aboutsummaryrefslogtreecommitdiff
path: root/lib/rtsp.c
blob: 5da33d42cf054ee62b61356521ad71ad9ffc5059 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.haxx.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ***************************************************************************/

#include "curl_setup.h"

#ifndef CURL_DISABLE_RTSP

#include "urldata.h"
#include <curl/curl.h>
#include "transfer.h"
#include "sendf.h"
#include "multiif.h"
#include "http.h"
#include "url.h"
#include "progress.h"
#include "rtsp.h"
#include "strcase.h"
#include "select.h"
#include "connect.h"
#include "strdup.h"
/* The last 3 #include files should be in this order */
#include "curl_printf.h"
#include "curl_memory.h"
#include "memdebug.h"

/*
 * TODO (general)
 *  -incoming server requests
 *      -server CSeq counter
 *  -digest authentication
 *  -connect thru proxy
 *  -pipelining?
 */


#define RTP_PKT_CHANNEL(p)   ((int)((unsigned char)((p)[1])))

#define RTP_PKT_LENGTH(p)  ((((int)((unsigned char)((p)[2]))) << 8) | \
                             ((int)((unsigned char)((p)[3]))))

/* protocol-specific functions set up to be called by the main engine */
static CURLcode rtsp_do(struct connectdata *conn, bool *done);
static CURLcode rtsp_done(struct connectdata *conn, CURLcode, bool premature);
static CURLcode rtsp_connect(struct connectdata *conn, bool *done);
static CURLcode rtsp_disconnect(struct connectdata *conn, bool dead);

static int rtsp_getsock_do(struct connectdata *conn,
                           curl_socket_t *socks,
                           int numsocks);

/*
 * Parse and write out any available RTP data.
 *
 * nread: amount of data left after k->str. will be modified if RTP
 *        data is parsed and k->str is moved up
 * readmore: whether or not the RTP parser needs more data right away
 */
static CURLcode rtsp_rtp_readwrite(struct Curl_easy *data,
                                   struct connectdata *conn,
                                   ssize_t *nread,
                                   bool *readmore);

static CURLcode rtsp_setup_connection(struct connectdata *conn);


/* this returns the socket to wait for in the DO and DOING state for the multi
   interface and then we're always _sending_ a request and thus we wait for
   the single socket to become writable only */
static int rtsp_getsock_do(struct connectdata *conn,
                           curl_socket_t *socks,
                           int numsocks)
{
  /* write mode */
  (void)numsocks; /* unused, we trust it to be at least 1 */
  socks[0] = conn->sock[FIRSTSOCKET];
  return GETSOCK_WRITESOCK(0);
}

static
CURLcode rtp_client_write(struct connectdata *conn, char *ptr, size_t len);


/*
 * RTSP handler interface.
 */
const struct Curl_handler Curl_handler_rtsp = {
  "RTSP",                               /* scheme */
  rtsp_setup_connection,                /* setup_connection */
  rtsp_do,                              /* do_it */
  rtsp_done,                            /* done */
  ZERO_NULL,                            /* do_more */
  rtsp_connect,                         /* connect_it */
  ZERO_NULL,                            /* connecting */
  ZERO_NULL,                            /* doing */
  ZERO_NULL,                            /* proto_getsock */
  rtsp_getsock_do,                      /* doing_getsock */
  ZERO_NULL,                            /* domore_getsock */
  ZERO_NULL,                            /* perform_getsock */
  rtsp_disconnect,                      /* disconnect */
  rtsp_rtp_readwrite,                   /* readwrite */
  PORT_RTSP,                            /* defport */
  CURLPROTO_RTSP,                       /* protocol */
  PROTOPT_NONE                          /* flags */
};


static CURLcode rtsp_setup_connection(struct connectdata *conn)
{
  struct RTSP *rtsp;

  conn->data->req.protop = rtsp = calloc(1, sizeof(struct RTSP));
  if(!rtsp)
    return CURLE_OUT_OF_MEMORY;

  return CURLE_OK;
}


/*
 * The server may send us RTP data at any point, and RTSPREQ_RECEIVE does not
 * want to block the application forever while receiving a stream. Therefore,
 * we cannot assume that an RTSP socket is dead just because it is readable.
 *
 * Instead, if it is readable, run Curl_getconnectinfo() to peek at the socket
 * and distinguish between closed and data.
 */
bool Curl_rtsp_connisdead(struct connectdata *check)
{
  int sval;
  bool ret_val = TRUE;

  sval = SOCKET_READABLE(check->sock[FIRSTSOCKET], 0);
  if(sval == 0) {
    /* timeout */
    ret_val = FALSE;
  }
  else if(sval & CURL_CSELECT_ERR) {
    /* socket is in an error state */
    ret_val = TRUE;
  }
  else if((sval & CURL_CSELECT_IN) && check->data) {
    /* readable with no error. could be closed or could be alive but we can
       only check if we have a proper Curl_easy for the connection */
    curl_socket_t connectinfo = Curl_getconnectinfo(check->data, &check);
    if(connectinfo != CURL_SOCKET_BAD)
      ret_val = FALSE;
  }

  return ret_val;
}

static CURLcode rtsp_connect(struct connectdata *conn, bool *done)
{
  CURLcode httpStatus;
  struct Curl_easy *data = conn->data;

  httpStatus = Curl_http_connect(conn, done);

  /* Initialize the CSeq if not already done */
  if(data->state.rtsp_next_client_CSeq == 0)
    data->state.rtsp_next_client_CSeq = 1;
  if(data->state.rtsp_next_server_CSeq == 0)
    data->state.rtsp_next_server_CSeq = 1;

  conn->proto.rtspc.rtp_channel = -1;

  return httpStatus;
}

static CURLcode rtsp_disconnect(struct connectdata *conn, bool dead)
{
  (void) dead;
  Curl_safefree(conn->proto.rtspc.rtp_buf);
  return CURLE_OK;
}


static CURLcode rtsp_done(struct connectdata *conn,
                          CURLcode status, bool premature)
{
  struct Curl_easy *data = conn->data;
  struct RTSP *rtsp = data->req.protop;
  CURLcode httpStatus;
  long CSeq_sent;
  long CSeq_recv;

  /* Bypass HTTP empty-reply checks on receive */
  if(data->set.rtspreq == RTSPREQ_RECEIVE)
    premature = TRUE;

  httpStatus = Curl_http_done(conn, status, premature);

  if(rtsp) {
    /* Check the sequence numbers */
    CSeq_sent = rtsp->CSeq_sent;
    CSeq_recv = rtsp->CSeq_recv;
    if((data->set.rtspreq != RTSPREQ_RECEIVE) && (CSeq_sent != CSeq_recv)) {
      failf(data,
            "The CSeq of this request %ld did not match the response %ld",
            CSeq_sent, CSeq_recv);
      return CURLE_RTSP_CSEQ_ERROR;
    }
    else if(data->set.rtspreq == RTSPREQ_RECEIVE &&
            (conn->proto.rtspc.rtp_channel == -1)) {
      infof(data, "Got an RTP Receive with a CSeq of %ld\n", CSeq_recv);
      /* TODO CPC: Server -> Client logic here */
    }
  }

  return httpStatus;
}

static CURLcode rtsp_do(struct connectdata *conn, bool *done)
{
  struct Curl_easy *data = conn->data;
  CURLcode result=CURLE_OK;
  Curl_RtspReq rtspreq = data->set.rtspreq;
  struct RTSP *rtsp = data->req.protop;
  struct HTTP *http;
  Curl_send_buffer *req_buffer;
  curl_off_t postsize = 0; /* for ANNOUNCE and SET_PARAMETER */
  curl_off_t putsize = 0; /* for ANNOUNCE and SET_PARAMETER */

  const char *p_request = NULL;
  const char *p_session_id = NULL;
  const char *p_accept = NULL;
  const char *p_accept_encoding = NULL;
  const char *p_range = NULL;
  const char *p_referrer = NULL;
  const char *p_stream_uri = NULL;
  const char *p_transport = NULL;
  const char *p_uagent = NULL;
  const char *p_proxyuserpwd = NULL;
  const char *p_userpwd = NULL;

  *done = TRUE;

  http = &(rtsp->http_wrapper);
  /* Assert that no one has changed the RTSP struct in an evil way */
  DEBUGASSERT((void *)http == (void *)rtsp);

  rtsp->CSeq_sent = data->state.rtsp_next_client_CSeq;
  rtsp->CSeq_recv = 0;

  /* Setup the 'p_request' pointer to the proper p_request string
   * Since all RTSP requests are included here, there is no need to
   * support custom requests like HTTP.
   **/
  data->set.opt_no_body = TRUE; /* most requests don't contain a body */
  switch(rtspreq) {
  default:
    failf(data, "Got invalid RTSP request");
    return CURLE_BAD_FUNCTION_ARGUMENT;
  case RTSPREQ_OPTIONS:
    p_request = "OPTIONS";
    break;
  case RTSPREQ_DESCRIBE:
    p_request = "DESCRIBE";
    data->set.opt_no_body = FALSE;
    break;
  case RTSPREQ_ANNOUNCE:
    p_request = "ANNOUNCE";
    break;
  case RTSPREQ_SETUP:
    p_request = "SETUP";
    break;
  case RTSPREQ_PLAY:
    p_request = "PLAY";
    break;
  case RTSPREQ_PAUSE:
    p_request = "PAUSE";
    break;
  case RTSPREQ_TEARDOWN:
    p_request = "TEARDOWN";
    break;
  case RTSPREQ_GET_PARAMETER:
    /* GET_PARAMETER's no_body status is determined later */
    p_request = "GET_PARAMETER";
    data->set.opt_no_body = FALSE;
    break;
  case RTSPREQ_SET_PARAMETER:
    p_request = "SET_PARAMETER";
    break;
  case RTSPREQ_RECORD:
    p_request = "RECORD";
    break;
  case RTSPREQ_RECEIVE:
    p_request = "";
    /* Treat interleaved RTP as body*/
    data->set.opt_no_body = FALSE;
    break;
  case RTSPREQ_LAST:
    failf(data, "Got invalid RTSP request: RTSPREQ_LAST");
    return CURLE_BAD_FUNCTION_ARGUMENT;
  }

  if(rtspreq == RTSPREQ_RECEIVE) {
    Curl_setup_transfer(conn, FIRSTSOCKET, -1, TRUE,
                        &http->readbytecount, -1, NULL);

    return result;
  }

  p_session_id = data->set.str[STRING_RTSP_SESSION_ID];
  if(!p_session_id &&
     (rtspreq & ~(RTSPREQ_OPTIONS | RTSPREQ_DESCRIBE | RTSPREQ_SETUP))) {
    failf(data, "Refusing to issue an RTSP request [%s] without a session ID.",
          p_request);
    return CURLE_BAD_FUNCTION_ARGUMENT;
  }

  /* TODO: proxy? */

  /* Stream URI. Default to server '*' if not specified */
  if(data->set.str[STRING_RTSP_STREAM_URI]) {
    p_stream_uri = data->set.str[STRING_RTSP_STREAM_URI];
  }
  else {
    p_stream_uri = "*";
  }

  /* Transport Header for SETUP requests */
  p_transport = Curl_checkheaders(conn, "Transport:");
  if(rtspreq == RTSPREQ_SETUP && !p_transport) {
    /* New Transport: setting? */
    if(data->set.str[STRING_RTSP_TRANSPORT]) {
      Curl_safefree(conn->allocptr.rtsp_transport);

      conn->allocptr.rtsp_transport =
        aprintf("Transport: %s\r\n",
                data->set.str[STRING_RTSP_TRANSPORT]);
      if(!conn->allocptr.rtsp_transport)
        return CURLE_OUT_OF_MEMORY;
    }
    else {
      failf(data,
            "Refusing to issue an RTSP SETUP without a Transport: header.");
      return CURLE_BAD_FUNCTION_ARGUMENT;
    }

    p_transport = conn->allocptr.rtsp_transport;
  }

  /* Accept Headers for DESCRIBE requests */
  if(rtspreq == RTSPREQ_DESCRIBE) {
    /* Accept Header */
    p_accept = Curl_checkheaders(conn, "Accept:")?
      NULL:"Accept: application/sdp\r\n";

    /* Accept-Encoding header */
    if(!Curl_checkheaders(conn, "Accept-Encoding:") &&
       data->set.str[STRING_ENCODING]) {
      Curl_safefree(conn->allocptr.accept_encoding);
      conn->allocptr.accept_encoding =
        aprintf("Accept-Encoding: %s\r\n", data->set.str[STRING_ENCODING]);

      if(!conn->allocptr.accept_encoding)
        return CURLE_OUT_OF_MEMORY;

      p_accept_encoding = conn->allocptr.accept_encoding;
    }
  }

  /* The User-Agent string might have been allocated in url.c already, because
     it might have been used in the proxy connect, but if we have got a header
     with the user-agent string specified, we erase the previously made string
     here. */
  if(Curl_checkheaders(conn, "User-Agent:") && conn->allocptr.uagent) {
    Curl_safefree(conn->allocptr.uagent);
    conn->allocptr.uagent = NULL;
  }
  else if(!Curl_checkheaders(conn, "User-Agent:") &&
          data->set.str[STRING_USERAGENT]) {
    p_uagent = conn->allocptr.uagent;
  }

  /* setup the authentication headers */
  result = Curl_http_output_auth(conn, p_request, p_stream_uri, FALSE);
  if(result)
    return result;

  p_proxyuserpwd = conn->allocptr.proxyuserpwd;
  p_userpwd = conn->allocptr.userpwd;

  /* Referrer */
  Curl_safefree(conn->allocptr.ref);
  if(data->change.referer && !Curl_checkheaders(conn, "Referer:"))
    conn->allocptr.ref = aprintf("Referer: %s\r\n", data->change.referer);
  else
    conn->allocptr.ref = NULL;

  p_referrer = conn->allocptr.ref;

  /*
   * Range Header
   * Only applies to PLAY, PAUSE, RECORD
   *
   * Go ahead and use the Range stuff supplied for HTTP
   */
  if(data->state.use_range &&
     (rtspreq  & (RTSPREQ_PLAY | RTSPREQ_PAUSE | RTSPREQ_RECORD))) {

    /* Check to see if there is a range set in the custom headers */
    if(!Curl_checkheaders(conn, "Range:") && data->state.range) {
      Curl_safefree(conn->allocptr.rangeline);
      conn->allocptr.rangeline = aprintf("Range: %s\r\n", data->state.range);
      p_range = conn->allocptr.rangeline;
    }
  }

  /*
   * Sanity check the custom headers
   */
  if(Curl_checkheaders(conn, "CSeq:")) {
    failf(data, "CSeq cannot be set as a custom header.");
    return CURLE_RTSP_CSEQ_ERROR;
  }
  if(Curl_checkheaders(conn, "Session:")) {
    failf(data, "Session ID cannot be set as a custom header.");
    return CURLE_BAD_FUNCTION_ARGUMENT;
  }

  /* Initialize a dynamic send buffer */
  req_buffer = Curl_add_buffer_init();

  if(!req_buffer)
    return CURLE_OUT_OF_MEMORY;

  result =
    Curl_add_bufferf(req_buffer,
                     "%s %s RTSP/1.0\r\n" /* Request Stream-URI RTSP/1.0 */
                     "CSeq: %ld\r\n", /* CSeq */
                     p_request, p_stream_uri, rtsp->CSeq_sent);
  if(result)
    return result;

  /*
   * Rather than do a normal alloc line, keep the session_id unformatted
   * to make comparison easier
   */
  if(p_session_id) {
    result = Curl_add_bufferf(req_buffer, "Session: %s\r\n", p_session_id);
    if(result)
      return result;
  }

  /*
   * Shared HTTP-like options
   */
  result = Curl_add_bufferf(req_buffer,
                            "%s" /* transport */
                            "%s" /* accept */
                            "%s" /* accept-encoding */
                            "%s" /* range */
                            "%s" /* referrer */
                            "%s" /* user-agent */
                            "%s" /* proxyuserpwd */
                            "%s" /* userpwd */
                            ,
                            p_transport ? p_transport : "",
                            p_accept ? p_accept : "",
                            p_accept_encoding ? p_accept_encoding : "",
                            p_range ? p_range : "",
                            p_referrer ? p_referrer : "",
                            p_uagent ? p_uagent : "",
                            p_proxyuserpwd ? p_proxyuserpwd : "",
                            p_userpwd ? p_userpwd : "");

  /*
   * Free userpwd now --- cannot reuse this for Negotiate and possibly NTLM
   * with basic and digest, it will be freed anyway by the next request
   */
  Curl_safefree (conn->allocptr.userpwd);
  conn->allocptr.userpwd = NULL;

  if(result)
    return result;

  if((rtspreq == RTSPREQ_SETUP) || (rtspreq == RTSPREQ_DESCRIBE)) {
    result = Curl_add_timecondition(data, req_buffer);
    if(result)
      return result;
  }

  result = Curl_add_custom_headers(conn, FALSE, req_buffer);
  if(result)
    return result;

  if(rtspreq == RTSPREQ_ANNOUNCE ||
     rtspreq == RTSPREQ_SET_PARAMETER ||
     rtspreq == RTSPREQ_GET_PARAMETER) {

    if(data->set.upload) {
      putsize = data->state.infilesize;
      data->set.httpreq = HTTPREQ_PUT;

    }
    else {
      postsize = (data->state.infilesize != -1)?
        data->state.infilesize:
        (data->set.postfields? (curl_off_t)strlen(data->set.postfields):0);
      data->set.httpreq = HTTPREQ_POST;
    }

    if(putsize > 0 || postsize > 0) {
      /* As stated in the http comments, it is probably not wise to
       * actually set a custom Content-Length in the headers */
      if(!Curl_checkheaders(conn, "Content-Length:")) {
        result = Curl_add_bufferf(req_buffer,
            "Content-Length: %" CURL_FORMAT_CURL_OFF_T"\r\n",
            (data->set.upload ? putsize : postsize));
        if(result)
          return result;
      }

      if(rtspreq == RTSPREQ_SET_PARAMETER ||
         rtspreq == RTSPREQ_GET_PARAMETER) {
        if(!Curl_checkheaders(conn, "Content-Type:")) {
          result = Curl_add_bufferf(req_buffer,
              "Content-Type: text/parameters\r\n");
          if(result)
            return result;
        }
      }

      if(rtspreq == RTSPREQ_ANNOUNCE) {
        if(!Curl_checkheaders(conn, "Content-Type:")) {
          result = Curl_add_bufferf(req_buffer,
              "Content-Type: application/sdp\r\n");
          if(result)
            return result;
        }
      }

      data->state.expect100header = FALSE; /* RTSP posts are simple/small */
    }
    else if(rtspreq == RTSPREQ_GET_PARAMETER) {
      /* Check for an empty GET_PARAMETER (heartbeat) request */
      data->set.httpreq = HTTPREQ_HEAD;
      data->set.opt_no_body = TRUE;
    }
  }

  /* RTSP never allows chunked transfer */
  data->req.forbidchunk = TRUE;
  /* Finish the request buffer */
  result = Curl_add_buffer(req_buffer, "\r\n", 2);
  if(result)
    return result;

  if(postsize > 0) {
    result = Curl_add_buffer(req_buffer, data->set.postfields,
                             (size_t)postsize);
    if(result)
      return result;
  }

  /* issue the request */
  result = Curl_add_buffer_send(req_buffer, conn,
                                &data->info.request_size, 0, FIRSTSOCKET);
  if(result) {
    failf(data, "Failed sending RTSP request");
    return result;
  }

  Curl_setup_transfer(conn, FIRSTSOCKET, -1, TRUE, &http->readbytecount,
                      putsize?FIRSTSOCKET:-1,
                      putsize?&http->writebytecount:NULL);

  /* Increment the CSeq on success */
  data->state.rtsp_next_client_CSeq++;

  if(http->writebytecount) {
    /* if a request-body has been sent off, we make sure this progress is
       noted properly */
    Curl_pgrsSetUploadCounter(data, http->writebytecount);
    if(Curl_pgrsUpdate(conn))
      result = CURLE_ABORTED_BY_CALLBACK;
  }

  return result;
}


static CURLcode rtsp_rtp_readwrite(struct Curl_easy *data,
                                   struct connectdata *conn,
                                   ssize_t *nread,
                                   bool *readmore) {
  struct SingleRequest *k = &data->req;
  struct rtsp_conn *rtspc = &(conn->proto.rtspc);

  char *rtp; /* moving pointer to rtp data */
  ssize_t rtp_dataleft; /* how much data left to parse in this round */
  char *scratch;
  CURLcode result;

  if(rtspc->rtp_buf) {
    /* There was some leftover data the last time. Merge buffers */
    char *newptr = Curl_saferealloc(rtspc->rtp_buf,
                                    rtspc->rtp_bufsize + *nread);
    if(!newptr) {
      rtspc->rtp_buf = NULL;
      rtspc->rtp_bufsize = 0;
      return CURLE_OUT_OF_MEMORY;
    }
    rtspc->rtp_buf = newptr;
    memcpy(rtspc->rtp_buf + rtspc->rtp_bufsize, k->str, *nread);
    rtspc->rtp_bufsize += *nread;
    rtp = rtspc->rtp_buf;
    rtp_dataleft = rtspc->rtp_bufsize;
  }
  else {
    /* Just parse the request buffer directly */
    rtp = k->str;
    rtp_dataleft = *nread;
  }

  while((rtp_dataleft > 0) &&
        (rtp[0] == '$')) {
    if(rtp_dataleft > 4) {
      int rtp_length;

      /* Parse the header */
      /* The channel identifier immediately follows and is 1 byte */
      rtspc->rtp_channel = RTP_PKT_CHANNEL(rtp);

      /* The length is two bytes */
      rtp_length = RTP_PKT_LENGTH(rtp);

      if(rtp_dataleft < rtp_length + 4) {
        /* Need more - incomplete payload*/
        *readmore = TRUE;
        break;
      }
      else {
        /* We have the full RTP interleaved packet
         * Write out the header including the leading '$' */
        DEBUGF(infof(data, "RTP write channel %d rtp_length %d\n",
              rtspc->rtp_channel, rtp_length));
        result = rtp_client_write(conn, &rtp[0], rtp_length + 4);
        if(result) {
          failf(data, "Got an error writing an RTP packet");
          *readmore = FALSE;
          Curl_safefree(rtspc->rtp_buf);
          rtspc->rtp_buf = NULL;
          rtspc->rtp_bufsize = 0;
          return result;
        }

        /* Move forward in the buffer */
        rtp_dataleft -= rtp_length + 4;
        rtp += rtp_length + 4;

        if(data->set.rtspreq == RTSPREQ_RECEIVE) {
          /* If we are in a passive receive, give control back
           * to the app as often as we can.
           */
          k->keepon &= ~KEEP_RECV;
        }
      }
    }
    else {
      /* Need more - incomplete header */
      *readmore = TRUE;
      break;
    }
  }

  if(rtp_dataleft != 0 && rtp[0] == '$') {
    DEBUGF(infof(data, "RTP Rewinding %zd %s\n", rtp_dataleft,
          *readmore ? "(READMORE)" : ""));

    /* Store the incomplete RTP packet for a "rewind" */
    scratch = malloc(rtp_dataleft);
    if(!scratch) {
      Curl_safefree(rtspc->rtp_buf);
      rtspc->rtp_buf = NULL;
      rtspc->rtp_bufsize = 0;
      return CURLE_OUT_OF_MEMORY;
    }
    memcpy(scratch, rtp, rtp_dataleft);
    Curl_safefree(rtspc->rtp_buf);
    rtspc->rtp_buf = scratch;
    rtspc->rtp_bufsize = rtp_dataleft;

    /* As far as the transfer is concerned, this data is consumed */
    *nread = 0;
    return CURLE_OK;
  }
  else {
    /* Fix up k->str to point just after the last RTP packet */
    k->str += *nread - rtp_dataleft;

    /* either all of the data has been read or...
     * rtp now points at the next byte to parse
     */
    if(rtp_dataleft > 0)
      DEBUGASSERT(k->str[0] == rtp[0]);

    DEBUGASSERT(rtp_dataleft <= *nread); /* sanity check */

    *nread = rtp_dataleft;
  }

  /* If we get here, we have finished with the leftover/merge buffer */
  Curl_safefree(rtspc->rtp_buf);
  rtspc->rtp_buf = NULL;
  rtspc->rtp_bufsize = 0;

  return CURLE_OK;
}

static
CURLcode rtp_client_write(struct connectdata *conn, char *ptr, size_t len)
{
  struct Curl_easy *data = conn->data;
  size_t wrote;
  curl_write_callback writeit;

  if(len == 0) {
    failf (data, "Cannot write a 0 size RTP packet.");
    return CURLE_WRITE_ERROR;
  }

  writeit = data->set.fwrite_rtp?data->set.fwrite_rtp:data->set.fwrite_func;
  wrote = writeit(ptr, 1, len, data->set.rtp_out);

  if(CURL_WRITEFUNC_PAUSE == wrote) {
    failf (data, "Cannot pause RTP");
    return CURLE_WRITE_ERROR;
  }

  if(wrote != len) {
    failf (data, "Failed writing RTP data");
    return CURLE_WRITE_ERROR;
  }

  return CURLE_OK;
}

CURLcode Curl_rtsp_parseheader(struct connectdata *conn,
                               char *header)
{
  struct Curl_easy *data = conn->data;
  long CSeq = 0;

  if(checkprefix("CSeq:", header)) {
    /* Store the received CSeq. Match is verified in rtsp_done */
    int nc = sscanf(&header[4], ": %ld", &CSeq);
    if(nc == 1) {
      struct RTSP *rtsp = data->req.protop;
      rtsp->CSeq_recv = CSeq; /* mark the request */
      data->state.rtsp_CSeq_recv = CSeq; /* update the handle */
    }
    else {
      failf(data, "Unable to read the CSeq header: [%s]", header);
      return CURLE_RTSP_CSEQ_ERROR;
    }
  }
  else if(checkprefix("Session:", header)) {
    char *start;

    /* Find the first non-space letter */
    start = header + 8;
    while(*start && ISSPACE(*start))
      start++;

    if(!*start) {
      failf(data, "Got a blank Session ID");
    }
    else if(data->set.str[STRING_RTSP_SESSION_ID]) {
      /* If the Session ID is set, then compare */
      if(strncmp(start, data->set.str[STRING_RTSP_SESSION_ID],
                 strlen(data->set.str[STRING_RTSP_SESSION_ID]))  != 0) {
        failf(data, "Got RTSP Session ID Line [%s], but wanted ID [%s]",
              start, data->set.str[STRING_RTSP_SESSION_ID]);
        return CURLE_RTSP_SESSION_ERROR;
      }
    }
    else {
      /* If the Session ID is not set, and we find it in a response, then set
       * it.
       *
       * Allow any non whitespace content, up to the field seperator or end of
       * line. RFC 2326 isn't 100% clear on the session ID and for example
       * gstreamer does url-encoded session ID's not covered by the standard.
       */
      char *end = start;
      while(*end && *end != ';' && !ISSPACE(*end))
        end++;

      /* Copy the id substring into a new buffer */
      data->set.str[STRING_RTSP_SESSION_ID] = malloc(end - start + 1);
      if(data->set.str[STRING_RTSP_SESSION_ID] == NULL)
        return CURLE_OUT_OF_MEMORY;
      memcpy(data->set.str[STRING_RTSP_SESSION_ID], start, end - start);
      (data->set.str[STRING_RTSP_SESSION_ID])[end - start] = '\0';
    }
  }
  return CURLE_OK;
}

#endif /* CURL_DISABLE_RTSP */