     if (!hci_is_packet_buffer_reserved()){
424         log_error("l2cap_send_prepared_connectionless called without reserving packet first");
425         return BTSTACK_ACL_BUFFERS_FULL;
426     }
427 
428     if (!hci_can_send_prepared_acl_packet_now(handle)){
429         log_info("l2cap_send_prepared_connectionless handle 0x%02x, cid 0x%02x, cannot send", handle, cid);
430         return BTSTACK_ACL_BUFFERS_FULL;
431     }
432 
433     log_debug("l2cap_send_prepared_connectionless handle %u, cid 0x%02x", handle, cid);
434 
435     uint8_t *acl_buffer = hci_get_outgoing_packet_buffer();
436 
437     int pb = hci_non_flushable_packet_boundary_flag_supported() ? 0x00 : 0x02;
438 
439     // 0 - Connection handle : PB=pb : BC=00
440     little_endian_store_16(acl_buffer, 0, handle | (pb << 12) | (0 << 14));
441     // 2 - ACL length
442     little_endian_store_16(acl_buffer, 2,  len + 4);
443     // 4 - L2CAP packet length
444     little_endian_store_16(acl_buffer, 4,  len + 0);
445     // 6 - L2CAP channel DEST
446     little_endian_store_16(acl_buffer, 6, cid);
447     // send
448     int err = hci_send_acl_packet_buffer(len+8);
449 
450     return err;
451 }
452 
453 int l2cap_send(uint16_t local_cid, uint8_t *data, uint16_t len){
454 
455     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
456     if (!channel) {
457         log_error("l2cap_send no channel for cid 0x%02x", local_cid);
458         return -1;   // TODO: define error
459     }
460 
461     if (len > channel->remote_mtu){
462         log_error("l2cap_send cid 0x%02x, data length exceeds remote MTU.", local_cid);
463         return L2CAP_DATA_LEN_EXCEEDS_REMOTE_MTU;
464     }
465 
466     if (!hci_can_send_acl_packet_now(channel->handle)){
467         log_info("l2cap_send cid 0x%02x, cannot send", local_cid);
468         return BTSTACK_ACL_BUFFERS_FULL;
469     }
470 
471     hci_reserve_packet_buffer();
472     uint8_t *acl_buffer = hci_get_outgoing_packet_buffer();
473 
474     memcpy(&acl_buffer[8], data, len);
475 
476     return l2cap_send_prepared(local_cid, len);
477 }
478 
479 int l2cap_send_connectionless(uint16_t handle, uint16_t cid, uint8_t *data, uint16_t len){
480 
481     if (!hci_can_send_acl_packet_now(handle)){
482         log_info("l2cap_send cid 0x%02x, cannot send", cid);
483         return BTSTACK_ACL_BUFFERS_FULL;
484     }
485 
486     hci_reserve_packet_buffer();
487     uint8_t *acl_buffer = hci_get_outgoing_packet_buffer();
488 
489     memcpy(&acl_buffer[8], data, len);
490 
491     return l2cap_send_prepared_connectionless(handle, cid, len);
492 }
493 
494 int l2cap_send_echo_request(uint16_t handle, uint8_t *data, uint16_t len){
495     return l2cap_send_signaling_packet(handle, ECHO_REQUEST, 0x77, len, data);
496 }
497 
498 static inline void channelStateVarSetFlag(l2cap_channel_t *channel, L2CAP_CHANNEL_STATE_VAR flag){
499     channel->state_var = (L2CAP_CHANNEL_STATE_VAR) (channel->state_var | flag);
500 }
501 
502 static inline void channelStateVarClearFlag(l2cap_channel_t *channel, L2CAP_CHANNEL_STATE_VAR flag){
503     channel->state_var = (L2CAP_CHANNEL_STATE_VAR) (channel->state_var & ~flag);
504 }
505 
506 
507 
508 // MARK: L2CAP_RUN
509 // process outstanding signaling tasks
510 static void l2cap_run(void){
511 
512     // log_info("l2cap_run: entered");
513 
514     // check pending signaling responses
515     while (signaling_responses_pending){
516 
517         hci_con_handle_t handle = signaling_responses[0].handle;
518 
519         if (!hci_can_send_acl_packet_now(handle)) break;
520 
521         uint8_t  sig_id = signaling_responses[0].sig_id;
522         uint16_t infoType = signaling_responses[0].data;    // INFORMATION_REQUEST
523         uint16_t result   = signaling_responses[0].data;    // CONNECTION_REQUEST, COMMAND_REJECT
524         uint8_t  response_code = signaling_responses[0].code;
525 
526         // remove first item before sending (to avoid sending response mutliple times)
527         signaling_responses_pending--;
528         int i;
529         for (i=0; i < signaling_responses_pending; i++){
530             memcpy(&signaling_responses[i], &signaling_responses[i+1], sizeof(l2cap_signaling_response_t));
531         }
532 
533         switch (response_code){
534             case CONNECTION_REQUEST:
535                 l2cap_send_signaling_packet(handle, CONNECTION_RESPONSE, sig_id, 0, 0, result, 0);
536                 // also disconnect if result is 0x0003 - security blocked
537                 if (result == 0x0003){
538                     hci_disconnect_security_block(handle);
539                 }
540                 break;
541             case ECHO_REQUEST:
542                 l2cap_send_signaling_packet(handle, ECHO_RESPONSE, sig_id, 0, NULL);
543                 break;
544             case INFORMATION_REQUEST:
545                 switch (infoType){
546                     case 1: { // Connectionless MTU
547                         uint16_t connectionless_mtu = hci_max_acl_data_packet_length();
548                         l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, sizeof(connectionless_mtu), &connectionless_mtu);
549                         break;
550                     }
551                     case 2: { // Extended Features Supported
552                         // extended features request supported, features: fixed channels, unicast connectionless data reception
553                         uint32_t features = 0x280;
554                         l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, sizeof(features), &features);
555                         break;
556                     }
557                     case 3: { // Fixed Channels Supported
558                         uint8_t map[8];
559                         memset(map, 0, 8);
560                         map[0] = 0x01;  // L2CAP Signaling Channel (0x01) + Connectionless reception (0x02)
561                         l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, sizeof(map), &map);
562                         break;
563                     }
564                     default:
565                         // all other types are not supported
566                         l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 1, 0, NULL);
567                         break;
568                 }
569                 break;
570             case COMMAND_REJECT:
571                 l2cap_send_signaling_packet(handle, COMMAND_REJECT, sig_id, result, 0, NULL);
572 #ifdef ENABLE_BLE
573             case COMMAND_REJECT_LE:
574                 l2cap_send_le_signaling_packet(handle, COMMAND_REJECT, sig_id, result, 0, NULL);
575                 break;
576 #endif
577             default:
578                 // should not happen
579                 break;
580         }
581     }
582 
583     uint8_t  config_options[4];
584     btstack_linked_list_iterator_t it;
585     btstack_linked_list_iterator_init(&it, &l2cap_channels);
586     while (btstack_linked_list_iterator_has_next(&it)){
587 
588         l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
589         // log_info("l2cap_run: channel %p, state %u, var 0x%02x", channel, channel->state, channel->state_var);
590         switch (channel->state){
591 
592             case L2CAP_STATE_WAIT_INCOMING_SECURITY_LEVEL_UPDATE:
593             case L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT:
594                 if (!hci_can_send_acl_packet_now(channel->handle)) break;
595                 if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONN_RESP_PEND) {
596                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONN_RESP_PEND);
597                     l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid, 1, 0);
598                 }
599                 break;
600 
601             case L2CAP_STATE_WILL_SEND_CREATE_CONNECTION:
602                 if (!hci_can_send_command_packet_now()) break;
603                 // send connection request - set state first
604                 channel->state = L2CAP_STATE_WAIT_CONNECTION_COMPLETE;
605                 // BD_ADDR, Packet_Type, Page_Scan_Repetition_Mode, Reserved, Clock_Offset, Allow_Role_Switch
606                 hci_send_cmd(&hci_create_connection, channel->address, hci_usable_acl_packet_types(), 0, 0, 0, 1);
607                 break;
608 
609             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE:
610                 if (!hci_can_send_acl_packet_now(channel->handle)) break;
611                 channel->state = L2CAP_STATE_INVALID;
612                 l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid, channel->reason, 0);
613                 // discard channel - l2cap_finialize_channel_close without sending l2cap close event
614                 l2cap_stop_rtx(channel);
615                 btstack_linked_list_iterator_remove(&it);
616                 btstack_memory_l2cap_channel_free(channel);
617                 break;
618 
619             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT:
620                 if (!hci_can_send_acl_packet_now(channel->handle)) break;
621                 channel->state = L2CAP_STATE_CONFIG;
622                 channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
623                 l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid, 0, 0);
624                 break;
625 
626             case L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST:
627                 if (!hci_can_send_acl_packet_now(channel->handle)) break;
628                 // success, start l2cap handshake
629                 channel->local_sig_id = l2cap_next_sig_id();
630                 channel->state = L2CAP_STATE_WAIT_CONNECT_RSP;
631                 l2cap_send_signaling_packet( channel->handle, CONNECTION_REQUEST, channel->local_sig_id, channel->psm, channel->local_cid);
632                 l2cap_start_rtx(channel);
633                 break;
634 
635             case L2CAP_STATE_CONFIG:
636                 if (!hci_can_send_acl_packet_now(channel->handle)) break;
637                 if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP){
638                     uint16_t flags = 0;
639                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP);
640                     if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_CONT) {
641                         flags = 1;
642                     } else {
643                         channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP);
644                     }
645                     if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_INVALID){
646                         l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, flags, L2CAP_CONF_RESULT_UNKNOWN_OPTIONS, 0, NULL);
647                     } else if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_MTU){
648                         config_options[0] = 1; // MTU
649                         config_options[1] = 2; // len param
650                         little_endian_store_16( (uint8_t*)&config_options, 2, channel->remote_mtu);
651                         l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, flags, 0, 4, &config_options);
652                         channelStateVarClearFlag(channel,L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_MTU);
653                     } else {
654                         l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, flags, 0, 0, NULL);
655                     }
656                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_CONT);
657                 }
658                 else if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ){
659                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
660                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SENT_CONF_REQ);
661                     channel->local_sig_id = l2cap_next_sig_id();
662                     config_options[0] = 1; // MTU
663                     config_options[1] = 2; // len param
664                     little_endian_store_16( (uint8_t*)&config_options, 2, channel->local_mtu);
665                     l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->local_sig_id, channel->remote_cid, 0, 4, &config_options);
666                     l2cap_start_rtx(channel);
667                 }
668                 if (l2cap_channel_ready_for_open(channel)){
669                     channel->state = L2CAP_STATE_OPEN;
670                     l2cap_emit_channel_opened(channel, 0);  // success
671                 }
672                 break;
673 
674             case L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE:
675                 if (!hci_can_send_acl_packet_now(channel->handle)) break;
676                 channel->state = L2CAP_STATE_INVALID;
677                 l2cap_send_signaling_packet( channel->handle, DISCONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid);
678                 // we don't start an RTX timer for a disconnect - there's no point in closing the channel if the other side doesn't respond :)
679                 l2cap_finialize_channel_close(channel);  // -- remove from list
680                 break;
681 
682             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
683                 if (!hci_can_send_acl_packet_now(channel->handle)) break;
684                 channel->local_sig_id = l2cap_next_sig_id();
685                 channel->state = L2CAP_STATE_WAIT_DISCONNECT;
686                 l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->local_sig_id, channel->remote_cid, channel->local_cid);
687                 break;
688             default:
689                 break;
690         }
691     }
692 
693 #ifdef ENABLE_BLE
694     // send l2cap con paramter update if necessary
695     hci_connections_get_iterator(&it);
696     while(btstack_linked_list_iterator_has_next(&it)){
697         hci_connection_t * connection = (hci_connection_t *) btstack_linked_list_iterator_next(&it);
698         if (connection->address_type != BD_ADDR_TYPE_LE_PUBLIC && connection->address_type != BD_ADDR_TYPE_LE_RANDOM) continue;
699         if (!hci_can_send_acl_packet_now(connection->con_handle)) continue;
700         switch (connection->le_con_parameter_update_state){
701             case CON_PARAMETER_UPDATE_SEND_REQUEST:
702                 connection->le_con_parameter_update_state = CON_PARAMETER_UPDATE_NONE;
703                 l2cap_send_le_signaling_packet(connection->con_handle, CONNECTION_PARAMETER_UPDATE_REQUEST, connection->le_con_param_update_identifier,
704                                                connection->le_conn_interval_min, connection->le_conn_interval_max, connection->le_conn_latency, connection->le_supervision_timeout);
705                 break;
706             case CON_PARAMETER_UPDATE_SEND_RESPONSE:
707                 connection->le_con_parameter_update_state = CON_PARAMETER_UPDATE_CHANGE_HCI_CON_PARAMETERS;
708                 l2cap_send_le_signaling_packet(connection->con_handle, CONNECTION_PARAMETER_UPDATE_RESPONSE, connection->le_con_param_update_identifier, 0);
709                 break;
710             case CON_PARAMETER_UPDATE_DENY:
711                 connection->le_con_parameter_update_state = CON_PARAMETER_UPDATE_NONE;
712                 l2cap_send_le_signaling_packet(connection->con_handle, CONNECTION_PARAMETER_UPDATE_RESPONSE, connection->le_con_param_update_identifier, 1);
713                 break;
714             default:
715                 break;
716         }
717     }
718 #endif
719 
720     // log_info("l2cap_run: exit");
721 }
722 
723 uint16_t l2cap_max_mtu(void){
724     return HCI_ACL_PAYLOAD_SIZE - L2CAP_HEADER_SIZE;
725 }
726 
727 uint16_t l2cap_max_le_mtu(void){
728     return l2cap_max_mtu();
729 }
730 
731 static void l2cap_handle_connection_complete(uint16_t handle, l2cap_channel_t * channel){
732     if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
733         log_info("l2cap_handle_connection_complete expected state");
734         // success, start l2cap handshake
735         channel->handle = handle;
736         // check remote SSP feature first
737         channel->state = L2CAP_STATE_WAIT_REMOTE_SUPPORTED_FEATURES;
738     }
739 }
740 
741 static void l2cap_handle_remote_supported_features_received(l2cap_channel_t * channel){
742     if (channel->state != L2CAP_STATE_WAIT_REMOTE_SUPPORTED_FEATURES) return;
743 
744     // we have been waiting for remote supported features, if both support SSP,
745     log_info("l2cap received remote supported features, sec_level_0_allowed for psm %u = %u", channel->psm, l2cap_security_level_0_allowed_for_PSM(channel->psm));
746     if (hci_ssp_supported_on_both_sides(channel->handle) && !l2cap_security_level_0_allowed_for_PSM(channel->psm)){
747         // request security level 2
748         channel->state = L2CAP_STATE_WAIT_OUTGOING_SECURITY_LEVEL_UPDATE;
749         gap_request_security_level(channel->handle, LEVEL_2);
750         return;
751     }
752     // fine, go ahead
753     channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST;
754 }
755 
756 /**
757  * @brief Creates L2CAP channel to the PSM of a remote device with baseband address. A new baseband connection will be initiated if necessary.
758  * @param packet_handler
759  * @param address
760  * @param psm
761  * @param mtu
762  * @param local_cid
763  */
764 uint8_t l2cap_create_channel(btstack_packet_handler_t channel_packet_handler, bd_addr_t address, uint16_t psm, uint16_t mtu, uint16_t * out_local_cid){
765     log_info("L2CAP_CREATE_CHANNEL addr %s psm 0x%x mtu %u", bd_addr_to_str(address), psm, mtu);
766 
767     // alloc structure
768     l2cap_channel_t * chan = btstack_memory_l2cap_channel_get();
769     if (!chan) {
770         return BTSTACK_MEMORY_ALLOC_FAILED;
771     }
772 
773      // Init memory (make valgrind happy)
774     memset(chan, 0, sizeof(l2cap_channel_t));
775     // limit local mtu to max acl packet length - l2cap header
776     if (mtu > l2cap_max_mtu()) {
777         mtu = l2cap_max_mtu();
778     }
779 
780     // fill in
781     BD_ADDR_COPY(chan->address, address);
782     chan->psm = psm;
783     chan->handle = 0;
784     chan->packet_handler = channel_packet_handler;
785     chan->remote_mtu = L2CAP_MINIMAL_MTU;
786     chan->local_mtu = mtu;
787     chan->local_cid = l2cap_next_local_cid();
788 
789     // set initial state
790     chan->state = L2CAP_STATE_WILL_SEND_CREATE_CONNECTION;
791     chan->state_var = L2CAP_CHANNEL_STATE_VAR_NONE;
792     chan->remote_sig_id = L2CAP_SIG_ID_INVALID;
793     chan->local_sig_id = L2CAP_SIG_ID_INVALID;
794     chan->required_security_level = LEVEL_0;
795 
796     // add to connections list
797     btstack_linked_list_add(&l2cap_channels, (btstack_linked_item_t *) chan);
798 
799     // store local_cid
800     if (out_local_cid){
801        *out_local_cid = chan->local_cid;
802     }
803 
804     // check if hci connection is already usable
805     hci_connection_t * conn = hci_connection_for_bd_addr_and_type(address, BD_ADDR_TYPE_CLASSIC);
806     if (conn){
807         log_info("l2cap_create_channel, hci connection already exists");
808         l2cap_handle_connection_complete(conn->con_handle, chan);
809         // check if remote supported fearures are already received
810         if (conn->bonding_flags & BONDING_RECEIVED_REMOTE_FEATURES) {
811             l2cap_handle_remote_supported_features_received(chan);
812         }
813     }
814 
815     l2cap_run();
816 
817     return 0;
818 }
819 
820 void
821 l2cap_disconnect(uint16_t local_cid, uint8_t reason){
822     log_info("L2CAP_DISCONNECT local_cid 0x%x reason 0x%x", local_cid, reason);
823     // find channel for local_cid
824     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
825     if (channel) {
826         channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST;
827     }
828     // process
829     l2cap_run();
830 }
831 
832 static void l2cap_handle_connection_failed_for_addr(bd_addr_t address, uint8_t status){
833     btstack_linked_list_iterator_t it;
834     btstack_linked_list_iterator_init(&it, &l2cap_channels);
835     while (btstack_linked_list_iterator_has_next(&it)){
836         l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
837         if ( BD_ADDR_CMP( channel->address, address) != 0) continue;
838         // channel for this address found
839         switch (channel->state){
840             case L2CAP_STATE_WAIT_CONNECTION_COMPLETE:
841             case L2CAP_STATE_WILL_SEND_CREATE_CONNECTION:
842                 // failure, forward error code
843                 l2cap_emit_channel_opened(channel, status);
844                 // discard channel
845                 l2cap_stop_rtx(channel);
846                 btstack_linked_list_iterator_remove(&it);
847                 btstack_memory_l2cap_channel_free(channel);
848                 break;
849             default:
850                 break;
851         }
852     }
853 }
854 
855 static void l2cap_handle_connection_success_for_addr(bd_addr_t address, hci_con_handle_t handle){
856     btstack_linked_list_iterator_t it;
857     btstack_linked_list_iterator_init(&it, &l2cap_channels);
858     while (btstack_linked_list_iterator_has_next(&it)){
859         l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
860         if ( ! BD_ADDR_CMP( channel->address, address) ){
861             l2cap_handle_connection_complete(handle, channel);
862         }
863     }
864     // process
865     l2cap_run();
866 }
867 
868 static void l2cap_notify_channel_can_send(void){
869     btstack_linked_list_iterator_t it;
870     btstack_linked_list_iterator_init(&it, &l2cap_channels);
871     while (btstack_linked_list_iterator_has_next(&it)){
872         l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
873         if (!channel->waiting_for_can_send_now) continue;
874         if (!hci_can_send_acl_packet_now(channel->handle)) continue;
875         channel->waiting_for_can_send_now = 0;
876         l2cap_emit_can_send_now(channel);
877     }
878 }
879 
880 static void l2cap_hci_event_handler(uint8_t packet_type, uint16_t cid, uint8_t *packet, uint16_t size){
881 
882     bd_addr_t address;
883     hci_con_handle_t handle;
884     btstack_linked_list_iterator_t it;
885     int hci_con_used;
886 
887     switch(packet[0]){
888 
889         // handle connection complete events
890         case HCI_EVENT_CONNECTION_COMPLETE:
891             bt_flip_addr(address, &packet[5]);
892             if (packet[2] == 0){
893                 handle = little_endian_read_16(packet, 3);
894                 l2cap_handle_connection_success_for_addr(address, handle);
895             } else {
896                 l2cap_handle_connection_failed_for_addr(address, packet[2]);
897             }
898             break;
899 
900         // handle successful create connection cancel command
901         case HCI_EVENT_COMMAND_COMPLETE:
902             if ( COMMAND_COMPLETE_EVENT(packet, hci_create_connection_cancel) ) {
903                 if (packet[5] == 0){
904                     bt_flip_addr(address, &packet[6]);
905                     // CONNECTION TERMINATED BY LOCAL HOST (0X16)
906                     l2cap_handle_connection_failed_for_addr(address, 0x16);
907                 }
908             }
909             l2cap_run();    // try sending signaling packets first
910             break;
911 
912         case HCI_EVENT_COMMAND_STATUS:
913             l2cap_run();    // try sending signaling packets first
914             break;
915 
916         // handle disconnection complete events
917         case HCI_EVENT_DISCONNECTION_COMPLETE:
918             // send l2cap disconnect events for all channels on this handle and free them
919             handle = little_endian_read_16(packet, 3);
920             btstack_linked_list_iterator_init(&it, &l2cap_channels);
921             while (btstack_linked_list_iterator_has_next(&it)){
922                 l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
923                 if (channel->handle != handle) continue;
924                 l2cap_emit_channel_closed(channel);
925                 l2cap_stop_rtx(channel);
926                 btstack_linked_list_iterator_remove(&it);
927                 btstack_memory_l2cap_channel_free(channel);
928             }
929             break;
930 
931         // Notify channel packet handler if they can send now
932         case DAEMON_EVENT_HCI_PACKET_SENT:
933         case HCI_EVENT_NUMBER_OF_COMPLETED_PACKETS:
934             l2cap_run();    // try sending signaling packets first
935             l2cap_notify_channel_can_send();
936             break;
937 
938         // HCI Connection Timeouts
939         case L2CAP_EVENT_TIMEOUT_CHECK:
940             handle = little_endian_read_16(packet, 2);
941             if (gap_get_connection_type(handle) != GAP_CONNECTION_ACL) break;
942             if (hci_authentication_active_for_handle(handle)) break;
943             hci_con_used = 0;
944             btstack_linked_list_iterator_init(&it, &l2cap_channels);
945             while (btstack_linked_list_iterator_has_next(&it)){
946                 l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
947                 if (channel->handle != handle) continue;
948                 hci_con_used = 1;
949                 break;
950             }
951             if (hci_con_used) break;
952             if (!hci_can_send_command_packet_now()) break;
953             hci_send_cmd(&hci_disconnect, handle, 0x13); // remote closed connection
954             break;
955 
956         case HCI_EVENT_READ_REMOTE_SUPPORTED_FEATURES_COMPLETE:
957             handle = little_endian_read_16(packet, 3);
958             btstack_linked_list_iterator_init(&it, &l2cap_channels);
959             while (btstack_linked_list_iterator_has_next(&it)){
960                 l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
961                 if (channel->handle != handle) continue;
962                 l2cap_handle_remote_supported_features_received(channel);
963                 break;
964             }
965             break;
966 
967         case GAP_EVENT_SECURITY_LEVEL:
968             handle = little_endian_read_16(packet, 2);
969             log_info("l2cap - security level update");
970             btstack_linked_list_iterator_init(&it, &l2cap_channels);
971             while (btstack_linked_list_iterator_has_next(&it)){
972                 l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
973                 if (channel->handle != handle) continue;
974 
975                 log_info("l2cap - state %u", channel->state);
976 
977                 gap_security_level_t actual_level = (gap_security_level_t) packet[4];
978                 gap_security_level_t required_level = channel->required_security_level;
979 
980                 switch (channel->state){
981                     case L2CAP_STATE_WAIT_INCOMING_SECURITY_LEVEL_UPDATE:
982                         if (actual_level >= required_level){
983                             channel->state = L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT;
984                             l2cap_emit_connection_request(channel);
985                         } else {
986                             channel->reason = 0x0003; // security block
987                             channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE;
988                         }
989                         break;
990 
991                     case L2CAP_STATE_WAIT_OUTGOING_SECURITY_LEVEL_UPDATE:
992                         if (actual_level >= required_level){
993                             channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST;
994                         } else {
995                             // disconnnect, authentication not good enough
996                             hci_disconnect_security_block(handle);
997                         }
998                         break;
999 
1000                     default:
1001                         break;
1002                 }
1003             }
1004             break;
1005 
1006         default:
1007             break;
1008     }
1009 
1010     l2cap_run();
1011 }
1012 
1013 static void l2cap_handle_disconnect_request(l2cap_channel_t *channel, uint16_t identifier){
1014     channel->remote_sig_id = identifier;
1015     channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE;
1016     l2cap_run();
1017 }
1018 
1019 static void l2cap_register_signaling_response(hci_con_handle_t handle, uint8_t code, uint8_t sig_id, uint16_t data){
1020     // Vol 3, Part A, 4.3: "The DCID and SCID fields shall be ignored when the result field indi- cates the connection was refused."
1021     if (signaling_responses_pending < NR_PENDING_SIGNALING_RESPONSES) {
1022         signaling_responses[signaling_responses_pending].handle = handle;
1023         signaling_responses[signaling_responses_pending].code = code;
1024         signaling_responses[signaling_responses_pending].sig_id = sig_id;
1025         signaling_responses[signaling_responses_pending].data = data;
1026         signaling_responses_pending++;
1027         l2cap_run();
1028     }
1029 }
1030 
1031 static void l2cap_handle_connection_request(hci_con_handle_t handle, uint8_t sig_id, uint16_t psm, uint16_t source_cid){
1032 
1033     // log_info("l2cap_handle_connection_request for handle %u, psm %u cid 0x%02x", handle, psm, source_cid);
1034     l2cap_service_t *service = l2cap_get_service(psm);
1035     if (!service) {
1036         // 0x0002 PSM not supported
1037         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0002);
1038         return;
1039     }
1040 
1041     hci_connection_t * hci_connection = hci_connection_for_handle( handle );
1042     if (!hci_connection) {
1043         //
1044         log_error("no hci_connection for handle %u", handle);
1045         return;
1046     }
1047 
1048     // alloc structure
1049     // log_info("l2cap_handle_connection_request register channel");
1050     l2cap_channel_t * channel = btstack_memory_l2cap_channel_get();
1051     if (!channel){
1052         // 0x0004 No resources available
1053         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0004);
1054         return;
1055     }
1056     // Init memory (make valgrind happy)
1057     memset(channel, 0, sizeof(l2cap_channel_t));
1058     // fill in
1059     BD_ADDR_COPY(channel->address, hci_connection->address);
1060     channel->psm = psm;
1061     channel->handle = handle;
1062     channel->packet_handler = service->packet_handler;
1063     channel->local_cid  = l2cap_next_local_cid();
1064     channel->remote_cid = source_cid;
1065     channel->local_mtu  = service->mtu;
1066     channel->remote_mtu = L2CAP_DEFAULT_MTU;
1067     channel->remote_sig_id = sig_id;
1068     channel->required_security_level = service->required_security_level;
1069 
1070     // limit local mtu to max acl packet length - l2cap header
1071     if (channel->local_mtu > l2cap_max_mtu()) {
1072         channel->local_mtu = l2cap_max_mtu();
1073     }
1074 
1075     // set initial state
1076     channel->state =     L2CAP_STATE_WAIT_INCOMING_SECURITY_LEVEL_UPDATE;
1077     channel->state_var = L2CAP_CHANNEL_STATE_VAR_SEND_CONN_RESP_PEND;
1078 
1079     // add to connections list
1080     btstack_linked_list_add(&l2cap_channels, (btstack_linked_item_t *) channel);
1081 
1082     // assert security requirements
1083     gap_request_security_level(handle, channel->required_security_level);
1084 }
1085 
1086 void l2cap_accept_connection(uint16_t local_cid){
1087     log_info("L2CAP_ACCEPT_CONNECTION local_cid 0x%x", local_cid);
1088     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
1089     if (!channel) {
1090         log_error("l2cap_accept_connection called but local_cid 0x%x not found", local_cid);
1091         return;
1092     }
1093 
1094     channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT;
1095 
1096     // process
1097     l2cap_run();
1098 }
1099 
1100 void l2cap_decline_connection(uint16_t local_cid, uint8_t reason){
1101     log_info("L2CAP_DECLINE_CONNECTION local_cid 0x%x, reason %x", local_cid, reason);
1102     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid( local_cid);
1103     if (!channel) {
1104         log_error( "l2cap_decline_connection called but local_cid 0x%x not found", local_cid);
1105         return;
1106     }
1107     channel->state  = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE;
1108     channel->reason = reason;
1109     l2cap_run();
1110 }
1111 
1112 static void l2cap_signaling_handle_configure_request(l2cap_channel_t *channel, uint8_t *command){
1113 
1114     channel->remote_sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
1115 
1116     uint16_t flags = little_endian_read_16(command, 6);
1117     if (flags & 1) {
1118         channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_CONT);
1119     }
1120 
1121     // accept the other's configuration options
1122     uint16_t end_pos = 4 + little_endian_read_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
1123     uint16_t pos     = 8;
1124     while (pos < end_pos){
1125         uint8_t option_hint = command[pos] >> 7;
1126         uint8_t option_type = command[pos] & 0x7f;
1127         log_info("l2cap cid %u, hint %u, type %u", channel->local_cid, option_hint, option_type);
1128         pos++;
1129         uint8_t length = command[pos++];
1130         // MTU { type(8): 1, len(8):2, MTU(16) }
1131         if (option_type == 1 && length == 2){
1132             channel->remote_mtu = little_endian_read_16(command, pos);
1133             // log_info("l2cap cid 0x%02x, remote mtu %u", channel->local_cid, channel->remote_mtu);
1134             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_MTU);
1135         }
1136         // Flush timeout { type(8):2, len(8): 2, Flush Timeout(16)}
1137         if (option_type == 2 && length == 2){
1138             channel->flush_timeout = little_endian_read_16(command, pos);
1139         }
1140         // check for unknown options
1141         if (option_hint == 0 && (option_type == 0 || option_type >= 0x07)){
1142             log_info("l2cap cid %u, unknown options", channel->local_cid);
1143             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_INVALID);
1144         }
1145         pos += length;
1146     }
1147 }
1148 
1149 static int l2cap_channel_ready_for_open(l2cap_channel_t *channel){
1150     // log_info("l2cap_channel_ready_for_open 0x%02x", channel->state_var);
1151     if ((channel->state_var & L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_RSP) == 0) return 0;
1152     if ((channel->state_var & L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP) == 0) return 0;
1153     // addition check that fixes re-entrance issue causing l2cap event channel opened twice
1154     if (channel->state == L2CAP_STATE_OPEN) return 0;
1155     return 1;
1156 }
1157 
1158 
1159 static void l2cap_signaling_handler_channel(l2cap_channel_t *channel, uint8_t *command){
1160 
1161     uint8_t  code       = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
1162     uint8_t  identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
1163     uint16_t result = 0;
1164 
1165     log_info("L2CAP signaling handler code %u, state %u", code, channel->state);
1166 
1167     // handle DISCONNECT REQUESTS seperately
1168     if (code == DISCONNECTION_REQUEST){
1169         switch (channel->state){
1170             case L2CAP_STATE_CONFIG:
1171             case L2CAP_STATE_OPEN:
1172             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
1173             case L2CAP_STATE_WAIT_DISCONNECT:
1174                 l2cap_handle_disconnect_request(channel, identifier);
1175                 break;
1176 
1177             default:
1178                 // ignore in other states
1179                 break;
1180         }
1181         return;
1182     }
1183 
1184     // @STATEMACHINE(l2cap)
1185     switch (channel->state) {
1186 
1187         case L2CAP_STATE_WAIT_CONNECT_RSP:
1188             switch (code){
1189                 case CONNECTION_RESPONSE:
1190                     l2cap_stop_rtx(channel);
1191                     result = little_endian_read_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
1192                     switch (result) {
1193                         case 0:
1194                             // successful connection
1195                             channel->remote_cid = little_endian_read_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
1196                             channel->state = L2CAP_STATE_CONFIG;
1197                             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
1198                             break;
1199                         case 1:
1200                             // connection pending. get some coffee, but start the ERTX
1201                             l2cap_start_ertx(channel);
1202                             break;
1203                         default:
1204                             // channel closed
1205                             channel->state = L2CAP_STATE_CLOSED;
1206                             // map l2cap connection response result to BTstack status enumeration
1207                             l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result);
1208 
1209                             // drop link key if security block
1210                             if (L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result == L2CAP_CONNECTION_RESPONSE_RESULT_REFUSED_SECURITY){
1211                                 hci_drop_link_key_for_bd_addr(channel->address);
1212                             }
1213 
1214                             // discard channel
1215                             btstack_linked_list_remove(&l2cap_channels, (btstack_linked_item_t *) channel);
1216                             btstack_memory_l2cap_channel_free(channel);
1217                             break;
1218                     }
1219                     break;
1220 
1221                 default:
1222                     //@TODO: implement other signaling packets
1223                     break;
1224             }
1225             break;
1226 
1227         case L2CAP_STATE_CONFIG:
1228             result = little_endian_read_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
1229             switch (code) {
1230                 case CONFIGURE_REQUEST:
1231                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP);
1232                     l2cap_signaling_handle_configure_request(channel, command);
1233                     if (!(channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_CONT)){
1234                         // only done if continuation not set
1235                         channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_REQ);
1236                     }
1237                     break;
1238                 case CONFIGURE_RESPONSE:
1239                     l2cap_stop_rtx(channel);
1240                     switch (result){
1241                         case 0: // success
1242                             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_RSP);
1243                             break;
1244                         case 4: // pending
1245                             l2cap_start_ertx(channel);
1246                             break;
1247                         default:
1248                             // retry on negative result
1249                             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
1250                             break;
1251                     }
1252                     break;
1253                 default:
1254                     break;
1255             }
1256             if (l2cap_channel_ready_for_open(channel)){
1257                 // for open:
1258                 channel->state = L2CAP_STATE_OPEN;
1259                 l2cap_emit_channel_opened(channel, 0);
1260             }
1261             break;
1262 
1263         case L2CAP_STATE_WAIT_DISCONNECT:
1264             switch (code) {
1265                 case DISCONNECTION_RESPONSE:
1266                     l2cap_finialize_channel_close(channel);
1267                     break;
1268                 default:
1269                     //@TODO: implement other signaling packets
1270                     break;
1271             }
1272             break;
1273 
1274         case L2CAP_STATE_CLOSED:
1275             // @TODO handle incoming requests
1276             break;
1277 
1278         case L2CAP_STATE_OPEN:
1279             //@TODO: implement other signaling packets, e.g. re-configure
1280             break;
1281         default:
1282             break;
1283     }
1284     // log_info("new state %u", channel->state);
1285 }
1286 
1287 
1288 static void l2cap_signaling_handler_dispatch( hci_con_handle_t handle, uint8_t * command){
1289 
1290     // get code, signalind identifier and command len
1291     uint8_t code   = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
1292     uint8_t sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
1293 
1294     // not for a particular channel, and not CONNECTION_REQUEST, ECHO_[REQUEST|RESPONSE], INFORMATION_REQUEST
1295     if (code < 1 || code == ECHO_RESPONSE || code > INFORMATION_REQUEST){
1296         l2cap_register_signaling_response(handle, COMMAND_REJECT, sig_id, L2CAP_REJ_CMD_UNKNOWN);
1297         return;
1298     }
1299 
1300     // general commands without an assigned channel
1301     switch(code) {
1302 
1303         case CONNECTION_REQUEST: {
1304             uint16_t psm =        little_endian_read_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
1305             uint16_t source_cid = little_endian_read_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+2);
1306             l2cap_handle_connection_request(handle, sig_id, psm, source_cid);
1307             return;
1308         }
1309 
1310         case ECHO_REQUEST:
1311             l2cap_register_signaling_response(handle, code, sig_id, 0);
1312             return;
1313 
1314         case INFORMATION_REQUEST: {
1315             uint16_t infoType = little_endian_read_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
1316             l2cap_register_signaling_response(handle, code, sig_id, infoType);
1317             return;
1318         }
1319 
1320         default:
1321             break;
1322     }
1323 
1324 
1325     // Get potential destination CID
1326     uint16_t dest_cid = little_endian_read_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
1327 
1328     // Find channel for this sig_id and connection handle
1329     btstack_linked_list_iterator_t it;
1330     btstack_linked_list_iterator_init(&it, &l2cap_channels);
1331     while (btstack_linked_list_iterator_has_next(&it)){
1332         l2cap_channel_t * channel = (l2cap_channel_t *) btstack_linked_list_iterator_next(&it);
1333         if (channel->handle != handle) continue;
1334         if (code & 1) {
1335             // match odd commands (responses) by previous signaling identifier
1336             if (channel->local_sig_id == sig_id) {
1337                 l2cap_signaling_handler_channel(channel, command);
1338                 break;
1339             }
1340         } else {
1341             // match even commands (requests) by local channel id
1342             if (channel->local_cid == dest_cid) {
1343                 l2cap_signaling_handler_channel(channel, command);
1344                 break;
1345             }
1346         }
1347     }
1348 }
1349 
1350 static void l2cap_acl_handler(uint8_t packet_type, uint8_t *packet, uint16_t size ){
1351 
1352     // Get Channel ID
1353     uint16_t channel_id = READ_L2CAP_CHANNEL_ID(packet);
1354     hci_con_handle_t handle = READ_ACL_CONNECTION_HANDLE(packet);
1355 
1356     switch (channel_id) {
1357 
1358         case L2CAP_CID_SIGNALING: {
1359 
1360             uint16_t command_offset = 8;
1361             while (command_offset < size) {
1362 
1363                 // handle signaling commands
1364                 l2cap_signaling_handler_dispatch(handle, &packet[command_offset]);
1365 
1366                 // increment command_offset
1367                 command_offset += L2CAP_SIGNALING_COMMAND_DATA_OFFSET + little_endian_read_16(packet, command_offset + L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
1368             }
1369             break;
1370         }
1371 
1372         case L2CAP_CID_ATTRIBUTE_PROTOCOL:
1373             if (fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_INDEX_ATTRIBUTE_PROTOCOL].callback) {
1374                 (*fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_INDEX_ATTRIBUTE_PROTOCOL].callback)(ATT_DATA_PACKET, handle, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1375             }
1376             break;
1377 
1378         case L2CAP_CID_SECURITY_MANAGER_PROTOCOL:
1379             if (fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_INDEX_SECURITY_MANAGER_PROTOCOL].callback) {
1380                 (*fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_INDEX_SECURITY_MANAGER_PROTOCOL].callback)(SM_DATA_PACKET, handle, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1381             }
1382             break;
1383 
1384         case L2CAP_CID_CONNECTIONLESS_CHANNEL:
1385             if (fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_INDEX_CONNECTIONLESS_CHANNEL].callback) {
1386                 (*fixed_channels[L2CAP_FIXED_CHANNEL_TABLE_INDEX_CONNECTIONLESS_CHANNEL].callback)(UCD_DATA_PACKET, handle, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1387             }
1388             break;
1389 
1390         case L2CAP_CID_SIGNALING_LE: {
1391             switch (packet[8]){
1392                 case CONNECTION_PARAMETER_UPDATE_RESPONSE: {
1393                     uint16_t result = little_endian_read_16(packet, 12);
1394                     l2cap_emit_connection_parameter_update_response(handle, result);
1395                     break;
1396                 }
1397                 case CONNECTION_PARAMETER_UPDATE_REQUEST: {
1398                     uint8_t event[10];
1399                     event[0] = L2CAP_EVENT_CONNECTION_PARAMETER_UPDATE_REQUEST;
1400                     event[1] = 8;
1401                     memcpy(&event[2], &packet[12], 8);
1402 
1403                     hci_connection_t * connection = hci_connection_for_handle(handle);
1404                     if (connection){
1405                         if (connection->role != HCI_ROLE_MASTER){
1406                             // reject command without notifying upper layer when not in master role
1407                             uint8_t sig_id = packet[COMPLETE_L2CAP_HEADER + 1];
1408                             l2cap_register_signaling_response(handle, COMMAND_REJECT_LE, sig_id, L2CAP_REJ_CMD_UNKNOWN);
1409                             break;
1410                         }
1411                         int update_parameter = 1;
1412                         le_connection_parameter_range_t existing_range;
1413                         gap_le_get_connection_parameter_range(existing_range);
1414                         uint16_t le_conn_interval_min = little_endian_read_16(packet,12);
1415                         uint16_t le_conn_interval_max = little_endian_read_16(packet,14);
1416                         uint16_t le_conn_latency = little_endian_read_16(packet,16);
1417                         uint16_t le_supervision_timeout = little_endian_read_16(packet,18);
1418 
1419                         if (le_conn_interval_min < existing_range.le_conn_interval_min) update_parameter = 0;
1420                         if (le_conn_interval_max > existing_range.le_conn_interval_max) update_parameter = 0;
1421 
1422                         if (le_conn_latency < existing_range.le_conn_latency_min) update_parameter = 0;
1423                         if (le_conn_latency > existing_range.le_conn_latency_max) update_parameter = 0;
1424 
1425                         if (le_supervision_timeout < existing_range.le_supervision_timeout_min) update_parameter = 0;
1426                         if (le_supervision_timeout > existing_range.le_supervision_timeout_max) update_parameter = 0;
1427 
1428                         if (update_parameter){
1429                             connection->le_con_parameter_update_state = CON_PARAMETER_UPDATE_SEND_RESPONSE;
1430                             connection->le_conn_interval_min = le_conn_interval_min;
1431                             connection->le_conn_interval_max = le_conn_interval_max;
1432                             connection->le_conn_latency = le_conn_latency;
1433                             connection->le_supervision_timeout = le_supervision_timeout;
1434                         } else {
1435                             connection->le_con_parameter_update_state = CON_PARAMETER_UPDATE_DENY;
1436                         }
1437                         connection->le_con_param_update_identifier = packet[COMPLETE_L2CAP_HEADER + 1];
1438                     }
1439 
1440                     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
1441                     if (!l2cap_event_packet_handler) break;
1442                     (*l2cap_event_packet_handler)( HCI_EVENT_PACKET, 0, event, sizeof(event));
1443                     break;
1444                 }
1445                 default: {
1446                     uint8_t sig_id = packet[COMPLETE_L2CAP_HEADER + 1];
1447                     l2cap_register_signaling_response(handle, COMMAND_REJECT_LE, sig_id, L2CAP_REJ_CMD_UNKNOWN);
1448                     break;
1449                 }
1450             }
1451             break;
1452         }
1453 
1454         default: {
1455             // Find channel for this channel_id and connection handle
1456             l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(channel_id);
1457             if (channel) {
1458                 l2cap_dispatch_to_channel(channel, L2CAP_DATA_PACKET, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1459             }
1460             break;
1461         }
1462     }
1463 
1464     l2cap_run();
1465 }
1466 
1467 // finalize closed channel - l2cap_handle_disconnect_request & DISCONNECTION_RESPONSE
1468 void l2cap_finialize_channel_close(l2cap_channel_t *channel){
1469     channel->state = L2CAP_STATE_CLOSED;
1470     l2cap_emit_channel_closed(channel);
1471     // discard channel
1472     l2cap_stop_rtx(channel);
1473     btstack_linked_list_remove(&l2cap_channels, (btstack_linked_item_t *) channel);
1474     btstack_memory_l2cap_channel_free(channel);
1475 }
1476 
1477 static l2cap_service_t * l2cap_get_service_internal(btstack_linked_list_t * services, uint16_t psm){
1478     btstack_linked_list_iterator_t it;
1479     btstack_linked_list_iterator_init(&it, services);
1480     while (btstack_linked_list_iterator_has_next(&it)){
1481         l2cap_service_t * service = (l2cap_service_t *) btstack_linked_list_iterator_next(&it);
1482         if ( service->psm == psm){
1483             return service;
1484         };
1485     }
1486     return NULL;
1487 }
1488 
1489 static inline l2cap_service_t * l2cap_get_service(uint16_t psm){
1490     return l2cap_get_service_internal(&l2cap_services, psm);
1491 }
1492 
1493 
1494 uint8_t l2cap_register_service(btstack_packet_handler_t service_packet_handler, uint16_t psm, uint16_t mtu, gap_security_level_t security_level){
1495 
1496     log_info("L2CAP_REGISTER_SERVICE psm 0x%x mtu %u", psm, mtu);
1497 
1498     // check for alread registered psm
1499     // TODO: emit error event
1500     l2cap_service_t *service = l2cap_get_service(psm);
1501     if (service) {
1502         log_error("l2cap_register_service: PSM %u already registered", psm);
1503         return L2CAP_SERVICE_ALREADY_REGISTERED;
1504     }
1505 
1506     // alloc structure
1507     // TODO: emit error event
1508     service = btstack_memory_l2cap_service_get();
1509     if (!service) {
1510         log_error("l2cap_register_service: no memory for l2cap_service_t");
1511         return BTSTACK_MEMORY_ALLOC_FAILED;
1512     }
1513 
1514     // fill in
1515     service->psm = psm;
1516     service->mtu = mtu;
1517     service->packet_handler = service_packet_handler;
1518     service->required_security_level = security_level;
1519 
1520     // add to services list
1521     btstack_linked_list_add(&l2cap_services, (btstack_linked_item_t *) service);
1522 
1523     // enable page scan
1524     hci_connectable_control(1);
1525 
1526     return 0;
1527 }
1528 
1529 void l2cap_unregister_service(uint16_t psm){
1530 
1531     log_info("L2CAP_UNREGISTER_SERVICE psm 0x%x", psm);
1532 
1533     l2cap_service_t *service = l2cap_get_service(psm);
1534     if (!service) return;
1535     btstack_linked_list_remove(&l2cap_services, (btstack_linked_item_t *) service);
1536     btstack_memory_l2cap_service_free(service);
1537 
1538     // disable page scan when no services registered
1539     if (!btstack_linked_list_empty(&l2cap_services)) return;
1540     hci_connectable_control(0);
1541 }
1542 
1543 // Bluetooth 4.0 - allows to register handler for Attribute Protocol and Security Manager Protocol
1544 void l2cap_register_fixed_channel(btstack_packet_handler_t the_packet_handler, uint16_t channel_id) {
1545     int index = l2cap_fixed_channel_table_index_for_channel_id(channel_id);
1546     if (index < 0) return;
1547     fixed_channels[index].callback = the_packet_handler;
1548 }
1549 
1550 #ifdef ENABLE_BLE
1551 
1552 
1553 #if 0
1554 static inline l2cap_service_t * l2cap_le_get_service(uint16_t psm){
1555     return l2cap_get_service_internal(&l2cap_le_services, psm);
1556 }
1557 /**
1558  * @brief Regster L2CAP LE Credit Based Flow Control Mode service
1559  * @param
1560  */
1561 void l2cap_le_register_service(btstack_packet_handler_t packet_handler, uint16_t psm,
1562     uint16_t mtu, uint16_t mps, uint16_t initial_credits, gap_security_level_t security_level){
1563 
1564     log_info("L2CAP_LE_REGISTER_SERVICE psm 0x%x mtu %u connection %p", psm, mtu, connection);
1565 
1566     // check for alread registered psm
1567     // TODO: emit error event
1568     l2cap_service_t *service = l2cap_le_get_service(psm);
1569     if (service) {
1570         log_error("l2cap_le_register_service_internal: PSM %u already registered", psm);
1571         l2cap_emit_service_registered(connection, L2CAP_SERVICE_ALREADY_REGISTERED, psm);
1572         return;
1573     }
1574 
1575     // alloc structure
1576     // TODO: emit error event
1577     service = btstack_memory_l2cap_service_get();
1578     if (!service) {
1579         log_error("l2cap_register_service_internal: no memory for l2cap_service_t");
1580         l2cap_emit_service_registered(connection, BTSTACK_MEMORY_ALLOC_FAILED, psm);
1581         return;
1582     }
1583 
1584     // fill in
1585     service->psm = psm;
1586     service->mtu = mtu;
1587     service->mps = mps;
1588     service->packet_handler = packet_handler;
1589     service->required_security_level = security_level;
1590 
1591     // add to services list
1592     btstack_linked_list_add(&l2cap_le_services, (btstack_linked_item_t *) service);
1593 
1594     // done
1595     l2cap_emit_service_registered(connection, 0, psm);
1596 }
1597 
1598 void l2cap_le_unregister_service(uint16_t psm) {
1599 
1600     log_info("L2CAP_LE_UNREGISTER_SERVICE psm 0x%x", psm);
1601 
1602     l2cap_service_t *service = l2cap_le_get_service(psm);
1603     if (!service) return;
1604     btstack_linked_list_remove(&l2cap_le_services, (btstack_linked_item_t *) service);
1605     btstack_memory_l2cap_service_free(service);
1606 }
1607 #endif
1608 #endif
1609