Dactyloidae/netwerk/dns/mdns/libmdns/fallback/DNSResourceRecord.jsm

/* -*- Mode: js; js-indent-level: 2; indent-tabs-mode: nil; tab-width: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */
/* jshint esnext: true, moz: true */

'use strict';

this.EXPORTED_SYMBOLS = ['DNSResourceRecord'];

const { utils: Cu } = Components;

Cu.import('resource://gre/modules/Services.jsm');
Cu.import('resource://gre/modules/DataReader.jsm');
Cu.import('resource://gre/modules/DataWriter.jsm');
Cu.import('resource://gre/modules/DNSRecord.jsm');
Cu.import('resource://gre/modules/DNSTypes.jsm');

function debug(msg) {
  Services.console.logStringMessage('MulticastDNS: ' + msg);
}

const DNS_RESOURCE_RECORD_DEFAULT_TTL = 120; // 120 seconds

class DNSResourceRecord extends DNSRecord {
  constructor(properties = {}) {
    super(properties);

    this.ttl  = properties.ttl  || DNS_RESOURCE_RECORD_DEFAULT_TTL;
    this.data = properties.data || {};
  }

  static parseFromPacketReader(reader) {
    let record = super.parseFromPacketReader(reader);

    let ttl        = reader.getValue(4);
    let recordData = reader.getBytes(reader.getValue(2));
    let packetData = reader.data;

    let data;

    switch (record.recordType) {
      case DNS_RECORD_TYPES.A:
        data = _parseA(recordData, packetData);
        break;
      case DNS_RECORD_TYPES.PTR:
        data = _parsePTR(recordData, packetData);
        break;
      case DNS_RECORD_TYPES.TXT:
        data = _parseTXT(recordData, packetData);
        break;
      case DNS_RECORD_TYPES.SRV:
        data = _parseSRV(recordData, packetData);
        break;
      default:
        data = null;
        break;
    }

    record.ttl  = ttl;
    record.data = data;

    return record;
  }

  serialize() {
    let writer = new DataWriter(super.serialize());

    // Write `ttl` (4 bytes)
    writer.putValue(this.ttl, 4);

    let data;

    switch (this.recordType) {
      case DNS_RECORD_TYPES.A:
        data = _serializeA(this.data);
        break;
      case DNS_RECORD_TYPES.PTR:
        data = _serializePTR(this.data);
        break;
      case DNS_RECORD_TYPES.TXT:
        data = _serializeTXT(this.data);
        break;
      case DNS_RECORD_TYPES.SRV:
        data = _serializeSRV(this.data);
        break;
      default:
        data = new Uint8Array();
        break;
    }

    // Write `data` length.
    writer.putValue(data.length, 2);

    // Write `data` (ends with trailing 0x00 byte)
    writer.putBytes(data);

    return writer.data;
  }

  toJSON() {
    return JSON.stringify(this.toJSONObject());
  }

  toJSONObject() {
    let result = super.toJSONObject();
    result.ttl = this.ttl;
    result.data = this.data;
    return result;
  }
}

/**
 * @private
 */
function _parseA(recordData, packetData) {
  let reader = new DataReader(recordData);

  let parts = [];
  for (let i = 0; i < 4; i++) {
    parts.push(reader.getValue(1));
  }

  return parts.join('.');
}

/**
 * @private
 */
function _parsePTR(recordData, packetData) {
  let reader = new DataReader(recordData);

  return reader.getLabel(packetData);
}

/**
 * @private
 */
function _parseTXT(recordData, packetData) {
  let reader = new DataReader(recordData);

  let result = {};

  let label = reader.getLabel(packetData);
  if (label.length > 0) {
    let parts = label.split('.');
    parts.forEach((part) => {
      let [name] = part.split('=', 1);
      let value = part.substr(name.length + 1);
      result[name] = value;
    });
  }

  return result;
}

/**
 * @private
 */
function _parseSRV(recordData, packetData) {
  let reader = new DataReader(recordData);

  let priority = reader.getValue(2);
  let weight   = reader.getValue(2);
  let port     = reader.getValue(2);
  let target   = reader.getLabel(packetData);

  return { priority, weight, port, target };
}

/**
 * @private
 */
function _serializeA(data) {
  let writer = new DataWriter();

  let parts = data.split('.');
  for (let i = 0; i < 4; i++) {
    writer.putValue(parseInt(parts[i], 10) || 0);
  }

  return writer.data;
}

/**
 * @private
 */
function _serializePTR(data) {
  let writer = new DataWriter();

  writer.putLabel(data);

  return writer.data;
}

/**
 * @private
 */
function _serializeTXT(data) {
  let writer = new DataWriter();

  for (let name in data) {
    writer.putLengthString(name + '=' + data[name]);
  }

  return writer.data;
}

/**
 * @private
 */
function _serializeSRV(data) {
  let writer = new DataWriter();

  writer.putValue(data.priority || 0, 2);
  writer.putValue(data.weight   || 0, 2);
  writer.putValue(data.port     || 0, 2);
  writer.putLabel(data.target);

  return writer.data;
}