From e1c0be4312601e8b0e6fe0850590d06f2163da49 Mon Sep 17 00:00:00 2001
From: Philipp Hancke <philipp.hancke@googlemail.com>
Date: Tue, 31 Mar 2020 11:57:35 +0200
Subject: [PATCH 1/2] webrtc: add third-party sdp module

Adds the third-party sdp module available from
  https://www.npmjs.com/package/sdp
in version 2.12.0 and commit
  958f22a94231e4c1ca651b4a7d53b0e32bb4a558
without tests or dependencies. This is going to be used by simulcast
tests and is generally useful in manipulating the SDP generated and
consumed by WebRTC.

See https://github.com/web-platform-tests/rfcs/issues/46 for discussion
on how to add third-party javascript libraries.
---
 webrtc/third_party/sdp/LICENSE |  19 +
 webrtc/third_party/sdp/sdp.js  | 825 +++++++++++++++++++++++++++++++++
 2 files changed, 844 insertions(+)
 create mode 100644 webrtc/third_party/sdp/LICENSE
 create mode 100644 webrtc/third_party/sdp/sdp.js

diff --git a/webrtc/third_party/sdp/LICENSE b/webrtc/third_party/sdp/LICENSE
new file mode 100644
index 00000000000000..09502ec0a1d874
--- /dev/null
+++ b/webrtc/third_party/sdp/LICENSE
@@ -0,0 +1,19 @@
+Copyright (c) 2017 Philipp Hancke
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/webrtc/third_party/sdp/sdp.js b/webrtc/third_party/sdp/sdp.js
new file mode 100644
index 00000000000000..d2a28706115bc5
--- /dev/null
+++ b/webrtc/third_party/sdp/sdp.js
@@ -0,0 +1,825 @@
+/* eslint-env node */
+'use strict';
+
+// SDP helpers.
+var SDPUtils = {};
+
+// Generate an alphanumeric identifier for cname or mids.
+// TODO: use UUIDs instead? https://gist.github.com/jed/982883
+SDPUtils.generateIdentifier = function() {
+  return Math.random().toString(36).substr(2, 10);
+};
+
+// The RTCP CNAME used by all peerconnections from the same JS.
+SDPUtils.localCName = SDPUtils.generateIdentifier();
+
+// Splits SDP into lines, dealing with both CRLF and LF.
+SDPUtils.splitLines = function(blob) {
+  return blob.trim().split('\n').map(function(line) {
+    return line.trim();
+  });
+};
+// Splits SDP into sessionpart and mediasections. Ensures CRLF.
+SDPUtils.splitSections = function(blob) {
+  var parts = blob.split('\nm=');
+  return parts.map(function(part, index) {
+    return (index > 0 ? 'm=' + part : part).trim() + '\r\n';
+  });
+};
+
+// returns the session description.
+SDPUtils.getDescription = function(blob) {
+  var sections = SDPUtils.splitSections(blob);
+  return sections && sections[0];
+};
+
+// returns the individual media sections.
+SDPUtils.getMediaSections = function(blob) {
+  var sections = SDPUtils.splitSections(blob);
+  sections.shift();
+  return sections;
+};
+
+// Returns lines that start with a certain prefix.
+SDPUtils.matchPrefix = function(blob, prefix) {
+  return SDPUtils.splitLines(blob).filter(function(line) {
+    return line.indexOf(prefix) === 0;
+  });
+};
+
+// Parses an ICE candidate line. Sample input:
+// candidate:702786350 2 udp 41819902 8.8.8.8 60769 typ relay raddr 8.8.8.8
+// rport 55996"
+SDPUtils.parseCandidate = function(line) {
+  var parts;
+  // Parse both variants.
+  if (line.indexOf('a=candidate:') === 0) {
+    parts = line.substring(12).split(' ');
+  } else {
+    parts = line.substring(10).split(' ');
+  }
+
+  var candidate = {
+    foundation: parts[0],
+    component: parseInt(parts[1], 10),
+    protocol: parts[2].toLowerCase(),
+    priority: parseInt(parts[3], 10),
+    ip: parts[4],
+    address: parts[4], // address is an alias for ip.
+    port: parseInt(parts[5], 10),
+    // skip parts[6] == 'typ'
+    type: parts[7]
+  };
+
+  for (var i = 8; i < parts.length; i += 2) {
+    switch (parts[i]) {
+      case 'raddr':
+        candidate.relatedAddress = parts[i + 1];
+        break;
+      case 'rport':
+        candidate.relatedPort = parseInt(parts[i + 1], 10);
+        break;
+      case 'tcptype':
+        candidate.tcpType = parts[i + 1];
+        break;
+      case 'ufrag':
+        candidate.ufrag = parts[i + 1]; // for backward compability.
+        candidate.usernameFragment = parts[i + 1];
+        break;
+      default: // extension handling, in particular ufrag
+        candidate[parts[i]] = parts[i + 1];
+        break;
+    }
+  }
+  return candidate;
+};
+
+// Translates a candidate object into SDP candidate attribute.
+SDPUtils.writeCandidate = function(candidate) {
+  var sdp = [];
+  sdp.push(candidate.foundation);
+  sdp.push(candidate.component);
+  sdp.push(candidate.protocol.toUpperCase());
+  sdp.push(candidate.priority);
+  sdp.push(candidate.address || candidate.ip);
+  sdp.push(candidate.port);
+
+  var type = candidate.type;
+  sdp.push('typ');
+  sdp.push(type);
+  if (type !== 'host' && candidate.relatedAddress &&
+      candidate.relatedPort) {
+    sdp.push('raddr');
+    sdp.push(candidate.relatedAddress);
+    sdp.push('rport');
+    sdp.push(candidate.relatedPort);
+  }
+  if (candidate.tcpType && candidate.protocol.toLowerCase() === 'tcp') {
+    sdp.push('tcptype');
+    sdp.push(candidate.tcpType);
+  }
+  if (candidate.usernameFragment || candidate.ufrag) {
+    sdp.push('ufrag');
+    sdp.push(candidate.usernameFragment || candidate.ufrag);
+  }
+  return 'candidate:' + sdp.join(' ');
+};
+
+// Parses an ice-options line, returns an array of option tags.
+// a=ice-options:foo bar
+SDPUtils.parseIceOptions = function(line) {
+  return line.substr(14).split(' ');
+};
+
+// Parses an rtpmap line, returns RTCRtpCoddecParameters. Sample input:
+// a=rtpmap:111 opus/48000/2
+SDPUtils.parseRtpMap = function(line) {
+  var parts = line.substr(9).split(' ');
+  var parsed = {
+    payloadType: parseInt(parts.shift(), 10) // was: id
+  };
+
+  parts = parts[0].split('/');
+
+  parsed.name = parts[0];
+  parsed.clockRate = parseInt(parts[1], 10); // was: clockrate
+  parsed.channels = parts.length === 3 ? parseInt(parts[2], 10) : 1;
+  // legacy alias, got renamed back to channels in ORTC.
+  parsed.numChannels = parsed.channels;
+  return parsed;
+};
+
+// Generate an a=rtpmap line from RTCRtpCodecCapability or
+// RTCRtpCodecParameters.
+SDPUtils.writeRtpMap = function(codec) {
+  var pt = codec.payloadType;
+  if (codec.preferredPayloadType !== undefined) {
+    pt = codec.preferredPayloadType;
+  }
+  var channels = codec.channels || codec.numChannels || 1;
+  return 'a=rtpmap:' + pt + ' ' + codec.name + '/' + codec.clockRate +
+      (channels !== 1 ? '/' + channels : '') + '\r\n';
+};
+
+// Parses an a=extmap line (headerextension from RFC 5285). Sample input:
+// a=extmap:2 urn:ietf:params:rtp-hdrext:toffset
+// a=extmap:2/sendonly urn:ietf:params:rtp-hdrext:toffset
+SDPUtils.parseExtmap = function(line) {
+  var parts = line.substr(9).split(' ');
+  return {
+    id: parseInt(parts[0], 10),
+    direction: parts[0].indexOf('/') > 0 ? parts[0].split('/')[1] : 'sendrecv',
+    uri: parts[1]
+  };
+};
+
+// Generates a=extmap line from RTCRtpHeaderExtensionParameters or
+// RTCRtpHeaderExtension.
+SDPUtils.writeExtmap = function(headerExtension) {
+  return 'a=extmap:' + (headerExtension.id || headerExtension.preferredId) +
+      (headerExtension.direction && headerExtension.direction !== 'sendrecv'
+        ? '/' + headerExtension.direction
+        : '') +
+      ' ' + headerExtension.uri + '\r\n';
+};
+
+// Parses an ftmp line, returns dictionary. Sample input:
+// a=fmtp:96 vbr=on;cng=on
+// Also deals with vbr=on; cng=on
+SDPUtils.parseFmtp = function(line) {
+  var parsed = {};
+  var kv;
+  var parts = line.substr(line.indexOf(' ') + 1).split(';');
+  for (var j = 0; j < parts.length; j++) {
+    kv = parts[j].trim().split('=');
+    parsed[kv[0].trim()] = kv[1];
+  }
+  return parsed;
+};
+
+// Generates an a=ftmp line from RTCRtpCodecCapability or RTCRtpCodecParameters.
+SDPUtils.writeFmtp = function(codec) {
+  var line = '';
+  var pt = codec.payloadType;
+  if (codec.preferredPayloadType !== undefined) {
+    pt = codec.preferredPayloadType;
+  }
+  if (codec.parameters && Object.keys(codec.parameters).length) {
+    var params = [];
+    Object.keys(codec.parameters).forEach(function(param) {
+      if (codec.parameters[param]) {
+        params.push(param + '=' + codec.parameters[param]);
+      } else {
+        params.push(param);
+      }
+    });
+    line += 'a=fmtp:' + pt + ' ' + params.join(';') + '\r\n';
+  }
+  return line;
+};
+
+// Parses an rtcp-fb line, returns RTCPRtcpFeedback object. Sample input:
+// a=rtcp-fb:98 nack rpsi
+SDPUtils.parseRtcpFb = function(line) {
+  var parts = line.substr(line.indexOf(' ') + 1).split(' ');
+  return {
+    type: parts.shift(),
+    parameter: parts.join(' ')
+  };
+};
+// Generate a=rtcp-fb lines from RTCRtpCodecCapability or RTCRtpCodecParameters.
+SDPUtils.writeRtcpFb = function(codec) {
+  var lines = '';
+  var pt = codec.payloadType;
+  if (codec.preferredPayloadType !== undefined) {
+    pt = codec.preferredPayloadType;
+  }
+  if (codec.rtcpFeedback && codec.rtcpFeedback.length) {
+    // FIXME: special handling for trr-int?
+    codec.rtcpFeedback.forEach(function(fb) {
+      lines += 'a=rtcp-fb:' + pt + ' ' + fb.type +
+      (fb.parameter && fb.parameter.length ? ' ' + fb.parameter : '') +
+          '\r\n';
+    });
+  }
+  return lines;
+};
+
+// Parses an RFC 5576 ssrc media attribute. Sample input:
+// a=ssrc:3735928559 cname:something
+SDPUtils.parseSsrcMedia = function(line) {
+  var sp = line.indexOf(' ');
+  var parts = {
+    ssrc: parseInt(line.substr(7, sp - 7), 10)
+  };
+  var colon = line.indexOf(':', sp);
+  if (colon > -1) {
+    parts.attribute = line.substr(sp + 1, colon - sp - 1);
+    parts.value = line.substr(colon + 1);
+  } else {
+    parts.attribute = line.substr(sp + 1);
+  }
+  return parts;
+};
+
+SDPUtils.parseSsrcGroup = function(line) {
+  var parts = line.substr(13).split(' ');
+  return {
+    semantics: parts.shift(),
+    ssrcs: parts.map(function(ssrc) {
+      return parseInt(ssrc, 10);
+    })
+  };
+};
+
+// Extracts the MID (RFC 5888) from a media section.
+// returns the MID or undefined if no mid line was found.
+SDPUtils.getMid = function(mediaSection) {
+  var mid = SDPUtils.matchPrefix(mediaSection, 'a=mid:')[0];
+  if (mid) {
+    return mid.substr(6);
+  }
+};
+
+SDPUtils.parseFingerprint = function(line) {
+  var parts = line.substr(14).split(' ');
+  return {
+    algorithm: parts[0].toLowerCase(), // algorithm is case-sensitive in Edge.
+    value: parts[1]
+  };
+};
+
+// Extracts DTLS parameters from SDP media section or sessionpart.
+// FIXME: for consistency with other functions this should only
+//   get the fingerprint line as input. See also getIceParameters.
+SDPUtils.getDtlsParameters = function(mediaSection, sessionpart) {
+  var lines = SDPUtils.matchPrefix(mediaSection + sessionpart,
+    'a=fingerprint:');
+  // Note: a=setup line is ignored since we use the 'auto' role.
+  // Note2: 'algorithm' is not case sensitive except in Edge.
+  return {
+    role: 'auto',
+    fingerprints: lines.map(SDPUtils.parseFingerprint)
+  };
+};
+
+// Serializes DTLS parameters to SDP.
+SDPUtils.writeDtlsParameters = function(params, setupType) {
+  var sdp = 'a=setup:' + setupType + '\r\n';
+  params.fingerprints.forEach(function(fp) {
+    sdp += 'a=fingerprint:' + fp.algorithm + ' ' + fp.value + '\r\n';
+  });
+  return sdp;
+};
+
+// Parses a=crypto lines into
+//   https://rawgit.com/aboba/edgertc/master/msortc-rs4.html#dictionary-rtcsrtpsdesparameters-members
+SDPUtils.parseCryptoLine = function(line) {
+  var parts = line.substr(9).split(' ');
+  return {
+    tag: parseInt(parts[0], 10),
+    cryptoSuite: parts[1],
+    keyParams: parts[2],
+    sessionParams: parts.slice(3),
+  };
+};
+
+SDPUtils.writeCryptoLine = function(parameters) {
+  return 'a=crypto:' + parameters.tag + ' ' +
+    parameters.cryptoSuite + ' ' +
+    (typeof parameters.keyParams === 'object'
+      ? SDPUtils.writeCryptoKeyParams(parameters.keyParams)
+      : parameters.keyParams) +
+    (parameters.sessionParams ? ' ' + parameters.sessionParams.join(' ') : '') +
+    '\r\n';
+};
+
+// Parses the crypto key parameters into
+//   https://rawgit.com/aboba/edgertc/master/msortc-rs4.html#rtcsrtpkeyparam*
+SDPUtils.parseCryptoKeyParams = function(keyParams) {
+  if (keyParams.indexOf('inline:') !== 0) {
+    return null;
+  }
+  var parts = keyParams.substr(7).split('|');
+  return {
+    keyMethod: 'inline',
+    keySalt: parts[0],
+    lifeTime: parts[1],
+    mkiValue: parts[2] ? parts[2].split(':')[0] : undefined,
+    mkiLength: parts[2] ? parts[2].split(':')[1] : undefined,
+  };
+};
+
+SDPUtils.writeCryptoKeyParams = function(keyParams) {
+  return keyParams.keyMethod + ':'
+    + keyParams.keySalt +
+    (keyParams.lifeTime ? '|' + keyParams.lifeTime : '') +
+    (keyParams.mkiValue && keyParams.mkiLength
+      ? '|' + keyParams.mkiValue + ':' + keyParams.mkiLength
+      : '');
+};
+
+// Extracts all SDES paramters.
+SDPUtils.getCryptoParameters = function(mediaSection, sessionpart) {
+  var lines = SDPUtils.matchPrefix(mediaSection + sessionpart,
+    'a=crypto:');
+  return lines.map(SDPUtils.parseCryptoLine);
+};
+
+// Parses ICE information from SDP media section or sessionpart.
+// FIXME: for consistency with other functions this should only
+//   get the ice-ufrag and ice-pwd lines as input.
+SDPUtils.getIceParameters = function(mediaSection, sessionpart) {
+  var ufrag = SDPUtils.matchPrefix(mediaSection + sessionpart,
+    'a=ice-ufrag:')[0];
+  var pwd = SDPUtils.matchPrefix(mediaSection + sessionpart,
+    'a=ice-pwd:')[0];
+  if (!(ufrag && pwd)) {
+    return null;
+  }
+  return {
+    usernameFragment: ufrag.substr(12),
+    password: pwd.substr(10),
+  };
+};
+
+// Serializes ICE parameters to SDP.
+SDPUtils.writeIceParameters = function(params) {
+  return 'a=ice-ufrag:' + params.usernameFragment + '\r\n' +
+      'a=ice-pwd:' + params.password + '\r\n';
+};
+
+// Parses the SDP media section and returns RTCRtpParameters.
+SDPUtils.parseRtpParameters = function(mediaSection) {
+  var description = {
+    codecs: [],
+    headerExtensions: [],
+    fecMechanisms: [],
+    rtcp: []
+  };
+  var lines = SDPUtils.splitLines(mediaSection);
+  var mline = lines[0].split(' ');
+  for (var i = 3; i < mline.length; i++) { // find all codecs from mline[3..]
+    var pt = mline[i];
+    var rtpmapline = SDPUtils.matchPrefix(
+      mediaSection, 'a=rtpmap:' + pt + ' ')[0];
+    if (rtpmapline) {
+      var codec = SDPUtils.parseRtpMap(rtpmapline);
+      var fmtps = SDPUtils.matchPrefix(
+        mediaSection, 'a=fmtp:' + pt + ' ');
+      // Only the first a=fmtp:<pt> is considered.
+      codec.parameters = fmtps.length ? SDPUtils.parseFmtp(fmtps[0]) : {};
+      codec.rtcpFeedback = SDPUtils.matchPrefix(
+        mediaSection, 'a=rtcp-fb:' + pt + ' ')
+        .map(SDPUtils.parseRtcpFb);
+      description.codecs.push(codec);
+      // parse FEC mechanisms from rtpmap lines.
+      switch (codec.name.toUpperCase()) {
+        case 'RED':
+        case 'ULPFEC':
+          description.fecMechanisms.push(codec.name.toUpperCase());
+          break;
+        default: // only RED and ULPFEC are recognized as FEC mechanisms.
+          break;
+      }
+    }
+  }
+  SDPUtils.matchPrefix(mediaSection, 'a=extmap:').forEach(function(line) {
+    description.headerExtensions.push(SDPUtils.parseExtmap(line));
+  });
+  // FIXME: parse rtcp.
+  return description;
+};
+
+// Generates parts of the SDP media section describing the capabilities /
+// parameters.
+SDPUtils.writeRtpDescription = function(kind, caps) {
+  var sdp = '';
+
+  // Build the mline.
+  sdp += 'm=' + kind + ' ';
+  sdp += caps.codecs.length > 0 ? '9' : '0'; // reject if no codecs.
+  sdp += ' UDP/TLS/RTP/SAVPF ';
+  sdp += caps.codecs.map(function(codec) {
+    if (codec.preferredPayloadType !== undefined) {
+      return codec.preferredPayloadType;
+    }
+    return codec.payloadType;
+  }).join(' ') + '\r\n';
+
+  sdp += 'c=IN IP4 0.0.0.0\r\n';
+  sdp += 'a=rtcp:9 IN IP4 0.0.0.0\r\n';
+
+  // Add a=rtpmap lines for each codec. Also fmtp and rtcp-fb.
+  caps.codecs.forEach(function(codec) {
+    sdp += SDPUtils.writeRtpMap(codec);
+    sdp += SDPUtils.writeFmtp(codec);
+    sdp += SDPUtils.writeRtcpFb(codec);
+  });
+  var maxptime = 0;
+  caps.codecs.forEach(function(codec) {
+    if (codec.maxptime > maxptime) {
+      maxptime = codec.maxptime;
+    }
+  });
+  if (maxptime > 0) {
+    sdp += 'a=maxptime:' + maxptime + '\r\n';
+  }
+  sdp += 'a=rtcp-mux\r\n';
+
+  if (caps.headerExtensions) {
+    caps.headerExtensions.forEach(function(extension) {
+      sdp += SDPUtils.writeExtmap(extension);
+    });
+  }
+  // FIXME: write fecMechanisms.
+  return sdp;
+};
+
+// Parses the SDP media section and returns an array of
+// RTCRtpEncodingParameters.
+SDPUtils.parseRtpEncodingParameters = function(mediaSection) {
+  var encodingParameters = [];
+  var description = SDPUtils.parseRtpParameters(mediaSection);
+  var hasRed = description.fecMechanisms.indexOf('RED') !== -1;
+  var hasUlpfec = description.fecMechanisms.indexOf('ULPFEC') !== -1;
+
+  // filter a=ssrc:... cname:, ignore PlanB-msid
+  var ssrcs = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
+    .map(function(line) {
+      return SDPUtils.parseSsrcMedia(line);
+    })
+    .filter(function(parts) {
+      return parts.attribute === 'cname';
+    });
+  var primarySsrc = ssrcs.length > 0 && ssrcs[0].ssrc;
+  var secondarySsrc;
+
+  var flows = SDPUtils.matchPrefix(mediaSection, 'a=ssrc-group:FID')
+    .map(function(line) {
+      var parts = line.substr(17).split(' ');
+      return parts.map(function(part) {
+        return parseInt(part, 10);
+      });
+    });
+  if (flows.length > 0 && flows[0].length > 1 && flows[0][0] === primarySsrc) {
+    secondarySsrc = flows[0][1];
+  }
+
+  description.codecs.forEach(function(codec) {
+    if (codec.name.toUpperCase() === 'RTX' && codec.parameters.apt) {
+      var encParam = {
+        ssrc: primarySsrc,
+        codecPayloadType: parseInt(codec.parameters.apt, 10)
+      };
+      if (primarySsrc && secondarySsrc) {
+        encParam.rtx = {ssrc: secondarySsrc};
+      }
+      encodingParameters.push(encParam);
+      if (hasRed) {
+        encParam = JSON.parse(JSON.stringify(encParam));
+        encParam.fec = {
+          ssrc: primarySsrc,
+          mechanism: hasUlpfec ? 'red+ulpfec' : 'red'
+        };
+        encodingParameters.push(encParam);
+      }
+    }
+  });
+  if (encodingParameters.length === 0 && primarySsrc) {
+    encodingParameters.push({
+      ssrc: primarySsrc
+    });
+  }
+
+  // we support both b=AS and b=TIAS but interpret AS as TIAS.
+  var bandwidth = SDPUtils.matchPrefix(mediaSection, 'b=');
+  if (bandwidth.length) {
+    if (bandwidth[0].indexOf('b=TIAS:') === 0) {
+      bandwidth = parseInt(bandwidth[0].substr(7), 10);
+    } else if (bandwidth[0].indexOf('b=AS:') === 0) {
+      // use formula from JSEP to convert b=AS to TIAS value.
+      bandwidth = parseInt(bandwidth[0].substr(5), 10) * 1000 * 0.95
+          - (50 * 40 * 8);
+    } else {
+      bandwidth = undefined;
+    }
+    encodingParameters.forEach(function(params) {
+      params.maxBitrate = bandwidth;
+    });
+  }
+  return encodingParameters;
+};
+
+// parses http://draft.ortc.org/#rtcrtcpparameters*
+SDPUtils.parseRtcpParameters = function(mediaSection) {
+  var rtcpParameters = {};
+
+  // Gets the first SSRC. Note tha with RTX there might be multiple
+  // SSRCs.
+  var remoteSsrc = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
+    .map(function(line) {
+      return SDPUtils.parseSsrcMedia(line);
+    })
+    .filter(function(obj) {
+      return obj.attribute === 'cname';
+    })[0];
+  if (remoteSsrc) {
+    rtcpParameters.cname = remoteSsrc.value;
+    rtcpParameters.ssrc = remoteSsrc.ssrc;
+  }
+
+  // Edge uses the compound attribute instead of reducedSize
+  // compound is !reducedSize
+  var rsize = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-rsize');
+  rtcpParameters.reducedSize = rsize.length > 0;
+  rtcpParameters.compound = rsize.length === 0;
+
+  // parses the rtcp-mux attrіbute.
+  // Note that Edge does not support unmuxed RTCP.
+  var mux = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-mux');
+  rtcpParameters.mux = mux.length > 0;
+
+  return rtcpParameters;
+};
+
+// parses either a=msid: or a=ssrc:... msid lines and returns
+// the id of the MediaStream and MediaStreamTrack.
+SDPUtils.parseMsid = function(mediaSection) {
+  var parts;
+  var spec = SDPUtils.matchPrefix(mediaSection, 'a=msid:');
+  if (spec.length === 1) {
+    parts = spec[0].substr(7).split(' ');
+    return {stream: parts[0], track: parts[1]};
+  }
+  var planB = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
+    .map(function(line) {
+      return SDPUtils.parseSsrcMedia(line);
+    })
+    .filter(function(msidParts) {
+      return msidParts.attribute === 'msid';
+    });
+  if (planB.length > 0) {
+    parts = planB[0].value.split(' ');
+    return {stream: parts[0], track: parts[1]};
+  }
+};
+
+// SCTP
+// parses draft-ietf-mmusic-sctp-sdp-26 first and falls back
+// to draft-ietf-mmusic-sctp-sdp-05
+SDPUtils.parseSctpDescription = function(mediaSection) {
+  var mline = SDPUtils.parseMLine(mediaSection);
+  var maxSizeLine = SDPUtils.matchPrefix(mediaSection, 'a=max-message-size:');
+  var maxMessageSize;
+  if (maxSizeLine.length > 0) {
+    maxMessageSize = parseInt(maxSizeLine[0].substr(19), 10);
+  }
+  if (isNaN(maxMessageSize)) {
+    maxMessageSize = 65536;
+  }
+  var sctpPort = SDPUtils.matchPrefix(mediaSection, 'a=sctp-port:');
+  if (sctpPort.length > 0) {
+    return {
+      port: parseInt(sctpPort[0].substr(12), 10),
+      protocol: mline.fmt,
+      maxMessageSize: maxMessageSize
+    };
+  }
+  var sctpMapLines = SDPUtils.matchPrefix(mediaSection, 'a=sctpmap:');
+  if (sctpMapLines.length > 0) {
+    var parts = SDPUtils.matchPrefix(mediaSection, 'a=sctpmap:')[0]
+      .substr(10)
+      .split(' ');
+    return {
+      port: parseInt(parts[0], 10),
+      protocol: parts[1],
+      maxMessageSize: maxMessageSize
+    };
+  }
+};
+
+// SCTP
+// outputs the draft-ietf-mmusic-sctp-sdp-26 version that all browsers
+// support by now receiving in this format, unless we originally parsed
+// as the draft-ietf-mmusic-sctp-sdp-05 format (indicated by the m-line
+// protocol of DTLS/SCTP -- without UDP/ or TCP/)
+SDPUtils.writeSctpDescription = function(media, sctp) {
+  var output = [];
+  if (media.protocol !== 'DTLS/SCTP') {
+    output = [
+      'm=' + media.kind + ' 9 ' + media.protocol + ' ' + sctp.protocol + '\r\n',
+      'c=IN IP4 0.0.0.0\r\n',
+      'a=sctp-port:' + sctp.port + '\r\n'
+    ];
+  } else {
+    output = [
+      'm=' + media.kind + ' 9 ' + media.protocol + ' ' + sctp.port + '\r\n',
+      'c=IN IP4 0.0.0.0\r\n',
+      'a=sctpmap:' + sctp.port + ' ' + sctp.protocol + ' 65535\r\n'
+    ];
+  }
+  if (sctp.maxMessageSize !== undefined) {
+    output.push('a=max-message-size:' + sctp.maxMessageSize + '\r\n');
+  }
+  return output.join('');
+};
+
+// Generate a session ID for SDP.
+// https://tools.ietf.org/html/draft-ietf-rtcweb-jsep-20#section-5.2.1
+// recommends using a cryptographically random +ve 64-bit value
+// but right now this should be acceptable and within the right range
+SDPUtils.generateSessionId = function() {
+  return Math.random().toString().substr(2, 21);
+};
+
+// Write boilder plate for start of SDP
+// sessId argument is optional - if not supplied it will
+// be generated randomly
+// sessVersion is optional and defaults to 2
+// sessUser is optional and defaults to 'thisisadapterortc'
+SDPUtils.writeSessionBoilerplate = function(sessId, sessVer, sessUser) {
+  var sessionId;
+  var version = sessVer !== undefined ? sessVer : 2;
+  if (sessId) {
+    sessionId = sessId;
+  } else {
+    sessionId = SDPUtils.generateSessionId();
+  }
+  var user = sessUser || 'thisisadapterortc';
+  // FIXME: sess-id should be an NTP timestamp.
+  return 'v=0\r\n' +
+      'o=' + user + ' ' + sessionId + ' ' + version +
+        ' IN IP4 127.0.0.1\r\n' +
+      's=-\r\n' +
+      't=0 0\r\n';
+};
+
+SDPUtils.writeMediaSection = function(transceiver, caps, type, stream) {
+  var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps);
+
+  // Map ICE parameters (ufrag, pwd) to SDP.
+  sdp += SDPUtils.writeIceParameters(
+    transceiver.iceGatherer.getLocalParameters());
+
+  // Map DTLS parameters to SDP.
+  sdp += SDPUtils.writeDtlsParameters(
+    transceiver.dtlsTransport.getLocalParameters(),
+    type === 'offer' ? 'actpass' : 'active');
+
+  sdp += 'a=mid:' + transceiver.mid + '\r\n';
+
+  if (transceiver.direction) {
+    sdp += 'a=' + transceiver.direction + '\r\n';
+  } else if (transceiver.rtpSender && transceiver.rtpReceiver) {
+    sdp += 'a=sendrecv\r\n';
+  } else if (transceiver.rtpSender) {
+    sdp += 'a=sendonly\r\n';
+  } else if (transceiver.rtpReceiver) {
+    sdp += 'a=recvonly\r\n';
+  } else {
+    sdp += 'a=inactive\r\n';
+  }
+
+  if (transceiver.rtpSender) {
+    // spec.
+    var msid = 'msid:' + stream.id + ' ' +
+        transceiver.rtpSender.track.id + '\r\n';
+    sdp += 'a=' + msid;
+
+    // for Chrome.
+    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
+        ' ' + msid;
+    if (transceiver.sendEncodingParameters[0].rtx) {
+      sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
+          ' ' + msid;
+      sdp += 'a=ssrc-group:FID ' +
+          transceiver.sendEncodingParameters[0].ssrc + ' ' +
+          transceiver.sendEncodingParameters[0].rtx.ssrc +
+          '\r\n';
+    }
+  }
+  // FIXME: this should be written by writeRtpDescription.
+  sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
+      ' cname:' + SDPUtils.localCName + '\r\n';
+  if (transceiver.rtpSender && transceiver.sendEncodingParameters[0].rtx) {
+    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
+        ' cname:' + SDPUtils.localCName + '\r\n';
+  }
+  return sdp;
+};
+
+// Gets the direction from the mediaSection or the sessionpart.
+SDPUtils.getDirection = function(mediaSection, sessionpart) {
+  // Look for sendrecv, sendonly, recvonly, inactive, default to sendrecv.
+  var lines = SDPUtils.splitLines(mediaSection);
+  for (var i = 0; i < lines.length; i++) {
+    switch (lines[i]) {
+      case 'a=sendrecv':
+      case 'a=sendonly':
+      case 'a=recvonly':
+      case 'a=inactive':
+        return lines[i].substr(2);
+      default:
+        // FIXME: What should happen here?
+    }
+  }
+  if (sessionpart) {
+    return SDPUtils.getDirection(sessionpart);
+  }
+  return 'sendrecv';
+};
+
+SDPUtils.getKind = function(mediaSection) {
+  var lines = SDPUtils.splitLines(mediaSection);
+  var mline = lines[0].split(' ');
+  return mline[0].substr(2);
+};
+
+SDPUtils.isRejected = function(mediaSection) {
+  return mediaSection.split(' ', 2)[1] === '0';
+};
+
+SDPUtils.parseMLine = function(mediaSection) {
+  var lines = SDPUtils.splitLines(mediaSection);
+  var parts = lines[0].substr(2).split(' ');
+  return {
+    kind: parts[0],
+    port: parseInt(parts[1], 10),
+    protocol: parts[2],
+    fmt: parts.slice(3).join(' ')
+  };
+};
+
+SDPUtils.parseOLine = function(mediaSection) {
+  var line = SDPUtils.matchPrefix(mediaSection, 'o=')[0];
+  var parts = line.substr(2).split(' ');
+  return {
+    username: parts[0],
+    sessionId: parts[1],
+    sessionVersion: parseInt(parts[2], 10),
+    netType: parts[3],
+    addressType: parts[4],
+    address: parts[5]
+  };
+};
+
+// a very naive interpretation of a valid SDP.
+SDPUtils.isValidSDP = function(blob) {
+  if (typeof blob !== 'string' || blob.length === 0) {
+    return false;
+  }
+  var lines = SDPUtils.splitLines(blob);
+  for (var i = 0; i < lines.length; i++) {
+    if (lines[i].length < 2 || lines[i].charAt(1) !== '=') {
+      return false;
+    }
+    // TODO: check the modifier a bit more.
+  }
+  return true;
+};
+
+// Expose public methods.
+if (typeof module === 'object') {
+  module.exports = SDPUtils;
+}

From f0a9e8e3011f5046be20417aac977a3069d50f0a Mon Sep 17 00:00:00 2001
From: Philipp Hancke <philipp.hancke@googlemail.com>
Date: Tue, 31 Mar 2020 18:18:15 +0200
Subject: [PATCH 2/2] add readme

---
 webrtc/third_party/README.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 webrtc/third_party/README.md

diff --git a/webrtc/third_party/README.md b/webrtc/third_party/README.md
new file mode 100644
index 00000000000000..56a2295dd103db
--- /dev/null
+++ b/webrtc/third_party/README.md
@@ -0,0 +1,5 @@
+## sdp
+Third-party SDP module from
+  https://www.npmjs.com/package/sdp
+without tests or dependencies. See the commit message for version
+and commit information