xref: /btstack/src/l2cap.c (revision e0abb8e76b2cfdc59166280a6b7fe488c4788119)
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",
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);
129     uint8_t event[21];
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     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
141     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
142 }
143 
144 void l2cap_emit_channel_closed(l2cap_channel_t *channel) {
145     log_info("L2CAP_EVENT_CHANNEL_CLOSED local_cid 0x%x", channel->local_cid);
146     uint8_t event[4];
147     event[0] = L2CAP_EVENT_CHANNEL_CLOSED;
148     event[1] = sizeof(event) - 2;
149     bt_store_16(event, 2, channel->local_cid);
150     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
151     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
152 }
153 
154 void l2cap_emit_connection_request(l2cap_channel_t *channel) {
155     log_info("L2CAP_EVENT_INCOMING_CONNECTION addr %s handle 0x%x psm 0x%x local_cid 0x%x remote_cid 0x%x",
156              bd_addr_to_str(channel->address), channel->handle,  channel->psm, channel->local_cid, channel->remote_cid);
157     uint8_t event[16];
158     event[0] = L2CAP_EVENT_INCOMING_CONNECTION;
159     event[1] = sizeof(event) - 2;
160     bt_flip_addr(&event[2], channel->address);
161     bt_store_16(event,  8, channel->handle);
162     bt_store_16(event, 10, channel->psm);
163     bt_store_16(event, 12, channel->local_cid);
164     bt_store_16(event, 14, channel->remote_cid);
165     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
166     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
167 }
168 
169 static void l2cap_emit_service_registered(void *connection, uint8_t status, uint16_t psm){
170     log_info("L2CAP_EVENT_SERVICE_REGISTERED status 0x%x psm 0x%x", status, psm);
171     uint8_t event[5];
172     event[0] = L2CAP_EVENT_SERVICE_REGISTERED;
173     event[1] = sizeof(event) - 2;
174     event[2] = status;
175     bt_store_16(event, 3, psm);
176     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
177     (*packet_handler)(connection, HCI_EVENT_PACKET, 0, event, sizeof(event));
178 }
179 
180 void l2cap_emit_credits(l2cap_channel_t *channel, uint8_t credits) {
181 
182     log_info("L2CAP_EVENT_CREDITS local_cid 0x%x credits %u", channel->local_cid, credits);
183     // track credits
184     channel->packets_granted += credits;
185 
186     uint8_t event[5];
187     event[0] = L2CAP_EVENT_CREDITS;
188     event[1] = sizeof(event) - 2;
189     bt_store_16(event, 2, channel->local_cid);
190     event[4] = credits;
191     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
192     l2cap_dispatch(channel, HCI_EVENT_PACKET, event, sizeof(event));
193 }
194 
195 void l2cap_block_new_credits(uint8_t blocked){
196     new_credits_blocked = blocked;
197 }
198 
199 void l2cap_hand_out_credits(void){
200 
201     if (new_credits_blocked) return;    // we're told not to. used by daemon
202 
203     linked_item_t *it;
204     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
205         if (!hci_number_free_acl_slots()) return;
206         l2cap_channel_t * channel = (l2cap_channel_t *) it;
207         if (channel->state != L2CAP_STATE_OPEN) continue;
208         if (hci_number_outgoing_packets(channel->handle) < NR_BUFFERED_ACL_PACKETS && channel->packets_granted == 0) {
209             l2cap_emit_credits(channel, 1);
210         }
211     }
212 }
213 
214 l2cap_channel_t * l2cap_get_channel_for_local_cid(uint16_t local_cid){
215     linked_item_t *it;
216     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
217         l2cap_channel_t * channel = (l2cap_channel_t *) it;
218         if ( channel->local_cid == local_cid) {
219             return channel;
220         }
221     }
222     return NULL;
223 }
224 
225 int  l2cap_can_send_packet_now(uint16_t local_cid){
226     l2cap_channel_t *channel = l2cap_get_channel_for_local_cid(local_cid);
227     if (!channel) return 0;
228     if (!channel->packets_granted) return 0;
229     return hci_can_send_packet_now(HCI_ACL_DATA_PACKET);
230 }
231 
232 uint16_t l2cap_get_remote_mtu_for_local_cid(uint16_t local_cid){
233     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
234     if (channel) {
235         return channel->remote_mtu;
236     }
237     return 0;
238 }
239 
240 int l2cap_send_signaling_packet(hci_con_handle_t handle, L2CAP_SIGNALING_COMMANDS cmd, uint8_t identifier, ...){
241 
242     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
243         log_info("l2cap_send_signaling_packet, cannot send\n");
244         return BTSTACK_ACL_BUFFERS_FULL;
245     }
246 
247     // log_info("l2cap_send_signaling_packet type %u\n", cmd);
248     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
249     va_list argptr;
250     va_start(argptr, identifier);
251     uint16_t len = l2cap_create_signaling_internal(acl_buffer, handle, cmd, identifier, argptr);
252     va_end(argptr);
253     // log_info("l2cap_send_signaling_packet con %u!\n", handle);
254     return hci_send_acl_packet(acl_buffer, len);
255 }
256 
257 uint8_t *l2cap_get_outgoing_buffer(void){
258     return hci_get_outgoing_acl_packet_buffer() + COMPLETE_L2CAP_HEADER; // 8 bytes
259 }
260 
261 int l2cap_send_prepared(uint16_t local_cid, uint16_t len){
262 
263     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
264         log_info("l2cap_send_internal cid 0x%02x, cannot send\n", local_cid);
265         return BTSTACK_ACL_BUFFERS_FULL;
266     }
267 
268     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
269     if (!channel) {
270         log_error("l2cap_send_internal no channel for cid 0x%02x\n", local_cid);
271         return -1;   // TODO: define error
272     }
273 
274     if (channel->packets_granted == 0){
275         log_error("l2cap_send_internal cid 0x%02x, no credits!\n", local_cid);
276         return -1;  // TODO: define error
277     }
278 
279     --channel->packets_granted;
280 
281     log_debug("l2cap_send_internal cid 0x%02x, handle %u, 1 credit used, credits left %u;\n",
282                   local_cid, channel->handle, channel->packets_granted);
283 
284     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
285 
286     // 0 - Connection handle : PB=10 : BC=00
287     bt_store_16(acl_buffer, 0, channel->handle | (2 << 12) | (0 << 14));
288     // 2 - ACL length
289     bt_store_16(acl_buffer, 2,  len + 4);
290     // 4 - L2CAP packet length
291     bt_store_16(acl_buffer, 4,  len + 0);
292     // 6 - L2CAP channel DEST
293     bt_store_16(acl_buffer, 6, channel->remote_cid);
294     // send
295     int err = hci_send_acl_packet(acl_buffer, len+8);
296 
297     l2cap_hand_out_credits();
298 
299     return err;
300 }
301 
302 int l2cap_send_prepared_connectionless(uint16_t handle, uint16_t cid, uint16_t len){
303 
304     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
305         log_info("l2cap_send_prepared_to_handle cid 0x%02x, cannot send\n", cid);
306         return BTSTACK_ACL_BUFFERS_FULL;
307     }
308 
309     log_debug("l2cap_send_prepared_to_handle cid 0x%02x, handle %u\n", cid, handle);
310 
311     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
312 
313     // 0 - Connection handle : PB=10 : BC=00
314     bt_store_16(acl_buffer, 0, handle | (2 << 12) | (0 << 14));
315     // 2 - ACL length
316     bt_store_16(acl_buffer, 2,  len + 4);
317     // 4 - L2CAP packet length
318     bt_store_16(acl_buffer, 4,  len + 0);
319     // 6 - L2CAP channel DEST
320     bt_store_16(acl_buffer, 6, cid);
321     // send
322     int err = hci_send_acl_packet(acl_buffer, len+8);
323 
324     l2cap_hand_out_credits();
325 
326     return err;
327 }
328 
329 int l2cap_send_internal(uint16_t local_cid, uint8_t *data, uint16_t len){
330 
331     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
332         log_info("l2cap_send_internal cid 0x%02x, cannot send\n", local_cid);
333         return BTSTACK_ACL_BUFFERS_FULL;
334     }
335 
336     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
337 
338     memcpy(&acl_buffer[8], data, len);
339 
340     return l2cap_send_prepared(local_cid, len);
341 }
342 
343 int l2cap_send_connectionless(uint16_t handle, uint16_t cid, uint8_t *data, uint16_t len){
344 
345     if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)){
346         log_info("l2cap_send_internal cid 0x%02x, cannot send\n", cid);
347         return BTSTACK_ACL_BUFFERS_FULL;
348     }
349 
350     uint8_t *acl_buffer = hci_get_outgoing_acl_packet_buffer();
351 
352     memcpy(&acl_buffer[8], data, len);
353 
354     return l2cap_send_prepared_connectionless(handle, cid, len);
355 }
356 
357 static inline void channelStateVarSetFlag(l2cap_channel_t *channel, L2CAP_CHANNEL_STATE_VAR flag){
358     channel->state_var = (L2CAP_CHANNEL_STATE_VAR) (channel->state_var | flag);
359 }
360 
361 static inline void channelStateVarClearFlag(l2cap_channel_t *channel, L2CAP_CHANNEL_STATE_VAR flag){
362     channel->state_var = (L2CAP_CHANNEL_STATE_VAR) (channel->state_var & ~flag);
363 }
364 
365 
366 
367 // MARK: L2CAP_RUN
368 // process outstanding signaling tasks
369 void l2cap_run(void){
370 
371     // check pending signaling responses
372     while (signaling_responses_pending){
373 
374         if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)) break;
375 
376         hci_con_handle_t handle = signaling_responses[0].handle;
377         uint8_t sig_id = signaling_responses[0].sig_id;
378         uint16_t infoType = signaling_responses[0].data;    // INFORMATION_REQUEST
379         uint16_t result   = signaling_responses[0].data;    // CONNECTION_REQUEST
380 
381         switch (signaling_responses[0].code){
382             case CONNECTION_REQUEST:
383                 l2cap_send_signaling_packet(handle, CONNECTION_RESPONSE, sig_id, 0, 0, result, 0);
384                 break;
385             case ECHO_REQUEST:
386                 l2cap_send_signaling_packet(handle, ECHO_RESPONSE, sig_id, 0, NULL);
387                 break;
388             case INFORMATION_REQUEST:
389                 if (infoType == 2) {
390                     uint32_t features = 0;
391                     // extended features request supported, however no features present
392                     l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 0, 4, &features);
393                 } else {
394                     // all other types are not supported
395                     l2cap_send_signaling_packet(handle, INFORMATION_RESPONSE, sig_id, infoType, 1, 0, NULL);
396                 }
397                 break;
398             default:
399                 // should not happen
400                 break;
401         }
402 
403         // remove first item
404         signaling_responses_pending--;
405         int i;
406         for (i=0; i < signaling_responses_pending; i++){
407             memcpy(&signaling_responses[i], &signaling_responses[i+1], sizeof(l2cap_signaling_response_t));
408         }
409     }
410 
411     uint8_t  config_options[4];
412     linked_item_t *it;
413     linked_item_t *next;
414     for (it = (linked_item_t *) l2cap_channels; it ; it = next){
415         next = it->next;    // cache next item as current item might get freed
416 
417         if (!hci_can_send_packet_now(HCI_COMMAND_DATA_PACKET)) break;
418         if (!hci_can_send_packet_now(HCI_ACL_DATA_PACKET)) break;
419 
420         l2cap_channel_t * channel = (l2cap_channel_t *) it;
421 
422         // log_info("l2cap_run: state %u, var 0x%02x\n", channel->state, channel->state_var);
423 
424 
425         switch (channel->state){
426 
427             case L2CAP_STATE_WILL_SEND_CREATE_CONNECTION:
428                 // send connection request - set state first
429                 channel->state = L2CAP_STATE_WAIT_CONNECTION_COMPLETE;
430                 // BD_ADDR, Packet_Type, Page_Scan_Repetition_Mode, Reserved, Clock_Offset, Allow_Role_Switch
431                 hci_send_cmd(&hci_create_connection, channel->address, hci_usable_acl_packet_types(), 0, 0, 0, 1);
432                 break;
433 
434             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE:
435                 l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, 0, 0, channel->reason, 0);
436                 // discard channel - l2cap_finialize_channel_close without sending l2cap close event
437                 linked_list_remove(&l2cap_channels, (linked_item_t *) channel); // -- remove from list
438                 btstack_memory_l2cap_channel_free(channel);
439                 break;
440 
441             case L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT:
442                 channel->state = L2CAP_STATE_CONFIG;
443                 channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
444                 l2cap_send_signaling_packet(channel->handle, CONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid, 0, 0);
445                 break;
446 
447             case L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST:
448                 // success, start l2cap handshake
449                 channel->local_sig_id = l2cap_next_sig_id();
450                 channel->state = L2CAP_STATE_WAIT_CONNECT_RSP;
451                 l2cap_send_signaling_packet( channel->handle, CONNECTION_REQUEST, channel->local_sig_id, channel->psm, channel->local_cid);
452                 break;
453 
454             case L2CAP_STATE_CONFIG:
455                 if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP){
456                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP);
457                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP);
458                     l2cap_send_signaling_packet(channel->handle, CONFIGURE_RESPONSE, channel->remote_sig_id, channel->remote_cid, 0, 0, 0, NULL);
459                 }
460                 else if (channel->state_var & L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ){
461                     channelStateVarClearFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
462                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SENT_CONF_REQ);
463                     channel->local_sig_id = l2cap_next_sig_id();
464                     config_options[0] = 1; // MTU
465                     config_options[1] = 2; // len param
466                     bt_store_16( (uint8_t*)&config_options, 2, channel->local_mtu);
467                     l2cap_send_signaling_packet(channel->handle, CONFIGURE_REQUEST, channel->local_sig_id, channel->remote_cid, 0, 4, &config_options);
468                 }
469                 if (l2cap_channel_ready_for_open(channel)){
470                     channel->state = L2CAP_STATE_OPEN;
471                     l2cap_emit_channel_opened(channel, 0);  // success
472                     l2cap_emit_credits(channel, 1);
473                 }
474                 break;
475 
476             case L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE:
477                 l2cap_send_signaling_packet( channel->handle, DISCONNECTION_RESPONSE, channel->remote_sig_id, channel->local_cid, channel->remote_cid);
478                 l2cap_finialize_channel_close(channel);  // -- remove from list
479                 break;
480 
481             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
482                 channel->local_sig_id = l2cap_next_sig_id();
483                 channel->state = L2CAP_STATE_WAIT_DISCONNECT;
484                 l2cap_send_signaling_packet( channel->handle, DISCONNECTION_REQUEST, channel->local_sig_id, channel->remote_cid, channel->local_cid);
485                 break;
486             default:
487                 break;
488         }
489     }
490 }
491 
492 uint16_t l2cap_max_mtu(void){
493     return hci_max_acl_data_packet_length() - L2CAP_HEADER_SIZE;
494 }
495 
496 // open outgoing L2CAP channel
497 void l2cap_create_channel_internal(void * connection, btstack_packet_handler_t packet_handler,
498                                    bd_addr_t address, uint16_t psm, uint16_t mtu){
499 
500     log_info("L2CAP_CREATE_CHANNEL_MTU addr %s psm 0x%x mtu %u", bd_addr_to_str(address), psm, mtu);
501 
502     // alloc structure
503     l2cap_channel_t * chan = (l2cap_channel_t*) btstack_memory_l2cap_channel_get();
504     if (!chan) {
505         // emit error event
506         l2cap_channel_t dummy_channel;
507         BD_ADDR_COPY(dummy_channel.address, address);
508         dummy_channel.psm = psm;
509         l2cap_emit_channel_opened(&dummy_channel, BTSTACK_MEMORY_ALLOC_FAILED);
510         return;
511     }
512     // limit local mtu to max acl packet length
513     if (mtu > l2cap_max_mtu()) {
514         mtu = l2cap_max_mtu();
515     }
516 
517     // fill in
518     BD_ADDR_COPY(chan->address, address);
519     chan->psm = psm;
520     chan->handle = 0;
521     chan->connection = connection;
522     chan->packet_handler = packet_handler;
523     chan->remote_mtu = L2CAP_MINIMAL_MTU;
524     chan->local_mtu = mtu;
525     chan->packets_granted = 0;
526 
527     // set initial state
528     chan->state = L2CAP_STATE_WILL_SEND_CREATE_CONNECTION;
529     chan->state_var = L2CAP_CHANNEL_STATE_VAR_NONE;
530     chan->remote_sig_id = L2CAP_SIG_ID_INVALID;
531     chan->local_sig_id = L2CAP_SIG_ID_INVALID;
532 
533     // add to connections list
534     linked_list_add(&l2cap_channels, (linked_item_t *) chan);
535 
536     l2cap_run();
537 }
538 
539 void l2cap_disconnect_internal(uint16_t local_cid, uint8_t reason){
540     log_info("L2CAP_DISCONNECT local_cid 0x%x reason 0x%x", local_cid, reason);
541     // find channel for local_cid
542     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
543     if (channel) {
544         channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST;
545     }
546     // process
547     l2cap_run();
548 }
549 
550 static void l2cap_handle_connection_failed_for_addr(bd_addr_t address, uint8_t status){
551     linked_item_t *it = (linked_item_t *) &l2cap_channels;
552     while (it->next){
553         l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
554         if ( ! BD_ADDR_CMP( channel->address, address) ){
555             if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
556                 // failure, forward error code
557                 l2cap_emit_channel_opened(channel, status);
558                 // discard channel
559                 it->next = it->next->next;
560                 btstack_memory_l2cap_channel_free(channel);
561             }
562         } else {
563             it = it->next;
564         }
565     }
566 }
567 
568 static void l2cap_handle_connection_success_for_addr(bd_addr_t address, hci_con_handle_t handle){
569     linked_item_t *it;
570     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
571         l2cap_channel_t * channel = (l2cap_channel_t *) it;
572         if ( ! BD_ADDR_CMP( channel->address, address) ){
573             if (channel->state == L2CAP_STATE_WAIT_CONNECTION_COMPLETE || channel->state == L2CAP_STATE_WILL_SEND_CREATE_CONNECTION) {
574                 // success, start l2cap handshake
575                 channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_REQUEST;
576                 channel->handle = handle;
577                 channel->local_cid = l2cap_next_local_cid();
578             }
579         }
580     }
581     // process
582     l2cap_run();
583 }
584 
585 void l2cap_event_handler( uint8_t *packet, uint16_t size ){
586 
587     bd_addr_t address;
588     hci_con_handle_t handle;
589     l2cap_channel_t * channel;
590     linked_item_t *it;
591     int hci_con_used;
592 
593     switch(packet[0]){
594 
595         // handle connection complete events
596         case HCI_EVENT_CONNECTION_COMPLETE:
597             bt_flip_addr(address, &packet[5]);
598             if (packet[2] == 0){
599                 handle = READ_BT_16(packet, 3);
600                 l2cap_handle_connection_success_for_addr(address, handle);
601             } else {
602                 l2cap_handle_connection_failed_for_addr(address, packet[2]);
603             }
604             break;
605 
606         // handle successful create connection cancel command
607         case HCI_EVENT_COMMAND_COMPLETE:
608             if ( COMMAND_COMPLETE_EVENT(packet, hci_create_connection_cancel) ) {
609                 if (packet[5] == 0){
610                     bt_flip_addr(address, &packet[6]);
611                     // CONNECTION TERMINATED BY LOCAL HOST (0X16)
612                     l2cap_handle_connection_failed_for_addr(address, 0x16);
613                 }
614             }
615             l2cap_run();    // try sending signaling packets first
616             break;
617 
618         case HCI_EVENT_COMMAND_STATUS:
619             l2cap_run();    // try sending signaling packets first
620             break;
621 
622         // handle disconnection complete events
623         case HCI_EVENT_DISCONNECTION_COMPLETE:
624             // send l2cap disconnect events for all channels on this handle
625             handle = READ_BT_16(packet, 3);
626             it = (linked_item_t *) &l2cap_channels;
627             while (it->next){
628                 l2cap_channel_t * channel = (l2cap_channel_t *) it->next;
629                 if ( channel->handle == handle ){
630                     // update prev item before free'ing next element - don't call l2cap_finalize_channel_close
631                     it->next = it->next->next;
632                     l2cap_emit_channel_closed(channel);
633                     btstack_memory_l2cap_channel_free(channel);
634                 } else {
635                     it = it->next;
636                 }
637             }
638             break;
639 
640         case HCI_EVENT_NUMBER_OF_COMPLETED_PACKETS:
641             l2cap_run();    // try sending signaling packets first
642             l2cap_hand_out_credits();
643             break;
644 
645         // HCI Connection Timeouts
646         case L2CAP_EVENT_TIMEOUT_CHECK:
647             handle = READ_BT_16(packet, 2);
648             if (hci_authentication_active_for_handle(handle)) break;
649             hci_con_used = 0;
650             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
651                 channel = (l2cap_channel_t *) it;
652                 if (channel->handle == handle) {
653                     hci_con_used = 1;
654                 }
655             }
656             if (hci_con_used) break;
657             if (!hci_can_send_packet_now(HCI_COMMAND_DATA_PACKET)) break;
658             hci_send_cmd(&hci_disconnect, handle, 0x13); // remote closed connection
659             break;
660 
661         case DAEMON_EVENT_HCI_PACKET_SENT:
662             for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
663                 channel = (l2cap_channel_t *) it;
664                 if (channel->packet_handler) {
665                     (* (channel->packet_handler))(HCI_EVENT_PACKET, channel->local_cid, packet, size);
666                 }
667             }
668             if (attribute_protocol_packet_handler) {
669                 (*attribute_protocol_packet_handler)(HCI_EVENT_PACKET, 0, packet, size);
670             }
671             if (security_protocol_packet_handler) {
672                 (*security_protocol_packet_handler)(HCI_EVENT_PACKET, 0, packet, size);
673             }
674             break;
675 
676         default:
677             break;
678     }
679 
680     // pass on
681     (*packet_handler)(NULL, HCI_EVENT_PACKET, 0, packet, size);
682 }
683 
684 static void l2cap_handle_disconnect_request(l2cap_channel_t *channel, uint16_t identifier){
685     channel->remote_sig_id = identifier;
686     channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_RESPONSE;
687     l2cap_run();
688 }
689 
690 static void l2cap_register_signaling_response(hci_con_handle_t handle, uint8_t code, uint8_t sig_id, uint16_t data){
691     // Vol 3, Part A, 4.3: "The DCID and SCID fields shall be ignored when the result field indi- cates the connection was refused."
692     if (signaling_responses_pending < NR_PENDING_SIGNALING_RESPONSES) {
693         signaling_responses[signaling_responses_pending].handle = handle;
694         signaling_responses[signaling_responses_pending].code = code;
695         signaling_responses[signaling_responses_pending].sig_id = sig_id;
696         signaling_responses[signaling_responses_pending].data = data;
697         signaling_responses_pending++;
698         l2cap_run();
699     }
700 }
701 
702 static void l2cap_handle_connection_request(hci_con_handle_t handle, uint8_t sig_id, uint16_t psm, uint16_t source_cid){
703 
704     // log_info("l2cap_handle_connection_request for handle %u, psm %u cid 0x%02x\n", handle, psm, source_cid);
705     l2cap_service_t *service = l2cap_get_service(psm);
706     if (!service) {
707         // 0x0002 PSM not supported
708         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0002);
709         return;
710     }
711 
712     hci_connection_t * hci_connection = connection_for_handle( handle );
713     if (!hci_connection) {
714         //
715         log_error("no hci_connection for handle %u\n", handle);
716         return;
717     }
718     // alloc structure
719     // log_info("l2cap_handle_connection_request register channel\n");
720     l2cap_channel_t * channel = (l2cap_channel_t*) btstack_memory_l2cap_channel_get();
721     if (!channel){
722         // 0x0004 No resources available
723         l2cap_register_signaling_response(handle, CONNECTION_REQUEST, sig_id, 0x0004);
724         return;
725     }
726 
727     // fill in
728     BD_ADDR_COPY(channel->address, hci_connection->address);
729     channel->psm = psm;
730     channel->handle = handle;
731     channel->connection = service->connection;
732     channel->packet_handler = service->packet_handler;
733     channel->local_cid  = l2cap_next_local_cid();
734     channel->remote_cid = source_cid;
735     channel->local_mtu  = service->mtu;
736     channel->remote_mtu = L2CAP_DEFAULT_MTU;
737     channel->packets_granted = 0;
738     channel->remote_sig_id = sig_id;
739 
740     // limit local mtu to max acl packet length
741     if (channel->local_mtu > l2cap_max_mtu()) {
742         channel->local_mtu = l2cap_max_mtu();
743     }
744 
745     // set initial state
746     channel->state = L2CAP_STATE_WAIT_CLIENT_ACCEPT_OR_REJECT;
747     channel->state_var = L2CAP_CHANNEL_STATE_VAR_NONE;
748 
749     // add to connections list
750     linked_list_add(&l2cap_channels, (linked_item_t *) channel);
751 
752     // emit incoming connection request
753     l2cap_emit_connection_request(channel);
754 }
755 
756 void l2cap_accept_connection_internal(uint16_t local_cid){
757     log_info("L2CAP_ACCEPT_CONNECTION local_cid 0x%x", local_cid);
758     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(local_cid);
759     if (!channel) {
760         log_error("l2cap_accept_connection_internal called but local_cid 0x%x not found", local_cid);
761         return;
762     }
763 
764     channel->state = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_ACCEPT;
765 
766     // process
767     l2cap_run();
768 }
769 
770 void l2cap_decline_connection_internal(uint16_t local_cid, uint8_t reason){
771     log_info("L2CAP_DECLINE_CONNECTION local_cid 0x%x, reason %x", local_cid, reason);
772     l2cap_channel_t * channel = l2cap_get_channel_for_local_cid( local_cid);
773     if (!channel) {
774         log_error( "l2cap_decline_connection_internal called but local_cid 0x%x not found", local_cid);
775         return;
776     }
777     channel->state  = L2CAP_STATE_WILL_SEND_CONNECTION_RESPONSE_DECLINE;
778     channel->reason = reason;
779     l2cap_run();
780 }
781 
782 void l2cap_signaling_handle_configure_request(l2cap_channel_t *channel, uint8_t *command){
783 
784     channel->remote_sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
785 
786     // accept the other's configuration options
787     uint16_t end_pos = 4 + READ_BT_16(command, L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
788     uint16_t pos     = 8;
789     while (pos < end_pos){
790         uint8_t type   = command[pos++];
791         uint8_t length = command[pos++];
792         // MTU { type(8): 1, len(8):2, MTU(16) }
793         if ((type & 0x7f) == 1 && length == 2){
794             channel->remote_mtu = READ_BT_16(command, pos);
795             // log_info("l2cap cid 0x%02x, remote mtu %u\n", channel->local_cid, channel->remote_mtu);
796         }
797         pos += length;
798     }
799 }
800 
801 static int l2cap_channel_ready_for_open(l2cap_channel_t *channel){
802     // log_info("l2cap_channel_ready_for_open 0x%02x\n", channel->state_var);
803     if ((channel->state_var & L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_RSP) == 0) return 0;
804     if ((channel->state_var & L2CAP_CHANNEL_STATE_VAR_SENT_CONF_RSP) == 0) return 0;
805     return 1;
806 }
807 
808 
809 void l2cap_signaling_handler_channel(l2cap_channel_t *channel, uint8_t *command){
810 
811     uint8_t  code       = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
812     uint8_t  identifier = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
813     uint16_t result = 0;
814 
815     log_info("L2CAP signaling handler code %u, state %u\n", code, channel->state);
816 
817     // handle DISCONNECT REQUESTS seperately
818     if (code == DISCONNECTION_REQUEST){
819         switch (channel->state){
820             case L2CAP_STATE_CONFIG:
821             case L2CAP_STATE_OPEN:
822             case L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST:
823             case L2CAP_STATE_WAIT_DISCONNECT:
824                 l2cap_handle_disconnect_request(channel, identifier);
825                 break;
826 
827             default:
828                 // ignore in other states
829                 break;
830         }
831         return;
832     }
833 
834     // @STATEMACHINE(l2cap)
835     switch (channel->state) {
836 
837         case L2CAP_STATE_WAIT_CONNECT_RSP:
838             switch (code){
839                 case CONNECTION_RESPONSE:
840                     result = READ_BT_16 (command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+4);
841                     switch (result) {
842                         case 0:
843                             // successful connection
844                             channel->remote_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
845                             channel->state = L2CAP_STATE_CONFIG;
846                             channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_REQ);
847                             break;
848                         case 1:
849                             // connection pending. get some coffee
850                             break;
851                         default:
852                             // channel closed
853                             channel->state = L2CAP_STATE_CLOSED;
854 
855                             // map l2cap connection response result to BTstack status enumeration
856                             l2cap_emit_channel_opened(channel, L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result);
857 
858                             // drop link key if security block
859                             if (L2CAP_CONNECTION_RESPONSE_RESULT_SUCCESSFUL + result == L2CAP_CONNECTION_RESPONSE_RESULT_REFUSED_SECURITY){
860                                 hci_drop_link_key_for_bd_addr(&channel->address);
861                             }
862 
863                             // discard channel
864                             linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
865                             btstack_memory_l2cap_channel_free(channel);
866                             break;
867                     }
868                     break;
869 
870                 default:
871                     //@TODO: implement other signaling packets
872                     break;
873             }
874             break;
875 
876         case L2CAP_STATE_CONFIG:
877             switch (code) {
878                 case CONFIGURE_REQUEST:
879                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_REQ);
880                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_SEND_CONF_RSP);
881                     l2cap_signaling_handle_configure_request(channel, command);
882                     break;
883                 case CONFIGURE_RESPONSE:
884                     channelStateVarSetFlag(channel, L2CAP_CHANNEL_STATE_VAR_RCVD_CONF_RSP);
885                     break;
886                 default:
887                     break;
888             }
889             if (l2cap_channel_ready_for_open(channel)){
890                 // for open:
891                 channel->state = L2CAP_STATE_OPEN;
892                 l2cap_emit_channel_opened(channel, 0);
893                 l2cap_emit_credits(channel, 1);
894             }
895             break;
896 
897         case L2CAP_STATE_WAIT_DISCONNECT:
898             switch (code) {
899                 case DISCONNECTION_RESPONSE:
900                     l2cap_finialize_channel_close(channel);
901                     break;
902                 default:
903                     //@TODO: implement other signaling packets
904                     break;
905             }
906             break;
907 
908         case L2CAP_STATE_CLOSED:
909             // @TODO handle incoming requests
910             break;
911 
912         case L2CAP_STATE_OPEN:
913             //@TODO: implement other signaling packets, e.g. re-configure
914             break;
915         default:
916             break;
917     }
918     // log_info("new state %u\n", channel->state);
919 }
920 
921 
922 void l2cap_signaling_handler_dispatch( hci_con_handle_t handle, uint8_t * command){
923 
924     // get code, signalind identifier and command len
925     uint8_t code   = command[L2CAP_SIGNALING_COMMAND_CODE_OFFSET];
926     uint8_t sig_id = command[L2CAP_SIGNALING_COMMAND_SIGID_OFFSET];
927 
928     // not for a particular channel, and not CONNECTION_REQUEST, ECHO_[REQUEST|RESPONSE], INFORMATION_REQUEST
929     if (code < 1 || code == ECHO_RESPONSE || code > INFORMATION_REQUEST){
930         return;
931     }
932 
933     // general commands without an assigned channel
934     switch(code) {
935 
936         case CONNECTION_REQUEST: {
937             uint16_t psm =        READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
938             uint16_t source_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET+2);
939             l2cap_handle_connection_request(handle, sig_id, psm, source_cid);
940             return;
941         }
942 
943         case ECHO_REQUEST:
944             l2cap_register_signaling_response(handle, code, sig_id, 0);
945             return;
946 
947         case INFORMATION_REQUEST: {
948             uint16_t infoType = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
949             l2cap_register_signaling_response(handle, code, sig_id, infoType);
950             return;
951         }
952 
953         default:
954             break;
955     }
956 
957 
958     // Get potential destination CID
959     uint16_t dest_cid = READ_BT_16(command, L2CAP_SIGNALING_COMMAND_DATA_OFFSET);
960 
961     // Find channel for this sig_id and connection handle
962     linked_item_t *it;
963     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
964         l2cap_channel_t * channel = (l2cap_channel_t *) it;
965         if (channel->handle == handle) {
966             if (code & 1) {
967                 // match odd commands (responses) by previous signaling identifier
968                 if (channel->local_sig_id == sig_id) {
969                     l2cap_signaling_handler_channel(channel, command);
970                     break;
971                 }
972             } else {
973                 // match even commands (requests) by local channel id
974                 if (channel->local_cid == dest_cid) {
975                     l2cap_signaling_handler_channel(channel, command);
976                     break;
977                 }
978             }
979         }
980     }
981 }
982 
983 void l2cap_acl_handler( uint8_t *packet, uint16_t size ){
984 
985     // Get Channel ID
986     uint16_t channel_id = READ_L2CAP_CHANNEL_ID(packet);
987     hci_con_handle_t handle = READ_ACL_CONNECTION_HANDLE(packet);
988 
989     switch (channel_id) {
990 
991         case L2CAP_CID_SIGNALING: {
992 
993             uint16_t command_offset = 8;
994             while (command_offset < size) {
995 
996                 // handle signaling commands
997                 l2cap_signaling_handler_dispatch(handle, &packet[command_offset]);
998 
999                 // increment command_offset
1000                 command_offset += L2CAP_SIGNALING_COMMAND_DATA_OFFSET + READ_BT_16(packet, command_offset + L2CAP_SIGNALING_COMMAND_LENGTH_OFFSET);
1001             }
1002             break;
1003         }
1004 
1005         case L2CAP_CID_ATTRIBUTE_PROTOCOL:
1006             if (attribute_protocol_packet_handler) {
1007                 (*attribute_protocol_packet_handler)(ATT_DATA_PACKET, handle, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1008             }
1009             break;
1010 
1011         case L2CAP_CID_SECURITY_MANAGER_PROTOCOL:
1012             if (security_protocol_packet_handler) {
1013                 (*security_protocol_packet_handler)(SM_DATA_PACKET, handle, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1014             }
1015             break;
1016 
1017         default: {
1018             // Find channel for this channel_id and connection handle
1019             l2cap_channel_t * channel = l2cap_get_channel_for_local_cid(channel_id);
1020             if (channel) {
1021                 l2cap_dispatch(channel, L2CAP_DATA_PACKET, &packet[COMPLETE_L2CAP_HEADER], size-COMPLETE_L2CAP_HEADER);
1022             }
1023             break;
1024         }
1025     }
1026 
1027     l2cap_run();
1028 }
1029 
1030 static void l2cap_packet_handler(uint8_t packet_type, uint8_t *packet, uint16_t size){
1031     switch (packet_type) {
1032         case HCI_EVENT_PACKET:
1033             l2cap_event_handler(packet, size);
1034             break;
1035         case HCI_ACL_DATA_PACKET:
1036             l2cap_acl_handler(packet, size);
1037             break;
1038         default:
1039             break;
1040     }
1041 }
1042 
1043 // finalize closed channel - l2cap_handle_disconnect_request & DISCONNECTION_RESPONSE
1044 void l2cap_finialize_channel_close(l2cap_channel_t *channel){
1045     channel->state = L2CAP_STATE_CLOSED;
1046     l2cap_emit_channel_closed(channel);
1047     // discard channel
1048     linked_list_remove(&l2cap_channels, (linked_item_t *) channel);
1049     btstack_memory_l2cap_channel_free(channel);
1050 }
1051 
1052 l2cap_service_t * l2cap_get_service(uint16_t psm){
1053     linked_item_t *it;
1054 
1055     // close open channels
1056     for (it = (linked_item_t *) l2cap_services; it ; it = it->next){
1057         l2cap_service_t * service = ((l2cap_service_t *) it);
1058         if ( service->psm == psm){
1059             return service;
1060         };
1061     }
1062     return NULL;
1063 }
1064 
1065 void l2cap_register_service_internal(void *connection, btstack_packet_handler_t packet_handler, uint16_t psm, uint16_t mtu){
1066 
1067     log_info("L2CAP_REGISTER_SERVICE psm 0x%x mtu %u", psm, mtu);
1068 
1069     // check for alread registered psm
1070     // TODO: emit error event
1071     l2cap_service_t *service = l2cap_get_service(psm);
1072     if (service) {
1073         log_error("l2cap_register_service_internal: PSM %u already registered\n", psm);
1074         l2cap_emit_service_registered(connection, L2CAP_SERVICE_ALREADY_REGISTERED, psm);
1075         return;
1076     }
1077 
1078     // alloc structure
1079     // TODO: emit error event
1080     service = (l2cap_service_t *) btstack_memory_l2cap_service_get();
1081     if (!service) {
1082         log_error("l2cap_register_service_internal: no memory for l2cap_service_t\n");
1083         l2cap_emit_service_registered(connection, BTSTACK_MEMORY_ALLOC_FAILED, psm);
1084         return;
1085     }
1086 
1087     // fill in
1088     service->psm = psm;
1089     service->mtu = mtu;
1090     service->connection = connection;
1091     service->packet_handler = packet_handler;
1092 
1093     // add to services list
1094     linked_list_add(&l2cap_services, (linked_item_t *) service);
1095 
1096     // enable page scan
1097     hci_connectable_control(1);
1098 
1099     // done
1100     l2cap_emit_service_registered(connection, 0, psm);
1101 }
1102 
1103 void l2cap_unregister_service_internal(void *connection, uint16_t psm){
1104 
1105     log_info("L2CAP_UNREGISTER_SERVICE psm 0x%x", psm);
1106 
1107     l2cap_service_t *service = l2cap_get_service(psm);
1108     if (!service) return;
1109     linked_list_remove(&l2cap_services, (linked_item_t *) service);
1110     btstack_memory_l2cap_service_free(service);
1111 
1112     // disable page scan when no services registered
1113     if (!linked_list_empty(&l2cap_services)) return;
1114     hci_connectable_control(0);
1115 }
1116 
1117 //
1118 void l2cap_close_connection(void *connection){
1119     linked_item_t *it;
1120 
1121     // close open channels - note to myself: no channel is freed, so no new for fancy iterator tricks
1122     l2cap_channel_t * channel;
1123     for (it = (linked_item_t *) l2cap_channels; it ; it = it->next){
1124         channel = (l2cap_channel_t *) it;
1125         if (channel->connection == connection) {
1126             channel->state = L2CAP_STATE_WILL_SEND_DISCONNECT_REQUEST;
1127         }
1128     }
1129 
1130     // unregister services
1131     it = (linked_item_t *) &l2cap_services;
1132     while (it->next) {
1133         l2cap_service_t * service = (l2cap_service_t *) it->next;
1134         if (service->connection == connection){
1135             it->next = it->next->next;
1136             btstack_memory_l2cap_service_free(service);
1137         } else {
1138             it = it->next;
1139         }
1140     }
1141 
1142     // process
1143     l2cap_run();
1144 }
1145 
1146 // Bluetooth 4.0 - allows to register handler for Attribute Protocol and Security Manager Protocol
1147 void l2cap_register_fixed_channel(btstack_packet_handler_t packet_handler, uint16_t channel_id) {
1148     switch(channel_id){
1149         case L2CAP_CID_ATTRIBUTE_PROTOCOL:
1150             attribute_protocol_packet_handler = packet_handler;
1151             break;
1152         case L2CAP_CID_SECURITY_MANAGER_PROTOCOL:
1153             security_protocol_packet_handler = packet_handler;
1154             break;
1155     }
1156 }
1157 
1158