xref: /btstack/src/classic/rfcomm.c (revision c9921182ab4b1f83e3e5c671446dca5ffdf45b90)
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 <string.h> // memcpy
45 #include <stdint.h>
46 
47 #include "bluetooth_sdp.h"
48 #include "btstack_debug.h"
49 #include "btstack_event.h"
50 #include "btstack_memory.h"
51 #include "btstack_util.h"
52 #include "classic/core.h"
53 #include "classic/rfcomm.h"
54 #include "hci.h"
55 #include "hci_cmd.h"
56 #include "hci_dump.h"
57 #include "l2cap.h"
58 
59 // workaround for missing PRIxPTR on mspgcc (16/20-bit MCU)
60 #ifndef PRIxPTR
61 #if defined(__MSP430X__)  &&  defined(__MSP430X_LARGE__)
62 #define PRIxPTR "lx"
63 #else
64 #define PRIxPTR "x"
65 #endif
66 #endif
67 
68 // ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM requires ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE
69 #ifdef ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM
70 #ifdef ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE
71 #define RFCOMM_USE_OUTGOING_BUFFER
72 #define RFCOMM_USE_ERTM
73 #else
74 #error "ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM requires ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE. "
75 #error "Please disable ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM, or, "
76 #error "enable ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE"
77 #endif
78 #endif
79 
80 #define RFCOMM_MULIPLEXER_TIMEOUT_MS 60000
81 
82 #define RFCOMM_CREDITS 10
83 
84 // FCS calc
85 #define BT_RFCOMM_CODE_WORD         0xE0 // pol = x8+x2+x1+1
86 #define BT_RFCOMM_CRC_CHECK_LEN     3
87 #define BT_RFCOMM_UIHCRC_CHECK_LEN  2
88 
89 // Control field values      bit no.       1 2 3 4 PF 6 7 8
90 #define BT_RFCOMM_SABM       0x3F       // 1 1 1 1  1 1 0 0
91 #define BT_RFCOMM_UA         0x73       // 1 1 0 0  1 1 1 0
92 #define BT_RFCOMM_DM         0x0F       // 1 1 1 1  0 0 0 0
93 #define BT_RFCOMM_DM_PF      0x1F       // 1 1 1 1  1 0 0 0
94 #define BT_RFCOMM_DISC       0x53       // 1 1 0 0  1 0 1 0
95 #define BT_RFCOMM_UIH        0xEF       // 1 1 1 1  0 1 1 1
96 #define BT_RFCOMM_UIH_PF     0xFF       // 1 1 1 1  0 1 1 1
97 
98 // Multiplexer message types
99 #define BT_RFCOMM_CLD_CMD    0xC3
100 #define BT_RFCOMM_FCON_CMD   0xA3
101 #define BT_RFCOMM_FCON_RSP   0xA1
102 #define BT_RFCOMM_FCOFF_CMD  0x63
103 #define BT_RFCOMM_FCOFF_RSP  0x61
104 #define BT_RFCOMM_MSC_CMD    0xE3
105 #define BT_RFCOMM_MSC_RSP    0xE1
106 #define BT_RFCOMM_NSC_RSP    0x11
107 #define BT_RFCOMM_PN_CMD     0x83
108 #define BT_RFCOMM_PN_RSP     0x81
109 #define BT_RFCOMM_RLS_CMD    0x53
110 #define BT_RFCOMM_RLS_RSP    0x51
111 #define BT_RFCOMM_RPN_CMD    0x93
112 #define BT_RFCOMM_RPN_RSP    0x91
113 #define BT_RFCOMM_TEST_CMD   0x23
114 #define BT_RFCOMM_TEST_RSP   0x21
115 
116 typedef enum {
117     CH_EVT_RCVD_SABM = 1,
118     CH_EVT_RCVD_UA,
119     CH_EVT_RCVD_PN,
120     CH_EVT_RCVD_PN_RSP,
121     CH_EVT_RCVD_DISC,
122     CH_EVT_RCVD_DM,
123     CH_EVT_RCVD_MSC_CMD,
124     CH_EVT_RCVD_MSC_RSP,
125     CH_EVT_RCVD_NSC_RSP,
126     CH_EVT_RCVD_RLS_CMD,
127     CH_EVT_RCVD_RLS_RSP,
128     CH_EVT_RCVD_RPN_CMD,
129     CH_EVT_RCVD_RPN_REQ,
130     CH_EVT_RCVD_CREDITS,
131     CH_EVT_MULTIPLEXER_READY,
132     CH_EVT_READY_TO_SEND,
133 } RFCOMM_CHANNEL_EVENT;
134 
135 typedef struct rfcomm_channel_event {
136     RFCOMM_CHANNEL_EVENT type;
137     uint16_t dummy; // force rfcomm_channel_event to be 2-byte aligned -> avoid -Wcast-align warning
138 } rfcomm_channel_event_t;
139 
140 typedef struct rfcomm_channel_event_pn {
141     rfcomm_channel_event_t super;
142     uint16_t max_frame_size;
143     uint8_t  priority;
144     uint8_t  credits_outgoing;
145 } rfcomm_channel_event_pn_t;
146 
147 typedef struct rfcomm_channel_event_rpn {
148     rfcomm_channel_event_t super;
149     rfcomm_rpn_data_t data;
150 } rfcomm_channel_event_rpn_t;
151 
152 typedef struct rfcomm_channel_event_rls {
153     rfcomm_channel_event_t super;
154     uint8_t line_status;
155 } rfcomm_channel_event_rls_t;
156 
157 typedef struct rfcomm_channel_event_msc {
158     rfcomm_channel_event_t super;
159     uint8_t modem_status;
160 } rfcomm_channel_event_msc_t;
161 
162 
163 // global rfcomm data
164 static uint16_t      rfcomm_client_cid_generator;  // used for client channel IDs
165 
166 // linked lists for all
167 static btstack_linked_list_t rfcomm_multiplexers = NULL;
168 static btstack_linked_list_t rfcomm_channels = NULL;
169 static btstack_linked_list_t rfcomm_services = NULL;
170 
171 static gap_security_level_t rfcomm_security_level;
172 
173 #ifdef RFCOMM_USE_ERTM
174 static uint16_t rfcomm_ertm_id;
175 void (*rfcomm_ertm_request_callback)(rfcomm_ertm_request_t * request);
176 void (*rfcomm_ertm_released_callback)(uint16_t ertm_id);
177 #endif
178 
179 #ifdef RFCOMM_USE_OUTGOING_BUFFER
180 static uint8_t outgoing_buffer[1030];
181 #endif
182 
183 static int  rfcomm_channel_can_send(rfcomm_channel_t * channel);
184 static int  rfcomm_channel_ready_for_open(rfcomm_channel_t *channel);
185 static int rfcomm_channel_ready_to_send(rfcomm_channel_t * channel);
186 static void rfcomm_channel_state_machine_with_channel(rfcomm_channel_t *channel, const rfcomm_channel_event_t *event, int * out_channel_valid);
187 static void rfcomm_channel_state_machine_with_dlci(rfcomm_multiplexer_t * multiplexer, uint8_t dlci, const rfcomm_channel_event_t *event);
188 static void rfcomm_emit_can_send_now(rfcomm_channel_t *channel);
189 static int rfcomm_multiplexer_ready_to_send(rfcomm_multiplexer_t * multiplexer);
190 static void rfcomm_multiplexer_state_machine(rfcomm_multiplexer_t * multiplexer, RFCOMM_MULTIPLEXER_EVENT event);
191 
192 // MARK: RFCOMM CLIENT EVENTS
193 
194 static rfcomm_channel_t * rfcomm_channel_for_rfcomm_cid(uint16_t rfcomm_cid){
195     btstack_linked_item_t *it;
196     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
197         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
198         if (channel->rfcomm_cid == rfcomm_cid) {
199             return channel;
200         };
201     }
202     return NULL;
203 }
204 
205 static uint16_t rfcomm_next_client_cid(void){
206     do {
207         if (rfcomm_client_cid_generator == 0xffff) {
208             // don't use 0 as channel id
209             rfcomm_client_cid_generator = 1;
210         } else {
211             rfcomm_client_cid_generator++;
212         }
213     } while (rfcomm_channel_for_rfcomm_cid(rfcomm_client_cid_generator) != NULL);
214     return rfcomm_client_cid_generator;
215 }
216 
217 #ifdef RFCOMM_USE_ERTM
218 static rfcomm_multiplexer_t * rfcomm_multiplexer_for_ertm_id(uint16_t ertm_id) {
219     btstack_linked_item_t *it;
220     for (it = (btstack_linked_item_t *) rfcomm_multiplexers; it ; it = it->next){
221         rfcomm_multiplexer_t * multiplexer = ((rfcomm_multiplexer_t *) it);
222         if (multiplexer->ertm_id == ertm_id) {
223             return multiplexer;
224         };
225     }
226     return NULL;
227 }
228 
229 static uint16_t rfcomm_next_ertm_id(void){
230     do {
231         if (rfcomm_ertm_id == 0xffff) {
232             // don't use 0 as channel id
233             rfcomm_ertm_id = 1;
234         } else {
235             rfcomm_ertm_id++;
236         }
237     } while (rfcomm_multiplexer_for_ertm_id(rfcomm_ertm_id) != NULL);
238     return rfcomm_ertm_id;
239 }
240 
241 #endif
242 
243 // data: event (8), len(8), address(48), channel (8), rfcomm_cid (16)
244 static void rfcomm_emit_connection_request(rfcomm_channel_t *channel) {
245     log_info("RFCOMM_EVENT_INCOMING_CONNECTION addr %s channel #%u cid 0x%02x",
246              bd_addr_to_str(channel->multiplexer->remote_addr), channel->dlci>>1, channel->rfcomm_cid);
247     uint8_t event[11];
248     event[0] = RFCOMM_EVENT_INCOMING_CONNECTION;
249     event[1] = sizeof(event) - 2;
250     reverse_bd_addr(channel->multiplexer->remote_addr, &event[2]);
251     event[8] = channel->dlci >> 1;
252     little_endian_store_16(event, 9, channel->rfcomm_cid);
253     hci_dump_packet(HCI_EVENT_PACKET, 0, event, sizeof(event));
254 	(channel->packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
255 }
256 
257 // API Change: BTstack-0.3.50x uses
258 // data: event(8), len(8), status (8), address (48), server channel(8), rfcomm_cid(16), max frame size(16)
259 // next Cydia release will use SVN version of this
260 // data: event(8), len(8), status (8), address (48), handle (16), server channel(8), rfcomm_cid(16), max frame size(16)
261 static void rfcomm_emit_channel_opened(rfcomm_channel_t *channel, uint8_t status) {
262     log_info("RFCOMM_EVENT_CHANNEL_OPENED status 0x%x addr %s handle 0x%x channel #%u cid 0x%02x mtu %u",
263              status, bd_addr_to_str(channel->multiplexer->remote_addr), channel->multiplexer->con_handle,
264              channel->dlci>>1, channel->rfcomm_cid, channel->max_frame_size);
265     uint8_t event[18];
266     uint8_t pos = 0;
267     event[pos++] = RFCOMM_EVENT_CHANNEL_OPENED;  // 0
268     event[pos++] = sizeof(event) - 2;                   // 1
269     event[pos++] = status;                              // 2
270     reverse_bd_addr(channel->multiplexer->remote_addr, &event[pos]); pos += 6; // 3
271     little_endian_store_16(event,  pos, channel->multiplexer->con_handle);   pos += 2; // 9
272 	event[pos++] = channel->dlci >> 1;                                      // 11
273 	little_endian_store_16(event, pos, channel->rfcomm_cid); pos += 2;                 // 12 - channel ID
274 	little_endian_store_16(event, pos, channel->max_frame_size); pos += 2;   // max frame size
275     event[pos++] = channel->service ? 1 : 0;    // linked to service -> incoming
276     hci_dump_packet(HCI_EVENT_PACKET, 0, event, sizeof(event));
277 	(channel->packet_handler)(HCI_EVENT_PACKET, 0, event, pos);
278 
279     // if channel opened successfully, also send can send now if possible
280     if (status) return;
281     if (rfcomm_channel_can_send(channel)){
282         rfcomm_emit_can_send_now(channel);
283     }
284 }
285 
286 // data: event(8), len(8), rfcomm_cid(16)
287 static void rfcomm_emit_channel_closed(rfcomm_channel_t * channel) {
288     log_info("RFCOMM_EVENT_CHANNEL_CLOSED cid 0x%02x", channel->rfcomm_cid);
289     uint8_t event[4];
290     event[0] = RFCOMM_EVENT_CHANNEL_CLOSED;
291     event[1] = sizeof(event) - 2;
292     little_endian_store_16(event, 2, channel->rfcomm_cid);
293     hci_dump_packet(HCI_EVENT_PACKET, 0, event, sizeof(event));
294 	(channel->packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
295 }
296 
297 static void rfcomm_emit_remote_line_status(rfcomm_channel_t *channel, uint8_t line_status){
298     log_info("RFCOMM_EVENT_REMOTE_LINE_STATUS cid 0x%02x c, line status 0x%x", channel->rfcomm_cid, line_status);
299     uint8_t event[5];
300     event[0] = RFCOMM_EVENT_REMOTE_LINE_STATUS;
301     event[1] = sizeof(event) - 2;
302     little_endian_store_16(event, 2, channel->rfcomm_cid);
303     event[4] = line_status;
304     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
305     (channel->packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
306 }
307 
308 static void rfcomm_emit_port_configuration(rfcomm_channel_t *channel){
309     // notify client about new settings
310     uint8_t event[2+sizeof(rfcomm_rpn_data_t)];
311     event[0] = RFCOMM_EVENT_PORT_CONFIGURATION;
312     event[1] = sizeof(rfcomm_rpn_data_t);
313     (void)memcpy(&event[2], (uint8_t *)&channel->rpn_data,
314                  sizeof(rfcomm_rpn_data_t));
315     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
316     (channel->packet_handler)(HCI_EVENT_PACKET, channel->rfcomm_cid, event, sizeof(event));
317 }
318 
319 static void rfcomm_emit_can_send_now(rfcomm_channel_t *channel) {
320     log_debug("RFCOMM_EVENT_CHANNEL_CAN_SEND_NOW local_cid 0x%x", channel->rfcomm_cid);
321     uint8_t event[4];
322     event[0] = RFCOMM_EVENT_CAN_SEND_NOW;
323     event[1] = sizeof(event) - 2;
324     little_endian_store_16(event, 2, channel->rfcomm_cid);
325     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
326     (channel->packet_handler)(HCI_EVENT_PACKET, channel->rfcomm_cid, event, sizeof(event));
327 }
328 
329 // MARK RFCOMM RPN DATA HELPER
330 static void rfcomm_rpn_data_set_defaults(rfcomm_rpn_data_t * rpn_data){
331         rpn_data->baud_rate = RPN_BAUD_9600;  /* 9600 bps */
332         rpn_data->flags = 0x03;               /* 8-n-1 */
333         rpn_data->flow_control = 0;           /* no flow control */
334         rpn_data->xon  = 0xd1;                /* XON */
335         rpn_data->xoff = 0xd3;                /* XOFF */
336         rpn_data->parameter_mask_0 = 0x7f;    /* parameter mask, all values set */
337         rpn_data->parameter_mask_1 = 0x3f;    /* parameter mask, all values set */
338 }
339 
340 static void rfcomm_rpn_data_update(rfcomm_rpn_data_t * dest, rfcomm_rpn_data_t * src){
341     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_BAUD){
342         dest->baud_rate = src->baud_rate;
343     }
344     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_DATA_BITS){
345         dest->flags = (dest->flags & 0xfc) | (src->flags & 0x03);
346     }
347     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_STOP_BITS){
348         dest->flags = (dest->flags & 0xfb) | (src->flags & 0x04);
349     }
350     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_PARITY){
351         dest->flags = (dest->flags & 0xf7) | (src->flags & 0x08);
352     }
353     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_PARITY_TYPE){
354         dest->flags = (dest->flags & 0xfc) | (src->flags & 0x30);
355     }
356     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_XON_CHAR){
357         dest->xon = src->xon;
358     }
359     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_XOFF_CHAR){
360         dest->xoff = src->xoff;
361     }
362     int i;
363     for (i=0; i < 6 ; i++){
364         uint8_t mask = 1 << i;
365         if (src->parameter_mask_1 & mask){
366             dest->flags = (dest->flags & ~mask) | (src->flags & mask);
367         }
368     }
369     // always copy parameter mask, too. informative for client, needed for response
370     dest->parameter_mask_0 = src->parameter_mask_0;
371     dest->parameter_mask_1 = src->parameter_mask_1;
372 }
373 // MARK: RFCOMM MULTIPLEXER HELPER
374 
375 static uint16_t rfcomm_max_frame_size_for_l2cap_mtu(uint16_t l2cap_mtu){
376     // Assume RFCOMM header without credits and 2 byte (14 bit) length field
377     uint16_t max_frame_size = l2cap_mtu - 5;
378     log_info("rfcomm_max_frame_size_for_l2cap_mtu:  %u -> %u", l2cap_mtu, max_frame_size);
379     return max_frame_size;
380 }
381 
382 static void rfcomm_multiplexer_initialize(rfcomm_multiplexer_t *multiplexer){
383     multiplexer->state = RFCOMM_MULTIPLEXER_CLOSED;
384     multiplexer->fcon = 1;
385     multiplexer->send_dm_for_dlci = 0;
386     multiplexer->max_frame_size = rfcomm_max_frame_size_for_l2cap_mtu(l2cap_max_mtu());
387     multiplexer->test_data_len = 0;
388     multiplexer->nsc_command = 0;
389 }
390 
391 static rfcomm_multiplexer_t * rfcomm_multiplexer_create_for_addr(bd_addr_t addr){
392 
393     // alloc structure
394     rfcomm_multiplexer_t * multiplexer = btstack_memory_rfcomm_multiplexer_get();
395     if (!multiplexer) return NULL;
396 
397     // fill in
398     rfcomm_multiplexer_initialize(multiplexer);
399     bd_addr_copy(multiplexer->remote_addr, addr);
400 
401     // add to services list
402     btstack_linked_list_add(&rfcomm_multiplexers, (btstack_linked_item_t *) multiplexer);
403 
404     return multiplexer;
405 }
406 
407 static rfcomm_multiplexer_t * rfcomm_multiplexer_for_addr(bd_addr_t addr){
408     btstack_linked_item_t *it;
409     for (it = (btstack_linked_item_t *) rfcomm_multiplexers; it ; it = it->next){
410         rfcomm_multiplexer_t * multiplexer = ((rfcomm_multiplexer_t *) it);
411         // ignore multiplexer in shutdown
412         if (multiplexer->state == RFCOMM_MULTIPLEXER_SHUTTING_DOWN) continue;
413         if (bd_addr_cmp(addr, multiplexer->remote_addr) == 0) {
414             return multiplexer;
415         };
416     }
417     return NULL;
418 }
419 
420 static rfcomm_multiplexer_t * rfcomm_multiplexer_for_l2cap_cid(uint16_t l2cap_cid) {
421     btstack_linked_item_t *it;
422     for (it = (btstack_linked_item_t *) rfcomm_multiplexers; it ; it = it->next){
423         rfcomm_multiplexer_t * multiplexer = ((rfcomm_multiplexer_t *) it);
424         if (multiplexer->l2cap_cid == l2cap_cid) {
425             return multiplexer;
426         };
427     }
428     return NULL;
429 }
430 
431 static int rfcomm_multiplexer_has_channels(rfcomm_multiplexer_t * multiplexer){
432     btstack_linked_item_t *it;
433     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
434         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
435         if (channel->multiplexer == multiplexer) {
436             return 1;
437         }
438     }
439     return 0;
440 }
441 
442 // MARK: RFCOMM CHANNEL HELPER
443 
444 static void rfcomm_dump_channels(void){
445     btstack_linked_item_t * it;
446     int channels = 0;
447     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
448         rfcomm_channel_t * channel = (rfcomm_channel_t *) it;
449         log_info("Channel #%u: addr %p, state %u", channels, channel, channel->state);
450         channels++;
451     }
452 }
453 
454 static void rfcomm_channel_initialize(rfcomm_channel_t *channel, rfcomm_multiplexer_t *multiplexer,
455                                rfcomm_service_t *service, uint8_t server_channel){
456 
457     // set defaults for port configuration (even for services)
458     rfcomm_rpn_data_set_defaults(&channel->rpn_data);
459 
460     channel->state            = RFCOMM_CHANNEL_CLOSED;
461     channel->state_var        = RFCOMM_CHANNEL_STATE_VAR_NONE;
462 
463     channel->multiplexer      = multiplexer;
464     channel->rfcomm_cid       = rfcomm_next_client_cid();
465     channel->max_frame_size   = multiplexer->max_frame_size;
466 
467     channel->credits_incoming = 0;
468     channel->credits_outgoing = 0;
469 
470     // incoming flow control not active
471     channel->new_credits_incoming  = RFCOMM_CREDITS;
472     channel->incoming_flow_control = 0;
473 
474     channel->rls_line_status       = RFCOMM_RLS_STATUS_INVALID;
475 
476     channel->service = service;
477 	if (service) {
478 		// incoming connection
479     	channel->dlci = (server_channel << 1) |  multiplexer->outgoing;
480         if (channel->max_frame_size > service->max_frame_size) {
481             channel->max_frame_size = service->max_frame_size;
482         }
483         channel->incoming_flow_control = service->incoming_flow_control;
484         channel->new_credits_incoming  = service->incoming_initial_credits;
485         channel->packet_handler        = service->packet_handler;
486 	} else {
487 		// outgoing connection
488 		channel->dlci = (server_channel << 1) | (multiplexer->outgoing ^ 1);
489 	}
490 }
491 
492 // service == NULL -> outgoing channel
493 static rfcomm_channel_t * rfcomm_channel_create(rfcomm_multiplexer_t * multiplexer,
494                                                 rfcomm_service_t * service, uint8_t server_channel){
495 
496     log_info("rfcomm_channel_create for service %p, channel %u --- list of channels:", service, server_channel);
497     rfcomm_dump_channels();
498 
499     // alloc structure
500     rfcomm_channel_t * channel = btstack_memory_rfcomm_channel_get();
501     if (!channel) return NULL;
502 
503     // fill in
504     rfcomm_channel_initialize(channel, multiplexer, service, server_channel);
505 
506     // add to services list
507     btstack_linked_list_add(&rfcomm_channels, (btstack_linked_item_t *) channel);
508 
509     return channel;
510 }
511 
512 static void rfcomm_notify_channel_can_send(void){
513     btstack_linked_list_iterator_t it;
514     btstack_linked_list_iterator_init(&it, &rfcomm_channels);
515     while (btstack_linked_list_iterator_has_next(&it)){
516         rfcomm_channel_t * channel = (rfcomm_channel_t *) btstack_linked_list_iterator_next(&it);
517         if (!channel->waiting_for_can_send_now) continue; // didn't try to send yet
518         if (!rfcomm_channel_can_send(channel)) continue;  // or cannot yet either
519 
520         channel->waiting_for_can_send_now = 0;
521         rfcomm_emit_can_send_now(channel);
522     }
523 }
524 
525 static rfcomm_channel_t * rfcomm_channel_for_multiplexer_and_dlci(rfcomm_multiplexer_t * multiplexer, uint8_t dlci){
526     btstack_linked_item_t *it;
527     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
528         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
529         if ((channel->dlci == dlci) && (channel->multiplexer == multiplexer)) {
530             return channel;
531         };
532     }
533     return NULL;
534 }
535 
536 static rfcomm_service_t * rfcomm_service_for_channel(uint8_t server_channel){
537     btstack_linked_item_t *it;
538     for (it = (btstack_linked_item_t *) rfcomm_services; it ; it = it->next){
539         rfcomm_service_t * service = ((rfcomm_service_t *) it);
540         if ( service->server_channel == server_channel){
541             return service;
542         };
543     }
544     return NULL;
545 }
546 
547 // MARK: RFCOMM SEND
548 
549 /**
550  * @param credits - only used for RFCOMM flow control in UIH wiht P/F = 1
551  */
552 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){
553 
554     if (!l2cap_can_send_packet_now(multiplexer->l2cap_cid)) return BTSTACK_ACL_BUFFERS_FULL;
555 
556 #ifdef RFCOMM_USE_OUTGOING_BUFFER
557     uint8_t * rfcomm_out_buffer = outgoing_buffer;
558 #else
559     l2cap_reserve_packet_buffer();
560     uint8_t * rfcomm_out_buffer = l2cap_get_outgoing_buffer();
561 #endif
562 
563 	uint16_t pos = 0;
564 	uint8_t crc_fields = 3;
565 
566 	rfcomm_out_buffer[pos++] = address;
567 	rfcomm_out_buffer[pos++] = control;
568 
569 	// length field can be 1 or 2 octets
570 	if (len < 128){
571 		rfcomm_out_buffer[pos++] = (len << 1)| 1;     // bits 0-6
572 	} else {
573 		rfcomm_out_buffer[pos++] = (len & 0x7f) << 1; // bits 0-6
574 		rfcomm_out_buffer[pos++] = len >> 7;          // bits 7-14
575 		crc_fields++;
576 	}
577 
578 	// add credits for UIH frames when PF bit is set
579 	if (control == BT_RFCOMM_UIH_PF){
580 		rfcomm_out_buffer[pos++] = credits;
581 	}
582 
583 	// copy actual data
584 	if (len) {
585 		(void)memcpy(&rfcomm_out_buffer[pos], data, len);
586 		pos += len;
587 	}
588 
589 	// UIH frames only calc FCS over address + control (5.1.1)
590 	if ((control & 0xef) == BT_RFCOMM_UIH){
591 		crc_fields = 2;
592 	}
593 	rfcomm_out_buffer[pos++] =  btstack_crc8_calc(rfcomm_out_buffer, crc_fields); // calc fcs
594 
595 #ifdef RFCOMM_USE_OUTGOING_BUFFER
596     int err = l2cap_send(multiplexer->l2cap_cid, rfcomm_out_buffer, pos);
597 #else
598     int err = l2cap_send_prepared(multiplexer->l2cap_cid, pos);
599 #endif
600 
601     return err;
602 }
603 
604 // simplified version of rfcomm_send_packet_for_multiplexer for prepared rfcomm packet (UIH, 2 byte len, no credits)
605 static int rfcomm_send_uih_prepared(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint16_t len){
606 
607     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) | (dlci << 2);
608     uint8_t control = BT_RFCOMM_UIH;
609 
610 #ifdef RFCOMM_USE_OUTGOING_BUFFER
611     uint8_t * rfcomm_out_buffer = outgoing_buffer;
612 #else
613     uint8_t * rfcomm_out_buffer = l2cap_get_outgoing_buffer();
614 #endif
615 
616     uint16_t pos = 0;
617     rfcomm_out_buffer[pos++] = address;
618     rfcomm_out_buffer[pos++] = control;
619     rfcomm_out_buffer[pos++] = (len & 0x7f) << 1; // bits 0-6
620     rfcomm_out_buffer[pos++] = len >> 7;          // bits 7-14
621 
622     // actual data is already in place
623     pos += len;
624 
625     // UIH frames only calc FCS over address + control (5.1.1)
626     rfcomm_out_buffer[pos++] =  btstack_crc8_calc(rfcomm_out_buffer, 2); // calc fcs
627 
628 #ifdef RFCOMM_USE_OUTGOING_BUFFER
629     int err = l2cap_send(multiplexer->l2cap_cid, rfcomm_out_buffer, pos);
630 #else
631     int err = l2cap_send_prepared(multiplexer->l2cap_cid, pos);
632 #endif
633 
634     return err;
635 }
636 
637 // C/R Flag in Address
638 // - terms: initiator = station that creates multiplexer with SABM
639 // - terms: responder = station that responds to multiplexer setup with UA
640 // "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"
641 //    - command initiator = 1 /response responder = 1
642 //    - command responder = 0 /response initiator = 0
643 // "For UIH frames, the C/R bit is always set according to section 5.4.3.1 in GSM 07.10.
644 //  This applies independently of what is contained wthin the UIH frames, either data or control messages."
645 //    - c/r = 1 for frames by initiating station, 0 = for frames by responding station
646 
647 // C/R Flag in Message
648 // "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."
649 //   - If the C/R bit is set to 1 the message is a command
650 //   - if it is set to 0 the message is a response.
651 
652 // temp/old messge construction
653 
654 // new object oriented version
655 static int rfcomm_send_sabm(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
656 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) | (dlci << 2);   // command
657     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_SABM, 0, NULL, 0);
658 }
659 
660 static int rfcomm_send_disc(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
661 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) | (dlci << 2);  // command
662     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_DISC, 0, NULL, 0);
663 }
664 
665 static int rfcomm_send_ua(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
666 	uint8_t address = (1 << 0) | ((multiplexer->outgoing ^ 1) << 1) | (dlci << 2); // response
667     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UA, 0, NULL, 0);
668 }
669 
670 static int rfcomm_send_dm_pf(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
671 	uint8_t address = (1 << 0) | ((multiplexer->outgoing ^ 1) << 1) | (dlci << 2); // response
672     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_DM_PF, 0, NULL, 0);
673 }
674 
675 static int rfcomm_send_uih_fc_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t fcon) {
676     uint8_t address = (1 << 0) | (multiplexer->outgoing<< 1);
677     uint8_t payload[2];
678     uint8_t pos = 0;
679     payload[pos++] = fcon ? BT_RFCOMM_FCON_RSP : BT_RFCOMM_FCOFF_RSP;
680     payload[pos++] = (0 << 1) | 1;  // len
681     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
682 }
683 
684 // static int rfcomm_send_uih_test_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t * data, uint16_t len) {
685 //     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
686 //     uint8_t payload[2+len];
687 //     uint8_t pos = 0;
688 //     payload[pos++] = BT_RFCOMM_TEST_CMD;
689 //     payload[pos++] = (len + 1) << 1 | 1;  // len
690 //     memcpy(&payload[pos], data, len);
691 //     pos += len;
692 //     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
693 // }
694 
695 static int rfcomm_send_uih_test_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t * data, uint16_t len) {
696     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
697     uint8_t payload[2+RFCOMM_TEST_DATA_MAX_LEN];
698     uint8_t pos = 0;
699     payload[pos++] = BT_RFCOMM_TEST_RSP;
700     if (len > RFCOMM_TEST_DATA_MAX_LEN) {
701         len = RFCOMM_TEST_DATA_MAX_LEN;
702     }
703     payload[pos++] = (len << 1) | 1;  // len
704     (void)memcpy(&payload[pos], data, len);
705     pos += len;
706     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
707 }
708 
709 static int rfcomm_send_uih_msc_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t signals) {
710 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
711 	uint8_t payload[4];
712 	uint8_t pos = 0;
713 	payload[pos++] = BT_RFCOMM_MSC_CMD;
714 	payload[pos++] = (2 << 1) | 1;  // len
715 	payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
716 	payload[pos++] = signals;
717 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
718 }
719 
720 static int rfcomm_send_uih_msc_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t signals) {
721 	uint8_t address = (1 << 0) | (multiplexer->outgoing<< 1);
722 	uint8_t payload[4];
723 	uint8_t pos = 0;
724 	payload[pos++] = BT_RFCOMM_MSC_RSP;
725 	payload[pos++] = (2 << 1) | 1;  // len
726 	payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
727 	payload[pos++] = signals;
728 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
729 }
730 
731 static int rfcomm_send_uih_nsc_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t command) {
732     uint8_t address = (1 << 0) | (multiplexer->outgoing<< 1);
733     uint8_t payload[3];
734     uint8_t pos = 0;
735     payload[pos++] = BT_RFCOMM_NSC_RSP;
736     payload[pos++] = (1 << 1) | 1;  // len
737     payload[pos++] = command;
738     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
739 }
740 
741 static int rfcomm_send_uih_pn_command(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint16_t max_frame_size){
742 	uint8_t payload[10];
743 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
744 	uint8_t pos = 0;
745 	payload[pos++] = BT_RFCOMM_PN_CMD;
746 	payload[pos++] = (8 << 1) | 1;  // len
747 	payload[pos++] = dlci;
748 	payload[pos++] = 0xf0; // pre-defined for Bluetooth, see 5.5.3 of TS 07.10 Adaption for RFCOMM
749 	payload[pos++] = 0; // priority
750 	payload[pos++] = 0; // max 60 seconds ack
751 	payload[pos++] = max_frame_size & 0xff; // max framesize low
752 	payload[pos++] = max_frame_size >> 8;   // max framesize high
753 	payload[pos++] = 0x00; // number of retransmissions
754 	payload[pos++] = 0x00; // (unused error recovery window) initial number of credits
755 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
756 }
757 
758 // "The response may not change the DLCI, the priority, the convergence layer, or the timer value." rfcomm_tutorial.pdf
759 static int rfcomm_send_uih_pn_response(rfcomm_multiplexer_t *multiplexer, uint8_t dlci,
760                                        uint8_t priority, uint16_t max_frame_size){
761 	uint8_t payload[10];
762 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
763 	uint8_t pos = 0;
764 	payload[pos++] = BT_RFCOMM_PN_RSP;
765 	payload[pos++] = (8 << 1) | 1;  // len
766 	payload[pos++] = dlci;
767 	payload[pos++] = 0xe0; // pre defined for Bluetooth, see 5.5.3 of TS 07.10 Adaption for RFCOMM
768 	payload[pos++] = priority; // priority
769 	payload[pos++] = 0; // max 60 seconds ack
770 	payload[pos++] = max_frame_size & 0xff; // max framesize low
771 	payload[pos++] = max_frame_size >> 8;   // max framesize high
772 	payload[pos++] = 0x00; // number of retransmissions
773 	payload[pos++] = 0x00; // (unused error recovery window) initial number of credits
774 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
775 }
776 
777 static int rfcomm_send_uih_rls_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t line_status) {
778     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
779     uint8_t payload[4];
780     uint8_t pos = 0;
781     payload[pos++] = BT_RFCOMM_RLS_CMD;
782     payload[pos++] = (2 << 1) | 1;  // len
783     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
784     payload[pos++] = line_status;
785     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
786 }
787 
788 static int rfcomm_send_uih_rls_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t line_status) {
789     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
790     uint8_t payload[4];
791     uint8_t pos = 0;
792     payload[pos++] = BT_RFCOMM_RLS_RSP;
793     payload[pos++] = (2 << 1) | 1;  // len
794     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
795     payload[pos++] = line_status;
796     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
797 }
798 
799 static int rfcomm_send_uih_rpn_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, rfcomm_rpn_data_t *rpn_data) {
800     uint8_t payload[10];
801     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
802     uint8_t pos = 0;
803     payload[pos++] = BT_RFCOMM_RPN_CMD;
804     payload[pos++] = (8 << 1) | 1;  // len
805     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
806     payload[pos++] = rpn_data->baud_rate;
807     payload[pos++] = rpn_data->flags;
808     payload[pos++] = rpn_data->flow_control;
809     payload[pos++] = rpn_data->xon;
810     payload[pos++] = rpn_data->xoff;
811     payload[pos++] = rpn_data->parameter_mask_0;
812     payload[pos++] = rpn_data->parameter_mask_1;
813     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
814 }
815 
816 static int rfcomm_send_uih_rpn_req(rfcomm_multiplexer_t *multiplexer, uint8_t dlci) {
817     uint8_t payload[3];
818     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
819     uint8_t pos = 0;
820     payload[pos++] = BT_RFCOMM_RPN_CMD;
821     payload[pos++] = (1 << 1) | 1;  // len
822     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
823     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
824 }
825 
826 static int rfcomm_send_uih_rpn_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, rfcomm_rpn_data_t *rpn_data) {
827 	uint8_t payload[10];
828 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
829 	uint8_t pos = 0;
830 	payload[pos++] = BT_RFCOMM_RPN_RSP;
831 	payload[pos++] = (8 << 1) | 1;  // len
832 	payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
833 	payload[pos++] = rpn_data->baud_rate;
834 	payload[pos++] = rpn_data->flags;
835 	payload[pos++] = rpn_data->flow_control;
836 	payload[pos++] = rpn_data->xon;
837 	payload[pos++] = rpn_data->xoff;
838 	payload[pos++] = rpn_data->parameter_mask_0;
839 	payload[pos++] = rpn_data->parameter_mask_1;
840 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
841 }
842 
843 static void rfcomm_send_uih_credits(rfcomm_multiplexer_t *multiplexer, uint8_t dlci,  uint8_t credits){
844     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) |  (dlci << 2);
845     rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH_PF, credits, NULL, 0);
846 }
847 
848 // depending on channel state emit channel opened with status or channel closed
849 static void rfcomm_channel_emit_final_event(rfcomm_channel_t * channel, uint8_t status){
850     // emit appropriate events
851     switch(channel->state){
852         case RFCOMM_CHANNEL_OPEN:
853         case RFCOMM_CHANNEL_W4_UA_AFTER_DISC:
854             rfcomm_emit_channel_closed(channel);
855             break;
856         case RFCOMM_CHANNEL_SEND_UA_AFTER_DISC:
857             // remote didn't wait until we send the UA disc
858             // close event already emitted
859             break;
860         default:
861             rfcomm_emit_channel_opened(channel, status);
862             break;
863     }
864 }
865 
866 // MARK: RFCOMM MULTIPLEXER
867 static void rfcomm_multiplexer_stop_timer(rfcomm_multiplexer_t * multiplexer){
868     if (multiplexer->timer_active) {
869         btstack_run_loop_remove_timer(&multiplexer->timer);
870         multiplexer->timer_active = 0;
871     }
872 }
873 static void rfcomm_multiplexer_free(rfcomm_multiplexer_t * multiplexer){
874     btstack_linked_list_remove( &rfcomm_multiplexers, (btstack_linked_item_t *) multiplexer);
875     btstack_memory_rfcomm_multiplexer_free(multiplexer);
876 }
877 
878 static void rfcomm_multiplexer_finalize(rfcomm_multiplexer_t * multiplexer){
879     // remove (potential) timer
880     rfcomm_multiplexer_stop_timer(multiplexer);
881 
882     // close and remove all channels
883     btstack_linked_item_t *it = (btstack_linked_item_t *) &rfcomm_channels;
884     while (it->next){
885         rfcomm_channel_t * channel = (rfcomm_channel_t *) it->next;
886         if (channel->multiplexer == multiplexer) {
887             // emit open with status or closed
888             rfcomm_channel_emit_final_event(channel, RFCOMM_MULTIPLEXER_STOPPED);
889             // remove from list
890             it->next = it->next->next;
891             // free channel struct
892             btstack_memory_rfcomm_channel_free(channel);
893         } else {
894             it = it->next;
895         }
896     }
897 
898     // remove mutliplexer
899     rfcomm_multiplexer_free(multiplexer);
900 }
901 
902 static void rfcomm_multiplexer_timer_handler(btstack_timer_source_t *timer){
903     rfcomm_multiplexer_t * multiplexer = (rfcomm_multiplexer_t*) btstack_run_loop_get_timer_context(timer);
904     if (rfcomm_multiplexer_has_channels(multiplexer)) return;
905 
906     log_info("rfcomm_multiplexer_timer_handler timeout: shutting down multiplexer! (no channels)");
907     uint16_t l2cap_cid = multiplexer->l2cap_cid;
908     rfcomm_multiplexer_finalize(multiplexer);
909     l2cap_disconnect(l2cap_cid, 0x13);
910 }
911 
912 static void rfcomm_multiplexer_prepare_idle_timer(rfcomm_multiplexer_t * multiplexer){
913     if (multiplexer->timer_active) {
914         btstack_run_loop_remove_timer(&multiplexer->timer);
915         multiplexer->timer_active = 0;
916     }
917     if (rfcomm_multiplexer_has_channels(multiplexer)) return;
918 
919     // start idle timer for multiplexer timeout check as there are no rfcomm channels yet
920     btstack_run_loop_set_timer(&multiplexer->timer, RFCOMM_MULIPLEXER_TIMEOUT_MS);
921     btstack_run_loop_set_timer_handler(&multiplexer->timer, rfcomm_multiplexer_timer_handler);
922     btstack_run_loop_set_timer_context(&multiplexer->timer, multiplexer);
923     btstack_run_loop_add_timer(&multiplexer->timer);
924     multiplexer->timer_active = 1;
925 }
926 
927 static void rfcomm_multiplexer_opened(rfcomm_multiplexer_t *multiplexer){
928     log_info("Multiplexer up and running");
929     multiplexer->state = RFCOMM_MULTIPLEXER_OPEN;
930 
931     const rfcomm_channel_event_t event = { CH_EVT_MULTIPLEXER_READY, 0};
932 
933     // transition of channels that wait for multiplexer
934     btstack_linked_item_t *it;
935     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
936         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
937         if (channel->multiplexer != multiplexer) continue;
938         int rfcomm_channel_valid = 1;
939         rfcomm_channel_state_machine_with_channel(channel, &event, &rfcomm_channel_valid);
940         if (rfcomm_channel_valid && rfcomm_channel_ready_to_send(channel)){
941             l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
942         }
943     }
944     rfcomm_multiplexer_prepare_idle_timer(multiplexer);
945 
946     // request can send now for multiplexer if ready
947     if (rfcomm_multiplexer_ready_to_send(multiplexer)){
948         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
949     }
950 }
951 
952 static void rfcomm_handle_can_send_now(uint16_t l2cap_cid){
953 
954     log_debug("rfcomm_handle_can_send_now enter: %u", l2cap_cid);
955 
956     btstack_linked_list_iterator_t it;
957     int token_consumed = 0;
958 
959     // forward token to multiplexer
960     btstack_linked_list_iterator_init(&it, &rfcomm_multiplexers);
961     while (!token_consumed && btstack_linked_list_iterator_has_next(&it)){
962         rfcomm_multiplexer_t * multiplexer = (rfcomm_multiplexer_t *) btstack_linked_list_iterator_next(&it);
963         if (multiplexer->l2cap_cid != l2cap_cid) continue;
964         if (rfcomm_multiplexer_ready_to_send(multiplexer)){
965             log_debug("rfcomm_handle_can_send_now enter: multiplexer token");
966             token_consumed = 1;
967             rfcomm_multiplexer_state_machine(multiplexer, MULT_EV_READY_TO_SEND);
968         }
969     }
970 
971     // forward token to channel state machine
972     btstack_linked_list_iterator_init(&it, &rfcomm_channels);
973     while (!token_consumed && btstack_linked_list_iterator_has_next(&it)){
974         rfcomm_channel_t * channel = (rfcomm_channel_t *) btstack_linked_list_iterator_next(&it);
975         if (channel->multiplexer->l2cap_cid != l2cap_cid) continue;
976         // channel state machine
977         if (rfcomm_channel_ready_to_send(channel)){
978             log_debug("rfcomm_handle_can_send_now enter: channel token");
979             token_consumed = 1;
980             const rfcomm_channel_event_t event = { CH_EVT_READY_TO_SEND, 0 };
981             int rfcomm_channel_valid = 1;
982             rfcomm_channel_state_machine_with_channel(channel, &event, &rfcomm_channel_valid);
983         }
984     }
985 
986     // forward token to client
987     btstack_linked_list_iterator_init(&it, &rfcomm_channels);
988     while (!token_consumed && btstack_linked_list_iterator_has_next(&it)){
989         rfcomm_channel_t * channel = (rfcomm_channel_t *) btstack_linked_list_iterator_next(&it);
990         if (channel->multiplexer->l2cap_cid != l2cap_cid) continue;
991         // client waiting for can send now
992         if (!channel->waiting_for_can_send_now)    continue;
993         if ((channel->multiplexer->fcon & 1) == 0) continue;
994         if (!channel->credits_outgoing){
995             log_debug("rfcomm_handle_can_send_now waiting to send but no credits (ignore)");
996             continue;
997         }
998 
999         log_debug("rfcomm_handle_can_send_now enter: client token");
1000         token_consumed = 1;
1001         channel->waiting_for_can_send_now = 0;
1002         rfcomm_emit_can_send_now(channel);
1003     }
1004 
1005     // if token was consumed, request another one
1006     if (token_consumed) {
1007         l2cap_request_can_send_now_event(l2cap_cid);
1008     }
1009 
1010     log_debug("rfcomm_handle_can_send_now exit");
1011 }
1012 
1013 static void rfcomm_multiplexer_set_state_and_request_can_send_now_event(rfcomm_multiplexer_t * multiplexer, RFCOMM_MULTIPLEXER_STATE state){
1014     multiplexer->state = state;
1015     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1016 }
1017 
1018 /**
1019  * @return handled packet
1020  */
1021 static int rfcomm_hci_event_handler(uint8_t *packet, uint16_t size){
1022 
1023     UNUSED(size);   // ok: handling own l2cap events
1024 
1025     bd_addr_t event_addr;
1026     uint16_t  psm;
1027     uint16_t l2cap_cid;
1028     hci_con_handle_t con_handle;
1029     rfcomm_multiplexer_t *multiplexer = NULL;
1030     uint8_t status;
1031 
1032     switch (hci_event_packet_get_type(packet)) {
1033 
1034         // accept incoming rfcomm connection if no multiplexer exists yet
1035         case L2CAP_EVENT_INCOMING_CONNECTION:
1036             // data: event(8), len(8), address(48), handle (16),  psm (16), source cid(16) dest cid(16)
1037             reverse_bd_addr(&packet[2], event_addr);
1038             con_handle = little_endian_read_16(packet,  8);
1039             psm        = little_endian_read_16(packet, 10);
1040             l2cap_cid  = little_endian_read_16(packet, 12);
1041 
1042             if (psm != BLUETOOTH_PROTOCOL_RFCOMM) break;
1043 
1044             multiplexer = rfcomm_multiplexer_for_addr(event_addr);
1045 
1046             if (multiplexer) {
1047                 log_info("INCOMING_CONNECTION (l2cap_cid 0x%02x) for BLUETOOTH_PROTOCOL_RFCOMM => decline - multiplexer already exists", l2cap_cid);
1048                 l2cap_decline_connection(l2cap_cid);
1049                 return 1;
1050             }
1051 
1052             // create and inititialize new multiplexer instance (incoming)
1053             multiplexer = rfcomm_multiplexer_create_for_addr(event_addr);
1054             if (!multiplexer){
1055                 log_info("INCOMING_CONNECTION (l2cap_cid 0x%02x) for BLUETOOTH_PROTOCOL_RFCOMM => decline - no memory left", l2cap_cid);
1056                 l2cap_decline_connection(l2cap_cid);
1057                 return 1;
1058             }
1059 
1060             multiplexer->con_handle = con_handle;
1061             multiplexer->l2cap_cid = l2cap_cid;
1062             //
1063             multiplexer->state = RFCOMM_MULTIPLEXER_W4_SABM_0;
1064             log_info("L2CAP_EVENT_INCOMING_CONNECTION (l2cap_cid 0x%02x) for BLUETOOTH_PROTOCOL_RFCOMM => accept", l2cap_cid);
1065 
1066 #ifdef RFCOMM_USE_ERTM
1067             // request
1068             rfcomm_ertm_request_t request;
1069             memset(&request, 0, sizeof(rfcomm_ertm_request_t));
1070             (void)memcpy(request.addr, event_addr, 6);
1071             request.ertm_id = rfcomm_next_ertm_id();
1072             if (rfcomm_ertm_request_callback){
1073                 (*rfcomm_ertm_request_callback)(&request);
1074             }
1075             if (request.ertm_config && request.ertm_buffer && request.ertm_buffer_size){
1076                 multiplexer->ertm_id = request.ertm_id;
1077                 l2cap_accept_ertm_connection(l2cap_cid, request.ertm_config, request.ertm_buffer, request.ertm_buffer_size);
1078                 return 1;
1079             }
1080 #endif
1081 
1082             l2cap_accept_connection(l2cap_cid);
1083             return 1;
1084 
1085         // l2cap connection opened -> store l2cap_cid, remote_addr
1086         case L2CAP_EVENT_CHANNEL_OPENED:
1087 
1088             if (little_endian_read_16(packet, 11) != BLUETOOTH_PROTOCOL_RFCOMM) break;
1089 
1090             status = packet[2];
1091             log_info("L2CAP_EVENT_CHANNEL_OPENED for BLUETOOTH_PROTOCOL_RFCOMM, status %u", status);
1092 
1093             // get multiplexer for remote addr
1094             con_handle = little_endian_read_16(packet, 9);
1095             l2cap_cid = little_endian_read_16(packet, 13);
1096             reverse_bd_addr(&packet[3], event_addr);
1097             multiplexer = rfcomm_multiplexer_for_addr(event_addr);
1098             if (!multiplexer) {
1099                 log_error("L2CAP_EVENT_CHANNEL_OPENED but no multiplexer prepared");
1100                 return 1;
1101             }
1102 
1103             // on l2cap open error discard everything
1104             if (status){
1105 
1106                 // remove (potential) timer
1107                 rfcomm_multiplexer_stop_timer(multiplexer);
1108 
1109                 // mark multiplexer as shutting down
1110                 multiplexer->state = RFCOMM_MULTIPLEXER_SHUTTING_DOWN;
1111 
1112                 // emit rfcomm_channel_opened with status and free channel
1113                 // note: repeatedly go over list until full iteration causes no further change
1114                 int done;
1115                 do {
1116                     done = 1;
1117                     btstack_linked_item_t * it = (btstack_linked_item_t *) &rfcomm_channels;
1118                     while (it->next) {
1119                         rfcomm_channel_t * channel = (rfcomm_channel_t *) it->next;
1120                         if (channel->multiplexer == multiplexer){
1121                             done = 0;
1122                             rfcomm_emit_channel_opened(channel, status);
1123                             btstack_linked_list_remove(&rfcomm_channels, (btstack_linked_item_t *) channel);
1124                             btstack_memory_rfcomm_channel_free(channel);
1125                             break;
1126                         } else {
1127                             it = it->next;
1128                         }
1129                     }
1130                 } while (!done);
1131 
1132                 // free multiplexer
1133                 rfcomm_multiplexer_free(multiplexer);
1134                 return 1;
1135             }
1136 
1137             // following could be: rfcom_multiplexer_state_machein(..., EVENT_L2CAP_OPENED)
1138 
1139             // set max frame size based on l2cap MTU
1140             multiplexer->max_frame_size = rfcomm_max_frame_size_for_l2cap_mtu(little_endian_read_16(packet, 17));
1141 
1142             if (multiplexer->state == RFCOMM_MULTIPLEXER_W4_CONNECT) {
1143                 log_info("L2CAP_EVENT_CHANNEL_OPENED: outgoing connection");
1144                 // wrong remote addr
1145                 if (bd_addr_cmp(event_addr, multiplexer->remote_addr)) break;
1146                 multiplexer->l2cap_cid = l2cap_cid;
1147                 multiplexer->con_handle = con_handle;
1148                 // send SABM #0
1149                 rfcomm_multiplexer_set_state_and_request_can_send_now_event(multiplexer, RFCOMM_MULTIPLEXER_SEND_SABM_0);
1150 
1151             }
1152             return 1;
1153 
1154             // l2cap disconnect -> state = RFCOMM_MULTIPLEXER_CLOSED;
1155 
1156         // Notify channel packet handler if they can send now
1157         case L2CAP_EVENT_CAN_SEND_NOW:
1158             l2cap_cid = l2cap_event_can_send_now_get_local_cid(packet);
1159             rfcomm_handle_can_send_now(l2cap_cid);
1160             return 1;
1161 
1162         case L2CAP_EVENT_CHANNEL_CLOSED:
1163             // data: event (8), len(8), channel (16)
1164             l2cap_cid = little_endian_read_16(packet, 2);
1165             multiplexer = rfcomm_multiplexer_for_l2cap_cid(l2cap_cid);
1166             log_info("L2CAP_EVENT_CHANNEL_CLOSED cid 0x%0x, mult %p", l2cap_cid, multiplexer);
1167             if (!multiplexer) break;
1168             log_info("L2CAP_EVENT_CHANNEL_CLOSED state %u", multiplexer->state);
1169             // no need to call l2cap_disconnect here, as it's already closed
1170             rfcomm_multiplexer_finalize(multiplexer);
1171             return 1;
1172 
1173 #ifdef RFCOMM_USE_ERTM
1174         case L2CAP_EVENT_ERTM_BUFFER_RELEASED:
1175             l2cap_cid = l2cap_event_ertm_buffer_released_get_local_cid(packet);
1176             multiplexer = rfcomm_multiplexer_for_l2cap_cid(l2cap_cid);
1177             if (multiplexer) {
1178                 log_info("buffer for ertm id %u released", multiplexer->ertm_id);
1179                 if (rfcomm_ertm_released_callback){
1180                     (*rfcomm_ertm_released_callback)(multiplexer->ertm_id);
1181                 }
1182             }
1183             break;
1184 #endif
1185 
1186         default:
1187             break;
1188     }
1189     return 0;
1190 }
1191 
1192 static int rfcomm_multiplexer_l2cap_packet_handler(uint16_t channel, uint8_t *packet, uint16_t size){
1193     // get or create a multiplexer for a certain device
1194     rfcomm_multiplexer_t *multiplexer = rfcomm_multiplexer_for_l2cap_cid(channel);
1195     if (!multiplexer) return 0;
1196 
1197     uint16_t l2cap_cid = multiplexer->l2cap_cid;
1198 
1199 	// but only care for multiplexer control channel
1200     uint8_t frame_dlci = packet[0] >> 2;
1201     if (frame_dlci) return 0;
1202     const uint8_t length_offset = (packet[2] & 1) ^ 1;  // to be used for pos >= 3
1203     const uint8_t credit_offset = ((packet[1] & BT_RFCOMM_UIH_PF) == BT_RFCOMM_UIH_PF) ? 1 : 0;   // credits for uih_pf frames
1204     const uint8_t payload_offset = 3 + length_offset + credit_offset;
1205     switch (packet[1]){
1206 
1207         case BT_RFCOMM_SABM:
1208             if (multiplexer->state == RFCOMM_MULTIPLEXER_W4_SABM_0){
1209                 log_info("Received SABM #0");
1210                 multiplexer->outgoing = 0;
1211                 rfcomm_multiplexer_set_state_and_request_can_send_now_event(multiplexer, RFCOMM_MULTIPLEXER_SEND_UA_0);
1212                 return 1;
1213             }
1214             break;
1215 
1216         case BT_RFCOMM_UA:
1217             if (multiplexer->state == RFCOMM_MULTIPLEXER_W4_UA_0) {
1218                 // UA #0 -> send UA #0, state = RFCOMM_MULTIPLEXER_OPEN
1219                 log_info("Received UA #0 ");
1220                 rfcomm_multiplexer_opened(multiplexer);
1221                 return 1;
1222             }
1223             break;
1224 
1225         case BT_RFCOMM_DISC:
1226             // DISC #0 -> send UA #0, close multiplexer
1227             log_info("Received DISC #0, (ougoing = %u)", multiplexer->outgoing);
1228             rfcomm_multiplexer_set_state_and_request_can_send_now_event(multiplexer, RFCOMM_MULTIPLEXER_SEND_UA_0_AND_DISC);
1229             return 1;
1230 
1231         case BT_RFCOMM_DM:
1232             // DM #0 - we shouldn't get this, just give up
1233             log_info("Received DM #0");
1234             log_info("-> Closing down multiplexer");
1235             rfcomm_multiplexer_finalize(multiplexer);
1236             l2cap_disconnect(l2cap_cid, 0x13);
1237             return 1;
1238 
1239         case BT_RFCOMM_UIH:
1240             if (packet[payload_offset] == BT_RFCOMM_CLD_CMD){
1241                 // Multiplexer close down (CLD) -> close mutliplexer
1242                 log_info("Received Multiplexer close down command");
1243                 log_info("-> Closing down multiplexer");
1244                 rfcomm_multiplexer_finalize(multiplexer);
1245                 l2cap_disconnect(l2cap_cid, 0x13);
1246                 return 1;
1247             }
1248             switch (packet[payload_offset]){
1249                 case BT_RFCOMM_CLD_CMD:
1250                      // Multiplexer close down (CLD) -> close mutliplexer
1251                     log_info("Received Multiplexer close down command");
1252                     log_info("-> Closing down multiplexer");
1253                     rfcomm_multiplexer_finalize(multiplexer);
1254                     l2cap_disconnect(l2cap_cid, 0x13);
1255                     return 1;
1256 
1257                 case BT_RFCOMM_FCON_CMD:
1258                     multiplexer->fcon = 0x81;
1259                     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1260                     return 1;
1261 
1262                 case BT_RFCOMM_FCOFF_CMD:
1263                     multiplexer->fcon = 0x80;
1264                     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1265                     return 1;
1266 
1267                 case BT_RFCOMM_TEST_CMD: {
1268                     log_info("Received test command");
1269                     int len = packet[payload_offset+1] >> 1; // length < 125
1270                     if (len > RFCOMM_TEST_DATA_MAX_LEN){
1271                         len = RFCOMM_TEST_DATA_MAX_LEN;
1272                     }
1273                     len = btstack_min(len, size - 1 - payload_offset);  // avoid information leak
1274                     multiplexer->test_data_len = len;
1275                     (void)memcpy(multiplexer->test_data,
1276                                  &packet[payload_offset + 2], len);
1277                     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1278                     return 1;
1279                 }
1280                 default:
1281                     break;
1282             }
1283             break;
1284 
1285         default:
1286             break;
1287 
1288     }
1289     return 0;
1290 }
1291 
1292 static int rfcomm_multiplexer_ready_to_send(rfcomm_multiplexer_t * multiplexer){
1293     if (multiplexer->send_dm_for_dlci) return 1;
1294     if (multiplexer->nsc_command) return 1;
1295     if (multiplexer->fcon & 0x80) return 1;
1296     switch (multiplexer->state){
1297         case RFCOMM_MULTIPLEXER_SEND_SABM_0:
1298         case RFCOMM_MULTIPLEXER_SEND_UA_0:
1299         case RFCOMM_MULTIPLEXER_SEND_UA_0_AND_DISC:
1300             return 1;
1301         case RFCOMM_MULTIPLEXER_OPEN:
1302             if (multiplexer->test_data_len) {
1303                 return 1;
1304             }
1305             break;
1306         default:
1307             break;
1308     }
1309     return 0;
1310 }
1311 
1312 static void rfcomm_multiplexer_state_machine(rfcomm_multiplexer_t * multiplexer, RFCOMM_MULTIPLEXER_EVENT event){
1313 
1314     if (event != MULT_EV_READY_TO_SEND) return;
1315 
1316     uint16_t l2cap_cid = multiplexer->l2cap_cid;
1317 
1318     // process stored DM responses
1319     if (multiplexer->send_dm_for_dlci){
1320         uint8_t dlci = multiplexer->send_dm_for_dlci;
1321         multiplexer->send_dm_for_dlci = 0;
1322         rfcomm_send_dm_pf(multiplexer, dlci);
1323         return;
1324     }
1325 
1326     if (multiplexer->nsc_command){
1327         uint8_t command = multiplexer->nsc_command;
1328         multiplexer->nsc_command = 0;
1329         rfcomm_send_uih_nsc_rsp(multiplexer, command);
1330         return;
1331     }
1332 
1333     if (multiplexer->fcon & 0x80){
1334         multiplexer->fcon &= 0x01;
1335         rfcomm_send_uih_fc_rsp(multiplexer, multiplexer->fcon);
1336 
1337         if (multiplexer->fcon == 0) return;
1338         // trigger client to send again after sending FCon Response
1339         rfcomm_notify_channel_can_send();
1340         return;
1341     }
1342 
1343     switch (multiplexer->state) {
1344         case RFCOMM_MULTIPLEXER_SEND_SABM_0:
1345             log_info("Sending SABM #0 - (multi 0x%p)", multiplexer);
1346             multiplexer->state = RFCOMM_MULTIPLEXER_W4_UA_0;
1347             rfcomm_send_sabm(multiplexer, 0);
1348             break;
1349         case RFCOMM_MULTIPLEXER_SEND_UA_0:
1350             log_info("Sending UA #0");
1351             multiplexer->state = RFCOMM_MULTIPLEXER_OPEN;
1352             rfcomm_send_ua(multiplexer, 0);
1353 
1354             rfcomm_multiplexer_opened(multiplexer);
1355             break;
1356         case RFCOMM_MULTIPLEXER_SEND_UA_0_AND_DISC:
1357             log_info("Sending UA #0");
1358             log_info("Closing down multiplexer");
1359             multiplexer->state = RFCOMM_MULTIPLEXER_CLOSED;
1360             rfcomm_send_ua(multiplexer, 0);
1361 
1362             rfcomm_multiplexer_finalize(multiplexer);
1363             l2cap_disconnect(l2cap_cid, 0x13);
1364             break;
1365         case RFCOMM_MULTIPLEXER_OPEN:
1366             // respond to test command
1367             if (multiplexer->test_data_len){
1368                 int len = multiplexer->test_data_len;
1369                 log_info("Sending TEST Response with %u bytes", len);
1370                 multiplexer->test_data_len = 0;
1371                 rfcomm_send_uih_test_rsp(multiplexer, multiplexer->test_data, len);
1372                 return;
1373             }
1374             break;
1375         default:
1376             break;
1377     }
1378 }
1379 
1380 // MARK: RFCOMM CHANNEL
1381 
1382 static void rfcomm_channel_send_credits(rfcomm_channel_t *channel, uint8_t credits){
1383     channel->credits_incoming += credits;
1384     rfcomm_send_uih_credits(channel->multiplexer, channel->dlci, credits);
1385 }
1386 
1387 static int rfcomm_channel_can_send(rfcomm_channel_t * channel){
1388     if (!channel->credits_outgoing) return 0;
1389     if ((channel->multiplexer->fcon & 1) == 0) return 0;
1390     return l2cap_can_send_packet_now(channel->multiplexer->l2cap_cid);
1391 }
1392 
1393 static void rfcomm_channel_opened(rfcomm_channel_t *rfChannel){
1394 
1395     log_info("rfcomm_channel_opened!");
1396 
1397     rfChannel->state = RFCOMM_CHANNEL_OPEN;
1398     rfcomm_emit_channel_opened(rfChannel, 0);
1399     rfcomm_emit_port_configuration(rfChannel);
1400 
1401     // remove (potential) timer
1402     rfcomm_multiplexer_t *multiplexer = rfChannel->multiplexer;
1403     if (multiplexer->timer_active) {
1404         btstack_run_loop_remove_timer(&multiplexer->timer);
1405         multiplexer->timer_active = 0;
1406     }
1407     // hack for problem detecting authentication failure
1408     multiplexer->at_least_one_connection = 1;
1409 
1410     // request can send now if channel ready
1411     if (rfcomm_channel_ready_to_send(rfChannel)){
1412         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1413     }
1414 }
1415 
1416 static void rfcomm_channel_packet_handler_uih(rfcomm_multiplexer_t *multiplexer, uint8_t * packet, uint16_t size){
1417     const uint8_t frame_dlci = packet[0] >> 2;
1418     const uint8_t length_offset = (packet[2] & 1) ^ 1;  // to be used for pos >= 3
1419     const uint8_t credit_offset = ((packet[1] & BT_RFCOMM_UIH_PF) == BT_RFCOMM_UIH_PF) ? 1 : 0;   // credits for uih_pf frames
1420     const uint8_t payload_offset = 3 + length_offset + credit_offset;
1421     int request_can_send_now = 0;
1422 
1423     rfcomm_channel_t * channel = rfcomm_channel_for_multiplexer_and_dlci(multiplexer, frame_dlci);
1424     if (!channel) return;
1425 
1426     // handle new outgoing credits
1427     if (packet[1] == BT_RFCOMM_UIH_PF) {
1428 
1429         // add them
1430         uint16_t new_credits = packet[3+length_offset];
1431         channel->credits_outgoing += new_credits;
1432         log_info( "RFCOMM data UIH_PF, new credits channel 0x%02x: %u, now %u", channel->rfcomm_cid, new_credits, channel->credits_outgoing);
1433 
1434         // notify channel statemachine
1435         rfcomm_channel_event_t channel_event = { CH_EVT_RCVD_CREDITS, 0 };
1436         log_debug("rfcomm_channel_state_machine_with_channel, waiting_for_can_send_now %u", channel->waiting_for_can_send_now);
1437         int rfcomm_channel_valid = 1;
1438         rfcomm_channel_state_machine_with_channel(channel, &channel_event, &rfcomm_channel_valid);
1439         if (rfcomm_channel_valid){
1440             if (rfcomm_channel_ready_to_send(channel) || channel->waiting_for_can_send_now){
1441                 request_can_send_now = 1;
1442             }
1443         }
1444     }
1445 
1446     // contains payload?
1447     if ((size - 1) > payload_offset){
1448 
1449         // log_info( "RFCOMM data UIH_PF, size %u, channel %p", size-payload_offset-1, rfChannel->connection);
1450 
1451         // decrease incoming credit counter
1452         if (channel->credits_incoming > 0){
1453             channel->credits_incoming--;
1454         }
1455 
1456         // deliver payload
1457         (channel->packet_handler)(RFCOMM_DATA_PACKET, channel->rfcomm_cid,
1458                               &packet[payload_offset], size-payload_offset-1);
1459     }
1460 
1461     // automatically provide new credits to remote device, if no incoming flow control
1462     if (!channel->incoming_flow_control && (channel->credits_incoming < 5)){
1463         channel->new_credits_incoming = RFCOMM_CREDITS;
1464         request_can_send_now = 1;
1465     }
1466 
1467     if (request_can_send_now){
1468         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1469     }
1470 }
1471 
1472 static void rfcomm_channel_accept_pn(rfcomm_channel_t *channel, rfcomm_channel_event_pn_t *event){
1473     // priority of client request
1474     channel->pn_priority = event->priority;
1475 
1476     // new credits
1477     channel->credits_outgoing = event->credits_outgoing;
1478 
1479     // negotiate max frame size
1480     if (channel->max_frame_size > channel->multiplexer->max_frame_size) {
1481         channel->max_frame_size = channel->multiplexer->max_frame_size;
1482     }
1483     if (channel->max_frame_size > event->max_frame_size) {
1484         channel->max_frame_size = event->max_frame_size;
1485     }
1486 
1487 }
1488 
1489 static void rfcomm_channel_finalize(rfcomm_channel_t *channel){
1490 
1491     rfcomm_multiplexer_t *multiplexer = channel->multiplexer;
1492 
1493     // remove from list
1494     btstack_linked_list_remove( &rfcomm_channels, (btstack_linked_item_t *) channel);
1495 
1496     // free channel
1497     btstack_memory_rfcomm_channel_free(channel);
1498 
1499     // update multiplexer timeout after channel was removed from list
1500     rfcomm_multiplexer_prepare_idle_timer(multiplexer);
1501 }
1502 
1503 static void rfcomm_channel_state_machine_with_dlci(rfcomm_multiplexer_t * multiplexer, uint8_t dlci, const rfcomm_channel_event_t *event){
1504 
1505     // TODO: if client max frame size is smaller than RFCOMM_DEFAULT_SIZE, send PN
1506 
1507 
1508     // lookup existing channel
1509     rfcomm_channel_t * channel = rfcomm_channel_for_multiplexer_and_dlci(multiplexer, dlci);
1510 
1511     // log_info("rfcomm_channel_state_machine_with_dlci lookup dlci #%u = 0x%08x - event %u", dlci, (int) channel, event->type);
1512 
1513     if (channel) {
1514         int rfcomm_channel_valid = 1;
1515         rfcomm_channel_state_machine_with_channel(channel, event, &rfcomm_channel_valid);
1516         if (rfcomm_channel_valid && rfcomm_channel_ready_to_send(channel)){
1517             l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1518         }
1519         return;
1520     }
1521 
1522     // service registered?
1523     rfcomm_service_t * service = rfcomm_service_for_channel(dlci >> 1);
1524     // log_info("rfcomm_channel_state_machine_with_dlci service dlci #%u = 0x%08x", dlci, (int) service);
1525     if (!service) {
1526         // discard request by sending disconnected mode
1527         multiplexer->send_dm_for_dlci = dlci;
1528         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1529         return;
1530     }
1531 
1532     // create channel for some events
1533     switch (event->type) {
1534         case CH_EVT_RCVD_SABM:
1535         case CH_EVT_RCVD_PN:
1536         case CH_EVT_RCVD_RPN_REQ:
1537         case CH_EVT_RCVD_RPN_CMD:
1538             // setup incoming channel
1539             channel = rfcomm_channel_create(multiplexer, service, dlci >> 1);
1540             if (!channel){
1541                 // discard request by sending disconnected mode
1542                 multiplexer->send_dm_for_dlci = dlci;
1543                 l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1544             }
1545             break;
1546         default:
1547             break;
1548     }
1549 
1550     if (!channel) {
1551         // discard request by sending disconnected mode
1552         multiplexer->send_dm_for_dlci = dlci;
1553         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1554         return;
1555     }
1556 
1557     int rfcomm_channel_valid = 1;
1558     rfcomm_channel_state_machine_with_channel(channel, event, &rfcomm_channel_valid);
1559     if (rfcomm_channel_valid && rfcomm_channel_ready_to_send(channel)){
1560         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1561     }
1562 }
1563 
1564 static void rfcomm_channel_packet_handler(rfcomm_multiplexer_t * multiplexer,  uint8_t *packet, uint16_t size){
1565 
1566     UNUSED(size);   // ok: fixed format messages
1567 
1568     // rfcomm: (0) addr [76543 server channel] [2 direction: initiator uses 1] [1 C/R: CMD by initiator = 1] [0 EA=1]
1569     const uint8_t frame_dlci = packet[0] >> 2;
1570     uint8_t message_dlci; // used by commands in UIH(_PF) packets
1571 	uint8_t message_len;  //   "
1572 
1573     // rfcomm: (1) command/control
1574     // -- credits_offset = 1 if command == BT_RFCOMM_UIH_PF
1575     const uint8_t credit_offset = ((packet[1] & BT_RFCOMM_UIH_PF) == BT_RFCOMM_UIH_PF) ? 1 : 0;   // credits for uih_pf frames
1576     // rfcomm: (2) length. if bit 0 is cleared, 2 byte length is used. (little endian)
1577     const uint8_t length_offset = (packet[2] & 1) ^ 1;  // to be used for pos >= 3
1578     // rfcomm: (3+length_offset) credits if credits_offset == 1
1579     // rfcomm: (3+length_offest+credits_offset)
1580     const uint8_t payload_offset = 3 + length_offset + credit_offset;
1581 
1582     rfcomm_channel_event_t event;
1583     rfcomm_channel_event_pn_t event_pn;
1584     rfcomm_channel_event_rpn_t event_rpn;
1585     rfcomm_channel_event_msc_t event_msc;
1586 
1587     // switch by rfcomm message type
1588     switch(packet[1]) {
1589 
1590         case BT_RFCOMM_SABM:
1591             event.type = CH_EVT_RCVD_SABM;
1592             log_info("Received SABM #%u", frame_dlci);
1593             rfcomm_channel_state_machine_with_dlci(multiplexer, frame_dlci, &event);
1594             break;
1595 
1596         case BT_RFCOMM_UA:
1597             event.type = CH_EVT_RCVD_UA;
1598             log_info("Received UA #%u",frame_dlci);
1599             rfcomm_channel_state_machine_with_dlci(multiplexer, frame_dlci, &event);
1600             break;
1601 
1602         case BT_RFCOMM_DISC:
1603             event.type = CH_EVT_RCVD_DISC;
1604             rfcomm_channel_state_machine_with_dlci(multiplexer, frame_dlci, &event);
1605             break;
1606 
1607         case BT_RFCOMM_DM:
1608         case BT_RFCOMM_DM_PF:
1609             event.type = CH_EVT_RCVD_DM;
1610             rfcomm_channel_state_machine_with_dlci(multiplexer, frame_dlci, &event);
1611             break;
1612 
1613         case BT_RFCOMM_UIH_PF:
1614         case BT_RFCOMM_UIH:
1615 
1616             message_len  = packet[payload_offset+1] >> 1;
1617 
1618             switch (packet[payload_offset]) {
1619                 case BT_RFCOMM_PN_CMD:
1620                     message_dlci = packet[payload_offset+2];
1621                     event_pn.super.type = CH_EVT_RCVD_PN;
1622                     event_pn.priority = packet[payload_offset+4];
1623                     event_pn.max_frame_size = little_endian_read_16(packet, payload_offset+6);
1624                     event_pn.credits_outgoing = packet[payload_offset+9];
1625                     log_info("Received UIH Parameter Negotiation Command for #%u, credits %u",
1626                         message_dlci, event_pn.credits_outgoing);
1627                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_pn);
1628                     break;
1629 
1630                 case BT_RFCOMM_PN_RSP:
1631                     message_dlci = packet[payload_offset+2];
1632                     event_pn.super.type = CH_EVT_RCVD_PN_RSP;
1633                     event_pn.priority = packet[payload_offset+4];
1634                     event_pn.max_frame_size = little_endian_read_16(packet, payload_offset+6);
1635                     event_pn.credits_outgoing = packet[payload_offset+9];
1636                     log_info("Received UIH Parameter Negotiation Response max frame %u, credits %u",
1637                             event_pn.max_frame_size, event_pn.credits_outgoing);
1638                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_pn);
1639                     break;
1640 
1641                 case BT_RFCOMM_MSC_CMD:
1642                     message_dlci = packet[payload_offset+2] >> 2;
1643                     event_msc.super.type = CH_EVT_RCVD_MSC_CMD;
1644                     event_msc.modem_status = packet[payload_offset+3];
1645                     log_info("Received MSC CMD for #%u, ", message_dlci);
1646                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_msc);
1647                     break;
1648 
1649                 case BT_RFCOMM_MSC_RSP:
1650                     message_dlci = packet[payload_offset+2] >> 2;
1651                     event.type = CH_EVT_RCVD_MSC_RSP;
1652                     log_info("Received MSC RSP for #%u", message_dlci);
1653                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, &event);
1654                     break;
1655 
1656                 case BT_RFCOMM_RPN_CMD:
1657                     message_dlci = packet[payload_offset+2] >> 2;
1658                     switch (message_len){
1659                         case 1:
1660                             log_info("Received Remote Port Negotiation Request for #%u", message_dlci);
1661                             event.type = CH_EVT_RCVD_RPN_REQ;
1662                             rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, &event);
1663                             break;
1664                         case 8:
1665                             log_info("Received Remote Port Negotiation Update for #%u", message_dlci);
1666                             event_rpn.super.type = CH_EVT_RCVD_RPN_CMD;
1667                             event_rpn.data = *(rfcomm_rpn_data_t*) &packet[payload_offset+3];
1668                             rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_rpn);
1669                             break;
1670                         default:
1671                             break;
1672                     }
1673                     break;
1674 
1675                 case BT_RFCOMM_RPN_RSP:
1676                     log_info("Received RPN response");
1677                     break;
1678 
1679                 case BT_RFCOMM_RLS_CMD: {
1680                     log_info("Received RLS command");
1681                     message_dlci = packet[payload_offset+2] >> 2;
1682                     rfcomm_channel_event_rls_t event_rls;
1683                     event_rls.super.type = CH_EVT_RCVD_RLS_CMD;
1684                     event_rls.line_status = packet[payload_offset+3];
1685                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_rls);
1686                     break;
1687                 }
1688 
1689                 case BT_RFCOMM_RLS_RSP:
1690                     log_info("Received RLS response");
1691                     break;
1692 
1693                 // Following commands are handled by rfcomm_multiplexer_l2cap_packet_handler
1694                 // case BT_RFCOMM_TEST_CMD:
1695                 // case BT_RFCOMM_FCOFF_CMD:
1696                 // case BT_RFCOMM_FCON_CMD:
1697                 // everything else is an not supported command
1698                 default: {
1699                     log_error("Received unknown UIH command packet - 0x%02x", packet[payload_offset]);
1700                     multiplexer->nsc_command = packet[payload_offset];
1701                     break;
1702                 }
1703             }
1704             break;
1705 
1706         default:
1707             log_error("Received unknown RFCOMM message type %x", packet[1]);
1708             break;
1709     }
1710 
1711     // trigger next action - example W4_PN_RSP: transition to SEND_SABM which only depends on "can send"
1712     if (rfcomm_multiplexer_ready_to_send(multiplexer)){
1713         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1714     }
1715 }
1716 
1717 static void rfcomm_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
1718 
1719     if (packet_type == HCI_EVENT_PACKET){
1720         rfcomm_hci_event_handler(packet, size);
1721         return;
1722     }
1723 
1724     // we only handle l2cap packets for:
1725     if (packet_type != L2CAP_DATA_PACKET) return;
1726 
1727     //  - multiplexer itself
1728     int handled = rfcomm_multiplexer_l2cap_packet_handler(channel, packet, size);
1729 
1730     if (handled) return;
1731 
1732     // - channel over open mutliplexer
1733     rfcomm_multiplexer_t * multiplexer = rfcomm_multiplexer_for_l2cap_cid(channel);
1734     if ( (multiplexer == NULL) || (multiplexer->state != RFCOMM_MULTIPLEXER_OPEN)) return;
1735 
1736     // channel data ?
1737     // rfcomm: (0) addr [76543 server channel] [2 direction: initiator uses 1] [1 C/R: CMD by initiator = 1] [0 EA=1]
1738     const uint8_t frame_dlci = packet[0] >> 2;
1739 
1740     if (frame_dlci && ((packet[1] == BT_RFCOMM_UIH) || (packet[1] == BT_RFCOMM_UIH_PF))) {
1741         rfcomm_channel_packet_handler_uih(multiplexer, packet, size);
1742         return;
1743     }
1744 
1745     rfcomm_channel_packet_handler(multiplexer, packet, size);
1746 }
1747 
1748 static int rfcomm_channel_ready_for_open(rfcomm_channel_t *channel){
1749     // note: exchanging MSC isn't neccessary to consider channel open
1750     // note: having outgoing credits is also not necessary to consider channel open
1751     // 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);
1752     // if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SENT_MSC_RSP) == 0) return 0;
1753     // if (channel->credits_outgoing == 0) return 0;
1754     log_info("rfcomm_channel_ready_for_open state %u, flags needed %04x, current %04x, rf credits %u",
1755          channel->state, RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_RSP, channel->state_var, channel->credits_outgoing);
1756     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_RSP) == 0) return 0;
1757     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SENT_CREDITS) == 0) return 0;
1758 
1759     return 1;
1760 }
1761 
1762 static int rfcomm_channel_ready_for_incoming_dlc_setup(rfcomm_channel_t * channel){
1763     log_info("rfcomm_channel_ready_for_incoming_dlc_setup state var %04x", channel->state_var);
1764     // Client accept and SABM/UA is required, PN RSP is needed if PN was received
1765     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_CLIENT_ACCEPTED) == 0) return 0;
1766     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_SABM      ) == 0) return 0;
1767     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_UA        ) != 0) return 0;
1768     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP    ) != 0) return 0;
1769     return 1;
1770 }
1771 
1772 inline static void rfcomm_channel_state_add(rfcomm_channel_t *channel, RFCOMM_CHANNEL_STATE_VAR event){
1773     channel->state_var = (RFCOMM_CHANNEL_STATE_VAR) (channel->state_var | event);
1774 }
1775 inline static void rfcomm_channel_state_remove(rfcomm_channel_t *channel, RFCOMM_CHANNEL_STATE_VAR event){
1776     channel->state_var = (RFCOMM_CHANNEL_STATE_VAR) (channel->state_var & ~event);
1777 }
1778 
1779 static int rfcomm_channel_ready_to_send(rfcomm_channel_t * channel){
1780     switch (channel->state){
1781         case RFCOMM_CHANNEL_SEND_UIH_PN:
1782             log_debug("ch-ready: state %u", channel->state);
1783             return 1;
1784         case RFCOMM_CHANNEL_SEND_SABM_W4_UA:
1785             log_debug("ch-ready: state %u", channel->state);
1786             return 1;
1787         case RFCOMM_CHANNEL_SEND_UA_AFTER_DISC:
1788             log_debug("ch-ready: state %u", channel->state);
1789             return 1;
1790         case RFCOMM_CHANNEL_SEND_DISC:
1791             log_debug("ch-ready: state %u", channel->state);
1792             return 1;
1793         case RFCOMM_CHANNEL_SEND_DM:
1794             log_debug("ch-ready: state %u", channel->state);
1795             return 1;
1796         case RFCOMM_CHANNEL_OPEN:
1797             if (channel->new_credits_incoming) {
1798                 log_debug("ch-ready: channel open & new_credits_incoming") ;
1799                 return 1;
1800             }
1801             break;
1802         case RFCOMM_CHANNEL_DLC_SETUP:
1803             if (channel->state_var & (
1804                 RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD  |
1805                 RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS
1806              )) {
1807                 log_debug("ch-ready: channel dlc setup & send msc cmd or send credits") ;
1808                 return 1;
1809             }
1810             break;
1811 
1812         default:
1813             break;
1814     }
1815 
1816     if (channel->state_var & (
1817         RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP   |
1818         RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_INFO |
1819         RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RSP  |
1820         RFCOMM_CHANNEL_STATE_VAR_SEND_UA       |
1821         RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP
1822                              )){
1823         log_debug("ch-ready: state %x, state var %x", channel->state, channel->state_var);
1824         return 1;
1825     }
1826 
1827     if (channel->rls_line_status != RFCOMM_RLS_STATUS_INVALID) {
1828         log_debug("ch-ready: rls_line_status");
1829         return 1;
1830     }
1831 
1832     return 0;
1833 }
1834 
1835 
1836 static void rfcomm_channel_state_machine_with_channel(rfcomm_channel_t *channel, const rfcomm_channel_event_t *event, int * out_channel_valid){
1837 
1838     // log_info("rfcomm_channel_state_machine_with_channel: state %u, state_var %04x, event %u", channel->state, channel->state_var ,event->type);
1839 
1840     // channel != NULL -> channel valid
1841     *out_channel_valid = 1;
1842 
1843     rfcomm_multiplexer_t *multiplexer = channel->multiplexer;
1844 
1845     // TODO: integrate in common switch
1846     if (event->type == CH_EVT_RCVD_DISC){
1847         rfcomm_emit_channel_closed(channel);
1848         channel->state = RFCOMM_CHANNEL_SEND_UA_AFTER_DISC;
1849         return;
1850     }
1851 
1852     // TODO: integrate in common switch
1853     if (event->type == CH_EVT_RCVD_DM){
1854         log_info("Received DM message for #%u", channel->dlci);
1855         log_info("-> Closing channel locally for #%u", channel->dlci);
1856         rfcomm_channel_emit_final_event(channel, ERROR_CODE_CONNECTION_REJECTED_DUE_TO_LIMITED_RESOURCES);
1857         rfcomm_channel_finalize(channel);
1858         *out_channel_valid = 0;
1859         return;
1860     }
1861 
1862     // remote port negotiation command - just accept everything for now
1863     //
1864     // "The RPN command can be used before a new DLC is opened and should be used whenever the port settings change."
1865     // "The RPN command is specified as optional in TS 07.10, but it is mandatory to recognize and respond to it in RFCOMM.
1866     //   (Although the handling of individual settings are implementation-dependent.)"
1867     //
1868 
1869     // TODO: integrate in common switch
1870     if (event->type == CH_EVT_RCVD_RPN_CMD){
1871         // control port parameters
1872         rfcomm_channel_event_rpn_t *event_rpn = (rfcomm_channel_event_rpn_t*) event;
1873         rfcomm_rpn_data_update(&channel->rpn_data, &event_rpn->data);
1874         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RSP);
1875         // notify client about new settings
1876         rfcomm_emit_port_configuration(channel);
1877         return;
1878     }
1879 
1880     // TODO: integrate in common switch
1881     if (event->type == CH_EVT_RCVD_RPN_REQ){
1882         // no values got accepted (no values have beens sent)
1883         channel->rpn_data.parameter_mask_0 = 0x00;
1884         channel->rpn_data.parameter_mask_1 = 0x00;
1885         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RSP);
1886         return;
1887     }
1888 
1889     if (event->type == CH_EVT_RCVD_RLS_CMD){
1890         rfcomm_channel_event_rls_t * event_rls = (rfcomm_channel_event_rls_t*) event;
1891         channel->rls_line_status = event_rls->line_status & 0x0f;
1892         log_info("CH_EVT_RCVD_RLS_CMD setting line status to 0x%0x", channel->rls_line_status);
1893         rfcomm_emit_remote_line_status(channel, event_rls->line_status);
1894         return;
1895     }
1896 
1897     // TODO: integrate in common switch
1898     if (event->type == CH_EVT_READY_TO_SEND){
1899         if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RSP){
1900             log_info("Sending Remote Port Negotiation RSP for #%u", channel->dlci);
1901             rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RSP);
1902             rfcomm_send_uih_rpn_rsp(multiplexer, channel->dlci, &channel->rpn_data);
1903             return;
1904         }
1905         if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP){
1906             log_info("Sending MSC RSP for #%u", channel->dlci);
1907             rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP);
1908             rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SENT_MSC_RSP);
1909             rfcomm_send_uih_msc_rsp(multiplexer, channel->dlci, 0x8d);  // ea=1,fc=0,rtc=1,rtr=1,ic=0,dv=1
1910             return;
1911         }
1912         if (channel->rls_line_status != RFCOMM_RLS_STATUS_INVALID){
1913             log_info("Sending RLS RSP 0x%0x", channel->rls_line_status);
1914             uint8_t line_status = channel->rls_line_status;
1915             channel->rls_line_status = RFCOMM_RLS_STATUS_INVALID;
1916             rfcomm_send_uih_rls_rsp(multiplexer, channel->dlci, line_status);
1917             return;
1918         }
1919     }
1920 
1921     // emit MSC status to app
1922     if (event->type == CH_EVT_RCVD_MSC_CMD){
1923         // notify client about new settings
1924         rfcomm_channel_event_msc_t *event_msc = (rfcomm_channel_event_msc_t*) event;
1925         uint8_t modem_status_event[2+1];
1926         modem_status_event[0] = RFCOMM_EVENT_REMOTE_MODEM_STATUS;
1927         modem_status_event[1] = 1;
1928         modem_status_event[2] = event_msc->modem_status;
1929         (channel->packet_handler)(HCI_EVENT_PACKET, channel->rfcomm_cid, (uint8_t*)&modem_status_event, sizeof(modem_status_event));
1930         // no return, MSC_CMD will be handled by state machine below
1931     }
1932 
1933     rfcomm_channel_event_pn_t * event_pn = (rfcomm_channel_event_pn_t*) event;
1934 
1935     switch (channel->state) {
1936         case RFCOMM_CHANNEL_CLOSED:
1937             switch (event->type){
1938                 case CH_EVT_RCVD_SABM:
1939                     log_info("-> Inform app");
1940                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_SABM);
1941                     channel->state = RFCOMM_CHANNEL_INCOMING_SETUP;
1942                     rfcomm_emit_connection_request(channel);
1943                     break;
1944                 case CH_EVT_RCVD_PN:
1945                     rfcomm_channel_accept_pn(channel, event_pn);
1946                     log_info("-> Inform app");
1947                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_PN);
1948                     channel->state = RFCOMM_CHANNEL_INCOMING_SETUP;
1949                     rfcomm_emit_connection_request(channel);
1950                     break;
1951                 default:
1952                     break;
1953             }
1954             break;
1955 
1956         case RFCOMM_CHANNEL_INCOMING_SETUP:
1957             switch (event->type){
1958                 case CH_EVT_RCVD_SABM:
1959                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_SABM);
1960                     if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_CLIENT_ACCEPTED) {
1961                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_UA);
1962                     }
1963                     break;
1964                 case CH_EVT_RCVD_PN:
1965                     rfcomm_channel_accept_pn(channel, event_pn);
1966                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_PN);
1967                     if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_CLIENT_ACCEPTED) {
1968                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP);
1969                     }
1970                     break;
1971                 case CH_EVT_READY_TO_SEND:
1972                     // if / else if is used to check for state transition after sending
1973                     if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP){
1974                         log_info("Sending UIH Parameter Negotiation Respond for #%u", channel->dlci);
1975                         rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP);
1976                         rfcomm_send_uih_pn_response(multiplexer, channel->dlci, channel->pn_priority, channel->max_frame_size);
1977                     } else if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_UA){
1978                         log_info("Sending UA #%u", channel->dlci);
1979                         rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_UA);
1980                         rfcomm_send_ua(multiplexer, channel->dlci);
1981                     }
1982                     if (rfcomm_channel_ready_for_incoming_dlc_setup(channel)){
1983                         log_info("Incomping setup done, requesting send MSC CMD and send Credits");
1984                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD);
1985                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS);
1986                         channel->state = RFCOMM_CHANNEL_DLC_SETUP;
1987                      }
1988                     break;
1989                 default:
1990                     break;
1991             }
1992             break;
1993 
1994         case RFCOMM_CHANNEL_W4_MULTIPLEXER:
1995             switch (event->type) {
1996                 case CH_EVT_MULTIPLEXER_READY:
1997                     log_info("Muliplexer opened, sending UIH PN next");
1998                     channel->state = RFCOMM_CHANNEL_SEND_UIH_PN;
1999                     break;
2000                 default:
2001                     break;
2002             }
2003             break;
2004 
2005         case RFCOMM_CHANNEL_SEND_UIH_PN:
2006             switch (event->type) {
2007                 case CH_EVT_READY_TO_SEND:
2008                     // update mtu
2009                     channel->max_frame_size = btstack_min(multiplexer->max_frame_size, channel->max_frame_size);
2010                     log_info("Sending UIH Parameter Negotiation Command for #%u (channel 0x%p) mtu %u", channel->dlci, channel, channel->max_frame_size );
2011                     channel->state = RFCOMM_CHANNEL_W4_PN_RSP;
2012                     rfcomm_send_uih_pn_command(multiplexer, channel->dlci, channel->max_frame_size);
2013                     break;
2014                 default:
2015                     break;
2016             }
2017             break;
2018 
2019         case RFCOMM_CHANNEL_W4_PN_RSP:
2020             switch (event->type){
2021                 case CH_EVT_RCVD_PN_RSP:
2022                     // update max frame size
2023                     if (channel->max_frame_size > event_pn->max_frame_size) {
2024                         channel->max_frame_size = event_pn->max_frame_size;
2025                     }
2026                     // new credits
2027                     channel->credits_outgoing = event_pn->credits_outgoing;
2028                     channel->state = RFCOMM_CHANNEL_SEND_SABM_W4_UA;
2029                     break;
2030                 default:
2031                     break;
2032             }
2033             break;
2034 
2035         case RFCOMM_CHANNEL_SEND_SABM_W4_UA:
2036             switch (event->type) {
2037                 case CH_EVT_READY_TO_SEND:
2038                     log_info("Sending SABM #%u", channel->dlci);
2039                     channel->state = RFCOMM_CHANNEL_W4_UA;
2040                     rfcomm_send_sabm(multiplexer, channel->dlci);
2041                     break;
2042                 default:
2043                     break;
2044             }
2045             break;
2046 
2047         case RFCOMM_CHANNEL_W4_UA:
2048             switch (event->type){
2049                 case CH_EVT_RCVD_UA:
2050                     channel->state = RFCOMM_CHANNEL_DLC_SETUP;
2051                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD);
2052                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS);
2053                     break;
2054                 default:
2055                     break;
2056             }
2057             break;
2058 
2059         case RFCOMM_CHANNEL_DLC_SETUP:
2060             switch (event->type){
2061                 case CH_EVT_RCVD_MSC_CMD:
2062                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_CMD);
2063                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP);
2064                     break;
2065                 case CH_EVT_RCVD_MSC_RSP:
2066                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_RSP);
2067                     break;
2068 
2069                 case CH_EVT_READY_TO_SEND:
2070                     if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD){
2071                         log_info("Sending MSC CMD for #%u", channel->dlci);
2072                         rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD);
2073                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SENT_MSC_CMD);
2074                         rfcomm_send_uih_msc_cmd(multiplexer, channel->dlci , 0x8d);  // ea=1,fc=0,rtc=1,rtr=1,ic=0,dv=1
2075                         break;
2076                     }
2077                     if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS){
2078                         log_info("Providing credits for #%u", channel->dlci);
2079                         rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS);
2080                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SENT_CREDITS);
2081 
2082                         if (channel->new_credits_incoming) {
2083                             uint8_t new_credits = channel->new_credits_incoming;
2084                             channel->new_credits_incoming = 0;
2085                             rfcomm_channel_send_credits(channel, new_credits);
2086                         }
2087                         break;
2088 
2089                     }
2090                     break;
2091                 default:
2092                     break;
2093             }
2094             // finally done?
2095             if (rfcomm_channel_ready_for_open(channel)){
2096                 channel->state = RFCOMM_CHANNEL_OPEN;
2097                 rfcomm_channel_opened(channel);
2098             }
2099             break;
2100 
2101         case RFCOMM_CHANNEL_OPEN:
2102             switch (event->type){
2103                 case CH_EVT_RCVD_MSC_CMD:
2104                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP);
2105                     break;
2106                 case CH_EVT_READY_TO_SEND:
2107                     if (channel->new_credits_incoming) {
2108                         uint8_t new_credits = channel->new_credits_incoming;
2109                         channel->new_credits_incoming = 0;
2110                         rfcomm_channel_send_credits(channel, new_credits);
2111                         break;
2112                     }
2113                     break;
2114                 case CH_EVT_RCVD_CREDITS:
2115                     rfcomm_notify_channel_can_send();
2116                     break;
2117                 default:
2118                     break;
2119             }
2120             break;
2121 
2122         case RFCOMM_CHANNEL_SEND_DM:
2123             switch (event->type) {
2124                 case CH_EVT_READY_TO_SEND:
2125                     log_info("Sending DM_PF for #%u", channel->dlci);
2126                     // don't emit channel closed - channel was never open
2127                     channel->state = RFCOMM_CHANNEL_CLOSED;
2128                     rfcomm_send_dm_pf(multiplexer, channel->dlci);
2129                     rfcomm_channel_finalize(channel);
2130                     *out_channel_valid = 0;
2131                     break;
2132                 default:
2133                     break;
2134             }
2135             break;
2136 
2137         case RFCOMM_CHANNEL_SEND_DISC:
2138             switch (event->type) {
2139                 case CH_EVT_READY_TO_SEND:
2140                     channel->state = RFCOMM_CHANNEL_W4_UA_AFTER_DISC;
2141                     rfcomm_send_disc(multiplexer, channel->dlci);
2142                     break;
2143                 default:
2144                     break;
2145             }
2146             break;
2147 
2148         case RFCOMM_CHANNEL_W4_UA_AFTER_DISC:
2149             switch (event->type){
2150                 case CH_EVT_RCVD_UA:
2151                     channel->state = RFCOMM_CHANNEL_CLOSED;
2152                     rfcomm_emit_channel_closed(channel);
2153                     rfcomm_channel_finalize(channel);
2154                     *out_channel_valid = 0;
2155                     break;
2156                 default:
2157                     break;
2158             }
2159             break;
2160 
2161         case RFCOMM_CHANNEL_SEND_UA_AFTER_DISC:
2162             switch (event->type) {
2163                 case CH_EVT_READY_TO_SEND:
2164                     log_info("Sending UA after DISC for #%u", channel->dlci);
2165                     channel->state = RFCOMM_CHANNEL_CLOSED;
2166                     rfcomm_send_ua(multiplexer, channel->dlci);
2167                     rfcomm_channel_finalize(channel);
2168                     *out_channel_valid = 0;
2169                     break;
2170                 default:
2171                     break;
2172             }
2173             break;
2174 
2175         default:
2176             break;
2177     }
2178 }
2179 
2180 // MARK: RFCOMM BTstack API
2181 
2182 void rfcomm_init(void){
2183     rfcomm_client_cid_generator = 0;
2184     rfcomm_multiplexers = NULL;
2185     rfcomm_services     = NULL;
2186     rfcomm_channels     = NULL;
2187     rfcomm_security_level = gap_get_security_level();
2188 }
2189 
2190 void rfcomm_set_required_security_level(gap_security_level_t security_level){
2191     rfcomm_security_level = security_level;
2192 }
2193 
2194 int rfcomm_can_send_packet_now(uint16_t rfcomm_cid){
2195     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2196     if (!channel){
2197         log_error("rfcomm_send cid 0x%02x doesn't exist!", rfcomm_cid);
2198         return 0;
2199     }
2200     return rfcomm_channel_can_send(channel);
2201 }
2202 
2203 void rfcomm_request_can_send_now_event(uint16_t rfcomm_cid){
2204     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2205     if (!channel){
2206         log_error("rfcomm_send cid 0x%02x doesn't exist!", rfcomm_cid);
2207         return;
2208     }
2209     channel->waiting_for_can_send_now = 1;
2210     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2211 }
2212 
2213 static int rfcomm_assert_send_valid(rfcomm_channel_t * channel , uint16_t len){
2214     if (len > channel->max_frame_size){
2215         log_error("rfcomm_send cid 0x%02x, rfcomm data lenght exceeds MTU!", channel->rfcomm_cid);
2216         return RFCOMM_DATA_LEN_EXCEEDS_MTU;
2217     }
2218 
2219 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2220     if (len > rfcomm_max_frame_size_for_l2cap_mtu(sizeof(outgoing_buffer))){
2221         log_error("rfcomm_send cid 0x%02x, length exceeds outgoing rfcomm_out_buffer", channel->rfcomm_cid);
2222         return RFCOMM_DATA_LEN_EXCEEDS_MTU;
2223     }
2224 #endif
2225 
2226     if (!channel->credits_outgoing){
2227         log_info("rfcomm_send cid 0x%02x, no rfcomm outgoing credits!", channel->rfcomm_cid);
2228         return RFCOMM_NO_OUTGOING_CREDITS;
2229     }
2230 
2231     if ((channel->multiplexer->fcon & 1) == 0){
2232         log_info("rfcomm_send cid 0x%02x, aggregate flow off!", channel->rfcomm_cid);
2233         return RFCOMM_AGGREGATE_FLOW_OFF;
2234     }
2235     return 0;
2236 }
2237 
2238 uint16_t rfcomm_get_max_frame_size(uint16_t rfcomm_cid){
2239     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2240     if (!channel){
2241         log_error("rfcomm_get_max_frame_size cid 0x%02x doesn't exist!", rfcomm_cid);
2242         return 0;
2243     }
2244     return channel->max_frame_size;
2245 }
2246 
2247 // pre: rfcomm_can_send_packet_now(rfcomm_cid) == true
2248 int rfcomm_reserve_packet_buffer(void){
2249 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2250     log_error("rfcomm_reserve_packet_buffer should not get called with ERTM");
2251     return 0;
2252 #else
2253     return l2cap_reserve_packet_buffer();
2254 #endif
2255 }
2256 
2257 void rfcomm_release_packet_buffer(void){
2258 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2259     log_error("rfcomm_release_packet_buffer should not get called with ERTM");
2260 #else
2261     l2cap_release_packet_buffer();
2262 #endif
2263 }
2264 
2265 uint8_t * rfcomm_get_outgoing_buffer(void){
2266 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2267     uint8_t * rfcomm_out_buffer = outgoing_buffer;
2268 #else
2269     uint8_t * rfcomm_out_buffer = l2cap_get_outgoing_buffer();
2270 #endif
2271     // address + control + length (16) + no credit field
2272     return &rfcomm_out_buffer[4];
2273 }
2274 
2275 int rfcomm_send_prepared(uint16_t rfcomm_cid, uint16_t len){
2276     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2277     if (!channel){
2278         log_error("rfcomm_send_prepared cid 0x%02x doesn't exist!", rfcomm_cid);
2279         return 0;
2280     }
2281 
2282     int err = rfcomm_assert_send_valid(channel, len);
2283     if (err) return err;
2284 
2285 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2286     if (!l2cap_can_send_packet_now(channel->multiplexer->l2cap_cid)){
2287         log_error("rfcomm_send_prepared: l2cap cannot send now");
2288         return BTSTACK_ACL_BUFFERS_FULL;
2289     }
2290 #else
2291     if (!l2cap_can_send_prepared_packet_now(channel->multiplexer->l2cap_cid)){
2292         log_error("rfcomm_send_prepared: l2cap cannot send now");
2293         return BTSTACK_ACL_BUFFERS_FULL;
2294     }
2295 #endif
2296 
2297     // send might cause l2cap to emit new credits, update counters first
2298     if (len){
2299         channel->credits_outgoing--;
2300     } else {
2301         log_info("sending empty RFCOMM packet for cid %02x", rfcomm_cid);
2302     }
2303 
2304     int result = rfcomm_send_uih_prepared(channel->multiplexer, channel->dlci, len);
2305 
2306     if (result != 0) {
2307         if (len) {
2308             channel->credits_outgoing++;
2309         }
2310         log_error("rfcomm_send_prepared: error %d", result);
2311         return result;
2312     }
2313 
2314     return result;
2315 }
2316 
2317 int rfcomm_send(uint16_t rfcomm_cid, uint8_t *data, uint16_t len){
2318     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2319     if (!channel){
2320         log_error("cid 0x%02x doesn't exist!", rfcomm_cid);
2321         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
2322     }
2323 
2324     int err = rfcomm_assert_send_valid(channel, len);
2325     if (err) return err;
2326     if (!l2cap_can_send_packet_now(channel->multiplexer->l2cap_cid)){
2327         log_error("rfcomm_send_internal: l2cap cannot send now");
2328         return BTSTACK_ACL_BUFFERS_FULL;
2329     }
2330 
2331 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2332 #else
2333     rfcomm_reserve_packet_buffer();
2334 #endif
2335     uint8_t * rfcomm_payload = rfcomm_get_outgoing_buffer();
2336 
2337     (void)memcpy(rfcomm_payload, data, len);
2338     err = rfcomm_send_prepared(rfcomm_cid, len);
2339 
2340 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2341 #else
2342     if (err){
2343         rfcomm_release_packet_buffer();
2344     }
2345 #endif
2346 
2347     return err;
2348 }
2349 
2350 // Sends Local Lnie Status, see LINE_STATUS_..
2351 int rfcomm_send_local_line_status(uint16_t rfcomm_cid, uint8_t line_status){
2352     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2353     if (!channel){
2354         log_error("rfcomm_send_local_line_status cid 0x%02x doesn't exist!", rfcomm_cid);
2355         return 0;
2356     }
2357     return rfcomm_send_uih_rls_cmd(channel->multiplexer, channel->dlci, line_status);
2358 }
2359 
2360 // Sned local modem status. see MODEM_STAUS_..
2361 int rfcomm_send_modem_status(uint16_t rfcomm_cid, uint8_t modem_status){
2362     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2363     if (!channel){
2364         log_error("rfcomm_send_modem_status cid 0x%02x doesn't exist!", rfcomm_cid);
2365         return 0;
2366     }
2367     return rfcomm_send_uih_msc_cmd(channel->multiplexer, channel->dlci, modem_status);
2368 }
2369 
2370 // Configure remote port
2371 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){
2372     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2373     if (!channel){
2374         log_error("rfcomm_send_port_configuration cid 0x%02x doesn't exist!", rfcomm_cid);
2375         return 0;
2376     }
2377     rfcomm_rpn_data_t rpn_data;
2378     rpn_data.baud_rate = baud_rate;
2379     rpn_data.flags = data_bits | (stop_bits << 2) | (parity << 3);
2380     rpn_data.flow_control = flow_control;
2381     rpn_data.xon = 0;
2382     rpn_data.xoff = 0;
2383     rpn_data.parameter_mask_0 = 0x1f;   // all but xon/xoff
2384     rpn_data.parameter_mask_1 = 0x3f;   // all flow control options
2385     return rfcomm_send_uih_rpn_cmd(channel->multiplexer, channel->dlci, &rpn_data);
2386 }
2387 
2388 // Query remote port
2389 int rfcomm_query_port_configuration(uint16_t rfcomm_cid){
2390     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2391     if (!channel){
2392         log_error("rfcomm_query_port_configuration cid 0x%02x doesn't exist!", rfcomm_cid);
2393         return 0;
2394     }
2395     return rfcomm_send_uih_rpn_req(channel->multiplexer, channel->dlci);
2396 }
2397 
2398 
2399 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){
2400     log_info("RFCOMM_CREATE_CHANNEL addr %s channel #%u init credits %u",  bd_addr_to_str(addr), server_channel, initial_credits);
2401 
2402     // create new multiplexer if necessary
2403     uint8_t status = 0;
2404     uint8_t dlci = 0;
2405     int new_multiplexer = 0;
2406     rfcomm_channel_t * channel = NULL;
2407     rfcomm_multiplexer_t * multiplexer = rfcomm_multiplexer_for_addr(addr);
2408     if (!multiplexer) {
2409         multiplexer = rfcomm_multiplexer_create_for_addr(addr);
2410         if (!multiplexer) return BTSTACK_MEMORY_ALLOC_FAILED;
2411 
2412         multiplexer->outgoing = 1;
2413         multiplexer->state = RFCOMM_MULTIPLEXER_W4_CONNECT;
2414         new_multiplexer = 1;
2415     }
2416 
2417     // check if channel for this remote service already exists
2418     dlci = (server_channel << 1) | (multiplexer->outgoing ^ 1);
2419     channel = rfcomm_channel_for_multiplexer_and_dlci(multiplexer, dlci);
2420     if (channel){
2421         if (new_multiplexer) btstack_memory_rfcomm_multiplexer_free(multiplexer);
2422         return RFCOMM_CHANNEL_ALREADY_REGISTERED;
2423     }
2424 
2425     // prepare channel
2426     channel = rfcomm_channel_create(multiplexer, NULL, server_channel);
2427     if (!channel){
2428         if (new_multiplexer) btstack_memory_rfcomm_multiplexer_free(multiplexer);
2429         return BTSTACK_MEMORY_ALLOC_FAILED;
2430     }
2431 
2432     // rfcomm_cid is already assigned by rfcomm_channel_create
2433     channel->incoming_flow_control = incoming_flow_control;
2434     channel->new_credits_incoming  = initial_credits;
2435     channel->packet_handler = packet_handler;
2436 
2437     // return rfcomm_cid
2438     if (out_rfcomm_cid){
2439         *out_rfcomm_cid = channel->rfcomm_cid;
2440     }
2441 
2442     // start multiplexer setup
2443     if (multiplexer->state != RFCOMM_MULTIPLEXER_OPEN) {
2444         channel->state = RFCOMM_CHANNEL_W4_MULTIPLEXER;
2445         uint16_t l2cap_cid = 0;
2446 #ifdef RFCOMM_USE_ERTM
2447         // request
2448         rfcomm_ertm_request_t request;
2449         memset(&request, 0, sizeof(rfcomm_ertm_request_t));
2450         (void)memcpy(request.addr, addr, 6);
2451         request.ertm_id = rfcomm_next_ertm_id();
2452         if (rfcomm_ertm_request_callback){
2453             (*rfcomm_ertm_request_callback)(&request);
2454         }
2455         if (request.ertm_config && request.ertm_buffer && request.ertm_buffer_size){
2456             multiplexer->ertm_id = request.ertm_id;
2457             status = l2cap_create_ertm_channel(rfcomm_packet_handler, addr, BLUETOOTH_PROTOCOL_RFCOMM,
2458                         request.ertm_config, request.ertm_buffer, request.ertm_buffer_size, &l2cap_cid);
2459         }
2460         else
2461 #endif
2462         {
2463             status = l2cap_create_channel(rfcomm_packet_handler, addr, BLUETOOTH_PROTOCOL_RFCOMM, l2cap_max_mtu(), &l2cap_cid);
2464         }
2465         if (status) {
2466             if (new_multiplexer) btstack_memory_rfcomm_multiplexer_free(multiplexer);
2467             btstack_memory_rfcomm_channel_free(channel);
2468             return status;
2469         }
2470         multiplexer->l2cap_cid = l2cap_cid;
2471         return ERROR_CODE_SUCCESS;
2472     }
2473 
2474     channel->state = RFCOMM_CHANNEL_SEND_UIH_PN;
2475 
2476     // start connecting, if multiplexer is already up and running
2477     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
2478     return ERROR_CODE_SUCCESS;
2479 }
2480 
2481 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){
2482     return rfcomm_channel_create_internal(packet_handler, addr, server_channel, 1, initial_credits, out_rfcomm_cid);
2483 }
2484 
2485 uint8_t rfcomm_create_channel(btstack_packet_handler_t packet_handler, bd_addr_t addr, uint8_t server_channel, uint16_t * out_rfcomm_cid){
2486     return rfcomm_channel_create_internal(packet_handler, addr, server_channel, 0, RFCOMM_CREDITS, out_rfcomm_cid);
2487 }
2488 
2489 void rfcomm_disconnect(uint16_t rfcomm_cid){
2490     log_info("RFCOMM_DISCONNECT cid 0x%02x", rfcomm_cid);
2491     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2492     if (!channel) return;
2493 
2494     channel->state = RFCOMM_CHANNEL_SEND_DISC;
2495     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2496 }
2497 
2498 static uint8_t rfcomm_register_service_internal(btstack_packet_handler_t packet_handler,
2499     uint8_t channel, uint16_t max_frame_size, uint8_t incoming_flow_control, uint8_t initial_credits){
2500 
2501     log_info("RFCOMM_REGISTER_SERVICE channel #%u mtu %u flow_control %u credits %u",
2502              channel, max_frame_size, incoming_flow_control, initial_credits);
2503 
2504     // check if already registered
2505     rfcomm_service_t * service = rfcomm_service_for_channel(channel);
2506     if (service){
2507         return RFCOMM_CHANNEL_ALREADY_REGISTERED;
2508     }
2509 
2510     // alloc structure
2511     service = btstack_memory_rfcomm_service_get();
2512     if (!service) {
2513         return BTSTACK_MEMORY_ALLOC_FAILED;
2514     }
2515 
2516     // register with l2cap if not registered before, max MTU
2517     if (btstack_linked_list_empty(&rfcomm_services)){
2518         l2cap_register_service(rfcomm_packet_handler, BLUETOOTH_PROTOCOL_RFCOMM, 0xffff, rfcomm_security_level);
2519     }
2520 
2521     // fill in
2522     service->packet_handler = packet_handler;
2523     service->server_channel = channel;
2524     service->max_frame_size = max_frame_size;
2525     service->incoming_flow_control = incoming_flow_control;
2526     service->incoming_initial_credits = initial_credits;
2527 
2528     // add to services list
2529     btstack_linked_list_add(&rfcomm_services, (btstack_linked_item_t *) service);
2530 
2531     return 0;
2532 }
2533 
2534 uint8_t rfcomm_register_service_with_initial_credits(btstack_packet_handler_t packet_handler,
2535     uint8_t channel, uint16_t max_frame_size, uint8_t initial_credits){
2536 
2537     return rfcomm_register_service_internal(packet_handler, channel, max_frame_size, 1, initial_credits);
2538 }
2539 
2540 uint8_t rfcomm_register_service(btstack_packet_handler_t packet_handler, uint8_t channel,
2541     uint16_t max_frame_size){
2542 
2543     return rfcomm_register_service_internal(packet_handler, channel, max_frame_size, 0,RFCOMM_CREDITS);
2544 }
2545 
2546 void rfcomm_unregister_service(uint8_t service_channel){
2547     log_info("RFCOMM_UNREGISTER_SERVICE #%u", service_channel);
2548     rfcomm_service_t *service = rfcomm_service_for_channel(service_channel);
2549     if (!service) return;
2550     btstack_linked_list_remove(&rfcomm_services, (btstack_linked_item_t *) service);
2551     btstack_memory_rfcomm_service_free(service);
2552 
2553     // unregister if no services active
2554     if (btstack_linked_list_empty(&rfcomm_services)){
2555         // bt_send_cmd(&l2cap_unregister_service, BLUETOOTH_PROTOCOL_RFCOMM);
2556         l2cap_unregister_service(BLUETOOTH_PROTOCOL_RFCOMM);
2557     }
2558 }
2559 
2560 void rfcomm_accept_connection(uint16_t rfcomm_cid){
2561     log_info("RFCOMM_ACCEPT_CONNECTION cid 0x%02x", rfcomm_cid);
2562     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2563     if (!channel) return;
2564     switch (channel->state) {
2565         case RFCOMM_CHANNEL_INCOMING_SETUP:
2566             rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_CLIENT_ACCEPTED);
2567             if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_PN){
2568                 rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP);
2569                 l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2570             }
2571             if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_SABM){
2572                 rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_UA);
2573                 l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2574             }
2575             // at least one of { PN RSP, UA } needs to be sent
2576             // state transistion incoming setup -> dlc setup happens in rfcomm_run after these have been sent
2577             break;
2578         default:
2579             break;
2580     }
2581 
2582 }
2583 
2584 void rfcomm_decline_connection(uint16_t rfcomm_cid){
2585     log_info("RFCOMM_DECLINE_CONNECTION cid 0x%02x", rfcomm_cid);
2586     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2587     if (!channel) return;
2588     switch (channel->state) {
2589         case RFCOMM_CHANNEL_INCOMING_SETUP:
2590             channel->state = RFCOMM_CHANNEL_SEND_DM;
2591             l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2592             break;
2593         default:
2594             break;
2595     }
2596 }
2597 
2598 void rfcomm_grant_credits(uint16_t rfcomm_cid, uint8_t credits){
2599     log_info("RFCOMM_GRANT_CREDITS cid 0x%02x credits %u", rfcomm_cid, credits);
2600     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2601     if (!channel) return;
2602     if (!channel->incoming_flow_control) return;
2603     channel->new_credits_incoming += credits;
2604 
2605     // process
2606     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2607 }
2608 
2609 #ifdef RFCOMM_USE_ERTM
2610 void rfcomm_enable_l2cap_ertm(void request_callback(rfcomm_ertm_request_t * request), void released_callback(uint16_t ertm_id)){
2611     rfcomm_ertm_request_callback  = request_callback;
2612     rfcomm_ertm_released_callback = released_callback;
2613 }
2614 #endif
2615