xref: /btstack/src/l2cap.c (revision a00031e2154472f85be4622e7cee39f9589ab933)
1 /*
2  * Copyright (C) 2009-2012 by Matthias Ringwald
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the copyright holders nor the names of
14  *    contributors may be used to endorse or promote products derived
15  *    from this software without specific prior written permission.
16  * 4. Any redistribution, use, or modification is done solely for
17  *    personal benefit and not for any commercial purpose or for
18  *    monetary gain.
19  *
20  * THIS SOFTWARE IS PROVIDED BY MATTHIAS RINGWALD AND CONTRIBUTORS
21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
24  * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
26  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
27  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
30  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  *
33  * Please inquire about commercial licensing options at [email protected]
34  *
35  */
36 
37 /*
38  *  l2cap.c
39  *
40  *  Logical Link Control and Adaption Protocl (L2CAP)
41  *
42  *  Created by Matthias Ringwald on 5/16/09.
43  */
44 
45 #include "l2cap.h"
46 #include "hci.h"
47 #include "hci_dump.h"
48 #include "debug.h"
49 #include "btstack_memory.h"
50 
51 #include <stdarg.h>
52 #include <string.h>
53 
54 #include <stdio.h>
55 
56 // nr of buffered acl packets in outgoing queue to get max performance
57 #define NR_BUFFERED_ACL_PACKETS 3
58 
59 // used to cache l2cap rejects, echo, and informational requests
60 #define NR_PENDING_SIGNALING_RESPONSES 3
61 
62 // offsets for L2CAP SIGNALING COMMANDS
63 #define L2CAP_SIGNALING_COMMAND_CODE_OFFSET   0
64 #define L2CAP_SIGNALING_COMMAND_SIGID_OFFSET  1
65 #define L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET 2
66 #define L2CAP_SIGNALING_COMMAND_DATA_OFFSET   4
67 
68 static void null_packet_handler(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size);
69 static void l2cap_packet_handler(uint8_t packet_type, uint8_t *packet, uint16_t size);
70 
71 // used to cache l2cap rejects, echo, and informational requests
72 static l2cap_signaling_response_t signaling_responses[NR_PENDING_SIGNALING_RESPONSES];
73 static int signaling_responses_pending;
74 
75 static linked_list_t l2cap_channels = NULL;
76 static linked_list_t l2cap_services = NULL;
77 static void (*packet_handler) (void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size) = null_packet_handler;
78 static int new_credits_blocked = 0;
79 
80 static btstack_packet_handler_t attribute_protocol_packet_handler = NULL;
81 static btstack_packet_handler_t security_protocol_packet_handler = NULL;
82 
83 // prototypes
84 static void l2cap_finialize_channel_close(l2cap_channel_t *channel);
85 static l2cap_service_t * l2cap_get_service(uint16_t psm);
86 static void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status);
87 static void l2cap_emit_channel_closed(l2cap_channel_t *channel);
88 static void l2cap_emit_connection_request(l2cap_channel_t *channel);
89 static int l2cap_channel_ready_for_open(l2cap_channel_t *channel);
90 
91 
92 void l2cap_init(){
93     new_credits_blocked = 0;
94     signaling_responses_pending = 0;
95 
96     l2cap_channels = NULL;
97     l2cap_services = NULL;
98 
99     packet_handler = null_packet_handler;
100 
101     //
102     // register callback with HCI
103     //
104     hci_register_packet_handler(&l2cap_packet_handler);
105     hci_connectable_control(0); // no services yet
106 }
107 
108 
109 /** Register L2CAP packet handlers */
110 static void null_packet_handler(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
111 }
112 void l2cap_register_packet_handler(void (*handler)(void * connection, uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size)){
113     packet_handler = handler;
114 }
115 
116 //  notify client/protocol handler
117 void l2cap_dispatch(l2cap_channel_t *channel, uint8_t type, uint8_t * data, uint16_t size){
118     if (channel->packet_handler) {
119         (* (channel->packet_handler))(type, channel->local_cid, data, size);
120     } else {
121         (*packet_handler)(channel->connection, type, channel->local_cid, data, size);
122     }
123 }
124 
125 void l2cap_emit_channel_opened(l2cap_channel_t *channel, uint8_t status) {
126     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",
127              status, bd_addr_to_str(channel->address), channel->handle, channel->psm,
128              channel->local_cid, channel->remote_cid, channel->local_mtu, channel->remote_mtu, channel->flush_timeout);
129     uint8_t event[23];
130     event[0] = L2CAP_EVENT_CHANNEL_OPENED;
131     event[1] = sizeof(event) - 2;
132     event[2] = status;
133     bt_flip_addr(&event[3], channel->address);
134     bt_store_16(event,  9, channel->handle);
135     bt_store_16(event, 11, channel->psm);
136     bt_store_16(event, 13, channel->local_cid);
137     bt_store_16(event, 15, channel->remote_cid);
138     bt_store_16(event, 17, channel->local_mtu);
139     bt_store_16(event, 19, channel->remote_mtu);
140     bt_store_16(event, 19, channel->flush_timeout);
141     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
142     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
143 }
144 
145 void l2cap_emit_channel_closed(l2cap_channel_t *channel) {
146     log_info("L2CAP_EVENT_CHANNEL_CLOSED local_cid 0x%x", channel->local_cid);
147     uint8_t event[4];
148     event[0] = L2CAP_EVENT_CHANNEL_CLOSED;
149     event[1] = sizeof(event) - 2;
150     bt_store_16(event, 2, channel->local_cid);
151     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
152     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
153 }
154 
155 void l2cap_emit_connection_request(l2cap_channel_t *channel) {
156     log_info("L2CAP_EVENT_INCOMING_CONNECTION addr %s handle 0x%x psm 0x%x local_cid 0x%x remote_cid 0x%x",
157              bd_addr_to_str(channel->address), channel->handle,  channel->psm, channel->local_cid, channel->remote_cid);
158     uint8_t event[16];
159     event[0] = L2CAP_EVENT_INCOMING_CONNECTION;
160     event[1] = sizeof(event) - 2;
161     bt_flip_addr(&event[2], channel->address);
162     bt_store_16(event,  8, channel->handle);
163     bt_store_16(event, 10, channel->psm);
164     bt_store_16(event, 12, channel->local_cid);
165     bt_store_16(event, 14, channel->remote_cid);
166     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
167     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
168 }
169 
170 static void l2cap_emit_service_registered(void *connection, uint8_t status, uint16_t psm){
171     log_info("L2CAP_EVENT_SERVICE_REGISTERED status 0x%x psm 0x%x", status, psm);
172     uint8_t event[5];
173     event[0] = L2CAP_EVENT_SERVICE_REGISTERED;
174     event[1] = sizeof(event) - 2;
175     event[2] = status;
176     bt_store_16(event, 3, psm);
177     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
178     (*packet_handler)(connection, HCI_EVENT_PACKET, 0, event, sizeof(event));
179 }
180 
181 void l2cap_emit_credits(l2cap_channel_t *channel, uint8_t credits) {
182 
183     log_info("L2CAP_EVENT_CREDITS local_cid 0x%x credits %u", channel->local_cid, credits);
184     // track credits
185     channel->packets_granted += credits;
186 
187     uint8_t event[5];
188     event[0] = L2CAP_EVENT_CREDITS;
189     event[1] = sizeof(event) - 2;
190     bt_store_16(event, 2, channel->local_cid);
191     event[4] = credits;
192     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
193     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
194 }
195 
196 void l2cap_block_new_credits(uint8_t blocked){
197     new_credits_blocked = blocked;
198 }
199 
200 void l2cap_hand_out_credits(void){
201 
202     if (new_credits_blocked) return;    // we're told not to. used by daemon
203 
204     linked_item_t *it;
205     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
206         if (!hci_number_free_acl_slots()) return;
207         l2cap_channel_t * channel = (l2cap_channel_t *) it;
208         if (channel->state != L2CAP_STATE_OPEN) continue;
209         if (hci_number_outgoing_packets(channel->handle) < NR_BUFFERED_ACL_PACKETS && channel->packets_granted == 0) {
210             l2cap_emit_credits(channel, 1);
211         }
212     }
213 }
214 
215 l2cap_channel_t * l2cap_get_channel_for_local_cid(uint16_t local_cid){
216     linked_item_t *it;
217     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
218         l2cap_channel_t * channel = (l2cap_channel_t *) it;
219         if ( channel->local_cid == local_cid) {
220             return channel;
221         }
222     }
223     return NULL;
224 }
225 
226 int  l2cap_can_send_packet_now(uint16_t local_cid){
227     l2cap_channel_t *channel = l2cap_get_channel_for_local_cid(local_cid);
228     if (!channel) return 0;
229     if (!channel->packets_granted) return 0;
230     return hci_can_send_packet_now(HCI_ACL_DATA_PACKET);
231 }
232 
233 uint16_t l2cap_get_remote_mtu_for_local_cid(uint16_t local_cid){
234     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
235     if (channel) {
236         return channel->remote_mtu;
237     }
238     return 0;
239 }
240 
241 static l2cap_channel_t * l2cap_channel_for_rtx_timer(timer_source_t * ts){
242     linked_item_t *it;
243     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
244         l2cap_channel_t * channel = (l2cap_channel_t *) it;
245         if ( &channel->rtx == ts) {
246             return channel;
247         }
248     }
249     return NULL;
250 }
251 
252 static void l2cap_rtx_timeout(timer_source_t * ts){
253     l2cap_channel_t * channel = l2cap_channel_for_rtx_timer(ts);
254     if (!ts) return;
255 
256     log_info("l2cap_rtx_timeout for local cid 0x%02x", channel->local_cid);
257 
258     // "When terminating the channel, it is not necessary to send a L2CAP_DisconnectReq
259     //  and enter WAIT_DISCONNECT state. Channels can be transitioned directly to the CLOSED state."
260     // notify client
261     l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_RTX_TIMEOUT);
262 
263     // discard channel
264     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
265     btstack_memory_l2cap_channel_free(channel);
266 }
267 
268 static void l2cap_stop_rtx(l2cap_channel_t * channel){
269     log_info("l2cap_stop_rtx for local cid 0x%02x", channel->local_cid);
270     run_loop_remove_timer(&channel->rtx);
271 }
272 
273 static void l2cap_start_rtx(l2cap_channel_t * channel){
274     log_info("l2cap_start_rtx for local cid 0x%02x", channel->local_cid);
275     l2cap_stop_rtx(channel);
276     run_loop_set_timer_handler(&channel->rtx, l2cap_rtx_timeout);
277     run_loop_set_timer(&channel->rtx, L2CAP_RTX_TIMEOUT_MS);
278     run_loop_add_timer(&channel->rtx);
279 }
280 
281 static void l2cap_start_ertx(l2cap_channel_t * channel){
282     log_info("l2cap_start_ertx for local cid 0x%02x", channel->local_cid);
283     l2cap_stop_rtx(channel);
284     run_loop_set_timer_handler(&channel->rtx, l2cap_rtx_timeout);
285     run_loop_set_timer(&channel->rtx, L2CAP_ERTX_TIMEOUT_MS);
286     run_loop_add_timer(&channel->rtx);
287 }
288 
289 
290 int l2cap_send_signaling_packet(hci_con_handle_t handle, L2CAP_SIGNALING_COMMANDS cmd, uint8_t identifier, ...){
291 
292     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
293         log_info("l2cap_send_signaling_packet, cannot send\n");
294         return BTSTACK_ACL_BUFFERS_FULL;
295     }
296 
297     // log_info("l2cap_send_signaling_packet type %u\n", cmd);
298     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
299     va_list argptr;
300     va_start(argptr, identifier);
301     uint16_t len = l2cap_create_signaling_internal(acl_buffer, handle, cmd, identifier, argptr);
302     va_end(argptr);
303     // log_info("l2cap_send_signaling_packet con %u!\n", handle);
304     return hci_send_acl_packet(acl_buffer, len);
305 }
306 
307 uint8_t *l2cap_get_outgoing_buffer(void){
308     return hci_get_outgoing_acl_packet_buffer() + COMPLETE_L2CAP_HEADER; // 8 bytes
309 }
310 
311 int l2cap_send_prepared(uint16_t local_cid, uint16_t len){
312 
313     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
314         log_info("l2cap_send_internal cid 0x%02x, cannot send\n", local_cid);
315         return BTSTACK_ACL_BUFFERS_FULL;
316     }
317 
318     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
319     if (!channel) {
320         log_error("l2cap_send_internal no channel for cid 0x%02x\n", local_cid);
321         return -1;   // TODO: define error
322     }
323 
324     if (channel->packets_granted == 0){
325         log_error("l2cap_send_internal cid 0x%02x, no credits!\n", local_cid);
326         return -1;  // TODO: define error
327     }
328 
329     --channel->packets_granted;
330 
331     log_debug("l2cap_send_internal cid 0x%02x, handle %u, 1 credit used, credits left %u;\n",
332                   local_cid, channel->handle, channel->packets_granted);
333 
334     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
335 
336     // 0 - Connection handle : PB=10 : BC=00
337     bt_store_16(acl_buffer, 0, channel->handle | (2 << 12) | (0 << 14));
338     // 2 - ACL length
339     bt_store_16(acl_buffer, 2,  len + 4);
340     // 4 - L2CAP packet length
341     bt_store_16(acl_buffer, 4,  len + 0);
342     // 6 - L2CAP channel DEST
343     bt_store_16(acl_buffer, 6, channel->remote_cid);
344     // send
345     int err = hci_send_acl_packet(acl_buffer, len+8);
346 
347     l2cap_hand_out_credits();
348 
349     return err;
350 }
351 
352 int l2cap_send_prepared_connectionless(uint16_t handle, uint16_t cid, uint16_t len){
353 
354     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
355         log_info("l2cap_send_prepared_to_handle cid 0x%02x, cannot send\n", cid);
356         return BTSTACK_ACL_BUFFERS_FULL;
357     }
358 
359     log_debug("l2cap_send_prepared_to_handle cid 0x%02x, handle %u\n", cid, handle);
360 
361     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
362 
363     // 0 - Connection handle : PB=10 : BC=00
364     bt_store_16(acl_buffer, 0, handle | (2 << 12) | (0 << 14));
365     // 2 - ACL length
366     bt_store_16(acl_buffer, 2,  len + 4);
367     // 4 - L2CAP packet length
368     bt_store_16(acl_buffer, 4,  len + 0);
369     // 6 - L2CAP channel DEST
370     bt_store_16(acl_buffer, 6, cid);
371     // send
372     int err = hci_send_acl_packet(acl_buffer, len+8);
373 
374     l2cap_hand_out_credits();
375 
376     return err;
377 }
378 
379 int l2cap_send_internal(uint16_t local_cid, uint8_t *data, uint16_t len){
380 
381     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
382         log_info("l2cap_send_internal cid 0x%02x, cannot send\n", local_cid);
383         return BTSTACK_ACL_BUFFERS_FULL;
384     }
385 
386     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
387 
388     memcpy(&acl_buffer[8], data, len);
389 
390     return l2cap_send_prepared(local_cid, len);
391 }
392 
393 int l2cap_send_connectionless(uint16_t handle, uint16_t cid, uint8_t *data, uint16_t len){
394 
395     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
396         log_info("l2cap_send_internal cid 0x%02x, cannot send\n", cid);
397         return BTSTACK_ACL_BUFFERS_FULL;
398     }
399 
400     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
401 
402     memcpy(&acl_buffer[8], data, len);
403 
404     return l2cap_send_prepared_connectionless(handle, cid, len);
405 }
406 
407 static inline void channelStateVarSetFlag(l2cap_channel_t *channel, L2CAP_CHANNEL_STATE_VAR flag){
408     channel->state_var = (L2CAP_CHANNEL_STATE_VAR) (channel->state_var | flag);
409 }
410 
411 static inline void channelStateVarClearFlag(l2cap_channel_t *channel, L2CAP_CHANNEL_STATE_VAR flag){
412     channel->state_var = (L2CAP_CHANNEL_STATE_VAR) (channel->state_var & ~flag);
413 }
414 
415 
416 
417 // MARK: L2CAP_RUN
418 // process outstanding signaling tasks
419 void l2cap_run(void){
420 
421     // check pending signaling responses
422     while (signaling_responses_pending){
423 
424         if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)) break;
425 
426         hci_con_handle_t handle = signaling_responses[0].handle;
427         uint8_t sig_id = signaling_responses[0].sig_id;
428         uint16_t infoType = signaling_responses[0].data;    // INFORMATION_REQUEST
429         uint16_t result   = signaling_responses[0].data;    // CONNECTION_REQUEST, COMMAND_REJECT
430 
431         switch (signaling_responses[0].code){
432             case CONNECTION_REQUEST:
433                 l2cap_send_signaling_packet(handle, CONNECTION_RESPONSE, sig_id, 0, 0, result, 0);
434                 // also disconnect if result is 0x0003 - security blocked
435                 hci_disconnect_security_block(handle);
436                 break;
437             case ECHO_REQUEST:
438                 l2cap_send_signaling_packet(handle, ECHO_RESPONSE, sig_id, 0, NULL);
439                 break;
440             case INFORMATION_REQUEST:
441                 switch (infoType){
442                     case 1: { // Connectionless MTU
443                         uint16_t connectionless_mtu = hci_max_acl_data_packet_length();
444                         l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, sizeof(connectionless_mtu), &connectionless_mtu);
445                         break;
446                     }
447                     case 2: { // Extended Features Supported
448                         // extended features request supported, only supporing fixed channel map
449                         uint32_t features = 0x80;
450                         l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, sizeof(features), &features);
451                         break;
452                     }
453                     case 3: { // Fixed Channels Supported
454                         uint8_t map[8];
455                         memset(map, 0, 8);
456                         map[0] = 0x01;  // L2CAP Signaling Channel
457                         l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, sizeof(map), &map);
458                         break;
459                     }
460                     default:
461                         // all other types are not supported
462                         l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 1, 0, NULL);
463                         break;
464                 }
465                 break;
466             case COMMAND_REJECT:
467                 l2cap_send_signaling_packet(handle, COMMAND_REJECT, sig_id, result);
468                 break;
469             default:
470                 // should not happen
471                 break;
472         }
473 
474         // remove first item
475         signaling_responses_pending--;
476         int i;
477         for (i=0; i < signaling_responses_pending; i++){
478             memcpy(&signaling_responses[i], &signaling_responses[i+1], sizeof(l2cap_signaling_response_t));
479         }
480     }
481 
482     uint8_t  config_options[4];
483     linked_item_t *it;
484     linked_item_t *next;
485     for (it = (linked_item_t *) l2cap_channels; it ; it = next){
486         next = it->next;    // cache next item as current item might get freed
487 
488         if (!hci_can_send_packet_now(HCI_COMMAND_DATA_PACKET)) break;
489         if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)) break;
490 
491         l2cap_channel_t * channel = (l2cap_channel_t *) it;
492 
493         // log_info("l2cap_run: state %u, var 0x%02x\n", channel->state, channel->state_var);
494 
495 
496         switch (channel->state){
497 
498             case L2CAP_STATE_WAIT_SECURITY_LEVEL_UPDATE:
499             case L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT:
500                 if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONN_RESP_PEND) {
501                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONN_RESP_PEND);
502                     l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid, 1, 0);
503                 }
504                 break;
505 
506             case L2CAP_STATE_WILL_SEND_CREATE_CONNECTION:
507                 // send connection request - set state first
508                 channel->state = L2CAP_STATE_WAIT_CONNECTION_COMPLETE;
509                 // BD_ADDR, Packet_Type, Page_Scan_Repetition_Mode, Reserved, Clock_Offset, Allow_Role_Switch
510                 hci_send_cmd(&hci_create_connection, channel->address, hci_usable_acl_packet_types(), 0, 0, 0, 1);
511                 break;
512 
513             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE:
514                 l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, 0, 0, channel->reason, 0);
515                 // discard channel - l2cap_finialize_channel_close without sending l2cap close event
516                 linked_list_remove(&l2cap_channels, (linked_item_t *) channel); // -- remove from list
517                 btstack_memory_l2cap_channel_free(channel);
518                 break;
519 
520             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT:
521                 channel->state = L2CAP_STATE_CONFIG;
522                 channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
523                 l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid, 0, 0);
524                 break;
525 
526             case L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST:
527                 // success, start l2cap handshake
528                 channel->local_sig_id = l2cap_next_sig_id();
529                 channel->state = L2CAP_STATE_WAIT_CONNECT_RSP;
530                 l2cap_send_signaling_packet( channel->handle, CONNECTION_REQUEST, channel->local_sig_id, channel->psm, channel->local_cid);
531                 l2cap_start_rtx(channel);
532                 break;
533 
534             case L2CAP_STATE_CONFIG:
535                 if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP){
536                     uint16_t flags = 0;
537                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP);
538                     if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_CONT) {
539                         flags = 1;
540                     } else {
541                         channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP);
542                     }
543                     if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_INVALID){
544                         l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, flags, L2CAP_CONF_RESULT_UNKNOWN_OPTIONS, 0, NULL);
545                     } else if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_MTU){
546                         config_options[0] = 1; // MTU
547                         config_options[1] = 2; // len param
548                         bt_store_16( (uint8_t*)&config_options, 2, channel->remote_mtu);
549                         l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, flags, 0, 4, &config_options);
550                         channelStateVarClearFlag(channel,L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_MTU);
551                     } else {
552                         l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, flags, 0, 0, NULL);
553                     }
554                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_CONT);
555                 }
556                 else if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ){
557                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
558                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SENT_CONF_REQ);
559                     channel->local_sig_id = l2cap_next_sig_id();
560                     config_options[0] = 1; // MTU
561                     config_options[1] = 2; // len param
562                     bt_store_16( (uint8_t*)&config_options, 2, channel->local_mtu);
563                     l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->local_sig_id, channel->remote_cid, 0, 4, &config_options);
564                     l2cap_start_rtx(channel);
565                 }
566                 if (l2cap_channel_ready_for_open(channel)){
567                     channel->state = L2CAP_STATE_OPEN;
568                     l2cap_emit_channel_opened(channel, 0);  // success
569                     l2cap_emit_credits(channel, 1);
570                 }
571                 break;
572 
573             case L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE:
574                 l2cap_send_signaling_packet( channel->handle, DISCONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid);
575                 // 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 :)
576                 l2cap_finialize_channel_close(channel);  // -- remove from list
577                 break;
578 
579             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
580                 channel->local_sig_id = l2cap_next_sig_id();
581                 channel->state = L2CAP_STATE_WAIT_DISCONNECT;
582                 l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->local_sig_id, channel->remote_cid, channel->local_cid);
583                 break;
584             default:
585                 break;
586         }
587     }
588 }
589 
590 uint16_t l2cap_max_mtu(void){
591     return hci_max_acl_data_packet_length() - L2CAP_HEADER_SIZE;
592 }
593 
594 // open outgoing L2CAP channel
595 void l2cap_create_channel_internal(void * connection, btstack_packet_handler_t packet_handler,
596                                    bd_addr_t address, uint16_t psm, uint16_t mtu){
597 
598     log_info("L2CAP_CREATE_CHANNEL_MTU addr %s psm 0x%x mtu %u", bd_addr_to_str(address), psm, mtu);
599 
600     // alloc structure
601     l2cap_channel_t * chan = (l2cap_channel_t*) btstack_memory_l2cap_channel_get();
602     if (!chan) {
603         // emit error event
604         l2cap_channel_t dummy_channel;
605         BD_ADDR_COPY(dummy_channel.address, address);
606         dummy_channel.psm = psm;
607         l2cap_emit_channel_opened(&dummy_channel, BTSTACK_MEMORY_ALLOC_FAILED);
608         return;
609     }
610     // limit local mtu to max acl packet length
611     if (mtu > l2cap_max_mtu()) {
612         mtu = l2cap_max_mtu();
613     }
614 
615     // fill in
616     BD_ADDR_COPY(chan->address, address);
617     chan->psm = psm;
618     chan->handle = 0;
619     chan->connection = connection;
620     chan->packet_handler = packet_handler;
621     chan->remote_mtu = L2CAP_MINIMAL_MTU;
622     chan->local_mtu = mtu;
623     chan->packets_granted = 0;
624 
625     // set initial state
626     chan->state = L2CAP_STATE_WILL_SEND_CREATE_CONNECTION;
627     chan->state_var = L2CAP_CHANNEL_STATE_VAR_NONE;
628     chan->remote_sig_id = L2CAP_SIG_ID_INVALID;
629     chan->local_sig_id = L2CAP_SIG_ID_INVALID;
630 
631     // add to connections list
632     linked_list_add(&l2cap_channels, (linked_item_t *) chan);
633 
634     l2cap_run();
635 }
636 
637 void l2cap_disconnect_internal(uint16_t local_cid, uint8_t reason){
638     log_info("L2CAP_DISCONNECT local_cid 0x%x reason 0x%x", local_cid, reason);
639     // find channel for local_cid
640     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
641     if (channel) {
642         channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST;
643     }
644     // process
645     l2cap_run();
646 }
647 
648 static void l2cap_handle_connection_failed_for_addr(bd_addr_t address, uint8_t status){
649     linked_item_t *it = (linked_item_t *) &l2cap_channels;
650     while (it->next){
651         l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
652         if ( ! BD_ADDR_CMP( channel->address, address) ){
653             if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
654                 // failure, forward error code
655                 l2cap_emit_channel_opened(channel, status);
656                 // discard channel
657                 it->next = it->next->next;
658                 btstack_memory_l2cap_channel_free(channel);
659             }
660         } else {
661             it = it->next;
662         }
663     }
664 }
665 
666 static void l2cap_handle_connection_success_for_addr(bd_addr_t address, hci_con_handle_t handle){
667     linked_item_t *it;
668     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
669         l2cap_channel_t * channel = (l2cap_channel_t *) it;
670         if ( ! BD_ADDR_CMP( channel->address, address) ){
671             if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
672                 // success, start l2cap handshake
673                 channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST;
674                 channel->handle = handle;
675                 channel->local_cid = l2cap_next_local_cid();
676             }
677         }
678     }
679     // process
680     l2cap_run();
681 }
682 
683 void l2cap_event_handler( uint8_t *packet, uint16_t size ){
684 
685     bd_addr_t address;
686     hci_con_handle_t handle;
687     l2cap_channel_t * channel;
688     linked_item_t *it;
689     int hci_con_used;
690 
691     switch(packet[0]){
692 
693         // handle connection complete events
694         case HCI_EVENT_CONNECTION_COMPLETE:
695             bt_flip_addr(address, &packet[5]);
696             if (packet[2] == 0){
697                 handle = READ_BT_16(packet, 3);
698                 l2cap_handle_connection_success_for_addr(address, handle);
699             } else {
700                 l2cap_handle_connection_failed_for_addr(address, packet[2]);
701             }
702             break;
703 
704         // handle successful create connection cancel command
705         case HCI_EVENT_COMMAND_COMPLETE:
706             if ( COMMAND_COMPLETE_EVENT(packet, hci_create_connection_cancel) ) {
707                 if (packet[5] == 0){
708                     bt_flip_addr(address, &packet[6]);
709                     // CONNECTION TERMINATED BY LOCAL HOST (0X16)
710                     l2cap_handle_connection_failed_for_addr(address, 0x16);
711                 }
712             }
713             l2cap_run();    // try sending signaling packets first
714             break;
715 
716         case HCI_EVENT_COMMAND_STATUS:
717             l2cap_run();    // try sending signaling packets first
718             break;
719 
720         // handle disconnection complete events
721         case HCI_EVENT_DISCONNECTION_COMPLETE:
722             // send l2cap disconnect events for all channels on this handle
723             handle = READ_BT_16(packet, 3);
724             it = (linked_item_t *) &l2cap_channels;
725             while (it->next){
726                 l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
727                 if ( channel->handle == handle ){
728                     // update prev item before free'ing next element - don't call l2cap_finalize_channel_close
729                     it->next = it->next->next;
730                     l2cap_emit_channel_closed(channel);
731                     btstack_memory_l2cap_channel_free(channel);
732                 } else {
733                     it = it->next;
734                 }
735             }
736             break;
737 
738         case HCI_EVENT_NUMBER_OF_COMPLETED_PACKETS:
739             l2cap_run();    // try sending signaling packets first
740             l2cap_hand_out_credits();
741             break;
742 
743         // HCI Connection Timeouts
744         case L2CAP_EVENT_TIMEOUT_CHECK:
745             handle = READ_BT_16(packet, 2);
746             if (hci_authentication_active_for_handle(handle)) break;
747             hci_con_used = 0;
748             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
749                 channel = (l2cap_channel_t *) it;
750                 if (channel->handle == handle) {
751                     hci_con_used = 1;
752                 }
753             }
754             if (hci_con_used) break;
755             if (!hci_can_send_packet_now(HCI_COMMAND_DATA_PACKET)) break;
756             hci_send_cmd(&hci_disconnect, handle, 0x13); // remote closed connection
757             break;
758 
759         case DAEMON_EVENT_HCI_PACKET_SENT:
760             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
761                 channel = (l2cap_channel_t *) it;
762                 if (channel->packet_handler) {
763                     (* (channel->packet_handler))(HCI_EVENT_PACKET, channel->local_cid, packet, size);
764                 }
765             }
766             if (attribute_protocol_packet_handler) {
767                 (*attribute_protocol_packet_handler)(HCI_EVENT_PACKET, 0, packet, size);
768             }
769             if (security_protocol_packet_handler) {
770                 (*security_protocol_packet_handler)(HCI_EVENT_PACKET, 0, packet, size);
771             }
772             break;
773 
774         case GAP_SECURITY_LEVEL:
775             handle = READ_BT_16(packet, 2);
776             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
777                 channel = (l2cap_channel_t *) it;
778                 if (channel->handle != handle) continue;
779                 if (channel->state  != L2CAP_STATE_WAIT_SECURITY_LEVEL_UPDATE) continue;
780                 // @todo check security level again
781                 // channel->reason = 0x03; // security block
782                 // channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE;
783                 // success
784                 channel->state = L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT;
785                 l2cap_emit_connection_request(channel);
786             }
787             break;
788 
789         default:
790             break;
791     }
792 
793     // pass on
794     (*packet_handler)(NULL, HCI_EVENT_PACKET, 0, packet, size);
795 }
796 
797 static void l2cap_handle_disconnect_request(l2cap_channel_t *channel, uint16_t identifier){
798     channel->remote_sig_id = identifier;
799     channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE;
800     l2cap_run();
801 }
802 
803 static void l2cap_register_signaling_response(hci_con_handle_t handle, uint8_t code, uint8_t sig_id, uint16_t data){
804     // Vol 3, Part A, 4.3: "The DCID and SCID fields shall be ignored when the result field indi- cates the connection was refused."
805     if (signaling_responses_pending < NR_PENDING_SIGNALING_RESPONSES) {
806         signaling_responses[signaling_responses_pending].handle = handle;
807         signaling_responses[signaling_responses_pending].code = code;
808         signaling_responses[signaling_responses_pending].sig_id = sig_id;
809         signaling_responses[signaling_responses_pending].data = data;
810         signaling_responses_pending++;
811         l2cap_run();
812     }
813 }
814 
815 static void l2cap_handle_connection_request(hci_con_handle_t handle, uint8_t sig_id, uint16_t psm, uint16_t source_cid){
816 
817     // log_info("l2cap_handle_connection_request for handle %u, psm %u cid 0x%02x\n", handle, psm, source_cid);
818     l2cap_service_t *service = l2cap_get_service(psm);
819     if (!service) {
820         // 0x0002 PSM not supported
821         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0002);
822         return;
823     }
824 
825     hci_connection_t * hci_connection = hci_connection_for_handle( handle );
826     if (!hci_connection) {
827         //
828         log_error("no hci_connection for handle %u\n", handle);
829         return;
830     }
831 
832     // reject connection (0x03 security block) and disconnect if both have SSP, connection is not encrypted and PSM != SDP
833     if (psm != PSM_SDP
834         && hci_local_ssp_activated()
835         && hci_remote_ssp_supported(handle)
836         && gap_security_level(handle) == LEVEL_0){
837 
838         // 0x0003 Security Block
839         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0003);
840         return;
841     }
842 
843 
844     // alloc structure
845     // log_info("l2cap_handle_connection_request register channel\n");
846     l2cap_channel_t * channel = (l2cap_channel_t*) btstack_memory_l2cap_channel_get();
847     if (!channel){
848         // 0x0004 No resources available
849         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0004);
850         return;
851     }
852 
853     // fill in
854     BD_ADDR_COPY(channel->address, hci_connection->address);
855     channel->psm = psm;
856     channel->handle = handle;
857     channel->connection = service->connection;
858     channel->packet_handler = service->packet_handler;
859     channel->local_cid  = l2cap_next_local_cid();
860     channel->remote_cid = source_cid;
861     channel->local_mtu  = service->mtu;
862     channel->remote_mtu = L2CAP_DEFAULT_MTU;
863     channel->packets_granted = 0;
864     channel->remote_sig_id = sig_id;
865 
866     // limit local mtu to max acl packet length
867     if (channel->local_mtu > l2cap_max_mtu()) {
868         channel->local_mtu = l2cap_max_mtu();
869     }
870 
871     // set initial state
872     channel->state =     L2CAP_STATE_WAIT_SECURITY_LEVEL_UPDATE;
873     channel->state_var = L2CAP_CHANNEL_STATE_VAR_SEND_CONN_RESP_PEND;
874 
875     // add to connections list
876     linked_list_add(&l2cap_channels, (linked_item_t *) channel);
877 
878     // assert security requirements
879     gap_security_level_t required_level = LEVEL_0;
880     gap_request_security_level(handle, required_level);
881 }
882 
883 void l2cap_accept_connection_internal(uint16_t local_cid){
884     log_info("L2CAP_ACCEPT_CONNECTION local_cid 0x%x", local_cid);
885     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
886     if (!channel) {
887         log_error("l2cap_accept_connection_internal called but local_cid 0x%x not found", local_cid);
888         return;
889     }
890 
891     channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT;
892 
893     // process
894     l2cap_run();
895 }
896 
897 void l2cap_decline_connection_internal(uint16_t local_cid, uint8_t reason){
898     log_info("L2CAP_DECLINE_CONNECTION local_cid 0x%x, reason %x", local_cid, reason);
899     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid( local_cid);
900     if (!channel) {
901         log_error( "l2cap_decline_connection_internal called but local_cid 0x%x not found", local_cid);
902         return;
903     }
904     channel->state  = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE;
905     channel->reason = reason;
906     l2cap_run();
907 }
908 
909 void l2cap_signaling_handle_configure_request(l2cap_channel_t *channel, uint8_t *command){
910 
911     channel->remote_sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
912 
913     uint16_t flags = READ_BT_16(command, 6);
914     if (flags & 1) {
915         channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_CONT);
916     }
917 
918     // accept the other's configuration options
919     uint16_t end_pos = 4 + READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
920     uint16_t pos     = 8;
921     while (pos < end_pos){
922         uint8_t option_hint = command[pos] >> 7;
923         uint8_t option_type = command[pos] & 0x7f;
924         log_info("l2cap cid %u, hint %u, type %u", channel->local_cid, option_hint, option_type);
925         pos++;
926         uint8_t length = command[pos++];
927         // MTU { type(8): 1, len(8):2, MTU(16) }
928         if (option_type == 1 && length == 2){
929             channel->remote_mtu = READ_BT_16(command, pos);
930             // log_info("l2cap cid 0x%02x, remote mtu %u\n", channel->local_cid, channel->remote_mtu);
931             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_MTU);
932         }
933         // Flush timeout { type(8):2, len(8): 2, Flush Timeout(16)}
934         if (option_type == 2 && length == 2){
935             channel->flush_timeout = READ_BT_16(command, pos);
936         }
937         // check for unknown options
938         if (option_hint == 0 && (option_type == 0 || option_type >= 0x07)){
939             log_info("l2cap cid %u, unknown options", channel->local_cid);
940             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_INVALID);
941         }
942         pos += length;
943     }
944 }
945 
946 static int l2cap_channel_ready_for_open(l2cap_channel_t *channel){
947     // log_info("l2cap_channel_ready_for_open 0x%02x\n", channel->state_var);
948     if ((channel->state_var & L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_RSP) == 0) return 0;
949     if ((channel->state_var & L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP) == 0) return 0;
950     return 1;
951 }
952 
953 
954 void l2cap_signaling_handler_channel(l2cap_channel_t *channel, uint8_t *command){
955 
956     uint8_t  code       = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
957     uint8_t  identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
958     uint16_t result = 0;
959 
960     log_info("L2CAP signaling handler code %u, state %u\n", code, channel->state);
961 
962     // handle DISCONNECT REQUESTS seperately
963     if (code == DISCONNECTION_REQUEST){
964         switch (channel->state){
965             case L2CAP_STATE_CONFIG:
966             case L2CAP_STATE_OPEN:
967             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
968             case L2CAP_STATE_WAIT_DISCONNECT:
969                 l2cap_handle_disconnect_request(channel, identifier);
970                 break;
971 
972             default:
973                 // ignore in other states
974                 break;
975         }
976         return;
977     }
978 
979     // @STATEMACHINE(l2cap)
980     switch (channel->state) {
981 
982         case L2CAP_STATE_WAIT_CONNECT_RSP:
983             switch (code){
984                 case CONNECTION_RESPONSE:
985                     l2cap_stop_rtx(channel);
986                     result = READ_BT_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
987                     switch (result) {
988                         case 0:
989                             // successful connection
990                             channel->remote_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
991                             channel->state = L2CAP_STATE_CONFIG;
992                             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
993                             break;
994                         case 1:
995                             // connection pending. get some coffee, but start the ERTX
996                             l2cap_start_ertx(channel);
997                             break;
998                         default:
999                             // channel closed
1000                             channel->state = L2CAP_STATE_CLOSED;
1001                             // map l2cap connection response result to BTstack status enumeration
1002                             l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result);
1003 
1004                             // drop link key if security block
1005                             if (L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result == L2CAP_CONNECTION_RESPONSE_RESULT_REFUSED_SECURITY){
1006                                 hci_drop_link_key_for_bd_addr(&channel->address);
1007                             }
1008 
1009                             // discard channel
1010                             linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
1011                             btstack_memory_l2cap_channel_free(channel);
1012                             break;
1013                     }
1014                     break;
1015 
1016                 default:
1017                     //@TODO: implement other signaling packets
1018                     break;
1019             }
1020             break;
1021 
1022         case L2CAP_STATE_CONFIG:
1023             result = READ_BT_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
1024             switch (code) {
1025                 case CONFIGURE_REQUEST:
1026                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP);
1027                     l2cap_signaling_handle_configure_request(channel, command);
1028                     if (!(channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP_CONT)){
1029                         // only done if continuation not set
1030                         channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_REQ);
1031                     }
1032                     break;
1033                 case CONFIGURE_RESPONSE:
1034                     l2cap_stop_rtx(channel);
1035                     switch (result){
1036                         case 0: // success
1037                             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_RSP);
1038                             break;
1039                         case 4: // pending
1040                             l2cap_start_ertx(channel);
1041                             break;
1042                         default:
1043                             // retry on negative result
1044                             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
1045                             break;
1046                     }
1047                     break;
1048                 default:
1049                     break;
1050             }
1051             if (l2cap_channel_ready_for_open(channel)){
1052                 // for open:
1053                 channel->state = L2CAP_STATE_OPEN;
1054                 l2cap_emit_channel_opened(channel, 0);
1055                 l2cap_emit_credits(channel, 1);
1056             }
1057             break;
1058 
1059         case L2CAP_STATE_WAIT_DISCONNECT:
1060             switch (code) {
1061                 case DISCONNECTION_RESPONSE:
1062                     l2cap_finialize_channel_close(channel);
1063                     break;
1064                 default:
1065                     //@TODO: implement other signaling packets
1066                     break;
1067             }
1068             break;
1069 
1070         case L2CAP_STATE_CLOSED:
1071             // @TODO handle incoming requests
1072             break;
1073 
1074         case L2CAP_STATE_OPEN:
1075             //@TODO: implement other signaling packets, e.g. re-configure
1076             break;
1077         default:
1078             break;
1079     }
1080     // log_info("new state %u\n", channel->state);
1081 }
1082 
1083 
1084 void l2cap_signaling_handler_dispatch( hci_con_handle_t handle, uint8_t * command){
1085 
1086     // get code, signalind identifier and command len
1087     uint8_t code   = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
1088     uint8_t sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
1089 
1090     // not for a particular channel, and not CONNECTION_REQUEST, ECHO_[REQUEST|RESPONSE], INFORMATION_REQUEST
1091     if (code < 1 || code == ECHO_RESPONSE || code > INFORMATION_REQUEST){
1092         l2cap_register_signaling_response(handle, COMMAND_REJECT, sig_id, L2CAP_REJ_CMD_UNKNOWN);
1093         return;
1094     }
1095 
1096     // general commands without an assigned channel
1097     switch(code) {
1098 
1099         case CONNECTION_REQUEST: {
1100             uint16_t psm =        READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
1101             uint16_t source_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+2);
1102             l2cap_handle_connection_request(handle, sig_id, psm, source_cid);
1103             return;
1104         }
1105 
1106         case ECHO_REQUEST:
1107             l2cap_register_signaling_response(handle, code, sig_id, 0);
1108             return;
1109 
1110         case INFORMATION_REQUEST: {
1111             uint16_t infoType = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
1112             l2cap_register_signaling_response(handle, code, sig_id, infoType);
1113             return;
1114         }
1115 
1116         default:
1117             break;
1118     }
1119 
1120 
1121     // Get potential destination CID
1122     uint16_t dest_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
1123 
1124     // Find channel for this sig_id and connection handle
1125     linked_item_t *it;
1126     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
1127         l2cap_channel_t * channel = (l2cap_channel_t *) it;
1128         if (channel->handle == handle) {
1129             if (code & 1) {
1130                 // match odd commands (responses) by previous signaling identifier
1131                 if (channel->local_sig_id == sig_id) {
1132                     l2cap_signaling_handler_channel(channel, command);
1133                     break;
1134                 }
1135             } else {
1136                 // match even commands (requests) by local channel id
1137                 if (channel->local_cid == dest_cid) {
1138                     l2cap_signaling_handler_channel(channel, command);
1139                     break;
1140                 }
1141             }
1142         }
1143     }
1144 }
1145 
1146 void l2cap_acl_handler( uint8_t *packet, uint16_t size ){
1147 
1148     // Get Channel ID
1149     uint16_t channel_id = READ_L2CAP_CHANNEL_ID(packet);
1150     hci_con_handle_t handle = READ_ACL_CONNECTION_HANDLE(packet);
1151 
1152     switch (channel_id) {
1153 
1154         case L2CAP_CID_SIGNALING: {
1155 
1156             uint16_t command_offset = 8;
1157             while (command_offset < size) {
1158 
1159                 // handle signaling commands
1160                 l2cap_signaling_handler_dispatch(handle, &packet[command_offset]);
1161 
1162                 // increment command_offset
1163                 command_offset += L2CAP_SIGNALING_COMMAND_DATA_OFFSET + READ_BT_16(packet, command_offset + L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
1164             }
1165             break;
1166         }
1167 
1168         case L2CAP_CID_ATTRIBUTE_PROTOCOL:
1169             if (attribute_protocol_packet_handler) {
1170                 (*attribute_protocol_packet_handler)(ATT_DATA_PACKET, handle, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1171             }
1172             break;
1173 
1174         case L2CAP_CID_SECURITY_MANAGER_PROTOCOL:
1175             if (security_protocol_packet_handler) {
1176                 (*security_protocol_packet_handler)(SM_DATA_PACKET, handle, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1177             }
1178             break;
1179 
1180         default: {
1181             // Find channel for this channel_id and connection handle
1182             l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(channel_id);
1183             if (channel) {
1184                 l2cap_dispatch(channel, L2CAP_DATA_PACKET, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1185             }
1186             break;
1187         }
1188     }
1189 
1190     l2cap_run();
1191 }
1192 
1193 static void l2cap_packet_handler(uint8_t packet_type, uint8_t *packet, uint16_t size){
1194     switch (packet_type) {
1195         case HCI_EVENT_PACKET:
1196             l2cap_event_handler(packet, size);
1197             break;
1198         case HCI_ACL_DATA_PACKET:
1199             l2cap_acl_handler(packet, size);
1200             break;
1201         default:
1202             break;
1203     }
1204 }
1205 
1206 // finalize closed channel - l2cap_handle_disconnect_request & DISCONNECTION_RESPONSE
1207 void l2cap_finialize_channel_close(l2cap_channel_t *channel){
1208     channel->state = L2CAP_STATE_CLOSED;
1209     l2cap_emit_channel_closed(channel);
1210     // discard channel
1211     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
1212     btstack_memory_l2cap_channel_free(channel);
1213 }
1214 
1215 l2cap_service_t * l2cap_get_service(uint16_t psm){
1216     linked_item_t *it;
1217 
1218     // close open channels
1219     for (it = (linked_item_t *) l2cap_services; it ; it = it->next){
1220         l2cap_service_t * service = ((l2cap_service_t *) it);
1221         if ( service->psm == psm){
1222             return service;
1223         };
1224     }
1225     return NULL;
1226 }
1227 
1228 void l2cap_register_service_internal(void *connection, btstack_packet_handler_t packet_handler, uint16_t psm, uint16_t mtu){
1229 
1230     log_info("L2CAP_REGISTER_SERVICE psm 0x%x mtu %u", psm, mtu);
1231 
1232     // check for alread registered psm
1233     // TODO: emit error event
1234     l2cap_service_t *service = l2cap_get_service(psm);
1235     if (service) {
1236         log_error("l2cap_register_service_internal: PSM %u already registered\n", psm);
1237         l2cap_emit_service_registered(connection, L2CAP_SERVICE_ALREADY_REGISTERED, psm);
1238         return;
1239     }
1240 
1241     // alloc structure
1242     // TODO: emit error event
1243     service = (l2cap_service_t *) btstack_memory_l2cap_service_get();
1244     if (!service) {
1245         log_error("l2cap_register_service_internal: no memory for l2cap_service_t\n");
1246         l2cap_emit_service_registered(connection, BTSTACK_MEMORY_ALLOC_FAILED, psm);
1247         return;
1248     }
1249 
1250     // fill in
1251     service->psm = psm;
1252     service->mtu = mtu;
1253     service->connection = connection;
1254     service->packet_handler = packet_handler;
1255 
1256     // add to services list
1257     linked_list_add(&l2cap_services, (linked_item_t *) service);
1258 
1259     // enable page scan
1260     hci_connectable_control(1);
1261 
1262     // done
1263     l2cap_emit_service_registered(connection, 0, psm);
1264 }
1265 
1266 void l2cap_unregister_service_internal(void *connection, uint16_t psm){
1267 
1268     log_info("L2CAP_UNREGISTER_SERVICE psm 0x%x", psm);
1269 
1270     l2cap_service_t *service = l2cap_get_service(psm);
1271     if (!service) return;
1272     linked_list_remove(&l2cap_services, (linked_item_t *) service);
1273     btstack_memory_l2cap_service_free(service);
1274 
1275     // disable page scan when no services registered
1276     if (!linked_list_empty(&l2cap_services)) return;
1277     hci_connectable_control(0);
1278 }
1279 
1280 //
1281 void l2cap_close_connection(void *connection){
1282     linked_item_t *it;
1283 
1284     // close open channels - note to myself: no channel is freed, so no new for fancy iterator tricks
1285     l2cap_channel_t * channel;
1286     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
1287         channel = (l2cap_channel_t *) it;
1288         if (channel->connection == connection) {
1289             channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST;
1290         }
1291     }
1292 
1293     // unregister services
1294     it = (linked_item_t *) &l2cap_services;
1295     while (it->next) {
1296         l2cap_service_t * service = (l2cap_service_t *) it->next;
1297         if (service->connection == connection){
1298             it->next = it->next->next;
1299             btstack_memory_l2cap_service_free(service);
1300         } else {
1301             it = it->next;
1302         }
1303     }
1304 
1305     // process
1306     l2cap_run();
1307 }
1308 
1309 // Bluetooth 4.0 - allows to register handler for Attribute Protocol and Security Manager Protocol
1310 void l2cap_register_fixed_channel(btstack_packet_handler_t packet_handler, uint16_t channel_id) {
1311     switch(channel_id){
1312         case L2CAP_CID_ATTRIBUTE_PROTOCOL:
1313             attribute_protocol_packet_handler = packet_handler;
1314             break;
1315         case L2CAP_CID_SECURITY_MANAGER_PROTOCOL:
1316             security_protocol_packet_handler = packet_handler;
1317             break;
1318     }
1319 }
1320 
1321 #ifdef HAVE_BLE
1322 // Request LE connection parameter update
1323 int l2cap_le_request_connection_parameter_update(uint16_t handle, uint16_t interval_min, uint16_t interval_max, uint16_t slave_latency, uint16_t timeout_multiplier){
1324     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
1325         log_info("l2cap_send_signaling_packet, cannot send\n");
1326         return BTSTACK_ACL_BUFFERS_FULL;
1327     }
1328     // log_info("l2cap_send_signaling_packet type %u\n", cmd);
1329     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
1330     uint16_t len = l2cap_le_create_connection_parameter_update_request(acl_buffer, handle, interval_min, interval_max, slave_latency, timeout_multiplier);
1331     return hci_send_acl_packet(acl_buffer, len);
1332 }
1333 #endif
1334 
1335