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sapdec.c
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1 /*
2  * Session Announcement Protocol (RFC 2974) demuxer
3  * Copyright (c) 2010 Martin Storsjo
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #include "avformat.h"
23 #include "libavutil/avstring.h"
24 #include "libavutil/intreadwrite.h"
25 #include "network.h"
26 #include "os_support.h"
27 #include "internal.h"
28 #include "avio_internal.h"
29 #include "url.h"
30 #include "rtpdec.h"
31 #if HAVE_POLL_H
32 #include <poll.h>
33 #endif
34 
35 struct SAPState {
39  uint16_t hash;
40  char *sdp;
41  int eof;
42 };
43 
44 static int sap_probe(AVProbeData *p)
45 {
46  if (av_strstart(p->filename, "sap:", NULL))
47  return AVPROBE_SCORE_MAX;
48  return 0;
49 }
50 
52 {
53  struct SAPState *sap = s->priv_data;
54  if (sap->sdp_ctx)
56  if (sap->ann_fd)
57  ffurl_close(sap->ann_fd);
58  av_freep(&sap->sdp);
60  return 0;
61 }
62 
64 {
65  struct SAPState *sap = s->priv_data;
66  char host[1024], path[1024], url[1024];
68  int port;
69  int ret, i;
70  AVInputFormat* infmt;
71 
72  if (!ff_network_init())
73  return AVERROR(EIO);
74 
75  av_url_split(NULL, 0, NULL, 0, host, sizeof(host), &port,
76  path, sizeof(path), s->filename);
77  if (port < 0)
78  port = 9875;
79 
80  if (!host[0]) {
81  /* Listen for announcements on sap.mcast.net if no host was specified */
82  av_strlcpy(host, "224.2.127.254", sizeof(host));
83  }
84 
85  ff_url_join(url, sizeof(url), "udp", NULL, host, port, "?localport=%d",
86  port);
87  ret = ffurl_open(&sap->ann_fd, url, AVIO_FLAG_READ,
88  &s->interrupt_callback, NULL);
89  if (ret)
90  goto fail;
91 
92  while (1) {
93  int addr_type, auth_len;
94  int pos;
95 
96  ret = ffurl_read(sap->ann_fd, recvbuf, sizeof(recvbuf) - 1);
97  if (ret == AVERROR(EAGAIN))
98  continue;
99  if (ret < 0)
100  goto fail;
101  recvbuf[ret] = '\0'; /* Null terminate for easier parsing */
102  if (ret < 8) {
103  av_log(s, AV_LOG_WARNING, "Received too short packet\n");
104  continue;
105  }
106 
107  if ((recvbuf[0] & 0xe0) != 0x20) {
108  av_log(s, AV_LOG_WARNING, "Unsupported SAP version packet "
109  "received\n");
110  continue;
111  }
112 
113  if (recvbuf[0] & 0x04) {
114  av_log(s, AV_LOG_WARNING, "Received stream deletion "
115  "announcement\n");
116  continue;
117  }
118  addr_type = recvbuf[0] & 0x10;
119  auth_len = recvbuf[1];
120  sap->hash = AV_RB16(&recvbuf[2]);
121  pos = 4;
122  if (addr_type)
123  pos += 16; /* IPv6 */
124  else
125  pos += 4; /* IPv4 */
126  pos += auth_len * 4;
127  if (pos + 4 >= ret) {
128  av_log(s, AV_LOG_WARNING, "Received too short packet\n");
129  continue;
130  }
131 #define MIME "application/sdp"
132  if (strcmp(&recvbuf[pos], MIME) == 0) {
133  pos += strlen(MIME) + 1;
134  } else if (strncmp(&recvbuf[pos], "v=0\r\n", 5) == 0) {
135  // Direct SDP without a mime type
136  } else {
137  av_log(s, AV_LOG_WARNING, "Unsupported mime type %s\n",
138  &recvbuf[pos]);
139  continue;
140  }
141 
142  sap->sdp = av_strdup(&recvbuf[pos]);
143  break;
144  }
145 
146  av_log(s, AV_LOG_VERBOSE, "SDP:\n%s\n", sap->sdp);
147  ffio_init_context(&sap->sdp_pb, sap->sdp, strlen(sap->sdp), 0, NULL, NULL,
148  NULL, NULL);
149 
150  infmt = av_find_input_format("sdp");
151  if (!infmt)
152  goto fail;
154  if (!sap->sdp_ctx) {
155  ret = AVERROR(ENOMEM);
156  goto fail;
157  }
158  sap->sdp_ctx->max_delay = s->max_delay;
159  sap->sdp_ctx->pb = &sap->sdp_pb;
161  ret = avformat_open_input(&sap->sdp_ctx, "temp.sdp", infmt, NULL);
162  if (ret < 0)
163  goto fail;
164  if (sap->sdp_ctx->ctx_flags & AVFMTCTX_NOHEADER)
166  for (i = 0; i < sap->sdp_ctx->nb_streams; i++) {
167  AVStream *st = avformat_new_stream(s, NULL);
168  if (!st) {
169  ret = AVERROR(ENOMEM);
170  goto fail;
171  }
172  st->id = i;
174  st->time_base = sap->sdp_ctx->streams[i]->time_base;
175  }
176 
177  return 0;
178 
179 fail:
180  sap_read_close(s);
181  return ret;
182 }
183 
185 {
186  struct SAPState *sap = s->priv_data;
187  int fd = ffurl_get_file_handle(sap->ann_fd);
188  int n, ret;
189  struct pollfd p = {fd, POLLIN, 0};
191 
192  if (sap->eof)
193  return AVERROR_EOF;
194 
195  while (1) {
196  n = poll(&p, 1, 0);
197  if (n <= 0 || !(p.revents & POLLIN))
198  break;
199  ret = ffurl_read(sap->ann_fd, recvbuf, sizeof(recvbuf));
200  if (ret >= 8) {
201  uint16_t hash = AV_RB16(&recvbuf[2]);
202  /* Should ideally check the source IP address, too */
203  if (recvbuf[0] & 0x04 && hash == sap->hash) {
204  /* Stream deletion */
205  sap->eof = 1;
206  return AVERROR_EOF;
207  }
208  }
209  }
210  ret = av_read_frame(sap->sdp_ctx, pkt);
211  if (ret < 0)
212  return ret;
213  if (s->ctx_flags & AVFMTCTX_NOHEADER) {
214  while (sap->sdp_ctx->nb_streams > s->nb_streams) {
215  int i = s->nb_streams;
216  AVStream *st = avformat_new_stream(s, NULL);
217  if (!st) {
218  av_free_packet(pkt);
219  return AVERROR(ENOMEM);
220  }
221  st->id = i;
223  st->time_base = sap->sdp_ctx->streams[i]->time_base;
224  }
225  }
226  return ret;
227 }
228 
230  .name = "sap",
231  .long_name = NULL_IF_CONFIG_SMALL("SAP input"),
232  .priv_data_size = sizeof(struct SAPState),
233  .read_probe = sap_probe,
234  .read_header = sap_read_header,
235  .read_packet = sap_fetch_packet,
236  .read_close = sap_read_close,
237  .flags = AVFMT_NOFILE,
238 };