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// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.net;
import java.net.*;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.stream.Collectors;
/**
* Utilities for returning localhost addresses on Linux.
* See
* http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4665037
* on why this is necessary.
*
* @author bratseth
*/
public class LinuxInetAddress {
/**
* Returns an InetAddress representing the address of the localhost.
* A non-loopback address is preferred if available.
* An address that resolves to a hostname is preferred among non-loopback addresses.
* IPv4 is preferred over IPv6 among resolving addresses.
*
* @return a localhost address
*/
public static InetAddress getLocalHost() {
System.out.println("Resolving local address");
InetAddress fallback = InetAddress.getLoopbackAddress();
try {
InetAddress localAddress = InetAddress.getLocalHost();
fallback = localAddress;
List<InetAddress> nonLoopback =
getAllLocalFromNetwork().stream().filter(a -> ! a.isLoopbackAddress()).collect(Collectors.toList());
if (nonLoopback.isEmpty()) {
System.out.println("Returning fallback 1: " + fallback);
return fallback;
}
fallback = nonLoopback.get(0);
List<InetAddress> resolving =
nonLoopback.stream().filter(a -> doesResolve(a)).collect(Collectors.toList());
if (resolving.isEmpty()) {
System.out.println("Returning fallback 2: " + fallback);
return fallback;
}
fallback = resolving.get(0);
List<InetAddress> ipV4 =
resolving.stream().filter(a -> a instanceof Inet4Address).collect(Collectors.toList());
if (ipV4.isEmpty()) {
System.out.println("Returning fallback 3: " + fallback);
return fallback;
}
System.out.println("Returning first ipv4, " + ipV4.get(0) + " among:");
for (InetAddress choice : ipV4)
System.out.println(" " + choice);
return ipV4.get(0);
} catch (UnknownHostException e) {
System.out.println("Returning fallback from exception " + e);
return fallback;
}
}
/**
* Returns all local addresses of this host.
*
* @return an array of the addresses of this
* @throws UnknownHostException if we cannot access the network
*/
public static InetAddress[] getAllLocal() throws UnknownHostException {
InetAddress[] localInetAddresses = InetAddress.getAllByName("127.0.0.1");
if ( ! localInetAddresses[0].isLoopbackAddress()) return localInetAddresses;
return getAllLocalFromNetwork().toArray(new InetAddress[0]);
}
/**
* Returns all local addresses of this host.
*
* @return a list of the addresses of this
* @throws UnknownHostException if we cannot access the network
*/
private static List<InetAddress> getAllLocalFromNetwork() throws UnknownHostException {
try {
List<InetAddress> addresses = new ArrayList<>();
for (NetworkInterface networkInterface : Collections.list(NetworkInterface.getNetworkInterfaces()))
addresses.addAll(Collections.list(networkInterface.getInetAddresses()));
return addresses;
}
catch (SocketException ex) {
throw new UnknownHostException("127.0.0.1");
}
}
private static boolean doesResolve(InetAddress addr) {
String asAddr = addr.getHostAddress();
String asName = addr.getCanonicalHostName();
return ! asAddr.equals(asName);
}
}
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