xref: /btstack/src/classic/rfcomm.c (revision 5576987f3bce50ad7ea167eeb40b7c467df73b54)
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 BLUEKITCHEN
24  * GMBH 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 <inttypes.h>
45 #include <string.h> // memcpy
46 #include <stdint.h>
47 
48 #include "bluetooth_sdp.h"
49 #include "btstack_debug.h"
50 #include "btstack_event.h"
51 #include "btstack_memory.h"
52 #include "btstack_util.h"
53 #include "classic/core.h"
54 #include "classic/rfcomm.h"
55 #include "hci.h"
56 #include "hci_cmd.h"
57 #include "hci_dump.h"
58 #include "l2cap.h"
59 
60 // workaround for missing PRIxPTR on mspgcc (16/20-bit MCU)
61 #ifndef PRIxPTR
62 #if defined(__MSP430X__)  &&  defined(__MSP430X_LARGE__)
63 #define PRIxPTR "lx"
64 #else
65 #define PRIxPTR "x"
66 #endif
67 #endif
68 
69 // ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM requires ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE
70 #ifdef ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM
71 #ifdef ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE
72 #define RFCOMM_USE_OUTGOING_BUFFER
73 #define RFCOMM_USE_ERTM
74 #else
75 #error "ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM requires ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE. "
76 #error "Please disable ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE_FOR_RFCOMM, or, "
77 #error "enable ENABLE_L2CAP_ENHANCED_RETRANSMISSION_MODE"
78 #endif
79 #endif
80 
81 #define RFCOMM_MULIPLEXER_TIMEOUT_MS 60000
82 
83 #define RFCOMM_CREDITS 10
84 
85 // FCS calc
86 #define BT_RFCOMM_CODE_WORD         0xE0 // pol = x8+x2+x1+1
87 #define BT_RFCOMM_CRC_CHECK_LEN     3
88 #define BT_RFCOMM_UIHCRC_CHECK_LEN  2
89 
90 // Control field values      bit no.       1 2 3 4 PF 6 7 8
91 #define BT_RFCOMM_SABM       0x3F       // 1 1 1 1  1 1 0 0
92 #define BT_RFCOMM_UA         0x73       // 1 1 0 0  1 1 1 0
93 #define BT_RFCOMM_DM         0x0F       // 1 1 1 1  0 0 0 0
94 #define BT_RFCOMM_DM_PF      0x1F       // 1 1 1 1  1 0 0 0
95 #define BT_RFCOMM_DISC       0x53       // 1 1 0 0  1 0 1 0
96 #define BT_RFCOMM_UIH        0xEF       // 1 1 1 1  0 1 1 1
97 #define BT_RFCOMM_UIH_PF     0xFF       // 1 1 1 1  0 1 1 1
98 
99 // Multiplexer message types
100 #define BT_RFCOMM_CLD_CMD    0xC3
101 #define BT_RFCOMM_FCON_CMD   0xA3
102 #define BT_RFCOMM_FCON_RSP   0xA1
103 #define BT_RFCOMM_FCOFF_CMD  0x63
104 #define BT_RFCOMM_FCOFF_RSP  0x61
105 #define BT_RFCOMM_MSC_CMD    0xE3
106 #define BT_RFCOMM_MSC_RSP    0xE1
107 #define BT_RFCOMM_NSC_RSP    0x11
108 #define BT_RFCOMM_PN_CMD     0x83
109 #define BT_RFCOMM_PN_RSP     0x81
110 #define BT_RFCOMM_RLS_CMD    0x53
111 #define BT_RFCOMM_RLS_RSP    0x51
112 #define BT_RFCOMM_RPN_CMD    0x93
113 #define BT_RFCOMM_RPN_RSP    0x91
114 #define BT_RFCOMM_TEST_CMD   0x23
115 #define BT_RFCOMM_TEST_RSP   0x21
116 
117 typedef enum {
118     CH_EVT_RCVD_SABM = 1,
119     CH_EVT_RCVD_UA,
120     CH_EVT_RCVD_PN,
121     CH_EVT_RCVD_PN_RSP,
122     CH_EVT_RCVD_DISC,
123     CH_EVT_RCVD_DM,
124     CH_EVT_RCVD_MSC_CMD,
125     CH_EVT_RCVD_MSC_RSP,
126     CH_EVT_RCVD_NSC_RSP,
127     CH_EVT_RCVD_RLS_CMD,
128     CH_EVT_RCVD_RLS_RSP,
129     CH_EVT_RCVD_RPN_CMD,
130     CH_EVT_RCVD_RPN_REQ,
131     CH_EVT_RCVD_RPN_RSP,
132     CH_EVT_RCVD_CREDITS,
133     CH_EVT_MULTIPLEXER_READY,
134     CH_EVT_READY_TO_SEND,
135 } RFCOMM_CHANNEL_EVENT;
136 
137 typedef struct rfcomm_channel_event {
138     RFCOMM_CHANNEL_EVENT type;
139     uint16_t dummy; // force rfcomm_channel_event to be 2-byte aligned -> avoid -Wcast-align warning
140 } rfcomm_channel_event_t;
141 
142 typedef struct rfcomm_channel_event_pn {
143     rfcomm_channel_event_t super;
144     uint16_t max_frame_size;
145     uint8_t  priority;
146     uint8_t  credits_outgoing;
147 } rfcomm_channel_event_pn_t;
148 
149 typedef struct rfcomm_channel_event_rpn {
150     rfcomm_channel_event_t super;
151     rfcomm_rpn_data_t data;
152 } rfcomm_channel_event_rpn_t;
153 
154 typedef struct rfcomm_channel_event_rls {
155     rfcomm_channel_event_t super;
156     uint8_t line_status;
157 } rfcomm_channel_event_rls_t;
158 
159 typedef struct rfcomm_channel_event_msc {
160     rfcomm_channel_event_t super;
161     uint8_t modem_status;
162 } rfcomm_channel_event_msc_t;
163 
164 
165 // global rfcomm data
166 static uint16_t      rfcomm_client_cid_generator;  // used for client channel IDs
167 
168 // linked lists for all
169 static btstack_linked_list_t rfcomm_multiplexers;
170 static btstack_linked_list_t rfcomm_channels;
171 static btstack_linked_list_t rfcomm_services;
172 
173 static gap_security_level_t rfcomm_security_level;
174 
175 #ifdef RFCOMM_USE_ERTM
176 static uint16_t rfcomm_ertm_id;
177 void (*rfcomm_ertm_request_callback)(rfcomm_ertm_request_t * request);
178 void (*rfcomm_ertm_released_callback)(uint16_t ertm_id);
179 #endif
180 
181 #ifdef RFCOMM_USE_OUTGOING_BUFFER
182 static uint8_t outgoing_buffer[1030];
183 #endif
184 
185 static bool rfcomm_channel_can_send(rfcomm_channel_t * channel);
186 static int  rfcomm_channel_ready_for_open(rfcomm_channel_t *channel);
187 static int rfcomm_channel_ready_to_send(rfcomm_channel_t * channel);
188 static void rfcomm_channel_state_machine_with_channel(rfcomm_channel_t *channel, const rfcomm_channel_event_t *event, int * out_channel_valid);
189 static void rfcomm_channel_state_machine_with_dlci(rfcomm_multiplexer_t * multiplexer, uint8_t dlci, const rfcomm_channel_event_t *event);
190 static void rfcomm_emit_can_send_now(rfcomm_channel_t *channel);
191 static int rfcomm_multiplexer_ready_to_send(rfcomm_multiplexer_t * multiplexer);
192 static void rfcomm_multiplexer_state_machine(rfcomm_multiplexer_t * multiplexer, RFCOMM_MULTIPLEXER_EVENT event);
193 
194 // MARK: RFCOMM CLIENT EVENTS
195 
196 static rfcomm_channel_t * rfcomm_channel_for_rfcomm_cid(uint16_t rfcomm_cid){
197     btstack_linked_item_t *it;
198     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
199         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
200         if (channel->rfcomm_cid == rfcomm_cid) {
201             return channel;
202         };
203     }
204     return NULL;
205 }
206 
207 static uint16_t rfcomm_next_client_cid(void){
208     do {
209         if (rfcomm_client_cid_generator == 0xffff) {
210             // don't use 0 as channel id
211             rfcomm_client_cid_generator = 1;
212         } else {
213             rfcomm_client_cid_generator++;
214         }
215     } while (rfcomm_channel_for_rfcomm_cid(rfcomm_client_cid_generator) != NULL);
216     return rfcomm_client_cid_generator;
217 }
218 
219 #ifdef RFCOMM_USE_ERTM
220 static rfcomm_multiplexer_t * rfcomm_multiplexer_for_ertm_id(uint16_t ertm_id) {
221     btstack_linked_item_t *it;
222     for (it = (btstack_linked_item_t *) rfcomm_multiplexers; it ; it = it->next){
223         rfcomm_multiplexer_t * multiplexer = ((rfcomm_multiplexer_t *) it);
224         if (multiplexer->ertm_id == ertm_id) {
225             return multiplexer;
226         };
227     }
228     return NULL;
229 }
230 
231 static uint16_t rfcomm_next_ertm_id(void){
232     do {
233         if (rfcomm_ertm_id == 0xffff) {
234             // don't use 0 as channel id
235             rfcomm_ertm_id = 1;
236         } else {
237             rfcomm_ertm_id++;
238         }
239     } while (rfcomm_multiplexer_for_ertm_id(rfcomm_ertm_id) != NULL);
240     return rfcomm_ertm_id;
241 }
242 
243 #endif
244 
245 // data: event (8), len(8), address(48), channel (8), rfcomm_cid (16)
246 static void rfcomm_emit_connection_request(rfcomm_channel_t *channel) {
247     log_info("RFCOMM_EVENT_INCOMING_CONNECTION addr %s channel #%u cid 0x%02x",
248              bd_addr_to_str(channel->multiplexer->remote_addr), channel->dlci>>1, channel->rfcomm_cid);
249     uint8_t event[13];
250     event[0] = RFCOMM_EVENT_INCOMING_CONNECTION;
251     event[1] = sizeof(event) - 2;
252     reverse_bd_addr(channel->multiplexer->remote_addr, &event[2]);
253     event[8] = channel->dlci >> 1;
254     little_endian_store_16(event, 9, channel->rfcomm_cid);
255     little_endian_store_16(event, 11, channel->multiplexer->con_handle);
256     hci_dump_btstack_event( event, sizeof(event));
257 	(channel->packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
258 }
259 
260 // API Change: BTstack-0.3.50x uses
261 // data: event(8), len(8), status (8), address (48), server channel(8), rfcomm_cid(16), max frame size(16)
262 // next Cydia release will use SVN version of this
263 // data: event(8), len(8), status (8), address (48), handle (16), server channel(8), rfcomm_cid(16), max frame size(16)
264 static void rfcomm_emit_channel_opened(rfcomm_channel_t *channel, uint8_t status) {
265     log_info("RFCOMM_EVENT_CHANNEL_OPENED status 0x%x addr %s handle 0x%x channel #%u cid 0x%02x mtu %u",
266              status, bd_addr_to_str(channel->multiplexer->remote_addr), channel->multiplexer->con_handle,
267              channel->dlci>>1, channel->rfcomm_cid, channel->max_frame_size);
268     uint8_t event[18];
269     uint8_t pos = 0;
270     event[pos++] = RFCOMM_EVENT_CHANNEL_OPENED;  // 0
271     event[pos++] = sizeof(event) - 2;                   // 1
272     event[pos++] = status;                              // 2
273     reverse_bd_addr(channel->multiplexer->remote_addr, &event[pos]); pos += 6; // 3
274     little_endian_store_16(event,  pos, channel->multiplexer->con_handle);   pos += 2; // 9
275 	event[pos++] = channel->dlci >> 1;                                      // 11
276 	little_endian_store_16(event, pos, channel->rfcomm_cid); pos += 2;                 // 12 - channel ID
277 	little_endian_store_16(event, pos, channel->max_frame_size); pos += 2;   // max frame size
278     event[pos++] = channel->service ? 1 : 0;    // linked to service -> incoming
279     hci_dump_btstack_event( event, sizeof(event));
280 	(channel->packet_handler)(HCI_EVENT_PACKET, 0, event, pos);
281 
282     // if channel opened successfully, also send can send now if possible
283     if (status) return;
284     if (rfcomm_channel_can_send(channel)){
285         rfcomm_emit_can_send_now(channel);
286     }
287 }
288 
289 // data: event(8), len(8), rfcomm_cid(16)
290 static void rfcomm_emit_channel_closed(rfcomm_channel_t * channel) {
291     log_info("RFCOMM_EVENT_CHANNEL_CLOSED cid 0x%02x", channel->rfcomm_cid);
292     uint8_t event[4];
293     event[0] = RFCOMM_EVENT_CHANNEL_CLOSED;
294     event[1] = sizeof(event) - 2;
295     little_endian_store_16(event, 2, channel->rfcomm_cid);
296     hci_dump_btstack_event( event, sizeof(event));
297 	(channel->packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
298 }
299 
300 static void rfcomm_emit_remote_line_status(rfcomm_channel_t *channel, uint8_t line_status){
301     log_info("RFCOMM_EVENT_REMOTE_LINE_STATUS cid 0x%02x c, line status 0x%x", channel->rfcomm_cid, line_status);
302     uint8_t event[5];
303     event[0] = RFCOMM_EVENT_REMOTE_LINE_STATUS;
304     event[1] = sizeof(event) - 2;
305     little_endian_store_16(event, 2, channel->rfcomm_cid);
306     event[4] = line_status;
307     hci_dump_btstack_event( event, sizeof(event));
308     (channel->packet_handler)(HCI_EVENT_PACKET, 0, event, sizeof(event));
309 }
310 
311 static void rfcomm_emit_port_configuration(rfcomm_channel_t *channel, bool remote) {
312     // notify client about new settings
313     uint8_t event[2+2+1+sizeof(rfcomm_rpn_data_t)];
314     event[0] = RFCOMM_EVENT_PORT_CONFIGURATION;
315     event[1] = sizeof(event) - 2;
316     little_endian_store_16(event, 2, channel->rfcomm_cid);
317     if (remote){
318         event[4] = 1;
319         (void)memcpy(&event[5], (uint8_t *) &channel->remote_rpn_data, sizeof(rfcomm_rpn_data_t));
320     } else {
321         event[4] = 0;
322         (void)memcpy(&event[5], (uint8_t *) &channel->local_rpn_data, sizeof(rfcomm_rpn_data_t));
323     }
324     hci_dump_btstack_event( event, sizeof(event));
325     (channel->packet_handler)(HCI_EVENT_PACKET, channel->rfcomm_cid, event, sizeof(event));
326 }
327 
328 static void rfcomm_emit_can_send_now(rfcomm_channel_t *channel) {
329     log_debug("RFCOMM_EVENT_CHANNEL_CAN_SEND_NOW local_cid 0x%x", channel->rfcomm_cid);
330     uint8_t event[4];
331     event[0] = RFCOMM_EVENT_CAN_SEND_NOW;
332     event[1] = sizeof(event) - 2;
333     little_endian_store_16(event, 2, channel->rfcomm_cid);
334     hci_dump_btstack_event( event, sizeof(event));
335     (channel->packet_handler)(HCI_EVENT_PACKET, channel->rfcomm_cid, event, sizeof(event));
336 }
337 
338 // MARK RFCOMM RPN DATA HELPER
339 static void rfcomm_rpn_data_set_defaults(rfcomm_rpn_data_t * rpn_data){
340         rpn_data->baud_rate = RPN_BAUD_9600;  /* 9600 bps */
341         rpn_data->flags = 0x03;               /* 8-n-1 */
342         rpn_data->flow_control = 0;           /* no flow control */
343         rpn_data->xon  = 0xd1;                /* XON */
344         rpn_data->xoff = 0xd3;                /* XOFF */
345         rpn_data->parameter_mask_0 = 0x7f;    /* parameter mask, all values set */
346         rpn_data->parameter_mask_1 = 0x3f;    /* parameter mask, all values set */
347 }
348 
349 static void rfcomm_rpn_data_update(rfcomm_rpn_data_t * dest, rfcomm_rpn_data_t * src){
350     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_BAUD){
351         dest->baud_rate = src->baud_rate;
352     }
353     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_DATA_BITS){
354         dest->flags = (dest->flags & 0xfc) | (src->flags & 0x03);
355     }
356     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_STOP_BITS){
357         dest->flags = (dest->flags & 0xfb) | (src->flags & 0x04);
358     }
359     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_PARITY){
360         dest->flags = (dest->flags & 0xf7) | (src->flags & 0x08);
361     }
362     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_PARITY_TYPE){
363         dest->flags = (dest->flags & 0xcf) | (src->flags & 0x30);
364     }
365     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_XON_CHAR){
366         dest->xon = src->xon;
367     }
368     if (src->parameter_mask_0 & RPN_PARAM_MASK_0_XOFF_CHAR){
369         dest->xoff = src->xoff;
370     }
371     uint8_t mask = src->parameter_mask_1 & 0x3f;
372     dest->flow_control = (dest->flow_control & ~mask) | (src->flow_control & mask);
373    // always copy parameter mask, too. informative for client, needed for response
374     dest->parameter_mask_0 = src->parameter_mask_0;
375     dest->parameter_mask_1 = src->parameter_mask_1;
376 }
377 // MARK: RFCOMM MULTIPLEXER HELPER
378 
379 static uint16_t rfcomm_max_frame_size_for_l2cap_mtu(uint16_t l2cap_mtu){
380     // Assume RFCOMM header without credits and 2 byte (14 bit) length field
381     uint16_t max_frame_size = l2cap_mtu - 5;
382     log_info("rfcomm_max_frame_size_for_l2cap_mtu:  %u -> %u", l2cap_mtu, max_frame_size);
383     return max_frame_size;
384 }
385 
386 static void rfcomm_multiplexer_initialize(rfcomm_multiplexer_t *multiplexer){
387     multiplexer->state = RFCOMM_MULTIPLEXER_CLOSED;
388     multiplexer->fcon = 1;
389     multiplexer->send_dm_for_dlci = 0;
390     multiplexer->max_frame_size = rfcomm_max_frame_size_for_l2cap_mtu(l2cap_max_mtu());
391     multiplexer->test_data_len = 0;
392     multiplexer->nsc_command = 0;
393 }
394 
395 static rfcomm_multiplexer_t * rfcomm_multiplexer_create_for_addr(bd_addr_t addr){
396 
397     // alloc structure
398     rfcomm_multiplexer_t * multiplexer = btstack_memory_rfcomm_multiplexer_get();
399     if (!multiplexer) return NULL;
400 
401     // fill in
402     rfcomm_multiplexer_initialize(multiplexer);
403     bd_addr_copy(multiplexer->remote_addr, addr);
404 
405     // add to services list
406     btstack_linked_list_add(&rfcomm_multiplexers, (btstack_linked_item_t *) multiplexer);
407 
408     return multiplexer;
409 }
410 
411 static rfcomm_multiplexer_t * rfcomm_multiplexer_for_addr(bd_addr_t addr){
412     btstack_linked_item_t *it;
413     for (it = (btstack_linked_item_t *) rfcomm_multiplexers; it ; it = it->next){
414         rfcomm_multiplexer_t * multiplexer = ((rfcomm_multiplexer_t *) it);
415         // ignore multiplexer in shutdown
416         if (multiplexer->state == RFCOMM_MULTIPLEXER_SHUTTING_DOWN) continue;
417         if (bd_addr_cmp(addr, multiplexer->remote_addr) == 0) {
418             return multiplexer;
419         };
420     }
421     return NULL;
422 }
423 
424 static rfcomm_multiplexer_t * rfcomm_multiplexer_for_l2cap_cid(uint16_t l2cap_cid) {
425     btstack_linked_item_t *it;
426     for (it = (btstack_linked_item_t *) rfcomm_multiplexers; it ; it = it->next){
427         rfcomm_multiplexer_t * multiplexer = ((rfcomm_multiplexer_t *) it);
428         if (multiplexer->l2cap_cid == l2cap_cid) {
429             return multiplexer;
430         };
431     }
432     return NULL;
433 }
434 
435 static int rfcomm_multiplexer_has_channels(rfcomm_multiplexer_t * multiplexer){
436     btstack_linked_item_t *it;
437     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
438         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
439         if (channel->multiplexer == multiplexer) {
440             return 1;
441         }
442     }
443     return 0;
444 }
445 
446 // MARK: RFCOMM CHANNEL HELPER
447 
448 static void rfcomm_dump_channels(void){
449 #ifdef ENABLE_LOG_INFO
450     btstack_linked_item_t * it;
451     int channels = 0;
452     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
453         rfcomm_channel_t * channel = (rfcomm_channel_t *) it;
454         log_info("Channel #%u: addr %p, state %u", channels, channel, channel->state);
455         channels++;
456     }
457 #endif
458 }
459 
460 static void rfcomm_channel_initialize(rfcomm_channel_t *channel, rfcomm_multiplexer_t *multiplexer,
461                                rfcomm_service_t *service, uint8_t server_channel){
462 
463     // set defaults for port configuration (even for services)
464     rfcomm_rpn_data_set_defaults(&channel->local_rpn_data);
465     rfcomm_rpn_data_set_defaults(&channel->remote_rpn_data);
466 
467     channel->state            = RFCOMM_CHANNEL_CLOSED;
468     channel->state_var        = RFCOMM_CHANNEL_STATE_VAR_NONE;
469 
470     channel->multiplexer      = multiplexer;
471     channel->rfcomm_cid       = rfcomm_next_client_cid();
472     channel->max_frame_size   = multiplexer->max_frame_size;
473 
474     channel->credits_incoming = 0;
475     channel->credits_outgoing = 0;
476 
477     // incoming flow control not active
478     channel->new_credits_incoming  = RFCOMM_CREDITS;
479     channel->incoming_flow_control = 0;
480 
481     // nothing to send
482     channel->local_line_status  = RFCOMM_RLS_STATUS_INVALID;
483     channel->remote_line_status = RFCOMM_RLS_STATUS_INVALID;
484 
485     // modem status - ea=1,fc=0,rtc=1,rtr=1,ic=0,dv=1
486     channel->local_modem_status  = 0x8d;
487     channel->remote_modem_status = 0x8d;
488 
489     channel->service = service;
490 	if (service) {
491 		// incoming connection
492     	channel->dlci = (server_channel << 1) |  multiplexer->outgoing;
493         if (channel->max_frame_size > service->max_frame_size) {
494             channel->max_frame_size = service->max_frame_size;
495         }
496         channel->incoming_flow_control = service->incoming_flow_control;
497         channel->new_credits_incoming  = service->incoming_initial_credits;
498         channel->packet_handler        = service->packet_handler;
499 	} else {
500 		// outgoing connection
501 		channel->dlci = (server_channel << 1) | (multiplexer->outgoing ^ 1);
502 	}
503 }
504 
505 // service == NULL -> outgoing channel
506 static rfcomm_channel_t * rfcomm_channel_create(rfcomm_multiplexer_t * multiplexer,
507                                                 rfcomm_service_t * service, uint8_t server_channel){
508 
509     log_info("rfcomm_channel_create for service %p, channel %u --- list of channels:", service, server_channel);
510     rfcomm_dump_channels();
511 
512     // alloc structure
513     rfcomm_channel_t * channel = btstack_memory_rfcomm_channel_get();
514     if (!channel) return NULL;
515 
516     // fill in
517     rfcomm_channel_initialize(channel, multiplexer, service, server_channel);
518 
519     // add to services list
520     btstack_linked_list_add(&rfcomm_channels, (btstack_linked_item_t *) channel);
521 
522     return channel;
523 }
524 
525 static void rfcomm_notify_channel_can_send(void){
526     btstack_linked_list_iterator_t it;
527     btstack_linked_list_iterator_init(&it, &rfcomm_channels);
528     while (btstack_linked_list_iterator_has_next(&it)){
529         rfcomm_channel_t * channel = (rfcomm_channel_t *) btstack_linked_list_iterator_next(&it);
530         if (!channel->waiting_for_can_send_now) continue; // didn't try to send yet
531         if (!rfcomm_channel_can_send(channel)) continue;  // or cannot yet either
532 
533         channel->waiting_for_can_send_now = 0;
534         rfcomm_emit_can_send_now(channel);
535     }
536 }
537 
538 static rfcomm_channel_t * rfcomm_channel_for_multiplexer_and_dlci(rfcomm_multiplexer_t * multiplexer, uint8_t dlci){
539     btstack_linked_item_t *it;
540     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
541         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
542         if ((channel->dlci == dlci) && (channel->multiplexer == multiplexer)) {
543             return channel;
544         };
545     }
546     return NULL;
547 }
548 
549 static rfcomm_service_t * rfcomm_service_for_channel(uint8_t server_channel){
550     btstack_linked_item_t *it;
551     for (it = (btstack_linked_item_t *) rfcomm_services; it ; it = it->next){
552         rfcomm_service_t * service = ((rfcomm_service_t *) it);
553         if ( service->server_channel == server_channel){
554             return service;
555         };
556     }
557     return NULL;
558 }
559 
560 // MARK: RFCOMM SEND
561 
562 /**
563  * @param credits - only used for RFCOMM flow control in UIH wiht P/F = 1
564  */
565 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){
566 
567     if (!l2cap_can_send_packet_now(multiplexer->l2cap_cid)) return BTSTACK_ACL_BUFFERS_FULL;
568 
569 #ifdef RFCOMM_USE_OUTGOING_BUFFER
570     uint8_t * rfcomm_out_buffer = outgoing_buffer;
571 #else
572     l2cap_reserve_packet_buffer();
573     uint8_t * rfcomm_out_buffer = l2cap_get_outgoing_buffer();
574 #endif
575 
576 	uint16_t pos = 0;
577 	uint8_t crc_fields = 3;
578 
579 	rfcomm_out_buffer[pos++] = address;
580 	rfcomm_out_buffer[pos++] = control;
581 
582 	// length field can be 1 or 2 octets
583 	if (len < 128){
584 		rfcomm_out_buffer[pos++] = (len << 1)| 1;     // bits 0-6
585 	} else {
586 		rfcomm_out_buffer[pos++] = (len & 0x7f) << 1; // bits 0-6
587 		rfcomm_out_buffer[pos++] = len >> 7;          // bits 7-14
588 		crc_fields++;
589 	}
590 
591 	// add credits for UIH frames when PF bit is set
592 	if (control == BT_RFCOMM_UIH_PF){
593 		rfcomm_out_buffer[pos++] = credits;
594 	}
595 
596 	// copy actual data
597 	if (len) {
598 		(void)memcpy(&rfcomm_out_buffer[pos], data, len);
599 		pos += len;
600 	}
601 
602 	// UIH frames only calc FCS over address + control (5.1.1)
603 	if ((control & 0xef) == BT_RFCOMM_UIH){
604 		crc_fields = 2;
605 	}
606 	rfcomm_out_buffer[pos++] =  btstack_crc8_calc(rfcomm_out_buffer, crc_fields); // calc fcs
607 
608 #ifdef RFCOMM_USE_OUTGOING_BUFFER
609     int err = l2cap_send(multiplexer->l2cap_cid, rfcomm_out_buffer, pos);
610 #else
611     int err = l2cap_send_prepared(multiplexer->l2cap_cid, pos);
612 #endif
613 
614     return err;
615 }
616 
617 // simplified version of rfcomm_send_packet_for_multiplexer for prepared rfcomm packet (UIH, 2 byte len, no credits)
618 static uint8_t rfcomm_send_uih_prepared(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint16_t len){
619 
620     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) | (dlci << 2);
621     uint8_t control = BT_RFCOMM_UIH;
622 
623 #ifdef RFCOMM_USE_OUTGOING_BUFFER
624     uint8_t * rfcomm_out_buffer = outgoing_buffer;
625 #else
626     uint8_t * rfcomm_out_buffer = l2cap_get_outgoing_buffer();
627 #endif
628 
629     uint16_t pos = 0;
630     rfcomm_out_buffer[pos++] = address;
631     rfcomm_out_buffer[pos++] = control;
632     rfcomm_out_buffer[pos++] = (len & 0x7f) << 1; // bits 0-6
633     rfcomm_out_buffer[pos++] = len >> 7;          // bits 7-14
634 
635     // actual data is already in place
636     pos += len;
637 
638     // UIH frames only calc FCS over address + control (5.1.1)
639     rfcomm_out_buffer[pos++] =  btstack_crc8_calc(rfcomm_out_buffer, 2); // calc fcs
640 
641 #ifdef RFCOMM_USE_OUTGOING_BUFFER
642     uint8_t status = l2cap_send(multiplexer->l2cap_cid, rfcomm_out_buffer, pos);
643 #else
644     uint8_t status = l2cap_send_prepared(multiplexer->l2cap_cid, pos);
645 #endif
646 
647     return status;
648 }
649 
650 // C/R Flag in Address
651 // - terms: initiator = station that creates multiplexer with SABM
652 // - terms: responder = station that responds to multiplexer setup with UA
653 // "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"
654 //    - command initiator = 1 /response responder = 1
655 //    - command responder = 0 /response initiator = 0
656 // "For UIH frames, the C/R bit is always set according to section 5.4.3.1 in GSM 07.10.
657 //  This applies independently of what is contained wthin the UIH frames, either data or control messages."
658 //    - c/r = 1 for frames by initiating station, 0 = for frames by responding station
659 
660 // C/R Flag in Message
661 // "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."
662 //   - If the C/R bit is set to 1 the message is a command
663 //   - if it is set to 0 the message is a response.
664 
665 // temp/old messge construction
666 
667 // new object oriented version
668 static int rfcomm_send_sabm(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
669 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) | (dlci << 2);   // command
670     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_SABM, 0, NULL, 0);
671 }
672 
673 static int rfcomm_send_disc(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
674 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) | (dlci << 2);  // command
675     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_DISC, 0, NULL, 0);
676 }
677 
678 static int rfcomm_send_ua(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
679 	uint8_t address = (1 << 0) | ((multiplexer->outgoing ^ 1) << 1) | (dlci << 2); // response
680     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UA, 0, NULL, 0);
681 }
682 
683 static int rfcomm_send_dm_pf(rfcomm_multiplexer_t *multiplexer, uint8_t dlci){
684 	uint8_t address = (1 << 0) | ((multiplexer->outgoing ^ 1) << 1) | (dlci << 2); // response
685     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_DM_PF, 0, NULL, 0);
686 }
687 
688 static int rfcomm_send_uih_fc_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t fcon) {
689     uint8_t address = (1 << 0) | (multiplexer->outgoing<< 1);
690     uint8_t payload[2];
691     uint8_t pos = 0;
692     payload[pos++] = fcon ? BT_RFCOMM_FCON_RSP : BT_RFCOMM_FCOFF_RSP;
693     payload[pos++] = (0 << 1) | 1;  // 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_cmd(rfcomm_multiplexer_t *multiplexer, uint8_t * data, uint16_t len) {
698 //     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
699 //     uint8_t payload[2+len];
700 //     uint8_t pos = 0;
701 //     payload[pos++] = BT_RFCOMM_TEST_CMD;
702 //     payload[pos++] = (len + 1) << 1 | 1;  // len
703 //     memcpy(&payload[pos], data, len);
704 //     pos += len;
705 //     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
706 // }
707 
708 static int rfcomm_send_uih_test_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t * data, uint16_t len) {
709     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
710     uint8_t payload[2+RFCOMM_TEST_DATA_MAX_LEN];
711     uint8_t pos = 0;
712     payload[pos++] = BT_RFCOMM_TEST_RSP;
713     if (len > RFCOMM_TEST_DATA_MAX_LEN) {
714         len = RFCOMM_TEST_DATA_MAX_LEN;
715     }
716     payload[pos++] = (len << 1) | 1;  // len
717     (void)memcpy(&payload[pos], data, len);
718     pos += len;
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_cmd(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_CMD;
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_msc_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t signals) {
734 	uint8_t address = (1 << 0) | (multiplexer->outgoing<< 1);
735 	uint8_t payload[4];
736 	uint8_t pos = 0;
737 	payload[pos++] = BT_RFCOMM_MSC_RSP;
738 	payload[pos++] = (2 << 1) | 1;  // len
739 	payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
740 	payload[pos++] = signals;
741 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
742 }
743 
744 static int rfcomm_send_uih_nsc_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t command) {
745     uint8_t address = (1 << 0) | (multiplexer->outgoing<< 1);
746     uint8_t payload[3];
747     uint8_t pos = 0;
748     payload[pos++] = BT_RFCOMM_NSC_RSP;
749     payload[pos++] = (1 << 1) | 1;  // len
750     payload[pos++] = command;
751     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
752 }
753 
754 static int rfcomm_send_uih_pn_command(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint16_t max_frame_size){
755 	uint8_t payload[10];
756 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
757 	uint8_t pos = 0;
758 	payload[pos++] = BT_RFCOMM_PN_CMD;
759 	payload[pos++] = (8 << 1) | 1;  // len
760 	payload[pos++] = dlci;
761 	payload[pos++] = 0xf0; // pre-defined for Bluetooth, see 5.5.3 of TS 07.10 Adaption for RFCOMM
762 	payload[pos++] = 0; // priority
763 	payload[pos++] = 0; // max 60 seconds ack
764 	payload[pos++] = max_frame_size & 0xff; // max framesize low
765 	payload[pos++] = max_frame_size >> 8;   // max framesize high
766 	payload[pos++] = 0x00; // number of retransmissions
767 	payload[pos++] = 0x00; // (unused error recovery window) initial number of credits
768 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
769 }
770 
771 // "The response may not change the DLCI, the priority, the convergence layer, or the timer value." rfcomm_tutorial.pdf
772 static int rfcomm_send_uih_pn_response(rfcomm_multiplexer_t *multiplexer, uint8_t dlci,
773                                        uint8_t priority, uint16_t max_frame_size){
774 	uint8_t payload[10];
775 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
776 	uint8_t pos = 0;
777 	payload[pos++] = BT_RFCOMM_PN_RSP;
778 	payload[pos++] = (8 << 1) | 1;  // len
779 	payload[pos++] = dlci;
780 	payload[pos++] = 0xe0; // pre defined for Bluetooth, see 5.5.3 of TS 07.10 Adaption for RFCOMM
781 	payload[pos++] = priority; // priority
782 	payload[pos++] = 0; // max 60 seconds ack
783 	payload[pos++] = max_frame_size & 0xff; // max framesize low
784 	payload[pos++] = max_frame_size >> 8;   // max framesize high
785 	payload[pos++] = 0x00; // number of retransmissions
786 	payload[pos++] = 0x00; // (unused error recovery window) initial number of credits
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_cmd(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_CMD;
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_rls_rsp(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, uint8_t line_status) {
802     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
803     uint8_t payload[4];
804     uint8_t pos = 0;
805     payload[pos++] = BT_RFCOMM_RLS_RSP;
806     payload[pos++] = (2 << 1) | 1;  // len
807     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
808     payload[pos++] = line_status;
809     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
810 }
811 
812 static int rfcomm_send_uih_rpn_config(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, rfcomm_rpn_data_t *rpn_data) {
813     uint8_t payload[10];
814     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
815     uint8_t pos = 0;
816     payload[pos++] = BT_RFCOMM_RPN_CMD;
817     payload[pos++] = (8 << 1) | 1;  // len
818     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
819     payload[pos++] = rpn_data->baud_rate;
820     payload[pos++] = rpn_data->flags;
821     payload[pos++] = rpn_data->flow_control;
822     payload[pos++] = rpn_data->xon;
823     payload[pos++] = rpn_data->xoff;
824     payload[pos++] = rpn_data->parameter_mask_0;
825     payload[pos++] = rpn_data->parameter_mask_1;
826     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
827 }
828 
829 static int rfcomm_send_uih_rpn_query(rfcomm_multiplexer_t *multiplexer, uint8_t dlci) {
830     uint8_t payload[3];
831     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
832     uint8_t pos = 0;
833     payload[pos++] = BT_RFCOMM_RPN_CMD;
834     payload[pos++] = (1 << 1) | 1;  // len
835     payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
836     return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
837 }
838 
839 static int rfcomm_send_uih_rpn_response(rfcomm_multiplexer_t *multiplexer, uint8_t dlci, rfcomm_rpn_data_t *rpn_data) {
840 	uint8_t payload[10];
841 	uint8_t address = (1 << 0) | (multiplexer->outgoing << 1);
842 	uint8_t pos = 0;
843 	payload[pos++] = BT_RFCOMM_RPN_RSP;
844 	payload[pos++] = (8 << 1) | 1;  // len
845 	payload[pos++] = (1 << 0) | (1 << 1) | (dlci << 2); // CMD => C/R = 1
846 	payload[pos++] = rpn_data->baud_rate;
847 	payload[pos++] = rpn_data->flags;
848 	payload[pos++] = rpn_data->flow_control;
849 	payload[pos++] = rpn_data->xon;
850 	payload[pos++] = rpn_data->xoff;
851 	payload[pos++] = rpn_data->parameter_mask_0;
852 	payload[pos++] = rpn_data->parameter_mask_1;
853 	return rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH, 0, (uint8_t *) payload, pos);
854 }
855 
856 static void rfcomm_send_uih_credits(rfcomm_multiplexer_t *multiplexer, uint8_t dlci,  uint8_t credits){
857     uint8_t address = (1 << 0) | (multiplexer->outgoing << 1) |  (dlci << 2);
858     rfcomm_send_packet_for_multiplexer(multiplexer, address, BT_RFCOMM_UIH_PF, credits, NULL, 0);
859 }
860 
861 // depending on channel state emit channel opened with status or channel closed
862 static void rfcomm_channel_emit_final_event(rfcomm_channel_t * channel, uint8_t status){
863     // emit appropriate events
864     switch(channel->state){
865         case RFCOMM_CHANNEL_OPEN:
866         case RFCOMM_CHANNEL_W4_UA_AFTER_DISC:
867             rfcomm_emit_channel_closed(channel);
868             break;
869         case RFCOMM_CHANNEL_SEND_UA_AFTER_DISC:
870             // remote didn't wait until we send the UA disc
871             // close event already emitted
872             break;
873         default:
874             rfcomm_emit_channel_opened(channel, status);
875             break;
876     }
877 }
878 
879 // MARK: RFCOMM MULTIPLEXER
880 static void rfcomm_multiplexer_free(rfcomm_multiplexer_t * multiplexer){
881     btstack_linked_list_remove( &rfcomm_multiplexers, (btstack_linked_item_t *) multiplexer);
882     btstack_memory_rfcomm_multiplexer_free(multiplexer);
883 }
884 
885 static void rfcomm_multiplexer_finalize(rfcomm_multiplexer_t * multiplexer){
886     // close and remove all channels
887     btstack_linked_item_t *it = (btstack_linked_item_t *) &rfcomm_channels;
888     while (it->next){
889         rfcomm_channel_t * channel = (rfcomm_channel_t *) it->next;
890         if (channel->multiplexer == multiplexer) {
891             // emit open with status or closed
892             rfcomm_channel_emit_final_event(channel, RFCOMM_MULTIPLEXER_STOPPED);
893             // remove from list
894             it->next = it->next->next;
895             // free channel struct
896             btstack_memory_rfcomm_channel_free(channel);
897         } else {
898             it = it->next;
899         }
900     }
901 
902     // remove mutliplexer
903     rfcomm_multiplexer_free(multiplexer);
904 }
905 
906 static void rfcomm_multiplexer_opened(rfcomm_multiplexer_t *multiplexer){
907     log_info("Multiplexer up and running");
908     multiplexer->state = RFCOMM_MULTIPLEXER_OPEN;
909 
910     const rfcomm_channel_event_t event = { CH_EVT_MULTIPLEXER_READY, 0};
911 
912     // transition of channels that wait for multiplexer
913     btstack_linked_item_t *it;
914     for (it = (btstack_linked_item_t *) rfcomm_channels; it ; it = it->next){
915         rfcomm_channel_t * channel = ((rfcomm_channel_t *) it);
916         if (channel->multiplexer != multiplexer) continue;
917         int rfcomm_channel_valid = 1;
918         rfcomm_channel_state_machine_with_channel(channel, &event, &rfcomm_channel_valid);
919         if (rfcomm_channel_valid && rfcomm_channel_ready_to_send(channel)){
920             l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
921         }
922     }
923 
924     // request can send now for multiplexer if ready
925     if (rfcomm_multiplexer_ready_to_send(multiplexer)){
926         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
927     }
928 }
929 
930 static void rfcomm_handle_can_send_now(uint16_t l2cap_cid){
931 
932     log_debug("can_send_now enter: %u", l2cap_cid);
933 
934     btstack_linked_list_iterator_t it;
935     int token_consumed = 0;
936 
937     // forward token to multiplexer
938     btstack_linked_list_iterator_init(&it, &rfcomm_multiplexers);
939     while (!token_consumed && btstack_linked_list_iterator_has_next(&it)){
940         rfcomm_multiplexer_t * multiplexer = (rfcomm_multiplexer_t *) btstack_linked_list_iterator_next(&it);
941         if (multiplexer->l2cap_cid != l2cap_cid) continue;
942         if (rfcomm_multiplexer_ready_to_send(multiplexer)){
943             log_debug("can_send_now enter: multiplexer token");
944             token_consumed = 1;
945             rfcomm_multiplexer_state_machine(multiplexer, MULT_EV_READY_TO_SEND);
946         }
947     }
948 
949     // forward token to channel state machine
950     btstack_linked_list_iterator_init(&it, &rfcomm_channels);
951     while (!token_consumed && btstack_linked_list_iterator_has_next(&it)){
952         rfcomm_channel_t * channel = (rfcomm_channel_t *) btstack_linked_list_iterator_next(&it);
953         if (channel->multiplexer->l2cap_cid != l2cap_cid) continue;
954         // channel state machine
955         if (rfcomm_channel_ready_to_send(channel)){
956             log_debug("can_send_now enter: channel token");
957             token_consumed = 1;
958             const rfcomm_channel_event_t event = { CH_EVT_READY_TO_SEND, 0 };
959             int rfcomm_channel_valid = 1;
960             rfcomm_channel_state_machine_with_channel(channel, &event, &rfcomm_channel_valid);
961         }
962     }
963 
964     // forward token to client
965     btstack_linked_list_iterator_init(&it, &rfcomm_channels);
966     while (!token_consumed && btstack_linked_list_iterator_has_next(&it)){
967         rfcomm_channel_t * channel = (rfcomm_channel_t *) btstack_linked_list_iterator_next(&it);
968         if (channel->multiplexer->l2cap_cid != l2cap_cid) continue;
969         // client waiting for can send now
970         if (!channel->waiting_for_can_send_now)    continue;
971         if ((channel->multiplexer->fcon & 1) == 0) continue;
972         if (!channel->credits_outgoing){
973             log_debug("can_send_now waiting to send but no credits (ignore)");
974             continue;
975         }
976 
977         log_debug("can_send_now enter: client token");
978         token_consumed = 1;
979         channel->waiting_for_can_send_now = 0;
980         rfcomm_emit_can_send_now(channel);
981     }
982 
983     // if token was consumed, request another one
984     if (token_consumed) {
985         l2cap_request_can_send_now_event(l2cap_cid);
986     }
987 
988     log_debug("can_send_now exit");
989 }
990 
991 static void rfcomm_multiplexer_set_state_and_request_can_send_now_event(rfcomm_multiplexer_t * multiplexer, RFCOMM_MULTIPLEXER_STATE state){
992     multiplexer->state = state;
993     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
994 }
995 
996 /**
997  * @return handled packet
998  */
999 static int rfcomm_hci_event_handler(uint8_t *packet, uint16_t size){
1000 
1001     UNUSED(size);   // ok: handling own l2cap events
1002 
1003     bd_addr_t event_addr;
1004     uint16_t l2cap_cid;
1005     hci_con_handle_t con_handle;
1006     rfcomm_multiplexer_t *multiplexer = NULL;
1007     uint8_t status;
1008 
1009     switch (hci_event_packet_get_type(packet)) {
1010 
1011         // accept incoming rfcomm connection if no multiplexer exists yet
1012         case L2CAP_EVENT_INCOMING_CONNECTION:
1013             l2cap_event_incoming_connection_get_address(packet, event_addr);
1014             con_handle = l2cap_event_incoming_connection_get_handle(packet);
1015             l2cap_cid  = l2cap_event_incoming_connection_get_local_cid(packet);
1016 
1017             btstack_assert(l2cap_event_incoming_connection_get_psm(packet) == BLUETOOTH_PROTOCOL_RFCOMM);
1018 
1019             multiplexer = rfcomm_multiplexer_for_addr(event_addr);
1020 
1021             if (multiplexer) {
1022                 log_info("RFCOMM incoming (l2cap_cid 0x%02x) => decline - multiplexer already exists", l2cap_cid);
1023                 l2cap_decline_connection(l2cap_cid);
1024                 return 1;
1025             }
1026 
1027             // create and inititialize new multiplexer instance (incoming)
1028             multiplexer = rfcomm_multiplexer_create_for_addr(event_addr);
1029             if (!multiplexer){
1030                 log_info("RFCOMM incoming (l2cap_cid 0x%02x) => decline - no memory left", l2cap_cid);
1031                 l2cap_decline_connection(l2cap_cid);
1032                 return 1;
1033             }
1034 
1035             multiplexer->con_handle = con_handle;
1036             multiplexer->l2cap_cid = l2cap_cid;
1037             //
1038             multiplexer->state = RFCOMM_MULTIPLEXER_W4_SABM_0;
1039             log_info("RFCOMM incoming (l2cap_cid 0x%02x) => accept", l2cap_cid);
1040 
1041 #ifdef RFCOMM_USE_ERTM
1042             // request
1043             rfcomm_ertm_request_t request;
1044             memset(&request, 0, sizeof(rfcomm_ertm_request_t));
1045             (void)memcpy(request.addr, event_addr, 6);
1046             request.ertm_id = rfcomm_next_ertm_id();
1047             if (rfcomm_ertm_request_callback){
1048                 (*rfcomm_ertm_request_callback)(&request);
1049             }
1050             if (request.ertm_config && request.ertm_buffer && request.ertm_buffer_size){
1051                 multiplexer->ertm_id = request.ertm_id;
1052                 l2cap_ertm_accept_connection(l2cap_cid, request.ertm_config, request.ertm_buffer, request.ertm_buffer_size);
1053                 return 1;
1054             }
1055 #endif
1056 
1057             l2cap_accept_connection(l2cap_cid);
1058             return 1;
1059 
1060         // l2cap connection opened -> store l2cap_cid, remote_addr
1061         case L2CAP_EVENT_CHANNEL_OPENED:
1062 
1063             btstack_assert(l2cap_event_channel_opened_get_psm(packet) == BLUETOOTH_PROTOCOL_RFCOMM);
1064 
1065             status = l2cap_event_channel_opened_get_status(packet);
1066             log_info("channel opened, status %u", status);
1067 
1068             // get multiplexer for remote addr
1069             con_handle = l2cap_event_channel_opened_get_handle(packet);
1070             l2cap_cid = l2cap_event_channel_opened_get_local_cid(packet);
1071             l2cap_event_channel_opened_get_address(packet, event_addr);
1072             multiplexer = rfcomm_multiplexer_for_addr(event_addr);
1073             if (!multiplexer) {
1074                 log_error("channel opened but no multiplexer prepared");
1075                 return 1;
1076             }
1077 
1078             // set con handle for outgoing (already set for incoming)
1079             multiplexer->con_handle = con_handle;
1080 
1081             // on l2cap open error discard everything
1082             if (status){
1083 
1084                 // mark multiplexer as shutting down
1085                 multiplexer->state = RFCOMM_MULTIPLEXER_SHUTTING_DOWN;
1086 
1087                 // emit rfcomm_channel_opened with status and free channel
1088                 // note: repeatedly go over list until full iteration causes no further change
1089                 int done;
1090                 do {
1091                     done = 1;
1092                     btstack_linked_item_t * it = (btstack_linked_item_t *) &rfcomm_channels;
1093                     while (it->next) {
1094                         rfcomm_channel_t * channel = (rfcomm_channel_t *) it->next;
1095                         if (channel->multiplexer == multiplexer){
1096                             done = 0;
1097                             rfcomm_emit_channel_opened(channel, status);
1098                             btstack_linked_list_remove(&rfcomm_channels, (btstack_linked_item_t *) channel);
1099                             btstack_memory_rfcomm_channel_free(channel);
1100                             break;
1101                         } else {
1102                             it = it->next;
1103                         }
1104                     }
1105                 } while (!done);
1106 
1107                 // free multiplexer
1108                 rfcomm_multiplexer_free(multiplexer);
1109                 return 1;
1110             }
1111 
1112             // following could be: rfcomm_multiplexer_state_machine(..., EVENT_L2CAP_OPENED)
1113 
1114             // set max frame size based on l2cap MTU
1115             multiplexer->max_frame_size = rfcomm_max_frame_size_for_l2cap_mtu(little_endian_read_16(packet, 17));
1116 
1117             if (multiplexer->state == RFCOMM_MULTIPLEXER_W4_CONNECT) {
1118                 log_info("channel opened: outgoing connection");
1119                 multiplexer->l2cap_cid = l2cap_cid;
1120                 // send SABM #0
1121                 rfcomm_multiplexer_set_state_and_request_can_send_now_event(multiplexer, RFCOMM_MULTIPLEXER_SEND_SABM_0);
1122             }
1123             return 1;
1124 
1125             // l2cap disconnect -> state = RFCOMM_MULTIPLEXER_CLOSED;
1126 
1127         // Notify channel packet handler if they can send now
1128         case L2CAP_EVENT_CAN_SEND_NOW:
1129             l2cap_cid = l2cap_event_can_send_now_get_local_cid(packet);
1130             rfcomm_handle_can_send_now(l2cap_cid);
1131             return 1;
1132 
1133         case L2CAP_EVENT_CHANNEL_CLOSED:
1134             l2cap_cid = l2cap_event_channel_closed_get_local_cid(packet);
1135             multiplexer = rfcomm_multiplexer_for_l2cap_cid(l2cap_cid);
1136             log_info("channel closed cid 0x%0x, mult %p", l2cap_cid, multiplexer);
1137             if (!multiplexer) break;
1138             log_info("channel closed state %u", multiplexer->state);
1139             // no need to call l2cap_disconnect here, as it's already closed
1140             rfcomm_multiplexer_finalize(multiplexer);
1141             return 1;
1142 
1143 #ifdef RFCOMM_USE_ERTM
1144         case L2CAP_EVENT_ERTM_BUFFER_RELEASED:
1145             l2cap_cid = l2cap_event_ertm_buffer_released_get_local_cid(packet);
1146             multiplexer = rfcomm_multiplexer_for_l2cap_cid(l2cap_cid);
1147             if (multiplexer) {
1148                 log_info("buffer for ertm id %u released", multiplexer->ertm_id);
1149                 if (rfcomm_ertm_released_callback){
1150                     (*rfcomm_ertm_released_callback)(multiplexer->ertm_id);
1151                 }
1152             }
1153             break;
1154 #endif
1155 
1156         default:
1157             break;
1158     }
1159     return 0;
1160 }
1161 
1162 static int rfcomm_multiplexer_l2cap_packet_handler(uint16_t channel, uint8_t *packet, uint16_t size){
1163     // get or create a multiplexer for a certain device
1164     rfcomm_multiplexer_t *multiplexer = rfcomm_multiplexer_for_l2cap_cid(channel);
1165     if (!multiplexer) return 0;
1166 
1167     uint16_t l2cap_cid = multiplexer->l2cap_cid;
1168 
1169     if (size < 3) return 0;
1170 
1171 	// but only care for multiplexer control channel
1172     uint8_t frame_dlci = packet[0] >> 2;
1173     if (frame_dlci) return 0;
1174     const uint8_t length_offset = (packet[2] & 1) ^ 1;  // to be used for pos >= 3
1175     const uint8_t credit_offset = ((packet[1] & BT_RFCOMM_UIH_PF) == BT_RFCOMM_UIH_PF) ? 1 : 0;   // credits for uih_pf frames
1176     const uint8_t payload_offset = 3 + length_offset + credit_offset;
1177     switch (packet[1]){
1178 
1179         case BT_RFCOMM_SABM:
1180             if (multiplexer->state == RFCOMM_MULTIPLEXER_W4_SABM_0){
1181                 log_info("Received SABM #0");
1182                 multiplexer->outgoing = 0;
1183                 rfcomm_multiplexer_set_state_and_request_can_send_now_event(multiplexer, RFCOMM_MULTIPLEXER_SEND_UA_0);
1184                 return 1;
1185             }
1186             break;
1187 
1188         case BT_RFCOMM_UA:
1189             if (multiplexer->state == RFCOMM_MULTIPLEXER_W4_UA_0) {
1190                 // UA #0 -> send UA #0, state = RFCOMM_MULTIPLEXER_OPEN
1191                 log_info("Received UA #0 ");
1192                 rfcomm_multiplexer_opened(multiplexer);
1193                 return 1;
1194             }
1195             break;
1196 
1197         case BT_RFCOMM_DISC:
1198             // DISC #0 -> send UA #0, close multiplexer
1199             log_info("Received DISC #0, (ougoing = %u)", multiplexer->outgoing);
1200             rfcomm_multiplexer_set_state_and_request_can_send_now_event(multiplexer, RFCOMM_MULTIPLEXER_SEND_UA_0_AND_DISC);
1201             return 1;
1202 
1203         case BT_RFCOMM_DM:
1204             // DM #0 - we shouldn't get this, just give up
1205             log_info("Received DM #0");
1206             log_info("-> Closing down multiplexer");
1207             rfcomm_multiplexer_finalize(multiplexer);
1208             l2cap_disconnect(l2cap_cid);
1209             return 1;
1210 
1211         case BT_RFCOMM_UIH:
1212             if (payload_offset >= size) return 0;
1213 
1214             if (packet[payload_offset] == BT_RFCOMM_CLD_CMD){
1215                 // Multiplexer close down (CLD) -> close mutliplexer
1216                 log_info("Received Multiplexer close down command");
1217                 log_info("-> Closing down multiplexer");
1218                 rfcomm_multiplexer_finalize(multiplexer);
1219                 l2cap_disconnect(l2cap_cid);
1220                 return 1;
1221             }
1222             switch (packet[payload_offset]){
1223                 case BT_RFCOMM_CLD_CMD:
1224                      // Multiplexer close down (CLD) -> close mutliplexer
1225                     log_info("Received Multiplexer close down command");
1226                     log_info("-> Closing down multiplexer");
1227                     rfcomm_multiplexer_finalize(multiplexer);
1228                     l2cap_disconnect(l2cap_cid);
1229                     return 1;
1230 
1231                 case BT_RFCOMM_FCON_CMD:
1232                     multiplexer->fcon = 0x81;
1233                     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1234                     return 1;
1235 
1236                 case BT_RFCOMM_FCOFF_CMD:
1237                     multiplexer->fcon = 0x80;
1238                     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1239                     return 1;
1240 
1241                 case BT_RFCOMM_TEST_CMD: {
1242                     if ((payload_offset + 1) >= size) return 0; // (1)
1243                     log_info("Received test command");
1244                     int len = packet[payload_offset+1] >> 1; // length < 125
1245                     if (len > RFCOMM_TEST_DATA_MAX_LEN){
1246                         len = RFCOMM_TEST_DATA_MAX_LEN;
1247                     }
1248                     // from (1) => (size - 1 - payload_offset) > 0
1249                     len = btstack_min(len, size - 1 - payload_offset);  // avoid information leak
1250                     multiplexer->test_data_len = len;
1251                     (void)memcpy(multiplexer->test_data,
1252                                  &packet[payload_offset + 2], len);
1253                     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1254                     return 1;
1255                 }
1256                 default:
1257                     break;
1258             }
1259             break;
1260 
1261         default:
1262             break;
1263 
1264     }
1265     return 0;
1266 }
1267 
1268 static int rfcomm_multiplexer_ready_to_send(rfcomm_multiplexer_t * multiplexer){
1269     if (multiplexer->send_dm_for_dlci) return 1;
1270     if (multiplexer->nsc_command) return 1;
1271     if (multiplexer->fcon & 0x80) return 1;
1272     switch (multiplexer->state){
1273         case RFCOMM_MULTIPLEXER_SEND_SABM_0:
1274         case RFCOMM_MULTIPLEXER_SEND_UA_0:
1275         case RFCOMM_MULTIPLEXER_SEND_UA_0_AND_DISC:
1276             return 1;
1277         case RFCOMM_MULTIPLEXER_OPEN:
1278             if (multiplexer->test_data_len) {
1279                 return 1;
1280             }
1281             break;
1282         default:
1283             break;
1284     }
1285     return 0;
1286 }
1287 
1288 static void rfcomm_multiplexer_state_machine(rfcomm_multiplexer_t * multiplexer, RFCOMM_MULTIPLEXER_EVENT event){
1289 
1290     if (event != MULT_EV_READY_TO_SEND) return;
1291 
1292     uint16_t l2cap_cid = multiplexer->l2cap_cid;
1293 
1294     // process stored DM responses
1295     if (multiplexer->send_dm_for_dlci){
1296         uint8_t dlci = multiplexer->send_dm_for_dlci;
1297         multiplexer->send_dm_for_dlci = 0;
1298         rfcomm_send_dm_pf(multiplexer, dlci);
1299         return;
1300     }
1301 
1302     if (multiplexer->nsc_command){
1303         uint8_t command = multiplexer->nsc_command;
1304         multiplexer->nsc_command = 0;
1305         rfcomm_send_uih_nsc_rsp(multiplexer, command);
1306         return;
1307     }
1308 
1309     if (multiplexer->fcon & 0x80){
1310         multiplexer->fcon &= 0x01;
1311         rfcomm_send_uih_fc_rsp(multiplexer, multiplexer->fcon);
1312 
1313         if (multiplexer->fcon == 0) return;
1314         // trigger client to send again after sending FCon Response
1315         rfcomm_notify_channel_can_send();
1316         return;
1317     }
1318 
1319     switch (multiplexer->state) {
1320         case RFCOMM_MULTIPLEXER_SEND_SABM_0:
1321             log_info("Sending SABM #0 - (multi 0x%p)", multiplexer);
1322             multiplexer->state = RFCOMM_MULTIPLEXER_W4_UA_0;
1323             rfcomm_send_sabm(multiplexer, 0);
1324             break;
1325         case RFCOMM_MULTIPLEXER_SEND_UA_0:
1326             log_info("Sending UA #0");
1327             multiplexer->state = RFCOMM_MULTIPLEXER_OPEN;
1328             rfcomm_send_ua(multiplexer, 0);
1329 
1330             rfcomm_multiplexer_opened(multiplexer);
1331             break;
1332         case RFCOMM_MULTIPLEXER_SEND_UA_0_AND_DISC:
1333             log_info("Sending UA #0");
1334             log_info("Closing down multiplexer");
1335             multiplexer->state = RFCOMM_MULTIPLEXER_CLOSED;
1336             rfcomm_send_ua(multiplexer, 0);
1337 
1338             rfcomm_multiplexer_finalize(multiplexer);
1339             l2cap_disconnect(l2cap_cid);
1340             break;
1341         case RFCOMM_MULTIPLEXER_OPEN:
1342             // respond to test command
1343             if (multiplexer->test_data_len){
1344                 int len = multiplexer->test_data_len;
1345                 log_info("Sending TEST Response with %u bytes", len);
1346                 multiplexer->test_data_len = 0;
1347                 rfcomm_send_uih_test_rsp(multiplexer, multiplexer->test_data, len);
1348                 return;
1349             }
1350             break;
1351         default:
1352             break;
1353     }
1354 }
1355 
1356 // MARK: RFCOMM CHANNEL
1357 
1358 static void rfcomm_channel_send_credits(rfcomm_channel_t *channel, uint8_t credits){
1359     channel->credits_incoming += credits;
1360     rfcomm_send_uih_credits(channel->multiplexer, channel->dlci, credits);
1361 }
1362 
1363 static bool rfcomm_channel_can_send(rfcomm_channel_t * channel){
1364     log_debug("cid 0x%04x, outgoing credits %u", channel->rfcomm_cid, channel->credits_outgoing);
1365     if (!channel->credits_outgoing) return false;
1366     if ((channel->multiplexer->fcon & 1) == 0) return false;
1367     return l2cap_can_send_packet_now(channel->multiplexer->l2cap_cid) != 0;
1368 }
1369 
1370 static void rfcomm_channel_opened(rfcomm_channel_t *rfChannel){
1371 
1372     log_info("opened");
1373 
1374     rfChannel->state = RFCOMM_CHANNEL_OPEN;
1375     rfcomm_emit_channel_opened(rfChannel, 0);
1376     rfcomm_emit_port_configuration(rfChannel, false);
1377 
1378     // hack for problem detecting authentication failure
1379     rfcomm_multiplexer_t *multiplexer = rfChannel->multiplexer;
1380     multiplexer->at_least_one_connection = 1;
1381 
1382     // request can send now if channel ready
1383     if (rfcomm_channel_ready_to_send(rfChannel)){
1384         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1385     }
1386 }
1387 
1388 static void rfcomm_channel_packet_handler_uih(rfcomm_multiplexer_t *multiplexer, uint8_t * packet, uint16_t size){
1389     const uint8_t frame_dlci = packet[0] >> 2;
1390     const uint8_t length_offset = (packet[2] & 1) ^ 1;  // to be used for pos >= 3
1391     const uint8_t credit_offset = ((packet[1] & BT_RFCOMM_UIH_PF) == BT_RFCOMM_UIH_PF) ? 1 : 0;   // credits for uih_pf frames
1392     const uint8_t payload_offset = 3 + length_offset + credit_offset;
1393     int request_can_send_now = 0;
1394 
1395     rfcomm_channel_t * channel = rfcomm_channel_for_multiplexer_and_dlci(multiplexer, frame_dlci);
1396     if (!channel) return;
1397 
1398     // handle new outgoing credits
1399     if (packet[1] == BT_RFCOMM_UIH_PF) {
1400 
1401         // add them
1402         uint16_t new_credits = packet[3+length_offset];
1403         channel->credits_outgoing += new_credits;
1404         log_info( "RFCOMM data UIH_PF, new credits channel 0x%02x: %u, now %u", channel->rfcomm_cid, new_credits, channel->credits_outgoing);
1405 
1406         // notify channel statemachine
1407         rfcomm_channel_event_t channel_event = { CH_EVT_RCVD_CREDITS, 0 };
1408         log_debug("state machine, waiting_for_can_send_now %u", channel->waiting_for_can_send_now);
1409         int rfcomm_channel_valid = 1;
1410         rfcomm_channel_state_machine_with_channel(channel, &channel_event, &rfcomm_channel_valid);
1411         if (rfcomm_channel_valid){
1412             if (rfcomm_channel_ready_to_send(channel) || channel->waiting_for_can_send_now){
1413                 request_can_send_now = 1;
1414             }
1415         }
1416     }
1417 
1418     // contains payload?
1419     if ((size - 1) > payload_offset){
1420 
1421         // log_info( "RFCOMM data UIH_PF, size %u, channel %p", size-payload_offset-1, rfChannel->connection);
1422 
1423         // decrease incoming credit counter
1424         if (channel->credits_incoming > 0){
1425             channel->credits_incoming--;
1426         }
1427 
1428         // deliver payload
1429         (channel->packet_handler)(RFCOMM_DATA_PACKET, channel->rfcomm_cid,
1430                               &packet[payload_offset], size-payload_offset-1);
1431     }
1432 
1433     // automatically provide new credits to remote device, if no incoming flow control
1434     if (!channel->incoming_flow_control && (channel->credits_incoming < 5)){
1435         channel->new_credits_incoming = RFCOMM_CREDITS;
1436         request_can_send_now = 1;
1437     }
1438 
1439     if (request_can_send_now){
1440         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1441     }
1442 }
1443 
1444 static void rfcomm_channel_accept_pn(rfcomm_channel_t *channel, rfcomm_channel_event_pn_t *event){
1445     // priority of client request
1446     channel->pn_priority = event->priority;
1447 
1448     // new credits
1449     channel->credits_outgoing = event->credits_outgoing;
1450 
1451     // negotiate max frame size
1452     if (channel->max_frame_size > channel->multiplexer->max_frame_size) {
1453         channel->max_frame_size = channel->multiplexer->max_frame_size;
1454     }
1455     if (channel->max_frame_size > event->max_frame_size) {
1456         channel->max_frame_size = event->max_frame_size;
1457     }
1458 
1459 }
1460 
1461 static void rfcomm_channel_finalize(rfcomm_channel_t *channel){
1462     // remove from list
1463     btstack_linked_list_remove( &rfcomm_channels, (btstack_linked_item_t *) channel);
1464 
1465     // free channel
1466     btstack_memory_rfcomm_channel_free(channel);
1467 }
1468 
1469 static void rfcomm_channel_state_machine_with_dlci(rfcomm_multiplexer_t * multiplexer, uint8_t dlci, const rfcomm_channel_event_t *event){
1470 
1471     // TODO: if client max frame size is smaller than RFCOMM_DEFAULT_SIZE, send PN
1472 
1473 
1474     // lookup existing channel
1475     rfcomm_channel_t * channel = rfcomm_channel_for_multiplexer_and_dlci(multiplexer, dlci);
1476 
1477     // log_info("rfcomm_channel_state_machine_with_dlci lookup dlci #%u = 0x%08x - event %u", dlci, (int) channel, event->type);
1478 
1479     if (channel) {
1480         int rfcomm_channel_valid = 1;
1481         rfcomm_channel_state_machine_with_channel(channel, event, &rfcomm_channel_valid);
1482         if (rfcomm_channel_valid && rfcomm_channel_ready_to_send(channel)){
1483             l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1484         }
1485         return;
1486     }
1487 
1488     // service registered?
1489     rfcomm_service_t * service = rfcomm_service_for_channel(dlci >> 1);
1490     // log_info("rfcomm_channel_state_machine_with_dlci service dlci #%u = 0x%08x", dlci, (int) service);
1491     if (!service) {
1492         // discard request by sending disconnected mode
1493         multiplexer->send_dm_for_dlci = dlci;
1494         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1495         return;
1496     }
1497 
1498     // create channel for some events
1499     switch (event->type) {
1500         case CH_EVT_RCVD_SABM:
1501         case CH_EVT_RCVD_PN:
1502         case CH_EVT_RCVD_RPN_REQ:
1503         case CH_EVT_RCVD_RPN_CMD:
1504             // setup incoming channel
1505             channel = rfcomm_channel_create(multiplexer, service, dlci >> 1);
1506             if (!channel){
1507                 // discard request by sending disconnected mode
1508                 multiplexer->send_dm_for_dlci = dlci;
1509                 l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1510             }
1511             break;
1512         default:
1513             break;
1514     }
1515 
1516     if (!channel) {
1517         // discard request by sending disconnected mode
1518         multiplexer->send_dm_for_dlci = dlci;
1519         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1520         return;
1521     }
1522 
1523     int rfcomm_channel_valid = 1;
1524     rfcomm_channel_state_machine_with_channel(channel, event, &rfcomm_channel_valid);
1525     if (rfcomm_channel_valid && rfcomm_channel_ready_to_send(channel)){
1526         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1527     }
1528 }
1529 
1530 static void rfcomm_channel_packet_handler(rfcomm_multiplexer_t * multiplexer,  uint8_t *packet, uint16_t size){
1531 
1532     UNUSED(size);   // ok: fixed format messages
1533 
1534     // rfcomm: (0) addr [76543 server channel] [2 direction: initiator uses 1] [1 C/R: CMD by initiator = 1] [0 EA=1]
1535     const uint8_t frame_dlci = packet[0] >> 2;
1536     uint8_t message_dlci; // used by commands in UIH(_PF) packets
1537 	uint8_t message_len;  //   "
1538 
1539     // rfcomm: (1) command/control
1540     // -- credits_offset = 1 if command == BT_RFCOMM_UIH_PF
1541     const uint8_t credit_offset = ((packet[1] & BT_RFCOMM_UIH_PF) == BT_RFCOMM_UIH_PF) ? 1 : 0;   // credits for uih_pf frames
1542     // rfcomm: (2) length. if bit 0 is cleared, 2 byte length is used. (little endian)
1543     const uint8_t length_offset = (packet[2] & 1) ^ 1;  // to be used for pos >= 3
1544     // rfcomm: (3+length_offset) credits if credits_offset == 1
1545     // rfcomm: (3+length_offest+credits_offset)
1546     const uint8_t payload_offset = 3 + length_offset + credit_offset;
1547 
1548     rfcomm_channel_event_t event;
1549     rfcomm_channel_event_pn_t event_pn;
1550     rfcomm_channel_event_rpn_t event_rpn;
1551     rfcomm_channel_event_msc_t event_msc;
1552 
1553     // switch by rfcomm message type
1554     switch(packet[1]) {
1555 
1556         case BT_RFCOMM_SABM:
1557             event.type = CH_EVT_RCVD_SABM;
1558             log_info("Received SABM #%u", frame_dlci);
1559             rfcomm_channel_state_machine_with_dlci(multiplexer, frame_dlci, &event);
1560             break;
1561 
1562         case BT_RFCOMM_UA:
1563             event.type = CH_EVT_RCVD_UA;
1564             log_info("Received UA #%u",frame_dlci);
1565             rfcomm_channel_state_machine_with_dlci(multiplexer, frame_dlci, &event);
1566             break;
1567 
1568         case BT_RFCOMM_DISC:
1569             event.type = CH_EVT_RCVD_DISC;
1570             rfcomm_channel_state_machine_with_dlci(multiplexer, frame_dlci, &event);
1571             break;
1572 
1573         case BT_RFCOMM_DM:
1574         case BT_RFCOMM_DM_PF:
1575             event.type = CH_EVT_RCVD_DM;
1576             rfcomm_channel_state_machine_with_dlci(multiplexer, frame_dlci, &event);
1577             break;
1578 
1579         case BT_RFCOMM_UIH_PF:
1580         case BT_RFCOMM_UIH:
1581 
1582             message_len  = packet[payload_offset+1] >> 1;
1583 
1584             switch (packet[payload_offset]) {
1585                 case BT_RFCOMM_PN_CMD:
1586                     message_dlci = packet[payload_offset+2];
1587                     event_pn.super.type = CH_EVT_RCVD_PN;
1588                     event_pn.priority = packet[payload_offset+4];
1589                     event_pn.max_frame_size = little_endian_read_16(packet, payload_offset+6);
1590                     event_pn.credits_outgoing = packet[payload_offset+9];
1591                     log_info("Received UIH Parameter Negotiation Command for #%u, credits %u",
1592                         message_dlci, event_pn.credits_outgoing);
1593                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_pn);
1594                     break;
1595 
1596                 case BT_RFCOMM_PN_RSP:
1597                     message_dlci = packet[payload_offset+2];
1598                     event_pn.super.type = CH_EVT_RCVD_PN_RSP;
1599                     event_pn.priority = packet[payload_offset+4];
1600                     event_pn.max_frame_size = little_endian_read_16(packet, payload_offset+6);
1601                     event_pn.credits_outgoing = packet[payload_offset+9];
1602                     log_info("Received UIH Parameter Negotiation Response max frame %u, credits %u",
1603                             event_pn.max_frame_size, event_pn.credits_outgoing);
1604                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_pn);
1605                     break;
1606 
1607                 case BT_RFCOMM_MSC_CMD:
1608                     message_dlci = packet[payload_offset+2] >> 2;
1609                     event_msc.super.type = CH_EVT_RCVD_MSC_CMD;
1610                     event_msc.modem_status = packet[payload_offset+3];
1611                     log_info("Received MSC CMD for #%u, ", message_dlci);
1612                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_msc);
1613                     break;
1614 
1615                 case BT_RFCOMM_MSC_RSP:
1616                     message_dlci = packet[payload_offset+2] >> 2;
1617                     event.type = CH_EVT_RCVD_MSC_RSP;
1618                     log_info("Received MSC RSP for #%u", message_dlci);
1619                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, &event);
1620                     break;
1621 
1622                 case BT_RFCOMM_RPN_CMD:
1623                     message_dlci = packet[payload_offset+2] >> 2;
1624                     switch (message_len){
1625                         case 1:
1626                             log_info("Received Remote Port Negotiation Request for #%u", message_dlci);
1627                             event.type = CH_EVT_RCVD_RPN_REQ;
1628                             rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, &event);
1629                             break;
1630                         case 8:
1631                             log_info("Received Remote Port Negotiation Update for #%u", message_dlci);
1632                             event_rpn.super.type = CH_EVT_RCVD_RPN_CMD;
1633                             event_rpn.data = *(rfcomm_rpn_data_t*) &packet[payload_offset+3];
1634                             rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_rpn);
1635                             break;
1636                         default:
1637                             break;
1638                     }
1639                     break;
1640 
1641                 case BT_RFCOMM_RPN_RSP:
1642                     message_dlci = packet[payload_offset+2] >> 2;
1643                     if (message_len != 8) break;
1644                     event_rpn.super.type = CH_EVT_RCVD_RPN_RSP;
1645                     event_rpn.data = *(rfcomm_rpn_data_t*) &packet[payload_offset+3];
1646                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_rpn);
1647                     break;
1648 
1649                 case BT_RFCOMM_RLS_CMD: {
1650                     log_info("Received RLS command");
1651                     message_dlci = packet[payload_offset+2] >> 2;
1652                     rfcomm_channel_event_rls_t event_rls;
1653                     event_rls.super.type = CH_EVT_RCVD_RLS_CMD;
1654                     event_rls.line_status = packet[payload_offset+3];
1655                     rfcomm_channel_state_machine_with_dlci(multiplexer, message_dlci, (rfcomm_channel_event_t*) &event_rls);
1656                     break;
1657                 }
1658 
1659                 case BT_RFCOMM_RLS_RSP:
1660                     log_info("Received RLS response");
1661                     break;
1662 
1663                 // Following commands are handled by rfcomm_multiplexer_l2cap_packet_handler
1664                 // case BT_RFCOMM_TEST_CMD:
1665                 // case BT_RFCOMM_FCOFF_CMD:
1666                 // case BT_RFCOMM_FCON_CMD:
1667                 // everything else is an not supported command
1668                 default: {
1669                     log_error("Received unknown UIH command packet - 0x%02x", packet[payload_offset]);
1670                     multiplexer->nsc_command = packet[payload_offset];
1671                     break;
1672                 }
1673             }
1674             break;
1675 
1676         default:
1677             log_error("Received unknown RFCOMM message type %x", packet[1]);
1678             break;
1679     }
1680 
1681     // trigger next action - example W4_PN_RSP: transition to SEND_SABM which only depends on "can send"
1682     if (rfcomm_multiplexer_ready_to_send(multiplexer)){
1683         l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
1684     }
1685 }
1686 
1687 static void rfcomm_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
1688 
1689     if (packet_type == HCI_EVENT_PACKET){
1690         rfcomm_hci_event_handler(packet, size);
1691         return;
1692     }
1693 
1694     // we only handle l2cap packets for:
1695     if (packet_type != L2CAP_DATA_PACKET) return;
1696 
1697     //  - multiplexer itself
1698     int handled = rfcomm_multiplexer_l2cap_packet_handler(channel, packet, size);
1699 
1700     if (handled) return;
1701 
1702     // - channel over open multiplexer
1703     rfcomm_multiplexer_t * multiplexer = rfcomm_multiplexer_for_l2cap_cid(channel);
1704     if ( (multiplexer == NULL) || (multiplexer->state != RFCOMM_MULTIPLEXER_OPEN)) return;
1705 
1706     // channel data ?
1707     // rfcomm: (0) addr [76543 server channel] [2 direction: initiator uses 1] [1 C/R: CMD by initiator = 1] [0 EA=1]
1708     const uint8_t frame_dlci = packet[0] >> 2;
1709 
1710     if (frame_dlci && ((packet[1] == BT_RFCOMM_UIH) || (packet[1] == BT_RFCOMM_UIH_PF))) {
1711         rfcomm_channel_packet_handler_uih(multiplexer, packet, size);
1712         return;
1713     }
1714 
1715     rfcomm_channel_packet_handler(multiplexer, packet, size);
1716 }
1717 
1718 static int rfcomm_channel_ready_for_open(rfcomm_channel_t *channel){
1719     // note: exchanging MSC isn't neccessary to consider channel open
1720     // note: having outgoing credits is also not necessary to consider channel open
1721     // 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);
1722     // if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SENT_MSC_RSP) == 0) return 0;
1723     // if (channel->credits_outgoing == 0) return 0;
1724     log_info("rfcomm_channel_ready_for_open state %u, flags needed %04x, current %08" PRIx32 ", rf credits %u",
1725          channel->state, RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_RSP, channel->state_var, channel->credits_outgoing);
1726     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_RSP) == 0) return 0;
1727     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SENT_CREDITS) == 0) return 0;
1728 
1729     return 1;
1730 }
1731 
1732 static int rfcomm_channel_ready_for_incoming_dlc_setup(rfcomm_channel_t * channel){
1733     log_info("rfcomm_channel_ready_for_incoming_dlc_setup state var %08" PRIx32, channel->state_var);
1734     // Client accept and SABM/UA is required, PN RSP is needed if PN was received
1735     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_CLIENT_ACCEPTED) == 0) return 0;
1736     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_SABM      ) == 0) return 0;
1737     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_UA        ) != 0) return 0;
1738     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP    ) != 0) return 0;
1739     return 1;
1740 }
1741 
1742 inline static void rfcomm_channel_state_add(rfcomm_channel_t *channel, uint32_t flag){
1743     channel->state_var |= flag;
1744 }
1745 inline static void rfcomm_channel_state_remove(rfcomm_channel_t *channel, uint32_t flag){
1746     channel->state_var &= ~flag;
1747 }
1748 
1749 static int rfcomm_channel_ready_to_send(rfcomm_channel_t * channel){
1750     switch (channel->state){
1751         case RFCOMM_CHANNEL_SEND_UIH_PN:
1752             log_debug("ch-ready: state %u", channel->state);
1753             return 1;
1754         case RFCOMM_CHANNEL_SEND_SABM_W4_UA:
1755             log_debug("ch-ready: state %u", channel->state);
1756             return 1;
1757         case RFCOMM_CHANNEL_SEND_UA_AFTER_DISC:
1758             log_debug("ch-ready: state %u", channel->state);
1759             return 1;
1760         case RFCOMM_CHANNEL_SEND_DISC:
1761             log_debug("ch-ready: state %u", channel->state);
1762             return 1;
1763         case RFCOMM_CHANNEL_SEND_DM:
1764             log_debug("ch-ready: state %u", channel->state);
1765             return 1;
1766         case RFCOMM_CHANNEL_OPEN:
1767             if (channel->new_credits_incoming) {
1768                 log_debug("ch-ready: channel open & new_credits_incoming") ;
1769                 return 1;
1770             }
1771             break;
1772         case RFCOMM_CHANNEL_DLC_SETUP:
1773             if (channel->state_var & (
1774                 RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD  |
1775                 RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS
1776              )) {
1777                 log_debug("ch-ready: channel dlc setup & send msc cmd or send credits") ;
1778                 return 1;
1779             }
1780             break;
1781 
1782         default:
1783             break;
1784     }
1785 
1786     if (channel->state_var & (
1787         RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP       |
1788         RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_QUERY    |
1789         RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_CONFIG   |
1790         RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RESPONSE |
1791         RFCOMM_CHANNEL_STATE_VAR_SEND_UA           |
1792         RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD      |
1793         RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP
1794                              )){
1795         log_debug("ch-ready: state %x, state var %x", channel->state, channel->state_var);
1796         return 1;
1797     }
1798 
1799     if (channel->local_line_status != RFCOMM_RLS_STATUS_INVALID) {
1800         log_debug("ch-ready: rls_line_status");
1801         return 1;
1802     }
1803 
1804     if (channel->remote_line_status != RFCOMM_RLS_STATUS_INVALID) {
1805         log_debug("ch-ready: rls_line_status");
1806         return 1;
1807     }
1808 
1809     return 0;
1810 }
1811 
1812 
1813 static void rfcomm_channel_state_machine_with_channel(rfcomm_channel_t *channel, const rfcomm_channel_event_t *event, int * out_channel_valid){
1814 
1815     // channel != NULL -> channel valid
1816     *out_channel_valid = 1;
1817 
1818     rfcomm_multiplexer_t *multiplexer = channel->multiplexer;
1819 
1820     // TODO: integrate in common switch
1821     if (event->type == CH_EVT_RCVD_DISC){
1822         rfcomm_emit_channel_closed(channel);
1823         channel->state = RFCOMM_CHANNEL_SEND_UA_AFTER_DISC;
1824         return;
1825     }
1826 
1827     // TODO: integrate in common switch
1828     if (event->type == CH_EVT_RCVD_DM){
1829         log_info("Received DM message for #%u", channel->dlci);
1830         log_info("-> Closing channel locally for #%u", channel->dlci);
1831         rfcomm_channel_emit_final_event(channel, ERROR_CODE_CONNECTION_REJECTED_DUE_TO_LIMITED_RESOURCES);
1832         rfcomm_channel_finalize(channel);
1833         *out_channel_valid = 0;
1834         return;
1835     }
1836 
1837     // remote port negotiation command - just accept everything for now
1838     //
1839     // "The RPN command can be used before a new DLC is opened and should be used whenever the port settings change."
1840     // "The RPN command is specified as optional in TS 07.10, but it is mandatory to recognize and respond to it in RFCOMM.
1841     //   (Although the handling of individual settings are implementation-dependent.)"
1842     //
1843 
1844     // TODO: integrate in common switch
1845     if (event->type == CH_EVT_RCVD_RPN_CMD){
1846         // control port parameters
1847         rfcomm_channel_event_rpn_t *event_rpn = (rfcomm_channel_event_rpn_t*) event;
1848         rfcomm_rpn_data_update(&channel->local_rpn_data, &event_rpn->data);
1849         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RESPONSE);
1850         // notify client about new settings
1851         rfcomm_emit_port_configuration(channel, false);
1852         return;
1853     }
1854 
1855     // TODO: integrate in common switch
1856     if (event->type == CH_EVT_RCVD_RPN_REQ){
1857         // no values got accepted (no values have beens sent)
1858         channel->local_rpn_data.parameter_mask_0 = 0x00;
1859         channel->local_rpn_data.parameter_mask_1 = 0x00;
1860         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RESPONSE);
1861         return;
1862     }
1863 
1864     if (event->type == CH_EVT_RCVD_RLS_CMD){
1865         rfcomm_channel_event_rls_t * event_rls = (rfcomm_channel_event_rls_t*) event;
1866         channel->remote_line_status = event_rls->line_status & 0x0f;
1867         log_info("CH_EVT_RCVD_RLS_CMD remote line status 0x%0x", channel->remote_line_status);
1868         rfcomm_emit_remote_line_status(channel, channel->remote_line_status);
1869         return;
1870     }
1871 
1872     // TODO: integrate in common switch
1873     if (event->type == CH_EVT_READY_TO_SEND){
1874         if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_QUERY){
1875             log_info("Sending Remote Port Configuration Query for #%u", channel->dlci);
1876             rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_QUERY);
1877             rfcomm_send_uih_rpn_query(channel->multiplexer, channel->dlci);
1878             return;
1879         }
1880         if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_CONFIG){
1881             log_info("Sending Remote Port Configuration for #%u", channel->dlci);
1882             rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_CONFIG);
1883             rfcomm_send_uih_rpn_config(channel->multiplexer, channel->dlci, &channel->remote_rpn_data);
1884             return;
1885         }
1886         if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RESPONSE){
1887             log_info("Sending Remote Port Negotiation RSP for #%u", channel->dlci);
1888             rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_RESPONSE);
1889             rfcomm_send_uih_rpn_response(multiplexer, channel->dlci, &channel->local_rpn_data);
1890             return;
1891         }
1892         if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD){
1893             log_info("Sending MSC CMD for #%u", channel->dlci);
1894             rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD);
1895             rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SENT_MSC_CMD);
1896             rfcomm_send_uih_msc_cmd(multiplexer, channel->dlci , channel->local_modem_status);
1897             return;
1898         }
1899         if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP){
1900             log_info("Sending MSC RSP for #%u", channel->dlci);
1901             rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP);
1902             rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SENT_MSC_RSP);
1903             rfcomm_send_uih_msc_rsp(multiplexer, channel->dlci, channel->remote_modem_status);
1904             return;
1905         }
1906         if (channel->local_line_status != RFCOMM_RLS_STATUS_INVALID){
1907             log_info("Sending RLS CMD 0x%0x", channel->local_line_status);
1908             uint8_t line_status = channel->local_line_status;
1909             channel->local_line_status = RFCOMM_RLS_STATUS_INVALID;
1910             rfcomm_send_uih_rls_cmd(multiplexer, channel->dlci, line_status);
1911             return;
1912         }
1913         if (channel->remote_line_status != RFCOMM_RLS_STATUS_INVALID){
1914             log_info("Sending RLS RSP 0x%0x", channel->remote_line_status);
1915             uint8_t line_status = channel->remote_line_status;
1916             channel->remote_line_status = RFCOMM_RLS_STATUS_INVALID;
1917             rfcomm_send_uih_rls_rsp(multiplexer, channel->dlci, line_status);
1918             return;
1919         }
1920     }
1921 
1922     // emit MSC status to app
1923     if (event->type == CH_EVT_RCVD_MSC_CMD){
1924         // notify client about new settings
1925         rfcomm_channel_event_msc_t *event_msc = (rfcomm_channel_event_msc_t*) event;
1926         uint8_t modem_status_event[5];
1927         modem_status_event[0] = RFCOMM_EVENT_REMOTE_MODEM_STATUS;
1928         modem_status_event[1] = sizeof(event) - 2;
1929         little_endian_store_16(modem_status_event, 2, channel->rfcomm_cid);
1930         modem_status_event[4] = 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                     channel->remote_modem_status = ((rfcomm_channel_event_msc_t*) event)->modem_status;
2065                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_CMD);
2066                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP);
2067                     break;
2068                 case CH_EVT_RCVD_MSC_RSP:
2069                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_RCVD_MSC_RSP);
2070                     break;
2071 
2072                 case CH_EVT_READY_TO_SEND:
2073                     if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS){
2074                         log_info("Providing credits for #%u", channel->dlci);
2075                         rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_CREDITS);
2076                         rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SENT_CREDITS);
2077                         if (channel->new_credits_incoming) {
2078                             uint8_t new_credits = channel->new_credits_incoming;
2079                             channel->new_credits_incoming = 0;
2080                             rfcomm_channel_send_credits(channel, new_credits);
2081                         }
2082                         break;
2083                     }
2084                     break;
2085                 default:
2086                     break;
2087             }
2088             // finally done?
2089             if (rfcomm_channel_ready_for_open(channel)){
2090                 channel->state = RFCOMM_CHANNEL_OPEN;
2091                 rfcomm_channel_opened(channel);
2092             }
2093             break;
2094 
2095         case RFCOMM_CHANNEL_OPEN:
2096             switch (event->type){
2097                 case CH_EVT_RCVD_MSC_CMD:
2098                     channel->remote_modem_status = ((rfcomm_channel_event_msc_t*) event)->modem_status;
2099                     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_RSP);
2100                     break;
2101                 case CH_EVT_RCVD_RPN_RSP:
2102                     if ((channel->state_var & RFCOMM_CHANNEL_STATE_VAR_EMIT_RPN_RESPONSE) == 0) break;
2103                     rfcomm_channel_state_remove(channel, RFCOMM_CHANNEL_STATE_VAR_EMIT_RPN_RESPONSE);
2104                     memcpy(&channel->remote_rpn_data, &((rfcomm_channel_event_rpn_t*) event)->data, sizeof(rfcomm_rpn_data_t));
2105                     rfcomm_emit_port_configuration(channel, true);
2106                     break;
2107                 case CH_EVT_READY_TO_SEND:
2108                     if (channel->new_credits_incoming) {
2109                         uint8_t new_credits = channel->new_credits_incoming;
2110                         channel->new_credits_incoming = 0;
2111                         rfcomm_channel_send_credits(channel, new_credits);
2112                         break;
2113                     }
2114                     break;
2115                 case CH_EVT_RCVD_CREDITS:
2116                     rfcomm_notify_channel_can_send();
2117                     break;
2118                 default:
2119                     break;
2120             }
2121             break;
2122 
2123         case RFCOMM_CHANNEL_SEND_DM:
2124             switch (event->type) {
2125                 case CH_EVT_READY_TO_SEND:
2126                     log_info("Sending DM_PF for #%u", channel->dlci);
2127                     // don't emit channel closed - channel was never open
2128                     channel->state = RFCOMM_CHANNEL_CLOSED;
2129                     rfcomm_send_dm_pf(multiplexer, channel->dlci);
2130                     rfcomm_channel_finalize(channel);
2131                     *out_channel_valid = 0;
2132                     break;
2133                 default:
2134                     break;
2135             }
2136             break;
2137 
2138         case RFCOMM_CHANNEL_SEND_DISC:
2139             switch (event->type) {
2140                 case CH_EVT_READY_TO_SEND:
2141                     channel->state = RFCOMM_CHANNEL_W4_UA_AFTER_DISC;
2142                     rfcomm_send_disc(multiplexer, channel->dlci);
2143                     break;
2144                 default:
2145                     break;
2146             }
2147             break;
2148 
2149         case RFCOMM_CHANNEL_W4_UA_AFTER_DISC:
2150             switch (event->type){
2151                 case CH_EVT_RCVD_UA:
2152                     channel->state = RFCOMM_CHANNEL_CLOSED;
2153                     rfcomm_emit_channel_closed(channel);
2154                     rfcomm_channel_finalize(channel);
2155                     // RFCOMM v1.2, 5.2.2. Close-Down Procedure
2156                     // The device closing the last connection (DLC) on a particular session shall close the
2157                     // multiplexer by closing the corresponding L2CAP channel.
2158                     if (rfcomm_multiplexer_has_channels(multiplexer) == false){
2159                         log_info("Closed last DLC, shut-down multiplexer");
2160                         uint16_t l2cap_cid = multiplexer->l2cap_cid;
2161                         rfcomm_multiplexer_finalize(multiplexer);
2162                         l2cap_disconnect(l2cap_cid);
2163                     }
2164                     *out_channel_valid = 0;
2165                     break;
2166                 default:
2167                     break;
2168             }
2169             break;
2170 
2171         case RFCOMM_CHANNEL_SEND_UA_AFTER_DISC:
2172             switch (event->type) {
2173                 case CH_EVT_READY_TO_SEND:
2174                     log_info("Sending UA after DISC for #%u", channel->dlci);
2175                     channel->state = RFCOMM_CHANNEL_CLOSED;
2176                     rfcomm_send_ua(multiplexer, channel->dlci);
2177                     rfcomm_channel_finalize(channel);
2178                     *out_channel_valid = 0;
2179                     break;
2180                 default:
2181                     break;
2182             }
2183             break;
2184 
2185         default:
2186             break;
2187     }
2188 }
2189 
2190 // MARK: RFCOMM BTstack API
2191 
2192 void rfcomm_init(void){
2193     rfcomm_security_level = gap_get_security_level();
2194 #ifdef RFCOMM_USE_ERTM
2195     rfcomm_ertm_id = 0;
2196 #endif
2197 }
2198 
2199 void rfcomm_deinit(void){
2200     rfcomm_client_cid_generator = 0;
2201     rfcomm_multiplexers = NULL;
2202     rfcomm_services     = NULL;
2203     rfcomm_channels     = NULL;
2204 #ifdef RFCOMM_USE_ERTM
2205     rfcomm_ertm_request_callback  = NULL;
2206     rfcomm_ertm_released_callback = NULL;
2207 #endif
2208 }
2209 
2210 void rfcomm_set_required_security_level(gap_security_level_t security_level){
2211     rfcomm_security_level = security_level;
2212 }
2213 
2214 bool rfcomm_can_send_packet_now(uint16_t rfcomm_cid){
2215     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2216     if (!channel){
2217         log_error("send cid 0x%02x doesn't exist!", rfcomm_cid);
2218         return false;
2219     }
2220     return rfcomm_channel_can_send(channel);
2221 }
2222 
2223 uint8_t rfcomm_request_can_send_now_event(uint16_t rfcomm_cid){
2224     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2225     if (!channel) return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
2226     channel->waiting_for_can_send_now = 1;
2227     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2228     return ERROR_CODE_SUCCESS;
2229 }
2230 
2231 static uint8_t rfcomm_assert_send_valid(rfcomm_channel_t * channel , uint16_t len){
2232     if (len > channel->max_frame_size){
2233         log_error("send cid 0x%02x, rfcomm data lenght exceeds MTU!", channel->rfcomm_cid);
2234         return RFCOMM_DATA_LEN_EXCEEDS_MTU;
2235     }
2236 
2237 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2238     if (len > rfcomm_max_frame_size_for_l2cap_mtu(sizeof(outgoing_buffer))){
2239         log_error("send cid 0x%02x, length exceeds outgoing rfcomm_out_buffer", channel->rfcomm_cid);
2240         return RFCOMM_DATA_LEN_EXCEEDS_MTU;
2241     }
2242 #endif
2243 
2244     if (!channel->credits_outgoing){
2245         log_info("send cid 0x%02x, no rfcomm outgoing credits!", channel->rfcomm_cid);
2246         return RFCOMM_NO_OUTGOING_CREDITS;
2247     }
2248 
2249     if ((channel->multiplexer->fcon & 1) == 0){
2250         log_info("send cid 0x%02x, aggregate flow off!", channel->rfcomm_cid);
2251         return RFCOMM_AGGREGATE_FLOW_OFF;
2252     }
2253     return ERROR_CODE_SUCCESS;
2254 }
2255 
2256 uint16_t rfcomm_get_max_frame_size(uint16_t rfcomm_cid){
2257     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2258     if (!channel){
2259         return 0;
2260     }
2261     return channel->max_frame_size;
2262 }
2263 
2264 // pre: rfcomm_can_send_packet_now(rfcomm_cid) == true
2265 void rfcomm_reserve_packet_buffer(void){
2266 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2267     log_error("rfcomm_reserve_packet_buffer should not get called with ERTM");
2268 #else
2269     l2cap_reserve_packet_buffer();
2270 #endif
2271 }
2272 
2273 void rfcomm_release_packet_buffer(void){
2274 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2275     log_error("rfcomm_release_packet_buffer should not get called with ERTM");
2276 #else
2277     l2cap_release_packet_buffer();
2278 #endif
2279 }
2280 
2281 uint8_t * rfcomm_get_outgoing_buffer(void){
2282 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2283     uint8_t * rfcomm_out_buffer = outgoing_buffer;
2284 #else
2285     uint8_t * rfcomm_out_buffer = l2cap_get_outgoing_buffer();
2286 #endif
2287     // address + control + length (16) + no credit field
2288     return &rfcomm_out_buffer[4];
2289 }
2290 
2291 uint8_t rfcomm_send_prepared(uint16_t rfcomm_cid, uint16_t len){
2292     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2293     if (!channel){
2294         log_error("cid 0x%02x doesn't exist!", rfcomm_cid);
2295         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
2296     }
2297 
2298     uint8_t status = rfcomm_assert_send_valid(channel, len);
2299     if (status != ERROR_CODE_SUCCESS) return status;
2300 
2301 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2302     if (!l2cap_can_send_packet_now(channel->multiplexer->l2cap_cid)){
2303         log_error("l2cap cannot send now");
2304         return BTSTACK_ACL_BUFFERS_FULL;
2305     }
2306 #else
2307     if (!l2cap_can_send_prepared_packet_now(channel->multiplexer->l2cap_cid)){
2308         log_error("l2cap cannot send now");
2309         return BTSTACK_ACL_BUFFERS_FULL;
2310     }
2311 #endif
2312 
2313     // send might cause l2cap to emit new credits, update counters first
2314     if (len){
2315         channel->credits_outgoing--;
2316     } else {
2317         log_info("sending empty RFCOMM packet for cid %02x", rfcomm_cid);
2318     }
2319 
2320     status = rfcomm_send_uih_prepared(channel->multiplexer, channel->dlci, len);
2321 
2322     if (status != 0) {
2323         log_error("error %d", status);
2324         if (len) {
2325             channel->credits_outgoing++;
2326         }
2327     }
2328 
2329     return status;
2330 }
2331 
2332 uint8_t rfcomm_send(uint16_t rfcomm_cid, uint8_t *data, uint16_t len){
2333     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2334     if (!channel){
2335         log_error("cid 0x%02x doesn't exist!", rfcomm_cid);
2336         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
2337     }
2338 
2339     uint8_t status = rfcomm_assert_send_valid(channel, len);
2340     if (status != ERROR_CODE_SUCCESS) return status;
2341     if (!l2cap_can_send_packet_now(channel->multiplexer->l2cap_cid)){
2342         log_error("rfcomm_send_internal: l2cap cannot send now");
2343         return BTSTACK_ACL_BUFFERS_FULL;
2344     }
2345 
2346 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2347 #else
2348     rfcomm_reserve_packet_buffer();
2349 #endif
2350     uint8_t * rfcomm_payload = rfcomm_get_outgoing_buffer();
2351 
2352     (void)memcpy(rfcomm_payload, data, len);
2353     status = rfcomm_send_prepared(rfcomm_cid, len);
2354 
2355 #ifdef RFCOMM_USE_OUTGOING_BUFFER
2356 #else
2357     if (status != ERROR_CODE_SUCCESS){
2358         rfcomm_release_packet_buffer();
2359     }
2360 #endif
2361 
2362     return ERROR_CODE_SUCCESS;
2363 }
2364 
2365 // Sends Local Line Status, see LINE_STATUS_..
2366 uint8_t rfcomm_send_local_line_status(uint16_t rfcomm_cid, uint8_t line_status){
2367     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2368     if (!channel) return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
2369     if (channel->local_line_status != RFCOMM_RLS_STATUS_INVALID) return ERROR_CODE_COMMAND_DISALLOWED;
2370     channel->local_line_status = line_status;
2371     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2372     return ERROR_CODE_SUCCESS;
2373 }
2374 
2375 // Sned local modem status. see MODEM_STAUS_..
2376 uint8_t rfcomm_send_modem_status(uint16_t rfcomm_cid, uint8_t modem_status){
2377     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2378     if (!channel) return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
2379     channel->local_modem_status = modem_status;
2380     // trigger send
2381     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_MSC_CMD);
2382     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2383     return ERROR_CODE_SUCCESS;
2384 }
2385 
2386 // Configure remote port
2387 uint8_t 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, uint8_t flow_control){
2388     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2389     if (!channel){
2390         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
2391     }
2392 
2393     // store remote config
2394     channel->remote_rpn_data.baud_rate = baud_rate;
2395     channel->remote_rpn_data.flags = data_bits | (stop_bits << 2) | (parity << 3);
2396     channel->remote_rpn_data.flow_control = flow_control;
2397     channel->remote_rpn_data.xon = 0;
2398     channel->remote_rpn_data.xoff = 0;
2399     channel->remote_rpn_data.parameter_mask_0 = 0x1f;   // all but xon/xoff
2400     channel->remote_rpn_data.parameter_mask_1 = 0x3f;   // all flow control options
2401 
2402     // trigger send
2403     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_CONFIG);
2404     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2405     return ERROR_CODE_SUCCESS;
2406 }
2407 
2408 // Query remote port
2409 uint8_t rfcomm_query_port_configuration(uint16_t rfcomm_cid){
2410     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2411     if (!channel){
2412         return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
2413     }
2414     // trigger send
2415     rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_RPN_QUERY | RFCOMM_CHANNEL_STATE_VAR_EMIT_RPN_RESPONSE);
2416     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2417     return ERROR_CODE_SUCCESS;
2418 }
2419 
2420 
2421 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){
2422     log_info("create addr %s channel #%u init credits %u",  bd_addr_to_str(addr), server_channel, initial_credits);
2423 
2424     // create new multiplexer if necessary
2425     uint8_t status = 0;
2426     uint8_t dlci = 0;
2427     int new_multiplexer = 0;
2428     rfcomm_channel_t * channel = NULL;
2429     rfcomm_multiplexer_t * multiplexer = rfcomm_multiplexer_for_addr(addr);
2430     if (!multiplexer) {
2431         multiplexer = rfcomm_multiplexer_create_for_addr(addr);
2432         if (!multiplexer) return BTSTACK_MEMORY_ALLOC_FAILED;
2433 
2434         multiplexer->outgoing = 1;
2435         multiplexer->state = RFCOMM_MULTIPLEXER_W4_CONNECT;
2436         new_multiplexer = 1;
2437     }
2438 
2439     // check if channel for this remote service already exists
2440     dlci = (server_channel << 1) | (multiplexer->outgoing ^ 1);
2441     channel = rfcomm_channel_for_multiplexer_and_dlci(multiplexer, dlci);
2442     if (channel){
2443         if (new_multiplexer) btstack_memory_rfcomm_multiplexer_free(multiplexer);
2444         return RFCOMM_CHANNEL_ALREADY_REGISTERED;
2445     }
2446 
2447     // prepare channel
2448     channel = rfcomm_channel_create(multiplexer, NULL, server_channel);
2449     if (!channel){
2450         if (new_multiplexer) btstack_memory_rfcomm_multiplexer_free(multiplexer);
2451         return BTSTACK_MEMORY_ALLOC_FAILED;
2452     }
2453 
2454     // rfcomm_cid is already assigned by rfcomm_channel_create
2455     channel->incoming_flow_control = incoming_flow_control;
2456     channel->new_credits_incoming  = initial_credits;
2457     channel->packet_handler = packet_handler;
2458 
2459     // return rfcomm_cid
2460     if (out_rfcomm_cid){
2461         *out_rfcomm_cid = channel->rfcomm_cid;
2462     }
2463 
2464     // start multiplexer setup
2465     if (multiplexer->state != RFCOMM_MULTIPLEXER_OPEN) {
2466         channel->state = RFCOMM_CHANNEL_W4_MULTIPLEXER;
2467         uint16_t l2cap_cid = 0;
2468 #ifdef RFCOMM_USE_ERTM
2469         // request
2470         rfcomm_ertm_request_t request;
2471         memset(&request, 0, sizeof(rfcomm_ertm_request_t));
2472         (void)memcpy(request.addr, addr, 6);
2473         request.ertm_id = rfcomm_next_ertm_id();
2474         if (rfcomm_ertm_request_callback){
2475             (*rfcomm_ertm_request_callback)(&request);
2476         }
2477         if (request.ertm_config && request.ertm_buffer && request.ertm_buffer_size){
2478             multiplexer->ertm_id = request.ertm_id;
2479             status = l2cap_ertm_create_channel(rfcomm_packet_handler, addr, BLUETOOTH_PROTOCOL_RFCOMM,
2480                         request.ertm_config, request.ertm_buffer, request.ertm_buffer_size, &l2cap_cid);
2481         }
2482         else
2483 #endif
2484         {
2485             status = l2cap_create_channel(rfcomm_packet_handler, addr, BLUETOOTH_PROTOCOL_RFCOMM, l2cap_max_mtu(), &l2cap_cid);
2486         }
2487         if (status) {
2488             if (new_multiplexer) btstack_memory_rfcomm_multiplexer_free(multiplexer);
2489             btstack_memory_rfcomm_channel_free(channel);
2490             return status;
2491         }
2492         multiplexer->l2cap_cid = l2cap_cid;
2493         return ERROR_CODE_SUCCESS;
2494     }
2495 
2496     channel->state = RFCOMM_CHANNEL_SEND_UIH_PN;
2497 
2498     // start connecting, if multiplexer is already up and running
2499     l2cap_request_can_send_now_event(multiplexer->l2cap_cid);
2500     return ERROR_CODE_SUCCESS;
2501 }
2502 
2503 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){
2504     return rfcomm_channel_create_internal(packet_handler, addr, server_channel, 1, initial_credits, out_rfcomm_cid);
2505 }
2506 
2507 uint8_t rfcomm_create_channel(btstack_packet_handler_t packet_handler, bd_addr_t addr, uint8_t server_channel, uint16_t * out_rfcomm_cid){
2508     return rfcomm_channel_create_internal(packet_handler, addr, server_channel, 0, RFCOMM_CREDITS, out_rfcomm_cid);
2509 }
2510 
2511 uint8_t rfcomm_disconnect(uint16_t rfcomm_cid){
2512     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2513     if (!channel) return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
2514 
2515     if (channel->state != RFCOMM_CHANNEL_OPEN) return ERROR_CODE_COMMAND_DISALLOWED;
2516 
2517     log_info("disconnect cid 0x%02x", rfcomm_cid);
2518     channel->state = RFCOMM_CHANNEL_SEND_DISC;
2519     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2520     return ERROR_CODE_SUCCESS;
2521 }
2522 
2523 static uint8_t rfcomm_register_service_internal(btstack_packet_handler_t packet_handler,
2524     uint8_t channel, uint16_t max_frame_size, uint8_t incoming_flow_control, uint8_t initial_credits){
2525 
2526     log_info("register channel #%u mtu %u flow_control %u credits %u",
2527              channel, max_frame_size, incoming_flow_control, initial_credits);
2528 
2529     // check if already registered
2530     rfcomm_service_t * service = rfcomm_service_for_channel(channel);
2531     if (service){
2532         return RFCOMM_CHANNEL_ALREADY_REGISTERED;
2533     }
2534 
2535     // alloc structure
2536     service = btstack_memory_rfcomm_service_get();
2537     if (!service) {
2538         return BTSTACK_MEMORY_ALLOC_FAILED;
2539     }
2540 
2541     // register with l2cap if not registered before, max MTU
2542     if (btstack_linked_list_empty(&rfcomm_services)){
2543         uint8_t status = l2cap_register_service(rfcomm_packet_handler, BLUETOOTH_PROTOCOL_RFCOMM, 0xffff, rfcomm_security_level);
2544         if (status != ERROR_CODE_SUCCESS){
2545             btstack_memory_rfcomm_service_free(service);
2546             return status;
2547         }
2548     }
2549 
2550     // fill in
2551     service->packet_handler = packet_handler;
2552     service->server_channel = channel;
2553     service->max_frame_size = max_frame_size;
2554     service->incoming_flow_control = incoming_flow_control;
2555     service->incoming_initial_credits = initial_credits;
2556 
2557     // add to services list
2558     btstack_linked_list_add(&rfcomm_services, (btstack_linked_item_t *) service);
2559 
2560     return ERROR_CODE_SUCCESS;
2561 }
2562 
2563 uint8_t rfcomm_register_service_with_initial_credits(btstack_packet_handler_t packet_handler,
2564     uint8_t channel, uint16_t max_frame_size, uint8_t initial_credits){
2565 
2566     return rfcomm_register_service_internal(packet_handler, channel, max_frame_size, 1, initial_credits);
2567 }
2568 
2569 uint8_t rfcomm_register_service(btstack_packet_handler_t packet_handler, uint8_t channel,
2570     uint16_t max_frame_size){
2571 
2572     return rfcomm_register_service_internal(packet_handler, channel, max_frame_size, 0,RFCOMM_CREDITS);
2573 }
2574 
2575 void rfcomm_unregister_service(uint8_t service_channel){
2576     rfcomm_service_t *service = rfcomm_service_for_channel(service_channel);
2577     if (!service) return;
2578     btstack_linked_list_remove(&rfcomm_services, (btstack_linked_item_t *) service);
2579     btstack_memory_rfcomm_service_free(service);
2580 
2581     // unregister if no services active
2582     if (btstack_linked_list_empty(&rfcomm_services)){
2583         // bt_send_cmd(&l2cap_unregister_service, BLUETOOTH_PROTOCOL_RFCOMM);
2584         l2cap_unregister_service(BLUETOOTH_PROTOCOL_RFCOMM);
2585     }
2586 }
2587 
2588 uint8_t rfcomm_accept_connection(uint16_t rfcomm_cid){
2589     log_info("accept cid 0x%02x", rfcomm_cid);
2590     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2591     if (!channel) return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
2592 
2593     switch (channel->state) {
2594         case RFCOMM_CHANNEL_INCOMING_SETUP:
2595             rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_CLIENT_ACCEPTED);
2596             if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_PN){
2597                 rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_PN_RSP);
2598                 l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2599             }
2600             if (channel->state_var & RFCOMM_CHANNEL_STATE_VAR_RCVD_SABM){
2601                 rfcomm_channel_state_add(channel, RFCOMM_CHANNEL_STATE_VAR_SEND_UA);
2602                 l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2603             }
2604             // at least one of { PN RSP, UA } needs to be sent
2605             // state transistion incoming setup -> dlc setup happens in rfcomm_run after these have been sent
2606             return ERROR_CODE_SUCCESS;
2607         default:
2608            return ERROR_CODE_COMMAND_DISALLOWED;
2609     }
2610 }
2611 
2612 uint8_t rfcomm_decline_connection(uint16_t rfcomm_cid){
2613     log_info("decline cid 0x%02x", rfcomm_cid);
2614     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2615     if (!channel) return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
2616 
2617     switch (channel->state) {
2618         case RFCOMM_CHANNEL_INCOMING_SETUP:
2619             channel->state = RFCOMM_CHANNEL_SEND_DM;
2620             l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2621             return ERROR_CODE_SUCCESS;
2622         default:
2623             return ERROR_CODE_COMMAND_DISALLOWED;
2624     }
2625 }
2626 
2627 uint8_t rfcomm_grant_credits(uint16_t rfcomm_cid, uint8_t credits){
2628     log_info("grant cid 0x%02x credits %u", rfcomm_cid, credits);
2629     rfcomm_channel_t * channel = rfcomm_channel_for_rfcomm_cid(rfcomm_cid);
2630     if (!channel) return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
2631     if (!channel->incoming_flow_control) return ERROR_CODE_COMMAND_DISALLOWED;
2632     channel->new_credits_incoming += credits;
2633 
2634     // process
2635     l2cap_request_can_send_now_event(channel->multiplexer->l2cap_cid);
2636     return ERROR_CODE_SUCCESS;
2637 }
2638 
2639 #ifdef RFCOMM_USE_ERTM
2640 void rfcomm_enable_l2cap_ertm(void request_callback(rfcomm_ertm_request_t * request), void released_callback(uint16_t ertm_id)){
2641     rfcomm_ertm_request_callback  = request_callback;
2642     rfcomm_ertm_released_callback = released_callback;
2643 }
2644 #endif
2645