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webrtc / src / refs/heads/lkgr / . / pc / webrtc_sdp.cc
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/*
* Copyright 2011 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "pc/webrtc_sdp.h"
#include <ctype.h>
#include <limits.h>
#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <map>
#include <memory>
#include <optional>
#include <set>
#include <string>
#include <type_traits>
#include <unordered_map>
#include <utility>
#include <vector>
#include "absl/algorithm/container.h"
#include "absl/strings/ascii.h"
#include "absl/strings/match.h"
#include "absl/strings/string_view.h"
#include "api/candidate.h"
#include "api/jsep_ice_candidate.h"
#include "api/jsep_session_description.h"
#include "api/media_types.h"
#include "api/rtc_error.h"
#include "api/rtp_parameters.h"
#include "api/rtp_transceiver_direction.h"
#include "media/base/codec.h"
#include "media/base/media_constants.h"
#include "media/base/rid_description.h"
#include "media/base/rtp_utils.h"
#include "media/base/stream_params.h"
#include "media/sctp/sctp_transport_internal.h"
#include "p2p/base/candidate_pair_interface.h"
#include "p2p/base/ice_transport_internal.h"
#include "p2p/base/p2p_constants.h"
#include "p2p/base/port.h"
#include "p2p/base/port_interface.h"
#include "p2p/base/transport_description.h"
#include "p2p/base/transport_info.h"
#include "pc/media_protocol_names.h"
#include "pc/media_session.h"
#include "pc/session_description.h"
#include "pc/simulcast_description.h"
#include "pc/simulcast_sdp_serializer.h"
#include "rtc_base/arraysize.h"
#include "rtc_base/checks.h"
#include "rtc_base/crypto_random.h"
#include "rtc_base/ip_address.h"
#include "rtc_base/logging.h"
#include "rtc_base/net_helper.h"
#include "rtc_base/network_constants.h"
#include "rtc_base/socket_address.h"
#include "rtc_base/ssl_fingerprint.h"
#include "rtc_base/string_encode.h"
#include "rtc_base/string_utils.h"
#include "rtc_base/strings/string_builder.h"
using cricket::AudioContentDescription;
using cricket::Candidate;
using cricket::Candidates;
using cricket::ContentInfo;
using cricket::ICE_CANDIDATE_COMPONENT_RTCP;
using cricket::ICE_CANDIDATE_COMPONENT_RTP;
using cricket::kApplicationSpecificBandwidth;
using cricket::kCodecParamMaxPTime;
using cricket::kCodecParamMinPTime;
using cricket::kCodecParamPTime;
using cricket::kTransportSpecificBandwidth;
using cricket::MediaContentDescription;
using cricket::MediaProtocolType;
using cricket::MediaType;
using cricket::RidDescription;
using cricket::RtpHeaderExtensions;
using cricket::SctpDataContentDescription;
using cricket::SimulcastDescription;
using cricket::SimulcastLayer;
using cricket::SimulcastLayerList;
using cricket::SsrcGroup;
using cricket::StreamParams;
using cricket::StreamParamsVec;
using cricket::TransportDescription;
using cricket::TransportInfo;
using cricket::UnsupportedContentDescription;
using cricket::VideoContentDescription;
using rtc::SocketAddress;
// TODO(deadbeef): Switch to using anonymous namespace rather than declaring
// everything "static".
namespace webrtc {
// Line type
// RFC 4566
// An SDP session description consists of a number of lines of text of
// the form:
// <type>=<value>
// where <type> MUST be exactly one case-significant character.
// Check if passed character is a "token-char" from RFC 4566.
// https://datatracker.ietf.org/doc/html/rfc4566#section-9
// token-char = %x21 / %x23-27 / %x2A-2B / %x2D-2E / %x30-39
// / %x41-5A / %x5E-7E
bool IsTokenChar(char ch) {
return ch == 0x21 || (ch >= 0x23 && ch <= 0x27) || ch == 0x2a || ch == 0x2b ||
ch == 0x2d || ch == 0x2e || (ch >= 0x30 && ch <= 0x39) ||
(ch >= 0x41 && ch <= 0x5a) || (ch >= 0x5e && ch <= 0x7e);
}
static const int kLinePrefixLength = 2; // Length of <type>=
static const char kLineTypeVersion = 'v';
static const char kLineTypeOrigin = 'o';
static const char kLineTypeSessionName = 's';
static const char kLineTypeSessionInfo = 'i';
static const char kLineTypeSessionUri = 'u';
static const char kLineTypeSessionEmail = 'e';
static const char kLineTypeSessionPhone = 'p';
static const char kLineTypeSessionBandwidth = 'b';
static const char kLineTypeTiming = 't';
static const char kLineTypeRepeatTimes = 'r';
static const char kLineTypeTimeZone = 'z';
static const char kLineTypeEncryptionKey = 'k';
static const char kLineTypeMedia = 'm';
static const char kLineTypeConnection = 'c';
static const char kLineTypeAttributes = 'a';
// Attributes
static const char kAttributeGroup[] = "group";
static const char kAttributeMid[] = "mid";
static const char kAttributeMsid[] = "msid";
static const char kAttributeBundleOnly[] = "bundle-only";
static const char kAttributeRtcpMux[] = "rtcp-mux";
static const char kAttributeRtcpReducedSize[] = "rtcp-rsize";
static const char kAttributeSsrc[] = "ssrc";
static const char kSsrcAttributeCname[] = "cname";
static const char kAttributeExtmapAllowMixed[] = "extmap-allow-mixed";
static const char kAttributeExtmap[] = "extmap";
// draft-alvestrand-mmusic-msid-01
// a=msid-semantic: WMS
// This is a legacy field supported only for Plan B semantics.
static const char kAttributeMsidSemantics[] = "msid-semantic";
static const char kMediaStreamSemantic[] = "WMS";
static const char kSsrcAttributeMsid[] = "msid";
static const char kDefaultMsid[] = "default";
static const char kNoStreamMsid[] = "-";
static const char kAttributeSsrcGroup[] = "ssrc-group";
static const char kAttributeCandidate[] = "candidate";
static const char kAttributeCandidateTyp[] = "typ";
static const char kAttributeCandidateRaddr[] = "raddr";
static const char kAttributeCandidateRport[] = "rport";
static const char kAttributeCandidateUfrag[] = "ufrag";
static const char kAttributeCandidatePwd[] = "pwd";
static const char kAttributeCandidateGeneration[] = "generation";
static const char kAttributeCandidateNetworkId[] = "network-id";
static const char kAttributeCandidateNetworkCost[] = "network-cost";
static const char kAttributeFingerprint[] = "fingerprint";
static const char kAttributeSetup[] = "setup";
static const char kAttributeFmtp[] = "fmtp";
static const char kAttributeRtpmap[] = "rtpmap";
static const char kAttributeSctpmap[] = "sctpmap";
static const char kAttributeRtcp[] = "rtcp";
static const char kAttributeIceUfrag[] = "ice-ufrag";
static const char kAttributeIcePwd[] = "ice-pwd";
static const char kAttributeIceLite[] = "ice-lite";
static const char kAttributeIceOption[] = "ice-options";
static const char kAttributeSendOnly[] = "sendonly";
static const char kAttributeRecvOnly[] = "recvonly";
static const char kAttributeRtcpFb[] = "rtcp-fb";
static const char kAttributeSendRecv[] = "sendrecv";
static const char kAttributeInactive[] = "inactive";
// draft-ietf-mmusic-sctp-sdp-26
// a=sctp-port, a=max-message-size
static const char kAttributeSctpPort[] = "sctp-port";
static const char kAttributeMaxMessageSize[] = "max-message-size";
static const int kDefaultSctpMaxMessageSize = 65536;
// draft-ietf-mmusic-sdp-simulcast-13
// a=simulcast
static const char kAttributeSimulcast[] = "simulcast";
// draft-ietf-mmusic-rid-15
// a=rid
static const char kAttributeRid[] = "rid";
static const char kAttributePacketization[] = "packetization";
// Experimental flags
static const char kAttributeXGoogleFlag[] = "x-google-flag";
static const char kValueConference[] = "conference";
static const char kAttributeRtcpRemoteEstimate[] = "remote-net-estimate";
// Candidate
static const char kCandidateHost[] = "host";
static const char kCandidateSrflx[] = "srflx";
static const char kCandidatePrflx[] = "prflx";
static const char kCandidateRelay[] = "relay";
static const char kTcpCandidateType[] = "tcptype";
// rtc::StringBuilder doesn't have a << overload for chars, while rtc::split and
// rtc::tokenize_first both take a char delimiter. To handle both cases these
// constants come in pairs of a chars and length-one strings.
static const char kSdpDelimiterEqual[] = "=";
static const char kSdpDelimiterEqualChar = '=';
static const char kSdpDelimiterSpace[] = " ";
static const char kSdpDelimiterSpaceChar = ' ';
static const char kSdpDelimiterColon[] = ":";
static const char kSdpDelimiterColonChar = ':';
static const char kSdpDelimiterSemicolon[] = ";";
static const char kSdpDelimiterSemicolonChar = ';';
static const char kSdpDelimiterSlashChar = '/';
static const char kNewLineChar = '\n';
static const char kReturnChar = '\r';
static const char kLineBreak[] = "\r\n";
// TODO(deadbeef): Generate the Session and Time description
// instead of hardcoding.
static const char kSessionVersion[] = "v=0";
// RFC 4566
static const char kSessionOriginUsername[] = "-";
static const char kSessionOriginSessionId[] = "0";
static const char kSessionOriginSessionVersion[] = "0";
static const char kSessionOriginNettype[] = "IN";
static const char kSessionOriginAddrtype[] = "IP4";
static const char kSessionOriginAddress[] = "127.0.0.1";
static const char kSessionName[] = "s=-";
static const char kTimeDescription[] = "t=0 0";
static const char kAttrGroup[] = "a=group:BUNDLE";
static const char kConnectionNettype[] = "IN";
static const char kConnectionIpv4Addrtype[] = "IP4";
static const char kConnectionIpv6Addrtype[] = "IP6";
static const char kMediaTypeVideo[] = "video";
static const char kMediaTypeAudio[] = "audio";
static const char kMediaTypeData[] = "application";
static const char kMediaPortRejected[] = "0";
// draft-ietf-mmusic-trickle-ice-01
// When no candidates have been gathered, set the connection
// address to IP6 ::.
// TODO(perkj): FF can not parse IP6 ::. See http://crbug/430333
// Use IPV4 per default.
static const char kDummyAddress[] = "0.0.0.0";
static const char kDummyPort[] = "9";
static const char kDefaultSctpmapProtocol[] = "webrtc-datachannel";
// RTP payload type is in the 0-127 range. Use -1 to indicate "all" payload
// types.
const int kWildcardPayloadType = -1;
// Maximum number of channels allowed.
static const size_t kMaxNumberOfChannels = 24;
struct SsrcInfo {
uint32_t ssrc_id;
std::string cname;
std::string stream_id;
std::string track_id;
};
using SsrcInfoVec = std::vector<SsrcInfo>;
using SsrcGroupVec = std::vector<SsrcGroup>;
static void BuildMediaDescription(const ContentInfo* content_info,
const TransportInfo* transport_info,
const cricket::MediaType media_type,
const std::vector<Candidate>& candidates,
int msid_signaling,
std::string* message);
static void BuildMediaLine(const cricket::MediaType media_type,
const ContentInfo* content_info,
const MediaContentDescription* media_desc,
std::string* message);
static void BuildRtpContentAttributes(const MediaContentDescription* media_desc,
const cricket::MediaType media_type,
int msid_signaling,
std::string* message);
static void BuildRtpHeaderExtensions(const RtpHeaderExtensions& extensions,
std::string* message);
static void BuildRtpmap(const MediaContentDescription* media_desc,
const cricket::MediaType media_type,
std::string* message);
static void BuildCandidate(const std::vector<Candidate>& candidates,
bool include_ufrag,
std::string* message);
static void BuildIceUfragPwd(const TransportInfo* transport_info,
std::string* message);
static void BuildDtlsFingerprintSetup(const TransportInfo* transport_info,
std::string* message);
static void BuildIceOptions(const std::vector<std::string>& transport_options,
std::string* message);
static bool ParseSessionDescription(absl::string_view message,
size_t* pos,
std::string* session_id,
std::string* session_version,
TransportDescription* session_td,
RtpHeaderExtensions* session_extmaps,
rtc::SocketAddress* connection_addr,
cricket::SessionDescription* desc,
SdpParseError* error);
static bool ParseMediaDescription(
absl::string_view message,
const TransportDescription& session_td,
const RtpHeaderExtensions& session_extmaps,
size_t* pos,
const rtc::SocketAddress& session_connection_addr,
cricket::SessionDescription* desc,
std::vector<std::unique_ptr<JsepIceCandidate>>* candidates,
SdpParseError* error);
static bool ParseContent(
absl::string_view message,
const cricket::MediaType media_type,
int mline_index,
absl::string_view protocol,
const std::vector<int>& payload_types,
size_t* pos,
std::string* content_name,
bool* bundle_only,
int* msid_signaling,
MediaContentDescription* media_desc,
TransportDescription* transport,
std::vector<std::unique_ptr<JsepIceCandidate>>* candidates,
SdpParseError* error);
static bool ParseGroupAttribute(absl::string_view line,
cricket::SessionDescription* desc,
SdpParseError* error);
static bool ParseSsrcAttribute(absl::string_view line,
SsrcInfoVec* ssrc_infos,
int* msid_signaling,
SdpParseError* error);
static bool ParseSsrcGroupAttribute(absl::string_view line,
SsrcGroupVec* ssrc_groups,
SdpParseError* error);
static bool ParseRtpmapAttribute(absl::string_view line,
const cricket::MediaType media_type,
const std::vector<int>& payload_types,
MediaContentDescription* media_desc,
SdpParseError* error);
static bool ParseFmtpAttributes(absl::string_view line,
const cricket::MediaType media_type,
MediaContentDescription* media_desc,
SdpParseError* error);
static bool ParseFmtpParam(absl::string_view line,
std::string* parameter,
std::string* value,
SdpParseError* error);
static bool ParsePacketizationAttribute(absl::string_view line,
const cricket::MediaType media_type,
MediaContentDescription* media_desc,
SdpParseError* error);
static bool ParseRtcpFbAttribute(absl::string_view line,
const cricket::MediaType media_type,
MediaContentDescription* media_desc,
SdpParseError* error);
static bool ParseIceOptions(absl::string_view line,
std::vector<std::string>* transport_options,
SdpParseError* error);
static bool ParseExtmap(absl::string_view line,
RtpExtension* extmap,
SdpParseError* error);
static bool ParseFingerprintAttribute(
absl::string_view line,
std::unique_ptr<rtc::SSLFingerprint>* fingerprint,
SdpParseError* error);
static bool ParseDtlsSetup(absl::string_view line,
cricket::ConnectionRole* role,
SdpParseError* error);
static bool ParseMsidAttribute(absl::string_view line,
std::vector<std::string>* stream_ids,
std::string* track_id,
SdpParseError* error);
static void RemoveInvalidRidDescriptions(const std::vector<int>& payload_types,
std::vector<RidDescription>* rids);
static SimulcastLayerList RemoveRidsFromSimulcastLayerList(
const std::set<std::string>& to_remove,
const SimulcastLayerList& layers);
static void RemoveInvalidRidsFromSimulcast(
const std::vector<RidDescription>& rids,
SimulcastDescription* simulcast);
// Helper functions
// Below ParseFailed*** functions output the line that caused the parsing
// failure and the detailed reason (`description`) of the failure to `error`.
// The functions always return false so that they can be used directly in the
// following way when error happens:
// "return ParseFailed***(...);"
// The line starting at `line_start` of `message` is the failing line.
// The reason for the failure should be provided in the `description`.
// An example of a description could be "unknown character".
static bool ParseFailed(absl::string_view message,
size_t line_start,
std::string description,
SdpParseError* error) {
// Get the first line of `message` from `line_start`.
absl::string_view first_line;
size_t line_end = message.find(kNewLineChar, line_start);
if (line_end != std::string::npos) {
if (line_end > 0 && (message.at(line_end - 1) == kReturnChar)) {
--line_end;
}
first_line = message.substr(line_start, (line_end - line_start));
} else {
first_line = message.substr(line_start);
}
RTC_LOG(LS_ERROR) << "Failed to parse: \"" << first_line
<< "\". Reason: " << description;
if (error) {
// TODO(bugs.webrtc.org/13220): In C++17, we can use plain assignment, with
// a string_view on the right hand side.
error->line.assign(first_line.data(), first_line.size());
error->description = std::move(description);
}
return false;
}
// `line` is the failing line. The reason for the failure should be
// provided in the `description`.
static bool ParseFailed(absl::string_view line,
std::string description,
SdpParseError* error) {
return ParseFailed(line, 0, std::move(description), error);
}
// Parses failure where the failing SDP line isn't know or there are multiple
// failing lines.
static bool ParseFailed(std::string description, SdpParseError* error) {
return ParseFailed("", std::move(description), error);
}
// `line` is the failing line. The failure is due to the fact that `line`
// doesn't have `expected_fields` fields.
static bool ParseFailedExpectFieldNum(absl::string_view line,
int expected_fields,
SdpParseError* error) {
rtc::StringBuilder description;
description << "Expects " << expected_fields << " fields.";
return ParseFailed(line, description.Release(), error);
}
// `line` is the failing line. The failure is due to the fact that `line` has
// less than `expected_min_fields` fields.
static bool ParseFailedExpectMinFieldNum(absl::string_view line,
int expected_min_fields,
SdpParseError* error) {
rtc::StringBuilder description;
description << "Expects at least " << expected_min_fields << " fields.";
return ParseFailed(line, description.Release(), error);
}
// `line` is the failing line. The failure is due to the fact that it failed to
// get the value of `attribute`.
static bool ParseFailedGetValue(absl::string_view line,
absl::string_view attribute,
SdpParseError* error) {
rtc::StringBuilder description;
description << "Failed to get the value of attribute: " << attribute;
return ParseFailed(line, description.Release(), error);
}
// The line starting at `line_start` of `message` is the failing line. The
// failure is due to the line type (e.g. the "m" part of the "m-line")
// not matching what is expected. The expected line type should be
// provided as `line_type`.
static bool ParseFailedExpectLine(absl::string_view message,
size_t line_start,
const char line_type,
absl::string_view line_value,
SdpParseError* error) {
rtc::StringBuilder description;
description << "Expect line: " << std::string(1, line_type) << "="
<< line_value;
return ParseFailed(message, line_start, description.Release(), error);
}
static bool AddLine(absl::string_view line, std::string* message) {
if (!message)
return false;
message->append(line.data(), line.size());
message->append(kLineBreak);
return true;
}
// Trim return character, if any.
static absl::string_view TrimReturnChar(absl::string_view line) {
if (!line.empty() && line.back() == kReturnChar) {
line.remove_suffix(1);
}
return line;
}
// Gets line of `message` starting at `pos`, and checks overall SDP syntax. On
// success, advances `pos` to the next line.
static std::optional<absl::string_view> GetLine(absl::string_view message,
size_t* pos) {
size_t line_end = message.find(kNewLineChar, *pos);
if (line_end == absl::string_view::npos) {
return std::nullopt;
}
absl::string_view line =
TrimReturnChar(message.substr(*pos, line_end - *pos));
// RFC 4566
// An SDP session description consists of a number of lines of text of
// the form:
// <type>=<value>
// where <type> MUST be exactly one case-significant character and
// <value> is structured text whose format depends on <type>.
// Whitespace MUST NOT be used on either side of the "=" sign.
//
// However, an exception to the whitespace rule is made for "s=", since
// RFC4566 also says:
//
// If a session has no meaningful name, the value "s= " SHOULD be used
// (i.e., a single space as the session name).
if (line.length() < 3 || !islower(static_cast<unsigned char>(line[0])) ||
line[1] != kSdpDelimiterEqualChar ||
(line[0] != kLineTypeSessionName && line[2] == kSdpDelimiterSpaceChar)) {
return std::nullopt;
}
*pos = line_end + 1;
return line;
}
// Init `os` to "`type`=`value`".
static void InitLine(const char type,
absl::string_view value,
rtc::StringBuilder* os) {
os->Clear();
*os << std::string(1, type) << kSdpDelimiterEqual << value;
}
// Init `os` to "a=`attribute`".
static void InitAttrLine(absl::string_view attribute, rtc::StringBuilder* os) {
InitLine(kLineTypeAttributes, attribute, os);
}
// Writes a SDP attribute line based on `attribute` and `value` to `message`.
static void AddAttributeLine(absl::string_view attribute,
int value,
std::string* message) {
rtc::StringBuilder os;
InitAttrLine(attribute, &os);
os << kSdpDelimiterColon << value;
AddLine(os.str(), message);
}
static bool IsLineType(absl::string_view message,
const char type,
size_t line_start) {
if (message.size() < line_start + kLinePrefixLength) {
return false;
}
return (message[line_start] == type &&
message[line_start + 1] == kSdpDelimiterEqualChar);
}
static bool IsLineType(absl::string_view line, const char type) {
return IsLineType(line, type, 0);
}
static std::optional<absl::string_view>
GetLineWithType(absl::string_view message, size_t* pos, const char type) {
if (IsLineType(message, type, *pos)) {
return GetLine(message, pos);
}
return std::nullopt;
}
static bool HasAttribute(absl::string_view line, absl::string_view attribute) {
if (line.compare(kLinePrefixLength, attribute.size(), attribute) == 0) {
// Make sure that the match is not only a partial match. If length of
// strings doesn't match, the next character of the line must be ':' or ' '.
// This function is also used for media descriptions (e.g., "m=audio 9..."),
// hence the need to also allow space in the end.
RTC_CHECK_LE(kLinePrefixLength + attribute.size(), line.size());
if ((kLinePrefixLength + attribute.size()) == line.size() ||
line[kLinePrefixLength + attribute.size()] == kSdpDelimiterColonChar ||
line[kLinePrefixLength + attribute.size()] == kSdpDelimiterSpaceChar) {
return true;
}
}
return false;
}
static bool AddSsrcLine(uint32_t ssrc_id,
absl::string_view attribute,
absl::string_view value,
std::string* message) {
// RFC 5576
// a=ssrc:<ssrc-id> <attribute>:<value>
rtc::StringBuilder os;
InitAttrLine(kAttributeSsrc, &os);
os << kSdpDelimiterColon << ssrc_id << kSdpDelimiterSpace << attribute
<< kSdpDelimiterColon << value;
return AddLine(os.str(), message);
}
// Get value only from <attribute>:<value>.
static bool GetValue(absl::string_view message,
absl::string_view attribute,
std::string* value,
SdpParseError* error) {
std::string leftpart;
if (!rtc::tokenize_first(message, kSdpDelimiterColonChar, &leftpart, value)) {
return ParseFailedGetValue(message, attribute, error);
}
// The left part should end with the expected attribute.
if (leftpart.length() < attribute.length() ||
absl::string_view(leftpart).compare(
leftpart.length() - attribute.length(), attribute.length(),
attribute) != 0) {
return ParseFailedGetValue(message, attribute, error);
}
return true;
}
// Get a single [token] from <attribute>:<token>
static bool GetSingleTokenValue(absl::string_view message,
absl::string_view attribute,
std::string* value,
SdpParseError* error) {
if (!GetValue(message, attribute, value, error)) {
return false;
}
if (!absl::c_all_of(absl::string_view(*value), IsTokenChar)) {
rtc::StringBuilder description;
description << "Illegal character found in the value of " << attribute;
return ParseFailed(message, description.Release(), error);
}
return true;
}
static bool CaseInsensitiveFind(std::string str1, std::string str2) {
absl::c_transform(str1, str1.begin(), ::tolower);
absl::c_transform(str2, str2.begin(), ::tolower);
return str1.find(str2) != std::string::npos;
}
template <class T>
static bool GetValueFromString(absl::string_view line,
absl::string_view s,
T* t,
SdpParseError* error) {
if (!rtc::FromString(s, t)) {
rtc::StringBuilder description;
description << "Invalid value: " << s << ".";
return ParseFailed(line, description.Release(), error);
}
return true;
}
static bool GetPayloadTypeFromString(absl::string_view line,
absl::string_view s,
int* payload_type,
SdpParseError* error) {
return GetValueFromString(line, s, payload_type, error) &&
cricket::IsValidRtpPayloadType(*payload_type);
}
// Creates a StreamParams track in the case when no SSRC lines are signaled.
// This is a track that does not contain SSRCs and only contains
// stream_ids/track_id if it's signaled with a=msid lines.
void CreateTrackWithNoSsrcs(const std::vector<std::string>& msid_stream_ids,
absl::string_view msid_track_id,
const std::vector<RidDescription>& rids,
StreamParamsVec* tracks) {
StreamParams track;
if (msid_track_id.empty() && rids.empty()) {
// We only create an unsignaled track if a=msid lines were signaled.
RTC_LOG(LS_INFO) << "MSID not signaled, skipping creation of StreamParams";
return;
}
track.set_stream_ids(msid_stream_ids);
track.id = std::string(msid_track_id);
track.set_rids(rids);
tracks->push_back(track);
}
// Creates the StreamParams tracks, for the case when SSRC lines are signaled.
// `msid_stream_ids` and `msid_track_id` represent the stream/track ID from the
// "a=msid" attribute, if it exists. They are empty if the attribute does not
// exist. We prioritize getting stream_ids/track_ids signaled in a=msid lines.
void CreateTracksFromSsrcInfos(const SsrcInfoVec& ssrc_infos,
const std::vector<std::string>& msid_stream_ids,
absl::string_view msid_track_id,
StreamParamsVec* tracks,
int msid_signaling) {
RTC_DCHECK(tracks);
for (const SsrcInfo& ssrc_info : ssrc_infos) {
// According to https://tools.ietf.org/html/rfc5576#section-6.1, the CNAME
// attribute is mandatory, but we relax that restriction.
if (ssrc_info.cname.empty()) {
RTC_LOG(LS_WARNING) << "CNAME attribute missing for SSRC "
<< ssrc_info.ssrc_id;
}
std::vector<std::string> stream_ids;
std::string track_id;
if (msid_signaling & cricket::kMsidSignalingMediaSection) {
// This is the case with Unified Plan SDP msid signaling.
stream_ids = msid_stream_ids;
track_id = std::string(msid_track_id);
} else if (msid_signaling & cricket::kMsidSignalingSsrcAttribute) {
// This is the case with Plan B SDP msid signaling.
stream_ids.push_back(ssrc_info.stream_id);
track_id = ssrc_info.track_id;
} else if (msid_signaling == cricket::kMsidSignalingNotUsed) {
// Since no media streams isn't supported with older SDP signaling, we
// use a default stream id.
stream_ids.push_back(kDefaultMsid);
}
auto track_it = absl::c_find_if(
*tracks,
[track_id](const StreamParams& track) { return track.id == track_id; });
if (track_it == tracks->end()) {
// If we don't find an existing track, create a new one.
tracks->push_back(StreamParams());
track_it = tracks->end() - 1;
}
StreamParams& track = *track_it;
track.add_ssrc(ssrc_info.ssrc_id);
track.cname = ssrc_info.cname;
track.set_stream_ids(stream_ids);
track.id = track_id;
}
for (StreamParams& stream : *tracks) {
// If a track ID wasn't populated from the SSRC attributes OR the
// msid attribute, use default/random values. This happens after
// deduplication.
if (stream.id.empty()) {
stream.id = rtc::CreateRandomString(8);
}
}
}
void GetMediaStreamIds(const ContentInfo* content,
std::set<std::string>* labels) {
for (const StreamParams& stream_params :
content->media_description()->streams()) {
for (const std::string& stream_id : stream_params.stream_ids()) {
labels->insert(stream_id);
}
}
}
// Get ip and port of the default destination from the `candidates` with the
// given value of `component_id`. The default candidate should be the one most
// likely to work, typically IPv4 relay.
// RFC 5245
// The value of `component_id` currently supported are 1 (RTP) and 2 (RTCP).
// TODO(deadbeef): Decide the default destination in webrtcsession and
// pass it down via SessionDescription.
static void GetDefaultDestination(const std::vector<Candidate>& candidates,
int component_id,
std::string* port,
std::string* ip,
std::string* addr_type) {
*addr_type = kConnectionIpv4Addrtype;
*port = kDummyPort;
*ip = kDummyAddress;
int current_preference = 0; // Start with lowest preference
int current_family = AF_UNSPEC;
for (const Candidate& candidate : candidates) {
if (candidate.component() != component_id) {
continue;
}
// Default destination should be UDP only.
if (candidate.protocol() != cricket::UDP_PROTOCOL_NAME) {
continue;
}
const int preference = candidate.type_preference();
const int family = candidate.address().ipaddr().family();
// See if this candidate is more preferable then the current one if it's the
// same family. Or if the current family is IPv4 already so we could safely
// ignore all IPv6 ones. WebRTC bug 4269.
// http://code.google.com/p/webrtc/issues/detail?id=4269
if ((preference <= current_preference && current_family == family) ||
(current_family == AF_INET && family == AF_INET6)) {
continue;
}
if (family == AF_INET) {
addr_type->assign(kConnectionIpv4Addrtype);
} else if (family == AF_INET6) {
addr_type->assign(kConnectionIpv6Addrtype);
}
current_preference = preference;
current_family = family;
*port = candidate.address().PortAsString();
*ip = candidate.address().ipaddr().ToString();
}
}
// Gets "a=rtcp" line if found default RTCP candidate from `candidates`.
static std::string GetRtcpLine(const std::vector<Candidate>& candidates) {
std::string rtcp_port, rtcp_ip, addr_type;
GetDefaultDestination(candidates, ICE_CANDIDATE_COMPONENT_RTCP, &rtcp_port,
&rtcp_ip, &addr_type);
// Found default RTCP candidate.
// RFC 5245
// If the agent is utilizing RTCP, it MUST encode the RTCP candidate
// using the a=rtcp attribute as defined in RFC 3605.
// RFC 3605
// rtcp-attribute = "a=rtcp:" port [nettype space addrtype space
// connection-address] CRLF
rtc::StringBuilder os;
InitAttrLine(kAttributeRtcp, &os);
os << kSdpDelimiterColon << rtcp_port << " " << kConnectionNettype << " "
<< addr_type << " " << rtcp_ip;
return os.Release();
}
// Get candidates according to the mline index from SessionDescriptionInterface.
static void GetCandidatesByMindex(const SessionDescriptionInterface& desci,
int mline_index,
std::vector<Candidate>* candidates) {
if (!candidates) {
return;
}
const IceCandidateCollection* cc = desci.candidates(mline_index);
for (size_t i = 0; i < cc->count(); ++i) {
const IceCandidateInterface* candidate = cc->at(i);
candidates->push_back(candidate->candidate());
}
}
static bool IsValidPort(int port) {
return port >= 0 && port <= 65535;
}
std::string SdpSerialize(const JsepSessionDescription& jdesc) {
const cricket::SessionDescription* desc = jdesc.description();
if (!desc) {
return "";
}
std::string message;
// Session Description.
AddLine(kSessionVersion, &message);
// Session Origin
// RFC 4566
// o=<username> <sess-id> <sess-version> <nettype> <addrtype>
// <unicast-address>
rtc::StringBuilder os;
InitLine(kLineTypeOrigin, kSessionOriginUsername, &os);
const std::string& session_id =
jdesc.session_id().empty() ? kSessionOriginSessionId : jdesc.session_id();
const std::string& session_version = jdesc.session_version().empty()
? kSessionOriginSessionVersion
: jdesc.session_version();
os << " " << session_id << " " << session_version << " "
<< kSessionOriginNettype << " " << kSessionOriginAddrtype << " "
<< kSessionOriginAddress;
AddLine(os.str(), &message);
AddLine(kSessionName, &message);
// Time Description.
AddLine(kTimeDescription, &message);
// BUNDLE Groups
std::vector<const cricket::ContentGroup*> groups =
desc->GetGroupsByName(cricket::GROUP_TYPE_BUNDLE);
for (const cricket::ContentGroup* group : groups) {
std::string group_line = kAttrGroup;
RTC_DCHECK(group != NULL);
for (const std::string& content_name : group->content_names()) {
group_line.append(" ");
group_line.append(content_name);
}
AddLine(group_line, &message);
}
// Mixed one- and two-byte header extension.
if (desc->extmap_allow_mixed()) {
InitAttrLine(kAttributeExtmapAllowMixed, &os);
AddLine(os.str(), &message);
}
// MediaStream semantics.
// TODO(bugs.webrtc.org/10421): Change to & cricket::kMsidSignalingSemantic
// when we think it's safe to do so, so that we gradually fade out this old
// line that was removed from the specification.
if (desc->msid_signaling() != cricket::kMsidSignalingNotUsed) {
InitAttrLine(kAttributeMsidSemantics, &os);
os << kSdpDelimiterColon << " " << kMediaStreamSemantic;
// TODO(bugs.webrtc.org/10421): this code only looks at the first
// audio/video content. Fixing that might result in much larger SDP and the
// msid-semantic line should eventually go away so this is not worth fixing.
std::set<std::string> media_stream_ids;
const ContentInfo* audio_content = GetFirstAudioContent(desc);
if (audio_content)
GetMediaStreamIds(audio_content, &media_stream_ids);
const ContentInfo* video_content = GetFirstVideoContent(desc);
if (video_content)
GetMediaStreamIds(video_content, &media_stream_ids);
for (const std::string& id : media_stream_ids) {
os << " " << id;
}
AddLine(os.str(), &message);
}
// a=ice-lite
//
// TODO(deadbeef): It's weird that we need to iterate TransportInfos for
// this, when it's a session-level attribute. It really should be moved to a
// session-level structure like SessionDescription.
for (const cricket::TransportInfo& transport : desc->transport_infos()) {
if (transport.description.ice_mode == cricket::ICEMODE_LITE) {
InitAttrLine(kAttributeIceLite, &os);
AddLine(os.str(), &message);
break;
}
}
// Preserve the order of the media contents.
int mline_index = -1;
for (const ContentInfo& content : desc->contents()) {
std::vector<Candidate> candidates;
GetCandidatesByMindex(jdesc, ++mline_index, &candidates);
BuildMediaDescription(&content, desc->GetTransportInfoByName(content.name),
content.media_description()->type(), candidates,
desc->msid_signaling(), &message);
}
return message;
}
// Serializes the passed in IceCandidateInterface to a SDP string.
// candidate - The candidate to be serialized.
std::string SdpSerializeCandidate(const IceCandidateInterface& candidate) {
return SdpSerializeCandidate(candidate.candidate());
}
// Serializes a cricket Candidate.
std::string SdpSerializeCandidate(const cricket::Candidate& candidate) {
std::string message;
std::vector<cricket::Candidate> candidates(1, candidate);
BuildCandidate(candidates, true, &message);
// From WebRTC draft section 4.8.1.1 candidate-attribute will be
// just candidate:<candidate> not a=candidate:<blah>CRLF
RTC_DCHECK(message.find("a=") == 0);
message.erase(0, 2);
RTC_DCHECK(message.find(kLineBreak) == message.size() - 2);
message.resize(message.size() - 2);
return message;
}
bool SdpDeserialize(absl::string_view message,
JsepSessionDescription* jdesc,
SdpParseError* error) {
std::string session_id;
std::string session_version;
TransportDescription session_td("", "");
RtpHeaderExtensions session_extmaps;
rtc::SocketAddress session_connection_addr;
auto desc = std::make_unique<cricket::SessionDescription>();
size_t current_pos = 0;
// Session Description
if (!ParseSessionDescription(message, &current_pos, &session_id,
&session_version, &session_td, &session_extmaps,
&session_connection_addr, desc.get(), error)) {
return false;
}
// Media Description
std::vector<std::unique_ptr<JsepIceCandidate>> candidates;
if (!ParseMediaDescription(message, session_td, session_extmaps, &current_pos,
session_connection_addr, desc.get(), &candidates,
error)) {
return false;
}
jdesc->Initialize(std::move(desc), session_id, session_version);
for (const auto& candidate : candidates) {
jdesc->AddCandidate(candidate.get());
}
return true;
}
bool SdpDeserializeCandidate(absl::string_view message,
JsepIceCandidate* jcandidate,
SdpParseError* error) {
RTC_DCHECK(jcandidate != NULL);
Candidate candidate;
if (!ParseCandidate(message, &candidate, error, true)) {
return false;
}
jcandidate->SetCandidate(candidate);
return true;
}
bool SdpDeserializeCandidate(absl::string_view transport_name,
absl::string_view message,
cricket::Candidate* candidate,
SdpParseError* error) {
RTC_DCHECK(candidate != nullptr);
if (!ParseCandidate(message, candidate, error, true)) {
return false;
}
candidate->set_transport_name(transport_name);
return true;
}
bool ParseCandidate(absl::string_view message,
Candidate* candidate,
SdpParseError* error,
bool is_raw) {
RTC_DCHECK(candidate != NULL);
// Makes sure `message` contains only one line.
absl::string_view first_line;
size_t line_end = message.find(kNewLineChar);
if (line_end == absl::string_view::npos) {
first_line = message;
} else if (line_end + 1 == message.size()) {
first_line = message.substr(0, line_end);
} else {
return ParseFailed(message, 0, "Expect one line only", error);
}
// Trim return char, if any.
first_line = TrimReturnChar(first_line);
// From WebRTC draft section 4.8.1.1 candidate-attribute should be
// candidate:<candidate> when trickled, but we still support
// a=candidate:<blah>CRLF for backward compatibility and for parsing a line
// from the SDP.
if (IsLineType(first_line, kLineTypeAttributes)) {
first_line = first_line.substr(kLinePrefixLength);
}
std::string attribute_candidate;
std::string candidate_value;
// `first_line` must be in the form of "candidate:<value>".
if (!rtc::tokenize_first(first_line, kSdpDelimiterColonChar,
&attribute_candidate, &candidate_value) ||
attribute_candidate != kAttributeCandidate) {
if (is_raw) {
rtc::StringBuilder description;
description << "Expect line: " << kAttributeCandidate
<< ":"
"<candidate-str>";
return ParseFailed(first_line, 0, description.Release(), error);
} else {
return ParseFailedExpectLine(first_line, 0, kLineTypeAttributes,
kAttributeCandidate, error);
}
}
std::vector<absl::string_view> fields =
rtc::split(candidate_value, kSdpDelimiterSpaceChar);
// RFC 5245
// a=candidate:<foundation> <component-id> <transport> <priority>
// <connection-address> <port> typ <candidate-types>
// [raddr <connection-address>] [rport <port>]
// *(SP extension-att-name SP extension-att-value)
const size_t expected_min_fields = 8;
if (fields.size() < expected_min_fields ||
(fields[6] != kAttributeCandidateTyp)) {
return ParseFailedExpectMinFieldNum(first_line, expected_min_fields, error);
}
const absl::string_view foundation = fields[0];
int component_id = 0;
if (!GetValueFromString(first_line, fields[1], &component_id, error)) {
return false;
}
const absl::string_view transport = fields[2];
uint32_t priority = 0;
if (!GetValueFromString(first_line, fields[3], &priority, error)) {
return false;
}
const absl::string_view connection_address = fields[4];
int port = 0;
if (!GetValueFromString(first_line, fields[5], &port, error)) {
return false;
}
if (!IsValidPort(port)) {
return ParseFailed(first_line, "Invalid port number.", error);
}
SocketAddress address(connection_address, port);
std::optional<cricket::ProtocolType> protocol =
cricket::StringToProto(transport);
if (!protocol) {
return ParseFailed(first_line, "Unsupported transport type.", error);
}
bool tcp_protocol = false;
switch (*protocol) {
// Supported protocols.
case cricket::PROTO_UDP:
break;
case cricket::PROTO_TCP:
case cricket::PROTO_SSLTCP:
tcp_protocol = true;
break;
default:
return ParseFailed(first_line, "Unsupported transport type.", error);
}
IceCandidateType candidate_type;
const absl::string_view type = fields[7];
if (type == kCandidateHost) {
candidate_type = IceCandidateType::kHost;
} else if (type == kCandidateSrflx) {
candidate_type = IceCandidateType::kSrflx;
} else if (type == kCandidateRelay) {
candidate_type = IceCandidateType::kRelay;
} else if (type == kCandidatePrflx) {
candidate_type = IceCandidateType::kPrflx;
} else {
return ParseFailed(first_line, "Unsupported candidate type.", error);
}
size_t current_position = expected_min_fields;
SocketAddress related_address;
// The 2 optional fields for related address
// [raddr <connection-address>] [rport <port>]
if (fields.size() >= (current_position + 2) &&
fields[current_position] == kAttributeCandidateRaddr) {
related_address.SetIP(fields[++current_position]);
++current_position;
}
if (fields.size() >= (current_position + 2) &&
fields[current_position] == kAttributeCandidateRport) {
int port = 0;
if (!GetValueFromString(first_line, fields[++current_position], &port,
error)) {
return false;
}
if (!IsValidPort(port)) {
return ParseFailed(first_line, "Invalid port number.", error);
}
related_address.SetPort(port);
++current_position;
}
// If this is a TCP candidate, it has additional extension as defined in
// RFC 6544.
absl::string_view tcptype;
if (fields.size() >= (current_position + 2) &&
fields[current_position] == kTcpCandidateType) {
tcptype = fields[++current_position];
++current_position;
if (tcptype != cricket::TCPTYPE_ACTIVE_STR &&
tcptype != cricket::TCPTYPE_PASSIVE_STR &&
tcptype != cricket::TCPTYPE_SIMOPEN_STR) {
return ParseFailed(first_line, "Invalid TCP candidate type.", error);
}
if (!tcp_protocol) {
return ParseFailed(first_line, "Invalid non-TCP candidate", error);
}
} else if (tcp_protocol) {
// We allow the tcptype to be missing, for backwards compatibility,
// treating it as a passive candidate.
// TODO(bugs.webrtc.org/11466): Treat a missing tcptype as an error?
tcptype = cricket::TCPTYPE_PASSIVE_STR;
}
// Extension
// Though non-standard, we support the ICE ufrag and pwd being signaled on
// the candidate to avoid issues with confusing which generation a candidate
// belongs to when trickling multiple generations at the same time.
absl::string_view username;
absl::string_view password;
uint32_t generation = 0;
uint16_t network_id = 0;
uint16_t network_cost = 0;
for (size_t i = current_position; i + 1 < fields.size(); ++i) {
// RFC 5245
// *(SP extension-att-name SP extension-att-value)
if (fields[i] == kAttributeCandidateGeneration) {
if (!GetValueFromString(first_line, fields[++i], &generation, error)) {
return false;
}
} else if (fields[i] == kAttributeCandidateUfrag) {
username = fields[++i];
} else if (fields[i] == kAttributeCandidatePwd) {
password = fields[++i];
} else if (fields[i] == kAttributeCandidateNetworkId) {
if (!GetValueFromString(first_line, fields[++i], &network_id, error)) {
return false;
}
} else if (fields[i] == kAttributeCandidateNetworkCost) {
if (!GetValueFromString(first_line, fields[++i], &network_cost, error)) {
return false;
}
network_cost = std::min(network_cost, rtc::kNetworkCostMax);
} else {
// Skip the unknown extension.
++i;
}
}
*candidate = Candidate(component_id, cricket::ProtoToString(*protocol),
address, priority, username, password, candidate_type,
generation, foundation, network_id, network_cost);
candidate->set_related_address(related_address);
candidate->set_tcptype(tcptype);
return true;
}
bool ParseIceOptions(absl::string_view line,
std::vector<std::string>* transport_options,
SdpParseError* error) {
std::string ice_options;
if (!GetValue(line, kAttributeIceOption, &ice_options, error)) {
return false;
}
std::vector<absl::string_view> fields =
rtc::split(ice_options, kSdpDelimiterSpaceChar);
for (size_t i = 0; i < fields.size(); ++i) {
transport_options->emplace_back(fields[i]);
}
return true;
}
bool ParseSctpPort(absl::string_view line,
int* sctp_port,
SdpParseError* error) {
// draft-ietf-mmusic-sctp-sdp-26
// a=sctp-port
const size_t expected_min_fields = 2;
std::vector<absl::string_view> fields =
rtc::split(line.substr(kLinePrefixLength), kSdpDelimiterColonChar);
if (fields.size() < expected_min_fields) {
fields = rtc::split(line.substr(kLinePrefixLength), kSdpDelimiterSpaceChar);
}
if (fields.size() < expected_min_fields) {
return ParseFailedExpectMinFieldNum(line, expected_min_fields, error);
}
if (!rtc::FromString(fields[1], sctp_port)) {
return ParseFailed(line, "Invalid sctp port value.", error);
}
return true;
}
bool ParseSctpMaxMessageSize(absl::string_view line,
int* max_message_size,
SdpParseError* error) {
// draft-ietf-mmusic-sctp-sdp-26
// a=max-message-size:199999
const size_t expected_min_fields = 2;
std::vector<absl::string_view> fields =
rtc::split(line.substr(kLinePrefixLength), kSdpDelimiterColonChar);
if (fields.size() < expected_min_fields) {
return ParseFailedExpectMinFieldNum(line, expected_min_fields, error);
}
if (!rtc::FromString(fields[1], max_message_size)) {
return ParseFailed(line, "Invalid SCTP max message size.", error);
}
return true;
}
bool ParseExtmap(absl::string_view line,
RtpExtension* extmap,
SdpParseError* error) {
// RFC 5285
// a=extmap:<value>["/"<direction>] <URI> <extensionattributes>
std::vector<absl::string_view> fields =
rtc::split(line.substr(kLinePrefixLength), kSdpDelimiterSpaceChar);
const size_t expected_min_fields = 2;
if (fields.size() < expected_min_fields) {
return ParseFailedExpectMinFieldNum(line, expected_min_fields, error);
}
absl::string_view uri = fields[1];
std::string value_direction;
if (!GetValue(fields[0], kAttributeExtmap, &value_direction, error)) {
return false;
}
std::vector<absl::string_view> sub_fields =
rtc::split(value_direction, kSdpDelimiterSlashChar);
int value = 0;
if (!GetValueFromString(line, sub_fields[0], &value, error)) {
return false;
}
bool encrypted = false;
if (uri == RtpExtension::kEncryptHeaderExtensionsUri) {
// RFC 6904
// a=extmap:<value["/"<direction>] urn:ietf:params:rtp-hdrext:encrypt <URI>
// <extensionattributes>
const size_t expected_min_fields_encrypted = expected_min_fields + 1;
if (fields.size() < expected_min_fields_encrypted) {
return ParseFailedExpectMinFieldNum(line, expected_min_fields_encrypted,
error);
}
encrypted = true;
uri = fields[2];
if (uri == RtpExtension::kEncryptHeaderExtensionsUri) {
return ParseFailed(line, "Recursive encrypted header.", error);
}
}
*extmap = RtpExtension(uri, value, encrypted);
return true;
}
static void BuildSctpContentAttributes(
std::string* message,
const cricket::SctpDataContentDescription* data_desc) {
rtc::StringBuilder os;
if (data_desc->use_sctpmap()) {
// draft-ietf-mmusic-sctp-sdp-04
// a=sctpmap:sctpmap-number protocol [streams]
rtc::StringBuilder os;
InitAttrLine(kAttributeSctpmap, &os);
os << kSdpDelimiterColon << data_desc->port() << kSdpDelimiterSpace
<< kDefaultSctpmapProtocol << kSdpDelimiterSpace
<< cricket::kMaxSctpStreams;
AddLine(os.str(), message);
} else {
// draft-ietf-mmusic-sctp-sdp-23
// a=sctp-port:<port>
InitAttrLine(kAttributeSctpPort, &os);
os << kSdpDelimiterColon << data_desc->port();
AddLine(os.str(), message);
if (data_desc->max_message_size() != kDefaultSctpMaxMessageSize) {
InitAttrLine(kAttributeMaxMessageSize, &os);
os << kSdpDelimiterColon << data_desc->max_message_size();
AddLine(os.str(), message);
}
}
}
void BuildIceUfragPwd(const TransportInfo* transport_info,
std::string* message) {
RTC_DCHECK(transport_info);
rtc::StringBuilder os;
// RFC 5245
// ice-pwd-att = "ice-pwd" ":" password
// ice-ufrag-att = "ice-ufrag" ":" ufrag
// ice-ufrag
if (!transport_info->description.ice_ufrag.empty()) {
InitAttrLine(kAttributeIceUfrag, &os);
os << kSdpDelimiterColon << transport_info->description.ice_ufrag;
AddLine(os.str(), message);
}
// ice-pwd
if (!transport_info->description.ice_pwd.empty()) {
InitAttrLine(kAttributeIcePwd, &os);
os << kSdpDelimiterColon << transport_info->description.ice_pwd;
AddLine(os.str(), message);
}
}
void BuildDtlsFingerprintSetup(const TransportInfo* transport_info,
std::string* message) {
RTC_DCHECK(transport_info);
rtc::StringBuilder os;
// RFC 4572
// fingerprint-attribute =
// "fingerprint" ":" hash-func SP fingerprint
// When using max-bundle this is already included at session level.
// Insert the fingerprint attribute.
auto fingerprint = transport_info->description.identity_fingerprint.get();
if (!fingerprint) {
return;
}
InitAttrLine(kAttributeFingerprint, &os);
os << kSdpDelimiterColon << fingerprint->algorithm << kSdpDelimiterSpace
<< fingerprint->GetRfc4572Fingerprint();
AddLine(os.str(), message);
// Inserting setup attribute.
if (transport_info->description.connection_role !=
cricket::CONNECTIONROLE_NONE) {
// Making sure we are not using "passive" mode.
cricket::ConnectionRole role = transport_info->description.connection_role;
std::string dtls_role_str;
const bool success = cricket::ConnectionRoleToString(role, &dtls_role_str);
RTC_DCHECK(success);
InitAttrLine(kAttributeSetup, &os);
os << kSdpDelimiterColon << dtls_role_str;
AddLine(os.str(), message);
}
}
void BuildMediaLine(const cricket::MediaType media_type,
const ContentInfo* content_info,
const MediaContentDescription* media_desc,
std::string* message) {
rtc::StringBuilder os;
// RFC 4566
// m=<media> <port> <proto> <fmt>
// fmt is a list of payload type numbers that MAY be used in the session.
std::string type;
std::string fmt;
if (media_type == cricket::MEDIA_TYPE_AUDIO ||
media_type == cricket::MEDIA_TYPE_VIDEO) {
type = media_type == cricket::MEDIA_TYPE_AUDIO ? kMediaTypeAudio
: kMediaTypeVideo;
for (const cricket::Codec& codec : media_desc->codecs()) {
fmt.append(" ");
fmt.append(rtc::ToString(codec.id));
}
} else if (media_type == cricket::MEDIA_TYPE_DATA) {
type = kMediaTypeData;
const cricket::SctpDataContentDescription* sctp_data_desc =
media_desc->as_sctp();
if (sctp_data_desc) {
fmt.append(" ");
if (sctp_data_desc->use_sctpmap()) {
fmt.append(rtc::ToString(sctp_data_desc->port()));
} else {
fmt.append(kDefaultSctpmapProtocol);
}
} else {
RTC_DCHECK_NOTREACHED() << "Data description without SCTP";
}
} else if (media_type == cricket::MEDIA_TYPE_UNSUPPORTED) {
const UnsupportedContentDescription* unsupported_desc =
media_desc->as_unsupported();
type = unsupported_desc->media_type();
} else {
RTC_DCHECK_NOTREACHED();
}
// The fmt must never be empty. If no codecs are found, set the fmt attribute
// to 0.
if (fmt.empty()) {
fmt = " 0";
}
// The port number in the m line will be updated later when associated with
// the candidates.
//
// A port value of 0 indicates that the m= section is rejected.
// RFC 3264
// To reject an offered stream, the port number in the corresponding stream in
// the answer MUST be set to zero.
//
// However, the BUNDLE draft adds a new meaning to port zero, when used along
// with a=bundle-only.
std::string port = kDummyPort;
if (content_info->rejected || content_info->bundle_only) {
port = kMediaPortRejected;
} else if (!media_desc->connection_address().IsNil()) {
port = rtc::ToString(media_desc->connection_address().port());
}
// Add the m and c lines.
InitLine(kLineTypeMedia, type, &os);
os << " " << port << " " << media_desc->protocol() << fmt;
AddLine(os.str(), message);
}
void BuildMediaDescription(const ContentInfo* content_info,
const TransportInfo* transport_info,
const cricket::MediaType media_type,
const std::vector<Candidate>& candidates,
int msid_signaling,
std::string* message) {
RTC_DCHECK(message);
if (!content_info) {
return;
}
rtc::StringBuilder os;
const MediaContentDescription* media_desc = content_info->media_description();
RTC_DCHECK(media_desc);
// Add the m line.
BuildMediaLine(media_type, content_info, media_desc, message);
// Add the c line.
InitLine(kLineTypeConnection, kConnectionNettype, &os);
if (media_desc->connection_address().IsNil()) {
os << " " << kConnectionIpv4Addrtype << " " << kDummyAddress;
} else if (media_desc->connection_address().family() == AF_INET) {
os << " " << kConnectionIpv4Addrtype << " "
<< media_desc->connection_address().ipaddr().ToString();
} else if (media_desc->connection_address().family() == AF_INET6) {
os << " " << kConnectionIpv6Addrtype << " "
<< media_desc->connection_address().ipaddr().ToString();
} else {
os << " " << kConnectionIpv4Addrtype << " " << kDummyAddress;
}
AddLine(os.str(), message);
// RFC 4566
// b=AS:<bandwidth> or
// b=TIAS:<bandwidth>
int bandwidth = media_desc->bandwidth();
std::string bandwidth_type = media_desc->bandwidth_type();
if (bandwidth_type == kApplicationSpecificBandwidth && bandwidth >= 1000) {
InitLine(kLineTypeSessionBandwidth, bandwidth_type, &os);
bandwidth /= 1000;
os << kSdpDelimiterColon << bandwidth;
AddLine(os.str(), message);
} else if (bandwidth_type == kTransportSpecificBandwidth && bandwidth > 0) {
InitLine(kLineTypeSessionBandwidth, bandwidth_type, &os);
os << kSdpDelimiterColon << bandwidth;
AddLine(os.str(), message);
}
// Add the a=bundle-only line.
if (content_info->bundle_only) {
InitAttrLine(kAttributeBundleOnly, &os);
AddLine(os.str(), message);
}
// Add the a=rtcp line.
if (cricket::IsRtpProtocol(media_desc->protocol())) {
std::string rtcp_line = GetRtcpLine(candidates);
if (!rtcp_line.empty()) {
AddLine(rtcp_line, message);
}
}
// Build the a=candidate lines. We don't include ufrag and pwd in the
// candidates in the SDP to avoid redundancy.
BuildCandidate(candidates, false, message);
// Use the transport_info to build the media level ice-ufrag, ice-pwd
// and DTLS fingerprint and setup attributes.
if (transport_info) {
BuildIceUfragPwd(transport_info, message);
// draft-petithuguenin-mmusic-ice-attributes-level-03
BuildIceOptions(transport_info->description.transport_options, message);
// Also include the DTLS fingerprint and setup attribute if available.
BuildDtlsFingerprintSetup(transport_info, message);
}
// RFC 3388
// mid-attribute = "a=mid:" identification-tag
// identification-tag = token
// Use the content name as the mid identification-tag.
InitAttrLine(kAttributeMid, &os);
os << kSdpDelimiterColon << content_info->name;
AddLine(os.str(), message);
if (cricket::IsDtlsSctp(media_desc->protocol())) {
const cricket::SctpDataContentDescription* data_desc =
media_desc->as_sctp();
BuildSctpContentAttributes(message, data_desc);
} else if (cricket::IsRtpProtocol(media_desc->protocol())) {
BuildRtpContentAttributes(media_desc, media_type, msid_signaling, message);
}
}
void BuildRtpContentAttributes(const MediaContentDescription* media_desc,
const cricket::MediaType media_type,
int msid_signaling,
std::string* message) {
SimulcastSdpSerializer serializer;
rtc::StringBuilder os;
// RFC 8285
// a=extmap-allow-mixed
// The attribute MUST be either on session level or media level. We support
// responding on both levels, however, we don't respond on media level if it's
// set on session level.
if (media_desc->extmap_allow_mixed_enum() ==
MediaContentDescription::kMedia) {
InitAttrLine(kAttributeExtmapAllowMixed, &os);
AddLine(os.str(), message);
}
BuildRtpHeaderExtensions(media_desc->rtp_header_extensions(), message);
// RFC 3264
// a=sendrecv || a=sendonly || a=sendrecv || a=inactive
switch (media_desc->direction()) {
// Special case that for sdp purposes should be treated same as inactive.
case RtpTransceiverDirection::kStopped:
case RtpTransceiverDirection::kInactive:
InitAttrLine(kAttributeInactive, &os);
break;
case RtpTransceiverDirection::kSendOnly:
InitAttrLine(kAttributeSendOnly, &os);
break;
case RtpTransceiverDirection::kRecvOnly:
InitAttrLine(kAttributeRecvOnly, &os);
break;
case RtpTransceiverDirection::kSendRecv:
InitAttrLine(kAttributeSendRecv, &os);
break;
default:
RTC_DCHECK_NOTREACHED();
InitAttrLine(kAttributeSendRecv, &os);
break;
}
AddLine(os.str(), message);
// Specified in https://datatracker.ietf.org/doc/draft-ietf-mmusic-msid/16/
// a=msid:<msid-id> <msid-appdata>
// The msid-id is a 1*64 token char representing the media stream id, and the
// msid-appdata is a 1*64 token char representing the track id. There is a
// line for every media stream, with a special msid-id value of "-"
// representing no streams. The value of "msid-appdata" MUST be identical for
// all lines.
if (msid_signaling & cricket::kMsidSignalingMediaSection) {
const StreamParamsVec& streams = media_desc->streams();
if (streams.size() == 1u) {
const StreamParams& track = streams[0];
std::vector<std::string> stream_ids = track.stream_ids();
if (stream_ids.empty()) {
stream_ids.push_back(kNoStreamMsid);
}
for (const std::string& stream_id : stream_ids) {
InitAttrLine(kAttributeMsid, &os);
os << kSdpDelimiterColon << stream_id << kSdpDelimiterSpace << track.id;
AddLine(os.str(), message);
}
} else if (streams.size() > 1u) {
RTC_LOG(LS_WARNING)
<< "Trying to serialize Unified Plan SDP with more than "
"one track in a media section. Omitting 'a=msid'.";
}
}
// RFC 5761
// a=rtcp-mux
if (media_desc->rtcp_mux()) {
InitAttrLine(kAttributeRtcpMux, &os);
AddLine(os.str(), message);
}
// RFC 5506
// a=rtcp-rsize
if (media_desc->rtcp_reduced_size()) {
InitAttrLine(kAttributeRtcpReducedSize, &os);
AddLine(os.str(), message);
}
if (media_desc->conference_mode()) {
InitAttrLine(kAttributeXGoogleFlag, &os);
os << kSdpDelimiterColon << kValueConference;
AddLine(os.str(), message);
}
if (media_desc->remote_estimate()) {
InitAttrLine(kAttributeRtcpRemoteEstimate, &os);
AddLine(os.str(), message);
}
// RFC 4566
// a=rtpmap:<payload type> <encoding name>/<clock rate>
// [/<encodingparameters>]
BuildRtpmap(media_desc, media_type, message);
for (const StreamParams& track : media_desc->streams()) {
// Build the ssrc-group lines.
for (const SsrcGroup& ssrc_group : track.ssrc_groups) {
// RFC 5576
// a=ssrc-group:<semantics> <ssrc-id> ...
if (ssrc_group.ssrcs.empty()) {
continue;
}
InitAttrLine(kAttributeSsrcGroup, &os);
os << kSdpDelimiterColon << ssrc_group.semantics;
for (uint32_t ssrc : ssrc_group.ssrcs) {
os << kSdpDelimiterSpace << rtc::ToString(ssrc);
}
AddLine(os.str(), message);
}
// Build the ssrc lines for each ssrc.
for (uint32_t ssrc : track.ssrcs) {
// RFC 5576
// a=ssrc:<ssrc-id> cname:<value>
AddSsrcLine(ssrc, kSsrcAttributeCname, track.cname, message);
if (msid_signaling & cricket::kMsidSignalingSsrcAttribute) {
// draft-alvestrand-mmusic-msid-00
// a=ssrc:<ssrc-id> msid:identifier [appdata]
// The appdata consists of the "id" attribute of a MediaStreamTrack,
// which corresponds to the "id" attribute of StreamParams.
// Since a=ssrc msid signaling is used in Plan B SDP semantics, and
// multiple stream ids are not supported for Plan B, we are only adding
// a line for the first media stream id here.
const std::string& track_stream_id = track.first_stream_id();
// We use a special msid-id value of "-" to represent no streams,
// for Unified Plan compatibility. Plan B will always have a
// track_stream_id.
const std::string& stream_id =
track_stream_id.empty() ? kNoStreamMsid : track_stream_id;
InitAttrLine(kAttributeSsrc, &os);
os << kSdpDelimiterColon << ssrc << kSdpDelimiterSpace
<< kSsrcAttributeMsid << kSdpDelimiterColon << stream_id
<< kSdpDelimiterSpace << track.id;
AddLine(os.str(), message);
}
}
// Build the rid lines for each layer of the track
for (const RidDescription& rid_description : track.rids()) {
InitAttrLine(kAttributeRid, &os);
os << kSdpDelimiterColon
<< serializer.SerializeRidDescription(rid_description);
AddLine(os.str(), message);
}
}
for (const RidDescription& rid_description : media_desc->receive_rids()) {
InitAttrLine(kAttributeRid, &os);
os << kSdpDelimiterColon
<< serializer.SerializeRidDescription(rid_description);
AddLine(os.str(), message);
}
// Simulcast (a=simulcast)
// https://tools.ietf.org/html/draft-ietf-mmusic-sdp-simulcast-13#section-5.1
if (media_desc->HasSimulcast()) {
const auto& simulcast = media_desc->simulcast_description();
InitAttrLine(kAttributeSimulcast, &os);
os << kSdpDelimiterColon
<< serializer.SerializeSimulcastDescription(simulcast);
AddLine(os.str(), message);
}
}
void BuildRtpHeaderExtensions(const RtpHeaderExtensions& extensions,
std::string* message) {
rtc::StringBuilder os;
// RFC 8285
// a=extmap:<value>["/"<direction>] <URI> <extensionattributes>
// The definitions MUST be either all session level or all media level. This
// implementation uses all media level.
for (const RtpExtension& extension : extensions) {
InitAttrLine(kAttributeExtmap, &os);
os << kSdpDelimiterColon << extension.id;
if (extension.encrypt) {
os << kSdpDelimiterSpace << RtpExtension::kEncryptHeaderExtensionsUri;
}
os << kSdpDelimiterSpace << extension.uri;
AddLine(os.str(), message);
}
}
void WriteFmtpHeader(int payload_type, rtc::StringBuilder* os) {
// fmtp header: a=fmtp:`payload_type` <parameters>
// Add a=fmtp
InitAttrLine(kAttributeFmtp, os);
// Add :`payload_type`
*os << kSdpDelimiterColon << payload_type;
}
void WritePacketizationHeader(int payload_type, rtc::StringBuilder* os) {
// packetization header: a=packetization:`payload_type` <packetization_format>
// Add a=packetization
InitAttrLine(kAttributePacketization, os);
// Add :`payload_type`
*os << kSdpDelimiterColon << payload_type;
}
void WriteRtcpFbHeader(int payload_type, rtc::StringBuilder* os) {
// rtcp-fb header: a=rtcp-fb:`payload_type`
// <parameters>/<ccm <ccm_parameters>>
// Add a=rtcp-fb
InitAttrLine(kAttributeRtcpFb, os);
// Add :
*os << kSdpDelimiterColon;
if (payload_type == kWildcardPayloadType) {
*os << "*";
} else {
*os << payload_type;
}
}
void WriteFmtpParameter(absl::string_view parameter_name,
absl::string_view parameter_value,
rtc::StringBuilder* os) {
if (parameter_name.empty()) {
// RFC 2198 and RFC 4733 don't use key-value pairs.
*os << parameter_value;
} else {
// fmtp parameters: `parameter_name`=`parameter_value`
*os << parameter_name << kSdpDelimiterEqual << parameter_value;
}
}
bool IsFmtpParam(absl::string_view name) {
// RFC 4855, section 3 specifies the mapping of media format parameters to SDP
// parameters. Only ptime, maxptime, channels and rate are placed outside of
// the fmtp line. In WebRTC, channels and rate are already handled separately
// and thus not included in the CodecParameterMap.
return name != kCodecParamPTime && name != kCodecParamMaxPTime;
}
bool WriteFmtpParameters(const webrtc::CodecParameterMap& parameters,
rtc::StringBuilder* os) {
bool empty = true;
const char* delimiter = ""; // No delimiter before first parameter.
for (const auto& entry : parameters) {
const std::string& key = entry.first;
const std::string& value = entry.second;
if (IsFmtpParam(key)) {
*os << delimiter;
// A semicolon before each subsequent parameter.
delimiter = kSdpDelimiterSemicolon;
WriteFmtpParameter(key, value, os);
empty = false;
}
}
return !empty;
}
void AddFmtpLine(const cricket::Codec& codec, std::string* message) {
rtc::StringBuilder os;
WriteFmtpHeader(codec.id, &os);
os << kSdpDelimiterSpace;
// Create FMTP line and check that it's nonempty.
if (WriteFmtpParameters(codec.params, &os)) {
AddLine(os.str(), message);
}
return;
}
void AddPacketizationLine(const cricket::Codec& codec, std::string* message) {
if (!codec.packetization) {
return;
}
rtc::StringBuilder os;
WritePacketizationHeader(codec.id, &os);
os << " " << *codec.packetization;
AddLine(os.str(), message);
}
void AddRtcpFbLines(const cricket::Codec& codec, std::string* message) {
for (const cricket::FeedbackParam& param : codec.feedback_params.params()) {
rtc::StringBuilder os;
WriteRtcpFbHeader(codec.id, &os);
os << " " << param.id();
if (!param.param().empty()) {
os << " " << param.param();
}
AddLine(os.str(), message);
}
}
bool GetMinValue(const std::vector<int>& values, int* value) {
if (values.empty()) {
return false;
}
auto it = absl::c_min_element(values);
*value = *it;
return true;
}
bool GetParameter(const std::string& name,
const webrtc::CodecParameterMap& params,
int* value) {
std::map<std::string, std::string>::const_iterator found = params.find(name);
if (found == params.end()) {
return false;
}
if (!rtc::FromString(found->second, value)) {
return false;
}
return true;
}
void BuildRtpmap(const MediaContentDescription* media_desc,
const cricket::MediaType media_type,
std::string* message) {
RTC_DCHECK(message != NULL);
RTC_DCHECK(media_desc != NULL);
rtc::StringBuilder os;
if (media_type == cricket::MEDIA_TYPE_VIDEO) {
for (const cricket::Codec& codec : media_desc->codecs()) {
// RFC 4566
// a=rtpmap:<payload type> <encoding name>/<clock rate>
// [/<encodingparameters>]
if (codec.id != kWildcardPayloadType) {
InitAttrLine(kAttributeRtpmap, &os);
os << kSdpDelimiterColon << codec.id << " " << codec.name << "/"
<< cricket::kVideoCodecClockrate;
AddLine(os.str(), message);
}
AddPacketizationLine(codec, message);
AddRtcpFbLines(codec, message);
AddFmtpLine(codec, message);
}
} else if (media_type == cricket::MEDIA_TYPE_AUDIO) {
std::vector<int> ptimes;
std::vector<int> maxptimes;
int max_minptime = 0;
for (const cricket::Codec& codec : media_desc->codecs()) {
RTC_DCHECK(!codec.name.empty());
// RFC 4566
// a=rtpmap:<payload type> <encoding name>/<clock rate>
// [/<encodingparameters>]
InitAttrLine(kAttributeRtpmap, &os);
os << kSdpDelimiterColon << codec.id << " ";
os << codec.name << "/" << codec.clockrate;
if (codec.channels != 1) {
os << "/" << codec.channels;
}
AddLine(os.str(), message);
AddRtcpFbLines(codec, message);
AddFmtpLine(codec, message);
int minptime = 0;
if (GetParameter(kCodecParamMinPTime, codec.params, &minptime)) {
max_minptime = std::max(minptime, max_minptime);
}
int ptime;
if (GetParameter(kCodecParamPTime, codec.params, &ptime)) {
ptimes.push_back(ptime);
}
int maxptime;
if (GetParameter(kCodecParamMaxPTime, codec.params, &maxptime)) {
maxptimes.push_back(maxptime);
}
}
// Populate the maxptime attribute with the smallest maxptime of all codecs
// under the same m-line.
int min_maxptime = INT_MAX;
if (GetMinValue(maxptimes, &min_maxptime)) {
AddAttributeLine(kCodecParamMaxPTime, min_maxptime, message);
}
RTC_DCHECK_GE(min_maxptime, max_minptime);
// Populate the ptime attribute with the smallest ptime or the largest
// minptime, whichever is the largest, for all codecs under the same m-line.
int ptime = INT_MAX;
if (GetMinValue(ptimes, &ptime)) {
ptime = std::min(ptime, min_maxptime);
ptime = std::max(ptime, max_minptime);
AddAttributeLine(kCodecParamPTime, ptime, message);
}
}
}
void BuildCandidate(const std::vector<Candidate>& candidates,
bool include_ufrag,
std::string* message) {
rtc::StringBuilder os;
for (const Candidate& candidate : candidates) {
// RFC 5245
// a=candidate:<foundation> <component-id> <transport> <priority>
// <connection-address> <port> typ <candidate-types>
// [raddr <connection-address>] [rport <port>]
// *(SP extension-att-name SP extension-att-value)
std::string type;
// Map the cricket candidate type to "host" / "srflx" / "prflx" / "relay"
if (candidate.is_local()) {
type = kCandidateHost;
} else if (candidate.is_stun()) {
type = kCandidateSrflx;
} else if (candidate.is_relay()) {
type = kCandidateRelay;
} else if (candidate.is_prflx()) {
type = kCandidatePrflx;
// Peer reflexive candidate may be signaled for being removed.
} else {
RTC_DCHECK_NOTREACHED();
// Never write out candidates if we don't know the type.
continue;
}
InitAttrLine(kAttributeCandidate, &os);
os << kSdpDelimiterColon << candidate.foundation() << " "
<< candidate.component() << " " << candidate.protocol() << " "
<< candidate.priority() << " "
<< (candidate.address().ipaddr().IsNil()
? candidate.address().hostname()
: candidate.address().ipaddr().ToString())
<< " " << candidate.address().PortAsString() << " "
<< kAttributeCandidateTyp << " " << type << " ";
// Related address
if (!candidate.related_address().IsNil()) {
os << kAttributeCandidateRaddr << " "
<< candidate.related_address().ipaddr().ToString() << " "
<< kAttributeCandidateRport << " "
<< candidate.related_address().PortAsString() << " ";
}
// Note that we allow the tcptype to be missing, for backwards
// compatibility; the implementation treats this as a passive candidate.
// TODO(bugs.webrtc.org/11466): Treat a missing tcptype as an error?
if (candidate.protocol() == cricket::TCP_PROTOCOL_NAME &&
!candidate.tcptype().empty()) {
os << kTcpCandidateType << " " << candidate.tcptype() << " ";
}
// Extensions
os << kAttributeCandidateGeneration << " " << candidate.generation();
if (include_ufrag && !candidate.username().empty()) {
os << " " << kAttributeCandidateUfrag << " " << candidate.username();
}
if (candidate.network_id() > 0) {
os << " " << kAttributeCandidateNetworkId << " "
<< candidate.network_id();
}
if (candidate.network_cost() > 0) {
os << " " << kAttributeCandidateNetworkCost << " "
<< candidate.network_cost();
}
AddLine(os.str(), message);
}
}
void BuildIceOptions(const std::vector<std::string>& transport_options,
std::string* message) {
if (!transport_options.empty()) {
rtc::StringBuilder os;
InitAttrLine(kAttributeIceOption, &os);
os << kSdpDelimiterColon << transport_options[0];
for (size_t i = 1; i < transport_options.size(); ++i) {
os << kSdpDelimiterSpace << transport_options[i];
}
AddLine(os.str(), message);
}
}
bool ParseConnectionData(absl::string_view line,
rtc::SocketAddress* addr,
SdpParseError* error) {
// Parse the line from left to right.
std::string token;
std::string rightpart;
// RFC 4566
// c=<nettype> <addrtype> <connection-address>
// Skip the "c="
if (!rtc::tokenize_first(line, kSdpDelimiterEqualChar, &token, &rightpart)) {
return ParseFailed(line, "Failed to parse the network type.", error);
}
// Extract and verify the <nettype>
if (!rtc::tokenize_first(rightpart, kSdpDelimiterSpaceChar, &token,
&rightpart) ||
token != kConnectionNettype) {
return ParseFailed(line,
"Failed to parse the connection data. The network type "
"is not currently supported.",
error);
}
// Extract the "<addrtype>" and "<connection-address>".
if (!rtc::tokenize_first(rightpart, kSdpDelimiterSpaceChar, &token,
&rightpart)) {
return ParseFailed(line, "Failed to parse the address type.", error);
}
// The rightpart part should be the IP address without the slash which is used
// for multicast.
if (rightpart.find('/') != std::string::npos) {
return ParseFailed(line,
"Failed to parse the connection data. Multicast is not "
"currently supported.",
error);
}
addr->SetIP(rightpart);
// Verify that the addrtype matches the type of the parsed address.
if ((addr->family() == AF_INET && token != "IP4") ||
(addr->family() == AF_INET6 && token != "IP6")) {
addr->Clear();
return ParseFailed(
line,
"Failed to parse the connection data. The address type is mismatching.",
error);
}
return true;
}
bool ParseSessionDescription(absl::string_view message,
size_t* pos,
std::string* session_id,
std::string* session_version,
TransportDescription* session_td,
RtpHeaderExtensions* session_extmaps,
rtc::SocketAddress* connection_addr,
cricket::SessionDescription* desc,
SdpParseError* error) {
std::optional<absl::string_view> line;
desc->set_msid_signaling(cricket::kMsidSignalingNotUsed);
desc->set_extmap_allow_mixed(false);
// RFC 4566
// v= (protocol version)
line = GetLineWithType(message, pos, kLineTypeVersion);
if (!line) {
return ParseFailedExpectLine(message, *pos, kLineTypeVersion, std::string(),
error);
}
// RFC 4566
// o=<username> <sess-id> <sess-version> <nettype> <addrtype>
// <unicast-address>
line = GetLineWithType(message, pos, kLineTypeOrigin);
if (!line) {
return ParseFailedExpectLine(message, *pos, kLineTypeOrigin, std::string(),
error);
}
std::vector<absl::string_view> fields =
rtc::split(line->substr(kLinePrefixLength), kSdpDelimiterSpaceChar);
const size_t expected_fields = 6;
if (fields.size() != expected_fields) {
return ParseFailedExpectFieldNum(*line, expected_fields, error);
}
*session_id = std::string(fields[1]);
*session_version = std::string(fields[2]);
// RFC 4566
// s= (session name)
line = GetLineWithType(message, pos, kLineTypeSessionName);
if (!line) {
return ParseFailedExpectLine(message, *pos, kLineTypeSessionName,
std::string(), error);
}
// optional lines
// Those are the optional lines, so shouldn't return false if not present.
// RFC 4566
// i=* (session information)
GetLineWithType(message, pos, kLineTypeSessionInfo);
// RFC 4566
// u=* (URI of description)
GetLineWithType(message, pos, kLineTypeSessionUri);
// RFC 4566
// e=* (email address)
GetLineWithType(message, pos, kLineTypeSessionEmail);
// RFC 4566
// p=* (phone number)
GetLineWithType(message, pos, kLineTypeSessionPhone);
// RFC 4566
// c=* (connection information -- not required if included in
// all media)
if (std::optional<absl::string_view> cline =
GetLineWithType(message, pos, kLineTypeConnection);
cline.has_value()) {
if (!ParseConnectionData(*cline, connection_addr, error)) {
return false;
}
}
// RFC 4566
// b=* (zero or more bandwidth information lines)
while (GetLineWithType(message, pos, kLineTypeSessionBandwidth).has_value()) {
// By pass zero or more b lines.
}
// RFC 4566
// One or more time descriptions ("t=" and "r=" lines; see below)
// t= (time the session is active)
// r=* (zero or more repeat times)
// Ensure there's at least one time description
if (!GetLineWithType(message, pos, kLineTypeTiming).has_value()) {
return ParseFailedExpectLine(message, *pos, kLineTypeTiming, std::string(),
error);
}
while (GetLineWithType(message, pos, kLineTypeRepeatTimes).has_value()) {
// By pass zero or more r lines.
}
// Go through the rest of the time descriptions
while (GetLineWithType(message, pos, kLineTypeTiming).has_value()) {
while (GetLineWithType(message, pos, kLineTypeRepeatTimes).has_value()) {
// By pass zero or more r lines.
}
}
// RFC 4566
// z=* (time zone adjustments)
GetLineWithType(message, pos, kLineTypeTimeZone);
// RFC 4566
// k=* (encryption key)
GetLineWithType(message, pos, kLineTypeEncryptionKey);
// RFC 4566
// a=* (zero or more session attribute lines)
while (std::optional<absl::string_view> aline =
GetLineWithType(message, pos, kLineTypeAttributes)) {
if (HasAttribute(*aline, kAttributeGroup)) {
if (!ParseGroupAttribute(*aline, desc, error)) {
return false;
}
} else if (HasAttribute(*aline, kAttributeIceUfrag)) {
if (!GetValue(*aline, kAttributeIceUfrag, &(session_td->ice_ufrag),
error)) {
return false;
}
} else if (HasAttribute(*aline, kAttributeIcePwd)) {
if (!GetValue(*aline, kAttributeIcePwd, &(session_td->ice_pwd), error)) {
return false;
}
} else if (HasAttribute(*aline, kAttributeIceLite)) {
session_td->ice_mode = cricket::ICEMODE_LITE;
} else if (HasAttribute(*aline, kAttributeIceOption)) {
if (!ParseIceOptions(*aline, &(session_td->transport_options), error)) {
return false;
}
} else if (HasAttribute(*aline, kAttributeFingerprint)) {
if (session_td->identity_fingerprint.get()) {
return ParseFailed(
*aline,
"Can't have multiple fingerprint attributes at the same level.",
error);
}
std::unique_ptr<rtc::SSLFingerprint> fingerprint;
if (!ParseFingerprintAttribute(*aline, &fingerprint, error)) {
return false;
}
session_td->identity_fingerprint = std::move(fingerprint);
} else if (HasAttribute(*aline, kAttributeSetup)) {
if (!ParseDtlsSetup(*aline, &(session_td->connection_role), error)) {
return false;
}
} else if (HasAttribute(*aline, kAttributeMsidSemantics)) {
std::string semantics;
if (!GetValue(*aline, kAttributeMsidSemantics, &semantics, error)) {
return false;
}
if (CaseInsensitiveFind(semantics, kMediaStreamSemantic)) {
desc->set_msid_signaling(cricket::kMsidSignalingSemantic);
}
} else if (HasAttribute(*aline, kAttributeExtmapAllowMixed)) {
desc->set_extmap_allow_mixed(true);
} else if (HasAttribute(*aline, kAttributeExtmap)) {
RtpExtension extmap;
if (!ParseExtmap(*aline, &extmap, error)) {
return false;
}
session_extmaps->push_back(extmap);
}
}
return true;
}
bool ParseGroupAttribute(absl::string_view line,
cricket::SessionDescription* desc,
SdpParseError* error) {
RTC_DCHECK(desc != NULL);
// RFC 5888 and draft-holmberg-mmusic-sdp-bundle-negotiation-00
// a=group:BUNDLE video voice
std::vector<absl::string_view> fields =
rtc::split(line.substr(kLinePrefixLength), kSdpDelimiterSpaceChar);
std::string semantics;
if (!GetValue(fields[0], kAttributeGroup, &semantics, error)) {
return false;
}
cricket::ContentGroup group(semantics);
for (size_t i = 1; i < fields.size(); ++i) {
group.AddContentName(fields[i]);
}
desc->AddGroup(group);
return true;
}
static bool ParseFingerprintAttribute(
absl::string_view line,
std::unique_ptr<rtc::SSLFingerprint>* fingerprint,
SdpParseError* error) {
std::vector<absl::string_view> fields =
rtc::split(line.substr(kLinePrefixLength), kSdpDelimiterSpaceChar);
const size_t expected_fields = 2;
if (fields.size() != expected_fields) {
return ParseFailedExpectFieldNum(line, expected_fields, error);
}
// The first field here is "fingerprint:<hash>.
std::string algorithm;
if (!GetValue(fields[0], kAttributeFingerprint, &algorithm, error)) {
return false;
}
// Downcase the algorithm. Note that we don't need to downcase the
// fingerprint because hex_decode can handle upper-case.
absl::c_transform(algorithm, algorithm.begin(), ::tolower);
// The second field is the digest value. De-hexify it.
*fingerprint =
rtc::SSLFingerprint::CreateUniqueFromRfc4572(algorithm, fields[1]);
if (!*fingerprint) {
return ParseFailed(line, "Failed to create fingerprint from the digest.",
error);
}
return true;
}
static bool ParseDtlsSetup(absl::string_view line,
cricket::ConnectionRole* role_ptr,
SdpParseError* error) {
// setup-attr = "a=setup:" role
// role = "active" / "passive" / "actpass" / "holdconn"
std::vector<absl::string_view> fields =
rtc::split(line.substr(kLinePrefixLength), kSdpDelimiterColonChar);
const size_t expected_fields = 2;
if (fields.size() != expected_fields) {
return ParseFailedExpectFieldNum(line, expected_fields, error);
}
if (std::optional<cricket::ConnectionRole> role =
cricket::StringToConnectionRole(fields[1]);
role.has_value()) {
*role_ptr = *role;
return true;
}
return ParseFailed(line, "Invalid attribute value.", error);
}
static bool ParseMsidAttribute(absl::string_view line,
std::vector<std::string>* stream_ids,
std::string* track_id,
SdpParseError* error) {
// https://datatracker.ietf.org/doc/rfc8830/
// a=msid:<msid-value>
// msid-value = msid-id [ SP msid-appdata ]
// msid-id = 1*64token-char ; see RFC 4566
// msid-appdata = 1*64token-char ; see RFC 4566
// Note that JSEP stipulates not sending msid-appdata so
// a=msid:<stream id> <track id>
// is supported for backward compability reasons only.
// RFC 8830 section 2 states that duplicate a=msid:stream track is illegal.
std::vector<std::string> fields;
size_t num_fields = rtc::tokenize(line.substr(kLinePrefixLength),
kSdpDelimiterSpaceChar, &fields);
if (num_fields < 1 || num_fields > 2) {
return ParseFailed(line, "Expected a stream ID and optionally a track ID",
error);
}
if (num_fields == 1) {
if (line.back() == kSdpDelimiterSpaceChar) {
return ParseFailed(line, "Missing track ID in msid attribute.", error);
}
if (!track_id->empty()) {
fields.push_back(*track_id);
} else {
// Ending with an empty string track will cause a random track id
// to be generated later in the process.
fields.push_back("");
}
}
RTC_DCHECK_EQ(fields.size(), 2);
// All track ids should be the same within an m section in a Unified Plan SDP.
if (!track_id->empty() && track_id->compare(fields[1]) != 0) {
return ParseFailed(
line, "Two different track IDs in msid attribute in one m= section",
error);
}
*track_id = fields[1];
// msid:<msid-id>
std::string new_stream_id;
if (!GetValue(fields[0], kAttributeMsid, &new_stream_id, error)) {
return false;
}
if (new_stream_id.empty()) {
return ParseFailed(line, "Missing stream ID in msid attribute.", error);
}
// The special value "-" indicates "no MediaStream".
if (new_stream_id.compare(kNoStreamMsid) != 0 &&
!absl::c_any_of(*stream_ids,
[&new_stream_id](const std::string& existing_stream_id) {
return new_stream_id == existing_stream_id;
})) {
stream_ids->push_back(new_stream_id);
}
return true;
}
static void RemoveInvalidRidDescriptions(const std::vector<int>& payload_types,
std::vector<RidDescription>* rids) {
RTC_DCHECK(rids);
std::set<std::string> to_remove;
std::set<std::string> unique_rids;
// Check the rids to see which ones should be removed.
for (RidDescription& rid : *rids) {
// In the case of a duplicate, the entire "a=rid" line, and all "a=rid"
// lines with rid-ids that duplicate this line, are discarded and MUST NOT
// be included in the SDP Answer.
auto pair = unique_rids.insert(rid.rid);
// Insert will "fail" if element already exists.
if (!pair.second) {
to_remove.insert(rid.rid);
continue;
}
// If the "a=rid" line contains a "pt=", the list of payload types
// is verified against the list of valid payload types for the media
// section (that is, those listed on the "m=" line). Any PT missing
// from the "m=" line is discarded from the set of values in the
// "pt=". If no values are left in the "pt=" parameter after this
// processing, then the "a=rid" line is discarded.
if (rid.payload_types.empty()) {
// If formats were not specified, rid should not be removed.
continue;
}
// Note: Spec does not mention how to handle duplicate formats.
// Media section does not handle duplicates either.
std::set<int> removed_formats;
for (int payload_type : rid.payload_types) {
if (!absl::c_linear_search(payload_types, payload_type)) {
removed_formats.insert(payload_type);
}
}
rid.payload_types.erase(
std::remove_if(rid.payload_types.begin(), rid.payload_types.end(),
[&removed_formats](int format) {
return removed_formats.count(format) > 0;
}),
rid.payload_types.end());
// If all formats were removed then remove the rid alogether.
if (rid.payload_types.empty()) {
to_remove.insert(rid.rid);
}
}
// Remove every rid description that appears in the to_remove list.
if (!to_remove.empty()) {
rids->erase(std::remove_if(rids->begin(), rids->end(),
[&to_remove](const RidDescription& rid) {
return to_remove.count(rid.rid) > 0;
}),
rids->end());
}
}
// Create a new list (because SimulcastLayerList is immutable) without any
// layers that have a rid in the to_remove list.
// If a group of alternatives is empty after removing layers, the group should
// be removed altogether.
static SimulcastLayerList RemoveRidsFromSimulcastLayerList(
const std::set<std::string>& to_remove,
const SimulcastLayerList& layers) {
SimulcastLayerList result;
for (const std::vector<SimulcastLayer>& vector : layers) {
std::vector<SimulcastLayer> new_layers;
for (const SimulcastLayer& layer : vector) {
if (to_remove.find(layer.rid) == to_remove.end()) {
new_layers.push_back(layer);
}
}
// If all layers were removed, do not add an entry.
if (!new_layers.empty()) {
result.AddLayerWithAlternatives(new_layers);
}
}
return result;
}
// Will remove Simulcast Layers if:
// 1. They appear in both send and receive directions.
// 2. They do not appear in the list of `valid_rids`.
static void RemoveInvalidRidsFromSimulcast(
const std::vector<RidDescription>& valid_rids,
SimulcastDescription* simulcast) {
RTC_DCHECK(simulcast);
std::set<std::string> to_remove;
std::vector<SimulcastLayer> all_send_layers =
simulcast->send_layers().GetAllLayers();
std::vector<SimulcastLayer> all_receive_layers =
simulcast->receive_layers().GetAllLayers();
// If a rid appears in both send and receive directions, remove it from both.
// This algorithm runs in O(n^2) time, but for small n (as is the case with
// simulcast layers) it should still perform well.
for (const SimulcastLayer& send_layer : all_send_layers) {
if (absl::c_any_of(all_receive_layers,
[&send_layer](const SimulcastLayer& layer) {
return layer.rid == send_layer.rid;
})) {
to_remove.insert(send_layer.rid);
}
}
// Add any rid that is not in the valid list to the remove set.
for (const SimulcastLayer& send_layer : all_send_layers) {
if (absl::c_none_of(valid_rids, [&send_layer](const RidDescription& rid) {
return send_layer.rid == rid.rid &&
rid.direction == cricket::RidDirection::kSend;
})) {
to_remove.insert(send_layer.rid);
}
}
// Add any rid that is not in the valid list to the remove set.
for (const SimulcastLayer& receive_layer : all_receive_layers) {
if (absl::c_none_of(
valid_rids, [&receive_layer](const RidDescription& rid) {
return receive_layer.rid == rid.rid &&
rid.direction == cricket::RidDirection::kReceive;
})) {
to_remove.insert(receive_layer.rid);
}
}
simulcast->send_layers() =
RemoveRidsFromSimulcastLayerList(to_remove, simulcast->send_layers());
simulcast->receive_layers() =
RemoveRidsFromSimulcastLayerList(to_remove, simulcast->receive_layers());
}
// RFC 3551
// PT encoding media type clock rate channels
// name (Hz)
// 0 PCMU A 8,000 1
// 1 reserved A
// 2 reserved A
// 3 GSM A 8,000 1
// 4 G723 A 8,000 1
// 5 DVI4 A 8,000 1
// 6 DVI4 A 16,000 1
// 7 LPC A 8,000 1
// 8 PCMA A 8,000 1
// 9 G722 A 8,000 1
// 10 L16 A 44,100 2
// 11 L16 A 44,100 1
// 12 QCELP A 8,000 1
// 13 CN A 8,000 1
// 14 MPA A 90,000 (see text)
// 15 G728 A 8,000 1
// 16 DVI4 A 11,025 1
// 17 DVI4 A 22,050 1
// 18 G729 A 8,000 1
struct StaticPayloadAudioCodec {
const char* name;
int clockrate;
size_t channels;
};
static const StaticPayloadAudioCodec kStaticPayloadAudioCodecs[] = {
{"PCMU", 8000, 1}, {"reserved", 0, 0}, {"reserved", 0, 0},
{"GSM", 8000, 1}, {"G723", 8000, 1}, {"DVI4", 8000, 1},
{"DVI4", 16000, 1}, {"LPC", 8000, 1}, {"PCMA", 8000, 1},
{"G722", 8000, 1}, {"L16", 44100, 2}, {"L16", 44100, 1},
{"QCELP", 8000, 1}, {"CN", 8000, 1}, {"MPA", 90000, 1},
{"G728", 8000, 1}, {"DVI4", 11025, 1}, {"DVI4", 22050, 1},
{"G729", 8000, 1},
};
void MaybeCreateStaticPayloadAudioCodecs(const std::vector<int>& fmts,
MediaContentDescription* media_desc) {
if (!media_desc) {
return;
}
RTC_DCHECK(media_desc->codecs().empty());
for (int payload_type : fmts) {
if (!media_desc->HasCodec(payload_type) && payload_type >= 0 &&
static_cast<uint32_t>(payload_type) <
arraysize(kStaticPayloadAudioCodecs)) {
std::string encoding_name = kStaticPayloadAudioCodecs[payload_type].name;
int clock_rate = kStaticPayloadAudioCodecs[payload_type].clockrate;
size_t channels = kStaticPayloadAudioCodecs[payload_type].channels;
media_desc->AddCodec(cricket::CreateAudioCodec(
payload_type, encoding_name, clock_rate, channels));
}
}
}
static void BackfillCodecParameters(std::vector<cricket::Codec>& codecs) {
for (auto& codec : codecs) {
std::string unused_value;
if (absl::EqualsIgnoreCase(cricket::kVp9CodecName, codec.name)) {
// https://datatracker.ietf.org/doc/html/draft-ietf-payload-vp9#section-6
// profile-id defaults to "0"
if (!codec.GetParam(cricket::kVP9ProfileId, &unused_value)) {
codec.SetParam(cricket::kVP9ProfileId, "0");
}
} else if (absl::EqualsIgnoreCase(cricket::kH264CodecName, codec.name)) {
// https://www.rfc-editor.org/rfc/rfc6184#section-6.2
// packetization-mode defaults to "0"
if (!codec.GetParam(cricket::kH264FmtpPacketizationMode, &unused_value)) {
codec.SetParam(cricket::kH264FmtpPacketizationMode, "0");
}
} else if (absl::EqualsIgnoreCase(cricket::kAv1CodecName, codec.name)) {
// https://aomediacodec.github.io/av1-rtp-spec/#72-sdp-parameters
if (!codec.GetParam(cricket::kAv1FmtpProfile, &unused_value)) {
codec.SetParam(cricket::kAv1FmtpProfile, "0");
}
if (!codec.GetParam(cricket::kAv1FmtpLevelIdx, &unused_value)) {
codec.SetParam(cricket::kAv1FmtpLevelIdx, "5");
}
if (!codec.GetParam(cricket::kAv1FmtpTier, &unused_value)) {
codec.SetParam(cricket::kAv1FmtpTier, "0");
}
} else if (absl::EqualsIgnoreCase(cricket::kH265CodecName, codec.name)) {
// https://datatracker.ietf.org/doc/html/draft-aboba-avtcore-hevc-webrtc
if (!codec.GetParam(cricket::kH265FmtpLevelId, &unused_value)) {
codec.SetParam(cricket::kH265FmtpLevelId, "93");
}
if (!codec.GetParam(cricket::kH265FmtpTxMode, &unused_value)) {
codec.SetParam(cricket::kH265FmtpTxMode, "SRST");
}
}
}
}
static std::unique_ptr<MediaContentDescription> ParseContentDescription(
absl::string_view message,
const cricket::MediaType media_type,
int mline_index,
absl::string_view protocol,
const std::vector<int>& payload_types,
size_t* pos,
std::string* content_name,
bool* bundle_only,
int* msid_signaling,
TransportDescription* transport,
std::vector<std::unique_ptr<JsepIceCandidate>>* candidates,
SdpParseError* error) {
std::unique_ptr<MediaContentDescription> media_desc;
if (media_type == cricket::MediaType::MEDIA_TYPE_AUDIO) {
media_desc = std::make_unique<AudioContentDescription>();
} else if (media_type == cricket::MediaType::MEDIA_TYPE_VIDEO) {
media_desc = std::make_unique<VideoContentDescription>();
} else {
RTC_DCHECK_NOTREACHED();
return nullptr;
}
media_desc->set_extmap_allow_mixed_enum(MediaContentDescription::kNo);
if (!ParseContent(message, media_type, mline_index, protocol, payload_types,
pos, content_name, bundle_only, msid_signaling,
media_desc.get(), transport, candidates, error)) {
return nullptr;
}
// Sort the codecs according to the m-line fmt list.
std::unordered_map<int, int> payload_type_preferences;
// "size + 1" so that the lowest preference payload type has a preference of
// 1, which is greater than the default (0) for payload types not in the fmt
// list.
int preference = static_cast<int>(payload_types.size() + 1);
for (int pt : payload_types) {
payload_type_preferences[pt] = preference--;
}
std::vector<cricket::Codec> codecs = media_desc->codecs();
absl::c_sort(codecs, [&payload_type_preferences](const cricket::Codec& a,
const cricket::Codec& b) {
return payload_type_preferences[a.id] > payload_type_preferences[b.id];
});
// Backfill any default parameters.
BackfillCodecParameters(codecs);
media_desc->set_codecs(codecs);
return media_desc;
}
bool HasDuplicateMsidLines(cricket::SessionDescription* desc) {
std::set<std::pair<std::string, std::string>> seen_msids;
for (const cricket::ContentInfo& content : desc->contents()) {
for (const cricket::StreamParams& stream :
content.media_description()->streams()) {
auto msid = std::pair(stream.first_stream_id(), stream.id);
if (seen_msids.find(msid) != seen_msids.end()) {
return true;
}
seen_msids.insert(std::move(msid));
}
}
return false;
}
bool ParseMediaDescription(
absl::string_view message,
const TransportDescription& session_td,
const RtpHeaderExtensions& session_extmaps,
size_t* pos,
const rtc::SocketAddress& session_connection_addr,
cricket::SessionDescription* desc,
std::vector<std::unique_ptr<JsepIceCandidate>>* candidates,
SdpParseError* error) {
RTC_DCHECK(desc != NULL);
int mline_index = -1;
int msid_signaling = desc->msid_signaling();
// Zero or more media descriptions
// RFC 4566
// m=<media> <port> <proto> <fmt>
while (std::optional<absl::string_view> mline =
GetLineWithType(message, pos, kLineTypeMedia)) {
++mline_index;
std::vector<absl::string_view> fields =
rtc::split(mline->substr(kLinePrefixLength), kSdpDelimiterSpaceChar);
const size_t expected_min_fields = 4;
if (fields.size() < expected_min_fields) {
return ParseFailedExpectMinFieldNum(*mline, expected_min_fields, error);
}
bool port_rejected = false;
// RFC 3264
// To reject an offered stream, the port number in the corresponding stream
// in the answer MUST be set to zero.
if (fields[1] == kMediaPortRejected) {
port_rejected = true;
}
int port = 0;
if (!rtc::FromString<int>(fields[1], &port) || !IsValidPort(port)) {
return ParseFailed(*mline, "The port number is invalid", error);
}
absl::string_view protocol = fields[2];
// <fmt>
std::vector<int> payload_types;
if (cricket::IsRtpProtocol(protocol)) {
for (size_t j = 3; j < fields.size(); ++j) {
int pl = 0;
if (!GetPayloadTypeFromString(*mline, fields[j], &pl, error)) {
return false;
}
payload_types.push_back(pl);
}
}
// Make a temporary TransportDescription based on `session_td`.
// Some of this gets overwritten by ParseContent.
TransportDescription transport(
session_td.transport_options, session_td.ice_ufrag, session_td.ice_pwd,
session_td.ice_mode, session_td.connection_role,
session_td.identity_fingerprint.get());
std::unique_ptr<MediaContentDescription> content;
std::string content_name;
bool bundle_only = false;
int section_msid_signaling = cricket::kMsidSignalingNotUsed;
absl::string_view media_type = fields[0];
if ((media_type == kMediaTypeVideo || media_type == kMediaTypeAudio) &&
!cricket::IsRtpProtocol(protocol)) {
return ParseFailed(*mline, "Unsupported protocol for media type", error);
}
if (media_type == kMediaTypeVideo) {
content = ParseContentDescription(
message, cricket::MEDIA_TYPE_VIDEO, mline_index, protocol,
payload_types, pos, &content_name, &bundle_only,
&section_msid_signaling, &transport, candidates, error);
} else if (media_type == kMediaTypeAudio) {
content = ParseContentDescription(
message, cricket::MEDIA_TYPE_AUDIO, mline_index, protocol,
payload_types, pos, &content_name, &bundle_only,
&section_msid_signaling, &transport, candidates, error);
} else if (media_type == kMediaTypeData && cricket::IsDtlsSctp(protocol)) {
// The draft-03 format is:
// m=application <port> DTLS/SCTP <sctp-port>...
// use_sctpmap should be false.
// The draft-26 format is:
// m=application <port> UDP/DTLS/SCTP webrtc-datachannel
// use_sctpmap should be false.
auto data_desc = std::make_unique<SctpDataContentDescription>();
// Default max message size is 64K
// according to draft-ietf-mmusic-sctp-sdp-26
data_desc->set_max_message_size(kDefaultSctpMaxMessageSize);
int p;
if (rtc::FromString(fields[3], &p)) {
data_desc->set_port(p);
} else if (fields[3] == kDefaultSctpmapProtocol) {
data_desc->set_use_sctpmap(false);
}
if (!ParseContent(message, cricket::MEDIA_TYPE_DATA, mline_index,
protocol, payload_types, pos, &content_name,
&bundle_only, &section_msid_signaling, data_desc.get(),
&transport, candidates, error)) {
return false;
}
data_desc->set_protocol(protocol);
content = std::move(data_desc);
} else {
RTC_LOG(LS_WARNING) << "Unsupported media type: " << *mline;
auto unsupported_desc =
std::make_unique<UnsupportedContentDescription>(media_type);
if (!ParseContent(message, cricket::MEDIA_TYPE_UNSUPPORTED, mline_index,
protocol, payload_types, pos, &content_name,
&bundle_only, &section_msid_signaling,
unsupported_desc.get(), &transport, candidates,
error)) {
return false;
}
unsupported_desc->set_protocol(protocol);
content = std::move(unsupported_desc);
}
if (!content.get()) {
// ParseContentDescription returns NULL if failed.
return false;
}
msid_signaling |= section_msid_signaling;
bool content_rejected = false;
// A port of 0 is not interpreted as a rejected m= section when it's
// used along with a=bundle-only.
if (bundle_only) {
if (!port_rejected) {
// Usage of bundle-only with a nonzero port is unspecified. So just
// ignore bundle-only if we see this.
bundle_only = false;
RTC_LOG(LS_WARNING)
<< "a=bundle-only attribute observed with a nonzero "
"port; this usage is unspecified so the attribute is being "
"ignored.";
}
} else {
// If not using bundle-only, interpret port 0 in the normal way; the m=
// section is being rejected.
content_rejected = port_rejected;
}
if (content->as_unsupported()) {
content_rejected = true;
} else if (cricket::IsRtpProtocol(protocol) && !content->as_sctp()) {
content->set_protocol(std::string(protocol));
// Set the extmap.
if (!session_extmaps.empty() &&
!content->rtp_header_extensions().empty()) {
return ParseFailed("",
"The a=extmap MUST be either all session level or "
"all media level.",
error);
}
for (size_t i = 0; i < session_extmaps.size(); ++i) {
content->AddRtpHeaderExtension(session_extmaps[i]);
}
} else if (content->as_sctp()) {
// Do nothing, it's OK
} else {
RTC_LOG(LS_WARNING) << "Parse failed with unknown protocol " << protocol;
return false;
}
// Use the session level connection address if the media level addresses are
// not specified.
rtc::SocketAddress address;
address = content->connection_address().IsNil()
? session_connection_addr
: content->connection_address();
address.SetPort(port);
content->set_connection_address(address);
desc->AddContent(content_name,
cricket::IsDtlsSctp(protocol) ? MediaProtocolType::kSctp
: MediaProtocolType::kRtp,
content_rejected, bundle_only, std::move(content));
// Create TransportInfo with the media level "ice-pwd" and "ice-ufrag".
desc->AddTransportInfo(TransportInfo(content_name, transport));
}
// Apply whole-description sanity checks
if (HasDuplicateMsidLines(desc)) {
ParseFailed(message, *pos, "Duplicate a=msid lines detected", error);
return false;
}
desc->set_msid_signaling(msid_signaling);
size_t end_of_message = message.size();
if (mline_index == -1 && *pos != end_of_message) {
ParseFailed(message, *pos, "Expects m line.", error);
return false;
}
return true;
}
void AddParameters(const webrtc::CodecParameterMap& parameters,
cricket::Codec* codec) {
for (const auto& entry : parameters) {
const std::string& key = entry.first;
const std::string& value = entry.second;
codec->SetParam(key, value);
}
}
void AddFeedbackParameter(const cricket::FeedbackParam& feedback_param,
cricket::Codec* codec) {
codec->AddFeedbackParam(feedback_param);
}
void AddFeedbackParameters(const cricket::FeedbackParams& feedback_params,
cricket::Codec* codec) {
for (const cricket::FeedbackParam& param : feedback_params.params()) {
codec->AddFeedbackParam(param);
}
}
// Gets the current codec setting associated with `payload_type`. If there
// is no Codec associated with that payload type it returns an empty codec
// with that payload type.
cricket::Codec GetCodecWithPayloadType(
cricket::MediaType type,
const std::vector<cricket::Codec>& codecs,
int payload_type) {
const cricket::Codec* codec = FindCodecById(codecs, payload_type);
if (codec)
return *codec;
// Return empty codec with `payload_type`.
if (type == cricket::MEDIA_TYPE_AUDIO) {
return cricket::CreateAudioCodec(payload_type, "", 0, 0);
} else {
return cricket::CreateVideoCodec(payload_type, "");
}
}
// Updates or creates a new codec entry in the media description.
void AddOrReplaceCodec(MediaContentDescription* content_desc,
const cricket::Codec& codec) {
std::vector<cricket::Codec> codecs = content_desc->codecs();
bool found = false;
for (cricket::Codec& existing_codec : codecs) {
if (codec.id == existing_codec.id) {
// Overwrite existing codec with the new codec.
existing_codec = codec;
found = true;
break;
}
}
if (!found) {
content_desc->AddCodec(codec);
return;
}
content_desc->set_codecs(codecs);
}
// Adds or updates existing codec corresponding to `payload_type` according
// to `parameters`.
void UpdateCodec(MediaContentDescription* content_desc,
int payload_type,
const webrtc::CodecParameterMap& parameters) {
// Codec might already have been populated (from rtpmap).
cricket::Codec new_codec = GetCodecWithPayloadType(
content_desc->type(), content_desc->codecs(), payload_type);
AddParameters(parameters, &new_codec);
AddOrReplaceCodec(content_desc, new_codec);
}
// Adds or updates existing codec corresponding to `payload_type` according
// to `feedback_param`.
void UpdateCodec(MediaContentDescription* content_desc,
int payload_type,
const cricket::FeedbackParam& feedback_param) {
// Codec might already have been populated (from rtpmap).
cricket::Codec new_codec = GetCodecWithPayloadType(
content_desc->type(), content_desc->codecs(), payload_type);
AddFeedbackParameter(feedback_param, &new_codec);
AddOrReplaceCodec(content_desc, new_codec);
}
// Adds or updates existing video codec corresponding to `payload_type`
// according to `packetization`.
void UpdateVideoCodecPacketization(MediaContentDescription* desc,
int payload_type,
absl::string_view packetization) {
if (packetization != cricket::kPacketizationParamRaw) {
// Ignore unsupported packetization attribute.
return;
}
// Codec might already have been populated (from rtpmap).
cricket::Codec codec =
GetCodecWithPayloadType(desc->type(), desc->codecs(), payload_type);
codec.packetization = std::string(packetization);
AddOrReplaceCodec(desc, codec);
}
std::optional<cricket::Codec> PopWildcardCodec(
std::vector<cricket::Codec>* codecs) {
RTC_DCHECK(codecs);
for (auto iter = codecs->begin(); iter != codecs->end(); ++iter) {
if (iter->id == kWildcardPayloadType) {
cricket::Codec wildcard_codec = *iter;
codecs->erase(iter);
return wildcard_codec;
}
}
return std::nullopt;
}
void UpdateFromWildcardCodecs(cricket::MediaContentDescription* desc) {
RTC_DCHECK(desc);
auto codecs = desc->codecs();
std::optional<cricket::Codec> wildcard_codec = PopWildcardCodec(&codecs);
if (!wildcard_codec) {
return;
}
for (auto& codec : codecs) {
AddFeedbackParameters(wildcard_codec->feedback_params, &codec);
}
desc->set_codecs(codecs);
}
void AddAudioAttribute(const std::string& name,
absl::string_view value,
MediaContentDescription* desc) {
RTC_DCHECK(desc);
if (value.empty()) {
return;
}
std::vector<cricket::Codec> codecs = desc->codecs();
for (cricket::Codec& codec : codecs) {
codec.params[name] = std::string(value);
}
desc->set_codecs(codecs);
}
bool ParseContent(absl::string_view message,
const cricket::MediaType media_type,
int mline_index,
absl::string_view protocol,
const std::vector<int>& payload_types,
size_t* pos,
std::string* content_name,
bool* bundle_only,
int* msid_signaling,
MediaContentDescription* media_desc,
TransportDescription* transport,
std::vector<std::unique_ptr<JsepIceCandidate>>* candidates,
SdpParseError* error) {
RTC_DCHECK(media_desc != NULL);
RTC_DCHECK(content_name != NULL);
RTC_DCHECK(transport != NULL);
if (media_type == cricket::MEDIA_TYPE_AUDIO) {
MaybeCreateStaticPayloadAudioCodecs(payload_types, media_desc);
}
// The media level "ice-ufrag" and "ice-pwd".
// The candidates before update the media level "ice-pwd" and "ice-ufrag".
Candidates candidates_orig;
std::string mline_id;
// Tracks created out of the ssrc attributes.
StreamParamsVec tracks;
SsrcInfoVec ssrc_infos;
SsrcGroupVec ssrc_groups;
std::string maxptime_as_string;
std::string ptime_as_string;
std::vector<std::string> stream_ids;
std::string track_id;
SimulcastSdpSerializer deserializer;
std::vector<RidDescription> rids;
SimulcastDescription simulcast;
// Loop until the next m line
while (!IsLineType(message, kLineTypeMedia, *pos)) {
std::optional<absl::string_view> line = GetLine(message, pos);
if (!line.has_value()) {
if (*pos >= message.size()) {
break; // Done parsing
} else {
return ParseFailed(message, *pos, "Invalid SDP line.", error);
}
}
// RFC 4566
// b=* (zero or more bandwidth information lines)
if (IsLineType(*line, kLineTypeSessionBandwidth)) {
std::string bandwidth;
std::string bandwidth_type;
if (!rtc::tokenize_first(line->substr(kLinePrefixLength),
kSdpDelimiterColonChar, &bandwidth_type,
&bandwidth)) {
return ParseFailed(
*line,
"b= syntax error, does not match b=<modifier>:<bandwidth-value>.",
error);
}
if (!(bandwidth_type == kApplicationSpecificBandwidth ||
bandwidth_type == kTransportSpecificBandwidth)) {
// Ignore unknown bandwidth types.
continue;
}
int b = 0;
if (!GetValueFromString(*line, bandwidth, &b, error)) {
return false;
}
// TODO(deadbeef): Historically, applications may be setting a value
// of -1 to mean "unset any previously set bandwidth limit", even
// though ommitting the "b=AS" entirely will do just that. Once we've
// transitioned applications to doing the right thing, it would be
// better to treat this as a hard error instead of just ignoring it.
if (bandwidth_type == kApplicationSpecificBandwidth && b == -1) {
RTC_LOG(LS_WARNING) << "Ignoring \"b=AS:-1\"; will be treated as \"no "
"bandwidth limit\".";
continue;
}
if (b < 0) {
return ParseFailed(
*line, "b=" + bandwidth_type + " value can't be negative.", error);
}
// Convert values. Prevent integer overflow.
if (bandwidth_type == kApplicationSpecificBandwidth) {
b = std::min(b, INT_MAX / 1000) * 1000;
} else {
b = std::min(b, INT_MAX);
}
media_desc->set_bandwidth(b);
media_desc->set_bandwidth_type(bandwidth_type);
continue;
}
// Parse the media level connection data.
if (IsLineType(*line, kLineTypeConnection)) {
rtc::SocketAddress addr;
if (!ParseConnectionData(*line, &addr, error)) {
return false;
}
media_desc->set_connection_address(addr);
continue;
}
if (!IsLineType(*line, kLineTypeAttributes)) {
// TODO(deadbeef): Handle other lines if needed.
RTC_LOG(LS_VERBOSE) << "Ignored line: " << *line;
continue;
}
// Handle attributes common to SCTP and RTP.
if (HasAttribute(*line, kAttributeMid)) {
// RFC 3388
// mid-attribute = "a=mid:" identification-tag
// identification-tag = token
// Use the mid identification-tag as the content name.
if (!GetSingleTokenValue(*line, kAttributeMid, &mline_id, error)) {
return false;
}
*content_name = mline_id;
} else if (HasAttribute(*line, kAttributeBundleOnly)) {
*bundle_only = true;
} else if (HasAttribute(*line, kAttributeCandidate)) {
Candidate candidate;
if (!ParseCandidate(*line, &candidate, error, false)) {
return false;
}
// ParseCandidate will parse non-standard ufrag and password attributes,
// since it's used for candidate trickling, but we only want to process
// the "a=ice-ufrag"/"a=ice-pwd" values in a session description, so
// strip them off at this point.
candidate.set_username(std::string());
candidate.set_password(std::string());
candidates_orig.push_back(candidate);
} else if (HasAttribute(*line, kAttributeIceUfrag)) {
if (!GetValue(*line, kAttributeIceUfrag, &transport->ice_ufrag, error)) {
return false;
}
} else if (HasAttribute(*line, kAttributeIcePwd)) {
if (!GetValue(*line, kAttributeIcePwd, &transport->ice_pwd, error)) {
return false;
}
} else if (HasAttribute(*line, kAttributeIceOption)) {
if (!ParseIceOptions(*line, &transport->transport_options, error)) {
return false;
}
} else if (HasAttribute(*line, kAttributeFmtp)) {
if (!ParseFmtpAttributes(*line, media_type, media_desc, error)) {
return false;
}
} else if (HasAttribute(*line, kAttributeFingerprint)) {
std::unique_ptr<rtc::SSLFingerprint> fingerprint;
if (!ParseFingerprintAttribute(*line, &fingerprint, error)) {
return false;
}
transport->identity_fingerprint = std::move(fingerprint);
} else if (HasAttribute(*line, kAttributeSetup)) {
if (!ParseDtlsSetup(*line, &(transport->connection_role), error)) {
return false;
}
} else if (cricket::IsDtlsSctp(protocol) &&
media_type == cricket::MEDIA_TYPE_DATA) {
//
// SCTP specific attributes
//
if (HasAttribute(*line, kAttributeSctpPort)) {
if (media_desc->as_sctp()->use_sctpmap()) {
return ParseFailed(
*line, "sctp-port attribute can't be used with sctpmap.", error);
}
int sctp_port;
if (!ParseSctpPort(*line, &sctp_port, error)) {
return false;
}
media_desc->as_sctp()->set_port(sctp_port);
} else if (HasAttribute(*line, kAttributeMaxMessageSize)) {
int max_message_size;
if (!ParseSctpMaxMessageSize(*line, &max_message_size, error)) {
return false;
}
media_desc->as_sctp()->set_max_message_size(max_message_size);
} else if (HasAttribute(*line, kAttributeSctpmap)) {
// Ignore a=sctpmap: from early versions of draft-ietf-mmusic-sctp-sdp
continue;
}
} else if (cricket::IsRtpProtocol(protocol)) {
//
// RTP specific attributes
//
if (HasAttribute(*line, kAttributeRtcpMux)) {
media_desc->set_rtcp_mux(true);
} else if (HasAttribute(*line, kAttributeRtcpReducedSize)) {
media_desc->set_rtcp_reduced_size(true);
} else if (HasAttribute(*line, kAttributeRtcpRemoteEstimate)) {
media_desc->set_remote_estimate(true);
} else if (HasAttribute(*line, kAttributeSsrcGroup)) {
if (!ParseSsrcGroupAttribute(*line, &ssrc_groups, error)) {
return false;
}
} else if (HasAttribute(*line, kAttributeSsrc)) {
if (!ParseSsrcAttribute(*line, &ssrc_infos, msid_signaling, error)) {
return false;
}
} else if (HasAttribute(*line, kAttributeRtpmap)) {
if (!ParseRtpmapAttribute(*line, media_type, payload_types, media_desc,
error)) {
return false;
}
} else if (HasAttribute(*line, kCodecParamMaxPTime)) {
if (!GetValue(*line, kCodecParamMaxPTime, &maxptime_as_string, error)) {
return false;
}
} else if (HasAttribute(*line, kAttributePacketization)) {
if (!ParsePacketizationAttribute(*line, media_type, media_desc,
error)) {
return false;
}
} else if (HasAttribute(*line, kAttributeRtcpFb)) {
if (!ParseRtcpFbAttribute(*line, media_type, media_desc, error)) {
return false;
}
} else if (HasAttribute(*line, kCodecParamPTime)) {
if (!GetValue(*line, kCodecParamPTime, &ptime_as_string, error)) {
return false;
}
} else if (HasAttribute(*line, kAttributeSendOnly)) {
media_desc->set_direction(RtpTransceiverDirection::kSendOnly);
} else if (HasAttribute(*line, kAttributeRecvOnly)) {
media_desc->set_direction(RtpTransceiverDirection::kRecvOnly);
} else if (HasAttribute(*line, kAttributeInactive)) {
media_desc->set_direction(RtpTransceiverDirection::kInactive);
} else if (HasAttribute(*line, kAttributeSendRecv)) {
media_desc->set_direction(RtpTransceiverDirection::kSendRecv);
} else if (HasAttribute(*line, kAttributeExtmapAllowMixed)) {
media_desc->set_extmap_allow_mixed_enum(
MediaContentDescription::kMedia);
} else if (HasAttribute(*line, kAttributeExtmap)) {
RtpExtension extmap;
if (!ParseExtmap(*line, &extmap, error)) {
return false;
}
media_desc->AddRtpHeaderExtension(extmap);
} else if (HasAttribute(*line, kAttributeXGoogleFlag)) {
// Experimental attribute. Conference mode activates more aggressive
// AEC and NS settings.
// TODO(deadbeef): expose API to set these directly.
std::string flag_value;
if (!GetValue(*line, kAttributeXGoogleFlag, &flag_value, error)) {
return false;
}
if (flag_value.compare(kValueConference) == 0)
media_desc->set_conference_mode(true);
} else if (HasAttribute(*line, kAttributeMsid)) {
if (!ParseMsidAttribute(*line, &stream_ids, &track_id, error)) {
return false;
}
*msid_signaling |= cricket::kMsidSignalingMediaSection;
} else if (HasAttribute(*line, kAttributeRid)) {
const size_t kRidPrefixLength =
kLinePrefixLength + arraysize(kAttributeRid);
if (line->size() <= kRidPrefixLength) {
RTC_LOG(LS_INFO) << "Ignoring empty RID attribute: " << *line;
continue;
}
RTCErrorOr<RidDescription> error_or_rid_description =
deserializer.DeserializeRidDescription(
line->substr(kRidPrefixLength));
// Malformed a=rid lines are discarded.
if (!error_or_rid_description.ok()) {
RTC_LOG(LS_INFO) << "Ignoring malformed RID line: '" << *line
<< "'. Error: "
<< error_or_rid_description.error().message();
continue;
}
rids.push_back(error_or_rid_description.MoveValue());
} else if (HasAttribute(*line, kAttributeSimulcast)) {
const size_t kSimulcastPrefixLength =
kLinePrefixLength + arraysize(kAttributeSimulcast);
if (line->size() <= kSimulcastPrefixLength) {
return ParseFailed(*line, "Simulcast attribute is empty.", error);
}
if (!simulcast.empty()) {
return ParseFailed(*line, "Multiple Simulcast attributes specified.",
error);
}
RTCErrorOr<SimulcastDescription> error_or_simulcast =
deserializer.DeserializeSimulcastDescription(
line->substr(kSimulcastPrefixLength));
if (!error_or_simulcast.ok()) {
return ParseFailed(*line,
std::string("Malformed simulcast line: ") +
error_or_simulcast.error().message(),
error);
}
simulcast = error_or_simulcast.value();
} else if (HasAttribute(*line, kAttributeRtcp)) {
// Ignore and do not log a=rtcp line.
// JSEP section 5.8.2 (media section parsing) says to ignore it.
continue;
} else {
// Unrecognized attribute in RTP protocol.
RTC_LOG(LS_VERBOSE) << "Ignored line: " << *line;
continue;
}
} else {
// Only parse lines that we are interested of.
RTC_LOG(LS_VERBOSE) << "Ignored line: " << *line;
continue;
}
}
// Remove duplicate or inconsistent rids.
RemoveInvalidRidDescriptions(payload_types, &rids);
// If simulcast is specifed, split the rids into send and receive.
// Rids that do not appear in simulcast attribute will be removed.
std::vector<RidDescription> send_rids;
std::vector<RidDescription> receive_rids;
if (!simulcast.empty()) {
// Verify that the rids in simulcast match rids in sdp.
RemoveInvalidRidsFromSimulcast(rids, &simulcast);
// Use simulcast description to figure out Send / Receive RIDs.
std::map<std::string, RidDescription> rid_map;
for (const RidDescription& rid : rids) {
rid_map[rid.rid] = rid;
}
for (const auto& layer : simulcast.send_layers().GetAllLayers()) {
auto iter = rid_map.find(layer.rid);
RTC_DCHECK(iter != rid_map.end());
send_rids.push_back(iter->second);
}
for (const auto& layer : simulcast.receive_layers().GetAllLayers()) {
auto iter = rid_map.find(layer.rid);
RTC_DCHECK(iter != rid_map.end());
receive_rids.push_back(iter->second);
}
media_desc->set_simulcast_description(simulcast);
} else {
// RID is specified in RFC 8851, which identifies a lot of usages.
// We only support RFC 8853 usage of RID, not anything else.
// Ignore all RID parameters when a=simulcast is missing.
// In particular do NOT do send_rids = rids;
RTC_LOG(LS_VERBOSE) << "Ignoring send_rids without simulcast";
}
media_desc->set_receive_rids(receive_rids);
// Create tracks from the `ssrc_infos`.
// If the stream_id/track_id for all SSRCS are identical, one StreamParams
// will be created in CreateTracksFromSsrcInfos, containing all the SSRCs from
// the m= section.
if (!ssrc_infos.empty()) {
CreateTracksFromSsrcInfos(ssrc_infos, stream_ids, track_id, &tracks,
*msid_signaling);
} else if (media_type != cricket::MEDIA_TYPE_DATA &&
(*msid_signaling & cricket::kMsidSignalingMediaSection)) {
// If the stream_ids/track_id was signaled but SSRCs were unsignaled we
// still create a track. This isn't done for data media types because
// StreamParams aren't used for SCTP streams, and RTP data channels don't
// support unsignaled SSRCs.
// If track id was not specified, create a random one.
if (track_id.empty()) {
track_id = rtc::CreateRandomString(8);
}
CreateTrackWithNoSsrcs(stream_ids, track_id, send_rids, &tracks);
}
// Add the ssrc group to the track.
for (const SsrcGroup& ssrc_group : ssrc_groups) {
if (ssrc_group.ssrcs.empty()) {
continue;
}
uint32_t ssrc = ssrc_group.ssrcs.front();
for (StreamParams& track : tracks) {
if (track.has_ssrc(ssrc)) {
track.ssrc_groups.push_back(ssrc_group);
}
}
}
// Add the new tracks to the `media_desc`.
for (StreamParams& track : tracks) {
media_desc->AddStream(track);
}
UpdateFromWildcardCodecs(media_desc);
// Codec has not been populated correctly unless the name has been set. This
// can happen if an SDP has an fmtp or rtcp-fb with a payload type but doesn't
// have a corresponding "rtpmap" line. This should lead to a parse error.
if (!absl::c_all_of(media_desc->codecs(), [](const cricket::Codec codec) {
return !codec.name.empty();
})) {
return ParseFailed("Failed to parse codecs correctly.", error);
}
if (media_type == cricket::MEDIA_TYPE_AUDIO) {
AddAudioAttribute(kCodecParamMaxPTime, maxptime_as_string, media_desc);
AddAudioAttribute(kCodecParamPTime, ptime_as_string, media_desc);
}
// RFC 5245
// Update the candidates with the media level "ice-pwd" and "ice-ufrag".
for (Candidate& candidate : candidates_orig) {
RTC_DCHECK(candidate.username().empty() ||
candidate.username() == transport->ice_ufrag);
candidate.set_username(transport->ice_ufrag);
RTC_DCHECK(candidate.password().empty());
candidate.set_password(transport->ice_pwd);
candidates->push_back(
std::make_unique<JsepIceCandidate>(mline_id, mline_index, candidate));
}
return true;
}
bool ParseSsrcAttribute(absl::string_view line,
SsrcInfoVec* ssrc_infos,
int* msid_signaling,
SdpParseError* error) {
RTC_DCHECK(ssrc_infos != NULL);
// RFC 5576
// a=ssrc:<ssrc-id> <attribute>
// a=ssrc:<ssrc-id> <attribute>:<value>
std::string field1, field2;
if (!rtc::tokenize_first(line.substr(kLinePrefixLength),
kSdpDelimiterSpaceChar, &field1, &field2)) {
const size_t expected_fields = 2;
return ParseFailedExpectFieldNum(line, expected_fields, error);
}
// ssrc:<ssrc-id>
std::string ssrc_id_s;
if (!GetValue(field1, kAttributeSsrc, &ssrc_id_s, error)) {
return false;
}
uint32_t ssrc_id = 0;
if (!GetValueFromString(line, ssrc_id_s, &ssrc_id, error)) {
return false;
}
std::string attribute;
std::string value;
if (!rtc::tokenize_first(field2, kSdpDelimiterColonChar, &attribute,
&value)) {
rtc::StringBuilder description;
description << "Failed to get the ssrc attribute value from " << field2
<< ". Expected format <attribute>:<value>.";
return ParseFailed(line, description.Release(), error);
}
// Check if there's already an item for this `ssrc_id`. Create a new one if
// there isn't.
auto ssrc_info_it =
absl::c_find_if(*ssrc_infos, [ssrc_id](const SsrcInfo& ssrc_info) {
return ssrc_info.ssrc_id == ssrc_id;
});
if (ssrc_info_it == ssrc_infos->end()) {
SsrcInfo info;
info.ssrc_id = ssrc_id;
ssrc_infos->push_back(info);
ssrc_info_it = ssrc_infos->end() - 1;
}
SsrcInfo& ssrc_info = *ssrc_info_it;
// Store the info to the `ssrc_info`.
if (attribute == kSsrcAttributeCname) {
// RFC 5576
// cname:<value>
ssrc_info.cname = value;
} else if (attribute == kSsrcAttributeMsid) {
// draft-alvestrand-mmusic-msid-00
// msid:identifier [appdata]
std::vector<absl::string_view> fields =
rtc::split(value, kSdpDelimiterSpaceChar);
if (fields.size() < 1 || fields.size() > 2) {
return ParseFailed(
line, "Expected format \"msid:<identifier>[ <appdata>]\".", error);
}
ssrc_info.stream_id = std::string(fields[0]);
if (fields.size() == 2) {
ssrc_info.track_id = std::string(fields[1]);
}
*msid_signaling |= cricket::kMsidSignalingSsrcAttribute;
} else {
RTC_LOG(LS_INFO) << "Ignored unknown ssrc-specific attribute: " << line;
}
return true;
}
bool ParseSsrcGroupAttribute(absl::string_view line,
SsrcGroupVec* ssrc_groups,
SdpParseError* error) {
RTC_DCHECK(ssrc_groups != NULL);
// RFC 5576
// a=ssrc-group:<semantics> <ssrc-id> ...
std::vector<absl::string_view> fields =
rtc::split(line.substr(kLinePrefixLength), kSdpDelimiterSpaceChar);
const size_t expected_min_fields = 2;
if (fields.size() < expected_min_fields) {
return ParseFailedExpectMinFieldNum(line, expected_min_fields, error);
}
std::string semantics;
if (!GetValue(fields[0], kAttributeSsrcGroup, &semantics, error)) {
return false;
}
std::vector<uint32_t> ssrcs;
for (size_t i = 1; i < fields.size(); ++i) {
uint32_t ssrc = 0;
if (!GetValueFromString(line, fields[i], &ssrc, error)) {
return false;
}
// Reject duplicates. While not forbidden by RFC 5576,
// they don't make sense.
if (absl::c_linear_search(ssrcs, ssrc)) {
return ParseFailed(line, "Duplicate SSRC in ssrc-group", error);
}
ssrcs.push_back(ssrc);
}
ssrc_groups->push_back(SsrcGroup(semantics, ssrcs));
return true;
}
// Updates or creates a new codec entry in the audio description with according
// to `name`, `clockrate`, `bitrate`, and `channels`.
void UpdateCodec(int payload_type,
absl::string_view name,
int clockrate,
int bitrate,
size_t channels,
MediaContentDescription* desc) {
// Codec may already be populated with (only) optional parameters
// (from an fmtp).
cricket::Codec codec =
GetCodecWithPayloadType(desc->type(), desc->codecs(), payload_type);
codec.name = std::string(name);
codec.clockrate = clockrate;
codec.bitrate = bitrate;
codec.channels = channels;
AddOrReplaceCodec(desc, codec);
}
// Updates or creates a new codec entry in the video description according to
// `name`, `width`, `height`, and `framerate`.
void UpdateCodec(int payload_type,
absl::string_view name,
MediaContentDescription* desc) {
// Codec may already be populated with (only) optional parameters
// (from an fmtp).
cricket::Codec codec =
GetCodecWithPayloadType(desc->type(), desc->codecs(), payload_type);
codec.name = std::string(name);
AddOrReplaceCodec(desc, codec);
}
bool ParseRtpmapAttribute(absl::string_view line,
const cricket::MediaType media_type,
const std::vector<int>& payload_types,
MediaContentDescription* media_desc,
SdpParseError* error) {
static const int kFirstDynamicPayloadTypeLowerRange = 35;
std::vector<absl::string_view> fields =
rtc::split(line.substr(kLinePrefixLength), kSdpDelimiterSpaceChar);
// RFC 4566
// a=rtpmap:<payload type> <encoding name>/<clock rate>[/<encodingparameters>]
const size_t expected_min_fields = 2;
if (fields.size() < expected_min_fields) {
return ParseFailedExpectMinFieldNum(line, expected_min_fields, error);
}
std::string payload_type_value;
if (!GetValue(fields[0], kAttributeRtpmap, &payload_type_value, error)) {
return false;
}
int payload_type = 0;
if (!GetPayloadTypeFromString(line, payload_type_value, &payload_type,
error)) {
return false;
}
if (!absl::c_linear_search(payload_types, payload_type)) {
RTC_LOG(LS_WARNING) << "Ignore rtpmap line that did not appear in the "
"<fmt> of the m-line: "
<< line;
return true;
}
std::vector<absl::string_view> codec_params = rtc::split(fields[1], '/');
// <encoding name>/<clock rate>[/<encodingparameters>]
// 2 mandatory fields
if (codec_params.size() < 2 || codec_params.size() > 3) {
return ParseFailed(line,
"Expected format \"<encoding name>/<clock rate>"
"[/<encodingparameters>]\".",
error);
}
const absl::string_view encoding_name = codec_params[0];
int clock_rate = 0;
if (!GetValueFromString(line, codec_params[1], &clock_rate, error)) {
return false;
}
if (media_type == cricket::MEDIA_TYPE_VIDEO) {
for (const cricket::Codec& existing_codec : media_desc->codecs()) {
if (!existing_codec.name.empty() && payload_type == existing_codec.id &&
(!absl::EqualsIgnoreCase(encoding_name, existing_codec.name) ||
clock_rate != existing_codec.clockrate)) {
rtc::StringBuilder description;
description
<< "Duplicate "
<< (payload_type < kFirstDynamicPayloadTypeLowerRange
? "statically assigned"
: "")
<< " payload type with conflicting codec name or clock rate.";
return ParseFailed(line, description.Release(), error);
}
}
UpdateCodec(payload_type, encoding_name, media_desc);
} else if (media_type == cricket::MEDIA_TYPE_AUDIO) {
// RFC 4566
// For audio streams, <encoding parameters> indicates the number
// of audio channels. This parameter is OPTIONAL and may be
// omitted if the number of channels is one, provided that no
// additional parameters are needed.
size_t channels = 1;
if (codec_params.size() == 3) {
if (!GetValueFromString(line, codec_params[2], &channels, error)) {
return false;
}
}
if (channels > kMaxNumberOfChannels) {
return ParseFailed(line, "At most 24 channels are supported.", error);
}
for (const cricket::Codec& existing_codec : media_desc->codecs()) {
// TODO(crbug.com/1338902) re-add checks for clockrate and number of
// channels.
if (!existing_codec.name.empty() && payload_type == existing_codec.id &&
(!absl::EqualsIgnoreCase(encoding_name, existing_codec.name))) {
rtc::StringBuilder description;
description
<< "Duplicate "
<< (payload_type < kFirstDynamicPayloadTypeLowerRange
? "statically assigned"
: "")
<< " payload type with conflicting codec name or clock rate.";
return ParseFailed(line, description.Release(), error);
}
}
UpdateCodec(payload_type, encoding_name, clock_rate, 0, channels,
media_desc);
}
return true;
}
bool ParseFmtpParam(absl::string_view line,
std::string* parameter,
std::string* value,
SdpParseError* error) {
if (!rtc::tokenize_first(line, kSdpDelimiterEqualChar, parameter, value)) {
// Support for non-key-value lines like RFC 2198 or RFC 4733.
*parameter = "";
*value = std::string(line);
return true;
}
// a=fmtp:<payload_type> <param1>=<value1>; <param2>=<value2>; ...
return true;
}
bool ParseFmtpParameterSet(absl::string_view line_params,
webrtc::CodecParameterMap& codec_params,
SdpParseError* error) {
// Parse out format specific parameters.
for (absl::string_view param :
rtc::split(line_params, kSdpDelimiterSemicolonChar)) {
std::string name;
std::string value;
if (!ParseFmtpParam(absl::StripAsciiWhitespace(param), &name, &value,
error)) {
return false;
}
if (codec_params.find(name) != codec_params.end()) {
RTC_LOG(LS_INFO) << "Overwriting duplicate fmtp parameter with key \""
<< name << "\".";
}
codec_params[name] = value;
}
return true;
}
bool ParseFmtpAttributes(absl::string_view line,
const cricket::MediaType media_type,
MediaContentDescription* media_desc,
SdpParseError* error) {
if (media_type != cricket::MEDIA_TYPE_AUDIO &&
media_type != cricket::MEDIA_TYPE_VIDEO) {
return true;
}
std::string line_payload;
std::string line_params;
// https://tools.ietf.org/html/rfc4566#section-6
// a=fmtp:<format> <format specific parameters>
// At least two fields, whereas the second one is any of the optional
// parameters.
if (!rtc::tokenize_first(line.substr(kLinePrefixLength),
kSdpDelimiterSpaceChar, &line_payload,
&line_params)) {
ParseFailedExpectMinFieldNum(line, 2, error);
return false;
}
// Parse out the payload information.
std::string payload_type_str;
if (!GetValue(line_payload, kAttributeFmtp, &payload_type_str, error)) {
return false;
}
int payload_type = 0;
if (!GetPayloadTypeFromString(line_payload, payload_type_str, &payload_type,
error)) {
return false;
}
// Parse out format specific parameters.
webrtc::CodecParameterMap codec_params;
if (!ParseFmtpParameterSet(line_params, codec_params, error)) {
return false;
}
if (media_type == cricket::MEDIA_TYPE_AUDIO ||
media_type == cricket::MEDIA_TYPE_VIDEO) {
UpdateCodec(media_desc, payload_type, codec_params);
}
return true;
}
bool ParsePacketizationAttribute(absl::string_view line,
const cricket::MediaType media_type,
MediaContentDescription* media_desc,
SdpParseError* error) {
if (media_type != cricket::MEDIA_TYPE_VIDEO) {
return true;
}
std::vector<absl::string_view> packetization_fields =
rtc::split(line, kSdpDelimiterSpaceChar);
if (packetization_fields.size() < 2) {
return ParseFailedGetValue(line, kAttributePacketization, error);
}
std::string payload_type_string;
if (!GetValue(packetization_fields[0], kAttributePacketization,
&payload_type_string, error)) {
return false;
}
int payload_type;
if (!GetPayloadTypeFromString(line, payload_type_string, &payload_type,
error)) {
return false;
}
absl::string_view packetization = packetization_fields[1];
UpdateVideoCodecPacketization(media_desc, payload_type, packetization);
return true;
}
bool ParseRtcpFbAttribute(absl::string_view line,
const cricket::MediaType media_type,
MediaContentDescription* media_desc,
SdpParseError* error) {
if (media_type != cricket::MEDIA_TYPE_AUDIO &&
media_type != cricket::MEDIA_TYPE_VIDEO) {
return true;
}
std::vector<absl::string_view> rtcp_fb_fields =
rtc::split(line, kSdpDelimiterSpaceChar);
if (rtcp_fb_fields.size() < 2) {
return ParseFailedGetValue(line, kAttributeRtcpFb, error);
}
std::string payload_type_string;
if (!GetValue(rtcp_fb_fields[0], kAttributeRtcpFb, &payload_type_string,
error)) {
return false;
}
int payload_type = kWildcardPayloadType;
if (payload_type_string != "*") {
if (!GetPayloadTypeFromString(line, payload_type_string, &payload_type,
error)) {
return false;
}
}
absl::string_view id = rtcp_fb_fields[1];
std::string param = "";
for (auto iter = rtcp_fb_fields.begin() + 2; iter != rtcp_fb_fields.end();
++iter) {
param.append(iter->data(), iter->length());
}
const cricket::FeedbackParam feedback_param(id, param);
if (media_type == cricket::MEDIA_TYPE_AUDIO ||
media_type == cricket::MEDIA_TYPE_VIDEO) {
UpdateCodec(media_desc, payload_type, feedback_param);
}
return true;
}
} // namespace webrtc