xref: /btstack/src/classic/rfcomm.c (revision a8d51f092f1b660d0f6921369ad2bc3f9368296c)
1 /*
2  * Copyright (C) 2014 BlueKitchen GmbH
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the copyright holders nor the names of
14  *    contributors may be used to endorse or promote products derived
15  *    from this software without specific prior written permission.
16  * 4. Any redistribution, use, or modification is done solely for
17  *    personal benefit and not for any commercial purpose or for
18  *    monetary gain.
19  *
20  * THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
24  * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
26  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
27  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
30  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  *
33  * Please inquire about commercial licensing options at
34  * [email protected]
35  *
36  */
37 
38 #define BTSTACK_FILE__ "rfcomm.c"
39 
40 /*
41  *  rfcomm.c
42  */
43 
44 #include <string.h> // memcpy
45 #include <stdint.h>
46 
47 #include "bluetooth_sdp.h"
48 #include "btstack_debug.h"
49 #include "btstack_event.h"
50 #include "btstack_memory.h"
51 #include "btstack_util.h"
52 #include "classic/core.h"
53 #include "classic/rfcomm.h"
54 #include "hci.h"
55 #include "hci_cmd.h"
56 #include "hci_dump.h"
57 #include "l2cap.h"
58 
59 // workaround for missing PRIxPTR on mspgcc (16/20-bit MCU)
60 #ifndef PRIxPTR
61 #if defined(__MSP430X__)  &&  defined(__MSP430X_LARGE__)
62 #define PRIxPTR "lx"
63 #else
64 #define PRIxPTR "x"
65 #endif
66 #endif
67 
68 // ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM requires ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE
69 #ifdef ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM
70 #ifdef ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE
71 #define RFCOMM_USE_OUTGOING_BUFFER
72 #define RFCOMM_USE_ERTM
73 #else
74 #error "ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM requires ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE. "
75 #error "Please disable ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM, or, "
76 #error "enable ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE"
77 #endif
78 #endif
79 
80 #define RFCOMM_MULIPLEXER_TIMEOUT_MS 60000
81 
82 #define RFCOMM_CREDITS 10
83 
84 // FCS calc
85 #define BT_RFCOMM_CODE_WORD         0xE0 // pol = x8+x2+x1+1
86 #define BT_RFCOMM_CRC_CHECK_LEN     3
87 #define BT_RFCOMM_UIHCRC_CHECK_LEN  2
88 
89 // Control field values      bit no.       1 2 3 4 PF 6 7 8
90 #define BT_RFCOMM_SABM       0x3F       // 1 1 1 1  1 1 0 0
91 #define BT_RFCOMM_UA         0x73       // 1 1 0 0  1 1 1 0
92 #define BT_RFCOMM_DM         0x0F       // 1 1 1 1  0 0 0 0
93 #define BT_RFCOMM_DM_PF      0x1F       // 1 1 1 1  1 0 0 0
94 #define BT_RFCOMM_DISC       0x53       // 1 1 0 0  1 0 1 0
95 #define BT_RFCOMM_UIH        0xEF       // 1 1 1 1  0 1 1 1
96 #define BT_RFCOMM_UIH_PF     0xFF       // 1 1 1 1  0 1 1 1
97 
98 // Multiplexer message types
99 #define BT_RFCOMM_CLD_CMD    0xC3
100 #define BT_RFCOMM_FCON_CMD   0xA3
101 #define BT_RFCOMM_FCON_RSP   0xA1
102 #define BT_RFCOMM_FCOFF_CMD  0x63
103 #define BT_RFCOMM_FCOFF_RSP  0x61
104 #define BT_RFCOMM_MSC_CMD    0xE3
105 #define BT_RFCOMM_MSC_RSP    0xE1
106 #define BT_RFCOMM_NSC_RSP    0x11
107 #define BT_RFCOMM_PN_CMD     0x83
108 #define BT_RFCOMM_PN_RSP     0x81
109 #define BT_RFCOMM_RLS_CMD    0x53
110 #define BT_RFCOMM_RLS_RSP    0x51
111 #define BT_RFCOMM_RPN_CMD    0x93
112 #define BT_RFCOMM_RPN_RSP    0x91
113 #define BT_RFCOMM_TEST_CMD   0x23
114 #define BT_RFCOMM_TEST_RSP   0x21
115 
116 typedef enum {
117     CH_EVT_RCVD_SABM = 1,
118     CH_EVT_RCVD_UA,
119     CH_EVT_RCVD_PN,
120     CH_EVT_RCVD_PN_RSP,
121     CH_EVT_RCVD_DISC,
122     CH_EVT_RCVD_DM,
123     CH_EVT_RCVD_MSC_CMD,
124     CH_EVT_RCVD_MSC_RSP,
125     CH_EVT_RCVD_NSC_RSP,
126     CH_EVT_RCVD_RLS_CMD,
127     CH_EVT_RCVD_RLS_RSP,
128     CH_EVT_RCVD_RPN_CMD,
129     CH_EVT_RCVD_RPN_REQ,
130     CH_EVT_RCVD_CREDITS,
131     CH_EVT_MULTIPLEXER_READY,
132     CH_EVT_READY_TO_SEND,
133 } RFCOMM_CHANNEL_EVENT;
134 
135 typedef struct rfcomm_channel_event {
136     RFCOMM_CHANNEL_EVENT type;
137     uint16_t dummy; // force rfcomm_channel_event to be 2-byte aligned -> avoid -Wcast-align warning
138 } rfcomm_channel_event_t;
139 
140 typedef struct rfcomm_channel_event_pn {
141     rfcomm_channel_event_t super;
142     uint16_t max_frame_size;
143     uint8_t  priority;
144     uint8_t  credits_outgoing;
145 } rfcomm_channel_event_pn_t;
146 
147 typedef struct rfcomm_channel_event_rpn {
148     rfcomm_channel_event_t super;
149     rfcomm_rpn_data_t data;
150 } rfcomm_channel_event_rpn_t;
151 
152 typedef struct rfcomm_channel_event_rls {
153     rfcomm_channel_event_t super;
154     uint8_t line_status;
155 } rfcomm_channel_event_rls_t;
156 
157 typedef struct rfcomm_channel_event_msc {
158     rfcomm_channel_event_t super;
159     uint8_t modem_status;
160 } rfcomm_channel_event_msc_t;
161 
162 
163 // global rfcomm data
164 static uint16_t      rfcomm_client_cid_generator;  // used for client channel IDs
165 
166 // linked lists for all
167 static btstack_linked_list_t rfcomm_multiplexers = NULL;
168 static btstack_linked_list_t rfcomm_channels = NULL;
169 static btstack_linked_list_t rfcomm_services = NULL;
170 
171 static gap_security_level_t rfcomm_security_level;
172 
173 #ifdef RFCOMM_USE_ERTM
174 static uint16_t rfcomm_ertm_id;
175 void (*rfcomm_ertm_request_callback)(rfcomm_ertm_request_t * request);
176 void (*rfcomm_ertm_released_callback)(uint16_t ertm_id);
177 #endif
178 
179 #ifdef RFCOMM_USE_OUTGOING_BUFFER
180 static uint8_t outgoing_buffer[1030];
181 #endif
182 
183 static int  rfcomm_channel_can_send(rfcomm_channel_t * channel);
184 static int  rfcomm_channel_ready_for_open(rfcomm_channel_t *channel);
185 static int rfcomm_channel_ready_to_send(rfcomm_channel_t * channel);
186 static void rfcomm_channel_state_machine_with_channel(rfcomm_channel_t *channel, const rfcomm_channel_event_t *event, int * out_channel_valid);
187 static void rfcomm_channel_state_machine_with_dlci(rfcomm_multiplexer_t * multiplexer, uint8_t dlci, const rfcomm_channel_event_t *event);
188 static void rfcomm_emit_can_send_now(rfcomm_channel_t *channel);
189 static int rfcomm_multiplexer_ready_to_send(rfcomm_multiplexer_t * multiplexer);
190 static void rfcomm_multiplexer_state_machine(rfcomm_multiplexer_t * multiplexer, RFCOMM_MULTIPLEXER_EVENT event);
191 
192 // MARK: RFCOMM CLIENT EVENTS
193 
194 static rfcomm_channel_t * rfcomm_channel_for_rfcomm_cid(uint16_t rfcomm_cid){
195     btstack_linked_item_t *it;
196     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
197         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
198         if (channel->rfcomm_cid == rfcomm_cid) {
199             return channel;
200         };
201     }
202     return NULL;
203 }
204 
205 static uint16_t rfcomm_next_client_cid(void){
206     do {
207         if (rfcomm_client_cid_generator == 0xffff) {
208             // don't use 0 as channel id
209             rfcomm_client_cid_generator = 1;
210         } else {
211             rfcomm_client_cid_generator++;
212         }
213     } while (rfcomm_channel_for_rfcomm_cid(rfcomm_client_cid_generator) != NULL);
214     return rfcomm_client_cid_generator;
215 }
216 
217 #ifdef RFCOMM_USE_ERTM
218 static rfcomm_multiplexer_t * rfcomm_multiplexer_for_ertm_id(uint16_t ertm_id) {
219     btstack_linked_item_t *it;
220     for (it = (btstack_linked_item_t *) rfcomm_multiplexers; it ; it = it->next){
221         rfcomm_multiplexer_t * multiplexer = ((rfcomm_multiplexer_t *) it);
222         if (multiplexer->ertm_id == ertm_id) {
223             return multiplexer;
224         };
225     }
226     return NULL;
227 }
228 
229 static uint16_t rfcomm_next_ertm_id(void){
230     do {
231         if (rfcomm_ertm_id == 0xffff) {
232             // don't use 0 as channel id
233             rfcomm_ertm_id = 1;
234         } else {
235             rfcomm_ertm_id++;
236         }
237     } while (rfcomm_multiplexer_for_ertm_id(rfcomm_ertm_id) != NULL);
238     return rfcomm_ertm_id;
239 }
240 
241 #endif
242 
243 // data: event (8), len(8), address(48), channel (8), rfcomm_cid (16)
244 static void rfcomm_emit_connection_request(rfcomm_channel_t *channel) {
245     log_info("RFCOMM_EVENT_INCOMING_CONNECTION addr %s channel #%u cid 0x%02x",
246              bd_addr_to_str(channel->multiplexer->remote_addr), channel->dlci>>1, channel->rfcomm_cid);
247     uint8_t event[11];
248     event[0] = RFCOMM_EVENT_INCOMING_CONNECTION;
249     event[1] = sizeof(event) - 2;
250     reverse_bd_addr(channel->multiplexer->remote_addr, &event[2]);
251     event[8] = channel->dlci >> 1;
252     little_endian_store_16(event, 9, channel->rfcomm_cid);
253     hci_dump_packet(HCI_EVENT_PACKET, 0, event, sizeof(event));
254 	(channel->packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
255 }
256 
257 // API Change: BTstack-0.3.50x uses
258 // data: event(8), len(8), status (8), address (48), server channel(8), rfcomm_cid(16), max frame size(16)
259 // next Cydia release will use SVN version of this
260 // data: event(8), len(8), status (8), address (48), handle (16), server channel(8), rfcomm_cid(16), max frame size(16)
261 static void rfcomm_emit_channel_opened(rfcomm_channel_t *channel, uint8_t status) {
262     log_info("RFCOMM_EVENT_CHANNEL_OPENED status 0x%x addr %s handle 0x%x channel #%u cid 0x%02x mtu %u",
263              status, bd_addr_to_str(channel->multiplexer->remote_addr), channel->multiplexer->con_handle,
264              channel->dlci>>1, channel->rfcomm_cid, channel->max_frame_size);
265     uint8_t event[18];
266     uint8_t pos = 0;
267     event[pos++] = RFCOMM_EVENT_CHANNEL_OPENED;  // 0
268     event[pos++] = sizeof(event) - 2;                   // 1
269     event[pos++] = status;                              // 2
270     reverse_bd_addr(channel->multiplexer->remote_addr, &event[pos]); pos += 6; // 3
271     little_endian_store_16(event,  pos, channel->multiplexer->con_handle);   pos += 2; // 9
272 	event[pos++] = channel->dlci >> 1;                                      // 11
273 	little_endian_store_16(event, pos, channel->rfcomm_cid); pos += 2;                 // 12 - channel ID
274 	little_endian_store_16(event, pos, channel->max_frame_size); pos += 2;   // max frame size
275     event[pos++] = channel->service ? 1 : 0;    // linked to service -> incoming
276     hci_dump_packet(HCI_EVENT_PACKET, 0, event, sizeof(event));
277 	(channel->packet_handler)(HCI_EVENT_PACKET, 0, event, pos);
278 
279     // if channel opened successfully, also send can send now if possible
280     if (status) return;
281     if (rfcomm_channel_can_send(channel)){
282         rfcomm_emit_can_send_now(channel);
283     }
284 }
285 
286 // data: event(8), len(8), rfcomm_cid(16)
287 static void rfcomm_emit_channel_closed(rfcomm_channel_t * channel) {
288     log_info("RFCOMM_EVENT_CHANNEL_CLOSED cid 0x%02x", channel->rfcomm_cid);
289     uint8_t event[4];
290     event[0] = RFCOMM_EVENT_CHANNEL_CLOSED;
291     event[1] = sizeof(event) - 2;
292     little_endian_store_16(event, 2, channel->rfcomm_cid);
293     hci_dump_packet(HCI_EVENT_PACKET, 0, event, sizeof(event));
294 	(channel->packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
295 }
296 
297 static void rfcomm_emit_remote_line_status(rfcomm_channel_t *channel, uint8_t line_status){
298     log_info("RFCOMM_EVENT_REMOTE_LINE_STATUS cid 0x%02x c, line status 0x%x", channel->rfcomm_cid, line_status);
299     uint8_t event[5];
300     event[0] = RFCOMM_EVENT_REMOTE_LINE_STATUS;
301     event[1] = sizeof(event) - 2;
302     little_endian_store_16(event, 2, channel->rfcomm_cid);
303     event[4] = line_status;
304     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
305     (channel->packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
306 }
307 
308 static void rfcomm_emit_port_configuration(rfcomm_channel_t *channel){
309     // notify client about new settings
310     uint8_t event[2+sizeof(rfcomm_rpn_data_t)];
311     event[0] = RFCOMM_EVENT_PORT_CONFIGURATION;
312     event[1] = sizeof(rfcomm_rpn_data_t);
313     (void)memcpy(&event[2], (uint8_t *)&channel->rpn_data,
314                  sizeof(rfcomm_rpn_data_t));
315     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
316     (channel->packet_handler)(HCI_EVENT_PACKET, channel->rfcomm_cid, event, sizeof(event));
317 }
318 
319 static void rfcomm_emit_can_send_now(rfcomm_channel_t *channel) {
320     log_debug("RFCOMM_EVENT_CHANNEL_CAN_SEND_NOW local_cid 0x%x", channel->rfcomm_cid);
321     uint8_t event[4];
322     event[0] = RFCOMM_EVENT_CAN_SEND_NOW;
323     event[1] = sizeof(event) - 2;
324     little_endian_store_16(event, 2, channel->rfcomm_cid);
325     hci_dump_packet( HCI_EVENT_PACKET, 0, event, sizeof(event));
326     (channel->packet_handler)(HCI_EVENT_PACKET, channel->rfcomm_cid, event, sizeof(event));
327 }
328 
329 // MARK RFCOMM RPN DATA HELPER
330 static void rfcomm_rpn_data_set_defaults(rfcomm_rpn_data_t * rpn_data){
331         rpn_data->baud_rate = RPN_BAUD_9600;  /* 9600 bps */
332         rpn_data->flags = 0x03;               /* 8-n-1 */
333         rpn_data->flow_control = 0;           /* no flow control */
334         rpn_data->xon  = 0xd1;                /* XON */
335         rpn_data->xoff = 0xd3;                /* XOFF */
336         rpn_data->parameter_mask_0 = 0x7f;    /* parameter mask, all values set */
337         rpn_data->parameter_mask_1 = 0x3f;    /* parameter mask, all values set */
338 }
339 
340 static void rfcomm_rpn_data_update(rfcomm_rpn_data_t * dest, rfcomm_rpn_data_t * src){
341     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_BAUD){
342         dest->baud_rate = src->baud_rate;
343     }
344     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_DATA_BITS){
345         dest->flags = (dest->flags & 0xfc) | (src->flags & 0x03);
346     }
347     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_STOP_BITS){
348         dest->flags = (dest->flags & 0xfb) | (src->flags & 0x04);
349     }
350     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_PARITY){
351         dest->flags = (dest->flags & 0xf7) | (src->flags & 0x08);
352     }
353     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_PARITY_TYPE){
354         dest->flags = (dest->flags & 0xfc) | (src->flags & 0x30);
355     }
356     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_XON_CHAR){
357         dest->xon = src->xon;
358     }
359     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_XOFF_CHAR){
360         dest->xoff = src->xoff;
361     }
362     int i;
363     for (i=0; i < 6 ; i++){
364         uint8_t mask = 1 << i;
365         if (src->parameter_mask_1 & mask){
366             dest->flags = (dest->flags & ~mask) | (src->flags & mask);
367         }
368     }
369     // always copy parameter mask, too. informative for client, needed for response
370     dest->parameter_mask_0 = src->parameter_mask_0;
371     dest->parameter_mask_1 = src->parameter_mask_1;
372 }
373 // MARK: RFCOMM MULTIPLEXER HELPER
374 
375 static uint16_t rfcomm_max_frame_size_for_l2cap_mtu(uint16_t l2cap_mtu){
376     // Assume RFCOMM header without credits and 2 byte (14 bit) length field
377     uint16_t max_frame_size = l2cap_mtu - 5;
378     log_info("rfcomm_max_frame_size_for_l2cap_mtu:  %u -> %u", l2cap_mtu, max_frame_size);
379     return max_frame_size;
380 }
381 
382 static void rfcomm_multiplexer_initialize(rfcomm_multiplexer_t *multiplexer){
383     multiplexer->state = RFCOMM_MULTIPLEXER_CLOSED;
384     multiplexer->fcon = 1;
385     multiplexer->send_dm_for_dlci = 0;
386     multiplexer->max_frame_size = rfcomm_max_frame_size_for_l2cap_mtu(l2cap_max_mtu());
387     multiplexer->test_data_len = 0;
388     multiplexer->nsc_command = 0;
389 }
390 
391 static rfcomm_multiplexer_t * rfcomm_multiplexer_create_for_addr(bd_addr_t addr){
392 
393     // alloc structure
394     rfcomm_multiplexer_t * multiplexer = btstack_memory_rfcomm_multiplexer_get();
395     if (!multiplexer) return NULL;
396 
397     // fill in
398     rfcomm_multiplexer_initialize(multiplexer);
399     bd_addr_copy(multiplexer->remote_addr, addr);
400 
401     // add to services list
402     btstack_linked_list_add(&rfcomm_multiplexers, (btstack_linked_item_t *) multiplexer);
403 
404     return multiplexer;
405 }
406 
407 static rfcomm_multiplexer_t * rfcomm_multiplexer_for_addr(bd_addr_t addr){
408     btstack_linked_item_t *it;
409     for (it = (btstack_linked_item_t *) rfcomm_multiplexers; it ; it = it->next){
410         rfcomm_multiplexer_t * multiplexer = ((rfcomm_multiplexer_t *) it);
411         // ignore multiplexer in shutdown
412         if (multiplexer->state == RFCOMM_MULTIPLEXER_SHUTTING_DOWN) continue;
413         if (bd_addr_cmp(addr, multiplexer->remote_addr) == 0) {
414             return multiplexer;
415         };
416     }
417     return NULL;
418 }
419 
420 static rfcomm_multiplexer_t * rfcomm_multiplexer_for_l2cap_cid(uint16_t l2cap_cid) {
421     btstack_linked_item_t *it;
422     for (it = (btstack_linked_item_t *) rfcomm_multiplexers; it ; it = it->next){
423         rfcomm_multiplexer_t * multiplexer = ((rfcomm_multiplexer_t *) it);
424         if (multiplexer->l2cap_cid == l2cap_cid) {
425             return multiplexer;
426         };
427     }
428     return NULL;
429 }
430 
431 static int rfcomm_multiplexer_has_channels(rfcomm_multiplexer_t * multiplexer){
432     btstack_linked_item_t *it;
433     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
434         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
435         if (channel->multiplexer == multiplexer) {
436             return 1;
437         }
438     }
439     return 0;
440 }
441 
442 // MARK: RFCOMM CHANNEL HELPER
443 
444 static void rfcomm_dump_channels(void){
445 #ifdef ENABLE_LOG_INFO
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 #endif
454 }
455 
456 static void rfcomm_channel_initialize(rfcomm_channel_t *channel, rfcomm_multiplexer_t *multiplexer,
457                                rfcomm_service_t *service, uint8_t server_channel){
458 
459     // set defaults for port configuration (even for services)
460     rfcomm_rpn_data_set_defaults(&channel->rpn_data);
461 
462     channel->state            = RFCOMM_CHANNEL_CLOSED;
463     channel->state_var        = RFCOMM_CHANNEL_STATE_VAR_NONE;
464 
465     channel->multiplexer      = multiplexer;
466     channel->rfcomm_cid       = rfcomm_next_client_cid();
467     channel->max_frame_size   = multiplexer->max_frame_size;
468 
469     channel->credits_incoming = 0;
470     channel->credits_outgoing = 0;
471 
472     // incoming flow control not active
473     channel->new_credits_incoming  = RFCOMM_CREDITS;
474     channel->incoming_flow_control = 0;
475 
476     channel->rls_line_status       = RFCOMM_RLS_STATUS_INVALID;
477 
478     channel->service = service;
479 	if (service) {
480 		// incoming connection
481     	channel->dlci = (server_channel << 1) |  multiplexer->outgoing;
482         if (channel->max_frame_size > service->max_frame_size) {
483             channel->max_frame_size = service->max_frame_size;
484         }
485         channel->incoming_flow_control = service->incoming_flow_control;
486         channel->new_credits_incoming  = service->incoming_initial_credits;
487         channel->packet_handler        = service->packet_handler;
488 	} else {
489 		// outgoing connection
490 		channel->dlci = (server_channel << 1) | (multiplexer->outgoing ^ 1);
491 	}
492 }
493 
494 // service == NULL -> outgoing channel
495 static rfcomm_channel_t * rfcomm_channel_create(rfcomm_multiplexer_t * multiplexer,
496                                                 rfcomm_service_t * service, uint8_t server_channel){
497 
498     log_info("rfcomm_channel_create for service %p, channel %u --- list of channels:", service, server_channel);
499     rfcomm_dump_channels();
500 
501     // alloc structure
502     rfcomm_channel_t * channel = btstack_memory_rfcomm_channel_get();
503     if (!channel) return NULL;
504 
505     // fill in
506     rfcomm_channel_initialize(channel, multiplexer, service, server_channel);
507 
508     // add to services list
509     btstack_linked_list_add(&rfcomm_channels, (btstack_linked_item_t *) channel);
510 
511     return channel;
512 }
513 
514 static void rfcomm_notify_channel_can_send(void){
515     btstack_linked_list_iterator_t it;
516     btstack_linked_list_iterator_init(&it, &rfcomm_channels);
517     while (btstack_linked_list_iterator_has_next(&it)){
518         rfcomm_channel_t * channel = (rfcomm_channel_t *) btstack_linked_list_iterator_next(&it);
519         if (!channel->waiting_for_can_send_now) continue; // didn't try to send yet
520         if (!rfcomm_channel_can_send(channel)) continue;  // or cannot yet either
521 
522         channel->waiting_for_can_send_now = 0;
523         rfcomm_emit_can_send_now(channel);
524     }
525 }
526 
527 static rfcomm_channel_t * rfcomm_channel_for_multiplexer_and_dlci(rfcomm_multiplexer_t * multiplexer, uint8_t dlci){
528     btstack_linked_item_t *it;
529     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
530         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
531         if ((channel->dlci == dlci) && (channel->multiplexer == multiplexer)) {
532             return channel;
533         };
534     }
535     return NULL;
536 }
537 
538 static rfcomm_service_t * rfcomm_service_for_channel(uint8_t server_channel){
539     btstack_linked_item_t *it;
540     for (it = (btstack_linked_item_t *) rfcomm_services; it ; it = it->next){
541         rfcomm_service_t * service = ((rfcomm_service_t *) it);
542         if ( service->server_channel == server_channel){
543             return service;
544         };
545     }
546     return NULL;
547 }
548 
549 // MARK: RFCOMM SEND
550 
551 /**
552  * @param credits - only used for RFCOMM flow control in UIH wiht P/F = 1
553  */
554 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){
555 
556     if (!l2cap_can_send_packet_now(multiplexer->l2cap_cid)) return BTSTACK_ACL_BUFFERS_FULL;
557 
558 #ifdef RFCOMM_USE_OUTGOING_BUFFER
559     uint8_t * rfcomm_out_buffer = outgoing_buffer;
560 #else
561     l2cap_reserve_packet_buffer();
562     uint8_t * rfcomm_out_buffer = l2cap_get_outgoing_buffer();
563 #endif
564 
565 	uint16_t pos = 0;
566 	uint8_t crc_fields = 3;
567 
568 	rfcomm_out_buffer[pos++] = address;
569 	rfcomm_out_buffer[pos++] = control;
570 
571 	// length field can be 1 or 2 octets
572 	if (len < 128){
573 		rfcomm_out_buffer[pos++] = (len << 1)| 1;     // bits 0-6
574 	} else {
575 		rfcomm_out_buffer[pos++] = (len & 0x7f) << 1; // bits 0-6
576 		rfcomm_out_buffer[pos++] = len >> 7;          // bits 7-14
577 		crc_fields++;
578 	}
579 
580 	// add credits for UIH frames when PF bit is set
581 	if (control == BT_RFCOMM_UIH_PF){
582 		rfcomm_out_buffer[pos++] = credits;
583 	}
584 
585 	// copy actual data
586 	if (len) {
587 		(void)memcpy(&rfcomm_out_buffer[pos], data, len);
588 		pos += len;
589 	}
590 
591 	// UIH frames only calc FCS over address + control (5.1.1)
592 	if ((control & 0xef) == BT_RFCOMM_UIH){
593 		crc_fields = 2;
594 	}
595 	rfcomm_out_buffer[pos++] =  btstack_crc8_calc(rfcomm_out_buffer, crc_fields); // calc fcs
596 
597 #ifdef RFCOMM_USE_OUTGOING_BUFFER
598     int err = l2cap_send(multiplexer->l2cap_cid, rfcomm_out_buffer, pos);
599 #else
600     int err = l2cap_send_prepared(multiplexer->l2cap_cid, pos);
601 #endif
602 
603     return err;
604 }
605 
606 // simplified version of rfcomm_send_packet_for_multiplexer for prepared rfcomm packet (UIH, 2 byte len, no credits)
607 static int rfcomm_send_uih_prepared(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint16_t len){
608 
609     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) | (dlci << 2);
610     uint8_t control = BT_RFCOMM_UIH;
611 
612 #ifdef RFCOMM_USE_OUTGOING_BUFFER
613     uint8_t * rfcomm_out_buffer = outgoing_buffer;
614 #else
615     uint8_t * rfcomm_out_buffer = l2cap_get_outgoing_buffer();
616 #endif
617 
618     uint16_t pos = 0;
619     rfcomm_out_buffer[pos++] = address;
620     rfcomm_out_buffer[pos++] = control;
621     rfcomm_out_buffer[pos++] = (len & 0x7f) << 1; // bits 0-6
622     rfcomm_out_buffer[pos++] = len >> 7;          // bits 7-14
623 
624     // actual data is already in place
625     pos += len;
626 
627     // UIH frames only calc FCS over address + control (5.1.1)
628     rfcomm_out_buffer[pos++] =  btstack_crc8_calc(rfcomm_out_buffer, 2); // calc fcs
629 
630 #ifdef RFCOMM_USE_OUTGOING_BUFFER
631     int err = l2cap_send(multiplexer->l2cap_cid, rfcomm_out_buffer, pos);
632 #else
633     int err = l2cap_send_prepared(multiplexer->l2cap_cid, pos);
634 #endif
635 
636     return err;
637 }
638 
639 // C/R Flag in Address
640 // - terms: initiator = station that creates multiplexer with SABM
641 // - terms: responder = station that responds to multiplexer setup with UA
642 // "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"
643 //    - command initiator = 1 /response responder = 1
644 //    - command responder = 0 /response initiator = 0
645 // "For UIH frames, the C/R bit is always set according to section 5.4.3.1 in GSM 07.10.
646 //  This applies independently of what is contained wthin the UIH frames, either data or control messages."
647 //    - c/r = 1 for frames by initiating station, 0 = for frames by responding station
648 
649 // C/R Flag in Message
650 // "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."
651 //   - If the C/R bit is set to 1 the message is a command
652 //   - if it is set to 0 the message is a response.
653 
654 // temp/old messge construction
655 
656 // new object oriented version
657 static int rfcomm_send_sabm(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
658 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) | (dlci << 2);   // command
659     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_SABM, 0, NULL, 0);
660 }
661 
662 static int rfcomm_send_disc(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
663 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) | (dlci << 2);  // command
664     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_DISC, 0, NULL, 0);
665 }
666 
667 static int rfcomm_send_ua(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
668 	uint8_t address = (1 << 0) | ((multiplexer->outgoing ^ 1) << 1) | (dlci << 2); // response
669     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UA, 0, NULL, 0);
670 }
671 
672 static int rfcomm_send_dm_pf(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
673 	uint8_t address = (1 << 0) | ((multiplexer->outgoing ^ 1) << 1) | (dlci << 2); // response
674     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_DM_PF, 0, NULL, 0);
675 }
676 
677 static int rfcomm_send_uih_fc_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t fcon) {
678     uint8_t address = (1 << 0) | (multiplexer->outgoing<< 1);
679     uint8_t payload[2];
680     uint8_t pos = 0;
681     payload[pos++] = fcon ? BT_RFCOMM_FCON_RSP : BT_RFCOMM_FCOFF_RSP;
682     payload[pos++] = (0 << 1) | 1;  // len
683     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
684 }
685 
686 // static int rfcomm_send_uih_test_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t * data, uint16_t len) {
687 //     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
688 //     uint8_t payload[2+len];
689 //     uint8_t pos = 0;
690 //     payload[pos++] = BT_RFCOMM_TEST_CMD;
691 //     payload[pos++] = (len + 1) << 1 | 1;  // len
692 //     memcpy(&payload[pos], data, len);
693 //     pos += len;
694 //     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
695 // }
696 
697 static int rfcomm_send_uih_test_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t * data, uint16_t len) {
698     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
699     uint8_t payload[2+RFCOMM_TEST_DATA_MAX_LEN];
700     uint8_t pos = 0;
701     payload[pos++] = BT_RFCOMM_TEST_RSP;
702     if (len > RFCOMM_TEST_DATA_MAX_LEN) {
703         len = RFCOMM_TEST_DATA_MAX_LEN;
704     }
705     payload[pos++] = (len << 1) | 1;  // len
706     (void)memcpy(&payload[pos], data, len);
707     pos += len;
708     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
709 }
710 
711 static int rfcomm_send_uih_msc_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t signals) {
712 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
713 	uint8_t payload[4];
714 	uint8_t pos = 0;
715 	payload[pos++] = BT_RFCOMM_MSC_CMD;
716 	payload[pos++] = (2 << 1) | 1;  // len
717 	payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
718 	payload[pos++] = signals;
719 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
720 }
721 
722 static int rfcomm_send_uih_msc_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t signals) {
723 	uint8_t address = (1 << 0) | (multiplexer->outgoing<< 1);
724 	uint8_t payload[4];
725 	uint8_t pos = 0;
726 	payload[pos++] = BT_RFCOMM_MSC_RSP;
727 	payload[pos++] = (2 << 1) | 1;  // len
728 	payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
729 	payload[pos++] = signals;
730 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
731 }
732 
733 static int rfcomm_send_uih_nsc_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t command) {
734     uint8_t address = (1 << 0) | (multiplexer->outgoing<< 1);
735     uint8_t payload[3];
736     uint8_t pos = 0;
737     payload[pos++] = BT_RFCOMM_NSC_RSP;
738     payload[pos++] = (1 << 1) | 1;  // len
739     payload[pos++] = command;
740     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
741 }
742 
743 static int rfcomm_send_uih_pn_command(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint16_t max_frame_size){
744 	uint8_t payload[10];
745 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
746 	uint8_t pos = 0;
747 	payload[pos++] = BT_RFCOMM_PN_CMD;
748 	payload[pos++] = (8 << 1) | 1;  // len
749 	payload[pos++] = dlci;
750 	payload[pos++] = 0xf0; // pre-defined for Bluetooth, see 5.5.3 of TS 07.10 Adaption for RFCOMM
751 	payload[pos++] = 0; // priority
752 	payload[pos++] = 0; // max 60 seconds ack
753 	payload[pos++] = max_frame_size & 0xff; // max framesize low
754 	payload[pos++] = max_frame_size >> 8;   // max framesize high
755 	payload[pos++] = 0x00; // number of retransmissions
756 	payload[pos++] = 0x00; // (unused error recovery window) initial number of credits
757 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
758 }
759 
760 // "The response may not change the DLCI, the priority, the convergence layer, or the timer value." rfcomm_tutorial.pdf
761 static int rfcomm_send_uih_pn_response(rfcomm_multiplexer_t *multiplexer, uint8_t dlci,
762                                        uint8_t priority, uint16_t max_frame_size){
763 	uint8_t payload[10];
764 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
765 	uint8_t pos = 0;
766 	payload[pos++] = BT_RFCOMM_PN_RSP;
767 	payload[pos++] = (8 << 1) | 1;  // len
768 	payload[pos++] = dlci;
769 	payload[pos++] = 0xe0; // pre defined for Bluetooth, see 5.5.3 of TS 07.10 Adaption for RFCOMM
770 	payload[pos++] = priority; // priority
771 	payload[pos++] = 0; // max 60 seconds ack
772 	payload[pos++] = max_frame_size & 0xff; // max framesize low
773 	payload[pos++] = max_frame_size >> 8;   // max framesize high
774 	payload[pos++] = 0x00; // number of retransmissions
775 	payload[pos++] = 0x00; // (unused error recovery window) initial number of credits
776 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
777 }
778 
779 static int rfcomm_send_uih_rls_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t line_status) {
780     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
781     uint8_t payload[4];
782     uint8_t pos = 0;
783     payload[pos++] = BT_RFCOMM_RLS_CMD;
784     payload[pos++] = (2 << 1) | 1;  // len
785     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
786     payload[pos++] = line_status;
787     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
788 }
789 
790 static int rfcomm_send_uih_rls_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t line_status) {
791     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
792     uint8_t payload[4];
793     uint8_t pos = 0;
794     payload[pos++] = BT_RFCOMM_RLS_RSP;
795     payload[pos++] = (2 << 1) | 1;  // len
796     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
797     payload[pos++] = line_status;
798     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
799 }
800 
801 static int rfcomm_send_uih_rpn_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, rfcomm_rpn_data_t *rpn_data) {
802     uint8_t payload[10];
803     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
804     uint8_t pos = 0;
805     payload[pos++] = BT_RFCOMM_RPN_CMD;
806     payload[pos++] = (8 << 1) | 1;  // len
807     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
808     payload[pos++] = rpn_data->baud_rate;
809     payload[pos++] = rpn_data->flags;
810     payload[pos++] = rpn_data->flow_control;
811     payload[pos++] = rpn_data->xon;
812     payload[pos++] = rpn_data->xoff;
813     payload[pos++] = rpn_data->parameter_mask_0;
814     payload[pos++] = rpn_data->parameter_mask_1;
815     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
816 }
817 
818 static int rfcomm_send_uih_rpn_req(rfcomm_multiplexer_t *multiplexer, uint8_t dlci) {
819     uint8_t payload[3];
820     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
821     uint8_t pos = 0;
822     payload[pos++] = BT_RFCOMM_RPN_CMD;
823     payload[pos++] = (1 << 1) | 1;  // len
824     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
825     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
826 }
827 
828 static int rfcomm_send_uih_rpn_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, rfcomm_rpn_data_t *rpn_data) {
829 	uint8_t payload[10];
830 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
831 	uint8_t pos = 0;
832 	payload[pos++] = BT_RFCOMM_RPN_RSP;
833 	payload[pos++] = (8 << 1) | 1;  // len
834 	payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
835 	payload[pos++] = rpn_data->baud_rate;
836 	payload[pos++] = rpn_data->flags;
837 	payload[pos++] = rpn_data->flow_control;
838 	payload[pos++] = rpn_data->xon;
839 	payload[pos++] = rpn_data->xoff;
840 	payload[pos++] = rpn_data->parameter_mask_0;
841 	payload[pos++] = rpn_data->parameter_mask_1;
842 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
843 }
844 
845 static void rfcomm_send_uih_credits(rfcomm_multiplexer_t *multiplexer, uint8_t dlci,  uint8_t credits){
846     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) |  (dlci << 2);
847     rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH_PF, credits, NULL, 0);
848 }
849 
850 // depending on channel state emit channel opened with status or channel closed
851 static void rfcomm_channel_emit_final_event(rfcomm_channel_t * channel, uint8_t status){
852     // emit appropriate events
853     switch(channel->state){
854         case RFCOMM_CHANNEL_OPEN:
855         case RFCOMM_CHANNEL_W4_UA_AFTER_DISC:
856             rfcomm_emit_channel_closed(channel);
857             break;
858         case RFCOMM_CHANNEL_SEND_UA_AFTER_DISC:
859             // remote didn't wait until we send the UA disc
860             // close event already emitted
861             break;
862         default:
863             rfcomm_emit_channel_opened(channel, status);
864             break;
865     }
866 }
867 
868 // MARK: RFCOMM MULTIPLEXER
869 static void rfcomm_multiplexer_stop_timer(rfcomm_multiplexer_t * multiplexer){
870     if (multiplexer->timer_active) {
871         btstack_run_loop_remove_timer(&multiplexer->timer);
872         multiplexer->timer_active = 0;
873     }
874 }
875 static void rfcomm_multiplexer_free(rfcomm_multiplexer_t * multiplexer){
876     btstack_linked_list_remove( &rfcomm_multiplexers, (btstack_linked_item_t *) multiplexer);
877     btstack_memory_rfcomm_multiplexer_free(multiplexer);
878 }
879 
880 static void rfcomm_multiplexer_finalize(rfcomm_multiplexer_t * multiplexer){
881     // remove (potential) timer
882     rfcomm_multiplexer_stop_timer(multiplexer);
883 
884     // close and remove all channels
885     btstack_linked_item_t *it = (btstack_linked_item_t *) &rfcomm_channels;
886     while (it->next){
887         rfcomm_channel_t * channel = (rfcomm_channel_t *) it->next;
888         if (channel->multiplexer == multiplexer) {
889             // emit open with status or closed
890             rfcomm_channel_emit_final_event(channel, RFCOMM_MULTIPLEXER_STOPPED);
891             // remove from list
892             it->next = it->next->next;
893             // free channel struct
894             btstack_memory_rfcomm_channel_free(channel);
895         } else {
896             it = it->next;
897         }
898     }
899 
900     // remove mutliplexer
901     rfcomm_multiplexer_free(multiplexer);
902 }
903 
904 static void rfcomm_multiplexer_timer_handler(btstack_timer_source_t *timer){
905     rfcomm_multiplexer_t * multiplexer = (rfcomm_multiplexer_t*) btstack_run_loop_get_timer_context(timer);
906     if (rfcomm_multiplexer_has_channels(multiplexer)) return;
907 
908     log_info("rfcomm_multiplexer_timer_handler timeout: shutting down multiplexer! (no channels)");
909     uint16_t l2cap_cid = multiplexer->l2cap_cid;
910     rfcomm_multiplexer_finalize(multiplexer);
911     l2cap_disconnect(l2cap_cid, 0x13);
912 }
913 
914 static void rfcomm_multiplexer_prepare_idle_timer(rfcomm_multiplexer_t * multiplexer){
915     if (multiplexer->timer_active) {
916         btstack_run_loop_remove_timer(&multiplexer->timer);
917         multiplexer->timer_active = 0;
918     }
919     if (rfcomm_multiplexer_has_channels(multiplexer)) return;
920 
921     // start idle timer for multiplexer timeout check as there are no rfcomm channels yet
922     btstack_run_loop_set_timer(&multiplexer->timer, RFCOMM_MULIPLEXER_TIMEOUT_MS);
923     btstack_run_loop_set_timer_handler(&multiplexer->timer, rfcomm_multiplexer_timer_handler);
924     btstack_run_loop_set_timer_context(&multiplexer->timer, multiplexer);
925     btstack_run_loop_add_timer(&multiplexer->timer);
926     multiplexer->timer_active = 1;
927 }
928 
929 static void rfcomm_multiplexer_opened(rfcomm_multiplexer_t *multiplexer){
930     log_info("Multiplexer up and running");
931     multiplexer->state = RFCOMM_MULTIPLEXER_OPEN;
932 
933     const rfcomm_channel_event_t event = { CH_EVT_MULTIPLEXER_READY, 0};
934 
935     // transition of channels that wait for multiplexer
936     btstack_linked_item_t *it;
937     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
938         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
939         if (channel->multiplexer != multiplexer) continue;
940         int rfcomm_channel_valid = 1;
941         rfcomm_channel_state_machine_with_channel(channel, &event, &rfcomm_channel_valid);
942         if (rfcomm_channel_valid && rfcomm_channel_ready_to_send(channel)){
943             l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
944         }
945     }
946     rfcomm_multiplexer_prepare_idle_timer(multiplexer);
947 
948     // request can send now for multiplexer if ready
949     if (rfcomm_multiplexer_ready_to_send(multiplexer)){
950         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
951     }
952 }
953 
954 static void rfcomm_handle_can_send_now(uint16_t l2cap_cid){
955 
956     log_debug("rfcomm_handle_can_send_now enter: %u", l2cap_cid);
957 
958     btstack_linked_list_iterator_t it;
959     int token_consumed = 0;
960 
961     // forward token to multiplexer
962     btstack_linked_list_iterator_init(&it, &rfcomm_multiplexers);
963     while (!token_consumed && btstack_linked_list_iterator_has_next(&it)){
964         rfcomm_multiplexer_t * multiplexer = (rfcomm_multiplexer_t *) btstack_linked_list_iterator_next(&it);
965         if (multiplexer->l2cap_cid != l2cap_cid) continue;
966         if (rfcomm_multiplexer_ready_to_send(multiplexer)){
967             log_debug("rfcomm_handle_can_send_now enter: multiplexer token");
968             token_consumed = 1;
969             rfcomm_multiplexer_state_machine(multiplexer, MULT_EV_READY_TO_SEND);
970         }
971     }
972 
973     // forward token to channel state machine
974     btstack_linked_list_iterator_init(&it, &rfcomm_channels);
975     while (!token_consumed && btstack_linked_list_iterator_has_next(&it)){
976         rfcomm_channel_t * channel = (rfcomm_channel_t *) btstack_linked_list_iterator_next(&it);
977         if (channel->multiplexer->l2cap_cid != l2cap_cid) continue;
978         // channel state machine
979         if (rfcomm_channel_ready_to_send(channel)){
980             log_debug("rfcomm_handle_can_send_now enter: channel token");
981             token_consumed = 1;
982             const rfcomm_channel_event_t event = { CH_EVT_READY_TO_SEND, 0 };
983             int rfcomm_channel_valid = 1;
984             rfcomm_channel_state_machine_with_channel(channel, &event, &rfcomm_channel_valid);
985         }
986     }
987 
988     // forward token to client
989     btstack_linked_list_iterator_init(&it, &rfcomm_channels);
990     while (!token_consumed && btstack_linked_list_iterator_has_next(&it)){
991         rfcomm_channel_t * channel = (rfcomm_channel_t *) btstack_linked_list_iterator_next(&it);
992         if (channel->multiplexer->l2cap_cid != l2cap_cid) continue;
993         // client waiting for can send now
994         if (!channel->waiting_for_can_send_now)    continue;
995         if ((channel->multiplexer->fcon & 1) == 0) continue;
996         if (!channel->credits_outgoing){
997             log_debug("rfcomm_handle_can_send_now waiting to send but no credits (ignore)");
998             continue;
999         }
1000 
1001         log_debug("rfcomm_handle_can_send_now enter: client token");
1002         token_consumed = 1;
1003         channel->waiting_for_can_send_now = 0;
1004         rfcomm_emit_can_send_now(channel);
1005     }
1006 
1007     // if token was consumed, request another one
1008     if (token_consumed) {
1009         l2cap_request_can_send_now_event(l2cap_cid);
1010     }
1011 
1012     log_debug("rfcomm_handle_can_send_now exit");
1013 }
1014 
1015 static void rfcomm_multiplexer_set_state_and_request_can_send_now_event(rfcomm_multiplexer_t * multiplexer, RFCOMM_MULTIPLEXER_STATE state){
1016     multiplexer->state = state;
1017     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1018 }
1019 
1020 /**
1021  * @return handled packet
1022  */
1023 static int rfcomm_hci_event_handler(uint8_t *packet, uint16_t size){
1024 
1025     UNUSED(size);   // ok: handling own l2cap events
1026 
1027     bd_addr_t event_addr;
1028     uint16_t  psm;
1029     uint16_t l2cap_cid;
1030     hci_con_handle_t con_handle;
1031     rfcomm_multiplexer_t *multiplexer = NULL;
1032     uint8_t status;
1033 
1034     switch (hci_event_packet_get_type(packet)) {
1035 
1036         // accept incoming rfcomm connection if no multiplexer exists yet
1037         case L2CAP_EVENT_INCOMING_CONNECTION:
1038             // data: event(8), len(8), address(48), handle (16),  psm (16), source cid(16) dest cid(16)
1039             reverse_bd_addr(&packet[2], event_addr);
1040             con_handle = little_endian_read_16(packet,  8);
1041             psm        = little_endian_read_16(packet, 10);
1042             l2cap_cid  = little_endian_read_16(packet, 12);
1043 
1044             if (psm != BLUETOOTH_PROTOCOL_RFCOMM) break;
1045 
1046             multiplexer = rfcomm_multiplexer_for_addr(event_addr);
1047 
1048             if (multiplexer) {
1049                 log_info("INCOMING_CONNECTION (l2cap_cid 0x%02x) for BLUETOOTH_PROTOCOL_RFCOMM => decline - multiplexer already exists", l2cap_cid);
1050                 l2cap_decline_connection(l2cap_cid);
1051                 return 1;
1052             }
1053 
1054             // create and inititialize new multiplexer instance (incoming)
1055             multiplexer = rfcomm_multiplexer_create_for_addr(event_addr);
1056             if (!multiplexer){
1057                 log_info("INCOMING_CONNECTION (l2cap_cid 0x%02x) for BLUETOOTH_PROTOCOL_RFCOMM => decline - no memory left", l2cap_cid);
1058                 l2cap_decline_connection(l2cap_cid);
1059                 return 1;
1060             }
1061 
1062             multiplexer->con_handle = con_handle;
1063             multiplexer->l2cap_cid = l2cap_cid;
1064             //
1065             multiplexer->state = RFCOMM_MULTIPLEXER_W4_SABM_0;
1066             log_info("L2CAP_EVENT_INCOMING_CONNECTION (l2cap_cid 0x%02x) for BLUETOOTH_PROTOCOL_RFCOMM => accept", l2cap_cid);
1067 
1068 #ifdef RFCOMM_USE_ERTM
1069             // request
1070             rfcomm_ertm_request_t request;
1071             memset(&request, 0, sizeof(rfcomm_ertm_request_t));
1072             (void)memcpy(request.addr, event_addr, 6);
1073             request.ertm_id = rfcomm_next_ertm_id();
1074             if (rfcomm_ertm_request_callback){
1075                 (*rfcomm_ertm_request_callback)(&request);
1076             }
1077             if (request.ertm_config && request.ertm_buffer && request.ertm_buffer_size){
1078                 multiplexer->ertm_id = request.ertm_id;
1079                 l2cap_accept_ertm_connection(l2cap_cid, request.ertm_config, request.ertm_buffer, request.ertm_buffer_size);
1080                 return 1;
1081             }
1082 #endif
1083 
1084             l2cap_accept_connection(l2cap_cid);
1085             return 1;
1086 
1087         // l2cap connection opened -> store l2cap_cid, remote_addr
1088         case L2CAP_EVENT_CHANNEL_OPENED:
1089 
1090             if (little_endian_read_16(packet, 11) != BLUETOOTH_PROTOCOL_RFCOMM) break;
1091 
1092             status = packet[2];
1093             log_info("L2CAP_EVENT_CHANNEL_OPENED for BLUETOOTH_PROTOCOL_RFCOMM, status %u", status);
1094 
1095             // get multiplexer for remote addr
1096             con_handle = little_endian_read_16(packet, 9);
1097             l2cap_cid = little_endian_read_16(packet, 13);
1098             reverse_bd_addr(&packet[3], event_addr);
1099             multiplexer = rfcomm_multiplexer_for_addr(event_addr);
1100             if (!multiplexer) {
1101                 log_error("L2CAP_EVENT_CHANNEL_OPENED but no multiplexer prepared");
1102                 return 1;
1103             }
1104 
1105             // on l2cap open error discard everything
1106             if (status){
1107 
1108                 // remove (potential) timer
1109                 rfcomm_multiplexer_stop_timer(multiplexer);
1110 
1111                 // mark multiplexer as shutting down
1112                 multiplexer->state = RFCOMM_MULTIPLEXER_SHUTTING_DOWN;
1113 
1114                 // emit rfcomm_channel_opened with status and free channel
1115                 // note: repeatedly go over list until full iteration causes no further change
1116                 int done;
1117                 do {
1118                     done = 1;
1119                     btstack_linked_item_t * it = (btstack_linked_item_t *) &rfcomm_channels;
1120                     while (it->next) {
1121                         rfcomm_channel_t * channel = (rfcomm_channel_t *) it->next;
1122                         if (channel->multiplexer == multiplexer){
1123                             done = 0;
1124                             rfcomm_emit_channel_opened(channel, status);
1125                             btstack_linked_list_remove(&rfcomm_channels, (btstack_linked_item_t *) channel);
1126                             btstack_memory_rfcomm_channel_free(channel);
1127                             break;
1128                         } else {
1129                             it = it->next;
1130                         }
1131                     }
1132                 } while (!done);
1133 
1134                 // free multiplexer
1135                 rfcomm_multiplexer_free(multiplexer);
1136                 return 1;
1137             }
1138 
1139             // following could be: rfcom_multiplexer_state_machein(..., EVENT_L2CAP_OPENED)
1140 
1141             // set max frame size based on l2cap MTU
1142             multiplexer->max_frame_size = rfcomm_max_frame_size_for_l2cap_mtu(little_endian_read_16(packet, 17));
1143 
1144             if (multiplexer->state == RFCOMM_MULTIPLEXER_W4_CONNECT) {
1145                 log_info("L2CAP_EVENT_CHANNEL_OPENED: outgoing connection");
1146                 // wrong remote addr
1147                 if (bd_addr_cmp(event_addr, multiplexer->remote_addr)) break;
1148                 multiplexer->l2cap_cid = l2cap_cid;
1149                 multiplexer->con_handle = con_handle;
1150                 // send SABM #0
1151                 rfcomm_multiplexer_set_state_and_request_can_send_now_event(multiplexer, RFCOMM_MULTIPLEXER_SEND_SABM_0);
1152 
1153             }
1154             return 1;
1155 
1156             // l2cap disconnect -> state = RFCOMM_MULTIPLEXER_CLOSED;
1157 
1158         // Notify channel packet handler if they can send now
1159         case L2CAP_EVENT_CAN_SEND_NOW:
1160             l2cap_cid = l2cap_event_can_send_now_get_local_cid(packet);
1161             rfcomm_handle_can_send_now(l2cap_cid);
1162             return 1;
1163 
1164         case L2CAP_EVENT_CHANNEL_CLOSED:
1165             // data: event (8), len(8), channel (16)
1166             l2cap_cid = little_endian_read_16(packet, 2);
1167             multiplexer = rfcomm_multiplexer_for_l2cap_cid(l2cap_cid);
1168             log_info("L2CAP_EVENT_CHANNEL_CLOSED cid 0x%0x, mult %p", l2cap_cid, multiplexer);
1169             if (!multiplexer) break;
1170             log_info("L2CAP_EVENT_CHANNEL_CLOSED state %u", multiplexer->state);
1171             // no need to call l2cap_disconnect here, as it's already closed
1172             rfcomm_multiplexer_finalize(multiplexer);
1173             return 1;
1174 
1175 #ifdef RFCOMM_USE_ERTM
1176         case L2CAP_EVENT_ERTM_BUFFER_RELEASED:
1177             l2cap_cid = l2cap_event_ertm_buffer_released_get_local_cid(packet);
1178             multiplexer = rfcomm_multiplexer_for_l2cap_cid(l2cap_cid);
1179             if (multiplexer) {
1180                 log_info("buffer for ertm id %u released", multiplexer->ertm_id);
1181                 if (rfcomm_ertm_released_callback){
1182                     (*rfcomm_ertm_released_callback)(multiplexer->ertm_id);
1183                 }
1184             }
1185             break;
1186 #endif
1187 
1188         default:
1189             break;
1190     }
1191     return 0;
1192 }
1193 
1194 static int rfcomm_multiplexer_l2cap_packet_handler(uint16_t channel, uint8_t *packet, uint16_t size){
1195     // get or create a multiplexer for a certain device
1196     rfcomm_multiplexer_t *multiplexer = rfcomm_multiplexer_for_l2cap_cid(channel);
1197     if (!multiplexer) return 0;
1198 
1199     uint16_t l2cap_cid = multiplexer->l2cap_cid;
1200 
1201 	// but only care for multiplexer control channel
1202     uint8_t frame_dlci = packet[0] >> 2;
1203     if (frame_dlci) return 0;
1204     const uint8_t length_offset = (packet[2] & 1) ^ 1;  // to be used for pos >= 3
1205     const uint8_t credit_offset = ((packet[1] & BT_RFCOMM_UIH_PF) == BT_RFCOMM_UIH_PF) ? 1 : 0;   // credits for uih_pf frames
1206     const uint8_t payload_offset = 3 + length_offset + credit_offset;
1207     switch (packet[1]){
1208 
1209         case BT_RFCOMM_SABM:
1210             if (multiplexer->state == RFCOMM_MULTIPLEXER_W4_SABM_0){
1211                 log_info("Received SABM #0");
1212                 multiplexer->outgoing = 0;
1213                 rfcomm_multiplexer_set_state_and_request_can_send_now_event(multiplexer, RFCOMM_MULTIPLEXER_SEND_UA_0);
1214                 return 1;
1215             }
1216             break;
1217 
1218         case BT_RFCOMM_UA:
1219             if (multiplexer->state == RFCOMM_MULTIPLEXER_W4_UA_0) {
1220                 // UA #0 -> send UA #0, state = RFCOMM_MULTIPLEXER_OPEN
1221                 log_info("Received UA #0 ");
1222                 rfcomm_multiplexer_opened(multiplexer);
1223                 return 1;
1224             }
1225             break;
1226 
1227         case BT_RFCOMM_DISC:
1228             // DISC #0 -> send UA #0, close multiplexer
1229             log_info("Received DISC #0, (ougoing = %u)", multiplexer->outgoing);
1230             rfcomm_multiplexer_set_state_and_request_can_send_now_event(multiplexer, RFCOMM_MULTIPLEXER_SEND_UA_0_AND_DISC);
1231             return 1;
1232 
1233         case BT_RFCOMM_DM:
1234             // DM #0 - we shouldn't get this, just give up
1235             log_info("Received DM #0");
1236             log_info("-> Closing down multiplexer");
1237             rfcomm_multiplexer_finalize(multiplexer);
1238             l2cap_disconnect(l2cap_cid, 0x13);
1239             return 1;
1240 
1241         case BT_RFCOMM_UIH:
1242             if (packet[payload_offset] == BT_RFCOMM_CLD_CMD){
1243                 // Multiplexer close down (CLD) -> close mutliplexer
1244                 log_info("Received Multiplexer close down command");
1245                 log_info("-> Closing down multiplexer");
1246                 rfcomm_multiplexer_finalize(multiplexer);
1247                 l2cap_disconnect(l2cap_cid, 0x13);
1248                 return 1;
1249             }
1250             switch (packet[payload_offset]){
1251                 case BT_RFCOMM_CLD_CMD:
1252                      // Multiplexer close down (CLD) -> close mutliplexer
1253                     log_info("Received Multiplexer close down command");
1254                     log_info("-> Closing down multiplexer");
1255                     rfcomm_multiplexer_finalize(multiplexer);
1256                     l2cap_disconnect(l2cap_cid, 0x13);
1257                     return 1;
1258 
1259                 case BT_RFCOMM_FCON_CMD:
1260                     multiplexer->fcon = 0x81;
1261                     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1262                     return 1;
1263 
1264                 case BT_RFCOMM_FCOFF_CMD:
1265                     multiplexer->fcon = 0x80;
1266                     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1267                     return 1;
1268 
1269                 case BT_RFCOMM_TEST_CMD: {
1270                     log_info("Received test command");
1271                     int len = packet[payload_offset+1] >> 1; // length < 125
1272                     if (len > RFCOMM_TEST_DATA_MAX_LEN){
1273                         len = RFCOMM_TEST_DATA_MAX_LEN;
1274                     }
1275                     len = btstack_min(len, size - 1 - payload_offset);  // avoid information leak
1276                     multiplexer->test_data_len = len;
1277                     (void)memcpy(multiplexer->test_data,
1278                                  &packet[payload_offset + 2], len);
1279                     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1280                     return 1;
1281                 }
1282                 default:
1283                     break;
1284             }
1285             break;
1286 
1287         default:
1288             break;
1289 
1290     }
1291     return 0;
1292 }
1293 
1294 static int rfcomm_multiplexer_ready_to_send(rfcomm_multiplexer_t * multiplexer){
1295     if (multiplexer->send_dm_for_dlci) return 1;
1296     if (multiplexer->nsc_command) return 1;
1297     if (multiplexer->fcon & 0x80) return 1;
1298     switch (multiplexer->state){
1299         case RFCOMM_MULTIPLEXER_SEND_SABM_0:
1300         case RFCOMM_MULTIPLEXER_SEND_UA_0:
1301         case RFCOMM_MULTIPLEXER_SEND_UA_0_AND_DISC:
1302             return 1;
1303         case RFCOMM_MULTIPLEXER_OPEN:
1304             if (multiplexer->test_data_len) {
1305                 return 1;
1306             }
1307             break;
1308         default:
1309             break;
1310     }
1311     return 0;
1312 }
1313 
1314 static void rfcomm_multiplexer_state_machine(rfcomm_multiplexer_t * multiplexer, RFCOMM_MULTIPLEXER_EVENT event){
1315 
1316     if (event != MULT_EV_READY_TO_SEND) return;
1317 
1318     uint16_t l2cap_cid = multiplexer->l2cap_cid;
1319 
1320     // process stored DM responses
1321     if (multiplexer->send_dm_for_dlci){
1322         uint8_t dlci = multiplexer->send_dm_for_dlci;
1323         multiplexer->send_dm_for_dlci = 0;
1324         rfcomm_send_dm_pf(multiplexer, dlci);
1325         return;
1326     }
1327 
1328     if (multiplexer->nsc_command){
1329         uint8_t command = multiplexer->nsc_command;
1330         multiplexer->nsc_command = 0;
1331         rfcomm_send_uih_nsc_rsp(multiplexer, command);
1332         return;
1333     }
1334 
1335     if (multiplexer->fcon & 0x80){
1336         multiplexer->fcon &= 0x01;
1337         rfcomm_send_uih_fc_rsp(multiplexer, multiplexer->fcon);
1338 
1339         if (multiplexer->fcon == 0) return;
1340         // trigger client to send again after sending FCon Response
1341         rfcomm_notify_channel_can_send();
1342         return;
1343     }
1344 
1345     switch (multiplexer->state) {
1346         case RFCOMM_MULTIPLEXER_SEND_SABM_0:
1347             log_info("Sending SABM #0 - (multi 0x%p)", multiplexer);
1348             multiplexer->state = RFCOMM_MULTIPLEXER_W4_UA_0;
1349             rfcomm_send_sabm(multiplexer, 0);
1350             break;
1351         case RFCOMM_MULTIPLEXER_SEND_UA_0:
1352             log_info("Sending UA #0");
1353             multiplexer->state = RFCOMM_MULTIPLEXER_OPEN;
1354             rfcomm_send_ua(multiplexer, 0);
1355 
1356             rfcomm_multiplexer_opened(multiplexer);
1357             break;
1358         case RFCOMM_MULTIPLEXER_SEND_UA_0_AND_DISC:
1359             log_info("Sending UA #0");
1360             log_info("Closing down multiplexer");
1361             multiplexer->state = RFCOMM_MULTIPLEXER_CLOSED;
1362             rfcomm_send_ua(multiplexer, 0);
1363 
1364             rfcomm_multiplexer_finalize(multiplexer);
1365             l2cap_disconnect(l2cap_cid, 0x13);
1366             break;
1367         case RFCOMM_MULTIPLEXER_OPEN:
1368             // respond to test command
1369             if (multiplexer->test_data_len){
1370                 int len = multiplexer->test_data_len;
1371                 log_info("Sending TEST Response with %u bytes", len);
1372                 multiplexer->test_data_len = 0;
1373                 rfcomm_send_uih_test_rsp(multiplexer, multiplexer->test_data, len);
1374                 return;
1375             }
1376             break;
1377         default:
1378             break;
1379     }
1380 }
1381 
1382 // MARK: RFCOMM CHANNEL
1383 
1384 static void rfcomm_channel_send_credits(rfcomm_channel_t *channel, uint8_t credits){
1385     channel->credits_incoming += credits;
1386     rfcomm_send_uih_credits(channel->multiplexer, channel->dlci, credits);
1387 }
1388 
1389 static int rfcomm_channel_can_send(rfcomm_channel_t * channel){
1390     if (!channel->credits_outgoing) return 0;
1391     if ((channel->multiplexer->fcon & 1) == 0) return 0;
1392     return l2cap_can_send_packet_now(channel->multiplexer->l2cap_cid);
1393 }
1394 
1395 static void rfcomm_channel_opened(rfcomm_channel_t *rfChannel){
1396 
1397     log_info("rfcomm_channel_opened!");
1398 
1399     rfChannel->state = RFCOMM_CHANNEL_OPEN;
1400     rfcomm_emit_channel_opened(rfChannel, 0);
1401     rfcomm_emit_port_configuration(rfChannel);
1402 
1403     // remove (potential) timer
1404     rfcomm_multiplexer_t *multiplexer = rfChannel->multiplexer;
1405     if (multiplexer->timer_active) {
1406         btstack_run_loop_remove_timer(&multiplexer->timer);
1407         multiplexer->timer_active = 0;
1408     }
1409     // hack for problem detecting authentication failure
1410     multiplexer->at_least_one_connection = 1;
1411 
1412     // request can send now if channel ready
1413     if (rfcomm_channel_ready_to_send(rfChannel)){
1414         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1415     }
1416 }
1417 
1418 static void rfcomm_channel_packet_handler_uih(rfcomm_multiplexer_t *multiplexer, uint8_t * packet, uint16_t size){
1419     const uint8_t frame_dlci = packet[0] >> 2;
1420     const uint8_t length_offset = (packet[2] & 1) ^ 1;  // to be used for pos >= 3
1421     const uint8_t credit_offset = ((packet[1] & BT_RFCOMM_UIH_PF) == BT_RFCOMM_UIH_PF) ? 1 : 0;   // credits for uih_pf frames
1422     const uint8_t payload_offset = 3 + length_offset + credit_offset;
1423     int request_can_send_now = 0;
1424 
1425     rfcomm_channel_t * channel = rfcomm_channel_for_multiplexer_and_dlci(multiplexer, frame_dlci);
1426     if (!channel) return;
1427 
1428     // handle new outgoing credits
1429     if (packet[1] == BT_RFCOMM_UIH_PF) {
1430 
1431         // add them
1432         uint16_t new_credits = packet[3+length_offset];
1433         channel->credits_outgoing += new_credits;
1434         log_info( "RFCOMM data UIH_PF, new credits channel 0x%02x: %u, now %u", channel->rfcomm_cid, new_credits, channel->credits_outgoing);
1435 
1436         // notify channel statemachine
1437         rfcomm_channel_event_t channel_event = { CH_EVT_RCVD_CREDITS, 0 };
1438         log_debug("rfcomm_channel_state_machine_with_channel, waiting_for_can_send_now %u", channel->waiting_for_can_send_now);
1439         int rfcomm_channel_valid = 1;
1440         rfcomm_channel_state_machine_with_channel(channel, &channel_event, &rfcomm_channel_valid);
1441         if (rfcomm_channel_valid){
1442             if (rfcomm_channel_ready_to_send(channel) || channel->waiting_for_can_send_now){
1443                 request_can_send_now = 1;
1444             }
1445         }
1446     }
1447 
1448     // contains payload?
1449     if ((size - 1) > payload_offset){
1450 
1451         // log_info( "RFCOMM data UIH_PF, size %u, channel %p", size-payload_offset-1, rfChannel->connection);
1452 
1453         // decrease incoming credit counter
1454         if (channel->credits_incoming > 0){
1455             channel->credits_incoming--;
1456         }
1457 
1458         // deliver payload
1459         (channel->packet_handler)(RFCOMM_DATA_PACKET, channel->rfcomm_cid,
1460                               &packet[payload_offset], size-payload_offset-1);
1461     }
1462 
1463     // automatically provide new credits to remote device, if no incoming flow control
1464     if (!channel->incoming_flow_control && (channel->credits_incoming < 5)){
1465         channel->new_credits_incoming = RFCOMM_CREDITS;
1466         request_can_send_now = 1;
1467     }
1468 
1469     if (request_can_send_now){
1470         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1471     }
1472 }
1473 
1474 static void rfcomm_channel_accept_pn(rfcomm_channel_t *channel, rfcomm_channel_event_pn_t *event){
1475     // priority of client request
1476     channel->pn_priority = event->priority;
1477 
1478     // new credits
1479     channel->credits_outgoing = event->credits_outgoing;
1480 
1481     // negotiate max frame size
1482     if (channel->max_frame_size > channel->multiplexer->max_frame_size) {
1483         channel->max_frame_size = channel->multiplexer->max_frame_size;
1484     }
1485     if (channel->max_frame_size > event->max_frame_size) {
1486         channel->max_frame_size = event->max_frame_size;
1487     }
1488 
1489 }
1490 
1491 static void rfcomm_channel_finalize(rfcomm_channel_t *channel){
1492 
1493     rfcomm_multiplexer_t *multiplexer = channel->multiplexer;
1494 
1495     // remove from list
1496     btstack_linked_list_remove( &rfcomm_channels, (btstack_linked_item_t *) channel);
1497 
1498     // free channel
1499     btstack_memory_rfcomm_channel_free(channel);
1500 
1501     // update multiplexer timeout after channel was removed from list
1502     rfcomm_multiplexer_prepare_idle_timer(multiplexer);
1503 }
1504 
1505 static void rfcomm_channel_state_machine_with_dlci(rfcomm_multiplexer_t * multiplexer, uint8_t dlci, const rfcomm_channel_event_t *event){
1506 
1507     // TODO: if client max frame size is smaller than RFCOMM_DEFAULT_SIZE, send PN
1508 
1509 
1510     // lookup existing channel
1511     rfcomm_channel_t * channel = rfcomm_channel_for_multiplexer_and_dlci(multiplexer, dlci);
1512 
1513     // log_info("rfcomm_channel_state_machine_with_dlci lookup dlci #%u = 0x%08x - event %u", dlci, (int) channel, event->type);
1514 
1515     if (channel) {
1516         int rfcomm_channel_valid = 1;
1517         rfcomm_channel_state_machine_with_channel(channel, event, &rfcomm_channel_valid);
1518         if (rfcomm_channel_valid && rfcomm_channel_ready_to_send(channel)){
1519             l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1520         }
1521         return;
1522     }
1523 
1524     // service registered?
1525     rfcomm_service_t * service = rfcomm_service_for_channel(dlci >> 1);
1526     // log_info("rfcomm_channel_state_machine_with_dlci service dlci #%u = 0x%08x", dlci, (int) service);
1527     if (!service) {
1528         // discard request by sending disconnected mode
1529         multiplexer->send_dm_for_dlci = dlci;
1530         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1531         return;
1532     }
1533 
1534     // create channel for some events
1535     switch (event->type) {
1536         case CH_EVT_RCVD_SABM:
1537         case CH_EVT_RCVD_PN:
1538         case CH_EVT_RCVD_RPN_REQ:
1539         case CH_EVT_RCVD_RPN_CMD:
1540             // setup incoming channel
1541             channel = rfcomm_channel_create(multiplexer, service, dlci >> 1);
1542             if (!channel){
1543                 // discard request by sending disconnected mode
1544                 multiplexer->send_dm_for_dlci = dlci;
1545                 l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1546             }
1547             break;
1548         default:
1549             break;
1550     }
1551 
1552     if (!channel) {
1553         // discard request by sending disconnected mode
1554         multiplexer->send_dm_for_dlci = dlci;
1555         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1556         return;
1557     }
1558 
1559     int rfcomm_channel_valid = 1;
1560     rfcomm_channel_state_machine_with_channel(channel, event, &rfcomm_channel_valid);
1561     if (rfcomm_channel_valid && rfcomm_channel_ready_to_send(channel)){
1562         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1563     }
1564 }
1565 
1566 static void rfcomm_channel_packet_handler(rfcomm_multiplexer_t * multiplexer,  uint8_t *packet, uint16_t size){
1567 
1568     UNUSED(size);   // ok: fixed format messages
1569 
1570     // rfcomm: (0) addr [76543 server channel] [2 direction: initiator uses 1] [1 C/R: CMD by initiator = 1] [0 EA=1]
1571     const uint8_t frame_dlci = packet[0] >> 2;
1572     uint8_t message_dlci; // used by commands in UIH(_PF) packets
1573 	uint8_t message_len;  //   "
1574 
1575     // rfcomm: (1) command/control
1576     // -- credits_offset = 1 if command == BT_RFCOMM_UIH_PF
1577     const uint8_t credit_offset = ((packet[1] & BT_RFCOMM_UIH_PF) == BT_RFCOMM_UIH_PF) ? 1 : 0;   // credits for uih_pf frames
1578     // rfcomm: (2) length. if bit 0 is cleared, 2 byte length is used. (little endian)
1579     const uint8_t length_offset = (packet[2] & 1) ^ 1;  // to be used for pos >= 3
1580     // rfcomm: (3+length_offset) credits if credits_offset == 1
1581     // rfcomm: (3+length_offest+credits_offset)
1582     const uint8_t payload_offset = 3 + length_offset + credit_offset;
1583 
1584     rfcomm_channel_event_t event;
1585     rfcomm_channel_event_pn_t event_pn;
1586     rfcomm_channel_event_rpn_t event_rpn;
1587     rfcomm_channel_event_msc_t event_msc;
1588 
1589     // switch by rfcomm message type
1590     switch(packet[1]) {
1591 
1592         case BT_RFCOMM_SABM:
1593             event.type = CH_EVT_RCVD_SABM;
1594             log_info("Received SABM #%u", frame_dlci);
1595             rfcomm_channel_state_machine_with_dlci(multiplexer, frame_dlci, &event);
1596             break;
1597 
1598         case BT_RFCOMM_UA:
1599             event.type = CH_EVT_RCVD_UA;
1600             log_info("Received UA #%u",frame_dlci);
1601             rfcomm_channel_state_machine_with_dlci(multiplexer, frame_dlci, &event);
1602             break;
1603 
1604         case BT_RFCOMM_DISC:
1605             event.type = CH_EVT_RCVD_DISC;
1606             rfcomm_channel_state_machine_with_dlci(multiplexer, frame_dlci, &event);
1607             break;
1608 
1609         case BT_RFCOMM_DM:
1610         case BT_RFCOMM_DM_PF:
1611             event.type = CH_EVT_RCVD_DM;
1612             rfcomm_channel_state_machine_with_dlci(multiplexer, frame_dlci, &event);
1613             break;
1614 
1615         case BT_RFCOMM_UIH_PF:
1616         case BT_RFCOMM_UIH:
1617 
1618             message_len  = packet[payload_offset+1] >> 1;
1619 
1620             switch (packet[payload_offset]) {
1621                 case BT_RFCOMM_PN_CMD:
1622                     message_dlci = packet[payload_offset+2];
1623                     event_pn.super.type = CH_EVT_RCVD_PN;
1624                     event_pn.priority = packet[payload_offset+4];
1625                     event_pn.max_frame_size = little_endian_read_16(packet, payload_offset+6);
1626                     event_pn.credits_outgoing = packet[payload_offset+9];
1627                     log_info("Received UIH Parameter Negotiation Command for #%u, credits %u",
1628                         message_dlci, event_pn.credits_outgoing);
1629                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_pn);
1630                     break;
1631 
1632                 case BT_RFCOMM_PN_RSP:
1633                     message_dlci = packet[payload_offset+2];
1634                     event_pn.super.type = CH_EVT_RCVD_PN_RSP;
1635                     event_pn.priority = packet[payload_offset+4];
1636                     event_pn.max_frame_size = little_endian_read_16(packet, payload_offset+6);
1637                     event_pn.credits_outgoing = packet[payload_offset+9];
1638                     log_info("Received UIH Parameter Negotiation Response max frame %u, credits %u",
1639                             event_pn.max_frame_size, event_pn.credits_outgoing);
1640                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_pn);
1641                     break;
1642 
1643                 case BT_RFCOMM_MSC_CMD:
1644                     message_dlci = packet[payload_offset+2] >> 2;
1645                     event_msc.super.type = CH_EVT_RCVD_MSC_CMD;
1646                     event_msc.modem_status = packet[payload_offset+3];
1647                     log_info("Received MSC CMD for #%u, ", message_dlci);
1648                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_msc);
1649                     break;
1650 
1651                 case BT_RFCOMM_MSC_RSP:
1652                     message_dlci = packet[payload_offset+2] >> 2;
1653                     event.type = CH_EVT_RCVD_MSC_RSP;
1654                     log_info("Received MSC RSP for #%u", message_dlci);
1655                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, &event);
1656                     break;
1657 
1658                 case BT_RFCOMM_RPN_CMD:
1659                     message_dlci = packet[payload_offset+2] >> 2;
1660                     switch (message_len){
1661                         case 1:
1662                             log_info("Received Remote Port Negotiation Request for #%u", message_dlci);
1663                             event.type = CH_EVT_RCVD_RPN_REQ;
1664                             rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, &event);
1665                             break;
1666                         case 8:
1667                             log_info("Received Remote Port Negotiation Update for #%u", message_dlci);
1668                             event_rpn.super.type = CH_EVT_RCVD_RPN_CMD;
1669                             event_rpn.data = *(rfcomm_rpn_data_t*) &packet[payload_offset+3];
1670                             rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_rpn);
1671                             break;
1672                         default:
1673                             break;
1674                     }
1675                     break;
1676 
1677                 case BT_RFCOMM_RPN_RSP:
1678                     log_info("Received RPN response");
1679                     break;
1680 
1681                 case BT_RFCOMM_RLS_CMD: {
1682                     log_info("Received RLS command");
1683                     message_dlci = packet[payload_offset+2] >> 2;
1684                     rfcomm_channel_event_rls_t event_rls;
1685                     event_rls.super.type = CH_EVT_RCVD_RLS_CMD;
1686                     event_rls.line_status = packet[payload_offset+3];
1687                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_rls);
1688                     break;
1689                 }
1690 
1691                 case BT_RFCOMM_RLS_RSP:
1692                     log_info("Received RLS response");
1693                     break;
1694 
1695                 // Following commands are handled by rfcomm_multiplexer_l2cap_packet_handler
1696                 // case BT_RFCOMM_TEST_CMD:
1697                 // case BT_RFCOMM_FCOFF_CMD:
1698                 // case BT_RFCOMM_FCON_CMD:
1699                 // everything else is an not supported command
1700                 default: {
1701                     log_error("Received unknown UIH command packet - 0x%02x", packet[payload_offset]);
1702                     multiplexer->nsc_command = packet[payload_offset];
1703                     break;
1704                 }
1705             }
1706             break;
1707 
1708         default:
1709             log_error("Received unknown RFCOMM message type %x", packet[1]);
1710             break;
1711     }
1712 
1713     // trigger next action - example W4_PN_RSP: transition to SEND_SABM which only depends on "can send"
1714     if (rfcomm_multiplexer_ready_to_send(multiplexer)){
1715         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1716     }
1717 }
1718 
1719 static void rfcomm_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
1720 
1721     if (packet_type == HCI_EVENT_PACKET){
1722         rfcomm_hci_event_handler(packet, size);
1723         return;
1724     }
1725 
1726     // we only handle l2cap packets for:
1727     if (packet_type != L2CAP_DATA_PACKET) return;
1728 
1729     //  - multiplexer itself
1730     int handled = rfcomm_multiplexer_l2cap_packet_handler(channel, packet, size);
1731 
1732     if (handled) return;
1733 
1734     // - channel over open mutliplexer
1735     rfcomm_multiplexer_t * multiplexer = rfcomm_multiplexer_for_l2cap_cid(channel);
1736     if ( (multiplexer == NULL) || (multiplexer->state != RFCOMM_MULTIPLEXER_OPEN)) return;
1737 
1738     // channel data ?
1739     // rfcomm: (0) addr [76543 server channel] [2 direction: initiator uses 1] [1 C/R: CMD by initiator = 1] [0 EA=1]
1740     const uint8_t frame_dlci = packet[0] >> 2;
1741 
1742     if (frame_dlci && ((packet[1] == BT_RFCOMM_UIH) || (packet[1] == BT_RFCOMM_UIH_PF))) {
1743         rfcomm_channel_packet_handler_uih(multiplexer, packet, size);
1744         return;
1745     }
1746 
1747     rfcomm_channel_packet_handler(multiplexer, packet, size);
1748 }
1749 
1750 static int rfcomm_channel_ready_for_open(rfcomm_channel_t *channel){
1751     // note: exchanging MSC isn't neccessary to consider channel open
1752     // note: having outgoing credits is also not necessary to consider channel open
1753     // 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);
1754     // if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SENT_MSC_RSP) == 0) return 0;
1755     // if (channel->credits_outgoing == 0) return 0;
1756     log_info("rfcomm_channel_ready_for_open state %u, flags needed %04x, current %04x, rf credits %u",
1757          channel->state, RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_RSP, channel->state_var, channel->credits_outgoing);
1758     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_RSP) == 0) return 0;
1759     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SENT_CREDITS) == 0) return 0;
1760 
1761     return 1;
1762 }
1763 
1764 static int rfcomm_channel_ready_for_incoming_dlc_setup(rfcomm_channel_t * channel){
1765     log_info("rfcomm_channel_ready_for_incoming_dlc_setup state var %04x", channel->state_var);
1766     // Client accept and SABM/UA is required, PN RSP is needed if PN was received
1767     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_CLIENT_ACCEPTED) == 0) return 0;
1768     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_SABM      ) == 0) return 0;
1769     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_UA        ) != 0) return 0;
1770     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP    ) != 0) return 0;
1771     return 1;
1772 }
1773 
1774 inline static void rfcomm_channel_state_add(rfcomm_channel_t *channel, RFCOMM_CHANNEL_STATE_VAR event){
1775     channel->state_var = (RFCOMM_CHANNEL_STATE_VAR) (channel->state_var | event);
1776 }
1777 inline static void rfcomm_channel_state_remove(rfcomm_channel_t *channel, RFCOMM_CHANNEL_STATE_VAR event){
1778     channel->state_var = (RFCOMM_CHANNEL_STATE_VAR) (channel->state_var & ~event);
1779 }
1780 
1781 static int rfcomm_channel_ready_to_send(rfcomm_channel_t * channel){
1782     switch (channel->state){
1783         case RFCOMM_CHANNEL_SEND_UIH_PN:
1784             log_debug("ch-ready: state %u", channel->state);
1785             return 1;
1786         case RFCOMM_CHANNEL_SEND_SABM_W4_UA:
1787             log_debug("ch-ready: state %u", channel->state);
1788             return 1;
1789         case RFCOMM_CHANNEL_SEND_UA_AFTER_DISC:
1790             log_debug("ch-ready: state %u", channel->state);
1791             return 1;
1792         case RFCOMM_CHANNEL_SEND_DISC:
1793             log_debug("ch-ready: state %u", channel->state);
1794             return 1;
1795         case RFCOMM_CHANNEL_SEND_DM:
1796             log_debug("ch-ready: state %u", channel->state);
1797             return 1;
1798         case RFCOMM_CHANNEL_OPEN:
1799             if (channel->new_credits_incoming) {
1800                 log_debug("ch-ready: channel open & new_credits_incoming") ;
1801                 return 1;
1802             }
1803             break;
1804         case RFCOMM_CHANNEL_DLC_SETUP:
1805             if (channel->state_var & (
1806                 RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD  |
1807                 RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS
1808              )) {
1809                 log_debug("ch-ready: channel dlc setup & send msc cmd or send credits") ;
1810                 return 1;
1811             }
1812             break;
1813 
1814         default:
1815             break;
1816     }
1817 
1818     if (channel->state_var & (
1819         RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP   |
1820         RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_INFO |
1821         RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RSP  |
1822         RFCOMM_CHANNEL_STATE_VAR_SEND_UA       |
1823         RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP
1824                              )){
1825         log_debug("ch-ready: state %x, state var %x", channel->state, channel->state_var);
1826         return 1;
1827     }
1828 
1829     if (channel->rls_line_status != RFCOMM_RLS_STATUS_INVALID) {
1830         log_debug("ch-ready: rls_line_status");
1831         return 1;
1832     }
1833 
1834     return 0;
1835 }
1836 
1837 
1838 static void rfcomm_channel_state_machine_with_channel(rfcomm_channel_t *channel, const rfcomm_channel_event_t *event, int * out_channel_valid){
1839 
1840     // log_info("rfcomm_channel_state_machine_with_channel: state %u, state_var %04x, event %u", channel->state, channel->state_var ,event->type);
1841 
1842     // channel != NULL -> channel valid
1843     *out_channel_valid = 1;
1844 
1845     rfcomm_multiplexer_t *multiplexer = channel->multiplexer;
1846 
1847     // TODO: integrate in common switch
1848     if (event->type == CH_EVT_RCVD_DISC){
1849         rfcomm_emit_channel_closed(channel);
1850         channel->state = RFCOMM_CHANNEL_SEND_UA_AFTER_DISC;
1851         return;
1852     }
1853 
1854     // TODO: integrate in common switch
1855     if (event->type == CH_EVT_RCVD_DM){
1856         log_info("Received DM message for #%u", channel->dlci);
1857         log_info("-> Closing channel locally for #%u", channel->dlci);
1858         rfcomm_channel_emit_final_event(channel, ERROR_CODE_CONNECTION_REJECTED_DUE_TO_LIMITED_RESOURCES);
1859         rfcomm_channel_finalize(channel);
1860         *out_channel_valid = 0;
1861         return;
1862     }
1863 
1864     // remote port negotiation command - just accept everything for now
1865     //
1866     // "The RPN command can be used before a new DLC is opened and should be used whenever the port settings change."
1867     // "The RPN command is specified as optional in TS 07.10, but it is mandatory to recognize and respond to it in RFCOMM.
1868     //   (Although the handling of individual settings are implementation-dependent.)"
1869     //
1870 
1871     // TODO: integrate in common switch
1872     if (event->type == CH_EVT_RCVD_RPN_CMD){
1873         // control port parameters
1874         rfcomm_channel_event_rpn_t *event_rpn = (rfcomm_channel_event_rpn_t*) event;
1875         rfcomm_rpn_data_update(&channel->rpn_data, &event_rpn->data);
1876         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RSP);
1877         // notify client about new settings
1878         rfcomm_emit_port_configuration(channel);
1879         return;
1880     }
1881 
1882     // TODO: integrate in common switch
1883     if (event->type == CH_EVT_RCVD_RPN_REQ){
1884         // no values got accepted (no values have beens sent)
1885         channel->rpn_data.parameter_mask_0 = 0x00;
1886         channel->rpn_data.parameter_mask_1 = 0x00;
1887         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RSP);
1888         return;
1889     }
1890 
1891     if (event->type == CH_EVT_RCVD_RLS_CMD){
1892         rfcomm_channel_event_rls_t * event_rls = (rfcomm_channel_event_rls_t*) event;
1893         channel->rls_line_status = event_rls->line_status & 0x0f;
1894         log_info("CH_EVT_RCVD_RLS_CMD setting line status to 0x%0x", channel->rls_line_status);
1895         rfcomm_emit_remote_line_status(channel, event_rls->line_status);
1896         return;
1897     }
1898 
1899     // TODO: integrate in common switch
1900     if (event->type == CH_EVT_READY_TO_SEND){
1901         if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RSP){
1902             log_info("Sending Remote Port Negotiation RSP for #%u", channel->dlci);
1903             rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RSP);
1904             rfcomm_send_uih_rpn_rsp(multiplexer, channel->dlci, &channel->rpn_data);
1905             return;
1906         }
1907         if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP){
1908             log_info("Sending MSC RSP for #%u", channel->dlci);
1909             rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP);
1910             rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SENT_MSC_RSP);
1911             rfcomm_send_uih_msc_rsp(multiplexer, channel->dlci, 0x8d);  // ea=1,fc=0,rtc=1,rtr=1,ic=0,dv=1
1912             return;
1913         }
1914         if (channel->rls_line_status != RFCOMM_RLS_STATUS_INVALID){
1915             log_info("Sending RLS RSP 0x%0x", channel->rls_line_status);
1916             uint8_t line_status = channel->rls_line_status;
1917             channel->rls_line_status = RFCOMM_RLS_STATUS_INVALID;
1918             rfcomm_send_uih_rls_rsp(multiplexer, channel->dlci, line_status);
1919             return;
1920         }
1921     }
1922 
1923     // emit MSC status to app
1924     if (event->type == CH_EVT_RCVD_MSC_CMD){
1925         // notify client about new settings
1926         rfcomm_channel_event_msc_t *event_msc = (rfcomm_channel_event_msc_t*) event;
1927         uint8_t modem_status_event[2+1];
1928         modem_status_event[0] = RFCOMM_EVENT_REMOTE_MODEM_STATUS;
1929         modem_status_event[1] = 1;
1930         modem_status_event[2] = event_msc->modem_status;
1931         (channel->packet_handler)(HCI_EVENT_PACKET, channel->rfcomm_cid, (uint8_t*)&modem_status_event, sizeof(modem_status_event));
1932         // no return, MSC_CMD will be handled by state machine below
1933     }
1934 
1935     rfcomm_channel_event_pn_t * event_pn = (rfcomm_channel_event_pn_t*) event;
1936 
1937     switch (channel->state) {
1938         case RFCOMM_CHANNEL_CLOSED:
1939             switch (event->type){
1940                 case CH_EVT_RCVD_SABM:
1941                     log_info("-> Inform app");
1942                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_SABM);
1943                     channel->state = RFCOMM_CHANNEL_INCOMING_SETUP;
1944                     rfcomm_emit_connection_request(channel);
1945                     break;
1946                 case CH_EVT_RCVD_PN:
1947                     rfcomm_channel_accept_pn(channel, event_pn);
1948                     log_info("-> Inform app");
1949                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_PN);
1950                     channel->state = RFCOMM_CHANNEL_INCOMING_SETUP;
1951                     rfcomm_emit_connection_request(channel);
1952                     break;
1953                 default:
1954                     break;
1955             }
1956             break;
1957 
1958         case RFCOMM_CHANNEL_INCOMING_SETUP:
1959             switch (event->type){
1960                 case CH_EVT_RCVD_SABM:
1961                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_SABM);
1962                     if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_CLIENT_ACCEPTED) {
1963                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_UA);
1964                     }
1965                     break;
1966                 case CH_EVT_RCVD_PN:
1967                     rfcomm_channel_accept_pn(channel, event_pn);
1968                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_PN);
1969                     if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_CLIENT_ACCEPTED) {
1970                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP);
1971                     }
1972                     break;
1973                 case CH_EVT_READY_TO_SEND:
1974                     // if / else if is used to check for state transition after sending
1975                     if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP){
1976                         log_info("Sending UIH Parameter Negotiation Respond for #%u", channel->dlci);
1977                         rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP);
1978                         rfcomm_send_uih_pn_response(multiplexer, channel->dlci, channel->pn_priority, channel->max_frame_size);
1979                     } else if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_UA){
1980                         log_info("Sending UA #%u", channel->dlci);
1981                         rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_UA);
1982                         rfcomm_send_ua(multiplexer, channel->dlci);
1983                     }
1984                     if (rfcomm_channel_ready_for_incoming_dlc_setup(channel)){
1985                         log_info("Incomping setup done, requesting send MSC CMD and send Credits");
1986                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD);
1987                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS);
1988                         channel->state = RFCOMM_CHANNEL_DLC_SETUP;
1989                      }
1990                     break;
1991                 default:
1992                     break;
1993             }
1994             break;
1995 
1996         case RFCOMM_CHANNEL_W4_MULTIPLEXER:
1997             switch (event->type) {
1998                 case CH_EVT_MULTIPLEXER_READY:
1999                     log_info("Muliplexer opened, sending UIH PN next");
2000                     channel->state = RFCOMM_CHANNEL_SEND_UIH_PN;
2001                     break;
2002                 default:
2003                     break;
2004             }
2005             break;
2006 
2007         case RFCOMM_CHANNEL_SEND_UIH_PN:
2008             switch (event->type) {
2009                 case CH_EVT_READY_TO_SEND:
2010                     // update mtu
2011                     channel->max_frame_size = btstack_min(multiplexer->max_frame_size, channel->max_frame_size);
2012                     log_info("Sending UIH Parameter Negotiation Command for #%u (channel 0x%p) mtu %u", channel->dlci, channel, channel->max_frame_size );
2013                     channel->state = RFCOMM_CHANNEL_W4_PN_RSP;
2014                     rfcomm_send_uih_pn_command(multiplexer, channel->dlci, channel->max_frame_size);
2015                     break;
2016                 default:
2017                     break;
2018             }
2019             break;
2020 
2021         case RFCOMM_CHANNEL_W4_PN_RSP:
2022             switch (event->type){
2023                 case CH_EVT_RCVD_PN_RSP:
2024                     // update max frame size
2025                     if (channel->max_frame_size > event_pn->max_frame_size) {
2026                         channel->max_frame_size = event_pn->max_frame_size;
2027                     }
2028                     // new credits
2029                     channel->credits_outgoing = event_pn->credits_outgoing;
2030                     channel->state = RFCOMM_CHANNEL_SEND_SABM_W4_UA;
2031                     break;
2032                 default:
2033                     break;
2034             }
2035             break;
2036 
2037         case RFCOMM_CHANNEL_SEND_SABM_W4_UA:
2038             switch (event->type) {
2039                 case CH_EVT_READY_TO_SEND:
2040                     log_info("Sending SABM #%u", channel->dlci);
2041                     channel->state = RFCOMM_CHANNEL_W4_UA;
2042                     rfcomm_send_sabm(multiplexer, channel->dlci);
2043                     break;
2044                 default:
2045                     break;
2046             }
2047             break;
2048 
2049         case RFCOMM_CHANNEL_W4_UA:
2050             switch (event->type){
2051                 case CH_EVT_RCVD_UA:
2052                     channel->state = RFCOMM_CHANNEL_DLC_SETUP;
2053                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD);
2054                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS);
2055                     break;
2056                 default:
2057                     break;
2058             }
2059             break;
2060 
2061         case RFCOMM_CHANNEL_DLC_SETUP:
2062             switch (event->type){
2063                 case CH_EVT_RCVD_MSC_CMD:
2064                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_CMD);
2065                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP);
2066                     break;
2067                 case CH_EVT_RCVD_MSC_RSP:
2068                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_RSP);
2069                     break;
2070 
2071                 case CH_EVT_READY_TO_SEND:
2072                     if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD){
2073                         log_info("Sending MSC CMD for #%u", channel->dlci);
2074                         rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD);
2075                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SENT_MSC_CMD);
2076                         rfcomm_send_uih_msc_cmd(multiplexer, channel->dlci , 0x8d);  // ea=1,fc=0,rtc=1,rtr=1,ic=0,dv=1
2077                         break;
2078                     }
2079                     if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS){
2080                         log_info("Providing credits for #%u", channel->dlci);
2081                         rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS);
2082                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SENT_CREDITS);
2083 
2084                         if (channel->new_credits_incoming) {
2085                             uint8_t new_credits = channel->new_credits_incoming;
2086                             channel->new_credits_incoming = 0;
2087                             rfcomm_channel_send_credits(channel, new_credits);
2088                         }
2089                         break;
2090 
2091                     }
2092                     break;
2093                 default:
2094                     break;
2095             }
2096             // finally done?
2097             if (rfcomm_channel_ready_for_open(channel)){
2098                 channel->state = RFCOMM_CHANNEL_OPEN;
2099                 rfcomm_channel_opened(channel);
2100             }
2101             break;
2102 
2103         case RFCOMM_CHANNEL_OPEN:
2104             switch (event->type){
2105                 case CH_EVT_RCVD_MSC_CMD:
2106                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP);
2107                     break;
2108                 case CH_EVT_READY_TO_SEND:
2109                     if (channel->new_credits_incoming) {
2110                         uint8_t new_credits = channel->new_credits_incoming;
2111                         channel->new_credits_incoming = 0;
2112                         rfcomm_channel_send_credits(channel, new_credits);
2113                         break;
2114                     }
2115                     break;
2116                 case CH_EVT_RCVD_CREDITS:
2117                     rfcomm_notify_channel_can_send();
2118                     break;
2119                 default:
2120                     break;
2121             }
2122             break;
2123 
2124         case RFCOMM_CHANNEL_SEND_DM:
2125             switch (event->type) {
2126                 case CH_EVT_READY_TO_SEND:
2127                     log_info("Sending DM_PF for #%u", channel->dlci);
2128                     // don't emit channel closed - channel was never open
2129                     channel->state = RFCOMM_CHANNEL_CLOSED;
2130                     rfcomm_send_dm_pf(multiplexer, channel->dlci);
2131                     rfcomm_channel_finalize(channel);
2132                     *out_channel_valid = 0;
2133                     break;
2134                 default:
2135                     break;
2136             }
2137             break;
2138 
2139         case RFCOMM_CHANNEL_SEND_DISC:
2140             switch (event->type) {
2141                 case CH_EVT_READY_TO_SEND:
2142                     channel->state = RFCOMM_CHANNEL_W4_UA_AFTER_DISC;
2143                     rfcomm_send_disc(multiplexer, channel->dlci);
2144                     break;
2145                 default:
2146                     break;
2147             }
2148             break;
2149 
2150         case RFCOMM_CHANNEL_W4_UA_AFTER_DISC:
2151             switch (event->type){
2152                 case CH_EVT_RCVD_UA:
2153                     channel->state = RFCOMM_CHANNEL_CLOSED;
2154                     rfcomm_emit_channel_closed(channel);
2155                     rfcomm_channel_finalize(channel);
2156                     *out_channel_valid = 0;
2157                     break;
2158                 default:
2159                     break;
2160             }
2161             break;
2162 
2163         case RFCOMM_CHANNEL_SEND_UA_AFTER_DISC:
2164             switch (event->type) {
2165                 case CH_EVT_READY_TO_SEND:
2166                     log_info("Sending UA after DISC for #%u", channel->dlci);
2167                     channel->state = RFCOMM_CHANNEL_CLOSED;
2168                     rfcomm_send_ua(multiplexer, channel->dlci);
2169                     rfcomm_channel_finalize(channel);
2170                     *out_channel_valid = 0;
2171                     break;
2172                 default:
2173                     break;
2174             }
2175             break;
2176 
2177         default:
2178             break;
2179     }
2180 }
2181 
2182 // MARK: RFCOMM BTstack API
2183 
2184 void rfcomm_init(void){
2185     rfcomm_client_cid_generator = 0;
2186     rfcomm_multiplexers = NULL;
2187     rfcomm_services     = NULL;
2188     rfcomm_channels     = NULL;
2189     rfcomm_security_level = gap_get_security_level();
2190 }
2191 
2192 void rfcomm_set_required_security_level(gap_security_level_t security_level){
2193     rfcomm_security_level = security_level;
2194 }
2195 
2196 int rfcomm_can_send_packet_now(uint16_t rfcomm_cid){
2197     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2198     if (!channel){
2199         log_error("rfcomm_send cid 0x%02x doesn't exist!", rfcomm_cid);
2200         return 0;
2201     }
2202     return rfcomm_channel_can_send(channel);
2203 }
2204 
2205 void rfcomm_request_can_send_now_event(uint16_t rfcomm_cid){
2206     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2207     if (!channel){
2208         log_error("rfcomm_send cid 0x%02x doesn't exist!", rfcomm_cid);
2209         return;
2210     }
2211     channel->waiting_for_can_send_now = 1;
2212     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2213 }
2214 
2215 static int rfcomm_assert_send_valid(rfcomm_channel_t * channel , uint16_t len){
2216     if (len > channel->max_frame_size){
2217         log_error("rfcomm_send cid 0x%02x, rfcomm data lenght exceeds MTU!", channel->rfcomm_cid);
2218         return RFCOMM_DATA_LEN_EXCEEDS_MTU;
2219     }
2220 
2221 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2222     if (len > rfcomm_max_frame_size_for_l2cap_mtu(sizeof(outgoing_buffer))){
2223         log_error("rfcomm_send cid 0x%02x, length exceeds outgoing rfcomm_out_buffer", channel->rfcomm_cid);
2224         return RFCOMM_DATA_LEN_EXCEEDS_MTU;
2225     }
2226 #endif
2227 
2228     if (!channel->credits_outgoing){
2229         log_info("rfcomm_send cid 0x%02x, no rfcomm outgoing credits!", channel->rfcomm_cid);
2230         return RFCOMM_NO_OUTGOING_CREDITS;
2231     }
2232 
2233     if ((channel->multiplexer->fcon & 1) == 0){
2234         log_info("rfcomm_send cid 0x%02x, aggregate flow off!", channel->rfcomm_cid);
2235         return RFCOMM_AGGREGATE_FLOW_OFF;
2236     }
2237     return 0;
2238 }
2239 
2240 uint16_t rfcomm_get_max_frame_size(uint16_t rfcomm_cid){
2241     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2242     if (!channel){
2243         log_error("rfcomm_get_max_frame_size cid 0x%02x doesn't exist!", rfcomm_cid);
2244         return 0;
2245     }
2246     return channel->max_frame_size;
2247 }
2248 
2249 // pre: rfcomm_can_send_packet_now(rfcomm_cid) == true
2250 int rfcomm_reserve_packet_buffer(void){
2251 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2252     log_error("rfcomm_reserve_packet_buffer should not get called with ERTM");
2253     return 0;
2254 #else
2255     return l2cap_reserve_packet_buffer();
2256 #endif
2257 }
2258 
2259 void rfcomm_release_packet_buffer(void){
2260 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2261     log_error("rfcomm_release_packet_buffer should not get called with ERTM");
2262 #else
2263     l2cap_release_packet_buffer();
2264 #endif
2265 }
2266 
2267 uint8_t * rfcomm_get_outgoing_buffer(void){
2268 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2269     uint8_t * rfcomm_out_buffer = outgoing_buffer;
2270 #else
2271     uint8_t * rfcomm_out_buffer = l2cap_get_outgoing_buffer();
2272 #endif
2273     // address + control + length (16) + no credit field
2274     return &rfcomm_out_buffer[4];
2275 }
2276 
2277 int rfcomm_send_prepared(uint16_t rfcomm_cid, uint16_t len){
2278     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2279     if (!channel){
2280         log_error("rfcomm_send_prepared cid 0x%02x doesn't exist!", rfcomm_cid);
2281         return 0;
2282     }
2283 
2284     int err = rfcomm_assert_send_valid(channel, len);
2285     if (err) return err;
2286 
2287 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2288     if (!l2cap_can_send_packet_now(channel->multiplexer->l2cap_cid)){
2289         log_error("rfcomm_send_prepared: l2cap cannot send now");
2290         return BTSTACK_ACL_BUFFERS_FULL;
2291     }
2292 #else
2293     if (!l2cap_can_send_prepared_packet_now(channel->multiplexer->l2cap_cid)){
2294         log_error("rfcomm_send_prepared: l2cap cannot send now");
2295         return BTSTACK_ACL_BUFFERS_FULL;
2296     }
2297 #endif
2298 
2299     // send might cause l2cap to emit new credits, update counters first
2300     if (len){
2301         channel->credits_outgoing--;
2302     } else {
2303         log_info("sending empty RFCOMM packet for cid %02x", rfcomm_cid);
2304     }
2305 
2306     int result = rfcomm_send_uih_prepared(channel->multiplexer, channel->dlci, len);
2307 
2308     if (result != 0) {
2309         if (len) {
2310             channel->credits_outgoing++;
2311         }
2312         log_error("rfcomm_send_prepared: error %d", result);
2313         return result;
2314     }
2315 
2316     return result;
2317 }
2318 
2319 int rfcomm_send(uint16_t rfcomm_cid, uint8_t *data, uint16_t len){
2320     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2321     if (!channel){
2322         log_error("cid 0x%02x doesn't exist!", rfcomm_cid);
2323         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
2324     }
2325 
2326     int err = rfcomm_assert_send_valid(channel, len);
2327     if (err) return err;
2328     if (!l2cap_can_send_packet_now(channel->multiplexer->l2cap_cid)){
2329         log_error("rfcomm_send_internal: l2cap cannot send now");
2330         return BTSTACK_ACL_BUFFERS_FULL;
2331     }
2332 
2333 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2334 #else
2335     rfcomm_reserve_packet_buffer();
2336 #endif
2337     uint8_t * rfcomm_payload = rfcomm_get_outgoing_buffer();
2338 
2339     (void)memcpy(rfcomm_payload, data, len);
2340     err = rfcomm_send_prepared(rfcomm_cid, len);
2341 
2342 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2343 #else
2344     if (err){
2345         rfcomm_release_packet_buffer();
2346     }
2347 #endif
2348 
2349     return err;
2350 }
2351 
2352 // Sends Local Lnie Status, see LINE_STATUS_..
2353 int rfcomm_send_local_line_status(uint16_t rfcomm_cid, uint8_t line_status){
2354     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2355     if (!channel){
2356         log_error("rfcomm_send_local_line_status cid 0x%02x doesn't exist!", rfcomm_cid);
2357         return 0;
2358     }
2359     return rfcomm_send_uih_rls_cmd(channel->multiplexer, channel->dlci, line_status);
2360 }
2361 
2362 // Sned local modem status. see MODEM_STAUS_..
2363 int rfcomm_send_modem_status(uint16_t rfcomm_cid, uint8_t modem_status){
2364     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2365     if (!channel){
2366         log_error("rfcomm_send_modem_status cid 0x%02x doesn't exist!", rfcomm_cid);
2367         return 0;
2368     }
2369     return rfcomm_send_uih_msc_cmd(channel->multiplexer, channel->dlci, modem_status);
2370 }
2371 
2372 // Configure remote port
2373 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){
2374     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2375     if (!channel){
2376         log_error("rfcomm_send_port_configuration cid 0x%02x doesn't exist!", rfcomm_cid);
2377         return 0;
2378     }
2379     rfcomm_rpn_data_t rpn_data;
2380     rpn_data.baud_rate = baud_rate;
2381     rpn_data.flags = data_bits | (stop_bits << 2) | (parity << 3);
2382     rpn_data.flow_control = flow_control;
2383     rpn_data.xon = 0;
2384     rpn_data.xoff = 0;
2385     rpn_data.parameter_mask_0 = 0x1f;   // all but xon/xoff
2386     rpn_data.parameter_mask_1 = 0x3f;   // all flow control options
2387     return rfcomm_send_uih_rpn_cmd(channel->multiplexer, channel->dlci, &rpn_data);
2388 }
2389 
2390 // Query remote port
2391 int rfcomm_query_port_configuration(uint16_t rfcomm_cid){
2392     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2393     if (!channel){
2394         log_error("rfcomm_query_port_configuration cid 0x%02x doesn't exist!", rfcomm_cid);
2395         return 0;
2396     }
2397     return rfcomm_send_uih_rpn_req(channel->multiplexer, channel->dlci);
2398 }
2399 
2400 
2401 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){
2402     log_info("RFCOMM_CREATE_CHANNEL addr %s channel #%u init credits %u",  bd_addr_to_str(addr), server_channel, initial_credits);
2403 
2404     // create new multiplexer if necessary
2405     uint8_t status = 0;
2406     uint8_t dlci = 0;
2407     int new_multiplexer = 0;
2408     rfcomm_channel_t * channel = NULL;
2409     rfcomm_multiplexer_t * multiplexer = rfcomm_multiplexer_for_addr(addr);
2410     if (!multiplexer) {
2411         multiplexer = rfcomm_multiplexer_create_for_addr(addr);
2412         if (!multiplexer) return BTSTACK_MEMORY_ALLOC_FAILED;
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         if (new_multiplexer) btstack_memory_rfcomm_multiplexer_free(multiplexer);
2424         return RFCOMM_CHANNEL_ALREADY_REGISTERED;
2425     }
2426 
2427     // prepare channel
2428     channel = rfcomm_channel_create(multiplexer, NULL, server_channel);
2429     if (!channel){
2430         if (new_multiplexer) btstack_memory_rfcomm_multiplexer_free(multiplexer);
2431         return BTSTACK_MEMORY_ALLOC_FAILED;
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         (void)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) {
2468             if (new_multiplexer) btstack_memory_rfcomm_multiplexer_free(multiplexer);
2469             btstack_memory_rfcomm_channel_free(channel);
2470             return status;
2471         }
2472         multiplexer->l2cap_cid = l2cap_cid;
2473         return ERROR_CODE_SUCCESS;
2474     }
2475 
2476     channel->state = RFCOMM_CHANNEL_SEND_UIH_PN;
2477 
2478     // start connecting, if multiplexer is already up and running
2479     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
2480     return ERROR_CODE_SUCCESS;
2481 }
2482 
2483 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){
2484     return rfcomm_channel_create_internal(packet_handler, addr, server_channel, 1, initial_credits, out_rfcomm_cid);
2485 }
2486 
2487 uint8_t rfcomm_create_channel(btstack_packet_handler_t packet_handler, bd_addr_t addr, uint8_t server_channel, uint16_t * out_rfcomm_cid){
2488     return rfcomm_channel_create_internal(packet_handler, addr, server_channel, 0, RFCOMM_CREDITS, out_rfcomm_cid);
2489 }
2490 
2491 void rfcomm_disconnect(uint16_t rfcomm_cid){
2492     log_info("RFCOMM_DISCONNECT cid 0x%02x", rfcomm_cid);
2493     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2494     if (!channel) return;
2495 
2496     channel->state = RFCOMM_CHANNEL_SEND_DISC;
2497     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2498 }
2499 
2500 static uint8_t rfcomm_register_service_internal(btstack_packet_handler_t packet_handler,
2501     uint8_t channel, uint16_t max_frame_size, uint8_t incoming_flow_control, uint8_t initial_credits){
2502 
2503     log_info("RFCOMM_REGISTER_SERVICE channel #%u mtu %u flow_control %u credits %u",
2504              channel, max_frame_size, incoming_flow_control, initial_credits);
2505 
2506     // check if already registered
2507     rfcomm_service_t * service = rfcomm_service_for_channel(channel);
2508     if (service){
2509         return RFCOMM_CHANNEL_ALREADY_REGISTERED;
2510     }
2511 
2512     // alloc structure
2513     service = btstack_memory_rfcomm_service_get();
2514     if (!service) {
2515         return BTSTACK_MEMORY_ALLOC_FAILED;
2516     }
2517 
2518     // register with l2cap if not registered before, max MTU
2519     if (btstack_linked_list_empty(&rfcomm_services)){
2520         l2cap_register_service(rfcomm_packet_handler, BLUETOOTH_PROTOCOL_RFCOMM, 0xffff, rfcomm_security_level);
2521     }
2522 
2523     // fill in
2524     service->packet_handler = packet_handler;
2525     service->server_channel = channel;
2526     service->max_frame_size = max_frame_size;
2527     service->incoming_flow_control = incoming_flow_control;
2528     service->incoming_initial_credits = initial_credits;
2529 
2530     // add to services list
2531     btstack_linked_list_add(&rfcomm_services, (btstack_linked_item_t *) service);
2532 
2533     return 0;
2534 }
2535 
2536 uint8_t rfcomm_register_service_with_initial_credits(btstack_packet_handler_t packet_handler,
2537     uint8_t channel, uint16_t max_frame_size, uint8_t initial_credits){
2538 
2539     return rfcomm_register_service_internal(packet_handler, channel, max_frame_size, 1, initial_credits);
2540 }
2541 
2542 uint8_t rfcomm_register_service(btstack_packet_handler_t packet_handler, uint8_t channel,
2543     uint16_t max_frame_size){
2544 
2545     return rfcomm_register_service_internal(packet_handler, channel, max_frame_size, 0,RFCOMM_CREDITS);
2546 }
2547 
2548 void rfcomm_unregister_service(uint8_t service_channel){
2549     log_info("RFCOMM_UNREGISTER_SERVICE #%u", service_channel);
2550     rfcomm_service_t *service = rfcomm_service_for_channel(service_channel);
2551     if (!service) return;
2552     btstack_linked_list_remove(&rfcomm_services, (btstack_linked_item_t *) service);
2553     btstack_memory_rfcomm_service_free(service);
2554 
2555     // unregister if no services active
2556     if (btstack_linked_list_empty(&rfcomm_services)){
2557         // bt_send_cmd(&l2cap_unregister_service, BLUETOOTH_PROTOCOL_RFCOMM);
2558         l2cap_unregister_service(BLUETOOTH_PROTOCOL_RFCOMM);
2559     }
2560 }
2561 
2562 void rfcomm_accept_connection(uint16_t rfcomm_cid){
2563     log_info("RFCOMM_ACCEPT_CONNECTION cid 0x%02x", rfcomm_cid);
2564     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2565     if (!channel) return;
2566     switch (channel->state) {
2567         case RFCOMM_CHANNEL_INCOMING_SETUP:
2568             rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_CLIENT_ACCEPTED);
2569             if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_PN){
2570                 rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP);
2571                 l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2572             }
2573             if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_SABM){
2574                 rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_UA);
2575                 l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2576             }
2577             // at least one of { PN RSP, UA } needs to be sent
2578             // state transistion incoming setup -> dlc setup happens in rfcomm_run after these have been sent
2579             break;
2580         default:
2581             break;
2582     }
2583 
2584 }
2585 
2586 void rfcomm_decline_connection(uint16_t rfcomm_cid){
2587     log_info("RFCOMM_DECLINE_CONNECTION cid 0x%02x", rfcomm_cid);
2588     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2589     if (!channel) return;
2590     switch (channel->state) {
2591         case RFCOMM_CHANNEL_INCOMING_SETUP:
2592             channel->state = RFCOMM_CHANNEL_SEND_DM;
2593             l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2594             break;
2595         default:
2596             break;
2597     }
2598 }
2599 
2600 void rfcomm_grant_credits(uint16_t rfcomm_cid, uint8_t credits){
2601     log_info("RFCOMM_GRANT_CREDITS cid 0x%02x credits %u", rfcomm_cid, credits);
2602     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2603     if (!channel) return;
2604     if (!channel->incoming_flow_control) return;
2605     channel->new_credits_incoming += credits;
2606 
2607     // process
2608     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2609 }
2610 
2611 #ifdef RFCOMM_USE_ERTM
2612 void rfcomm_enable_l2cap_ertm(void request_callback(rfcomm_ertm_request_t * request), void released_callback(uint16_t ertm_id)){
2613     rfcomm_ertm_request_callback  = request_callback;
2614     rfcomm_ertm_released_callback = released_callback;
2615 }
2616 #endif
2617