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     */
020    package org.sonar.process;
021    
022    import java.net.Inet4Address;
023    import java.net.InetAddress;
024    import java.net.NetworkInterface;
025    import java.net.SocketException;
026    import java.util.Enumeration;
027    
028    public class LoopbackAddress {
029    
030      private static 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    }