xref: /btstack/src/classic/rfcomm.c (revision b6fc147f78a37f3479b846963ca40c9b931f6e2f)
1 /*
2  * Copyright (C) 2014 BlueKitchen GmbH
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the copyright holders nor the names of
14  *    contributors may be used to endorse or promote products derived
15  *    from this software without specific prior written permission.
16  * 4. Any redistribution, use, or modification is done solely for
17  *    personal benefit and not for any commercial purpose or for
18  *    monetary gain.
19  *
20  * THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
24  * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
26  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
27  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
30  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  *
33  * Please inquire about commercial licensing options at
34  * [email protected]
35  *
36  */
37 
38 #define BTSTACK_FILE__ "rfcomm.c"
39 
40 /*
41  *  rfcomm.c
42  */
43 
44 #include <stdio.h>
45 #include <stdlib.h>
46 #include <string.h> // memcpy
47 #include <stdint.h>
48 
49 #include "bluetooth_sdp.h"
50 #include "btstack_debug.h"
51 #include "btstack_event.h"
52 #include "btstack_memory.h"
53 #include "btstack_util.h"
54 #include "classic/core.h"
55 #include "classic/rfcomm.h"
56 #include "hci.h"
57 #include "hci_cmd.h"
58 #include "hci_dump.h"
59 #include "l2cap.h"
60 
61 // workaround for missing PRIxPTR on mspgcc (16/20-bit MCU)
62 #ifndef PRIxPTR
63 #if defined(__MSP430X__)  &&  defined(__MSP430X_LARGE__)
64 #define PRIxPTR "lx"
65 #else
66 #define PRIxPTR "x"
67 #endif
68 #endif
69 
70 // ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM requires ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE
71 #ifdef ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM
72 #ifdef ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE
73 #define RFCOMM_USE_OUTGOING_BUFFER
74 #define RFCOMM_USE_ERTM
75 #else
76 #error "ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM requires ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE. "
77 #error "Please disable ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM, or, "
78 #error "enable ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE"
79 #endif
80 #endif
81 
82 #define RFCOMM_MULIPLEXER_TIMEOUT_MS 60000
83 
84 #define RFCOMM_CREDITS 10
85 
86 // FCS calc
87 #define BT_RFCOMM_CODE_WORD         0xE0 // pol = x8+x2+x1+1
88 #define BT_RFCOMM_CRC_CHECK_LEN     3
89 #define BT_RFCOMM_UIHCRC_CHECK_LEN  2
90 
91 
92 typedef enum {
93     CH_EVT_RCVD_SABM = 1,
94     CH_EVT_RCVD_UA,
95     CH_EVT_RCVD_PN,
96     CH_EVT_RCVD_PN_RSP,
97     CH_EVT_RCVD_DISC,
98     CH_EVT_RCVD_DM,
99     CH_EVT_RCVD_MSC_CMD,
100     CH_EVT_RCVD_MSC_RSP,
101     CH_EVT_RCVD_NSC_RSP,
102     CH_EVT_RCVD_RLS_CMD,
103     CH_EVT_RCVD_RLS_RSP,
104     CH_EVT_RCVD_RPN_CMD,
105     CH_EVT_RCVD_RPN_REQ,
106     CH_EVT_RCVD_CREDITS,
107     CH_EVT_MULTIPLEXER_READY,
108     CH_EVT_READY_TO_SEND,
109 } RFCOMM_CHANNEL_EVENT;
110 
111 typedef struct rfcomm_channel_event {
112     RFCOMM_CHANNEL_EVENT type;
113     uint16_t dummy; // force rfcomm_channel_event to be 2-byte aligned -> avoid -Wcast-align warning
114 } rfcomm_channel_event_t;
115 
116 typedef struct rfcomm_channel_event_pn {
117     rfcomm_channel_event_t super;
118     uint16_t max_frame_size;
119     uint8_t  priority;
120     uint8_t  credits_outgoing;
121 } rfcomm_channel_event_pn_t;
122 
123 typedef struct rfcomm_channel_event_rpn {
124     rfcomm_channel_event_t super;
125     rfcomm_rpn_data_t data;
126 } rfcomm_channel_event_rpn_t;
127 
128 typedef struct rfcomm_channel_event_rls {
129     rfcomm_channel_event_t super;
130     uint8_t line_status;
131 } rfcomm_channel_event_rls_t;
132 
133 typedef struct rfcomm_channel_event_msc {
134     rfcomm_channel_event_t super;
135     uint8_t modem_status;
136 } rfcomm_channel_event_msc_t;
137 
138 
139 // global rfcomm data
140 static uint16_t      rfcomm_client_cid_generator;  // used for client channel IDs
141 
142 // linked lists for all
143 static btstack_linked_list_t rfcomm_multiplexers = NULL;
144 static btstack_linked_list_t rfcomm_channels = NULL;
145 static btstack_linked_list_t rfcomm_services = NULL;
146 
147 static gap_security_level_t rfcomm_security_level;
148 
149 #ifdef RFCOMM_USE_ERTM
150 static uint16_t ertm_id;
151 void (*rfcomm_ertm_request_callback)(rfcomm_ertm_request_t * request);
152 void (*rfcomm_ertm_released_callback)(uint16_t ertm_id);
153 #endif
154 
155 #ifdef RFCOMM_USE_OUTGOING_BUFFER
156 static uint8_t outgoing_buffer[1030];
157 #endif
158 
159 static int  rfcomm_channel_can_send(rfcomm_channel_t * channel);
160 static int  rfcomm_channel_ready_for_open(rfcomm_channel_t *channel);
161 static int rfcomm_channel_ready_to_send(rfcomm_channel_t * channel);
162 static void rfcomm_channel_state_machine_with_channel(rfcomm_channel_t *channel, const rfcomm_channel_event_t *event, int * out_channel_valid);
163 static void rfcomm_channel_state_machine_with_dlci(rfcomm_multiplexer_t * multiplexer, uint8_t dlci, const rfcomm_channel_event_t *event);
164 static void rfcomm_emit_can_send_now(rfcomm_channel_t *channel);
165 static int rfcomm_multiplexer_ready_to_send(rfcomm_multiplexer_t * multiplexer);
166 static void rfcomm_multiplexer_state_machine(rfcomm_multiplexer_t * multiplexer, RFCOMM_MULTIPLEXER_EVENT event);
167 
168 // MARK: RFCOMM CLIENT EVENTS
169 
170 // data: event (8), len(8), address(48), channel (8), rfcomm_cid (16)
171 static void rfcomm_emit_connection_request(rfcomm_channel_t *channel) {
172     log_info("RFCOMM_EVENT_INCOMING_CONNECTION addr %s channel #%u cid 0x%02x",
173              bd_addr_to_str(channel->multiplexer->remote_addr), channel->dlci>>1, channel->rfcomm_cid);
174     uint8_t event[11];
175     event[0] = RFCOMM_EVENT_INCOMING_CONNECTION;
176     event[1] = sizeof(event) - 2;
177     reverse_bd_addr(channel->multiplexer->remote_addr, &event[2]);
178     event[8] = channel->dlci >> 1;
179     little_endian_store_16(event, 9, channel->rfcomm_cid);
180     hci_dump_packet(HCI_EVENT_PACKET, 0, event, sizeof(event));
181 	(channel->packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
182 }
183 
184 // API Change: BTstack-0.3.50x uses
185 // data: event(8), len(8), status (8), address (48), server channel(8), rfcomm_cid(16), max frame size(16)
186 // next Cydia release will use SVN version of this
187 // data: event(8), len(8), status (8), address (48), handle (16), server channel(8), rfcomm_cid(16), max frame size(16)
188 static void rfcomm_emit_channel_opened(rfcomm_channel_t *channel, uint8_t status) {
189     log_info("RFCOMM_EVENT_CHANNEL_OPENED status 0x%x addr %s handle 0x%x channel #%u cid 0x%02x mtu %u",
190              status, bd_addr_to_str(channel->multiplexer->remote_addr), channel->multiplexer->con_handle,
191              channel->dlci>>1, channel->rfcomm_cid, channel->max_frame_size);
192     uint8_t event[18];
193     uint8_t pos = 0;
194     event[pos++] = RFCOMM_EVENT_CHANNEL_OPENED;  // 0
195     event[pos++] = sizeof(event) - 2;                   // 1
196     event[pos++] = status;                              // 2
197     reverse_bd_addr(channel->multiplexer->remote_addr, &event[pos]); pos += 6; // 3
198     little_endian_store_16(event,  pos, channel->multiplexer->con_handle);   pos += 2; // 9
199 	event[pos++] = channel->dlci >> 1;                                      // 11
200 	little_endian_store_16(event, pos, channel->rfcomm_cid); pos += 2;                 // 12 - channel ID
201 	little_endian_store_16(event, pos, channel->max_frame_size); pos += 2;   // max frame size
202     event[pos++] = channel->service ? 1 : 0;    // linked to service -> incoming
203     hci_dump_packet(HCI_EVENT_PACKET, 0, event, sizeof(event));
204 	(channel->packet_handler)(HCI_EVENT_PACKET, 0, event, pos);
205 
206     // if channel opened successfully, also send can send now if possible
207     if (status) return;
208     if (rfcomm_channel_can_send(channel)){
209         rfcomm_emit_can_send_now(channel);
210     }
211 }
212 
213 // data: event(8), len(8), rfcomm_cid(16)
214 static void rfcomm_emit_channel_closed(rfcomm_channel_t * channel) {
215     log_info("RFCOMM_EVENT_CHANNEL_CLOSED cid 0x%02x", channel->rfcomm_cid);
216     uint8_t event[4];
217     event[0] = RFCOMM_EVENT_CHANNEL_CLOSED;
218     event[1] = sizeof(event) - 2;
219     little_endian_store_16(event, 2, channel->rfcomm_cid);
220     hci_dump_packet(HCI_EVENT_PACKET, 0, event, sizeof(event));
221 	(channel->packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
222 }
223 
224 static void rfcomm_emit_remote_line_status(rfcomm_channel_t *channel, uint8_t line_status){
225     log_info("RFCOMM_EVENT_REMOTE_LINE_STATUS cid 0x%02x c, line status 0x%x", channel->rfcomm_cid, line_status);
226     uint8_t event[5];
227     event[0] = RFCOMM_EVENT_REMOTE_LINE_STATUS;
228     event[1] = sizeof(event) - 2;
229     little_endian_store_16(event, 2, channel->rfcomm_cid);
230     event[4] = line_status;
231     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
232     (channel->packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
233 }
234 
235 static void rfcomm_emit_port_configuration(rfcomm_channel_t *channel){
236     // notify client about new settings
237     uint8_t event[2+sizeof(rfcomm_rpn_data_t)];
238     event[0] = RFCOMM_EVENT_PORT_CONFIGURATION;
239     event[1] = sizeof(rfcomm_rpn_data_t);
240     memcpy(&event[2], (uint8_t*) &channel->rpn_data, sizeof(rfcomm_rpn_data_t));
241     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
242     (channel->packet_handler)(HCI_EVENT_PACKET, channel->rfcomm_cid, event, sizeof(event));
243 }
244 
245 static void rfcomm_emit_can_send_now(rfcomm_channel_t *channel) {
246     log_debug("RFCOMM_EVENT_CHANNEL_CAN_SEND_NOW local_cid 0x%x", channel->rfcomm_cid);
247     uint8_t event[4];
248     event[0] = RFCOMM_EVENT_CAN_SEND_NOW;
249     event[1] = sizeof(event) - 2;
250     little_endian_store_16(event, 2, channel->rfcomm_cid);
251     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
252     (channel->packet_handler)(HCI_EVENT_PACKET, channel->rfcomm_cid, event, sizeof(event));
253 }
254 
255 // MARK RFCOMM RPN DATA HELPER
256 static void rfcomm_rpn_data_set_defaults(rfcomm_rpn_data_t * rpn_data){
257         rpn_data->baud_rate = RPN_BAUD_9600;  /* 9600 bps */
258         rpn_data->flags = 0x03;               /* 8-n-1 */
259         rpn_data->flow_control = 0;           /* no flow control */
260         rpn_data->xon  = 0xd1;                /* XON */
261         rpn_data->xoff = 0xd3;                /* XOFF */
262         rpn_data->parameter_mask_0 = 0x7f;    /* parameter mask, all values set */
263         rpn_data->parameter_mask_1 = 0x3f;    /* parameter mask, all values set */
264 }
265 
266 static void rfcomm_rpn_data_update(rfcomm_rpn_data_t * dest, rfcomm_rpn_data_t * src){
267     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_BAUD){
268         dest->baud_rate = src->baud_rate;
269     }
270     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_DATA_BITS){
271         dest->flags = (dest->flags & 0xfc) | (src->flags & 0x03);
272     }
273     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_STOP_BITS){
274         dest->flags = (dest->flags & 0xfb) | (src->flags & 0x04);
275     }
276     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_PARITY){
277         dest->flags = (dest->flags & 0xf7) | (src->flags & 0x08);
278     }
279     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_PARITY_TYPE){
280         dest->flags = (dest->flags & 0xfc) | (src->flags & 0x30);
281     }
282     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_XON_CHAR){
283         dest->xon = src->xon;
284     }
285     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_XOFF_CHAR){
286         dest->xoff = src->xoff;
287     }
288     int i;
289     for (i=0; i < 6 ; i++){
290         uint8_t mask = 1 << i;
291         if (src->parameter_mask_1 & mask){
292             dest->flags = (dest->flags & ~mask) | (src->flags & mask);
293         }
294     }
295     // always copy parameter mask, too. informative for client, needed for response
296     dest->parameter_mask_0 = src->parameter_mask_0;
297     dest->parameter_mask_1 = src->parameter_mask_1;
298 }
299 // MARK: RFCOMM MULTIPLEXER HELPER
300 
301 static uint16_t rfcomm_max_frame_size_for_l2cap_mtu(uint16_t l2cap_mtu){
302     // Assume RFCOMM header without credits and 2 byte (14 bit) length field
303     uint16_t max_frame_size = l2cap_mtu - 5;
304     log_info("rfcomm_max_frame_size_for_l2cap_mtu:  %u -> %u", l2cap_mtu, max_frame_size);
305     return max_frame_size;
306 }
307 
308 static void rfcomm_multiplexer_initialize(rfcomm_multiplexer_t *multiplexer){
309     multiplexer->state = RFCOMM_MULTIPLEXER_CLOSED;
310     multiplexer->fcon = 1;
311     multiplexer->send_dm_for_dlci = 0;
312     multiplexer->max_frame_size = rfcomm_max_frame_size_for_l2cap_mtu(l2cap_max_mtu());
313     multiplexer->test_data_len = 0;
314     multiplexer->nsc_command = 0;
315 }
316 
317 static rfcomm_multiplexer_t * rfcomm_multiplexer_create_for_addr(bd_addr_t addr){
318 
319     // alloc structure
320     rfcomm_multiplexer_t * multiplexer = btstack_memory_rfcomm_multiplexer_get();
321     if (!multiplexer) return NULL;
322 
323     // fill in
324     rfcomm_multiplexer_initialize(multiplexer);
325     bd_addr_copy(multiplexer->remote_addr, addr);
326 
327     // add to services list
328     btstack_linked_list_add(&rfcomm_multiplexers, (btstack_linked_item_t *) multiplexer);
329 
330     return multiplexer;
331 }
332 
333 static rfcomm_multiplexer_t * rfcomm_multiplexer_for_addr(bd_addr_t addr){
334     btstack_linked_item_t *it;
335     for (it = (btstack_linked_item_t *) rfcomm_multiplexers; it ; it = it->next){
336         rfcomm_multiplexer_t * multiplexer = ((rfcomm_multiplexer_t *) it);
337         // ignore multiplexer in shutdown
338         if (multiplexer->state == RFCOMM_MULTIPLEXER_SHUTTING_DOWN) continue;
339         if (bd_addr_cmp(addr, multiplexer->remote_addr) == 0) {
340             return multiplexer;
341         };
342     }
343     return NULL;
344 }
345 
346 static rfcomm_multiplexer_t * rfcomm_multiplexer_for_l2cap_cid(uint16_t l2cap_cid) {
347     btstack_linked_item_t *it;
348     for (it = (btstack_linked_item_t *) rfcomm_multiplexers; it ; it = it->next){
349         rfcomm_multiplexer_t * multiplexer = ((rfcomm_multiplexer_t *) it);
350         if (multiplexer->l2cap_cid == l2cap_cid) {
351             return multiplexer;
352         };
353     }
354     return NULL;
355 }
356 
357 static int rfcomm_multiplexer_has_channels(rfcomm_multiplexer_t * multiplexer){
358     btstack_linked_item_t *it;
359     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
360         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
361         if (channel->multiplexer == multiplexer) {
362             return 1;
363         }
364     }
365     return 0;
366 }
367 
368 // MARK: RFCOMM CHANNEL HELPER
369 
370 static void rfcomm_dump_channels(void){
371     btstack_linked_item_t * it;
372     int channels = 0;
373     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
374         rfcomm_channel_t * channel = (rfcomm_channel_t *) it;
375         log_info("Channel #%u: addr %p, state %u", channels, channel, channel->state);
376         channels++;
377     }
378 }
379 
380 static void rfcomm_channel_initialize(rfcomm_channel_t *channel, rfcomm_multiplexer_t *multiplexer,
381                                rfcomm_service_t *service, uint8_t server_channel){
382 
383     // don't use 0 as channel id
384     if (rfcomm_client_cid_generator == 0) ++rfcomm_client_cid_generator;
385 
386     // set defaults for port configuration (even for services)
387     rfcomm_rpn_data_set_defaults(&channel->rpn_data);
388 
389     channel->state            = RFCOMM_CHANNEL_CLOSED;
390     channel->state_var        = RFCOMM_CHANNEL_STATE_VAR_NONE;
391 
392     channel->multiplexer      = multiplexer;
393     channel->rfcomm_cid       = rfcomm_client_cid_generator++;
394     channel->max_frame_size   = multiplexer->max_frame_size;
395 
396     channel->credits_incoming = 0;
397     channel->credits_outgoing = 0;
398 
399     // incoming flow control not active
400     channel->new_credits_incoming  = RFCOMM_CREDITS;
401     channel->incoming_flow_control = 0;
402 
403     channel->rls_line_status       = RFCOMM_RLS_STATUS_INVALID;
404 
405     channel->service = service;
406 	if (service) {
407 		// incoming connection
408     	channel->dlci = (server_channel << 1) |  multiplexer->outgoing;
409         if (channel->max_frame_size > service->max_frame_size) {
410             channel->max_frame_size = service->max_frame_size;
411         }
412         channel->incoming_flow_control = service->incoming_flow_control;
413         channel->new_credits_incoming  = service->incoming_initial_credits;
414         channel->packet_handler        = service->packet_handler;
415 	} else {
416 		// outgoing connection
417 		channel->dlci = (server_channel << 1) | (multiplexer->outgoing ^ 1);
418 	}
419 }
420 
421 // service == NULL -> outgoing channel
422 static rfcomm_channel_t * rfcomm_channel_create(rfcomm_multiplexer_t * multiplexer,
423                                                 rfcomm_service_t * service, uint8_t server_channel){
424 
425     log_info("rfcomm_channel_create for service %p, channel %u --- list of channels:", service, server_channel);
426     rfcomm_dump_channels();
427 
428     // alloc structure
429     rfcomm_channel_t * channel = btstack_memory_rfcomm_channel_get();
430     if (!channel) return NULL;
431 
432     // fill in
433     rfcomm_channel_initialize(channel, multiplexer, service, server_channel);
434 
435     // add to services list
436     btstack_linked_list_add(&rfcomm_channels, (btstack_linked_item_t *) channel);
437 
438     return channel;
439 }
440 
441 static void rfcomm_notify_channel_can_send(void){
442     btstack_linked_list_iterator_t it;
443     btstack_linked_list_iterator_init(&it, &rfcomm_channels);
444     while (btstack_linked_list_iterator_has_next(&it)){
445         rfcomm_channel_t * channel = (rfcomm_channel_t *) btstack_linked_list_iterator_next(&it);
446         if (!channel->waiting_for_can_send_now) continue; // didn't try to send yet
447         if (!rfcomm_channel_can_send(channel)) continue;  // or cannot yet either
448 
449         channel->waiting_for_can_send_now = 0;
450         rfcomm_emit_can_send_now(channel);
451     }
452 }
453 
454 static rfcomm_channel_t * rfcomm_channel_for_rfcomm_cid(uint16_t rfcomm_cid){
455     btstack_linked_item_t *it;
456     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
457         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
458         if (channel->rfcomm_cid == rfcomm_cid) {
459             return channel;
460         };
461     }
462     return NULL;
463 }
464 
465 static rfcomm_channel_t * rfcomm_channel_for_multiplexer_and_dlci(rfcomm_multiplexer_t * multiplexer, uint8_t dlci){
466     btstack_linked_item_t *it;
467     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
468         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
469         if (channel->dlci == dlci && channel->multiplexer == multiplexer) {
470             return channel;
471         };
472     }
473     return NULL;
474 }
475 
476 static rfcomm_service_t * rfcomm_service_for_channel(uint8_t server_channel){
477     btstack_linked_item_t *it;
478     for (it = (btstack_linked_item_t *) rfcomm_services; it ; it = it->next){
479         rfcomm_service_t * service = ((rfcomm_service_t *) it);
480         if ( service->server_channel == server_channel){
481             return service;
482         };
483     }
484     return NULL;
485 }
486 
487 // MARK: RFCOMM SEND
488 
489 /**
490  * @param credits - only used for RFCOMM flow control in UIH wiht P/F = 1
491  */
492 static int rfcomm_send_packet_for_multiplexer(rfcomm_multiplexer_t *multiplexer, uint8_t address, uint8_t control, uint8_t credits, uint8_t *data, uint16_t len){
493 
494     if (!l2cap_can_send_packet_now(multiplexer->l2cap_cid)) return BTSTACK_ACL_BUFFERS_FULL;
495 
496 #ifdef RFCOMM_USE_OUTGOING_BUFFER
497     uint8_t * rfcomm_out_buffer = outgoing_buffer;
498 #else
499     l2cap_reserve_packet_buffer();
500     uint8_t * rfcomm_out_buffer = l2cap_get_outgoing_buffer();
501 #endif
502 
503 	uint16_t pos = 0;
504 	uint8_t crc_fields = 3;
505 
506 	rfcomm_out_buffer[pos++] = address;
507 	rfcomm_out_buffer[pos++] = control;
508 
509 	// length field can be 1 or 2 octets
510 	if (len < 128){
511 		rfcomm_out_buffer[pos++] = (len << 1)| 1;     // bits 0-6
512 	} else {
513 		rfcomm_out_buffer[pos++] = (len & 0x7f) << 1; // bits 0-6
514 		rfcomm_out_buffer[pos++] = len >> 7;          // bits 7-14
515 		crc_fields++;
516 	}
517 
518 	// add credits for UIH frames when PF bit is set
519 	if (control == BT_RFCOMM_UIH_PF){
520 		rfcomm_out_buffer[pos++] = credits;
521 	}
522 
523 	// copy actual data
524 	if (len) {
525 		memcpy(&rfcomm_out_buffer[pos], data, len);
526 		pos += len;
527 	}
528 
529 	// UIH frames only calc FCS over address + control (5.1.1)
530 	if ((control & 0xef) == BT_RFCOMM_UIH){
531 		crc_fields = 2;
532 	}
533 	rfcomm_out_buffer[pos++] =  btstack_crc8_calc(rfcomm_out_buffer, crc_fields); // calc fcs
534 
535 #ifdef RFCOMM_USE_OUTGOING_BUFFER
536     int err = l2cap_send(multiplexer->l2cap_cid, rfcomm_out_buffer, pos);
537 #else
538     int err = l2cap_send_prepared(multiplexer->l2cap_cid, pos);
539 #endif
540 
541     return err;
542 }
543 
544 // simplified version of rfcomm_send_packet_for_multiplexer for prepared rfcomm packet (UIH, 2 byte len, no credits)
545 static int rfcomm_send_uih_prepared(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint16_t len){
546 
547     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) | (dlci << 2);
548     uint8_t control = BT_RFCOMM_UIH;
549 
550 #ifdef RFCOMM_USE_OUTGOING_BUFFER
551     uint8_t * rfcomm_out_buffer = outgoing_buffer;
552 #else
553     uint8_t * rfcomm_out_buffer = l2cap_get_outgoing_buffer();
554 #endif
555 
556     uint16_t pos = 0;
557     rfcomm_out_buffer[pos++] = address;
558     rfcomm_out_buffer[pos++] = control;
559     rfcomm_out_buffer[pos++] = (len & 0x7f) << 1; // bits 0-6
560     rfcomm_out_buffer[pos++] = len >> 7;          // bits 7-14
561 
562     // actual data is already in place
563     pos += len;
564 
565     // UIH frames only calc FCS over address + control (5.1.1)
566     rfcomm_out_buffer[pos++] =  btstack_crc8_calc(rfcomm_out_buffer, 2); // calc fcs
567 
568 #ifdef RFCOMM_USE_OUTGOING_BUFFER
569     int err = l2cap_send(multiplexer->l2cap_cid, rfcomm_out_buffer, pos);
570 #else
571     int err = l2cap_send_prepared(multiplexer->l2cap_cid, pos);
572 #endif
573 
574     return err;
575 }
576 
577 // C/R Flag in Address
578 // - terms: initiator = station that creates multiplexer with SABM
579 // - terms: responder = station that responds to multiplexer setup with UA
580 // "For SABM, UA, DM and DISC frames C/R bit is set according to Table 1 in GSM 07.10, section 5.2.1.2"
581 //    - command initiator = 1 /response responder = 1
582 //    - command responder = 0 /response initiator = 0
583 // "For UIH frames, the C/R bit is always set according to section 5.4.3.1 in GSM 07.10.
584 //  This applies independently of what is contained wthin the UIH frames, either data or control messages."
585 //    - c/r = 1 for frames by initiating station, 0 = for frames by responding station
586 
587 // C/R Flag in Message
588 // "In the message level, the C/R bit in the command type field is set as stated in section 5.4.6.2 in GSM 07.10."
589 //   - If the C/R bit is set to 1 the message is a command
590 //   - if it is set to 0 the message is a response.
591 
592 // temp/old messge construction
593 
594 // new object oriented version
595 static int rfcomm_send_sabm(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
596 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) | (dlci << 2);   // command
597     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_SABM, 0, NULL, 0);
598 }
599 
600 static int rfcomm_send_disc(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
601 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) | (dlci << 2);  // command
602     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_DISC, 0, NULL, 0);
603 }
604 
605 static int rfcomm_send_ua(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
606 	uint8_t address = (1 << 0) | ((multiplexer->outgoing ^ 1) << 1) | (dlci << 2); // response
607     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UA, 0, NULL, 0);
608 }
609 
610 static int rfcomm_send_dm_pf(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
611 	uint8_t address = (1 << 0) | ((multiplexer->outgoing ^ 1) << 1) | (dlci << 2); // response
612     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_DM_PF, 0, NULL, 0);
613 }
614 
615 static int rfcomm_send_uih_fc_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t fcon) {
616     uint8_t address = (1 << 0) | (multiplexer->outgoing<< 1);
617     uint8_t payload[2];
618     uint8_t pos = 0;
619     payload[pos++] = fcon ? BT_RFCOMM_FCON_RSP : BT_RFCOMM_FCOFF_RSP;
620     payload[pos++] = (0 << 1) | 1;  // len
621     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
622 }
623 
624 // static int rfcomm_send_uih_test_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t * data, uint16_t len) {
625 //     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
626 //     uint8_t payload[2+len];
627 //     uint8_t pos = 0;
628 //     payload[pos++] = BT_RFCOMM_TEST_CMD;
629 //     payload[pos++] = (len + 1) << 1 | 1;  // len
630 //     memcpy(&payload[pos], data, len);
631 //     pos += len;
632 //     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
633 // }
634 
635 static int rfcomm_send_uih_test_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t * data, uint16_t len) {
636     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
637     uint8_t payload[2+RFCOMM_TEST_DATA_MAX_LEN];
638     uint8_t pos = 0;
639     payload[pos++] = BT_RFCOMM_TEST_RSP;
640     if (len > RFCOMM_TEST_DATA_MAX_LEN) {
641         len = RFCOMM_TEST_DATA_MAX_LEN;
642     }
643     payload[pos++] = (len << 1) | 1;  // len
644     memcpy(&payload[pos], data, len);
645     pos += len;
646     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
647 }
648 
649 static int rfcomm_send_uih_msc_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t signals) {
650 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
651 	uint8_t payload[4];
652 	uint8_t pos = 0;
653 	payload[pos++] = BT_RFCOMM_MSC_CMD;
654 	payload[pos++] = (2 << 1) | 1;  // len
655 	payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
656 	payload[pos++] = signals;
657 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
658 }
659 
660 static int rfcomm_send_uih_msc_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t signals) {
661 	uint8_t address = (1 << 0) | (multiplexer->outgoing<< 1);
662 	uint8_t payload[4];
663 	uint8_t pos = 0;
664 	payload[pos++] = BT_RFCOMM_MSC_RSP;
665 	payload[pos++] = (2 << 1) | 1;  // len
666 	payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
667 	payload[pos++] = signals;
668 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
669 }
670 
671 static int rfcomm_send_uih_nsc_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t command) {
672     uint8_t address = (1 << 0) | (multiplexer->outgoing<< 1);
673     uint8_t payload[3];
674     uint8_t pos = 0;
675     payload[pos++] = BT_RFCOMM_NSC_RSP;
676     payload[pos++] = (1 << 1) | 1;  // len
677     payload[pos++] = command;
678     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
679 }
680 
681 static int rfcomm_send_uih_pn_command(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint16_t max_frame_size){
682 	uint8_t payload[10];
683 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
684 	uint8_t pos = 0;
685 	payload[pos++] = BT_RFCOMM_PN_CMD;
686 	payload[pos++] = (8 << 1) | 1;  // len
687 	payload[pos++] = dlci;
688 	payload[pos++] = 0xf0; // pre-defined for Bluetooth, see 5.5.3 of TS 07.10 Adaption for RFCOMM
689 	payload[pos++] = 0; // priority
690 	payload[pos++] = 0; // max 60 seconds ack
691 	payload[pos++] = max_frame_size & 0xff; // max framesize low
692 	payload[pos++] = max_frame_size >> 8;   // max framesize high
693 	payload[pos++] = 0x00; // number of retransmissions
694 	payload[pos++] = 0x00; // (unused error recovery window) initial number of credits
695 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
696 }
697 
698 // "The response may not change the DLCI, the priority, the convergence layer, or the timer value." rfcomm_tutorial.pdf
699 static int rfcomm_send_uih_pn_response(rfcomm_multiplexer_t *multiplexer, uint8_t dlci,
700                                        uint8_t priority, uint16_t max_frame_size){
701 	uint8_t payload[10];
702 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
703 	uint8_t pos = 0;
704 	payload[pos++] = BT_RFCOMM_PN_RSP;
705 	payload[pos++] = (8 << 1) | 1;  // len
706 	payload[pos++] = dlci;
707 	payload[pos++] = 0xe0; // pre defined for Bluetooth, see 5.5.3 of TS 07.10 Adaption for RFCOMM
708 	payload[pos++] = priority; // priority
709 	payload[pos++] = 0; // max 60 seconds ack
710 	payload[pos++] = max_frame_size & 0xff; // max framesize low
711 	payload[pos++] = max_frame_size >> 8;   // max framesize high
712 	payload[pos++] = 0x00; // number of retransmissions
713 	payload[pos++] = 0x00; // (unused error recovery window) initial number of credits
714 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
715 }
716 
717 static int rfcomm_send_uih_rls_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t line_status) {
718     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
719     uint8_t payload[4];
720     uint8_t pos = 0;
721     payload[pos++] = BT_RFCOMM_RLS_CMD;
722     payload[pos++] = (2 << 1) | 1;  // len
723     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
724     payload[pos++] = line_status;
725     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
726 }
727 
728 static int rfcomm_send_uih_rls_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t line_status) {
729     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
730     uint8_t payload[4];
731     uint8_t pos = 0;
732     payload[pos++] = BT_RFCOMM_RLS_RSP;
733     payload[pos++] = (2 << 1) | 1;  // len
734     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
735     payload[pos++] = line_status;
736     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
737 }
738 
739 static int rfcomm_send_uih_rpn_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, rfcomm_rpn_data_t *rpn_data) {
740     uint8_t payload[10];
741     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
742     uint8_t pos = 0;
743     payload[pos++] = BT_RFCOMM_RPN_CMD;
744     payload[pos++] = (8 << 1) | 1;  // len
745     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
746     payload[pos++] = rpn_data->baud_rate;
747     payload[pos++] = rpn_data->flags;
748     payload[pos++] = rpn_data->flow_control;
749     payload[pos++] = rpn_data->xon;
750     payload[pos++] = rpn_data->xoff;
751     payload[pos++] = rpn_data->parameter_mask_0;
752     payload[pos++] = rpn_data->parameter_mask_1;
753     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
754 }
755 
756 static int rfcomm_send_uih_rpn_req(rfcomm_multiplexer_t *multiplexer, uint8_t dlci) {
757     uint8_t payload[3];
758     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
759     uint8_t pos = 0;
760     payload[pos++] = BT_RFCOMM_RPN_CMD;
761     payload[pos++] = (1 << 1) | 1;  // len
762     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
763     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
764 }
765 
766 static int rfcomm_send_uih_rpn_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, rfcomm_rpn_data_t *rpn_data) {
767 	uint8_t payload[10];
768 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
769 	uint8_t pos = 0;
770 	payload[pos++] = BT_RFCOMM_RPN_RSP;
771 	payload[pos++] = (8 << 1) | 1;  // len
772 	payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
773 	payload[pos++] = rpn_data->baud_rate;
774 	payload[pos++] = rpn_data->flags;
775 	payload[pos++] = rpn_data->flow_control;
776 	payload[pos++] = rpn_data->xon;
777 	payload[pos++] = rpn_data->xoff;
778 	payload[pos++] = rpn_data->parameter_mask_0;
779 	payload[pos++] = rpn_data->parameter_mask_1;
780 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
781 }
782 
783 static void rfcomm_send_uih_credits(rfcomm_multiplexer_t *multiplexer, uint8_t dlci,  uint8_t credits){
784     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) |  (dlci << 2);
785     rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH_PF, credits, NULL, 0);
786 }
787 
788 // depending on channel state emit channel opened with status or channel closed
789 static void rfcomm_channel_emit_final_event(rfcomm_channel_t * channel, uint8_t status){
790     // emit appropriate events
791     switch(channel->state){
792         case RFCOMM_CHANNEL_OPEN:
793         case RFCOMM_CHANNEL_W4_UA_AFTER_DISC:
794             rfcomm_emit_channel_closed(channel);
795             break;
796         case RFCOMM_CHANNEL_SEND_UA_AFTER_DISC:
797             // remote didn't wait until we send the UA disc
798             // close event already emitted
799             break;
800         default:
801             rfcomm_emit_channel_opened(channel, status);
802             break;
803     }
804 }
805 
806 // MARK: RFCOMM MULTIPLEXER
807 static void rfcomm_multiplexer_stop_timer(rfcomm_multiplexer_t * multiplexer){
808     if (multiplexer->timer_active) {
809         btstack_run_loop_remove_timer(&multiplexer->timer);
810         multiplexer->timer_active = 0;
811     }
812 }
813 static void rfcomm_multiplexer_free(rfcomm_multiplexer_t * multiplexer){
814     btstack_linked_list_remove( &rfcomm_multiplexers, (btstack_linked_item_t *) multiplexer);
815     btstack_memory_rfcomm_multiplexer_free(multiplexer);
816 }
817 
818 static void rfcomm_multiplexer_finalize(rfcomm_multiplexer_t * multiplexer){
819     // remove (potential) timer
820     rfcomm_multiplexer_stop_timer(multiplexer);
821 
822     // close and remove all channels
823     btstack_linked_item_t *it = (btstack_linked_item_t *) &rfcomm_channels;
824     while (it->next){
825         rfcomm_channel_t * channel = (rfcomm_channel_t *) it->next;
826         if (channel->multiplexer == multiplexer) {
827             // emit open with status or closed
828             rfcomm_channel_emit_final_event(channel, RFCOMM_MULTIPLEXER_STOPPED);
829             // remove from list
830             it->next = it->next->next;
831             // free channel struct
832             btstack_memory_rfcomm_channel_free(channel);
833         } else {
834             it = it->next;
835         }
836     }
837 
838     // remove mutliplexer
839     rfcomm_multiplexer_free(multiplexer);
840 }
841 
842 static void rfcomm_multiplexer_timer_handler(btstack_timer_source_t *timer){
843     rfcomm_multiplexer_t * multiplexer = (rfcomm_multiplexer_t*) btstack_run_loop_get_timer_context(timer);
844     if (rfcomm_multiplexer_has_channels(multiplexer)) return;
845 
846     log_info("rfcomm_multiplexer_timer_handler timeout: shutting down multiplexer! (no channels)");
847     uint16_t l2cap_cid = multiplexer->l2cap_cid;
848     rfcomm_multiplexer_finalize(multiplexer);
849     l2cap_disconnect(l2cap_cid, 0x13);
850 }
851 
852 static void rfcomm_multiplexer_prepare_idle_timer(rfcomm_multiplexer_t * multiplexer){
853     if (multiplexer->timer_active) {
854         btstack_run_loop_remove_timer(&multiplexer->timer);
855         multiplexer->timer_active = 0;
856     }
857     if (rfcomm_multiplexer_has_channels(multiplexer)) return;
858 
859     // start idle timer for multiplexer timeout check as there are no rfcomm channels yet
860     btstack_run_loop_set_timer(&multiplexer->timer, RFCOMM_MULIPLEXER_TIMEOUT_MS);
861     btstack_run_loop_set_timer_handler(&multiplexer->timer, rfcomm_multiplexer_timer_handler);
862     btstack_run_loop_set_timer_context(&multiplexer->timer, multiplexer);
863     btstack_run_loop_add_timer(&multiplexer->timer);
864     multiplexer->timer_active = 1;
865 }
866 
867 static void rfcomm_multiplexer_opened(rfcomm_multiplexer_t *multiplexer){
868     log_info("Multiplexer up and running");
869     multiplexer->state = RFCOMM_MULTIPLEXER_OPEN;
870 
871     const rfcomm_channel_event_t event = { CH_EVT_MULTIPLEXER_READY, 0};
872 
873     // transition of channels that wait for multiplexer
874     btstack_linked_item_t *it;
875     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
876         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
877         if (channel->multiplexer != multiplexer) continue;
878         int rfcomm_channel_valid = 1;
879         rfcomm_channel_state_machine_with_channel(channel, &event, &rfcomm_channel_valid);
880         if (rfcomm_channel_valid && rfcomm_channel_ready_to_send(channel)){
881             l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
882         }
883     }
884     rfcomm_multiplexer_prepare_idle_timer(multiplexer);
885 
886     // request can send now for multiplexer if ready
887     if (rfcomm_multiplexer_ready_to_send(multiplexer)){
888         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
889     }
890 }
891 
892 static void rfcomm_handle_can_send_now(uint16_t l2cap_cid){
893 
894     log_debug("rfcomm_handle_can_send_now enter: %u", l2cap_cid);
895 
896     btstack_linked_list_iterator_t it;
897     int token_consumed = 0;
898 
899     // forward token to multiplexer
900     btstack_linked_list_iterator_init(&it, &rfcomm_multiplexers);
901     while (!token_consumed && btstack_linked_list_iterator_has_next(&it)){
902         rfcomm_multiplexer_t * multiplexer = (rfcomm_multiplexer_t *) btstack_linked_list_iterator_next(&it);
903         if (multiplexer->l2cap_cid != l2cap_cid) continue;
904         if (rfcomm_multiplexer_ready_to_send(multiplexer)){
905             log_debug("rfcomm_handle_can_send_now enter: multiplexer token");
906             token_consumed = 1;
907             rfcomm_multiplexer_state_machine(multiplexer, MULT_EV_READY_TO_SEND);
908         }
909     }
910 
911     // forward token to channel state machine
912     btstack_linked_list_iterator_init(&it, &rfcomm_channels);
913     while (!token_consumed && btstack_linked_list_iterator_has_next(&it)){
914         rfcomm_channel_t * channel = (rfcomm_channel_t *) btstack_linked_list_iterator_next(&it);
915         if (channel->multiplexer->l2cap_cid != l2cap_cid) continue;
916         // channel state machine
917         if (rfcomm_channel_ready_to_send(channel)){
918             log_debug("rfcomm_handle_can_send_now enter: channel token");
919             token_consumed = 1;
920             const rfcomm_channel_event_t event = { CH_EVT_READY_TO_SEND, 0 };
921             int rfcomm_channel_valid = 1;
922             rfcomm_channel_state_machine_with_channel(channel, &event, &rfcomm_channel_valid);
923         }
924     }
925 
926     // forward token to client
927     btstack_linked_list_iterator_init(&it, &rfcomm_channels);
928     while (!token_consumed && btstack_linked_list_iterator_has_next(&it)){
929         rfcomm_channel_t * channel = (rfcomm_channel_t *) btstack_linked_list_iterator_next(&it);
930         if (channel->multiplexer->l2cap_cid != l2cap_cid) continue;
931         // client waiting for can send now
932         if (!channel->waiting_for_can_send_now)    continue;
933         if ((channel->multiplexer->fcon & 1) == 0) continue;
934         if (!channel->credits_outgoing){
935             log_debug("rfcomm_handle_can_send_now waiting to send but no credits (ignore)");
936             continue;
937         }
938 
939         log_debug("rfcomm_handle_can_send_now enter: client token");
940         token_consumed = 1;
941         channel->waiting_for_can_send_now = 0;
942         rfcomm_emit_can_send_now(channel);
943     }
944 
945     // if token was consumed, request another one
946     if (token_consumed) {
947         l2cap_request_can_send_now_event(l2cap_cid);
948     }
949 
950     log_debug("rfcomm_handle_can_send_now exit");
951 }
952 
953 static void rfcomm_multiplexer_set_state_and_request_can_send_now_event(rfcomm_multiplexer_t * multiplexer, RFCOMM_MULTIPLEXER_STATE state){
954     multiplexer->state = state;
955     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
956 }
957 
958 /**
959  * @return handled packet
960  */
961 static int rfcomm_hci_event_handler(uint8_t *packet, uint16_t size){
962 
963     UNUSED(size);   // ok: handling own l2cap events
964 
965     bd_addr_t event_addr;
966     uint16_t  psm;
967     uint16_t l2cap_cid;
968     hci_con_handle_t con_handle;
969     rfcomm_multiplexer_t *multiplexer = NULL;
970     uint8_t status;
971 
972     switch (hci_event_packet_get_type(packet)) {
973 
974         // accept incoming rfcomm connection if no multiplexer exists yet
975         case L2CAP_EVENT_INCOMING_CONNECTION:
976             // data: event(8), len(8), address(48), handle (16),  psm (16), source cid(16) dest cid(16)
977             reverse_bd_addr(&packet[2], event_addr);
978             con_handle = little_endian_read_16(packet,  8);
979             psm        = little_endian_read_16(packet, 10);
980             l2cap_cid  = little_endian_read_16(packet, 12);
981 
982             if (psm != BLUETOOTH_PROTOCOL_RFCOMM) break;
983 
984             multiplexer = rfcomm_multiplexer_for_addr(event_addr);
985 
986             if (multiplexer) {
987                 log_info("INCOMING_CONNECTION (l2cap_cid 0x%02x) for BLUETOOTH_PROTOCOL_RFCOMM => decline - multiplexer already exists", l2cap_cid);
988                 l2cap_decline_connection(l2cap_cid);
989                 return 1;
990             }
991 
992             // create and inititialize new multiplexer instance (incoming)
993             multiplexer = rfcomm_multiplexer_create_for_addr(event_addr);
994             if (!multiplexer){
995                 log_info("INCOMING_CONNECTION (l2cap_cid 0x%02x) for BLUETOOTH_PROTOCOL_RFCOMM => decline - no memory left", l2cap_cid);
996                 l2cap_decline_connection(l2cap_cid);
997                 return 1;
998             }
999 
1000             multiplexer->con_handle = con_handle;
1001             multiplexer->l2cap_cid = l2cap_cid;
1002             //
1003             multiplexer->state = RFCOMM_MULTIPLEXER_W4_SABM_0;
1004             log_info("L2CAP_EVENT_INCOMING_CONNECTION (l2cap_cid 0x%02x) for BLUETOOTH_PROTOCOL_RFCOMM => accept", l2cap_cid);
1005 
1006 #ifdef RFCOMM_USE_ERTM
1007             // request
1008             rfcomm_ertm_request_t request;
1009             memset(&request, 0, sizeof(rfcomm_ertm_request_t));
1010             memcpy(request.addr, event_addr, 6);
1011             request.ertm_id = ++ertm_id;
1012             if (rfcomm_ertm_request_callback){
1013                 (*rfcomm_ertm_request_callback)(&request);
1014             }
1015             if (request.ertm_config && request.ertm_buffer && request.ertm_buffer_size){
1016                 multiplexer->ertm_id = request.ertm_id;
1017                 l2cap_accept_ertm_connection(l2cap_cid, request.ertm_config, request.ertm_buffer, request.ertm_buffer_size);
1018                 return 1;
1019             }
1020 #endif
1021 
1022             l2cap_accept_connection(l2cap_cid);
1023             return 1;
1024 
1025         // l2cap connection opened -> store l2cap_cid, remote_addr
1026         case L2CAP_EVENT_CHANNEL_OPENED:
1027 
1028             if (little_endian_read_16(packet, 11) != BLUETOOTH_PROTOCOL_RFCOMM) break;
1029 
1030             status = packet[2];
1031             log_info("L2CAP_EVENT_CHANNEL_OPENED for BLUETOOTH_PROTOCOL_RFCOMM, status %u", status);
1032 
1033             // get multiplexer for remote addr
1034             con_handle = little_endian_read_16(packet, 9);
1035             l2cap_cid = little_endian_read_16(packet, 13);
1036             reverse_bd_addr(&packet[3], event_addr);
1037             multiplexer = rfcomm_multiplexer_for_addr(event_addr);
1038             if (!multiplexer) {
1039                 log_error("L2CAP_EVENT_CHANNEL_OPENED but no multiplexer prepared");
1040                 return 1;
1041             }
1042 
1043             // on l2cap open error discard everything
1044             if (status){
1045 
1046                 // remove (potential) timer
1047                 rfcomm_multiplexer_stop_timer(multiplexer);
1048 
1049                 // mark multiplexer as shutting down
1050                 multiplexer->state = RFCOMM_MULTIPLEXER_SHUTTING_DOWN;
1051 
1052                 // emit rfcomm_channel_opened with status and free channel
1053                 // note: repeatedly go over list until full iteration causes no further change
1054                 int done;
1055                 do {
1056                     done = 1;
1057                     btstack_linked_item_t * it = (btstack_linked_item_t *) &rfcomm_channels;
1058                     while (it->next) {
1059                         rfcomm_channel_t * channel = (rfcomm_channel_t *) it->next;
1060                         if (channel->multiplexer == multiplexer){
1061                             done = 0;
1062                             rfcomm_emit_channel_opened(channel, status);
1063                             btstack_linked_list_remove(&rfcomm_channels, (btstack_linked_item_t *) channel);
1064                             btstack_memory_rfcomm_channel_free(channel);
1065                             break;
1066                         } else {
1067                             it = it->next;
1068                         }
1069                     }
1070                 } while (!done);
1071 
1072                 // free multiplexer
1073                 rfcomm_multiplexer_free(multiplexer);
1074                 return 1;
1075             }
1076 
1077             // following could be: rfcom_multiplexer_state_machein(..., EVENT_L2CAP_OPENED)
1078 
1079             if (multiplexer->state == RFCOMM_MULTIPLEXER_W4_CONNECT) {
1080                 log_info("L2CAP_EVENT_CHANNEL_OPENED: outgoing connection");
1081                 // wrong remote addr
1082                 if (bd_addr_cmp(event_addr, multiplexer->remote_addr)) break;
1083                 multiplexer->l2cap_cid = l2cap_cid;
1084                 multiplexer->con_handle = con_handle;
1085                 // send SABM #0
1086                 rfcomm_multiplexer_set_state_and_request_can_send_now_event(multiplexer, RFCOMM_MULTIPLEXER_SEND_SABM_0);
1087 
1088             } else { // multiplexer->state == RFCOMM_MULTIPLEXER_W4_SABM_0
1089 
1090                 // set max frame size based on l2cap MTU
1091                 multiplexer->max_frame_size = rfcomm_max_frame_size_for_l2cap_mtu(little_endian_read_16(packet, 17));
1092             }
1093             return 1;
1094 
1095             // l2cap disconnect -> state = RFCOMM_MULTIPLEXER_CLOSED;
1096 
1097         // Notify channel packet handler if they can send now
1098         case L2CAP_EVENT_CAN_SEND_NOW:
1099             l2cap_cid = l2cap_event_can_send_now_get_local_cid(packet);
1100             rfcomm_handle_can_send_now(l2cap_cid);
1101             return 1;
1102 
1103         case L2CAP_EVENT_CHANNEL_CLOSED:
1104             // data: event (8), len(8), channel (16)
1105             l2cap_cid = little_endian_read_16(packet, 2);
1106             multiplexer = rfcomm_multiplexer_for_l2cap_cid(l2cap_cid);
1107             log_info("L2CAP_EVENT_CHANNEL_CLOSED cid 0x%0x, mult %p", l2cap_cid, multiplexer);
1108             if (!multiplexer) break;
1109             log_info("L2CAP_EVENT_CHANNEL_CLOSED state %u", multiplexer->state);
1110             // no need to call l2cap_disconnect here, as it's already closed
1111             rfcomm_multiplexer_finalize(multiplexer);
1112             return 1;
1113 
1114 #ifdef RFCOMM_USE_ERTM
1115         case L2CAP_EVENT_ERTM_BUFFER_RELEASED:
1116             l2cap_cid = l2cap_event_ertm_buffer_released_get_local_cid(packet);
1117             multiplexer = rfcomm_multiplexer_for_l2cap_cid(l2cap_cid);
1118             if (multiplexer) {
1119                 log_info("buffer for ertm id %u released", multiplexer->ertm_id);
1120                 if (rfcomm_ertm_released_callback){
1121                     (*rfcomm_ertm_released_callback)(multiplexer->ertm_id);
1122                 }
1123             }
1124             break;
1125 #endif
1126 
1127         default:
1128             break;
1129     }
1130     return 0;
1131 }
1132 
1133 static int rfcomm_multiplexer_l2cap_packet_handler(uint16_t channel, uint8_t *packet, uint16_t size){
1134     // get or create a multiplexer for a certain device
1135     rfcomm_multiplexer_t *multiplexer = rfcomm_multiplexer_for_l2cap_cid(channel);
1136     if (!multiplexer) return 0;
1137 
1138     uint16_t l2cap_cid = multiplexer->l2cap_cid;
1139 
1140 	// but only care for multiplexer control channel
1141     uint8_t frame_dlci = packet[0] >> 2;
1142     if (frame_dlci) return 0;
1143     const uint8_t length_offset = (packet[2] & 1) ^ 1;  // to be used for pos >= 3
1144     const uint8_t credit_offset = ((packet[1] & BT_RFCOMM_UIH_PF) == BT_RFCOMM_UIH_PF) ? 1 : 0;   // credits for uih_pf frames
1145     const uint8_t payload_offset = 3 + length_offset + credit_offset;
1146     switch (packet[1]){
1147 
1148         case BT_RFCOMM_SABM:
1149             if (multiplexer->state == RFCOMM_MULTIPLEXER_W4_SABM_0){
1150                 log_info("Received SABM #0");
1151                 multiplexer->outgoing = 0;
1152                 rfcomm_multiplexer_set_state_and_request_can_send_now_event(multiplexer, RFCOMM_MULTIPLEXER_SEND_UA_0);
1153                 return 1;
1154             }
1155             break;
1156 
1157         case BT_RFCOMM_UA:
1158             if (multiplexer->state == RFCOMM_MULTIPLEXER_W4_UA_0) {
1159                 // UA #0 -> send UA #0, state = RFCOMM_MULTIPLEXER_OPEN
1160                 log_info("Received UA #0 ");
1161                 rfcomm_multiplexer_opened(multiplexer);
1162                 return 1;
1163             }
1164             break;
1165 
1166         case BT_RFCOMM_DISC:
1167             // DISC #0 -> send UA #0, close multiplexer
1168             log_info("Received DISC #0, (ougoing = %u)", multiplexer->outgoing);
1169             rfcomm_multiplexer_set_state_and_request_can_send_now_event(multiplexer, RFCOMM_MULTIPLEXER_SEND_UA_0_AND_DISC);
1170             return 1;
1171 
1172         case BT_RFCOMM_DM:
1173             // DM #0 - we shouldn't get this, just give up
1174             log_info("Received DM #0");
1175             log_info("-> Closing down multiplexer");
1176             rfcomm_multiplexer_finalize(multiplexer);
1177             l2cap_disconnect(l2cap_cid, 0x13);
1178             return 1;
1179 
1180         case BT_RFCOMM_UIH:
1181             if (packet[payload_offset] == BT_RFCOMM_CLD_CMD){
1182                 // Multiplexer close down (CLD) -> close mutliplexer
1183                 log_info("Received Multiplexer close down command");
1184                 log_info("-> Closing down multiplexer");
1185                 rfcomm_multiplexer_finalize(multiplexer);
1186                 l2cap_disconnect(l2cap_cid, 0x13);
1187                 return 1;
1188             }
1189             switch (packet[payload_offset]){
1190                 case BT_RFCOMM_CLD_CMD:
1191                      // Multiplexer close down (CLD) -> close mutliplexer
1192                     log_info("Received Multiplexer close down command");
1193                     log_info("-> Closing down multiplexer");
1194                     rfcomm_multiplexer_finalize(multiplexer);
1195                     l2cap_disconnect(l2cap_cid, 0x13);
1196                     return 1;
1197 
1198                 case BT_RFCOMM_FCON_CMD:
1199                     multiplexer->fcon = 0x81;
1200                     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1201                     return 1;
1202 
1203                 case BT_RFCOMM_FCOFF_CMD:
1204                     multiplexer->fcon = 0x80;
1205                     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1206                     return 1;
1207 
1208                 case BT_RFCOMM_TEST_CMD: {
1209                     log_info("Received test command");
1210                     int len = packet[payload_offset+1] >> 1; // length < 125
1211                     if (len > RFCOMM_TEST_DATA_MAX_LEN){
1212                         len = RFCOMM_TEST_DATA_MAX_LEN;
1213                     }
1214                     len = btstack_min(len, size - 1 - payload_offset);  // avoid information leak
1215                     multiplexer->test_data_len = len;
1216                     memcpy(multiplexer->test_data, &packet[payload_offset + 2], len);
1217                     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1218                     return 1;
1219                 }
1220                 default:
1221                     break;
1222             }
1223             break;
1224 
1225         default:
1226             break;
1227 
1228     }
1229     return 0;
1230 }
1231 
1232 static int rfcomm_multiplexer_ready_to_send(rfcomm_multiplexer_t * multiplexer){
1233     if (multiplexer->send_dm_for_dlci) return 1;
1234     if (multiplexer->nsc_command) return 1;
1235     if (multiplexer->fcon & 0x80) return 1;
1236     switch (multiplexer->state){
1237         case RFCOMM_MULTIPLEXER_SEND_SABM_0:
1238         case RFCOMM_MULTIPLEXER_SEND_UA_0:
1239         case RFCOMM_MULTIPLEXER_SEND_UA_0_AND_DISC:
1240             return 1;
1241         case RFCOMM_MULTIPLEXER_OPEN:
1242             if (multiplexer->test_data_len) {
1243                 return 1;
1244             }
1245             break;
1246         default:
1247             break;
1248     }
1249     return 0;
1250 }
1251 
1252 static void rfcomm_multiplexer_state_machine(rfcomm_multiplexer_t * multiplexer, RFCOMM_MULTIPLEXER_EVENT event){
1253 
1254     if (event != MULT_EV_READY_TO_SEND) return;
1255 
1256     uint16_t l2cap_cid = multiplexer->l2cap_cid;
1257 
1258     // process stored DM responses
1259     if (multiplexer->send_dm_for_dlci){
1260         uint8_t dlci = multiplexer->send_dm_for_dlci;
1261         multiplexer->send_dm_for_dlci = 0;
1262         rfcomm_send_dm_pf(multiplexer, dlci);
1263         return;
1264     }
1265 
1266     if (multiplexer->nsc_command){
1267         uint8_t command = multiplexer->nsc_command;
1268         multiplexer->nsc_command = 0;
1269         rfcomm_send_uih_nsc_rsp(multiplexer, command);
1270         return;
1271     }
1272 
1273     if (multiplexer->fcon & 0x80){
1274         multiplexer->fcon &= 0x01;
1275         rfcomm_send_uih_fc_rsp(multiplexer, multiplexer->fcon);
1276 
1277         if (multiplexer->fcon == 0) return;
1278         // trigger client to send again after sending FCon Response
1279         rfcomm_notify_channel_can_send();
1280         return;
1281     }
1282 
1283     switch (multiplexer->state) {
1284         case RFCOMM_MULTIPLEXER_SEND_SABM_0:
1285             log_info("Sending SABM #0 - (multi 0x%p)", multiplexer);
1286             multiplexer->state = RFCOMM_MULTIPLEXER_W4_UA_0;
1287             rfcomm_send_sabm(multiplexer, 0);
1288             break;
1289         case RFCOMM_MULTIPLEXER_SEND_UA_0:
1290             log_info("Sending UA #0");
1291             multiplexer->state = RFCOMM_MULTIPLEXER_OPEN;
1292             rfcomm_send_ua(multiplexer, 0);
1293 
1294             rfcomm_multiplexer_opened(multiplexer);
1295             break;
1296         case RFCOMM_MULTIPLEXER_SEND_UA_0_AND_DISC:
1297             log_info("Sending UA #0");
1298             log_info("Closing down multiplexer");
1299             multiplexer->state = RFCOMM_MULTIPLEXER_CLOSED;
1300             rfcomm_send_ua(multiplexer, 0);
1301 
1302             rfcomm_multiplexer_finalize(multiplexer);
1303             l2cap_disconnect(l2cap_cid, 0x13);
1304             break;
1305         case RFCOMM_MULTIPLEXER_OPEN:
1306             // respond to test command
1307             if (multiplexer->test_data_len){
1308                 int len = multiplexer->test_data_len;
1309                 log_info("Sending TEST Response with %u bytes", len);
1310                 multiplexer->test_data_len = 0;
1311                 rfcomm_send_uih_test_rsp(multiplexer, multiplexer->test_data, len);
1312                 return;
1313             }
1314             break;
1315         default:
1316             break;
1317     }
1318 }
1319 
1320 // MARK: RFCOMM CHANNEL
1321 
1322 static void rfcomm_channel_send_credits(rfcomm_channel_t *channel, uint8_t credits){
1323     channel->credits_incoming += credits;
1324     rfcomm_send_uih_credits(channel->multiplexer, channel->dlci, credits);
1325 }
1326 
1327 static int rfcomm_channel_can_send(rfcomm_channel_t * channel){
1328     if (!channel->credits_outgoing) return 0;
1329     if ((channel->multiplexer->fcon & 1) == 0) return 0;
1330     return l2cap_can_send_packet_now(channel->multiplexer->l2cap_cid);
1331 }
1332 
1333 static void rfcomm_channel_opened(rfcomm_channel_t *rfChannel){
1334 
1335     log_info("rfcomm_channel_opened!");
1336 
1337     rfChannel->state = RFCOMM_CHANNEL_OPEN;
1338     rfcomm_emit_channel_opened(rfChannel, 0);
1339     rfcomm_emit_port_configuration(rfChannel);
1340 
1341     // remove (potential) timer
1342     rfcomm_multiplexer_t *multiplexer = rfChannel->multiplexer;
1343     if (multiplexer->timer_active) {
1344         btstack_run_loop_remove_timer(&multiplexer->timer);
1345         multiplexer->timer_active = 0;
1346     }
1347     // hack for problem detecting authentication failure
1348     multiplexer->at_least_one_connection = 1;
1349 
1350     // request can send now if channel ready
1351     if (rfcomm_channel_ready_to_send(rfChannel)){
1352         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1353     }
1354 }
1355 
1356 static void rfcomm_channel_packet_handler_uih(rfcomm_multiplexer_t *multiplexer, uint8_t * packet, uint16_t size){
1357     const uint8_t frame_dlci = packet[0] >> 2;
1358     const uint8_t length_offset = (packet[2] & 1) ^ 1;  // to be used for pos >= 3
1359     const uint8_t credit_offset = ((packet[1] & BT_RFCOMM_UIH_PF) == BT_RFCOMM_UIH_PF) ? 1 : 0;   // credits for uih_pf frames
1360     const uint8_t payload_offset = 3 + length_offset + credit_offset;
1361     int request_can_send_now = 0;
1362 
1363     rfcomm_channel_t * channel = rfcomm_channel_for_multiplexer_and_dlci(multiplexer, frame_dlci);
1364     if (!channel) return;
1365 
1366     // handle new outgoing credits
1367     if (packet[1] == BT_RFCOMM_UIH_PF) {
1368 
1369         // add them
1370         uint16_t new_credits = packet[3+length_offset];
1371         channel->credits_outgoing += new_credits;
1372         log_info( "RFCOMM data UIH_PF, new credits channel 0x%02x: %u, now %u", channel->rfcomm_cid, new_credits, channel->credits_outgoing);
1373 
1374         // notify channel statemachine
1375         rfcomm_channel_event_t channel_event = { CH_EVT_RCVD_CREDITS, 0 };
1376         log_debug("rfcomm_channel_state_machine_with_channel, waiting_for_can_send_now %u", channel->waiting_for_can_send_now);
1377         int rfcomm_channel_valid = 1;
1378         rfcomm_channel_state_machine_with_channel(channel, &channel_event, &rfcomm_channel_valid);
1379         if (rfcomm_channel_valid){
1380             if (rfcomm_channel_ready_to_send(channel) || channel->waiting_for_can_send_now){
1381                 request_can_send_now = 1;
1382             }
1383         }
1384     }
1385 
1386     // contains payload?
1387     if (size - 1 > payload_offset){
1388 
1389         // log_info( "RFCOMM data UIH_PF, size %u, channel %p", size-payload_offset-1, rfChannel->connection);
1390 
1391         // decrease incoming credit counter
1392         if (channel->credits_incoming > 0){
1393             channel->credits_incoming--;
1394         }
1395 
1396         // deliver payload
1397         (channel->packet_handler)(RFCOMM_DATA_PACKET, channel->rfcomm_cid,
1398                               &packet[payload_offset], size-payload_offset-1);
1399     }
1400 
1401     // automatically provide new credits to remote device, if no incoming flow control
1402     if (!channel->incoming_flow_control && channel->credits_incoming < 5){
1403         channel->new_credits_incoming = RFCOMM_CREDITS;
1404         request_can_send_now = 1;
1405     }
1406 
1407     if (request_can_send_now){
1408         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1409     }
1410 }
1411 
1412 static void rfcomm_channel_accept_pn(rfcomm_channel_t *channel, rfcomm_channel_event_pn_t *event){
1413     // priority of client request
1414     channel->pn_priority = event->priority;
1415 
1416     // new credits
1417     channel->credits_outgoing = event->credits_outgoing;
1418 
1419     // negotiate max frame size
1420     if (channel->max_frame_size > channel->multiplexer->max_frame_size) {
1421         channel->max_frame_size = channel->multiplexer->max_frame_size;
1422     }
1423     if (channel->max_frame_size > event->max_frame_size) {
1424         channel->max_frame_size = event->max_frame_size;
1425     }
1426 
1427 }
1428 
1429 static void rfcomm_channel_finalize(rfcomm_channel_t *channel){
1430 
1431     rfcomm_multiplexer_t *multiplexer = channel->multiplexer;
1432 
1433     // remove from list
1434     btstack_linked_list_remove( &rfcomm_channels, (btstack_linked_item_t *) channel);
1435 
1436     // free channel
1437     btstack_memory_rfcomm_channel_free(channel);
1438 
1439     // update multiplexer timeout after channel was removed from list
1440     rfcomm_multiplexer_prepare_idle_timer(multiplexer);
1441 }
1442 
1443 static void rfcomm_channel_state_machine_with_dlci(rfcomm_multiplexer_t * multiplexer, uint8_t dlci, const rfcomm_channel_event_t *event){
1444 
1445     // TODO: if client max frame size is smaller than RFCOMM_DEFAULT_SIZE, send PN
1446 
1447 
1448     // lookup existing channel
1449     rfcomm_channel_t * channel = rfcomm_channel_for_multiplexer_and_dlci(multiplexer, dlci);
1450 
1451     // log_info("rfcomm_channel_state_machine_with_dlci lookup dlci #%u = 0x%08x - event %u", dlci, (int) channel, event->type);
1452 
1453     if (channel) {
1454         int rfcomm_channel_valid = 1;
1455         rfcomm_channel_state_machine_with_channel(channel, event, &rfcomm_channel_valid);
1456         if (rfcomm_channel_valid && rfcomm_channel_ready_to_send(channel)){
1457             l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1458         }
1459         return;
1460     }
1461 
1462     // service registered?
1463     rfcomm_service_t * service = rfcomm_service_for_channel(dlci >> 1);
1464     // log_info("rfcomm_channel_state_machine_with_dlci service dlci #%u = 0x%08x", dlci, (int) service);
1465     if (!service) {
1466         // discard request by sending disconnected mode
1467         multiplexer->send_dm_for_dlci = dlci;
1468         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1469         return;
1470     }
1471 
1472     // create channel for some events
1473     switch (event->type) {
1474         case CH_EVT_RCVD_SABM:
1475         case CH_EVT_RCVD_PN:
1476         case CH_EVT_RCVD_RPN_REQ:
1477         case CH_EVT_RCVD_RPN_CMD:
1478             // setup incoming channel
1479             channel = rfcomm_channel_create(multiplexer, service, dlci >> 1);
1480             if (!channel){
1481                 // discard request by sending disconnected mode
1482                 multiplexer->send_dm_for_dlci = dlci;
1483                 l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1484             }
1485             break;
1486         default:
1487             break;
1488     }
1489 
1490     if (!channel) {
1491         // discard request by sending disconnected mode
1492         multiplexer->send_dm_for_dlci = dlci;
1493         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1494         return;
1495     }
1496 
1497     int rfcomm_channel_valid = 1;
1498     rfcomm_channel_state_machine_with_channel(channel, event, &rfcomm_channel_valid);
1499     if (rfcomm_channel_valid && rfcomm_channel_ready_to_send(channel)){
1500         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1501     }
1502 }
1503 
1504 static void rfcomm_channel_packet_handler(rfcomm_multiplexer_t * multiplexer,  uint8_t *packet, uint16_t size){
1505 
1506     UNUSED(size);   // ok: fixed format messages
1507 
1508     // rfcomm: (0) addr [76543 server channel] [2 direction: initiator uses 1] [1 C/R: CMD by initiator = 1] [0 EA=1]
1509     const uint8_t frame_dlci = packet[0] >> 2;
1510     uint8_t message_dlci; // used by commands in UIH(_PF) packets
1511 	uint8_t message_len;  //   "
1512 
1513     // rfcomm: (1) command/control
1514     // -- credits_offset = 1 if command == BT_RFCOMM_UIH_PF
1515     const uint8_t credit_offset = ((packet[1] & BT_RFCOMM_UIH_PF) == BT_RFCOMM_UIH_PF) ? 1 : 0;   // credits for uih_pf frames
1516     // rfcomm: (2) length. if bit 0 is cleared, 2 byte length is used. (little endian)
1517     const uint8_t length_offset = (packet[2] & 1) ^ 1;  // to be used for pos >= 3
1518     // rfcomm: (3+length_offset) credits if credits_offset == 1
1519     // rfcomm: (3+length_offest+credits_offset)
1520     const uint8_t payload_offset = 3 + length_offset + credit_offset;
1521 
1522     rfcomm_channel_event_t event;
1523     rfcomm_channel_event_pn_t event_pn;
1524     rfcomm_channel_event_rpn_t event_rpn;
1525     rfcomm_channel_event_msc_t event_msc;
1526 
1527     // switch by rfcomm message type
1528     switch(packet[1]) {
1529 
1530         case BT_RFCOMM_SABM:
1531             event.type = CH_EVT_RCVD_SABM;
1532             log_info("Received SABM #%u", frame_dlci);
1533             rfcomm_channel_state_machine_with_dlci(multiplexer, frame_dlci, &event);
1534             break;
1535 
1536         case BT_RFCOMM_UA:
1537             event.type = CH_EVT_RCVD_UA;
1538             log_info("Received UA #%u",frame_dlci);
1539             rfcomm_channel_state_machine_with_dlci(multiplexer, frame_dlci, &event);
1540             break;
1541 
1542         case BT_RFCOMM_DISC:
1543             event.type = CH_EVT_RCVD_DISC;
1544             rfcomm_channel_state_machine_with_dlci(multiplexer, frame_dlci, &event);
1545             break;
1546 
1547         case BT_RFCOMM_DM:
1548         case BT_RFCOMM_DM_PF:
1549             event.type = CH_EVT_RCVD_DM;
1550             rfcomm_channel_state_machine_with_dlci(multiplexer, frame_dlci, &event);
1551             break;
1552 
1553         case BT_RFCOMM_UIH_PF:
1554         case BT_RFCOMM_UIH:
1555 
1556             message_len  = packet[payload_offset+1] >> 1;
1557 
1558             switch (packet[payload_offset]) {
1559                 case BT_RFCOMM_PN_CMD:
1560                     message_dlci = packet[payload_offset+2];
1561                     event_pn.super.type = CH_EVT_RCVD_PN;
1562                     event_pn.priority = packet[payload_offset+4];
1563                     event_pn.max_frame_size = little_endian_read_16(packet, payload_offset+6);
1564                     event_pn.credits_outgoing = packet[payload_offset+9];
1565                     log_info("Received UIH Parameter Negotiation Command for #%u, credits %u",
1566                         message_dlci, event_pn.credits_outgoing);
1567                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_pn);
1568                     break;
1569 
1570                 case BT_RFCOMM_PN_RSP:
1571                     message_dlci = packet[payload_offset+2];
1572                     event_pn.super.type = CH_EVT_RCVD_PN_RSP;
1573                     event_pn.priority = packet[payload_offset+4];
1574                     event_pn.max_frame_size = little_endian_read_16(packet, payload_offset+6);
1575                     event_pn.credits_outgoing = packet[payload_offset+9];
1576                     log_info("Received UIH Parameter Negotiation Response max frame %u, credits %u",
1577                             event_pn.max_frame_size, event_pn.credits_outgoing);
1578                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_pn);
1579                     break;
1580 
1581                 case BT_RFCOMM_MSC_CMD:
1582                     message_dlci = packet[payload_offset+2] >> 2;
1583                     event_msc.super.type = CH_EVT_RCVD_MSC_CMD;
1584                     event_msc.modem_status = packet[payload_offset+3];
1585                     log_info("Received MSC CMD for #%u, ", message_dlci);
1586                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_msc);
1587                     break;
1588 
1589                 case BT_RFCOMM_MSC_RSP:
1590                     message_dlci = packet[payload_offset+2] >> 2;
1591                     event.type = CH_EVT_RCVD_MSC_RSP;
1592                     log_info("Received MSC RSP for #%u", message_dlci);
1593                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, &event);
1594                     break;
1595 
1596                 case BT_RFCOMM_RPN_CMD:
1597                     message_dlci = packet[payload_offset+2] >> 2;
1598                     switch (message_len){
1599                         case 1:
1600                             log_info("Received Remote Port Negotiation Request for #%u", message_dlci);
1601                             event.type = CH_EVT_RCVD_RPN_REQ;
1602                             rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, &event);
1603                             break;
1604                         case 8:
1605                             log_info("Received Remote Port Negotiation Update for #%u", message_dlci);
1606                             event_rpn.super.type = CH_EVT_RCVD_RPN_CMD;
1607                             event_rpn.data = *(rfcomm_rpn_data_t*) &packet[payload_offset+3];
1608                             rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_rpn);
1609                             break;
1610                         default:
1611                             break;
1612                     }
1613                     break;
1614 
1615                 case BT_RFCOMM_RPN_RSP:
1616                     log_info("Received RPN response");
1617                     break;
1618 
1619                 case BT_RFCOMM_RLS_CMD: {
1620                     log_info("Received RLS command");
1621                     message_dlci = packet[payload_offset+2] >> 2;
1622                     rfcomm_channel_event_rls_t event_rls;
1623                     event_rls.super.type = CH_EVT_RCVD_RLS_CMD;
1624                     event_rls.line_status = packet[payload_offset+3];
1625                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_rls);
1626                     break;
1627                 }
1628 
1629                 case BT_RFCOMM_RLS_RSP:
1630                     log_info("Received RLS response");
1631                     break;
1632 
1633                 // Following commands are handled by rfcomm_multiplexer_l2cap_packet_handler
1634                 // case BT_RFCOMM_TEST_CMD:
1635                 // case BT_RFCOMM_FCOFF_CMD:
1636                 // case BT_RFCOMM_FCON_CMD:
1637                 // everything else is an not supported command
1638                 default: {
1639                     log_error("Received unknown UIH command packet - 0x%02x", packet[payload_offset]);
1640                     multiplexer->nsc_command = packet[payload_offset];
1641                     break;
1642                 }
1643             }
1644             break;
1645 
1646         default:
1647             log_error("Received unknown RFCOMM message type %x", packet[1]);
1648             break;
1649     }
1650 
1651     // trigger next action - example W4_PN_RSP: transition to SEND_SABM which only depends on "can send"
1652     if (rfcomm_multiplexer_ready_to_send(multiplexer)){
1653         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1654     }
1655 }
1656 
1657 static void rfcomm_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
1658 
1659     if (packet_type == HCI_EVENT_PACKET){
1660         rfcomm_hci_event_handler(packet, size);
1661         return;
1662     }
1663 
1664     // we only handle l2cap packets for:
1665     if (packet_type != L2CAP_DATA_PACKET) return;
1666 
1667     //  - multiplexer itself
1668     int handled = rfcomm_multiplexer_l2cap_packet_handler(channel, packet, size);
1669 
1670     if (handled) return;
1671 
1672     // - channel over open mutliplexer
1673     rfcomm_multiplexer_t * multiplexer = rfcomm_multiplexer_for_l2cap_cid(channel);
1674     if (!multiplexer || multiplexer->state != RFCOMM_MULTIPLEXER_OPEN) return;
1675 
1676     // channel data ?
1677     // rfcomm: (0) addr [76543 server channel] [2 direction: initiator uses 1] [1 C/R: CMD by initiator = 1] [0 EA=1]
1678     const uint8_t frame_dlci = packet[0] >> 2;
1679 
1680     if (frame_dlci && (packet[1] == BT_RFCOMM_UIH || packet[1] == BT_RFCOMM_UIH_PF)) {
1681         rfcomm_channel_packet_handler_uih(multiplexer, packet, size);
1682         return;
1683     }
1684 
1685     rfcomm_channel_packet_handler(multiplexer, packet, size);
1686 }
1687 
1688 static int rfcomm_channel_ready_for_open(rfcomm_channel_t *channel){
1689     // note: exchanging MSC isn't neccessary to consider channel open
1690     // note: having outgoing credits is also not necessary to consider channel open
1691     // log_info("rfcomm_channel_ready_for_open state %u, flags needed %04x, current %04x, rf credits %u, l2cap credits %u ", channel->state, RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_RSP|RFCOMM_CHANNEL_STATE_VAR_SENT_MSC_RSP|RFCOMM_CHANNEL_STATE_VAR_SENT_CREDITS, channel->state_var, channel->credits_outgoing, channel->multiplexer->l2cap_credits);
1692     // if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SENT_MSC_RSP) == 0) return 0;
1693     // if (channel->credits_outgoing == 0) return 0;
1694     log_info("rfcomm_channel_ready_for_open state %u, flags needed %04x, current %04x, rf credits %u",
1695          channel->state, RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_RSP, channel->state_var, channel->credits_outgoing);
1696     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_RSP) == 0) return 0;
1697     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SENT_CREDITS) == 0) return 0;
1698 
1699     return 1;
1700 }
1701 
1702 static int rfcomm_channel_ready_for_incoming_dlc_setup(rfcomm_channel_t * channel){
1703     log_info("rfcomm_channel_ready_for_incoming_dlc_setup state var %04x", channel->state_var);
1704     // Client accept and SABM/UA is required, PN RSP is needed if PN was received
1705     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_CLIENT_ACCEPTED) == 0) return 0;
1706     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_SABM      ) == 0) return 0;
1707     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_UA        ) != 0) return 0;
1708     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP    ) != 0) return 0;
1709     return 1;
1710 }
1711 
1712 inline static void rfcomm_channel_state_add(rfcomm_channel_t *channel, RFCOMM_CHANNEL_STATE_VAR event){
1713     channel->state_var = (RFCOMM_CHANNEL_STATE_VAR) (channel->state_var | event);
1714 }
1715 inline static void rfcomm_channel_state_remove(rfcomm_channel_t *channel, RFCOMM_CHANNEL_STATE_VAR event){
1716     channel->state_var = (RFCOMM_CHANNEL_STATE_VAR) (channel->state_var & ~event);
1717 }
1718 
1719 static int rfcomm_channel_ready_to_send(rfcomm_channel_t * channel){
1720     switch (channel->state){
1721         case RFCOMM_CHANNEL_SEND_UIH_PN:
1722             log_debug("ch-ready: state %u", channel->state);
1723             return 1;
1724         case RFCOMM_CHANNEL_SEND_SABM_W4_UA:
1725             log_debug("ch-ready: state %u", channel->state);
1726             return 1;
1727         case RFCOMM_CHANNEL_SEND_UA_AFTER_DISC:
1728             log_debug("ch-ready: state %u", channel->state);
1729             return 1;
1730         case RFCOMM_CHANNEL_SEND_DISC:
1731             log_debug("ch-ready: state %u", channel->state);
1732             return 1;
1733         case RFCOMM_CHANNEL_SEND_DM:
1734             log_debug("ch-ready: state %u", channel->state);
1735             return 1;
1736         case RFCOMM_CHANNEL_OPEN:
1737             if (channel->new_credits_incoming) {
1738                 log_debug("ch-ready: channel open & new_credits_incoming") ;
1739                 return 1;
1740             }
1741             break;
1742         case RFCOMM_CHANNEL_DLC_SETUP:
1743             if (channel->state_var & (
1744                 RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD  |
1745                 RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS
1746              )) {
1747                 log_debug("ch-ready: channel dlc setup & send msc cmd or send credits") ;
1748                 return 1;
1749             }
1750             break;
1751 
1752         default:
1753             break;
1754     }
1755 
1756     if (channel->state_var & (
1757         RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP   |
1758         RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_INFO |
1759         RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RSP  |
1760         RFCOMM_CHANNEL_STATE_VAR_SEND_UA       |
1761         RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP
1762                              )){
1763         log_debug("ch-ready: state %x, state var %x", channel->state, channel->state_var);
1764         return 1;
1765     }
1766 
1767     if (channel->rls_line_status != RFCOMM_RLS_STATUS_INVALID) {
1768         log_debug("ch-ready: rls_line_status");
1769         return 1;
1770     }
1771 
1772     return 0;
1773 }
1774 
1775 
1776 static void rfcomm_channel_state_machine_with_channel(rfcomm_channel_t *channel, const rfcomm_channel_event_t *event, int * out_channel_valid){
1777 
1778     // log_info("rfcomm_channel_state_machine_with_channel: state %u, state_var %04x, event %u", channel->state, channel->state_var ,event->type);
1779 
1780     // channel != NULL -> channel valid
1781     *out_channel_valid = 1;
1782 
1783     rfcomm_multiplexer_t *multiplexer = channel->multiplexer;
1784 
1785     // TODO: integrate in common switch
1786     if (event->type == CH_EVT_RCVD_DISC){
1787         rfcomm_emit_channel_closed(channel);
1788         channel->state = RFCOMM_CHANNEL_SEND_UA_AFTER_DISC;
1789         return;
1790     }
1791 
1792     // TODO: integrate in common switch
1793     if (event->type == CH_EVT_RCVD_DM){
1794         log_info("Received DM message for #%u", channel->dlci);
1795         log_info("-> Closing channel locally for #%u", channel->dlci);
1796         rfcomm_channel_emit_final_event(channel, ERROR_CODE_CONNECTION_REJECTED_DUE_TO_LIMITED_RESOURCES);
1797         rfcomm_channel_finalize(channel);
1798         *out_channel_valid = 0;
1799         return;
1800     }
1801 
1802     // remote port negotiation command - just accept everything for now
1803     //
1804     // "The RPN command can be used before a new DLC is opened and should be used whenever the port settings change."
1805     // "The RPN command is specified as optional in TS 07.10, but it is mandatory to recognize and respond to it in RFCOMM.
1806     //   (Although the handling of individual settings are implementation-dependent.)"
1807     //
1808 
1809     // TODO: integrate in common switch
1810     if (event->type == CH_EVT_RCVD_RPN_CMD){
1811         // control port parameters
1812         rfcomm_channel_event_rpn_t *event_rpn = (rfcomm_channel_event_rpn_t*) event;
1813         rfcomm_rpn_data_update(&channel->rpn_data, &event_rpn->data);
1814         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RSP);
1815         // notify client about new settings
1816         rfcomm_emit_port_configuration(channel);
1817         return;
1818     }
1819 
1820     // TODO: integrate in common switch
1821     if (event->type == CH_EVT_RCVD_RPN_REQ){
1822         // no values got accepted (no values have beens sent)
1823         channel->rpn_data.parameter_mask_0 = 0x00;
1824         channel->rpn_data.parameter_mask_1 = 0x00;
1825         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RSP);
1826         return;
1827     }
1828 
1829     if (event->type == CH_EVT_RCVD_RLS_CMD){
1830         rfcomm_channel_event_rls_t * event_rls = (rfcomm_channel_event_rls_t*) event;
1831         channel->rls_line_status = event_rls->line_status & 0x0f;
1832         log_info("CH_EVT_RCVD_RLS_CMD setting line status to 0x%0x", channel->rls_line_status);
1833         rfcomm_emit_remote_line_status(channel, event_rls->line_status);
1834         return;
1835     }
1836 
1837     // TODO: integrate in common switch
1838     if (event->type == CH_EVT_READY_TO_SEND){
1839         if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RSP){
1840             log_info("Sending Remote Port Negotiation RSP for #%u", channel->dlci);
1841             rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RSP);
1842             rfcomm_send_uih_rpn_rsp(multiplexer, channel->dlci, &channel->rpn_data);
1843             return;
1844         }
1845         if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP){
1846             log_info("Sending MSC RSP for #%u", channel->dlci);
1847             rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP);
1848             rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SENT_MSC_RSP);
1849             rfcomm_send_uih_msc_rsp(multiplexer, channel->dlci, 0x8d);  // ea=1,fc=0,rtc=1,rtr=1,ic=0,dv=1
1850             return;
1851         }
1852         if (channel->rls_line_status != RFCOMM_RLS_STATUS_INVALID){
1853             log_info("Sending RLS RSP 0x%0x", channel->rls_line_status);
1854             uint8_t line_status = channel->rls_line_status;
1855             channel->rls_line_status = RFCOMM_RLS_STATUS_INVALID;
1856             rfcomm_send_uih_rls_rsp(multiplexer, channel->dlci, line_status);
1857             return;
1858         }
1859     }
1860 
1861     // emit MSC status to app
1862     if (event->type == CH_EVT_RCVD_MSC_CMD){
1863         // notify client about new settings
1864         rfcomm_channel_event_msc_t *event_msc = (rfcomm_channel_event_msc_t*) event;
1865         uint8_t modem_status_event[2+1];
1866         modem_status_event[0] = RFCOMM_EVENT_REMOTE_MODEM_STATUS;
1867         modem_status_event[1] = 1;
1868         modem_status_event[2] = event_msc->modem_status;
1869         (channel->packet_handler)(HCI_EVENT_PACKET, channel->rfcomm_cid, (uint8_t*)&modem_status_event, sizeof(modem_status_event));
1870         // no return, MSC_CMD will be handled by state machine below
1871     }
1872 
1873     rfcomm_channel_event_pn_t * event_pn = (rfcomm_channel_event_pn_t*) event;
1874 
1875     switch (channel->state) {
1876         case RFCOMM_CHANNEL_CLOSED:
1877             switch (event->type){
1878                 case CH_EVT_RCVD_SABM:
1879                     log_info("-> Inform app");
1880                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_SABM);
1881                     channel->state = RFCOMM_CHANNEL_INCOMING_SETUP;
1882                     rfcomm_emit_connection_request(channel);
1883                     break;
1884                 case CH_EVT_RCVD_PN:
1885                     rfcomm_channel_accept_pn(channel, event_pn);
1886                     log_info("-> Inform app");
1887                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_PN);
1888                     channel->state = RFCOMM_CHANNEL_INCOMING_SETUP;
1889                     rfcomm_emit_connection_request(channel);
1890                     break;
1891                 default:
1892                     break;
1893             }
1894             break;
1895 
1896         case RFCOMM_CHANNEL_INCOMING_SETUP:
1897             switch (event->type){
1898                 case CH_EVT_RCVD_SABM:
1899                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_SABM);
1900                     if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_CLIENT_ACCEPTED) {
1901                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_UA);
1902                     }
1903                     break;
1904                 case CH_EVT_RCVD_PN:
1905                     rfcomm_channel_accept_pn(channel, event_pn);
1906                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_PN);
1907                     if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_CLIENT_ACCEPTED) {
1908                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP);
1909                     }
1910                     break;
1911                 case CH_EVT_READY_TO_SEND:
1912                     // if / else if is used to check for state transition after sending
1913                     if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP){
1914                         log_info("Sending UIH Parameter Negotiation Respond for #%u", channel->dlci);
1915                         rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP);
1916                         rfcomm_send_uih_pn_response(multiplexer, channel->dlci, channel->pn_priority, channel->max_frame_size);
1917                     } else if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_UA){
1918                         log_info("Sending UA #%u", channel->dlci);
1919                         rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_UA);
1920                         rfcomm_send_ua(multiplexer, channel->dlci);
1921                     }
1922                     if (rfcomm_channel_ready_for_incoming_dlc_setup(channel)){
1923                         log_info("Incomping setup done, requesting send MSC CMD and send Credits");
1924                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD);
1925                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS);
1926                         channel->state = RFCOMM_CHANNEL_DLC_SETUP;
1927                      }
1928                     break;
1929                 default:
1930                     break;
1931             }
1932             break;
1933 
1934         case RFCOMM_CHANNEL_W4_MULTIPLEXER:
1935             switch (event->type) {
1936                 case CH_EVT_MULTIPLEXER_READY:
1937                     log_info("Muliplexer opened, sending UIH PN next");
1938                     channel->state = RFCOMM_CHANNEL_SEND_UIH_PN;
1939                     break;
1940                 default:
1941                     break;
1942             }
1943             break;
1944 
1945         case RFCOMM_CHANNEL_SEND_UIH_PN:
1946             switch (event->type) {
1947                 case CH_EVT_READY_TO_SEND:
1948                     log_info("Sending UIH Parameter Negotiation Command for #%u (channel 0x%p)", channel->dlci, channel );
1949                     channel->state = RFCOMM_CHANNEL_W4_PN_RSP;
1950                     rfcomm_send_uih_pn_command(multiplexer, channel->dlci, channel->max_frame_size);
1951                     break;
1952                 default:
1953                     break;
1954             }
1955             break;
1956 
1957         case RFCOMM_CHANNEL_W4_PN_RSP:
1958             switch (event->type){
1959                 case CH_EVT_RCVD_PN_RSP:
1960                     // update max frame size
1961                     if (channel->max_frame_size > event_pn->max_frame_size) {
1962                         channel->max_frame_size = event_pn->max_frame_size;
1963                     }
1964                     // new credits
1965                     channel->credits_outgoing = event_pn->credits_outgoing;
1966                     channel->state = RFCOMM_CHANNEL_SEND_SABM_W4_UA;
1967                     break;
1968                 default:
1969                     break;
1970             }
1971             break;
1972 
1973         case RFCOMM_CHANNEL_SEND_SABM_W4_UA:
1974             switch (event->type) {
1975                 case CH_EVT_READY_TO_SEND:
1976                     log_info("Sending SABM #%u", channel->dlci);
1977                     channel->state = RFCOMM_CHANNEL_W4_UA;
1978                     rfcomm_send_sabm(multiplexer, channel->dlci);
1979                     break;
1980                 default:
1981                     break;
1982             }
1983             break;
1984 
1985         case RFCOMM_CHANNEL_W4_UA:
1986             switch (event->type){
1987                 case CH_EVT_RCVD_UA:
1988                     channel->state = RFCOMM_CHANNEL_DLC_SETUP;
1989                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD);
1990                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS);
1991                     break;
1992                 default:
1993                     break;
1994             }
1995             break;
1996 
1997         case RFCOMM_CHANNEL_DLC_SETUP:
1998             switch (event->type){
1999                 case CH_EVT_RCVD_MSC_CMD:
2000                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_CMD);
2001                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP);
2002                     break;
2003                 case CH_EVT_RCVD_MSC_RSP:
2004                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_RSP);
2005                     break;
2006 
2007                 case CH_EVT_READY_TO_SEND:
2008                     if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD){
2009                         log_info("Sending MSC CMD for #%u", channel->dlci);
2010                         rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD);
2011                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SENT_MSC_CMD);
2012                         rfcomm_send_uih_msc_cmd(multiplexer, channel->dlci , 0x8d);  // ea=1,fc=0,rtc=1,rtr=1,ic=0,dv=1
2013                         break;
2014                     }
2015                     if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS){
2016                         log_info("Providing credits for #%u", channel->dlci);
2017                         rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS);
2018                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SENT_CREDITS);
2019 
2020                         if (channel->new_credits_incoming) {
2021                             uint8_t new_credits = channel->new_credits_incoming;
2022                             channel->new_credits_incoming = 0;
2023                             rfcomm_channel_send_credits(channel, new_credits);
2024                         }
2025                         break;
2026 
2027                     }
2028                     break;
2029                 default:
2030                     break;
2031             }
2032             // finally done?
2033             if (rfcomm_channel_ready_for_open(channel)){
2034                 channel->state = RFCOMM_CHANNEL_OPEN;
2035                 rfcomm_channel_opened(channel);
2036             }
2037             break;
2038 
2039         case RFCOMM_CHANNEL_OPEN:
2040             switch (event->type){
2041                 case CH_EVT_RCVD_MSC_CMD:
2042                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP);
2043                     break;
2044                 case CH_EVT_READY_TO_SEND:
2045                     if (channel->new_credits_incoming) {
2046                         uint8_t new_credits = channel->new_credits_incoming;
2047                         channel->new_credits_incoming = 0;
2048                         rfcomm_channel_send_credits(channel, new_credits);
2049                         break;
2050                     }
2051                     break;
2052                 case CH_EVT_RCVD_CREDITS:
2053                     rfcomm_notify_channel_can_send();
2054                     break;
2055                 default:
2056                     break;
2057             }
2058             break;
2059 
2060         case RFCOMM_CHANNEL_SEND_DM:
2061             switch (event->type) {
2062                 case CH_EVT_READY_TO_SEND:
2063                     log_info("Sending DM_PF for #%u", channel->dlci);
2064                     // don't emit channel closed - channel was never open
2065                     channel->state = RFCOMM_CHANNEL_CLOSED;
2066                     rfcomm_send_dm_pf(multiplexer, channel->dlci);
2067                     rfcomm_channel_finalize(channel);
2068                     *out_channel_valid = 0;
2069                     break;
2070                 default:
2071                     break;
2072             }
2073             break;
2074 
2075         case RFCOMM_CHANNEL_SEND_DISC:
2076             switch (event->type) {
2077                 case CH_EVT_READY_TO_SEND:
2078                     channel->state = RFCOMM_CHANNEL_W4_UA_AFTER_DISC;
2079                     rfcomm_send_disc(multiplexer, channel->dlci);
2080                     break;
2081                 default:
2082                     break;
2083             }
2084             break;
2085 
2086         case RFCOMM_CHANNEL_W4_UA_AFTER_DISC:
2087             switch (event->type){
2088                 case CH_EVT_RCVD_UA:
2089                     channel->state = RFCOMM_CHANNEL_CLOSED;
2090                     rfcomm_emit_channel_closed(channel);
2091                     rfcomm_channel_finalize(channel);
2092                     *out_channel_valid = 0;
2093                     break;
2094                 default:
2095                     break;
2096             }
2097             break;
2098 
2099         case RFCOMM_CHANNEL_SEND_UA_AFTER_DISC:
2100             switch (event->type) {
2101                 case CH_EVT_READY_TO_SEND:
2102                     log_info("Sending UA after DISC for #%u", channel->dlci);
2103                     channel->state = RFCOMM_CHANNEL_CLOSED;
2104                     rfcomm_send_ua(multiplexer, channel->dlci);
2105                     rfcomm_channel_finalize(channel);
2106                     *out_channel_valid = 0;
2107                     break;
2108                 default:
2109                     break;
2110             }
2111             break;
2112 
2113         default:
2114             break;
2115     }
2116 }
2117 
2118 // MARK: RFCOMM BTstack API
2119 
2120 void rfcomm_init(void){
2121     rfcomm_client_cid_generator = 0;
2122     rfcomm_multiplexers = NULL;
2123     rfcomm_services     = NULL;
2124     rfcomm_channels     = NULL;
2125     rfcomm_security_level = LEVEL_2;
2126 }
2127 
2128 void rfcomm_set_required_security_level(gap_security_level_t security_level){
2129     rfcomm_security_level = security_level;
2130 }
2131 
2132 int rfcomm_can_send_packet_now(uint16_t rfcomm_cid){
2133     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2134     if (!channel){
2135         log_error("rfcomm_send cid 0x%02x doesn't exist!", rfcomm_cid);
2136         return 0;
2137     }
2138     return rfcomm_channel_can_send(channel);
2139 }
2140 
2141 void rfcomm_request_can_send_now_event(uint16_t rfcomm_cid){
2142     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2143     if (!channel){
2144         log_error("rfcomm_send cid 0x%02x doesn't exist!", rfcomm_cid);
2145         return;
2146     }
2147     channel->waiting_for_can_send_now = 1;
2148     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2149 }
2150 
2151 static int rfcomm_assert_send_valid(rfcomm_channel_t * channel , uint16_t len){
2152     if (len > channel->max_frame_size){
2153         log_error("rfcomm_send cid 0x%02x, rfcomm data lenght exceeds MTU!", channel->rfcomm_cid);
2154         return RFCOMM_DATA_LEN_EXCEEDS_MTU;
2155     }
2156 
2157 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2158     if (len > rfcomm_max_frame_size_for_l2cap_mtu(sizeof(outgoing_buffer))){
2159         log_error("rfcomm_send cid 0x%02x, length exceeds outgoing rfcomm_out_buffer", channel->rfcomm_cid);
2160         return RFCOMM_DATA_LEN_EXCEEDS_MTU;
2161     }
2162 #endif
2163 
2164     if (!channel->credits_outgoing){
2165         log_info("rfcomm_send cid 0x%02x, no rfcomm outgoing credits!", channel->rfcomm_cid);
2166         return RFCOMM_NO_OUTGOING_CREDITS;
2167     }
2168 
2169     if ((channel->multiplexer->fcon & 1) == 0){
2170         log_info("rfcomm_send cid 0x%02x, aggregate flow off!", channel->rfcomm_cid);
2171         return RFCOMM_AGGREGATE_FLOW_OFF;
2172     }
2173     return 0;
2174 }
2175 
2176 uint16_t rfcomm_get_max_frame_size(uint16_t rfcomm_cid){
2177     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2178     if (!channel){
2179         log_error("rfcomm_get_max_frame_size cid 0x%02x doesn't exist!", rfcomm_cid);
2180         return 0;
2181     }
2182     return channel->max_frame_size;
2183 }
2184 
2185 // pre: rfcomm_can_send_packet_now(rfcomm_cid) == true
2186 int rfcomm_reserve_packet_buffer(void){
2187 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2188     log_error("rfcomm_reserve_packet_buffer should not get called with ERTM");
2189     return 0;
2190 #else
2191     return l2cap_reserve_packet_buffer();
2192 #endif
2193 }
2194 
2195 void rfcomm_release_packet_buffer(void){
2196 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2197     log_error("rfcomm_release_packet_buffer should not get called with ERTM");
2198 #else
2199     l2cap_release_packet_buffer();
2200 #endif
2201 }
2202 
2203 uint8_t * rfcomm_get_outgoing_buffer(void){
2204 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2205     uint8_t * rfcomm_out_buffer = outgoing_buffer;
2206 #else
2207     uint8_t * rfcomm_out_buffer = l2cap_get_outgoing_buffer();
2208 #endif
2209     // address + control + length (16) + no credit field
2210     return &rfcomm_out_buffer[4];
2211 }
2212 
2213 int rfcomm_send_prepared(uint16_t rfcomm_cid, uint16_t len){
2214     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2215     if (!channel){
2216         log_error("rfcomm_send_prepared cid 0x%02x doesn't exist!", rfcomm_cid);
2217         return 0;
2218     }
2219 
2220     int err = rfcomm_assert_send_valid(channel, len);
2221     if (err) return err;
2222 
2223 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2224     if (!l2cap_can_send_packet_now(channel->multiplexer->l2cap_cid)){
2225         log_error("rfcomm_send_prepared: l2cap cannot send now");
2226         return BTSTACK_ACL_BUFFERS_FULL;
2227     }
2228 #else
2229     if (!l2cap_can_send_prepared_packet_now(channel->multiplexer->l2cap_cid)){
2230         log_error("rfcomm_send_prepared: l2cap cannot send now");
2231         return BTSTACK_ACL_BUFFERS_FULL;
2232     }
2233 #endif
2234 
2235     // send might cause l2cap to emit new credits, update counters first
2236     if (len){
2237         channel->credits_outgoing--;
2238     } else {
2239         log_info("sending empty RFCOMM packet for cid %02x", rfcomm_cid);
2240     }
2241 
2242     int result = rfcomm_send_uih_prepared(channel->multiplexer, channel->dlci, len);
2243 
2244     if (result != 0) {
2245         if (len) {
2246             channel->credits_outgoing++;
2247         }
2248         log_error("rfcomm_send_prepared: error %d", result);
2249         return result;
2250     }
2251 
2252     return result;
2253 }
2254 
2255 int rfcomm_send(uint16_t rfcomm_cid, uint8_t *data, uint16_t len){
2256     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2257     if (!channel){
2258         log_error("cid 0x%02x doesn't exist!", rfcomm_cid);
2259         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
2260     }
2261 
2262     int err = rfcomm_assert_send_valid(channel, len);
2263     if (err) return err;
2264     if (!l2cap_can_send_packet_now(channel->multiplexer->l2cap_cid)){
2265         log_error("rfcomm_send_internal: l2cap cannot send now");
2266         return BTSTACK_ACL_BUFFERS_FULL;
2267     }
2268 
2269 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2270 #else
2271     rfcomm_reserve_packet_buffer();
2272 #endif
2273     uint8_t * rfcomm_payload = rfcomm_get_outgoing_buffer();
2274 
2275     memcpy(rfcomm_payload, data, len);
2276     err = rfcomm_send_prepared(rfcomm_cid, len);
2277 
2278 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2279 #else
2280     if (err){
2281         rfcomm_release_packet_buffer();
2282     }
2283 #endif
2284 
2285     return err;
2286 }
2287 
2288 // Sends Local Lnie Status, see LINE_STATUS_..
2289 int rfcomm_send_local_line_status(uint16_t rfcomm_cid, uint8_t line_status){
2290     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2291     if (!channel){
2292         log_error("rfcomm_send_local_line_status cid 0x%02x doesn't exist!", rfcomm_cid);
2293         return 0;
2294     }
2295     return rfcomm_send_uih_rls_cmd(channel->multiplexer, channel->dlci, line_status);
2296 }
2297 
2298 // Sned local modem status. see MODEM_STAUS_..
2299 int rfcomm_send_modem_status(uint16_t rfcomm_cid, uint8_t modem_status){
2300     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2301     if (!channel){
2302         log_error("rfcomm_send_modem_status cid 0x%02x doesn't exist!", rfcomm_cid);
2303         return 0;
2304     }
2305     return rfcomm_send_uih_msc_cmd(channel->multiplexer, channel->dlci, modem_status);
2306 }
2307 
2308 // Configure remote port
2309 int rfcomm_send_port_configuration(uint16_t rfcomm_cid, rpn_baud_t baud_rate, rpn_data_bits_t data_bits, rpn_stop_bits_t stop_bits, rpn_parity_t parity, rpn_flow_control_t flow_control){
2310     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2311     if (!channel){
2312         log_error("rfcomm_send_port_configuration cid 0x%02x doesn't exist!", rfcomm_cid);
2313         return 0;
2314     }
2315     rfcomm_rpn_data_t rpn_data;
2316     rpn_data.baud_rate = baud_rate;
2317     rpn_data.flags = data_bits | (stop_bits << 2) | (parity << 3);
2318     rpn_data.flow_control = flow_control;
2319     rpn_data.xon = 0;
2320     rpn_data.xoff = 0;
2321     rpn_data.parameter_mask_0 = 0x1f;   // all but xon/xoff
2322     rpn_data.parameter_mask_1 = 0x3f;   // all flow control options
2323     return rfcomm_send_uih_rpn_cmd(channel->multiplexer, channel->dlci, &rpn_data);
2324 }
2325 
2326 // Query remote port
2327 int rfcomm_query_port_configuration(uint16_t rfcomm_cid){
2328     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2329     if (!channel){
2330         log_error("rfcomm_query_port_configuration cid 0x%02x doesn't exist!", rfcomm_cid);
2331         return 0;
2332     }
2333     return rfcomm_send_uih_rpn_req(channel->multiplexer, channel->dlci);
2334 }
2335 
2336 
2337 static uint8_t rfcomm_channel_create_internal(btstack_packet_handler_t packet_handler, bd_addr_t addr, uint8_t server_channel, uint8_t incoming_flow_control, uint8_t initial_credits, uint16_t * out_rfcomm_cid){
2338     log_info("RFCOMM_CREATE_CHANNEL addr %s channel #%u init credits %u",  bd_addr_to_str(addr), server_channel, initial_credits);
2339 
2340     // create new multiplexer if necessary
2341     uint8_t status = 0;
2342     uint8_t dlci = 0;
2343     int new_multiplexer = 0;
2344     rfcomm_channel_t * channel = NULL;
2345     rfcomm_multiplexer_t * multiplexer = rfcomm_multiplexer_for_addr(addr);
2346     if (!multiplexer) {
2347         multiplexer = rfcomm_multiplexer_create_for_addr(addr);
2348         if (!multiplexer){
2349             status = BTSTACK_MEMORY_ALLOC_FAILED;
2350             goto fail;
2351         }
2352         multiplexer->outgoing = 1;
2353         multiplexer->state = RFCOMM_MULTIPLEXER_W4_CONNECT;
2354         new_multiplexer = 1;
2355     }
2356 
2357     // check if channel for this remote service already exists
2358     dlci = (server_channel << 1) | (multiplexer->outgoing ^ 1);
2359     channel = rfcomm_channel_for_multiplexer_and_dlci(multiplexer, dlci);
2360     if (channel){
2361         status = RFCOMM_CHANNEL_ALREADY_REGISTERED;
2362         goto fail;
2363     }
2364 
2365     // prepare channel
2366     channel = rfcomm_channel_create(multiplexer, NULL, server_channel);
2367     if (!channel){
2368         status = BTSTACK_MEMORY_ALLOC_FAILED;
2369         goto fail;
2370     }
2371 
2372     // rfcomm_cid is already assigned by rfcomm_channel_create
2373     channel->incoming_flow_control = incoming_flow_control;
2374     channel->new_credits_incoming  = initial_credits;
2375     channel->packet_handler = packet_handler;
2376 
2377     // return rfcomm_cid
2378     if (out_rfcomm_cid){
2379         *out_rfcomm_cid = channel->rfcomm_cid;
2380     }
2381 
2382     // start multiplexer setup
2383     if (multiplexer->state != RFCOMM_MULTIPLEXER_OPEN) {
2384         channel->state = RFCOMM_CHANNEL_W4_MULTIPLEXER;
2385         uint16_t l2cap_cid = 0;
2386 #ifdef RFCOMM_USE_ERTM
2387         // request
2388         rfcomm_ertm_request_t request;
2389         memset(&request, 0, sizeof(rfcomm_ertm_request_t));
2390         memcpy(request.addr, addr, 6);
2391         request.ertm_id = ++ertm_id;
2392         if (rfcomm_ertm_request_callback){
2393             (*rfcomm_ertm_request_callback)(&request);
2394         }
2395         if (request.ertm_config && request.ertm_buffer && request.ertm_buffer_size){
2396             multiplexer->ertm_id = request.ertm_id;
2397             status = l2cap_create_ertm_channel(rfcomm_packet_handler, addr, BLUETOOTH_PROTOCOL_RFCOMM,
2398                         request.ertm_config, request.ertm_buffer, request.ertm_buffer_size, &l2cap_cid);
2399         }
2400         else
2401 #endif
2402         {
2403             status = l2cap_create_channel(rfcomm_packet_handler, addr, BLUETOOTH_PROTOCOL_RFCOMM, l2cap_max_mtu(), &l2cap_cid);
2404         }
2405         if (status) goto fail;
2406         multiplexer->l2cap_cid = l2cap_cid;
2407         return 0;
2408     }
2409 
2410     channel->state = RFCOMM_CHANNEL_SEND_UIH_PN;
2411 
2412     // start connecting, if multiplexer is already up and running
2413     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
2414     return 0;
2415 
2416 fail:
2417     if (new_multiplexer) btstack_memory_rfcomm_multiplexer_free(multiplexer);
2418     if (channel)         btstack_memory_rfcomm_channel_free(channel);
2419     return status;
2420 }
2421 
2422 uint8_t rfcomm_create_channel_with_initial_credits(btstack_packet_handler_t packet_handler, bd_addr_t addr, uint8_t server_channel, uint8_t initial_credits, uint16_t * out_rfcomm_cid){
2423     return rfcomm_channel_create_internal(packet_handler, addr, server_channel, 1, initial_credits, out_rfcomm_cid);
2424 }
2425 
2426 uint8_t rfcomm_create_channel(btstack_packet_handler_t packet_handler, bd_addr_t addr, uint8_t server_channel, uint16_t * out_rfcomm_cid){
2427     return rfcomm_channel_create_internal(packet_handler, addr, server_channel, 0, RFCOMM_CREDITS, out_rfcomm_cid);
2428 }
2429 
2430 void rfcomm_disconnect(uint16_t rfcomm_cid){
2431     log_info("RFCOMM_DISCONNECT cid 0x%02x", rfcomm_cid);
2432     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2433     if (!channel) return;
2434 
2435     channel->state = RFCOMM_CHANNEL_SEND_DISC;
2436     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2437 }
2438 
2439 static uint8_t rfcomm_register_service_internal(btstack_packet_handler_t packet_handler,
2440     uint8_t channel, uint16_t max_frame_size, uint8_t incoming_flow_control, uint8_t initial_credits){
2441 
2442     log_info("RFCOMM_REGISTER_SERVICE channel #%u mtu %u flow_control %u credits %u",
2443              channel, max_frame_size, incoming_flow_control, initial_credits);
2444 
2445     // check if already registered
2446     rfcomm_service_t * service = rfcomm_service_for_channel(channel);
2447     if (service){
2448         return RFCOMM_CHANNEL_ALREADY_REGISTERED;
2449     }
2450 
2451     // alloc structure
2452     service = btstack_memory_rfcomm_service_get();
2453     if (!service) {
2454         return BTSTACK_MEMORY_ALLOC_FAILED;
2455     }
2456 
2457     // register with l2cap if not registered before, max MTU
2458     if (btstack_linked_list_empty(&rfcomm_services)){
2459         l2cap_register_service(rfcomm_packet_handler, BLUETOOTH_PROTOCOL_RFCOMM, 0xffff, rfcomm_security_level);
2460     }
2461 
2462     // fill in
2463     service->packet_handler = packet_handler;
2464     service->server_channel = channel;
2465     service->max_frame_size = max_frame_size;
2466     service->incoming_flow_control = incoming_flow_control;
2467     service->incoming_initial_credits = initial_credits;
2468 
2469     // add to services list
2470     btstack_linked_list_add(&rfcomm_services, (btstack_linked_item_t *) service);
2471 
2472     return 0;
2473 }
2474 
2475 uint8_t rfcomm_register_service_with_initial_credits(btstack_packet_handler_t packet_handler,
2476     uint8_t channel, uint16_t max_frame_size, uint8_t initial_credits){
2477 
2478     return rfcomm_register_service_internal(packet_handler, channel, max_frame_size, 1, initial_credits);
2479 }
2480 
2481 uint8_t rfcomm_register_service(btstack_packet_handler_t packet_handler, uint8_t channel,
2482     uint16_t max_frame_size){
2483 
2484     return rfcomm_register_service_internal(packet_handler, channel, max_frame_size, 0,RFCOMM_CREDITS);
2485 }
2486 
2487 void rfcomm_unregister_service(uint8_t service_channel){
2488     log_info("RFCOMM_UNREGISTER_SERVICE #%u", service_channel);
2489     rfcomm_service_t *service = rfcomm_service_for_channel(service_channel);
2490     if (!service) return;
2491     btstack_linked_list_remove(&rfcomm_services, (btstack_linked_item_t *) service);
2492     btstack_memory_rfcomm_service_free(service);
2493 
2494     // unregister if no services active
2495     if (btstack_linked_list_empty(&rfcomm_services)){
2496         // bt_send_cmd(&l2cap_unregister_service, BLUETOOTH_PROTOCOL_RFCOMM);
2497         l2cap_unregister_service(BLUETOOTH_PROTOCOL_RFCOMM);
2498     }
2499 }
2500 
2501 void rfcomm_accept_connection(uint16_t rfcomm_cid){
2502     log_info("RFCOMM_ACCEPT_CONNECTION cid 0x%02x", rfcomm_cid);
2503     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2504     if (!channel) return;
2505     switch (channel->state) {
2506         case RFCOMM_CHANNEL_INCOMING_SETUP:
2507             rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_CLIENT_ACCEPTED);
2508             if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_PN){
2509                 rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP);
2510                 l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2511             }
2512             if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_SABM){
2513                 rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_UA);
2514                 l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2515             }
2516             // at least one of { PN RSP, UA } needs to be sent
2517             // state transistion incoming setup -> dlc setup happens in rfcomm_run after these have been sent
2518             break;
2519         default:
2520             break;
2521     }
2522 
2523 }
2524 
2525 void rfcomm_decline_connection(uint16_t rfcomm_cid){
2526     log_info("RFCOMM_DECLINE_CONNECTION cid 0x%02x", rfcomm_cid);
2527     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2528     if (!channel) return;
2529     switch (channel->state) {
2530         case RFCOMM_CHANNEL_INCOMING_SETUP:
2531             channel->state = RFCOMM_CHANNEL_SEND_DM;
2532             l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2533             break;
2534         default:
2535             break;
2536     }
2537 }
2538 
2539 void rfcomm_grant_credits(uint16_t rfcomm_cid, uint8_t credits){
2540     log_info("RFCOMM_GRANT_CREDITS cid 0x%02x credits %u", rfcomm_cid, credits);
2541     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2542     if (!channel) return;
2543     if (!channel->incoming_flow_control) return;
2544     channel->new_credits_incoming += credits;
2545 
2546     // process
2547     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2548 }
2549 
2550 #ifdef RFCOMM_USE_ERTM
2551 void rfcomm_enable_l2cap_ertm(void request_callback(rfcomm_ertm_request_t * request), void released_callback(uint16_t ertm_id)){
2552     rfcomm_ertm_request_callback  = request_callback;
2553     rfcomm_ertm_released_callback = released_callback;
2554 }
2555 #endif
2556