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#include <sys/time.h>
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                           AVFormatParameters *ap)
65{
66    struct SAPState *sap = s->priv_data;
67    char host[1024], path[1024], url[1024];
68    uint8_t recvbuf[1500];
69    int port;
70    int ret, i;
71    AVInputFormat* infmt;
72
73    if (!ff_network_init())
74        return AVERROR(EIO);
75
76    av_url_split(NULL, 0, NULL, 0, host, sizeof(host), &port,
77                 path, sizeof(path), s->filename);
78    if (port < 0)
79        port = 9875;
80
81    if (!host[0]) {
82        /* Listen for announcements on sap.mcast.net if no host was specified */
83        av_strlcpy(host, "224.2.127.254", sizeof(host));
84    }
85
86    ff_url_join(url, sizeof(url), "udp", NULL, host, port, "?localport=%d",
87                port);
88    ret = ffurl_open(&sap->ann_fd, url, AVIO_FLAG_READ,
89                     &s->interrupt_callback, NULL);
90    if (ret)
91        goto fail;
92
93    while (1) {
94        int addr_type, auth_len;
95        int pos;
96
97        ret = ffurl_read(sap->ann_fd, recvbuf, sizeof(recvbuf) - 1);
98        if (ret == AVERROR(EAGAIN))
99            continue;
100        if (ret < 0)
101            goto fail;
102        recvbuf[ret] = '\0'; /* Null terminate for easier parsing */
103        if (ret < 8) {
104            av_log(s, AV_LOG_WARNING, "Received too short packet\n");
105            continue;
106        }
107
108        if ((recvbuf[0] & 0xe0) != 0x20) {
109            av_log(s, AV_LOG_WARNING, "Unsupported SAP version packet "
110                                      "received\n");
111            continue;
112        }
113
114        if (recvbuf[0] & 0x04) {
115            av_log(s, AV_LOG_WARNING, "Received stream deletion "
116                                      "announcement\n");
117            continue;
118        }
119        addr_type = recvbuf[0] & 0x10;
120        auth_len  = recvbuf[1];
121        sap->hash = AV_RB16(&recvbuf[2]);
122        pos = 4;
123        if (addr_type)
124            pos += 16; /* IPv6 */
125        else
126            pos += 4; /* IPv4 */
127        pos += auth_len * 4;
128        if (pos + 4 >= ret) {
129            av_log(s, AV_LOG_WARNING, "Received too short packet\n");
130            continue;
131        }
132#define MIME "application/sdp"
133        if (strcmp(&recvbuf[pos], MIME) == 0) {
134            pos += strlen(MIME) + 1;
135        } else if (strncmp(&recvbuf[pos], "v=0\r\n", 5) == 0) {
136            // Direct SDP without a mime type
137        } else {
138            av_log(s, AV_LOG_WARNING, "Unsupported mime type %s\n",
139                                      &recvbuf[pos]);
140            continue;
141        }
142
143        sap->sdp = av_strdup(&recvbuf[pos]);
144        break;
145    }
146
147    av_log(s, AV_LOG_VERBOSE, "SDP:\n%s\n", sap->sdp);
148    ffio_init_context(&sap->sdp_pb, sap->sdp, strlen(sap->sdp), 0, NULL, NULL,
149                  NULL, NULL);
150
151    infmt = av_find_input_format("sdp");
152    if (!infmt)
153        goto fail;
154    sap->sdp_ctx = avformat_alloc_context();
155    if (!sap->sdp_ctx) {
156        ret = AVERROR(ENOMEM);
157        goto fail;
158    }
159    sap->sdp_ctx->max_delay = s->max_delay;
160    sap->sdp_ctx->pb        = &sap->sdp_pb;
161    sap->sdp_ctx->interrupt_callback = s->interrupt_callback;
162    ret = avformat_open_input(&sap->sdp_ctx, "temp.sdp", infmt, NULL);
163    if (ret < 0)
164        goto fail;
165    if (sap->sdp_ctx->ctx_flags & AVFMTCTX_NOHEADER)
166        s->ctx_flags |= AVFMTCTX_NOHEADER;
167    for (i = 0; i < sap->sdp_ctx->nb_streams; i++) {
168        AVStream *st = avformat_new_stream(s, NULL);
169        if (!st) {
170            ret = AVERROR(ENOMEM);
171            goto fail;
172        }
173        st->id = i;
174        avcodec_copy_context(st->codec, sap->sdp_ctx->streams[i]->codec);
175        st->time_base = sap->sdp_ctx->streams[i]->time_base;
176    }
177
178    return 0;
179
180fail:
181    sap_read_close(s);
182    return ret;
183}
184
185static int sap_fetch_packet(AVFormatContext *s, AVPacket *pkt)
186{
187    struct SAPState *sap = s->priv_data;
188    int fd = ffurl_get_file_handle(sap->ann_fd);
189    int n, ret;
190    struct pollfd p = {fd, POLLIN, 0};
191    uint8_t recvbuf[1500];
192
193    if (sap->eof)
194        return AVERROR_EOF;
195
196    while (1) {
197        n = poll(&p, 1, 0);
198        if (n <= 0 || !(p.revents & POLLIN))
199            break;
200        ret = ffurl_read(sap->ann_fd, recvbuf, sizeof(recvbuf));
201        if (ret >= 8) {
202            uint16_t hash = AV_RB16(&recvbuf[2]);
203            /* Should ideally check the source IP address, too */
204            if (recvbuf[0] & 0x04 && hash == sap->hash) {
205                /* Stream deletion */
206                sap->eof = 1;
207                return AVERROR_EOF;
208            }
209        }
210    }
211    ret = av_read_frame(sap->sdp_ctx, pkt);
212    if (ret < 0)
213        return ret;
214    if (s->ctx_flags & AVFMTCTX_NOHEADER) {
215        while (sap->sdp_ctx->nb_streams > s->nb_streams) {
216            int i = s->nb_streams;
217            AVStream *st = avformat_new_stream(s, NULL);
218            if (!st) {
219                av_free_packet(pkt);
220                return AVERROR(ENOMEM);
221            }
222            st->id = i;
223            avcodec_copy_context(st->codec, sap->sdp_ctx->streams[i]->codec);
224            st->time_base = sap->sdp_ctx->streams[i]->time_base;
225        }
226    }
227    return ret;
228}
229
230AVInputFormat ff_sap_demuxer = {
231    .name           = "sap",
232    .long_name      = NULL_IF_CONFIG_SMALL("SAP input format"),
233    .priv_data_size = sizeof(struct SAPState),
234    .read_probe     = sap_probe,
235    .read_header    = sap_read_header,
236    .read_packet    = sap_fetch_packet,
237    .read_close     = sap_read_close,
238    .flags = AVFMT_NOFILE,
239};
240
241