xref: /btstack/src/classic/rfcomm.c (revision d58a1b5f11ada8ddf896c41fff5a35e7f140c37e)
1 /*
2  * Copyright (C) 2014 BlueKitchen GmbH
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the copyright holders nor the names of
14  *    contributors may be used to endorse or promote products derived
15  *    from this software without specific prior written permission.
16  * 4. Any redistribution, use, or modification is done solely for
17  *    personal benefit and not for any commercial purpose or for
18  *    monetary gain.
19  *
20  * THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
24  * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
26  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
27  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
30  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  *
33  * Please inquire about commercial licensing options at
34  * [email protected]
35  *
36  */
37 
38 #define BTSTACK_FILE__ "rfcomm.c"
39 
40 /*
41  *  rfcomm.c
42  */
43 
44 #include <stdio.h>
45 #include <stdlib.h>
46 #include <string.h> // memcpy
47 #include <stdint.h>
48 
49 #include "bluetooth_sdp.h"
50 #include "btstack_debug.h"
51 #include "btstack_event.h"
52 #include "btstack_memory.h"
53 #include "btstack_util.h"
54 #include "classic/core.h"
55 #include "classic/rfcomm.h"
56 #include "hci.h"
57 #include "hci_cmd.h"
58 #include "hci_dump.h"
59 #include "l2cap.h"
60 
61 // workaround for missing PRIxPTR on mspgcc (16/20-bit MCU)
62 #ifndef PRIxPTR
63 #if defined(__MSP430X__)  &&  defined(__MSP430X_LARGE__)
64 #define PRIxPTR "lx"
65 #else
66 #define PRIxPTR "x"
67 #endif
68 #endif
69 
70 // ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM requires ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE
71 #ifdef ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM
72 #ifdef ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE
73 #define RFCOMM_USE_OUTGOING_BUFFER
74 #define RFCOMM_USE_ERTM
75 #else
76 #error "ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM requires ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE. "
77 #error "Please disable ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM, or, "
78 #error "enable ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE"
79 #endif
80 #endif
81 
82 #define RFCOMM_MULIPLEXER_TIMEOUT_MS 60000
83 
84 #define RFCOMM_CREDITS 10
85 
86 // FCS calc
87 #define BT_RFCOMM_CODE_WORD         0xE0 // pol = x8+x2+x1+1
88 #define BT_RFCOMM_CRC_CHECK_LEN     3
89 #define BT_RFCOMM_UIHCRC_CHECK_LEN  2
90 
91 // Control field values      bit no.       1 2 3 4 PF 6 7 8
92 #define BT_RFCOMM_SABM       0x3F       // 1 1 1 1  1 1 0 0
93 #define BT_RFCOMM_UA         0x73       // 1 1 0 0  1 1 1 0
94 #define BT_RFCOMM_DM         0x0F       // 1 1 1 1  0 0 0 0
95 #define BT_RFCOMM_DM_PF      0x1F       // 1 1 1 1  1 0 0 0
96 #define BT_RFCOMM_DISC       0x53       // 1 1 0 0  1 0 1 0
97 #define BT_RFCOMM_UIH        0xEF       // 1 1 1 1  0 1 1 1
98 #define BT_RFCOMM_UIH_PF     0xFF       // 1 1 1 1  0 1 1 1
99 
100 // Multiplexer message types
101 #define BT_RFCOMM_CLD_CMD    0xC3
102 #define BT_RFCOMM_FCON_CMD   0xA3
103 #define BT_RFCOMM_FCON_RSP   0xA1
104 #define BT_RFCOMM_FCOFF_CMD  0x63
105 #define BT_RFCOMM_FCOFF_RSP  0x61
106 #define BT_RFCOMM_MSC_CMD    0xE3
107 #define BT_RFCOMM_MSC_RSP    0xE1
108 #define BT_RFCOMM_NSC_RSP    0x11
109 #define BT_RFCOMM_PN_CMD     0x83
110 #define BT_RFCOMM_PN_RSP     0x81
111 #define BT_RFCOMM_RLS_CMD    0x53
112 #define BT_RFCOMM_RLS_RSP    0x51
113 #define BT_RFCOMM_RPN_CMD    0x93
114 #define BT_RFCOMM_RPN_RSP    0x91
115 #define BT_RFCOMM_TEST_CMD   0x23
116 #define BT_RFCOMM_TEST_RSP   0x21
117 
118 typedef enum {
119     CH_EVT_RCVD_SABM = 1,
120     CH_EVT_RCVD_UA,
121     CH_EVT_RCVD_PN,
122     CH_EVT_RCVD_PN_RSP,
123     CH_EVT_RCVD_DISC,
124     CH_EVT_RCVD_DM,
125     CH_EVT_RCVD_MSC_CMD,
126     CH_EVT_RCVD_MSC_RSP,
127     CH_EVT_RCVD_NSC_RSP,
128     CH_EVT_RCVD_RLS_CMD,
129     CH_EVT_RCVD_RLS_RSP,
130     CH_EVT_RCVD_RPN_CMD,
131     CH_EVT_RCVD_RPN_REQ,
132     CH_EVT_RCVD_CREDITS,
133     CH_EVT_MULTIPLEXER_READY,
134     CH_EVT_READY_TO_SEND,
135 } RFCOMM_CHANNEL_EVENT;
136 
137 typedef struct rfcomm_channel_event {
138     RFCOMM_CHANNEL_EVENT type;
139     uint16_t dummy; // force rfcomm_channel_event to be 2-byte aligned -> avoid -Wcast-align warning
140 } rfcomm_channel_event_t;
141 
142 typedef struct rfcomm_channel_event_pn {
143     rfcomm_channel_event_t super;
144     uint16_t max_frame_size;
145     uint8_t  priority;
146     uint8_t  credits_outgoing;
147 } rfcomm_channel_event_pn_t;
148 
149 typedef struct rfcomm_channel_event_rpn {
150     rfcomm_channel_event_t super;
151     rfcomm_rpn_data_t data;
152 } rfcomm_channel_event_rpn_t;
153 
154 typedef struct rfcomm_channel_event_rls {
155     rfcomm_channel_event_t super;
156     uint8_t line_status;
157 } rfcomm_channel_event_rls_t;
158 
159 typedef struct rfcomm_channel_event_msc {
160     rfcomm_channel_event_t super;
161     uint8_t modem_status;
162 } rfcomm_channel_event_msc_t;
163 
164 
165 // global rfcomm data
166 static uint16_t      rfcomm_client_cid_generator;  // used for client channel IDs
167 
168 // linked lists for all
169 static btstack_linked_list_t rfcomm_multiplexers = NULL;
170 static btstack_linked_list_t rfcomm_channels = NULL;
171 static btstack_linked_list_t rfcomm_services = NULL;
172 
173 static gap_security_level_t rfcomm_security_level;
174 
175 #ifdef RFCOMM_USE_ERTM
176 static uint16_t rfcomm_ertm_id;
177 void (*rfcomm_ertm_request_callback)(rfcomm_ertm_request_t * request);
178 void (*rfcomm_ertm_released_callback)(uint16_t ertm_id);
179 #endif
180 
181 #ifdef RFCOMM_USE_OUTGOING_BUFFER
182 static uint8_t outgoing_buffer[1030];
183 #endif
184 
185 static int  rfcomm_channel_can_send(rfcomm_channel_t * channel);
186 static int  rfcomm_channel_ready_for_open(rfcomm_channel_t *channel);
187 static int rfcomm_channel_ready_to_send(rfcomm_channel_t * channel);
188 static void rfcomm_channel_state_machine_with_channel(rfcomm_channel_t *channel, const rfcomm_channel_event_t *event, int * out_channel_valid);
189 static void rfcomm_channel_state_machine_with_dlci(rfcomm_multiplexer_t * multiplexer, uint8_t dlci, const rfcomm_channel_event_t *event);
190 static void rfcomm_emit_can_send_now(rfcomm_channel_t *channel);
191 static int rfcomm_multiplexer_ready_to_send(rfcomm_multiplexer_t * multiplexer);
192 static void rfcomm_multiplexer_state_machine(rfcomm_multiplexer_t * multiplexer, RFCOMM_MULTIPLEXER_EVENT event);
193 
194 // MARK: RFCOMM CLIENT EVENTS
195 
196 static rfcomm_channel_t * rfcomm_channel_for_rfcomm_cid(uint16_t rfcomm_cid){
197     btstack_linked_item_t *it;
198     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
199         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
200         if (channel->rfcomm_cid == rfcomm_cid) {
201             return channel;
202         };
203     }
204     return NULL;
205 }
206 
207 static uint16_t rfcomm_next_client_cid(void){
208     do {
209         if (rfcomm_client_cid_generator == 0xffff) {
210             // don't use 0 as channel id
211             rfcomm_client_cid_generator = 1;
212         } else {
213             rfcomm_client_cid_generator++;
214         }
215     } while (rfcomm_channel_for_rfcomm_cid(rfcomm_client_cid_generator) != NULL);
216     return rfcomm_client_cid_generator;
217 }
218 
219 #ifdef RFCOMM_USE_ERTM
220 static rfcomm_multiplexer_t * rfcomm_multiplexer_for_ertm_id(uint16_t ertm_id) {
221     btstack_linked_item_t *it;
222     for (it = (btstack_linked_item_t *) rfcomm_multiplexers; it ; it = it->next){
223         rfcomm_multiplexer_t * multiplexer = ((rfcomm_multiplexer_t *) it);
224         if (multiplexer->ertm_id == ertm_id) {
225             return multiplexer;
226         };
227     }
228     return NULL;
229 }
230 
231 static uint16_t rfcomm_next_ertm_id(void){
232     do {
233         if (rfcomm_ertm_id == 0xffff) {
234             // don't use 0 as channel id
235             rfcomm_ertm_id = 1;
236         } else {
237             rfcomm_ertm_id++;
238         }
239     } while (rfcomm_multiplexer_for_ertm_id(rfcomm_ertm_id) != NULL);
240     return rfcomm_ertm_id;
241 }
242 
243 #endif
244 
245 // data: event (8), len(8), address(48), channel (8), rfcomm_cid (16)
246 static void rfcomm_emit_connection_request(rfcomm_channel_t *channel) {
247     log_info("RFCOMM_EVENT_INCOMING_CONNECTION addr %s channel #%u cid 0x%02x",
248              bd_addr_to_str(channel->multiplexer->remote_addr), channel->dlci>>1, channel->rfcomm_cid);
249     uint8_t event[11];
250     event[0] = RFCOMM_EVENT_INCOMING_CONNECTION;
251     event[1] = sizeof(event) - 2;
252     reverse_bd_addr(channel->multiplexer->remote_addr, &event[2]);
253     event[8] = channel->dlci >> 1;
254     little_endian_store_16(event, 9, channel->rfcomm_cid);
255     hci_dump_packet(HCI_EVENT_PACKET, 0, event, sizeof(event));
256 	(channel->packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
257 }
258 
259 // API Change: BTstack-0.3.50x uses
260 // data: event(8), len(8), status (8), address (48), server channel(8), rfcomm_cid(16), max frame size(16)
261 // next Cydia release will use SVN version of this
262 // data: event(8), len(8), status (8), address (48), handle (16), server channel(8), rfcomm_cid(16), max frame size(16)
263 static void rfcomm_emit_channel_opened(rfcomm_channel_t *channel, uint8_t status) {
264     log_info("RFCOMM_EVENT_CHANNEL_OPENED status 0x%x addr %s handle 0x%x channel #%u cid 0x%02x mtu %u",
265              status, bd_addr_to_str(channel->multiplexer->remote_addr), channel->multiplexer->con_handle,
266              channel->dlci>>1, channel->rfcomm_cid, channel->max_frame_size);
267     uint8_t event[18];
268     uint8_t pos = 0;
269     event[pos++] = RFCOMM_EVENT_CHANNEL_OPENED;  // 0
270     event[pos++] = sizeof(event) - 2;                   // 1
271     event[pos++] = status;                              // 2
272     reverse_bd_addr(channel->multiplexer->remote_addr, &event[pos]); pos += 6; // 3
273     little_endian_store_16(event,  pos, channel->multiplexer->con_handle);   pos += 2; // 9
274 	event[pos++] = channel->dlci >> 1;                                      // 11
275 	little_endian_store_16(event, pos, channel->rfcomm_cid); pos += 2;                 // 12 - channel ID
276 	little_endian_store_16(event, pos, channel->max_frame_size); pos += 2;   // max frame size
277     event[pos++] = channel->service ? 1 : 0;    // linked to service -> incoming
278     hci_dump_packet(HCI_EVENT_PACKET, 0, event, sizeof(event));
279 	(channel->packet_handler)(HCI_EVENT_PACKET, 0, event, pos);
280 
281     // if channel opened successfully, also send can send now if possible
282     if (status) return;
283     if (rfcomm_channel_can_send(channel)){
284         rfcomm_emit_can_send_now(channel);
285     }
286 }
287 
288 // data: event(8), len(8), rfcomm_cid(16)
289 static void rfcomm_emit_channel_closed(rfcomm_channel_t * channel) {
290     log_info("RFCOMM_EVENT_CHANNEL_CLOSED cid 0x%02x", channel->rfcomm_cid);
291     uint8_t event[4];
292     event[0] = RFCOMM_EVENT_CHANNEL_CLOSED;
293     event[1] = sizeof(event) - 2;
294     little_endian_store_16(event, 2, channel->rfcomm_cid);
295     hci_dump_packet(HCI_EVENT_PACKET, 0, event, sizeof(event));
296 	(channel->packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
297 }
298 
299 static void rfcomm_emit_remote_line_status(rfcomm_channel_t *channel, uint8_t line_status){
300     log_info("RFCOMM_EVENT_REMOTE_LINE_STATUS cid 0x%02x c, line status 0x%x", channel->rfcomm_cid, line_status);
301     uint8_t event[5];
302     event[0] = RFCOMM_EVENT_REMOTE_LINE_STATUS;
303     event[1] = sizeof(event) - 2;
304     little_endian_store_16(event, 2, channel->rfcomm_cid);
305     event[4] = line_status;
306     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
307     (channel->packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
308 }
309 
310 static void rfcomm_emit_port_configuration(rfcomm_channel_t *channel){
311     // notify client about new settings
312     uint8_t event[2+sizeof(rfcomm_rpn_data_t)];
313     event[0] = RFCOMM_EVENT_PORT_CONFIGURATION;
314     event[1] = sizeof(rfcomm_rpn_data_t);
315     memcpy(&event[2], (uint8_t*) &channel->rpn_data, sizeof(rfcomm_rpn_data_t));
316     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
317     (channel->packet_handler)(HCI_EVENT_PACKET, channel->rfcomm_cid, event, sizeof(event));
318 }
319 
320 static void rfcomm_emit_can_send_now(rfcomm_channel_t *channel) {
321     log_debug("RFCOMM_EVENT_CHANNEL_CAN_SEND_NOW local_cid 0x%x", channel->rfcomm_cid);
322     uint8_t event[4];
323     event[0] = RFCOMM_EVENT_CAN_SEND_NOW;
324     event[1] = sizeof(event) - 2;
325     little_endian_store_16(event, 2, channel->rfcomm_cid);
326     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
327     (channel->packet_handler)(HCI_EVENT_PACKET, channel->rfcomm_cid, event, sizeof(event));
328 }
329 
330 // MARK RFCOMM RPN DATA HELPER
331 static void rfcomm_rpn_data_set_defaults(rfcomm_rpn_data_t * rpn_data){
332         rpn_data->baud_rate = RPN_BAUD_9600;  /* 9600 bps */
333         rpn_data->flags = 0x03;               /* 8-n-1 */
334         rpn_data->flow_control = 0;           /* no flow control */
335         rpn_data->xon  = 0xd1;                /* XON */
336         rpn_data->xoff = 0xd3;                /* XOFF */
337         rpn_data->parameter_mask_0 = 0x7f;    /* parameter mask, all values set */
338         rpn_data->parameter_mask_1 = 0x3f;    /* parameter mask, all values set */
339 }
340 
341 static void rfcomm_rpn_data_update(rfcomm_rpn_data_t * dest, rfcomm_rpn_data_t * src){
342     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_BAUD){
343         dest->baud_rate = src->baud_rate;
344     }
345     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_DATA_BITS){
346         dest->flags = (dest->flags & 0xfc) | (src->flags & 0x03);
347     }
348     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_STOP_BITS){
349         dest->flags = (dest->flags & 0xfb) | (src->flags & 0x04);
350     }
351     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_PARITY){
352         dest->flags = (dest->flags & 0xf7) | (src->flags & 0x08);
353     }
354     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_PARITY_TYPE){
355         dest->flags = (dest->flags & 0xfc) | (src->flags & 0x30);
356     }
357     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_XON_CHAR){
358         dest->xon = src->xon;
359     }
360     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_XOFF_CHAR){
361         dest->xoff = src->xoff;
362     }
363     int i;
364     for (i=0; i < 6 ; i++){
365         uint8_t mask = 1 << i;
366         if (src->parameter_mask_1 & mask){
367             dest->flags = (dest->flags & ~mask) | (src->flags & mask);
368         }
369     }
370     // always copy parameter mask, too. informative for client, needed for response
371     dest->parameter_mask_0 = src->parameter_mask_0;
372     dest->parameter_mask_1 = src->parameter_mask_1;
373 }
374 // MARK: RFCOMM MULTIPLEXER HELPER
375 
376 static uint16_t rfcomm_max_frame_size_for_l2cap_mtu(uint16_t l2cap_mtu){
377     // Assume RFCOMM header without credits and 2 byte (14 bit) length field
378     uint16_t max_frame_size = l2cap_mtu - 5;
379     log_info("rfcomm_max_frame_size_for_l2cap_mtu:  %u -> %u", l2cap_mtu, max_frame_size);
380     return max_frame_size;
381 }
382 
383 static void rfcomm_multiplexer_initialize(rfcomm_multiplexer_t *multiplexer){
384     multiplexer->state = RFCOMM_MULTIPLEXER_CLOSED;
385     multiplexer->fcon = 1;
386     multiplexer->send_dm_for_dlci = 0;
387     multiplexer->max_frame_size = rfcomm_max_frame_size_for_l2cap_mtu(l2cap_max_mtu());
388     multiplexer->test_data_len = 0;
389     multiplexer->nsc_command = 0;
390 }
391 
392 static rfcomm_multiplexer_t * rfcomm_multiplexer_create_for_addr(bd_addr_t addr){
393 
394     // alloc structure
395     rfcomm_multiplexer_t * multiplexer = btstack_memory_rfcomm_multiplexer_get();
396     if (!multiplexer) return NULL;
397 
398     // fill in
399     rfcomm_multiplexer_initialize(multiplexer);
400     bd_addr_copy(multiplexer->remote_addr, addr);
401 
402     // add to services list
403     btstack_linked_list_add(&rfcomm_multiplexers, (btstack_linked_item_t *) multiplexer);
404 
405     return multiplexer;
406 }
407 
408 static rfcomm_multiplexer_t * rfcomm_multiplexer_for_addr(bd_addr_t addr){
409     btstack_linked_item_t *it;
410     for (it = (btstack_linked_item_t *) rfcomm_multiplexers; it ; it = it->next){
411         rfcomm_multiplexer_t * multiplexer = ((rfcomm_multiplexer_t *) it);
412         // ignore multiplexer in shutdown
413         if (multiplexer->state == RFCOMM_MULTIPLEXER_SHUTTING_DOWN) continue;
414         if (bd_addr_cmp(addr, multiplexer->remote_addr) == 0) {
415             return multiplexer;
416         };
417     }
418     return NULL;
419 }
420 
421 static rfcomm_multiplexer_t * rfcomm_multiplexer_for_l2cap_cid(uint16_t l2cap_cid) {
422     btstack_linked_item_t *it;
423     for (it = (btstack_linked_item_t *) rfcomm_multiplexers; it ; it = it->next){
424         rfcomm_multiplexer_t * multiplexer = ((rfcomm_multiplexer_t *) it);
425         if (multiplexer->l2cap_cid == l2cap_cid) {
426             return multiplexer;
427         };
428     }
429     return NULL;
430 }
431 
432 static int rfcomm_multiplexer_has_channels(rfcomm_multiplexer_t * multiplexer){
433     btstack_linked_item_t *it;
434     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
435         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
436         if (channel->multiplexer == multiplexer) {
437             return 1;
438         }
439     }
440     return 0;
441 }
442 
443 // MARK: RFCOMM CHANNEL HELPER
444 
445 static void rfcomm_dump_channels(void){
446     btstack_linked_item_t * it;
447     int channels = 0;
448     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
449         rfcomm_channel_t * channel = (rfcomm_channel_t *) it;
450         log_info("Channel #%u: addr %p, state %u", channels, channel, channel->state);
451         channels++;
452     }
453 }
454 
455 static void rfcomm_channel_initialize(rfcomm_channel_t *channel, rfcomm_multiplexer_t *multiplexer,
456                                rfcomm_service_t *service, uint8_t server_channel){
457 
458     // set defaults for port configuration (even for services)
459     rfcomm_rpn_data_set_defaults(&channel->rpn_data);
460 
461     channel->state            = RFCOMM_CHANNEL_CLOSED;
462     channel->state_var        = RFCOMM_CHANNEL_STATE_VAR_NONE;
463 
464     channel->multiplexer      = multiplexer;
465     channel->rfcomm_cid       = rfcomm_next_client_cid();
466     channel->max_frame_size   = multiplexer->max_frame_size;
467 
468     channel->credits_incoming = 0;
469     channel->credits_outgoing = 0;
470 
471     // incoming flow control not active
472     channel->new_credits_incoming  = RFCOMM_CREDITS;
473     channel->incoming_flow_control = 0;
474 
475     channel->rls_line_status       = RFCOMM_RLS_STATUS_INVALID;
476 
477     channel->service = service;
478 	if (service) {
479 		// incoming connection
480     	channel->dlci = (server_channel << 1) |  multiplexer->outgoing;
481         if (channel->max_frame_size > service->max_frame_size) {
482             channel->max_frame_size = service->max_frame_size;
483         }
484         channel->incoming_flow_control = service->incoming_flow_control;
485         channel->new_credits_incoming  = service->incoming_initial_credits;
486         channel->packet_handler        = service->packet_handler;
487 	} else {
488 		// outgoing connection
489 		channel->dlci = (server_channel << 1) | (multiplexer->outgoing ^ 1);
490 	}
491 }
492 
493 // service == NULL -> outgoing channel
494 static rfcomm_channel_t * rfcomm_channel_create(rfcomm_multiplexer_t * multiplexer,
495                                                 rfcomm_service_t * service, uint8_t server_channel){
496 
497     log_info("rfcomm_channel_create for service %p, channel %u --- list of channels:", service, server_channel);
498     rfcomm_dump_channels();
499 
500     // alloc structure
501     rfcomm_channel_t * channel = btstack_memory_rfcomm_channel_get();
502     if (!channel) return NULL;
503 
504     // fill in
505     rfcomm_channel_initialize(channel, multiplexer, service, server_channel);
506 
507     // add to services list
508     btstack_linked_list_add(&rfcomm_channels, (btstack_linked_item_t *) channel);
509 
510     return channel;
511 }
512 
513 static void rfcomm_notify_channel_can_send(void){
514     btstack_linked_list_iterator_t it;
515     btstack_linked_list_iterator_init(&it, &rfcomm_channels);
516     while (btstack_linked_list_iterator_has_next(&it)){
517         rfcomm_channel_t * channel = (rfcomm_channel_t *) btstack_linked_list_iterator_next(&it);
518         if (!channel->waiting_for_can_send_now) continue; // didn't try to send yet
519         if (!rfcomm_channel_can_send(channel)) continue;  // or cannot yet either
520 
521         channel->waiting_for_can_send_now = 0;
522         rfcomm_emit_can_send_now(channel);
523     }
524 }
525 
526 static rfcomm_channel_t * rfcomm_channel_for_multiplexer_and_dlci(rfcomm_multiplexer_t * multiplexer, uint8_t dlci){
527     btstack_linked_item_t *it;
528     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
529         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
530         if ((channel->dlci == dlci) && (channel->multiplexer == multiplexer)) {
531             return channel;
532         };
533     }
534     return NULL;
535 }
536 
537 static rfcomm_service_t * rfcomm_service_for_channel(uint8_t server_channel){
538     btstack_linked_item_t *it;
539     for (it = (btstack_linked_item_t *) rfcomm_services; it ; it = it->next){
540         rfcomm_service_t * service = ((rfcomm_service_t *) it);
541         if ( service->server_channel == server_channel){
542             return service;
543         };
544     }
545     return NULL;
546 }
547 
548 // MARK: RFCOMM SEND
549 
550 /**
551  * @param credits - only used for RFCOMM flow control in UIH wiht P/F = 1
552  */
553 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){
554 
555     if (!l2cap_can_send_packet_now(multiplexer->l2cap_cid)) return BTSTACK_ACL_BUFFERS_FULL;
556 
557 #ifdef RFCOMM_USE_OUTGOING_BUFFER
558     uint8_t * rfcomm_out_buffer = outgoing_buffer;
559 #else
560     l2cap_reserve_packet_buffer();
561     uint8_t * rfcomm_out_buffer = l2cap_get_outgoing_buffer();
562 #endif
563 
564 	uint16_t pos = 0;
565 	uint8_t crc_fields = 3;
566 
567 	rfcomm_out_buffer[pos++] = address;
568 	rfcomm_out_buffer[pos++] = control;
569 
570 	// length field can be 1 or 2 octets
571 	if (len < 128){
572 		rfcomm_out_buffer[pos++] = (len << 1)| 1;     // bits 0-6
573 	} else {
574 		rfcomm_out_buffer[pos++] = (len & 0x7f) << 1; // bits 0-6
575 		rfcomm_out_buffer[pos++] = len >> 7;          // bits 7-14
576 		crc_fields++;
577 	}
578 
579 	// add credits for UIH frames when PF bit is set
580 	if (control == BT_RFCOMM_UIH_PF){
581 		rfcomm_out_buffer[pos++] = credits;
582 	}
583 
584 	// copy actual data
585 	if (len) {
586 		memcpy(&rfcomm_out_buffer[pos], data, len);
587 		pos += len;
588 	}
589 
590 	// UIH frames only calc FCS over address + control (5.1.1)
591 	if ((control & 0xef) == BT_RFCOMM_UIH){
592 		crc_fields = 2;
593 	}
594 	rfcomm_out_buffer[pos++] =  btstack_crc8_calc(rfcomm_out_buffer, crc_fields); // calc fcs
595 
596 #ifdef RFCOMM_USE_OUTGOING_BUFFER
597     int err = l2cap_send(multiplexer->l2cap_cid, rfcomm_out_buffer, pos);
598 #else
599     int err = l2cap_send_prepared(multiplexer->l2cap_cid, pos);
600 #endif
601 
602     return err;
603 }
604 
605 // simplified version of rfcomm_send_packet_for_multiplexer for prepared rfcomm packet (UIH, 2 byte len, no credits)
606 static int rfcomm_send_uih_prepared(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint16_t len){
607 
608     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) | (dlci << 2);
609     uint8_t control = BT_RFCOMM_UIH;
610 
611 #ifdef RFCOMM_USE_OUTGOING_BUFFER
612     uint8_t * rfcomm_out_buffer = outgoing_buffer;
613 #else
614     uint8_t * rfcomm_out_buffer = l2cap_get_outgoing_buffer();
615 #endif
616 
617     uint16_t pos = 0;
618     rfcomm_out_buffer[pos++] = address;
619     rfcomm_out_buffer[pos++] = control;
620     rfcomm_out_buffer[pos++] = (len & 0x7f) << 1; // bits 0-6
621     rfcomm_out_buffer[pos++] = len >> 7;          // bits 7-14
622 
623     // actual data is already in place
624     pos += len;
625 
626     // UIH frames only calc FCS over address + control (5.1.1)
627     rfcomm_out_buffer[pos++] =  btstack_crc8_calc(rfcomm_out_buffer, 2); // calc fcs
628 
629 #ifdef RFCOMM_USE_OUTGOING_BUFFER
630     int err = l2cap_send(multiplexer->l2cap_cid, rfcomm_out_buffer, pos);
631 #else
632     int err = l2cap_send_prepared(multiplexer->l2cap_cid, pos);
633 #endif
634 
635     return err;
636 }
637 
638 // C/R Flag in Address
639 // - terms: initiator = station that creates multiplexer with SABM
640 // - terms: responder = station that responds to multiplexer setup with UA
641 // "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"
642 //    - command initiator = 1 /response responder = 1
643 //    - command responder = 0 /response initiator = 0
644 // "For UIH frames, the C/R bit is always set according to section 5.4.3.1 in GSM 07.10.
645 //  This applies independently of what is contained wthin the UIH frames, either data or control messages."
646 //    - c/r = 1 for frames by initiating station, 0 = for frames by responding station
647 
648 // C/R Flag in Message
649 // "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."
650 //   - If the C/R bit is set to 1 the message is a command
651 //   - if it is set to 0 the message is a response.
652 
653 // temp/old messge construction
654 
655 // new object oriented version
656 static int rfcomm_send_sabm(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
657 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) | (dlci << 2);   // command
658     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_SABM, 0, NULL, 0);
659 }
660 
661 static int rfcomm_send_disc(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
662 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) | (dlci << 2);  // command
663     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_DISC, 0, NULL, 0);
664 }
665 
666 static int rfcomm_send_ua(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
667 	uint8_t address = (1 << 0) | ((multiplexer->outgoing ^ 1) << 1) | (dlci << 2); // response
668     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UA, 0, NULL, 0);
669 }
670 
671 static int rfcomm_send_dm_pf(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
672 	uint8_t address = (1 << 0) | ((multiplexer->outgoing ^ 1) << 1) | (dlci << 2); // response
673     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_DM_PF, 0, NULL, 0);
674 }
675 
676 static int rfcomm_send_uih_fc_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t fcon) {
677     uint8_t address = (1 << 0) | (multiplexer->outgoing<< 1);
678     uint8_t payload[2];
679     uint8_t pos = 0;
680     payload[pos++] = fcon ? BT_RFCOMM_FCON_RSP : BT_RFCOMM_FCOFF_RSP;
681     payload[pos++] = (0 << 1) | 1;  // len
682     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
683 }
684 
685 // static int rfcomm_send_uih_test_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t * data, uint16_t len) {
686 //     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
687 //     uint8_t payload[2+len];
688 //     uint8_t pos = 0;
689 //     payload[pos++] = BT_RFCOMM_TEST_CMD;
690 //     payload[pos++] = (len + 1) << 1 | 1;  // len
691 //     memcpy(&payload[pos], data, len);
692 //     pos += len;
693 //     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
694 // }
695 
696 static int rfcomm_send_uih_test_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t * data, uint16_t len) {
697     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
698     uint8_t payload[2+RFCOMM_TEST_DATA_MAX_LEN];
699     uint8_t pos = 0;
700     payload[pos++] = BT_RFCOMM_TEST_RSP;
701     if (len > RFCOMM_TEST_DATA_MAX_LEN) {
702         len = RFCOMM_TEST_DATA_MAX_LEN;
703     }
704     payload[pos++] = (len << 1) | 1;  // len
705     memcpy(&payload[pos], data, len);
706     pos += len;
707     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
708 }
709 
710 static int rfcomm_send_uih_msc_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t signals) {
711 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
712 	uint8_t payload[4];
713 	uint8_t pos = 0;
714 	payload[pos++] = BT_RFCOMM_MSC_CMD;
715 	payload[pos++] = (2 << 1) | 1;  // len
716 	payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
717 	payload[pos++] = signals;
718 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
719 }
720 
721 static int rfcomm_send_uih_msc_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t signals) {
722 	uint8_t address = (1 << 0) | (multiplexer->outgoing<< 1);
723 	uint8_t payload[4];
724 	uint8_t pos = 0;
725 	payload[pos++] = BT_RFCOMM_MSC_RSP;
726 	payload[pos++] = (2 << 1) | 1;  // len
727 	payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
728 	payload[pos++] = signals;
729 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
730 }
731 
732 static int rfcomm_send_uih_nsc_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t command) {
733     uint8_t address = (1 << 0) | (multiplexer->outgoing<< 1);
734     uint8_t payload[3];
735     uint8_t pos = 0;
736     payload[pos++] = BT_RFCOMM_NSC_RSP;
737     payload[pos++] = (1 << 1) | 1;  // len
738     payload[pos++] = command;
739     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
740 }
741 
742 static int rfcomm_send_uih_pn_command(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint16_t max_frame_size){
743 	uint8_t payload[10];
744 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
745 	uint8_t pos = 0;
746 	payload[pos++] = BT_RFCOMM_PN_CMD;
747 	payload[pos++] = (8 << 1) | 1;  // len
748 	payload[pos++] = dlci;
749 	payload[pos++] = 0xf0; // pre-defined for Bluetooth, see 5.5.3 of TS 07.10 Adaption for RFCOMM
750 	payload[pos++] = 0; // priority
751 	payload[pos++] = 0; // max 60 seconds ack
752 	payload[pos++] = max_frame_size & 0xff; // max framesize low
753 	payload[pos++] = max_frame_size >> 8;   // max framesize high
754 	payload[pos++] = 0x00; // number of retransmissions
755 	payload[pos++] = 0x00; // (unused error recovery window) initial number of credits
756 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
757 }
758 
759 // "The response may not change the DLCI, the priority, the convergence layer, or the timer value." rfcomm_tutorial.pdf
760 static int rfcomm_send_uih_pn_response(rfcomm_multiplexer_t *multiplexer, uint8_t dlci,
761                                        uint8_t priority, uint16_t max_frame_size){
762 	uint8_t payload[10];
763 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
764 	uint8_t pos = 0;
765 	payload[pos++] = BT_RFCOMM_PN_RSP;
766 	payload[pos++] = (8 << 1) | 1;  // len
767 	payload[pos++] = dlci;
768 	payload[pos++] = 0xe0; // pre defined for Bluetooth, see 5.5.3 of TS 07.10 Adaption for RFCOMM
769 	payload[pos++] = priority; // priority
770 	payload[pos++] = 0; // max 60 seconds ack
771 	payload[pos++] = max_frame_size & 0xff; // max framesize low
772 	payload[pos++] = max_frame_size >> 8;   // max framesize high
773 	payload[pos++] = 0x00; // number of retransmissions
774 	payload[pos++] = 0x00; // (unused error recovery window) initial number of credits
775 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
776 }
777 
778 static int rfcomm_send_uih_rls_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t line_status) {
779     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
780     uint8_t payload[4];
781     uint8_t pos = 0;
782     payload[pos++] = BT_RFCOMM_RLS_CMD;
783     payload[pos++] = (2 << 1) | 1;  // len
784     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
785     payload[pos++] = line_status;
786     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
787 }
788 
789 static int rfcomm_send_uih_rls_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t line_status) {
790     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
791     uint8_t payload[4];
792     uint8_t pos = 0;
793     payload[pos++] = BT_RFCOMM_RLS_RSP;
794     payload[pos++] = (2 << 1) | 1;  // len
795     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
796     payload[pos++] = line_status;
797     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
798 }
799 
800 static int rfcomm_send_uih_rpn_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, rfcomm_rpn_data_t *rpn_data) {
801     uint8_t payload[10];
802     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
803     uint8_t pos = 0;
804     payload[pos++] = BT_RFCOMM_RPN_CMD;
805     payload[pos++] = (8 << 1) | 1;  // len
806     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
807     payload[pos++] = rpn_data->baud_rate;
808     payload[pos++] = rpn_data->flags;
809     payload[pos++] = rpn_data->flow_control;
810     payload[pos++] = rpn_data->xon;
811     payload[pos++] = rpn_data->xoff;
812     payload[pos++] = rpn_data->parameter_mask_0;
813     payload[pos++] = rpn_data->parameter_mask_1;
814     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
815 }
816 
817 static int rfcomm_send_uih_rpn_req(rfcomm_multiplexer_t *multiplexer, uint8_t dlci) {
818     uint8_t payload[3];
819     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
820     uint8_t pos = 0;
821     payload[pos++] = BT_RFCOMM_RPN_CMD;
822     payload[pos++] = (1 << 1) | 1;  // len
823     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
824     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
825 }
826 
827 static int rfcomm_send_uih_rpn_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, rfcomm_rpn_data_t *rpn_data) {
828 	uint8_t payload[10];
829 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
830 	uint8_t pos = 0;
831 	payload[pos++] = BT_RFCOMM_RPN_RSP;
832 	payload[pos++] = (8 << 1) | 1;  // len
833 	payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
834 	payload[pos++] = rpn_data->baud_rate;
835 	payload[pos++] = rpn_data->flags;
836 	payload[pos++] = rpn_data->flow_control;
837 	payload[pos++] = rpn_data->xon;
838 	payload[pos++] = rpn_data->xoff;
839 	payload[pos++] = rpn_data->parameter_mask_0;
840 	payload[pos++] = rpn_data->parameter_mask_1;
841 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
842 }
843 
844 static void rfcomm_send_uih_credits(rfcomm_multiplexer_t *multiplexer, uint8_t dlci,  uint8_t credits){
845     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) |  (dlci << 2);
846     rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH_PF, credits, NULL, 0);
847 }
848 
849 // depending on channel state emit channel opened with status or channel closed
850 static void rfcomm_channel_emit_final_event(rfcomm_channel_t * channel, uint8_t status){
851     // emit appropriate events
852     switch(channel->state){
853         case RFCOMM_CHANNEL_OPEN:
854         case RFCOMM_CHANNEL_W4_UA_AFTER_DISC:
855             rfcomm_emit_channel_closed(channel);
856             break;
857         case RFCOMM_CHANNEL_SEND_UA_AFTER_DISC:
858             // remote didn't wait until we send the UA disc
859             // close event already emitted
860             break;
861         default:
862             rfcomm_emit_channel_opened(channel, status);
863             break;
864     }
865 }
866 
867 // MARK: RFCOMM MULTIPLEXER
868 static void rfcomm_multiplexer_stop_timer(rfcomm_multiplexer_t * multiplexer){
869     if (multiplexer->timer_active) {
870         btstack_run_loop_remove_timer(&multiplexer->timer);
871         multiplexer->timer_active = 0;
872     }
873 }
874 static void rfcomm_multiplexer_free(rfcomm_multiplexer_t * multiplexer){
875     btstack_linked_list_remove( &rfcomm_multiplexers, (btstack_linked_item_t *) multiplexer);
876     btstack_memory_rfcomm_multiplexer_free(multiplexer);
877 }
878 
879 static void rfcomm_multiplexer_finalize(rfcomm_multiplexer_t * multiplexer){
880     // remove (potential) timer
881     rfcomm_multiplexer_stop_timer(multiplexer);
882 
883     // close and remove all channels
884     btstack_linked_item_t *it = (btstack_linked_item_t *) &rfcomm_channels;
885     while (it->next){
886         rfcomm_channel_t * channel = (rfcomm_channel_t *) it->next;
887         if (channel->multiplexer == multiplexer) {
888             // emit open with status or closed
889             rfcomm_channel_emit_final_event(channel, RFCOMM_MULTIPLEXER_STOPPED);
890             // remove from list
891             it->next = it->next->next;
892             // free channel struct
893             btstack_memory_rfcomm_channel_free(channel);
894         } else {
895             it = it->next;
896         }
897     }
898 
899     // remove mutliplexer
900     rfcomm_multiplexer_free(multiplexer);
901 }
902 
903 static void rfcomm_multiplexer_timer_handler(btstack_timer_source_t *timer){
904     rfcomm_multiplexer_t * multiplexer = (rfcomm_multiplexer_t*) btstack_run_loop_get_timer_context(timer);
905     if (rfcomm_multiplexer_has_channels(multiplexer)) return;
906 
907     log_info("rfcomm_multiplexer_timer_handler timeout: shutting down multiplexer! (no channels)");
908     uint16_t l2cap_cid = multiplexer->l2cap_cid;
909     rfcomm_multiplexer_finalize(multiplexer);
910     l2cap_disconnect(l2cap_cid, 0x13);
911 }
912 
913 static void rfcomm_multiplexer_prepare_idle_timer(rfcomm_multiplexer_t * multiplexer){
914     if (multiplexer->timer_active) {
915         btstack_run_loop_remove_timer(&multiplexer->timer);
916         multiplexer->timer_active = 0;
917     }
918     if (rfcomm_multiplexer_has_channels(multiplexer)) return;
919 
920     // start idle timer for multiplexer timeout check as there are no rfcomm channels yet
921     btstack_run_loop_set_timer(&multiplexer->timer, RFCOMM_MULIPLEXER_TIMEOUT_MS);
922     btstack_run_loop_set_timer_handler(&multiplexer->timer, rfcomm_multiplexer_timer_handler);
923     btstack_run_loop_set_timer_context(&multiplexer->timer, multiplexer);
924     btstack_run_loop_add_timer(&multiplexer->timer);
925     multiplexer->timer_active = 1;
926 }
927 
928 static void rfcomm_multiplexer_opened(rfcomm_multiplexer_t *multiplexer){
929     log_info("Multiplexer up and running");
930     multiplexer->state = RFCOMM_MULTIPLEXER_OPEN;
931 
932     const rfcomm_channel_event_t event = { CH_EVT_MULTIPLEXER_READY, 0};
933 
934     // transition of channels that wait for multiplexer
935     btstack_linked_item_t *it;
936     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
937         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
938         if (channel->multiplexer != multiplexer) continue;
939         int rfcomm_channel_valid = 1;
940         rfcomm_channel_state_machine_with_channel(channel, &event, &rfcomm_channel_valid);
941         if (rfcomm_channel_valid && rfcomm_channel_ready_to_send(channel)){
942             l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
943         }
944     }
945     rfcomm_multiplexer_prepare_idle_timer(multiplexer);
946 
947     // request can send now for multiplexer if ready
948     if (rfcomm_multiplexer_ready_to_send(multiplexer)){
949         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
950     }
951 }
952 
953 static void rfcomm_handle_can_send_now(uint16_t l2cap_cid){
954 
955     log_debug("rfcomm_handle_can_send_now enter: %u", l2cap_cid);
956 
957     btstack_linked_list_iterator_t it;
958     int token_consumed = 0;
959 
960     // forward token to multiplexer
961     btstack_linked_list_iterator_init(&it, &rfcomm_multiplexers);
962     while (!token_consumed && btstack_linked_list_iterator_has_next(&it)){
963         rfcomm_multiplexer_t * multiplexer = (rfcomm_multiplexer_t *) btstack_linked_list_iterator_next(&it);
964         if (multiplexer->l2cap_cid != l2cap_cid) continue;
965         if (rfcomm_multiplexer_ready_to_send(multiplexer)){
966             log_debug("rfcomm_handle_can_send_now enter: multiplexer token");
967             token_consumed = 1;
968             rfcomm_multiplexer_state_machine(multiplexer, MULT_EV_READY_TO_SEND);
969         }
970     }
971 
972     // forward token to channel state machine
973     btstack_linked_list_iterator_init(&it, &rfcomm_channels);
974     while (!token_consumed && btstack_linked_list_iterator_has_next(&it)){
975         rfcomm_channel_t * channel = (rfcomm_channel_t *) btstack_linked_list_iterator_next(&it);
976         if (channel->multiplexer->l2cap_cid != l2cap_cid) continue;
977         // channel state machine
978         if (rfcomm_channel_ready_to_send(channel)){
979             log_debug("rfcomm_handle_can_send_now enter: channel token");
980             token_consumed = 1;
981             const rfcomm_channel_event_t event = { CH_EVT_READY_TO_SEND, 0 };
982             int rfcomm_channel_valid = 1;
983             rfcomm_channel_state_machine_with_channel(channel, &event, &rfcomm_channel_valid);
984         }
985     }
986 
987     // forward token to client
988     btstack_linked_list_iterator_init(&it, &rfcomm_channels);
989     while (!token_consumed && btstack_linked_list_iterator_has_next(&it)){
990         rfcomm_channel_t * channel = (rfcomm_channel_t *) btstack_linked_list_iterator_next(&it);
991         if (channel->multiplexer->l2cap_cid != l2cap_cid) continue;
992         // client waiting for can send now
993         if (!channel->waiting_for_can_send_now)    continue;
994         if ((channel->multiplexer->fcon & 1) == 0) continue;
995         if (!channel->credits_outgoing){
996             log_debug("rfcomm_handle_can_send_now waiting to send but no credits (ignore)");
997             continue;
998         }
999 
1000         log_debug("rfcomm_handle_can_send_now enter: client token");
1001         token_consumed = 1;
1002         channel->waiting_for_can_send_now = 0;
1003         rfcomm_emit_can_send_now(channel);
1004     }
1005 
1006     // if token was consumed, request another one
1007     if (token_consumed) {
1008         l2cap_request_can_send_now_event(l2cap_cid);
1009     }
1010 
1011     log_debug("rfcomm_handle_can_send_now exit");
1012 }
1013 
1014 static void rfcomm_multiplexer_set_state_and_request_can_send_now_event(rfcomm_multiplexer_t * multiplexer, RFCOMM_MULTIPLEXER_STATE state){
1015     multiplexer->state = state;
1016     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1017 }
1018 
1019 /**
1020  * @return handled packet
1021  */
1022 static int rfcomm_hci_event_handler(uint8_t *packet, uint16_t size){
1023 
1024     UNUSED(size);   // ok: handling own l2cap events
1025 
1026     bd_addr_t event_addr;
1027     uint16_t  psm;
1028     uint16_t l2cap_cid;
1029     hci_con_handle_t con_handle;
1030     rfcomm_multiplexer_t *multiplexer = NULL;
1031     uint8_t status;
1032 
1033     switch (hci_event_packet_get_type(packet)) {
1034 
1035         // accept incoming rfcomm connection if no multiplexer exists yet
1036         case L2CAP_EVENT_INCOMING_CONNECTION:
1037             // data: event(8), len(8), address(48), handle (16),  psm (16), source cid(16) dest cid(16)
1038             reverse_bd_addr(&packet[2], event_addr);
1039             con_handle = little_endian_read_16(packet,  8);
1040             psm        = little_endian_read_16(packet, 10);
1041             l2cap_cid  = little_endian_read_16(packet, 12);
1042 
1043             if (psm != BLUETOOTH_PROTOCOL_RFCOMM) break;
1044 
1045             multiplexer = rfcomm_multiplexer_for_addr(event_addr);
1046 
1047             if (multiplexer) {
1048                 log_info("INCOMING_CONNECTION (l2cap_cid 0x%02x) for BLUETOOTH_PROTOCOL_RFCOMM => decline - multiplexer already exists", l2cap_cid);
1049                 l2cap_decline_connection(l2cap_cid);
1050                 return 1;
1051             }
1052 
1053             // create and inititialize new multiplexer instance (incoming)
1054             multiplexer = rfcomm_multiplexer_create_for_addr(event_addr);
1055             if (!multiplexer){
1056                 log_info("INCOMING_CONNECTION (l2cap_cid 0x%02x) for BLUETOOTH_PROTOCOL_RFCOMM => decline - no memory left", l2cap_cid);
1057                 l2cap_decline_connection(l2cap_cid);
1058                 return 1;
1059             }
1060 
1061             multiplexer->con_handle = con_handle;
1062             multiplexer->l2cap_cid = l2cap_cid;
1063             //
1064             multiplexer->state = RFCOMM_MULTIPLEXER_W4_SABM_0;
1065             log_info("L2CAP_EVENT_INCOMING_CONNECTION (l2cap_cid 0x%02x) for BLUETOOTH_PROTOCOL_RFCOMM => accept", l2cap_cid);
1066 
1067 #ifdef RFCOMM_USE_ERTM
1068             // request
1069             rfcomm_ertm_request_t request;
1070             memset(&request, 0, sizeof(rfcomm_ertm_request_t));
1071             memcpy(request.addr, event_addr, 6);
1072             request.ertm_id = rfcomm_next_ertm_id();
1073             if (rfcomm_ertm_request_callback){
1074                 (*rfcomm_ertm_request_callback)(&request);
1075             }
1076             if (request.ertm_config && request.ertm_buffer && request.ertm_buffer_size){
1077                 multiplexer->ertm_id = request.ertm_id;
1078                 l2cap_accept_ertm_connection(l2cap_cid, request.ertm_config, request.ertm_buffer, request.ertm_buffer_size);
1079                 return 1;
1080             }
1081 #endif
1082 
1083             l2cap_accept_connection(l2cap_cid);
1084             return 1;
1085 
1086         // l2cap connection opened -> store l2cap_cid, remote_addr
1087         case L2CAP_EVENT_CHANNEL_OPENED:
1088 
1089             if (little_endian_read_16(packet, 11) != BLUETOOTH_PROTOCOL_RFCOMM) break;
1090 
1091             status = packet[2];
1092             log_info("L2CAP_EVENT_CHANNEL_OPENED for BLUETOOTH_PROTOCOL_RFCOMM, status %u", status);
1093 
1094             // get multiplexer for remote addr
1095             con_handle = little_endian_read_16(packet, 9);
1096             l2cap_cid = little_endian_read_16(packet, 13);
1097             reverse_bd_addr(&packet[3], event_addr);
1098             multiplexer = rfcomm_multiplexer_for_addr(event_addr);
1099             if (!multiplexer) {
1100                 log_error("L2CAP_EVENT_CHANNEL_OPENED but no multiplexer prepared");
1101                 return 1;
1102             }
1103 
1104             // on l2cap open error discard everything
1105             if (status){
1106 
1107                 // remove (potential) timer
1108                 rfcomm_multiplexer_stop_timer(multiplexer);
1109 
1110                 // mark multiplexer as shutting down
1111                 multiplexer->state = RFCOMM_MULTIPLEXER_SHUTTING_DOWN;
1112 
1113                 // emit rfcomm_channel_opened with status and free channel
1114                 // note: repeatedly go over list until full iteration causes no further change
1115                 int done;
1116                 do {
1117                     done = 1;
1118                     btstack_linked_item_t * it = (btstack_linked_item_t *) &rfcomm_channels;
1119                     while (it->next) {
1120                         rfcomm_channel_t * channel = (rfcomm_channel_t *) it->next;
1121                         if (channel->multiplexer == multiplexer){
1122                             done = 0;
1123                             rfcomm_emit_channel_opened(channel, status);
1124                             btstack_linked_list_remove(&rfcomm_channels, (btstack_linked_item_t *) channel);
1125                             btstack_memory_rfcomm_channel_free(channel);
1126                             break;
1127                         } else {
1128                             it = it->next;
1129                         }
1130                     }
1131                 } while (!done);
1132 
1133                 // free multiplexer
1134                 rfcomm_multiplexer_free(multiplexer);
1135                 return 1;
1136             }
1137 
1138             // following could be: rfcom_multiplexer_state_machein(..., EVENT_L2CAP_OPENED)
1139 
1140             // set max frame size based on l2cap MTU
1141             multiplexer->max_frame_size = rfcomm_max_frame_size_for_l2cap_mtu(little_endian_read_16(packet, 17));
1142 
1143             if (multiplexer->state == RFCOMM_MULTIPLEXER_W4_CONNECT) {
1144                 log_info("L2CAP_EVENT_CHANNEL_OPENED: outgoing connection");
1145                 // wrong remote addr
1146                 if (bd_addr_cmp(event_addr, multiplexer->remote_addr)) break;
1147                 multiplexer->l2cap_cid = l2cap_cid;
1148                 multiplexer->con_handle = con_handle;
1149                 // send SABM #0
1150                 rfcomm_multiplexer_set_state_and_request_can_send_now_event(multiplexer, RFCOMM_MULTIPLEXER_SEND_SABM_0);
1151 
1152             }
1153             return 1;
1154 
1155             // l2cap disconnect -> state = RFCOMM_MULTIPLEXER_CLOSED;
1156 
1157         // Notify channel packet handler if they can send now
1158         case L2CAP_EVENT_CAN_SEND_NOW:
1159             l2cap_cid = l2cap_event_can_send_now_get_local_cid(packet);
1160             rfcomm_handle_can_send_now(l2cap_cid);
1161             return 1;
1162 
1163         case L2CAP_EVENT_CHANNEL_CLOSED:
1164             // data: event (8), len(8), channel (16)
1165             l2cap_cid = little_endian_read_16(packet, 2);
1166             multiplexer = rfcomm_multiplexer_for_l2cap_cid(l2cap_cid);
1167             log_info("L2CAP_EVENT_CHANNEL_CLOSED cid 0x%0x, mult %p", l2cap_cid, multiplexer);
1168             if (!multiplexer) break;
1169             log_info("L2CAP_EVENT_CHANNEL_CLOSED state %u", multiplexer->state);
1170             // no need to call l2cap_disconnect here, as it's already closed
1171             rfcomm_multiplexer_finalize(multiplexer);
1172             return 1;
1173 
1174 #ifdef RFCOMM_USE_ERTM
1175         case L2CAP_EVENT_ERTM_BUFFER_RELEASED:
1176             l2cap_cid = l2cap_event_ertm_buffer_released_get_local_cid(packet);
1177             multiplexer = rfcomm_multiplexer_for_l2cap_cid(l2cap_cid);
1178             if (multiplexer) {
1179                 log_info("buffer for ertm id %u released", multiplexer->ertm_id);
1180                 if (rfcomm_ertm_released_callback){
1181                     (*rfcomm_ertm_released_callback)(multiplexer->ertm_id);
1182                 }
1183             }
1184             break;
1185 #endif
1186 
1187         default:
1188             break;
1189     }
1190     return 0;
1191 }
1192 
1193 static int rfcomm_multiplexer_l2cap_packet_handler(uint16_t channel, uint8_t *packet, uint16_t size){
1194     // get or create a multiplexer for a certain device
1195     rfcomm_multiplexer_t *multiplexer = rfcomm_multiplexer_for_l2cap_cid(channel);
1196     if (!multiplexer) return 0;
1197 
1198     uint16_t l2cap_cid = multiplexer->l2cap_cid;
1199 
1200 	// but only care for multiplexer control channel
1201     uint8_t frame_dlci = packet[0] >> 2;
1202     if (frame_dlci) return 0;
1203     const uint8_t length_offset = (packet[2] & 1) ^ 1;  // to be used for pos >= 3
1204     const uint8_t credit_offset = ((packet[1] & BT_RFCOMM_UIH_PF) == BT_RFCOMM_UIH_PF) ? 1 : 0;   // credits for uih_pf frames
1205     const uint8_t payload_offset = 3 + length_offset + credit_offset;
1206     switch (packet[1]){
1207 
1208         case BT_RFCOMM_SABM:
1209             if (multiplexer->state == RFCOMM_MULTIPLEXER_W4_SABM_0){
1210                 log_info("Received SABM #0");
1211                 multiplexer->outgoing = 0;
1212                 rfcomm_multiplexer_set_state_and_request_can_send_now_event(multiplexer, RFCOMM_MULTIPLEXER_SEND_UA_0);
1213                 return 1;
1214             }
1215             break;
1216 
1217         case BT_RFCOMM_UA:
1218             if (multiplexer->state == RFCOMM_MULTIPLEXER_W4_UA_0) {
1219                 // UA #0 -> send UA #0, state = RFCOMM_MULTIPLEXER_OPEN
1220                 log_info("Received UA #0 ");
1221                 rfcomm_multiplexer_opened(multiplexer);
1222                 return 1;
1223             }
1224             break;
1225 
1226         case BT_RFCOMM_DISC:
1227             // DISC #0 -> send UA #0, close multiplexer
1228             log_info("Received DISC #0, (ougoing = %u)", multiplexer->outgoing);
1229             rfcomm_multiplexer_set_state_and_request_can_send_now_event(multiplexer, RFCOMM_MULTIPLEXER_SEND_UA_0_AND_DISC);
1230             return 1;
1231 
1232         case BT_RFCOMM_DM:
1233             // DM #0 - we shouldn't get this, just give up
1234             log_info("Received DM #0");
1235             log_info("-> Closing down multiplexer");
1236             rfcomm_multiplexer_finalize(multiplexer);
1237             l2cap_disconnect(l2cap_cid, 0x13);
1238             return 1;
1239 
1240         case BT_RFCOMM_UIH:
1241             if (packet[payload_offset] == BT_RFCOMM_CLD_CMD){
1242                 // Multiplexer close down (CLD) -> close mutliplexer
1243                 log_info("Received Multiplexer close down command");
1244                 log_info("-> Closing down multiplexer");
1245                 rfcomm_multiplexer_finalize(multiplexer);
1246                 l2cap_disconnect(l2cap_cid, 0x13);
1247                 return 1;
1248             }
1249             switch (packet[payload_offset]){
1250                 case BT_RFCOMM_CLD_CMD:
1251                      // Multiplexer close down (CLD) -> close mutliplexer
1252                     log_info("Received Multiplexer close down command");
1253                     log_info("-> Closing down multiplexer");
1254                     rfcomm_multiplexer_finalize(multiplexer);
1255                     l2cap_disconnect(l2cap_cid, 0x13);
1256                     return 1;
1257 
1258                 case BT_RFCOMM_FCON_CMD:
1259                     multiplexer->fcon = 0x81;
1260                     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1261                     return 1;
1262 
1263                 case BT_RFCOMM_FCOFF_CMD:
1264                     multiplexer->fcon = 0x80;
1265                     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1266                     return 1;
1267 
1268                 case BT_RFCOMM_TEST_CMD: {
1269                     log_info("Received test command");
1270                     int len = packet[payload_offset+1] >> 1; // length < 125
1271                     if (len > RFCOMM_TEST_DATA_MAX_LEN){
1272                         len = RFCOMM_TEST_DATA_MAX_LEN;
1273                     }
1274                     len = btstack_min(len, size - 1 - payload_offset);  // avoid information leak
1275                     multiplexer->test_data_len = len;
1276                     memcpy(multiplexer->test_data, &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 = LEVEL_2;
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     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){
2411             status = BTSTACK_MEMORY_ALLOC_FAILED;
2412             goto fail;
2413         }
2414         multiplexer->outgoing = 1;
2415         multiplexer->state = RFCOMM_MULTIPLEXER_W4_CONNECT;
2416         new_multiplexer = 1;
2417     }
2418 
2419     // check if channel for this remote service already exists
2420     dlci = (server_channel << 1) | (multiplexer->outgoing ^ 1);
2421     channel = rfcomm_channel_for_multiplexer_and_dlci(multiplexer, dlci);
2422     if (channel){
2423         status = RFCOMM_CHANNEL_ALREADY_REGISTERED;
2424         goto fail;
2425     }
2426 
2427     // prepare channel
2428     channel = rfcomm_channel_create(multiplexer, NULL, server_channel);
2429     if (!channel){
2430         status = BTSTACK_MEMORY_ALLOC_FAILED;
2431         goto fail;
2432     }
2433 
2434     // rfcomm_cid is already assigned by rfcomm_channel_create
2435     channel->incoming_flow_control = incoming_flow_control;
2436     channel->new_credits_incoming  = initial_credits;
2437     channel->packet_handler = packet_handler;
2438 
2439     // return rfcomm_cid
2440     if (out_rfcomm_cid){
2441         *out_rfcomm_cid = channel->rfcomm_cid;
2442     }
2443 
2444     // start multiplexer setup
2445     if (multiplexer->state != RFCOMM_MULTIPLEXER_OPEN) {
2446         channel->state = RFCOMM_CHANNEL_W4_MULTIPLEXER;
2447         uint16_t l2cap_cid = 0;
2448 #ifdef RFCOMM_USE_ERTM
2449         // request
2450         rfcomm_ertm_request_t request;
2451         memset(&request, 0, sizeof(rfcomm_ertm_request_t));
2452         memcpy(request.addr, addr, 6);
2453         request.ertm_id = rfcomm_next_ertm_id();
2454         if (rfcomm_ertm_request_callback){
2455             (*rfcomm_ertm_request_callback)(&request);
2456         }
2457         if (request.ertm_config && request.ertm_buffer && request.ertm_buffer_size){
2458             multiplexer->ertm_id = request.ertm_id;
2459             status = l2cap_create_ertm_channel(rfcomm_packet_handler, addr, BLUETOOTH_PROTOCOL_RFCOMM,
2460                         request.ertm_config, request.ertm_buffer, request.ertm_buffer_size, &l2cap_cid);
2461         }
2462         else
2463 #endif
2464         {
2465             status = l2cap_create_channel(rfcomm_packet_handler, addr, BLUETOOTH_PROTOCOL_RFCOMM, l2cap_max_mtu(), &l2cap_cid);
2466         }
2467         if (status) goto fail;
2468         multiplexer->l2cap_cid = l2cap_cid;
2469         return 0;
2470     }
2471 
2472     channel->state = RFCOMM_CHANNEL_SEND_UIH_PN;
2473 
2474     // start connecting, if multiplexer is already up and running
2475     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
2476     return 0;
2477 
2478 fail:
2479     if (new_multiplexer) btstack_memory_rfcomm_multiplexer_free(multiplexer);
2480     if (channel)         btstack_memory_rfcomm_channel_free(channel);
2481     return status;
2482 }
2483 
2484 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){
2485     return rfcomm_channel_create_internal(packet_handler, addr, server_channel, 1, initial_credits, out_rfcomm_cid);
2486 }
2487 
2488 uint8_t rfcomm_create_channel(btstack_packet_handler_t packet_handler, bd_addr_t addr, uint8_t server_channel, uint16_t * out_rfcomm_cid){
2489     return rfcomm_channel_create_internal(packet_handler, addr, server_channel, 0, RFCOMM_CREDITS, out_rfcomm_cid);
2490 }
2491 
2492 void rfcomm_disconnect(uint16_t rfcomm_cid){
2493     log_info("RFCOMM_DISCONNECT cid 0x%02x", rfcomm_cid);
2494     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2495     if (!channel) return;
2496 
2497     channel->state = RFCOMM_CHANNEL_SEND_DISC;
2498     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2499 }
2500 
2501 static uint8_t rfcomm_register_service_internal(btstack_packet_handler_t packet_handler,
2502     uint8_t channel, uint16_t max_frame_size, uint8_t incoming_flow_control, uint8_t initial_credits){
2503 
2504     log_info("RFCOMM_REGISTER_SERVICE channel #%u mtu %u flow_control %u credits %u",
2505              channel, max_frame_size, incoming_flow_control, initial_credits);
2506 
2507     // check if already registered
2508     rfcomm_service_t * service = rfcomm_service_for_channel(channel);
2509     if (service){
2510         return RFCOMM_CHANNEL_ALREADY_REGISTERED;
2511     }
2512 
2513     // alloc structure
2514     service = btstack_memory_rfcomm_service_get();
2515     if (!service) {
2516         return BTSTACK_MEMORY_ALLOC_FAILED;
2517     }
2518 
2519     // register with l2cap if not registered before, max MTU
2520     if (btstack_linked_list_empty(&rfcomm_services)){
2521         l2cap_register_service(rfcomm_packet_handler, BLUETOOTH_PROTOCOL_RFCOMM, 0xffff, rfcomm_security_level);
2522     }
2523 
2524     // fill in
2525     service->packet_handler = packet_handler;
2526     service->server_channel = channel;
2527     service->max_frame_size = max_frame_size;
2528     service->incoming_flow_control = incoming_flow_control;
2529     service->incoming_initial_credits = initial_credits;
2530 
2531     // add to services list
2532     btstack_linked_list_add(&rfcomm_services, (btstack_linked_item_t *) service);
2533 
2534     return 0;
2535 }
2536 
2537 uint8_t rfcomm_register_service_with_initial_credits(btstack_packet_handler_t packet_handler,
2538     uint8_t channel, uint16_t max_frame_size, uint8_t initial_credits){
2539 
2540     return rfcomm_register_service_internal(packet_handler, channel, max_frame_size, 1, initial_credits);
2541 }
2542 
2543 uint8_t rfcomm_register_service(btstack_packet_handler_t packet_handler, uint8_t channel,
2544     uint16_t max_frame_size){
2545 
2546     return rfcomm_register_service_internal(packet_handler, channel, max_frame_size, 0,RFCOMM_CREDITS);
2547 }
2548 
2549 void rfcomm_unregister_service(uint8_t service_channel){
2550     log_info("RFCOMM_UNREGISTER_SERVICE #%u", service_channel);
2551     rfcomm_service_t *service = rfcomm_service_for_channel(service_channel);
2552     if (!service) return;
2553     btstack_linked_list_remove(&rfcomm_services, (btstack_linked_item_t *) service);
2554     btstack_memory_rfcomm_service_free(service);
2555 
2556     // unregister if no services active
2557     if (btstack_linked_list_empty(&rfcomm_services)){
2558         // bt_send_cmd(&l2cap_unregister_service, BLUETOOTH_PROTOCOL_RFCOMM);
2559         l2cap_unregister_service(BLUETOOTH_PROTOCOL_RFCOMM);
2560     }
2561 }
2562 
2563 void rfcomm_accept_connection(uint16_t rfcomm_cid){
2564     log_info("RFCOMM_ACCEPT_CONNECTION cid 0x%02x", rfcomm_cid);
2565     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2566     if (!channel) return;
2567     switch (channel->state) {
2568         case RFCOMM_CHANNEL_INCOMING_SETUP:
2569             rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_CLIENT_ACCEPTED);
2570             if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_PN){
2571                 rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP);
2572                 l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2573             }
2574             if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_SABM){
2575                 rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_UA);
2576                 l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2577             }
2578             // at least one of { PN RSP, UA } needs to be sent
2579             // state transistion incoming setup -> dlc setup happens in rfcomm_run after these have been sent
2580             break;
2581         default:
2582             break;
2583     }
2584 
2585 }
2586 
2587 void rfcomm_decline_connection(uint16_t rfcomm_cid){
2588     log_info("RFCOMM_DECLINE_CONNECTION cid 0x%02x", rfcomm_cid);
2589     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2590     if (!channel) return;
2591     switch (channel->state) {
2592         case RFCOMM_CHANNEL_INCOMING_SETUP:
2593             channel->state = RFCOMM_CHANNEL_SEND_DM;
2594             l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2595             break;
2596         default:
2597             break;
2598     }
2599 }
2600 
2601 void rfcomm_grant_credits(uint16_t rfcomm_cid, uint8_t credits){
2602     log_info("RFCOMM_GRANT_CREDITS cid 0x%02x credits %u", rfcomm_cid, credits);
2603     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2604     if (!channel) return;
2605     if (!channel->incoming_flow_control) return;
2606     channel->new_credits_incoming += credits;
2607 
2608     // process
2609     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2610 }
2611 
2612 #ifdef RFCOMM_USE_ERTM
2613 void rfcomm_enable_l2cap_ertm(void request_callback(rfcomm_ertm_request_t * request), void released_callback(uint16_t ertm_id)){
2614     rfcomm_ertm_request_callback  = request_callback;
2615     rfcomm_ertm_released_callback = released_callback;
2616 }
2617 #endif
2618