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
35struct SAPState {
36    URLContext *ann_fd;
37    AVFormatContext *sdp_ctx;
38    AVIOContext sdp_pb;
39    uint16_t hash;
40    char *sdp;
41    int eof;
42};
43
44static int sap_probe(AVProbeData *p)
45{
46    if (av_strstart(p->filename, "sap:", NULL))
47        return AVPROBE_SCORE_MAX;
48    return 0;
49}
50
51static int sap_read_close(AVFormatContext *s)
52{
53    struct SAPState *sap = s->priv_data;
54    if (sap->sdp_ctx)
55        avformat_close_input(&sap->sdp_ctx);
56    if (sap->ann_fd)
57        ffurl_close(sap->ann_fd);
58    av_freep(&sap->sdp);
59    ff_network_close();
60    return 0;
61}
62
63static int sap_read_header(AVFormatContext *s)
64{
65    struct SAPState *sap = s->priv_data;
66    char host[1024], path[1024], url[1024];
67    uint8_t recvbuf[RTP_MAX_PACKET_LENGTH];
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;
153    sap->sdp_ctx = avformat_alloc_context();
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;
160    sap->sdp_ctx->interrupt_callback = s->interrupt_callback;
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)
165        s->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;
173        avcodec_copy_context(st->codec, sap->sdp_ctx->streams[i]->codec);
174        st->time_base = sap->sdp_ctx->streams[i]->time_base;
175    }
176
177    return 0;
178
179fail:
180    sap_read_close(s);
181    return ret;
182}
183
184static int sap_fetch_packet(AVFormatContext *s, AVPacket *pkt)
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};
190    uint8_t recvbuf[RTP_MAX_PACKET_LENGTH];
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;
222            avcodec_copy_context(st->codec, sap->sdp_ctx->streams[i]->codec);
223            st->time_base = sap->sdp_ctx->streams[i]->time_base;
224        }
225    }
226    return ret;
227}
228
229AVInputFormat ff_sap_demuxer = {
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};
239