001/*
002 * SonarQube, open source software quality management tool.
003 * Copyright (C) 2008-2014 SonarSource
004 * mailto:contact AT sonarsource DOT com
005 *
006 * SonarQube is free software; you can redistribute it and/or
007 * modify it under the terms of the GNU Lesser General Public
008 * License as published by the Free Software Foundation; either
009 * version 3 of the License, or (at your option) any later version.
010 *
011 * SonarQube is distributed in the hope that it will be useful,
012 * but WITHOUT ANY WARRANTY; without even the implied warranty of
013 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014 * Lesser General Public License for more details.
015 *
016 * You should have received a copy of the GNU Lesser General Public License
017 * along with this program; if not, write to the Free Software Foundation,
018 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
019 */
020package org.sonar.process;
021
022import java.net.Inet4Address;
023import java.net.InetAddress;
024import java.net.NetworkInterface;
025import java.net.SocketException;
026import java.util.Enumeration;
027
028public class LoopbackAddress {
029
030  private static volatile InetAddress instance;
031
032  private LoopbackAddress() {
033    // only static stuff
034  }
035
036  /**
037   * Quite similar to {@code InetAddress.getLoopbackAddress()} which was introduced in Java 7. This
038   * method aims to support Java 6. It returns an IPv4 address, but not IPv6 in order to
039   * support {@code -Djava.net.preferIPv4Stack=true} which is recommended for Elasticsearch.
040   */
041  public static InetAddress get() {
042    if (instance == null) {
043      try {
044        instance = doGet(NetworkInterface.getNetworkInterfaces());
045      } catch (SocketException e) {
046        throw new IllegalStateException("Fail to browse network interfaces", e);
047      }
048
049    }
050    return instance;
051  }
052
053  static InetAddress doGet(Enumeration<NetworkInterface> ifaces) {
054    InetAddress result = null;
055    while (ifaces.hasMoreElements() && result == null) {
056      NetworkInterface iface = ifaces.nextElement();
057      Enumeration<InetAddress> addresses = iface.getInetAddresses();
058      while (addresses.hasMoreElements()) {
059        InetAddress addr = addresses.nextElement();
060        if (addr.isLoopbackAddress() && addr instanceof Inet4Address) {
061          result = addr;
062          break;
063        }
064      }
065    }
066    if (result == null) {
067      throw new IllegalStateException("Impossible to get a IPv4 loopback address");
068    }
069    return result;
070  }
071}