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osmo-msc/src/libmsc/sdp_msg.c

577 lines
17 KiB

/* Minimalistic SDP parse/compose implementation, focused on GSM audio codecs */
/*
* (C) 2019 by sysmocom - s.m.f.c. GmbH <info@sysmocom.de>
* All Rights Reserved
*
* SPDX-License-Identifier: AGPL-3.0+
*
* Author: Neels Hofmeyr
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <string.h>
#include <errno.h>
#include <osmocom/core/utils.h>
#include <osmocom/core/logging.h>
#include <osmocom/msc/debug.h>
#include <osmocom/msc/sdp_msg.h>
/* Compare name, rate and fmtp, returning typical cmp result: 0 on match, and -1 / 1 on mismatch.
* Do *not* compare the payload_type number.
* The fmtp is only string-compared -- e.g. if AMR parameters appear in a different order, it amounts to a mismatch even
* though all parameters are the same. */
int sdp_audio_codec_cmp(const struct sdp_audio_codec *a, const struct sdp_audio_codec *b)
{
int rc;
if (a == b)
return 0;
if (!a)
return -1;
if (!b)
return 1;
rc = strncmp(a->subtype_name, b->subtype_name, sizeof(a->subtype_name));
if (rc)
return rc;
if (a->rate < b->rate)
return -1;
if (a->rate > b->rate)
return 1;
rc = strncmp(a->fmtp, b->fmtp, sizeof(a->fmtp));
if (rc)
return rc;
return 0;
}
/* Given a predefined fixed payload_type number, add an SDP audio codec entry, if not present yet.
* The payload_type must exist in sdp_msg_payload_type_names.
* Return the audio codec created or already existing for this payload type number.
*/
struct sdp_audio_codec *sdp_audio_codec_add(struct sdp_audio_codecs *ac, unsigned int payload_type,
const char *subtype_name, unsigned int rate, const char *fmtp)
{
struct sdp_audio_codec *codec;
/* Does an entry already exist? */
codec = sdp_audio_codec_by_payload_type(ac, payload_type, false);
if (codec) {
/* Already exists, sanity check */
if (!codec->subtype_name[0])
OSMO_STRLCPY_ARRAY(codec->subtype_name, subtype_name);
else if (strcmp(codec->subtype_name, subtype_name)) {
/* There already is an entry with this payload_type number but a mismatching subtype_name. That is
* weird, rather abort. */
return NULL;
}
if (codec->rate != rate
|| (fmtp && strcmp(fmtp, codec->fmtp))) {
/* Mismatching details. Rather abort */
return NULL;
}
return codec;
}
/* None exists, create codec entry for this payload type number */
codec = sdp_audio_codec_by_payload_type(ac, payload_type, true);
/* NULL means unable to add an entry */
if (!codec)
return NULL;
OSMO_STRLCPY_ARRAY(codec->subtype_name, subtype_name);
if (fmtp)
OSMO_STRLCPY_ARRAY(codec->fmtp, fmtp);
return codec;
}
struct sdp_audio_codec *sdp_audio_codec_add_copy(struct sdp_audio_codecs *ac, const struct sdp_audio_codec *codec)
{
return sdp_audio_codec_add(ac, codec->payload_type, codec->subtype_name, codec->rate,
codec->fmtp[0] ? codec->fmtp : NULL);
}
struct sdp_audio_codec *sdp_audio_codec_by_payload_type(struct sdp_audio_codecs *ac, unsigned int payload_type,
bool create)
{
struct sdp_audio_codec *codec;
foreach_sdp_audio_codec(codec, ac) {
if (codec->payload_type == payload_type)
return codec;
}
if (!create)
return NULL;
/* Not found; codec points after the last entry now. */
if ((codec - ac->codec) >= ARRAY_SIZE(ac->codec))
return NULL;
*codec = (struct sdp_audio_codec){
.payload_type = payload_type,
.rate = 8000,
};
ac->count = (codec - ac->codec) + 1;
return codec;
}
/* Return a given sdp_msg's codec entry that matches the subtype_name, rate and fmtp of the given codec, or NULL if no
* match is found. Comparison is made by sdp_audio_codec_cmp(). */
struct sdp_audio_codec *sdp_audio_codec_by_descr(struct sdp_audio_codecs *ac, const struct sdp_audio_codec *codec)
{
struct sdp_audio_codec *i;
foreach_sdp_audio_codec(i, ac) {
if (!sdp_audio_codec_cmp(i, codec))
return i;
}
return NULL;
}
/* Remove the codec entry pointed at by 'codec'. 'codec' must point at an entry of 'sdp' (to use an external codec
* instance, use sdp_audio_codec_by_descr()).
* Return 0 on success, -ENOENT if codec does not point at the sdp->codec array. */
int sdp_audio_codec_remove(struct sdp_audio_codecs *ac, const struct sdp_audio_codec *codec)
{
struct sdp_audio_codec *i;
if ((codec < ac->codec)
|| ((codec - ac->codec) >= OSMO_MIN(ac->count, ARRAY_SIZE(ac->codec))))
return -ENOENT;
/* Move all following entries one up */
ac->count--;
foreach_sdp_audio_codec(i, ac) {
if (i < codec)
continue;
*i = *(i+1);
}
return 0;
}
/* Convert struct sdp_msg to the actual SDP protocol representation */
int sdp_msg_to_sdp_str_buf(char *dst, size_t dst_size, const struct sdp_msg *sdp)
{
const struct sdp_audio_codec *codec;
struct osmo_strbuf sb = { .buf = dst, .len = dst_size };
const char *ip = sdp->rtp.ip[0] ? sdp->rtp.ip : "0.0.0.0";
char ipv = osmo_ip_str_type(ip) == AF_INET6 ? '6' : '4';
OSMO_STRBUF_PRINTF(sb,
"v=0\r\n"
"o=OsmoMSC 0 0 IN IP%c %s\r\n"
"s=GSM Call\r\n"
"c=IN IP%c %s\r\n"
"t=0 0\r\n"
"m=audio %d RTP/AVP",
ipv, ip, ipv, ip,
sdp->rtp.port);
/* Append all payload type numbers to 'm=audio <port> RTP/AVP 3 4 112' line */
foreach_sdp_audio_codec(codec, &sdp->audio_codecs)
OSMO_STRBUF_PRINTF(sb, " %d", codec->payload_type);
OSMO_STRBUF_PRINTF(sb, "\r\n");
/* Add details for all codecs */
foreach_sdp_audio_codec(codec, &sdp->audio_codecs) {
if (codec->subtype_name[0]) {
OSMO_STRBUF_PRINTF(sb, "a=rtpmap:%d %s/%d\r\n", codec->payload_type, codec->subtype_name,
codec->rate > 0? codec->rate : 8000);
}
if (codec->fmtp[0])
OSMO_STRBUF_PRINTF(sb, "a=fmtp:%d %s\r\n", codec->payload_type, codec->fmtp);
}
OSMO_STRBUF_PRINTF(sb, "a=ptime:%d\r\n", sdp->ptime > 0? sdp->ptime : 20);
return sb.chars_needed;
}
/* Return the first line ending (or the end of the string) at or after the given string position. */
const char *sdp_msg_line_end(const char *src)
{
const char *line_end = strchr(src, '\r');
if (!line_end)
line_end = strchr(src, '\n');
if (!line_end)
line_end = src + strlen(src);
return line_end;
}
/* parse a line like 'a=rtpmap:0 PCMU/8000', 'a=fmtp:112 octet-align=1; mode-set=4', 'a=ptime:20'.
* The src should point at the character after 'a=', e.g. at the start of 'rtpmap', 'fmtp', 'ptime'
*/
int sdp_parse_attrib(struct sdp_msg *sdp, const char *src)
{
unsigned int payload_type;
struct sdp_audio_codec *codec;
#define A_RTPMAP "rtpmap:"
#define A_FMTP "fmtp:"
#define A_PTIME "ptime:"
#define A_RTCP "rtcp:"
#define A_SENDRECV "sendrecv"
#define A_SENDONLY "sendonly"
#define A_RECVONLY "recvonly"
if (osmo_str_startswith(src, A_RTPMAP)) {
char *audio_name;
unsigned int channels = 1;
if (sscanf(src, A_RTPMAP "%u", &payload_type) != 1)
return -EINVAL;
audio_name = strchr(src, ' ');
if (!audio_name || audio_name >= sdp_msg_line_end(src))
return -EINVAL;
codec = sdp_audio_codec_by_payload_type(&sdp->audio_codecs, payload_type, true);
if (!codec)
return -ENOSPC;
if (sscanf(audio_name, " %31[^/]/%u/%u", codec->subtype_name, &codec->rate, &channels) < 1)
return -EINVAL;
if (channels != 1)
return -ENOTSUP;
}
else if (osmo_str_startswith(src, A_FMTP)) {
char *fmtp_str;
const char *line_end = sdp_msg_line_end(src);
if (sscanf(src, A_FMTP "%u", &payload_type) != 1)
return -EINVAL;
fmtp_str = strchr(src, ' ');
if (!fmtp_str)
return -EINVAL;
fmtp_str++;
if (fmtp_str >= line_end)
return -EINVAL;
codec = sdp_audio_codec_by_payload_type(&sdp->audio_codecs, payload_type, true);
if (!codec)
return -ENOSPC;
/* (+1 because osmo_strlcpy() interprets it as size including the '\0') */
osmo_strlcpy(codec->fmtp, fmtp_str, line_end - fmtp_str + 1);
}
else if (osmo_str_startswith(src, A_PTIME)) {
if (sscanf(src, A_PTIME "%u", &sdp->ptime) != 1)
return -EINVAL;
}
else if (osmo_str_startswith(src, A_RTCP)) {
/* TODO? */
}
else if (osmo_str_startswith(src, A_SENDRECV)) {
/* TODO? */
}
else if (osmo_str_startswith(src, A_SENDONLY)) {
/* TODO? */
}
else if (osmo_str_startswith(src, A_RECVONLY)) {
/* TODO? */
}
return 0;
}
const struct value_string sdp_msg_payload_type_names[] = {
{ 0, "PCMU" },
{ 3, "GSM" },
{ 8, "PCMA" },
{ 18, "G729" },
{ 110, "GSM-EFR" },
{ 111, "GSM-HR-08" },
{ 112, "AMR" },
{ 113, "AMR-WB" },
{}
};
/* Return payload type number matching given string ("AMR", "GSM", ...) or negative if not found. */
int sdp_subtype_name_to_payload_type(const char *subtype_name)
{
return get_string_value(sdp_msg_payload_type_names, subtype_name);
}
/* Parse a line like 'm=audio 16398 RTP/AVP 0 3 8 96 112', starting after the '=' */
static int sdp_parse_media_description(struct sdp_msg *sdp, const char *src)
{
unsigned int port;
int i;
const char *payload_type_str;
const char *line_end = sdp_msg_line_end(src);
if (sscanf(src, "audio %u RTP/AVP", &port) < 1)
return -ENOTSUP;
if (port > 0xffff)
return -EINVAL;
sdp->rtp.port = port;
/* skip "audio 12345 RTP/AVP ", i.e. 3 spaces on */
payload_type_str = src;
for (i = 0; i < 3; i++) {
payload_type_str = strchr(payload_type_str, ' ');
if (!payload_type_str)
return -EINVAL;
while (*payload_type_str == ' ')
payload_type_str++;
if (payload_type_str >= line_end)
return -EINVAL;
}
/* Parse listing of payload type numbers after "RTP/AVP" */
while (payload_type_str < line_end) {
unsigned int payload_type;
struct sdp_audio_codec *codec;
const char *subtype_name;
if (sscanf(payload_type_str, "%u", &payload_type) < 1)
return -EINVAL;
codec = sdp_audio_codec_by_payload_type(&sdp->audio_codecs, payload_type, true);
if (!codec)
return -ENOSPC;
/* Fill in subtype name for fixed payload types */
subtype_name = get_value_string_or_null(sdp_msg_payload_type_names, codec->payload_type);
if (subtype_name)
OSMO_STRLCPY_ARRAY(codec->subtype_name, subtype_name);
payload_type_str = strchr(payload_type_str, ' ');
if (!payload_type_str)
payload_type_str = line_end;
while (*payload_type_str == ' ')
payload_type_str++;
}
return 0;
}
/* parse a line like 'c=IN IP4 192.168.11.151' starting after the '=' */
static int sdp_parse_connection_info(struct sdp_msg *sdp, const char *src)
{
char ipv[10];
char addr_str[INET6_ADDRSTRLEN];
if (sscanf(src, "IN %s %s", ipv, addr_str) < 2)
return -EINVAL;
/* supporting only IPv4 */
if (strcmp(ipv, "IP4"))
return -ENOTSUP;
osmo_sockaddr_str_from_str(&sdp->rtp, addr_str, sdp->rtp.port);
return 0;
}
/* Parse SDP string into struct sdp_msg. Return 0 on success, negative on error. */
int sdp_msg_from_sdp_str(struct sdp_msg *sdp, const char *src)
{
const char *pos;
*sdp = (struct sdp_msg){};
for (pos = src; pos && *pos; pos++) {
char attrib;
int rc = 0;
if (*pos == '\r' || *pos == '\n')
continue;
/* Expecting only lines starting with 'X='. Not being too strict about it is probably alright. */
if (pos[1] != '=')
goto next_line;
attrib = *pos;
pos += 2;
switch (attrib) {
/* a=... */
case 'a':
rc = sdp_parse_attrib(sdp, pos);
break;
case 'm':
rc = sdp_parse_media_description(sdp, pos);
break;
case 'c':
rc = sdp_parse_connection_info(sdp, pos);
break;
default:
/* ignore any other parameters */
break;
}
if (rc) {
size_t line_len;
const char *line_end = sdp_msg_line_end(pos);
pos -= 2;
line_len = line_end - pos;
switch (rc) {
case -EINVAL:
LOGP(DMNCC, LOGL_ERROR,
"Failed to parse SDP: invalid line: %s\n", osmo_quote_str(pos, line_len));
break;
case -ENOSPC:
LOGP(DMNCC, LOGL_ERROR,
"Failed to parse SDP: no more space for: %s\n", osmo_quote_str(pos, line_len));
break;
case -ENOTSUP:
LOGP(DMNCC, LOGL_ERROR,
"Failed to parse SDP: not supported: %s\n", osmo_quote_str(pos, line_len));
break;
default:
LOGP(DMNCC, LOGL_ERROR,
"Failed to parse SDP: %s\n", osmo_quote_str(pos, line_len));
break;
}
return rc;
}
next_line:
pos = strstr(pos, "\r\n");
if (!pos)
break;
}
return 0;
}
/* Leave only those codecs in 'ac_dest' that are also present in 'ac_other'.
* The matching is made by sdp_audio_codec_cmp(), i.e. payload_type numbers are not compared and fmtp parameters are
* compared 1:1 as plain strings.
* If translate_payload_type_numbers has an effect if ac_dest and ac_other have mismatching payload_type numbers for the
* same SDP codec descriptions. If translate_payload_type_numbers is true, take the payload_type numbers from ac_other.
* If false, keep payload_type numbers in ac_dest unchanged. */
void sdp_audio_codecs_intersection(struct sdp_audio_codecs *ac_dest, const struct sdp_audio_codecs *ac_other,
bool translate_payload_type_numbers)
{
int i;
for (i = 0; i < ac_dest->count; i++) {
struct sdp_audio_codec *codec = &ac_dest->codec[i];
struct sdp_audio_codec *other;
OSMO_ASSERT(i < ARRAY_SIZE(ac_dest->codec));
other = sdp_audio_codec_by_descr((struct sdp_audio_codecs*)ac_other, codec);
if (!other) {
OSMO_ASSERT(sdp_audio_codec_remove(ac_dest, codec) == 0);
i--;
continue;
}
/* Doing payload_type number translation of part of the intersection because it makes the algorithm
* simpler: we already know ac_dest is a subset of ac_other, and there is no need to resolve payload
* type number conflicts. */
if (translate_payload_type_numbers)
codec->payload_type = other->payload_type;
}
}
/* Make sure the given codec is listed as the first codec. 'codec' must be an actual codec entry of the given audio
* codecs list. */
void sdp_audio_codecs_select(struct sdp_audio_codecs *ac, struct sdp_audio_codec *codec)
{
struct sdp_audio_codec tmp;
struct sdp_audio_codec *pos;
OSMO_ASSERT((codec >= ac->codec)
&& ((codec - ac->codec) < OSMO_MIN(ac->count, ARRAY_SIZE(ac->codec))));
/* Already the first? */
if (codec == ac->codec)
return;
tmp = *codec;
for (pos = codec - 1; pos >= ac->codec; pos--)
pos[1] = pos[0];
ac->codec[0] = tmp;
return;
}
/* Short single-line representation of an SDP audio codec, convenient for logging.
* Like "AMR/8000:octet-align=1#122" */
int sdp_audio_codec_to_str_buf(char *buf, size_t buflen, const struct sdp_audio_codec *codec)
{
struct osmo_strbuf sb = { .buf = buf, .len = buflen };
OSMO_STRBUF_PRINTF(sb, "%s", codec->subtype_name);
if (codec->fmtp[0])
OSMO_STRBUF_PRINTF(sb, ":%s", codec->fmtp);
return sb.chars_needed;
}
char *sdp_audio_codec_to_str_c(void *ctx, const struct sdp_audio_codec *codec)
{
OSMO_NAME_C_IMPL(ctx, 32, "sdp_audio_codec_to_str_c-ERROR", sdp_audio_codec_to_str_buf, codec)
}
const char *sdp_audio_codec_to_str(const struct sdp_audio_codec *codec)
{
return sdp_audio_codec_to_str_c(OTC_SELECT, codec);
}
/* Short single-line representation of a list of SDP audio codecs, convenient for logging */
int sdp_audio_codecs_to_str_buf(char *buf, size_t buflen, const struct sdp_audio_codecs *ac)
{
struct osmo_strbuf sb = { .buf = buf, .len = buflen };
const struct sdp_audio_codec *codec;
if (!ac->count)
OSMO_STRBUF_PRINTF(sb, "(no-codecs)");
foreach_sdp_audio_codec(codec, ac) {
bool first = (codec == ac->codec);
if (!first)
OSMO_STRBUF_PRINTF(sb, ",");
OSMO_STRBUF_APPEND(sb, sdp_audio_codec_to_str_buf, codec);
}
return sb.chars_needed;
}
char *sdp_audio_codecs_to_str_c(void *ctx, const struct sdp_audio_codecs *ac)
{
OSMO_NAME_C_IMPL(ctx, 128, "sdp_audio_codecs_to_str_c-ERROR", sdp_audio_codecs_to_str_buf, ac)
}
const char *sdp_audio_codecs_to_str(const struct sdp_audio_codecs *ac)
{
return sdp_audio_codecs_to_str_c(OTC_SELECT, ac);
}
/* Short single-line representation of an SDP message, convenient for logging */
int sdp_msg_to_str_buf(char *buf, size_t buflen, const struct sdp_msg *sdp)
{
struct osmo_strbuf sb = { .buf = buf, .len = buflen };
if (!sdp) {
OSMO_STRBUF_PRINTF(sb, "NULL");
return sb.chars_needed;
}
OSMO_STRBUF_PRINTF(sb, OSMO_SOCKADDR_STR_FMT, OSMO_SOCKADDR_STR_FMT_ARGS(&sdp->rtp));
OSMO_STRBUF_PRINTF(sb, "{");
OSMO_STRBUF_APPEND(sb, sdp_audio_codecs_to_str_buf, &sdp->audio_codecs);
OSMO_STRBUF_PRINTF(sb, "}");
return sb.chars_needed;
}
char *sdp_msg_to_str_c(void *ctx, const struct sdp_msg *sdp)
{
OSMO_NAME_C_IMPL(ctx, 128, "sdp_msg_to_str_c-ERROR", sdp_msg_to_str_buf, sdp)
}
const char *sdp_msg_to_str(const struct sdp_msg *sdp)
{
return sdp_msg_to_str_c(OTC_SELECT, sdp);
}