Minetrack/lib/dns.js

const dns = require("dns");

const logger = require("./logger");

const { TimeTracker } = require("./time");

const config = require("../config");

const SKIP_SRV_TIMEOUT = config.skipSrvTimeout || 60 * 60 * 1000;

class DNSResolver {
  constructor(ip, port) {
    this._ip = ip;
    this._port = port;
  }

  _skipSrv() {
    this._skipSrvUntil = TimeTracker.getEpochMillis() + SKIP_SRV_TIMEOUT;
  }

  _isSkipSrv() {
    return (
      this._skipSrvUntil && TimeTracker.getEpochMillis() <= this._skipSrvUntil
    );
  }

  resolve(callback) {
    if (this._isSkipSrv()) {
      callback(this._ip, this._port, config.rates.connectTimeout);

      return;
    }

    const startTime = TimeTracker.getEpochMillis();

    let callbackFired = false;

    const fireCallback = (ip, port) => {
      if (!callbackFired) {
        callbackFired = true;

        // Send currentTime - startTime to provide remaining connectionTime allowance
        const remainingTime =
          config.rates.connectTimeout -
          (TimeTracker.getEpochMillis() - startTime);

        callback(ip || this._ip, port || this._port, remainingTime);
      }
    };

    const timeoutCallback = setTimeout(
      fireCallback,
      config.rates.connectTimeout
    );

    dns.resolveSrv("_minecraft._tcp." + this._ip, (err, records) => {
      // Cancel the timeout handler if not already fired
      if (!callbackFired) {
        clearTimeout(timeoutCallback);
      }

      // Test if the error indicates a miss, or if the records returned are empty
      if (
        (err && (err.code === "ENOTFOUND" || err.code === "ENODATA")) ||
        !records ||
        records.length === 0
      ) {
        // Compare config.skipSrvTimeout directly since SKIP_SRV_TIMEOUT has an or'd value
        // isSkipSrvTimeoutDisabled == whether the config has a valid skipSrvTimeout value set
        const isSkipSrvTimeoutDisabled =
          typeof config.skipSrvTimeout === "number" &&
          config.skipSrvTimeout === 0;

        // Only activate _skipSrv if the skipSrvTimeout value is either NaN or > 0
        // 0 represents a disabled flag
        if (!this._isSkipSrv() && !isSkipSrvTimeoutDisabled) {
          this._skipSrv();

          logger.log(
            "warn",
            "No SRV records were resolved for %s. Minetrack will skip attempting to resolve %s SRV records for %d minutes.",
            this._ip,
            this._ip,
            SKIP_SRV_TIMEOUT / (60 * 1000)
          );
        }

        fireCallback();
      } else {
        // Only fires if !err && records.length > 0
        fireCallback(records[0].name, records[0].port);
      }
    });
  }
}

module.exports = DNSResolver;