Source code

001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.reef.wake.remote;
020
021import org.apache.reef.wake.exception.WakeRuntimeException;
022
023import java.net.Inet4Address;
024import java.net.InetAddress;
025import java.net.NetworkInterface;
026import java.net.SocketException;
027import java.util.Comparator;
028import java.util.Enumeration;
029import java.util.TreeSet;
030import java.util.concurrent.atomic.AtomicReference;
031import java.util.logging.Level;
032import java.util.logging.Logger;
033
034public class NetUtils {
035  private static final Logger LOG = Logger.getLogger(NetUtils.class.getName());
036
037  private static AtomicReference<String> cached = new AtomicReference<>();
038
039  public static String getLocalAddress() {
040    // This method is surprisingly slow: It was causing unit test timeouts, so we memoize the result.
041    if (cached.get() == null) {
042      Enumeration<NetworkInterface> ifaces;
043      try {
044        ifaces = NetworkInterface.getNetworkInterfaces();
045        TreeSet<Inet4Address> sortedAddrs = new TreeSet<>(new AddressComparator());
046        // There is an idea of virtual / subinterfaces exposed by java here.
047        // We're not walking around looking for those because the javadoc says:
048
049        // "NOTE: can use getNetworkInterfaces()+getInetAddresses() to obtain all IP addresses for this node"
050
051        while (ifaces.hasMoreElements()) {
052          NetworkInterface iface = ifaces.nextElement();
053//          if(iface.isUp()) {  // leads to slowness and non-deterministic return values, so don't call isUp().
054          Enumeration<InetAddress> addrs = iface.getInetAddresses();
055          while (addrs.hasMoreElements()) {
056            InetAddress a = addrs.nextElement();
057            if (a instanceof Inet4Address) {
058              sortedAddrs.add((Inet4Address) a);
059            }
060//            }
061          }
062        }
063        if (sortedAddrs.isEmpty()) {
064          throw new WakeRuntimeException("This machine apparently doesn't have any IP addresses (not even 127.0.0.1) on interfaces that are up.");
065        }
066        cached.set(sortedAddrs.pollFirst().getHostAddress());
067        LOG.log(Level.FINE, "Local address is {0}", cached.get());
068      } catch (SocketException e) {
069        throw new WakeRuntimeException("Unable to get local host address",
070            e.getCause());
071      }
072    }
073    return cached.get();
074  }
075
076  private static class AddressComparator implements Comparator<Inet4Address> {
077
078    // get unsigned byte.
079    private static int u(byte b) {
080      return ((int) b);// & 0xff;
081    }
082
083    @Override
084    public int compare(Inet4Address aa, Inet4Address ba) {
085      byte[] a = aa.getAddress();
086      byte[] b = ba.getAddress();
087      // local subnet comes after all else.
088      if (a[0] == 127 && b[0] != 127) {
089        return 1;
090      }
091      if (a[0] != 127 && b[0] == 127) {
092        return -1;
093      }
094      for (int i = 0; i < 4; i++) {
095        if (u(a[i]) < u(b[i])) {
096          return -1;
097        }
098        if (u(a[i]) > u(b[i])) {
099          return 1;
100        }
101      }
102      return 0;
103    }
104  }
105
106}