libavformat/sapdec.c

   1 /*
   2  * Session Announcement Protocol (RFC 2974) demuxer
   3  * Copyright (c) 2010 Martin Storsjo
   4  *
   5  * This file is part of Libav.
   6  *
   7  * Libav 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  * Libav 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 Libav; 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 #if HAVE_POLL_H
  31 #include <poll.h>
  32 #endif
  33
  34 struct SAPState {
  35     URLContext *ann_fd;
  36     AVFormatContext *sdp_ctx;
  37     AVIOContext sdp_pb;
  38     uint16_t hash;
  39     char *sdp;
  40     int eof;
  41 };
  42
  43 static int sap_probe(AVProbeData *p)
  44 {
  45     if (av_strstart(p->filename, "sap:", NULL))
  46         return AVPROBE_SCORE_MAX;
  47     return 0;
  48 }
  49
  50 static int sap_read_close(AVFormatContext *s)
  51 {
  52     struct SAPState *sap = s->priv_data;
  53     if (sap->sdp_ctx)
  54         avformat_close_input(&sap->sdp_ctx);
  55     if (sap->ann_fd)
  56         ffurl_close(sap->ann_fd);
  57     av_freep(&sap->sdp);
  58     ff_network_close();
  59     return 0;
  60 }
  61
  62 static int sap_read_header(AVFormatContext *s)
  63 {
  64     struct SAPState *sap = s->priv_data;
  65     char host[1024], path[1024], url[1024];
  66     uint8_t recvbuf[1500];
  67     int port;
  68     int ret, i;
  69     AVInputFormat* infmt;
  70
  71     if (!ff_network_init())
  72         return AVERROR(EIO);
  73
  74     av_url_split(NULL, 0, NULL, 0, host, sizeof(host), &port,
  75                  path, sizeof(path), s->filename);
  76     if (port < 0)
  77         port = 9875;
  78
  79     if (!host[0]) {
  80         /* Listen for announcements on sap.mcast.net if no host was specified */
  81         av_strlcpy(host, "224.2.127.254", sizeof(host));
  82     }
  83
  84     ff_url_join(url, sizeof(url), "udp", NULL, host, port, "?localport=%d",
  85                 port);
  86     ret = ffurl_open(&sap->ann_fd, url, AVIO_FLAG_READ,
  87                      &s->interrupt_callback, NULL);
  88     if (ret)
  89         goto fail;
  90
  91     while (1) {
  92         int addr_type, auth_len;
  93         int pos;
  94
  95         ret = ffurl_read(sap->ann_fd, recvbuf, sizeof(recvbuf) - 1);
  96         if (ret == AVERROR(EAGAIN))
  97             continue;
  98         if (ret < 0)
  99             goto fail;
 100         recvbuf[ret] = '\0'; /* Null terminate for easier parsing */
 101         if (ret < 8) {
 102             av_log(s, AV_LOG_WARNING, "Received too short packet\n");
 103             continue;
 104         }
 105
 106         if ((recvbuf[0] & 0xe0) != 0x20) {
 107             av_log(s, AV_LOG_WARNING, "Unsupported SAP version packet "
 108                                       "received\n");
 109             continue;
 110         }
 111
 112         if (recvbuf[0] & 0x04) {
 113             av_log(s, AV_LOG_WARNING, "Received stream deletion "
 114                                       "announcement\n");
 115             continue;
 116         }
 117         addr_type = recvbuf[0] & 0x10;
 118         auth_len  = recvbuf[1];
 119         sap->hash = AV_RB16(&recvbuf[2]);
 120         pos = 4;
 121         if (addr_type)
 122             pos += 16; /* IPv6 */
 123         else
 124             pos += 4; /* IPv4 */
 125         pos += auth_len * 4;
 126         if (pos + 4 >= ret) {
 127             av_log(s, AV_LOG_WARNING, "Received too short packet\n");
 128             continue;
 129         }
 130 #define MIME "application/sdp"
 131         if (strcmp(&recvbuf[pos], MIME) == 0) {
 132             pos += strlen(MIME) + 1;
 133         } else if (strncmp(&recvbuf[pos], "v=0\r\n", 5) == 0) {
 134             // Direct SDP without a mime type
 135         } else {
 136             av_log(s, AV_LOG_WARNING, "Unsupported mime type %s\n",
 137                                       &recvbuf[pos]);
 138             continue;
 139         }
 140
 141         sap->sdp = av_strdup(&recvbuf[pos]);
 142         break;
 143     }
 144
 145     av_log(s, AV_LOG_VERBOSE, "SDP:\n%s\n", sap->sdp);
 146     ffio_init_context(&sap->sdp_pb, sap->sdp, strlen(sap->sdp), 0, NULL, NULL,
 147                   NULL, NULL);
 148
 149     infmt = av_find_input_format("sdp");
 150     if (!infmt)
 151         goto fail;
 152     sap->sdp_ctx = avformat_alloc_context();
 153     if (!sap->sdp_ctx) {
 154         ret = AVERROR(ENOMEM);
 155         goto fail;
 156     }
 157     sap->sdp_ctx->max_delay = s->max_delay;
 158     sap->sdp_ctx->pb        = &sap->sdp_pb;
 159     sap->sdp_ctx->interrupt_callback = s->interrupt_callback;
 160     ret = avformat_open_input(&sap->sdp_ctx, "temp.sdp", infmt, NULL);
 161     if (ret < 0)
 162         goto fail;
 163     if (sap->sdp_ctx->ctx_flags & AVFMTCTX_NOHEADER)
 164         s->ctx_flags |= AVFMTCTX_NOHEADER;
 165     for (i = 0; i < sap->sdp_ctx->nb_streams; i++) {
 166         AVStream *st = avformat_new_stream(s, NULL);
 167         if (!st) {
 168             ret = AVERROR(ENOMEM);
 169             goto fail;
 170         }
 171         st->id = i;
 172         avcodec_copy_context(st->codec, sap->sdp_ctx->streams[i]->codec);
 173         st->time_base = sap->sdp_ctx->streams[i]->time_base;
 174     }
 175
 176     return 0;
 177
 178 fail:
 179     sap_read_close(s);
 180     return ret;
 181 }
 182
 183 static int sap_fetch_packet(AVFormatContext *s, AVPacket *pkt)
 184 {
 185     struct SAPState *sap = s->priv_data;
 186     int fd = ffurl_get_file_handle(sap->ann_fd);
 187     int n, ret;
 188     struct pollfd p = {fd, POLLIN, 0};
 189     uint8_t recvbuf[1500];
 190
 191     if (sap->eof)
 192         return AVERROR_EOF;
 193
 194     while (1) {
 195         n = poll(&p, 1, 0);
 196         if (n <= 0 || !(p.revents & POLLIN))
 197             break;
 198         ret = ffurl_read(sap->ann_fd, recvbuf, sizeof(recvbuf));
 199         if (ret >= 8) {
 200             uint16_t hash = AV_RB16(&recvbuf[2]);
 201             /* Should ideally check the source IP address, too */
 202             if (recvbuf[0] & 0x04 && hash == sap->hash) {
 203                 /* Stream deletion */
 204                 sap->eof = 1;
 205                 return AVERROR_EOF;
 206             }
 207         }
 208     }
 209     ret = av_read_frame(sap->sdp_ctx, pkt);
 210     if (ret < 0)
 211         return ret;
 212     if (s->ctx_flags & AVFMTCTX_NOHEADER) {
 213         while (sap->sdp_ctx->nb_streams > s->nb_streams) {
 214             int i = s->nb_streams;
 215             AVStream *st = avformat_new_stream(s, NULL);
 216             if (!st) {
 217                 av_free_packet(pkt);
 218                 return AVERROR(ENOMEM);
 219             }
 220             st->id = i;
 221             avcodec_copy_context(st->codec, sap->sdp_ctx->streams[i]->codec);
 222             st->time_base = sap->sdp_ctx->streams[i]->time_base;
 223         }
 224     }
 225     return ret;
 226 }
 227
 228 AVInputFormat ff_sap_demuxer = {
 229     .name           = "sap",
 230     .long_name      = NULL_IF_CONFIG_SMALL("SAP input"),
 231     .priv_data_size = sizeof(struct SAPState),
 232     .read_probe     = sap_probe,
 233     .read_header    = sap_read_header,
 234     .read_packet    = sap_fetch_packet,
 235     .read_close     = sap_read_close,
 236     .flags          = AVFMT_NOFILE,
 237 };