libavformat/sapdec.c
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00001 /*
00002  * Session Announcement Protocol (RFC 2974) demuxer
00003  * Copyright (c) 2010 Martin Storsjo
00004  *
00005  * This file is part of Libav.
00006  *
00007  * Libav is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * Libav is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with Libav; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00022 #include "avformat.h"
00023 #include "libavutil/avstring.h"
00024 #include "libavutil/intreadwrite.h"
00025 #include "network.h"
00026 #include "os_support.h"
00027 #include "internal.h"
00028 #include "avio_internal.h"
00029 #include "url.h"
00030 #if HAVE_POLL_H
00031 #include <poll.h>
00032 #endif
00033 #include <sys/time.h>
00034 
00035 struct SAPState {
00036     URLContext *ann_fd;
00037     AVFormatContext *sdp_ctx;
00038     AVIOContext sdp_pb;
00039     uint16_t hash;
00040     char *sdp;
00041     int eof;
00042 };
00043 
00044 static int sap_probe(AVProbeData *p)
00045 {
00046     if (av_strstart(p->filename, "sap:", NULL))
00047         return AVPROBE_SCORE_MAX;
00048     return 0;
00049 }
00050 
00051 static int sap_read_close(AVFormatContext *s)
00052 {
00053     struct SAPState *sap = s->priv_data;
00054     if (sap->sdp_ctx)
00055         avformat_close_input(&sap->sdp_ctx);
00056     if (sap->ann_fd)
00057         ffurl_close(sap->ann_fd);
00058     av_freep(&sap->sdp);
00059     ff_network_close();
00060     return 0;
00061 }
00062 
00063 static int sap_read_header(AVFormatContext *s,
00064                            AVFormatParameters *ap)
00065 {
00066     struct SAPState *sap = s->priv_data;
00067     char host[1024], path[1024], url[1024];
00068     uint8_t recvbuf[1500];
00069     int port;
00070     int ret, i;
00071     AVInputFormat* infmt;
00072 
00073     if (!ff_network_init())
00074         return AVERROR(EIO);
00075 
00076     av_url_split(NULL, 0, NULL, 0, host, sizeof(host), &port,
00077                  path, sizeof(path), s->filename);
00078     if (port < 0)
00079         port = 9875;
00080 
00081     if (!host[0]) {
00082         /* Listen for announcements on sap.mcast.net if no host was specified */
00083         av_strlcpy(host, "224.2.127.254", sizeof(host));
00084     }
00085 
00086     ff_url_join(url, sizeof(url), "udp", NULL, host, port, "?localport=%d",
00087                 port);
00088     ret = ffurl_open(&sap->ann_fd, url, AVIO_FLAG_READ,
00089                      &s->interrupt_callback, NULL);
00090     if (ret)
00091         goto fail;
00092 
00093     while (1) {
00094         int addr_type, auth_len;
00095         int pos;
00096 
00097         ret = ffurl_read(sap->ann_fd, recvbuf, sizeof(recvbuf) - 1);
00098         if (ret == AVERROR(EAGAIN))
00099             continue;
00100         if (ret < 0)
00101             goto fail;
00102         recvbuf[ret] = '\0'; /* Null terminate for easier parsing */
00103         if (ret < 8) {
00104             av_log(s, AV_LOG_WARNING, "Received too short packet\n");
00105             continue;
00106         }
00107 
00108         if ((recvbuf[0] & 0xe0) != 0x20) {
00109             av_log(s, AV_LOG_WARNING, "Unsupported SAP version packet "
00110                                       "received\n");
00111             continue;
00112         }
00113 
00114         if (recvbuf[0] & 0x04) {
00115             av_log(s, AV_LOG_WARNING, "Received stream deletion "
00116                                       "announcement\n");
00117             continue;
00118         }
00119         addr_type = recvbuf[0] & 0x10;
00120         auth_len  = recvbuf[1];
00121         sap->hash = AV_RB16(&recvbuf[2]);
00122         pos = 4;
00123         if (addr_type)
00124             pos += 16; /* IPv6 */
00125         else
00126             pos += 4; /* IPv4 */
00127         pos += auth_len * 4;
00128         if (pos + 4 >= ret) {
00129             av_log(s, AV_LOG_WARNING, "Received too short packet\n");
00130             continue;
00131         }
00132 #define MIME "application/sdp"
00133         if (strcmp(&recvbuf[pos], MIME) == 0) {
00134             pos += strlen(MIME) + 1;
00135         } else if (strncmp(&recvbuf[pos], "v=0\r\n", 5) == 0) {
00136             // Direct SDP without a mime type
00137         } else {
00138             av_log(s, AV_LOG_WARNING, "Unsupported mime type %s\n",
00139                                       &recvbuf[pos]);
00140             continue;
00141         }
00142 
00143         sap->sdp = av_strdup(&recvbuf[pos]);
00144         break;
00145     }
00146 
00147     av_log(s, AV_LOG_VERBOSE, "SDP:\n%s\n", sap->sdp);
00148     ffio_init_context(&sap->sdp_pb, sap->sdp, strlen(sap->sdp), 0, NULL, NULL,
00149                   NULL, NULL);
00150 
00151     infmt = av_find_input_format("sdp");
00152     if (!infmt)
00153         goto fail;
00154     sap->sdp_ctx = avformat_alloc_context();
00155     if (!sap->sdp_ctx) {
00156         ret = AVERROR(ENOMEM);
00157         goto fail;
00158     }
00159     sap->sdp_ctx->max_delay = s->max_delay;
00160     sap->sdp_ctx->pb        = &sap->sdp_pb;
00161     sap->sdp_ctx->interrupt_callback = s->interrupt_callback;
00162     ret = avformat_open_input(&sap->sdp_ctx, "temp.sdp", infmt, NULL);
00163     if (ret < 0)
00164         goto fail;
00165     if (sap->sdp_ctx->ctx_flags & AVFMTCTX_NOHEADER)
00166         s->ctx_flags |= AVFMTCTX_NOHEADER;
00167     for (i = 0; i < sap->sdp_ctx->nb_streams; i++) {
00168         AVStream *st = avformat_new_stream(s, NULL);
00169         if (!st) {
00170             ret = AVERROR(ENOMEM);
00171             goto fail;
00172         }
00173         st->id = i;
00174         avcodec_copy_context(st->codec, sap->sdp_ctx->streams[i]->codec);
00175         st->time_base = sap->sdp_ctx->streams[i]->time_base;
00176     }
00177 
00178     return 0;
00179 
00180 fail:
00181     sap_read_close(s);
00182     return ret;
00183 }
00184 
00185 static int sap_fetch_packet(AVFormatContext *s, AVPacket *pkt)
00186 {
00187     struct SAPState *sap = s->priv_data;
00188     int fd = ffurl_get_file_handle(sap->ann_fd);
00189     int n, ret;
00190     struct pollfd p = {fd, POLLIN, 0};
00191     uint8_t recvbuf[1500];
00192 
00193     if (sap->eof)
00194         return AVERROR_EOF;
00195 
00196     while (1) {
00197         n = poll(&p, 1, 0);
00198         if (n <= 0 || !(p.revents & POLLIN))
00199             break;
00200         ret = ffurl_read(sap->ann_fd, recvbuf, sizeof(recvbuf));
00201         if (ret >= 8) {
00202             uint16_t hash = AV_RB16(&recvbuf[2]);
00203             /* Should ideally check the source IP address, too */
00204             if (recvbuf[0] & 0x04 && hash == sap->hash) {
00205                 /* Stream deletion */
00206                 sap->eof = 1;
00207                 return AVERROR_EOF;
00208             }
00209         }
00210     }
00211     ret = av_read_frame(sap->sdp_ctx, pkt);
00212     if (ret < 0)
00213         return ret;
00214     if (s->ctx_flags & AVFMTCTX_NOHEADER) {
00215         while (sap->sdp_ctx->nb_streams > s->nb_streams) {
00216             int i = s->nb_streams;
00217             AVStream *st = avformat_new_stream(s, NULL);
00218             if (!st) {
00219                 av_free_packet(pkt);
00220                 return AVERROR(ENOMEM);
00221             }
00222             st->id = i;
00223             avcodec_copy_context(st->codec, sap->sdp_ctx->streams[i]->codec);
00224             st->time_base = sap->sdp_ctx->streams[i]->time_base;
00225         }
00226     }
00227     return ret;
00228 }
00229 
00230 AVInputFormat ff_sap_demuxer = {
00231     .name           = "sap",
00232     .long_name      = NULL_IF_CONFIG_SMALL("SAP input format"),
00233     .priv_data_size = sizeof(struct SAPState),
00234     .read_probe     = sap_probe,
00235     .read_header    = sap_read_header,
00236     .read_packet    = sap_fetch_packet,
00237     .read_close     = sap_read_close,
00238     .flags = AVFMT_NOFILE,
00239 };
00240