diff options
author | Neels Hofmeyr <neels@hofmeyr.de> | 2019-10-21 03:24:04 +0200 |
---|---|---|
committer | Neels Hofmeyr <neels@hofmeyr.de> | 2019-11-28 02:52:55 +0100 |
commit | eef45781024d6e17c7b473d15ec5d3d83515d0e2 (patch) | |
tree | 1dc6441b7789da0a8821cbaf75ed8d3b7149aa6d /src | |
parent | bde605dfc574726f2e776c8230e47a5b25e63866 (diff) |
add sdp_msg API: SDP parsing/composition
Rationale: in order to add full SDP to the MNCC protocol (upcoming patch
I8c3b2de53ffae4ec3a66b9dabf308c290a2c999f), we need to parse and compose SDP
messages. Obviously, libosmo-mgcp-client already contains similar code, but
that is unfortunately heavily glued to the actual MGCP implementation. The
simplest solution is to create this separate implementation, copy-pasting from
the existing libosmo-mgcp-client code as is convenient.
This API is added here to probe whether it works well. When it does, the
intention is to "move it up" to osmo-mgw and overhaul the SDP parsing in our
MGCP client and MGCP server APIs using this same API.
Change-Id: If3ce23cd5bab15e2ab4c52ef3e4c75979dffe931
Diffstat (limited to 'src')
-rw-r--r-- | src/libmsc/Makefile.am | 1 | ||||
-rw-r--r-- | src/libmsc/sdp_msg.c | 576 |
2 files changed, 577 insertions, 0 deletions
diff --git a/src/libmsc/Makefile.am b/src/libmsc/Makefile.am index d83489680..e6a2dc164 100644 --- a/src/libmsc/Makefile.am +++ b/src/libmsc/Makefile.am @@ -64,6 +64,7 @@ libmsc_a_SOURCES = \ ran_peer.c \ rrlp.c \ rtp_stream.c \ + sdp_msg.c \ silent_call.c \ sms_queue.c \ transaction.c \ diff --git a/src/libmsc/sdp_msg.c b/src/libmsc/sdp_msg.c new file mode 100644 index 000000000..7880978a0 --- /dev/null +++ b/src/libmsc/sdp_msg.c @@ -0,0 +1,576 @@ +/* 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_str(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"; + + OSMO_STRBUF_PRINTF(sb, + "v=0\r\n" + "o=OsmoMSC 0 0 IN IP4 %s\r\n" + "s=GSM Call\r\n" + "c=IN IP4 %s\r\n" + "t=0 0\r\n" + "m=audio %d RTP/AVP", + ip, 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 < 0 || 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_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_name_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_name_c(void *ctx, const struct sdp_audio_codec *codec) +{ + OSMO_NAME_C_IMPL(ctx, 32, "sdp_audio_codec_name_c-ERROR", sdp_audio_codec_name_buf, codec) +} + +const char *sdp_audio_codec_name(const struct sdp_audio_codec *codec) +{ + return sdp_audio_codec_name_c(OTC_SELECT, codec); +} + +/* Short single-line representation of a list of SDP audio codecs, convenient for logging */ +int sdp_audio_codecs_name_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_name_buf, codec); + } + return sb.chars_needed; +} + +char *sdp_audio_codecs_name_c(void *ctx, const struct sdp_audio_codecs *ac) +{ + OSMO_NAME_C_IMPL(ctx, 128, "sdp_audio_codecs_name_c-ERROR", sdp_audio_codecs_name_buf, ac) +} + +const char *sdp_audio_codecs_name(const struct sdp_audio_codecs *ac) +{ + return sdp_audio_codecs_name_c(OTC_SELECT, ac); +} + +/* Short single-line representation of an SDP message, convenient for logging */ +int sdp_msg_name_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_name_buf, &sdp->audio_codecs); + OSMO_STRBUF_PRINTF(sb, "}"); + return sb.chars_needed; +} + +char *sdp_msg_name_c(void *ctx, const struct sdp_msg *sdp) +{ + OSMO_NAME_C_IMPL(ctx, 128, "sdp_msg_name_c-ERROR", sdp_msg_name_buf, sdp) +} + +const char *sdp_msg_name(const struct sdp_msg *sdp) +{ + return sdp_msg_name_c(OTC_SELECT, sdp); +} |