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/*
* Copyright 2018 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/sdp_serializer.h"
#include <map>
#include <string>
#include <type_traits>
#include <utility>
#include <vector>
#include "absl/algorithm/container.h"
#include "absl/strings/string_view.h"
#include "absl/types/optional.h"
#include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
#include "rtc_base/checks.h"
#include "rtc_base/string_encode.h"
#include "rtc_base/string_to_number.h"
#include "rtc_base/strings/string_builder.h"
using cricket::RidDescription;
using cricket::RidDirection;
using cricket::SimulcastDescription;
using cricket::SimulcastLayer;
using cricket::SimulcastLayerList;
namespace webrtc {
namespace {
// delimiters
const char kDelimiterComma[] = ",";
const char kDelimiterCommaChar = ',';
const char kDelimiterEqual[] = "=";
const char kDelimiterEqualChar = '=';
const char kDelimiterSemicolon[] = ";";
const char kDelimiterSemicolonChar = ';';
const char kDelimiterSpace[] = " ";
const char kDelimiterSpaceChar = ' ';
// https://tools.ietf.org/html/draft-ietf-mmusic-sdp-simulcast-13#section-5.1
// https://tools.ietf.org/html/draft-ietf-mmusic-rid-15#section-10
const char kSimulcastPausedStream[] = "~";
const char kSimulcastPausedStreamChar = '~';
const char kSendDirection[] = "send";
const char kReceiveDirection[] = "recv";
const char kPayloadType[] = "pt";
RTCError ParseError(absl::string_view message) {
return RTCError(RTCErrorType::SYNTAX_ERROR, message);
}
// These methods serialize simulcast according to the specification:
// https://tools.ietf.org/html/draft-ietf-mmusic-sdp-simulcast-13#section-5.1
rtc::StringBuilder& operator<<(rtc::StringBuilder& builder,
const SimulcastLayer& simulcast_layer) {
if (simulcast_layer.is_paused) {
builder << kSimulcastPausedStream;
}
builder << simulcast_layer.rid;
return builder;
}
rtc::StringBuilder& operator<<(
rtc::StringBuilder& builder,
const std::vector<SimulcastLayer>& layer_alternatives) {
bool first = true;
for (const SimulcastLayer& rid : layer_alternatives) {
if (!first) {
builder << kDelimiterComma;
}
builder << rid;
first = false;
}
return builder;
}
rtc::StringBuilder& operator<<(rtc::StringBuilder& builder,
const SimulcastLayerList& simulcast_layers) {
bool first = true;
for (const auto& alternatives : simulcast_layers) {
if (!first) {
builder << kDelimiterSemicolon;
}
builder << alternatives;
first = false;
}
return builder;
}
// This method deserializes simulcast according to the specification:
// https://tools.ietf.org/html/draft-ietf-mmusic-sdp-simulcast-13#section-5.1
// sc-str-list = sc-alt-list *( ";" sc-alt-list )
// sc-alt-list = sc-id *( "," sc-id )
// sc-id-paused = "~"
// sc-id = [sc-id-paused] rid-id
// rid-id = 1*(alpha-numeric / "-" / "_") ; see: I-D.ietf-mmusic-rid
RTCErrorOr<SimulcastLayerList> ParseSimulcastLayerList(const std::string& str) {
std::vector<absl::string_view> tokens =
rtc::split(str, kDelimiterSemicolonChar);
if (tokens.empty()) {
return ParseError("Layer list cannot be empty.");
}
SimulcastLayerList result;
for (const absl::string_view& token : tokens) {
if (token.empty()) {
return ParseError("Simulcast alternative layer list is empty.");
}
std::vector<absl::string_view> rid_tokens =
rtc::split(token, kDelimiterCommaChar);
if (rid_tokens.empty()) {
return ParseError("Simulcast alternative layer list is malformed.");
}
std::vector<SimulcastLayer> layers;
for (const absl::string_view& rid_token : rid_tokens) {
if (rid_token.empty() || rid_token == kSimulcastPausedStream) {
return ParseError("Rid must not be empty.");
}
bool paused = rid_token[0] == kSimulcastPausedStreamChar;
absl::string_view rid = paused ? rid_token.substr(1) : rid_token;
layers.push_back(SimulcastLayer(rid, paused));
}
result.AddLayerWithAlternatives(layers);
}
return std::move(result);
}
webrtc::RTCError ParseRidPayloadList(const std::string& payload_list,
RidDescription* rid_description) {
RTC_DCHECK(rid_description);
std::vector<int>& payload_types = rid_description->payload_types;
// Check that the description doesn't have any payload types or restrictions.
// If the pt= field is specified, it must be first and must not repeat.
if (!payload_types.empty()) {
return ParseError("Multiple pt= found in RID Description.");
}
if (!rid_description->restrictions.empty()) {
return ParseError("Payload list must appear first in the restrictions.");
}
// If the pt= field is specified, it must have a value.
if (payload_list.empty()) {
return ParseError("Payload list must have at least one value.");
}
// Tokenize the ',' delimited list
std::vector<std::string> string_payloads;
rtc::tokenize(payload_list, kDelimiterCommaChar, &string_payloads);
if (string_payloads.empty()) {
return ParseError("Payload list must have at least one value.");
}
for (const std::string& payload_type : string_payloads) {
absl::optional<int> value = rtc::StringToNumber<int>(payload_type);
if (!value.has_value()) {
return ParseError("Invalid payload type: " + payload_type);
}
// Check if the value already appears in the payload list.
if (absl::c_linear_search(payload_types, value.value())) {
return ParseError("Duplicate payload type in list: " + payload_type);
}
payload_types.push_back(value.value());
}
return RTCError::OK();
}
} // namespace
std::string SdpSerializer::SerializeSimulcastDescription(
const cricket::SimulcastDescription& simulcast) const {
rtc::StringBuilder sb;
std::string delimiter;
if (!simulcast.send_layers().empty()) {
sb << kSendDirection << kDelimiterSpace << simulcast.send_layers();
delimiter = kDelimiterSpace;
}
if (!simulcast.receive_layers().empty()) {
sb << delimiter << kReceiveDirection << kDelimiterSpace
<< simulcast.receive_layers();
}
return sb.str();
}
// https://tools.ietf.org/html/draft-ietf-mmusic-sdp-simulcast-13#section-5.1
// a:simulcast:<send> <streams> <recv> <streams>
// Formal Grammar
// sc-value = ( sc-send [SP sc-recv] ) / ( sc-recv [SP sc-send] )
// sc-send = %s"send" SP sc-str-list
// sc-recv = %s"recv" SP sc-str-list
// sc-str-list = sc-alt-list *( ";" sc-alt-list )
// sc-alt-list = sc-id *( "," sc-id )
// sc-id-paused = "~"
// sc-id = [sc-id-paused] rid-id
// rid-id = 1*(alpha-numeric / "-" / "_") ; see: I-D.ietf-mmusic-rid
RTCErrorOr<SimulcastDescription> SdpSerializer::DeserializeSimulcastDescription(
absl::string_view string) const {
std::vector<std::string> tokens;
rtc::tokenize(std::string(string), kDelimiterSpaceChar, &tokens);
if (tokens.size() != 2 && tokens.size() != 4) {
return ParseError("Must have one or two <direction, streams> pairs.");
}
bool bidirectional = tokens.size() == 4; // indicates both send and recv
// Tokens 0, 2 (if exists) should be send / recv
if ((tokens[0] != kSendDirection && tokens[0] != kReceiveDirection) ||
(bidirectional && tokens[2] != kSendDirection &&
tokens[2] != kReceiveDirection) ||
(bidirectional && tokens[0] == tokens[2])) {
return ParseError("Valid values: send / recv.");
}
// Tokens 1, 3 (if exists) should be alternative layer lists
RTCErrorOr<SimulcastLayerList> list1, list2;
list1 = ParseSimulcastLayerList(tokens[1]);
if (!list1.ok()) {
return list1.MoveError();
}
if (bidirectional) {
list2 = ParseSimulcastLayerList(tokens[3]);
if (!list2.ok()) {
return list2.MoveError();
}
}
// Set the layers so that list1 is for send and list2 is for recv
if (tokens[0] != kSendDirection) {
std::swap(list1, list2);
}
// Set the layers according to which pair is send and which is recv
// At this point if the simulcast is unidirectional then
// either `list1` or `list2` will be in 'error' state indicating that
// the value should not be used.
SimulcastDescription simulcast;
if (list1.ok()) {
simulcast.send_layers() = list1.MoveValue();
}
if (list2.ok()) {
simulcast.receive_layers() = list2.MoveValue();
}
return std::move(simulcast);
}
std::string SdpSerializer::SerializeRidDescription(
const RidDescription& rid_description) const {
RTC_DCHECK(!rid_description.rid.empty());
RTC_DCHECK(rid_description.direction == RidDirection::kSend ||
rid_description.direction == RidDirection::kReceive);
rtc::StringBuilder builder;
builder << rid_description.rid << kDelimiterSpace
<< (rid_description.direction == RidDirection::kSend
? kSendDirection
: kReceiveDirection);
const auto& payload_types = rid_description.payload_types;
const auto& restrictions = rid_description.restrictions;
// First property is separated by ' ', the next ones by ';'.
const char* propertyDelimiter = kDelimiterSpace;
// Serialize any codecs in the description.
if (!payload_types.empty()) {
builder << propertyDelimiter << kPayloadType << kDelimiterEqual;
propertyDelimiter = kDelimiterSemicolon;
const char* formatDelimiter = "";
for (int payload_type : payload_types) {
builder << formatDelimiter << payload_type;
formatDelimiter = kDelimiterComma;
}
}
// Serialize any restrictions in the description.
for (const auto& pair : restrictions) {
// Serialize key=val pairs. =val part is ommitted if val is empty.
builder << propertyDelimiter << pair.first;
if (!pair.second.empty()) {
builder << kDelimiterEqual << pair.second;
}
propertyDelimiter = kDelimiterSemicolon;
}
return builder.str();
}
// https://tools.ietf.org/html/draft-ietf-mmusic-rid-15#section-10
// Formal Grammar
// rid-syntax = %s"a=rid:" rid-id SP rid-dir
// [ rid-pt-param-list / rid-param-list ]
// rid-id = 1*(alpha-numeric / "-" / "_")
// rid-dir = %s"send" / %s"recv"
// rid-pt-param-list = SP rid-fmt-list *( ";" rid-param )
// rid-param-list = SP rid-param *( ";" rid-param )
// rid-fmt-list = %s"pt=" fmt *( "," fmt )
// rid-param = 1*(alpha-numeric / "-") [ "=" param-val ]
// param-val = *( %x20-58 / %x60-7E )
// ; Any printable character except semicolon
RTCErrorOr<RidDescription> SdpSerializer::DeserializeRidDescription(
absl::string_view string) const {
std::vector<std::string> tokens;
rtc::tokenize(std::string(string), kDelimiterSpaceChar, &tokens);
if (tokens.size() < 2) {
return ParseError("RID Description must contain <RID> <direction>.");
}
if (tokens.size() > 3) {
return ParseError("Invalid RID Description format. Too many arguments.");
}
if (!IsLegalRsidName(tokens[0])) {
return ParseError("Invalid RID value: " + tokens[0] + ".");
}
if (tokens[1] != kSendDirection && tokens[1] != kReceiveDirection) {
return ParseError("Invalid RID direction. Supported values: send / recv.");
}
RidDirection direction = tokens[1] == kSendDirection ? RidDirection::kSend
: RidDirection::kReceive;
RidDescription rid_description(tokens[0], direction);
// If there is a third argument it is a payload list and/or restriction list.
if (tokens.size() == 3) {
std::vector<std::string> restrictions;
rtc::tokenize(tokens[2], kDelimiterSemicolonChar, &restrictions);
// Check for malformed restriction list, such as ';' or ';;;' etc.
if (restrictions.empty()) {
return ParseError("Invalid RID restriction list: " + tokens[2]);
}
// Parse the restrictions. The payload indicator (pt) can only appear first.
for (const std::string& restriction : restrictions) {
std::vector<std::string> parts;
rtc::tokenize(restriction, kDelimiterEqualChar, &parts);
if (parts.empty() || parts.size() > 2) {
return ParseError("Invalid format for restriction: " + restriction);
}
// `parts` contains at least one value and it does not contain a space.
// Note: `parts` and other values might still contain tab, newline,
// unprintable characters, etc. which will not generate errors here but
// will (most-likely) be ignored by components down stream.
if (parts[0] == kPayloadType) {
RTCError error = ParseRidPayloadList(
parts.size() > 1 ? parts[1] : std::string(), &rid_description);
if (!error.ok()) {
return std::move(error);
}
continue;
}
// Parse `parts` as a key=value pair which allows unspecified values.
if (rid_description.restrictions.find(parts[0]) !=
rid_description.restrictions.end()) {
return ParseError("Duplicate restriction specified: " + parts[0]);
}
rid_description.restrictions[parts[0]] =
parts.size() > 1 ? parts[1] : std::string();
}
}
return std::move(rid_description);
}
} // namespace webrtc