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 * Copyright (c) 1995, 2018, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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package java.net;

import java.util.NavigableSet;
import java.util.ArrayList;
import java.util.Objects;
import java.util.Scanner;
import java.security.AccessController;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.ObjectStreamException;
import java.io.ObjectStreamField;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectInputStream.GetField;
import java.io.ObjectOutputStream;
import java.io.ObjectOutputStream.PutField;
import java.lang.annotation.Native;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ConcurrentSkipListSet;
import java.util.concurrent.atomic.AtomicLong;

import jdk.internal.misc.JavaNetInetAddressAccess;
import jdk.internal.misc.SharedSecrets;
import sun.security.action.*;
import sun.net.InetAddressCachePolicy;
import sun.net.util.IPAddressUtil;

/**
 * This class represents an Internet Protocol (IP) address.
 *
 * <p> An IP address is either a 32-bit or 128-bit unsigned number
 * used by IP, a lower-level protocol on which protocols like UDP and
 * TCP are built. The IP address architecture is defined by <a
 * href="http://www.ietf.org/rfc/rfc790.txt"><i>RFC&nbsp;790:
 * Assigned Numbers</i></a>, <a
 * href="http://www.ietf.org/rfc/rfc1918.txt"> <i>RFC&nbsp;1918:
 * Address Allocation for Private Internets</i></a>, <a
 * href="http://www.ietf.org/rfc/rfc2365.txt"><i>RFC&nbsp;2365:
 * Administratively Scoped IP Multicast</i></a>, and <a
 * href="http://www.ietf.org/rfc/rfc2373.txt"><i>RFC&nbsp;2373: IP
 * Version 6 Addressing Architecture</i></a>. An instance of an
 * InetAddress consists of an IP address and possibly its
 * corresponding host name (depending on whether it is constructed
 * with a host name or whether it has already done reverse host name
 * resolution).
 *
 * <h3> Address types </h3>
 *
 * <table class="striped" style="margin-left:2em">
 * <caption style="display:none">Description of unicast and multicast address types</caption>
 * <thead>
 * <tr><th scope="col">Address Type</th><th scope="col">Description</th></tr>
 * </thead>
 * <tbody>
 * <tr><th scope="row" style="vertical-align:top">unicast</th>
 * <td>An identifier for a single interface. A packet sent to
 * a unicast address is delivered to the interface identified by
 * that address.
 *
 * <p> The Unspecified Address -- Also called anylocal or wildcard
 * address. It must never be assigned to any node. It indicates the
 * absence of an address. One example of its use is as the target of
 * bind, which allows a server to accept a client connection on any
 * interface, in case the server host has multiple interfaces.
 *
 * <p> The <i>unspecified</i> address must not be used as
 * the destination address of an IP packet.
 *
 * <p> The <i>Loopback</i> Addresses -- This is the address
 * assigned to the loopback interface. Anything sent to this
 * IP address loops around and becomes IP input on the local
 * host. This address is often used when testing a
 * client.</td></tr>
 * <tr><th scope="row" style="vertical-align:top">multicast</th>
 * <td>An identifier for a set of interfaces (typically belonging
 * to different nodes). A packet sent to a multicast address is
 * delivered to all interfaces identified by that address.</td></tr>
 * </tbody>
 * </table>
 *
 * <h4> IP address scope </h4>
 *
 * <p> <i>Link-local</i> addresses are designed to be used for addressing
 * on a single link for purposes such as auto-address configuration,
 * neighbor discovery, or when no routers are present.
 *
 * <p> <i>Site-local</i> addresses are designed to be used for addressing
 * inside of a site without the need for a global prefix.
 *
 * <p> <i>Global</i> addresses are unique across the internet.
 *
 * <h4> Textual representation of IP addresses </h4>
 *
 * The textual representation of an IP address is address family specific.
 *
 * <p>
 *
 * For IPv4 address format, please refer to <A
 * HREF="Inet4Address.html#format">Inet4Address#format</A>; For IPv6
 * address format, please refer to <A
 * HREF="Inet6Address.html#format">Inet6Address#format</A>.
 *
 * <P>There is a <a href="doc-files/net-properties.html#Ipv4IPv6">couple of
 * System Properties</a> affecting how IPv4 and IPv6 addresses are used.</P>
 *
 * <h4> Host Name Resolution </h4>
 *
 * Host name-to-IP address <i>resolution</i> is accomplished through
 * the use of a combination of local machine configuration information
 * and network naming services such as the Domain Name System (DNS)
 * and Network Information Service(NIS). The particular naming
 * services(s) being used is by default the local machine configured
 * one. For any host name, its corresponding IP address is returned.
 *
 * <p> <i>Reverse name resolution</i> means that for any IP address,
 * the host associated with the IP address is returned.
 *
 * <p> The InetAddress class provides methods to resolve host names to
 * their IP addresses and vice versa.
 *
 * <h4> InetAddress Caching </h4>
 *
 * The InetAddress class has a cache to store successful as well as
 * unsuccessful host name resolutions.
 *
 * <p> By default, when a security manager is installed, in order to
 * protect against DNS spoofing attacks,
 * the result of positive host name resolutions are
 * cached forever. When a security manager is not installed, the default
 * behavior is to cache entries for a finite (implementation dependent)
 * period of time. The result of unsuccessful host
 * name resolution is cached for a very short period of time (10
 * seconds) to improve performance.
 *
 * <p> If the default behavior is not desired, then a Java security property
 * can be set to a different Time-to-live (TTL) value for positive
 * caching. Likewise, a system admin can configure a different
 * negative caching TTL value when needed.
 *
 * <p> Two Java security properties control the TTL values used for
 * positive and negative host name resolution caching:
 *
 * <dl style="margin-left:2em">
 * <dt><b>networkaddress.cache.ttl</b></dt>
 * <dd>Indicates the caching policy for successful name lookups from
 * the name service. The value is specified as an integer to indicate
 * the number of seconds to cache the successful lookup. The default
 * setting is to cache for an implementation specific period of time.
 * <p>
 * A value of -1 indicates "cache forever".
 * </dd>
 * <dt><b>networkaddress.cache.negative.ttl</b> (default: 10)</dt>
 * <dd>Indicates the caching policy for un-successful name lookups
 * from the name service. The value is specified as an integer to
 * indicate the number of seconds to cache the failure for
 * un-successful lookups.
 * <p>
 * A value of 0 indicates "never cache".
 * A value of -1 indicates "cache forever".
 * </dd>
 * </dl>
 *
 * @author Chris Warth
 * @see java.net.InetAddress#getByAddress(byte[])
 * @see java.net.InetAddress#getByAddress(java.lang.String, byte[])
 * @see java.net.InetAddress#getAllByName(java.lang.String)
 * @see java.net.InetAddress#getByName(java.lang.String)
 * @see java.net.InetAddress#getLocalHost()
 * @since 1.0
 */
public
class InetAddress implements java.io.Serializable {

 @Native static final int PREFER_IPV4_VALUE = 0;
 @Native static final int PREFER_IPV6_VALUE = 1;
 @Native static final int PREFER_SYSTEM_VALUE = 2;

 /**
 * Specify the address family: Internet Protocol, Version 4
 * @since 1.4
 */
 @Native static final int IPv4 = 1;

 /**
 * Specify the address family: Internet Protocol, Version 6
 * @since 1.4
 */
 @Native static final int IPv6 = 2;

 /* Specify address family preference */
 static transient final int preferIPv6Address;

 static class InetAddressHolder {
 /**
 * Reserve the original application specified hostname.
 *
 * The original hostname is useful for domain-based endpoint
 * identification (see RFC 2818 and RFC 6125). If an address
 * was created with a raw IP address, a reverse name lookup
 * may introduce endpoint identification security issue via
 * DNS forging.
 *
 * Oracle JSSE provider is using this original hostname, via
 * jdk.internal.misc.JavaNetAccess, for SSL/TLS endpoint identification.
 *
 * Note: May define a new public method in the future if necessary.
 */
 String originalHostName;

 InetAddressHolder() {}

 InetAddressHolder(String hostName, int address, int family) {
 this.originalHostName = hostName;
 this.hostName = hostName;
 this.address = address;
 this.family = family;
 }

 void init(String hostName, int family) {
 this.originalHostName = hostName;
 this.hostName = hostName;
 if (family != -1) {
 this.family = family;
 }
 }

 String hostName;

 String getHostName() {
 return hostName;
 }

 String getOriginalHostName() {
 return originalHostName;
 }

 /**
 * Holds a 32-bit IPv4 address.
 */
 int address;

 int getAddress() {
 return address;
 }

 /**
 * Specifies the address family type, for instance, '1' for IPv4
 * addresses, and '2' for IPv6 addresses.
 */
 int family;

 int getFamily() {
 return family;
 }
 }

 /* Used to store the serializable fields of InetAddress */
 final transient InetAddressHolder holder;

 InetAddressHolder holder() {
 return holder;
 }

 /* Used to store the name service provider */
 private static transient NameService nameService = null;

 /**
 * Used to store the best available hostname.
 * Lazily initialized via a data race; safe because Strings are immutable.
 */
 private transient String canonicalHostName = null;

 /** use serialVersionUID from JDK 1.0.2 for interoperability */
 private static final long serialVersionUID = 3286316764910316507L;

 /*
 * Load net library into runtime, and perform initializations.
 */
 static {
 String str = java.security.AccessController.doPrivileged(
 new GetPropertyAction("java.net.preferIPv6Addresses"));
 if (str == null) {
 preferIPv6Address = PREFER_IPV4_VALUE;
 } else if (str.equalsIgnoreCase("true")) {
 preferIPv6Address = PREFER_IPV6_VALUE;
 } else if (str.equalsIgnoreCase("false")) {
 preferIPv6Address = PREFER_IPV4_VALUE;
 } else if (str.equalsIgnoreCase("system")) {
 preferIPv6Address = PREFER_SYSTEM_VALUE;
 } else {
 preferIPv6Address = PREFER_IPV4_VALUE;
 }
 AccessController.doPrivileged(
 new java.security.PrivilegedAction<>() {
 public Void run() {
 System.loadLibrary("net");
 return null;
 }
 });
 SharedSecrets.setJavaNetInetAddressAccess(
 new JavaNetInetAddressAccess() {
 public String getOriginalHostName(InetAddress ia) {
 return ia.holder.getOriginalHostName();
 }

 public InetAddress getByName(String hostName,
 InetAddress hostAddress)
 throws UnknownHostException
 {
 return InetAddress.getByName(hostName, hostAddress);
 }
 }
 );
 init();
 }

 /**
 * Constructor for the Socket.accept() method.
 * This creates an empty InetAddress, which is filled in by
 * the accept() method. This InetAddress, however, is not
 * put in the address cache, since it is not created by name.
 */
 InetAddress() {
 holder = new InetAddressHolder();
 }

 /**
 * Replaces the de-serialized object with an Inet4Address object.
 *
 * @return the alternate object to the de-serialized object.
 *
 * @throws ObjectStreamException if a new object replacing this
 * object could not be created
 */
 private Object readResolve() throws ObjectStreamException {
 // will replace the deserialized 'this' object
 return new Inet4Address(holder().getHostName(), holder().getAddress());
 }

 /**
 * Utility routine to check if the InetAddress is an
 * IP multicast address.
 * @return a {@code boolean} indicating if the InetAddress is
 * an IP multicast address
 * @since 1.1
 */
 public boolean isMulticastAddress() {
 return false;
 }

 /**
 * Utility routine to check if the InetAddress is a wildcard address.
 * @return a {@code boolean} indicating if the Inetaddress is
 * a wildcard address.
 * @since 1.4
 */
 public boolean isAnyLocalAddress() {
 return false;
 }

 /**
 * Utility routine to check if the InetAddress is a loopback address.
 *
 * @return a {@code boolean} indicating if the InetAddress is
 * a loopback address; or false otherwise.
 * @since 1.4
 */
 public boolean isLoopbackAddress() {
 return false;
 }

 /**
 * Utility routine to check if the InetAddress is an link local address.
 *
 * @return a {@code boolean} indicating if the InetAddress is
 * a link local address; or false if address is not a link local unicast address.
 * @since 1.4
 */
 public boolean isLinkLocalAddress() {
 return false;
 }

 /**
 * Utility routine to check if the InetAddress is a site local address.
 *
 * @return a {@code boolean} indicating if the InetAddress is
 * a site local address; or false if address is not a site local unicast address.
 * @since 1.4
 */
 public boolean isSiteLocalAddress() {
 return false;
 }

 /**
 * Utility routine to check if the multicast address has global scope.
 *
 * @return a {@code boolean} indicating if the address has
 * is a multicast address of global scope, false if it is not
 * of global scope or it is not a multicast address
 * @since 1.4
 */
 public boolean isMCGlobal() {
 return false;
 }

 /**
 * Utility routine to check if the multicast address has node scope.
 *
 * @return a {@code boolean} indicating if the address has
 * is a multicast address of node-local scope, false if it is not
 * of node-local scope or it is not a multicast address
 * @since 1.4
 */
 public boolean isMCNodeLocal() {
 return false;
 }

 /**
 * Utility routine to check if the multicast address has link scope.
 *
 * @return a {@code boolean} indicating if the address has
 * is a multicast address of link-local scope, false if it is not
 * of link-local scope or it is not a multicast address
 * @since 1.4
 */
 public boolean isMCLinkLocal() {
 return false;
 }

 /**
 * Utility routine to check if the multicast address has site scope.
 *
 * @return a {@code boolean} indicating if the address has
 * is a multicast address of site-local scope, false if it is not
 * of site-local scope or it is not a multicast address
 * @since 1.4
 */
 public boolean isMCSiteLocal() {
 return false;
 }

 /**
 * Utility routine to check if the multicast address has organization scope.
 *
 * @return a {@code boolean} indicating if the address has
 * is a multicast address of organization-local scope,
 * false if it is not of organization-local scope
 * or it is not a multicast address
 * @since 1.4
 */
 public boolean isMCOrgLocal() {
 return false;
 }


 /**
 * Test whether that address is reachable. Best effort is made by the
 * implementation to try to reach the host, but firewalls and server
 * configuration may block requests resulting in a unreachable status
 * while some specific ports may be accessible.
 * A typical implementation will use ICMP ECHO REQUESTs if the
 * privilege can be obtained, otherwise it will try to establish
 * a TCP connection on port 7 (Echo) of the destination host.
 * <p>
 * The timeout value, in milliseconds, indicates the maximum amount of time
 * the try should take. If the operation times out before getting an
 * answer, the host is deemed unreachable. A negative value will result
 * in an IllegalArgumentException being thrown.
 *
 * @param timeout the time, in milliseconds, before the call aborts
 * @return a {@code boolean} indicating if the address is reachable.
 * @throws IOException if a network error occurs
 * @throws IllegalArgumentException if {@code timeout} is negative.
 * @since 1.5
 */
 public boolean isReachable(int timeout) throws IOException {
 return isReachable(null, 0 , timeout);
 }

 /**
 * Test whether that address is reachable. Best effort is made by the
 * implementation to try to reach the host, but firewalls and server
 * configuration may block requests resulting in a unreachable status
 * while some specific ports may be accessible.
 * A typical implementation will use ICMP ECHO REQUESTs if the
 * privilege can be obtained, otherwise it will try to establish
 * a TCP connection on port 7 (Echo) of the destination host.
 * <p>
 * The {@code network interface} and {@code ttl} parameters
 * let the caller specify which network interface the test will go through
 * and the maximum number of hops the packets should go through.
 * A negative value for the {@code ttl} will result in an
 * IllegalArgumentException being thrown.
 * <p>
 * The timeout value, in milliseconds, indicates the maximum amount of time
 * the try should take. If the operation times out before getting an
 * answer, the host is deemed unreachable. A negative value will result
 * in an IllegalArgumentException being thrown.
 *
 * @param netif the NetworkInterface through which the
 * test will be done, or null for any interface
 * @param ttl the maximum numbers of hops to try or 0 for the
 * default
 * @param timeout the time, in milliseconds, before the call aborts
 * @throws IllegalArgumentException if either {@code timeout}
 * or {@code ttl} are negative.
 * @return a {@code boolean}indicating if the address is reachable.
 * @throws IOException if a network error occurs
 * @since 1.5
 */
 public boolean isReachable(NetworkInterface netif, int ttl,
 int timeout) throws IOException {
 if (ttl < 0)
 throw new IllegalArgumentException("ttl can't be negative");
 if (timeout < 0)
 throw new IllegalArgumentException("timeout can't be negative");

 return impl.isReachable(this, timeout, netif, ttl);
 }

 /**
 * Gets the host name for this IP address.
 *
 * <p>If this InetAddress was created with a host name,
 * this host name will be remembered and returned;
 * otherwise, a reverse name lookup will be performed
 * and the result will be returned based on the system
 * configured name lookup service. If a lookup of the name service
 * is required, call
 * {@link #getCanonicalHostName() getCanonicalHostName}.
 *
 * <p>If there is a security manager, its
 * {@code checkConnect} method is first called
 * with the hostname and {@code -1}
 * as its arguments to see if the operation is allowed.
 * If the operation is not allowed, it will return
 * the textual representation of the IP address.
 *
 * @return the host name for this IP address, or if the operation
 * is not allowed by the security check, the textual
 * representation of the IP address.
 *
 * @see InetAddress#getCanonicalHostName
 * @see SecurityManager#checkConnect
 */
 public String getHostName() {
 return getHostName(true);
 }

 /**
 * Returns the hostname for this address.
 * If the host is equal to null, then this address refers to any
 * of the local machine's available network addresses.
 * this is package private so SocketPermission can make calls into
 * here without a security check.
 *
 * <p>If there is a security manager, this method first
 * calls its {@code checkConnect} method
 * with the hostname and {@code -1}
 * as its arguments to see if the calling code is allowed to know
 * the hostname for this IP address, i.e., to connect to the host.
 * If the operation is not allowed, it will return
 * the textual representation of the IP address.
 *
 * @return the host name for this IP address, or if the operation
 * is not allowed by the security check, the textual
 * representation of the IP address.
 *
 * @param check make security check if true
 *
 * @see SecurityManager#checkConnect
 */
 String getHostName(boolean check) {
 if (holder().getHostName() == null) {
 holder().hostName = InetAddress.getHostFromNameService(this, check);
 }
 return holder().getHostName();
 }

 /**
 * Gets the fully qualified domain name for this IP address.
 * Best effort method, meaning we may not be able to return
 * the FQDN depending on the underlying system configuration.
 *
 * <p>If there is a security manager, this method first
 * calls its {@code checkConnect} method
 * with the hostname and {@code -1}
 * as its arguments to see if the calling code is allowed to know
 * the hostname for this IP address, i.e., to connect to the host.
 * If the operation is not allowed, it will return
 * the textual representation of the IP address.
 *
 * @return the fully qualified domain name for this IP address,
 * or if the operation is not allowed by the security check,
 * the textual representation of the IP address.
 *
 * @see SecurityManager#checkConnect
 *
 * @since 1.4
 */
 public String getCanonicalHostName() {
 String value = canonicalHostName;
 if (value == null)
 canonicalHostName = value =
 InetAddress.getHostFromNameService(this, true);
 return value;
 }

 /**
 * Returns the hostname for this address.
 *
 * <p>If there is a security manager, this method first
 * calls its {@code checkConnect} method
 * with the hostname and {@code -1}
 * as its arguments to see if the calling code is allowed to know
 * the hostname for this IP address, i.e., to connect to the host.
 * If the operation is not allowed, it will return
 * the textual representation of the IP address.
 *
 * @return the host name for this IP address, or if the operation
 * is not allowed by the security check, the textual
 * representation of the IP address.
 *
 * @param check make security check if true
 *
 * @see SecurityManager#checkConnect
 */
 private static String getHostFromNameService(InetAddress addr, boolean check) {
 String host = null;
 try {
 // first lookup the hostname
 host = nameService.getHostByAddr(addr.getAddress());

 /* check to see if calling code is allowed to know
 * the hostname for this IP address, ie, connect to the host
 */
 if (check) {
 SecurityManager sec = System.getSecurityManager();
 if (sec != null) {
 sec.checkConnect(host, -1);
 }
 }

 /* now get all the IP addresses for this hostname,
 * and make sure one of them matches the original IP
 * address. We do this to try and prevent spoofing.
 */

 InetAddress[] arr = InetAddress.getAllByName0(host, check);
 boolean ok = false;

 if(arr != null) {
 for(int i = 0; !ok && i < arr.length; i++) {
 ok = addr.equals(arr[i]);
 }
 }

 //XXX: if it looks a spoof just return the address?
 if (!ok) {
 host = addr.getHostAddress();
 return host;
 }
 } catch (SecurityException e) {
 host = addr.getHostAddress();
 } catch (UnknownHostException e) {
 host = addr.getHostAddress();
 // let next provider resolve the hostname
 }
 return host;
 }

 /**
 * Returns the raw IP address of this {@code InetAddress}
 * object. The result is in network byte order: the highest order
 * byte of the address is in {@code getAddress()[0]}.
 *
 * @return the raw IP address of this object.
 */
 public byte[] getAddress() {
 return null;
 }

 /**
 * Returns the IP address string in textual presentation.
 *
 * @return the raw IP address in a string format.
 * @since 1.0.2
 */
 public String getHostAddress() {
 return null;
 }

 /**
 * Returns a hashcode for this IP address.
 *
 * @return a hash code value for this IP address.
 */
 public int hashCode() {
 return -1;
 }

 /**
 * Compares this object against the specified object.
 * The result is {@code true} if and only if the argument is
 * not {@code null} and it represents the same IP address as
 * this object.
 * <p>
 * Two instances of {@code InetAddress} represent the same IP
 * address if the length of the byte arrays returned by
 * {@code getAddress} is the same for both, and each of the
 * array components is the same for the byte arrays.
 *
 * @param obj the object to compare against.
 * @return {@code true} if the objects are the same;
 * {@code false} otherwise.
 * @see java.net.InetAddress#getAddress()
 */
 public boolean equals(Object obj) {
 return false;
 }

 /**
 * Converts this IP address to a {@code String}. The
 * string returned is of the form: hostname / literal IP
 * address.
 *
 * If the host name is unresolved, no reverse name service lookup
 * is performed. The hostname part will be represented by an empty string.
 *
 * @return a string representation of this IP address.
 */
 public String toString() {
 String hostName = holder().getHostName();
 return Objects.toString(hostName, "")
 + "/" + getHostAddress();
 }

 // mapping from host name to Addresses - either NameServiceAddresses (while
 // still being looked-up by NameService(s)) or CachedAddresses when cached
 private static final ConcurrentMap<String, Addresses> cache =
 new ConcurrentHashMap<>();

 // CachedAddresses that have to expire are kept ordered in this NavigableSet
 // which is scanned on each access
 private static final NavigableSet<CachedAddresses> expirySet =
 new ConcurrentSkipListSet<>();

 // common interface
 private interface Addresses {
 InetAddress[] get() throws UnknownHostException;
 }

 // a holder for cached addresses with required metadata
 private static final class CachedAddresses implements Addresses, Comparable<CachedAddresses> {
 private static final AtomicLong seq = new AtomicLong();
 final String host;
 final InetAddress[] inetAddresses;
 final long expiryTime; // time of expiry (in terms of System.nanoTime())
 final long id = seq.incrementAndGet(); // each instance is unique

 CachedAddresses(String host, InetAddress[] inetAddresses, long expiryTime) {
 this.host = host;
 this.inetAddresses = inetAddresses;
 this.expiryTime = expiryTime;
 }

 @Override
 public InetAddress[] get() throws UnknownHostException {
 if (inetAddresses == null) {
 throw new UnknownHostException(host);
 }
 return inetAddresses;
 }

 @Override
 public int compareTo(CachedAddresses other) {
 // natural order is expiry time -
 // compare difference of expiry times rather than
 // expiry times directly, to avoid possible overflow.
 // (see System.nanoTime() recommendations...)
 long diff = this.expiryTime - other.expiryTime;
 if (diff < 0L) return -1;
 if (diff > 0L) return 1;
 // ties are broken using unique id
 return Long.compare(this.id, other.id);
 }
 }

 // a name service lookup based Addresses implementation which replaces itself
 // in cache when the result is obtained
 private static final class NameServiceAddresses implements Addresses {
 private final String host;
 private final InetAddress reqAddr;

 NameServiceAddresses(String host, InetAddress reqAddr) {
 this.host = host;
 this.reqAddr = reqAddr;
 }

 @Override
 public InetAddress[] get() throws UnknownHostException {
 Addresses addresses;
 // only one thread is doing lookup to name service
 // for particular host at any time.
 synchronized (this) {
 // re-check that we are still us + re-install us if slot empty
 addresses = cache.putIfAbsent(host, this);
 if (addresses == null) {
 // this can happen when we were replaced by CachedAddresses in
 // some other thread, then CachedAddresses expired and were
 // removed from cache while we were waiting for lock...
 addresses = this;
 }
 // still us ?
 if (addresses == this) {
 // lookup name services
 InetAddress[] inetAddresses;
 UnknownHostException ex;
 int cachePolicy;
 try {
 inetAddresses = getAddressesFromNameService(host, reqAddr);
 ex = null;
 cachePolicy = InetAddressCachePolicy.get();
 } catch (UnknownHostException uhe) {
 inetAddresses = null;
 ex = uhe;
 cachePolicy = InetAddressCachePolicy.getNegative();
 }
 // remove or replace us with cached addresses according to cachePolicy
 if (cachePolicy == InetAddressCachePolicy.NEVER) {
 cache.remove(host, this);
 } else {
 CachedAddresses cachedAddresses = new CachedAddresses(
 host,
 inetAddresses,
 cachePolicy == InetAddressCachePolicy.FOREVER
 ? 0L
 // cachePolicy is in [s] - we need [ns]
 : System.nanoTime() + 1000_000_000L * cachePolicy
 );
 if (cache.replace(host, this, cachedAddresses) &&
 cachePolicy != InetAddressCachePolicy.FOREVER) {
 // schedule expiry
 expirySet.add(cachedAddresses);
 }
 }
 if (inetAddresses == null) {
 throw ex == null ? new UnknownHostException(host) : ex;
 }
 return inetAddresses;
 }
 // else addresses != this
 }
 // delegate to different addresses when we are already replaced
 // but outside of synchronized block to avoid any chance of dead-locking
 return addresses.get();
 }
 }

 /**
 * NameService provides host and address lookup service
 *
 * @since 9
 */
 private interface NameService {

 /**
 * Lookup a host mapping by name. Retrieve the IP addresses
 * associated with a host
 *
 * @param host the specified hostname
 * @return array of IP addresses for the requested host
 * @throws UnknownHostException
 * if no IP address for the {@code host} could be found
 */
 InetAddress[] lookupAllHostAddr(String host)
 throws UnknownHostException;

 /**
 * Lookup the host corresponding to the IP address provided
 *
 * @param addr byte array representing an IP address
 * @return {@code String} representing the host name mapping
 * @throws UnknownHostException
 * if no host found for the specified IP address
 */
 String getHostByAddr(byte[] addr) throws UnknownHostException;

 }

 /**
 * The default NameService implementation, which delegates to the underlying
 * OS network libraries to resolve host address mappings.
 *
 * @since 9
 */
 private static final class PlatformNameService implements NameService {

 public InetAddress[] lookupAllHostAddr(String host)
 throws UnknownHostException
 {
 return impl.lookupAllHostAddr(host);
 }

 public String getHostByAddr(byte[] addr)
 throws UnknownHostException
 {
 return impl.getHostByAddr(addr);
 }
 }

 /**
 * The HostsFileNameService provides host address mapping
 * by reading the entries in a hosts file, which is specified by
 * {@code jdk.net.hosts.file} system property
 *
 * <p>The file format is that which corresponds with the /etc/hosts file
 * IP Address host alias list.
 *
 * <p>When the file lookup is enabled it replaces the default NameService
 * implementation
 *
 * @since 9
 */
 private static final class HostsFileNameService implements NameService {

 private final String hostsFile;

 public HostsFileNameService (String hostsFileName) {
 this.hostsFile = hostsFileName;
 }

 private String addrToString(byte addr[]) {
 String stringifiedAddress = null;

 if (addr.length == Inet4Address.INADDRSZ) {
 stringifiedAddress = Inet4Address.numericToTextFormat(addr);
 } else { // treat as an IPV6 jobby
 byte[] newAddr
 = IPAddressUtil.convertFromIPv4MappedAddress(addr);
 if (newAddr != null) {
 stringifiedAddress = Inet4Address.numericToTextFormat(addr);
 } else {
 stringifiedAddress = Inet6Address.numericToTextFormat(addr);
 }
 }
 return stringifiedAddress;
 }

 /**
 * Lookup the host name corresponding to the IP address provided.
 * Search the configured host file a host name corresponding to
 * the specified IP address.
 *
 * @param addr byte array representing an IP address
 * @return {@code String} representing the host name mapping
 * @throws UnknownHostException
 * if no host found for the specified IP address
 */
 @Override
 public String getHostByAddr(byte[] addr) throws UnknownHostException {
 String hostEntry;
 String host = null;

 String addrString = addrToString(addr);
 try (Scanner hostsFileScanner = new Scanner(new File(hostsFile), "UTF-8")) {
 while (hostsFileScanner.hasNextLine()) {
 hostEntry = hostsFileScanner.nextLine();
 if (!hostEntry.startsWith("#")) {
 hostEntry = removeComments(hostEntry);
 if (hostEntry.contains(addrString)) {
 host = extractHost(hostEntry, addrString);
 if (host != null) {
 break;
 }
 }
 }
 }
 } catch (FileNotFoundException e) {
 throw new UnknownHostException("Unable to resolve address "
 + addrString + " as hosts file " + hostsFile
 + " not found ");
 }

 if ((host == null) || (host.equals("")) || (host.equals(" "))) {
 throw new UnknownHostException("Requested address "
 + addrString
 + " resolves to an invalid entry in hosts file "
 + hostsFile);
 }
 return host;
 }

 /**
 * <p>Lookup a host mapping by name. Retrieve the IP addresses
 * associated with a host.
 *
 * <p>Search the configured hosts file for the addresses assocaited with
 * with the specified host name.
 *
 * @param host the specified hostname
 * @return array of IP addresses for the requested host
 * @throws UnknownHostException
 * if no IP address for the {@code host} could be found
 */
 public InetAddress[] lookupAllHostAddr(String host)
 throws UnknownHostException {
 String hostEntry;
 String addrStr = null;
 InetAddress[] res = null;
 byte addr[] = new byte[4];
 ArrayList<InetAddress> inetAddresses = null;

 // lookup the file and create a list InetAddress for the specfied host
 try (Scanner hostsFileScanner = new Scanner(new File(hostsFile), "UTF-8")) {
 while (hostsFileScanner.hasNextLine()) {
 hostEntry = hostsFileScanner.nextLine();
 if (!hostEntry.startsWith("#")) {
 hostEntry = removeComments(hostEntry);
 if (hostEntry.contains(host)) {
 addrStr = extractHostAddr(hostEntry, host);
 if ((addrStr != null) && (!addrStr.equals(""))) {
 addr = createAddressByteArray(addrStr);
 if (inetAddresses == null) {
 inetAddresses = new ArrayList<>(1);
 }
 if (addr != null) {
 inetAddresses.add(InetAddress.getByAddress(host, addr));
 }
 }
 }
 }
 }
 } catch (FileNotFoundException e) {
 throw new UnknownHostException("Unable to resolve host " + host
 + " as hosts file " + hostsFile + " not found ");
 }

 if (inetAddresses != null) {
 res = inetAddresses.toArray(new InetAddress[inetAddresses.size()]);
 } else {
 throw new UnknownHostException("Unable to resolve host " + host
 + " in hosts file " + hostsFile);
 }
 return res;
 }

 private String removeComments(String hostsEntry) {
 String filteredEntry = hostsEntry;
 int hashIndex;

 if ((hashIndex = hostsEntry.indexOf("#")) != -1) {
 filteredEntry = hostsEntry.substring(0, hashIndex);
 }
 return filteredEntry;
 }

 private byte [] createAddressByteArray(String addrStr) {
 byte[] addrArray;
 // check if IPV4 address - most likely
 addrArray = IPAddressUtil.textToNumericFormatV4(addrStr);
 if (addrArray == null) {
 addrArray = IPAddressUtil.textToNumericFormatV6(addrStr);
 }
 return addrArray;
 }

 /** host to ip address mapping */
 private String extractHostAddr(String hostEntry, String host) {
 String[] mapping = hostEntry.split("\\s+");
 String hostAddr = null;

 if (mapping.length >= 2) {
 // look at the host aliases
 for (int i = 1; i < mapping.length; i++) {
 if (mapping[i].equalsIgnoreCase(host)) {
 hostAddr = mapping[0];
 }
 }
 }
 return hostAddr;
 }

 /**
 * IP Address to host mapping
 * use first host alias in list
 */
 private String extractHost(String hostEntry, String addrString) {
 String[] mapping = hostEntry.split("\\s+");
 String host = null;

 if (mapping.length >= 2) {
 if (mapping[0].equalsIgnoreCase(addrString)) {
 host = mapping[1];
 }
 }
 return host;
 }
 }

 static final InetAddressImpl impl;

 static {
 // create the impl
 impl = InetAddressImplFactory.create();

 // create name service
 nameService = createNameService();
 }

 /**
 * Create an instance of the NameService interface based on
 * the setting of the {@code jdk.net.hosts.file} system property.
 *
 * <p>The default NameService is the PlatformNameService, which typically
 * delegates name and address resolution calls to the underlying
 * OS network libraries.
 *
 * <p> A HostsFileNameService is created if the {@code jdk.net.hosts.file}
 * system property is set. If the specified file doesn't exist, the name or
 * address lookup will result in an UnknownHostException. Thus, non existent
 * hosts file is handled as if the file is empty.
 *
 * @return a NameService
 */
 private static NameService createNameService() {

 String hostsFileName =
 GetPropertyAction.privilegedGetProperty("jdk.net.hosts.file");
 NameService theNameService;
 if (hostsFileName != null) {
 theNameService = new HostsFileNameService(hostsFileName);
 } else {
 theNameService = new PlatformNameService();
 }
 return theNameService;
 }

 /**
 * Creates an InetAddress based on the provided host name and IP address.
 * No name service is checked for the validity of the address.
 *
 * <p> The host name can either be a machine name, such as
 * "{@code java.sun.com}", or a textual representation of its IP
 * address.
 * <p> No validity checking is done on the host name either.
 *
 * <p> If addr specifies an IPv4 address an instance of Inet4Address
 * will be returned; otherwise, an instance of Inet6Address
 * will be returned.
 *
 * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
 * must be 16 bytes long
 *
 * @param host the specified host
 * @param addr the raw IP address in network byte order
 * @return an InetAddress object created from the raw IP address.
 * @exception UnknownHostException if IP address is of illegal length
 * @since 1.4
 */
 public static InetAddress getByAddress(String host, byte[] addr)
 throws UnknownHostException {
 if (host != null && host.length() > 0 && host.charAt(0) == '[') {
 if (host.charAt(host.length()-1) == ']') {
 host = host.substring(1, host.length() -1);
 }
 }
 if (addr != null) {
 if (addr.length == Inet4Address.INADDRSZ) {
 return new Inet4Address(host, addr);
 } else if (addr.length == Inet6Address.INADDRSZ) {
 byte[] newAddr
 = IPAddressUtil.convertFromIPv4MappedAddress(addr);
 if (newAddr != null) {
 return new Inet4Address(host, newAddr);
 } else {
 return new Inet6Address(host, addr);
 }
 }
 }
 throw new UnknownHostException("addr is of illegal length");
 }


 /**
 * Determines the IP address of a host, given the host's name.
 *
 * <p> The host name can either be a machine name, such as
 * "{@code java.sun.com}", or a textual representation of its
 * IP address. If a literal IP address is supplied, only the
 * validity of the address format is checked.
 *
 * <p> For {@code host} specified in literal IPv6 address,
 * either the form defined in RFC 2732 or the literal IPv6 address
 * format defined in RFC 2373 is accepted. IPv6 scoped addresses are also
 * supported. See <a href="Inet6Address.html#scoped">here</a> for a description of IPv6
 * scoped addresses.
 *
 * <p> If the host is {@code null} or {@code host.length()} is equal
 * to zero, then an {@code InetAddress} representing an address of the
 * loopback interface is returned.
 * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC&nbsp;3330</a>
 * section&nbsp;2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC&nbsp;2373</a>
 * section&nbsp;2.5.3.
 *
 * <p> If there is a security manager, and {@code host} is not {@code null}
 * or {@code host.length() } is not equal to zero, the security manager's
 * {@code checkConnect} method is called with the hostname and {@code -1}
 * as its arguments to determine if the operation is allowed.
 *
 * @param host the specified host, or {@code null}.
 * @return an IP address for the given host name.
 * @exception UnknownHostException if no IP address for the
 * {@code host} could be found, or if a scope_id was specified
 * for a global IPv6 address.
 * @exception SecurityException if a security manager exists
 * and its checkConnect method doesn't allow the operation
 */
 public static InetAddress getByName(String host)
 throws UnknownHostException {
 return InetAddress.getAllByName(host)[0];
 }

 // called from deployment cache manager
 private static InetAddress getByName(String host, InetAddress reqAddr)
 throws UnknownHostException {
 return InetAddress.getAllByName(host, reqAddr)[0];
 }

 /**
 * Given the name of a host, returns an array of its IP addresses,
 * based on the configured name service on the system.
 *
 * <p> The host name can either be a machine name, such as
 * "{@code java.sun.com}", or a textual representation of its IP
 * address. If a literal IP address is supplied, only the
 * validity of the address format is checked.
 *
 * <p> For {@code host} specified in <i>literal IPv6 address</i>,
 * either the form defined in RFC 2732 or the literal IPv6 address
 * format defined in RFC 2373 is accepted. A literal IPv6 address may
 * also be qualified by appending a scoped zone identifier or scope_id.
 * The syntax and usage of scope_ids is described
 * <a href="Inet6Address.html#scoped">here</a>.
 *
 * <p> If the host is {@code null} or {@code host.length()} is equal
 * to zero, then an {@code InetAddress} representing an address of the
 * loopback interface is returned.
 * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC&nbsp;3330</a>
 * section&nbsp;2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC&nbsp;2373</a>
 * section&nbsp;2.5.3. </p>
 *
 * <p> If there is a security manager, and {@code host} is not {@code null}
 * or {@code host.length() } is not equal to zero, the security manager's
 * {@code checkConnect} method is called with the hostname and {@code -1}
 * as its arguments to determine if the operation is allowed.
 *
 * @param host the name of the host, or {@code null}.
 * @return an array of all the IP addresses for a given host name.
 *
 * @exception UnknownHostException if no IP address for the
 * {@code host} could be found, or if a scope_id was specified
 * for a global IPv6 address.
 * @exception SecurityException if a security manager exists and its
 * {@code checkConnect} method doesn't allow the operation.
 *
 * @see SecurityManager#checkConnect
 */
 public static InetAddress[] getAllByName(String host)
 throws UnknownHostException {
 return getAllByName(host, null);
 }

 private static InetAddress[] getAllByName(String host, InetAddress reqAddr)
 throws UnknownHostException {

 if (host == null || host.length() == 0) {
 InetAddress[] ret = new InetAddress[1];
 ret[0] = impl.loopbackAddress();
 return ret;
 }

 boolean ipv6Expected = false;
 if (host.charAt(0) == '[') {
 // This is supposed to be an IPv6 literal
 if (host.length() > 2 && host.charAt(host.length()-1) == ']') {
 host = host.substring(1, host.length() -1);
 ipv6Expected = true;
 } else {
 // This was supposed to be a IPv6 address, but it's not!
 throw new UnknownHostException(host + ": invalid IPv6 address");
 }
 }

 // if host is an IP address, we won't do further lookup
 if (Character.digit(host.charAt(0), 16) != -1
 || (host.charAt(0) == ':')) {
 byte[] addr = null;
 int numericZone = -1;
 String ifname = null;
 // see if it is IPv4 address
 addr = IPAddressUtil.textToNumericFormatV4(host);
 if (addr == null) {
 // This is supposed to be an IPv6 literal
 // Check if a numeric or string zone id is present
 int pos;
 if ((pos=host.indexOf ('%')) != -1) {
 numericZone = checkNumericZone (host);
 if (numericZone == -1) { /* remainder of string must be an ifname */
 ifname = host.substring (pos+1);
 }
 }
 if ((addr = IPAddressUtil.textToNumericFormatV6(host)) == null && host.contains(":")) {
 throw new UnknownHostException(host + ": invalid IPv6 address");
 }
 } else if (ipv6Expected) {
 // Means an IPv4 litteral between brackets!
 throw new UnknownHostException("["+host+"]");
 }
 InetAddress[] ret = new InetAddress[1];
 if(addr != null) {
 if (addr.length == Inet4Address.INADDRSZ) {
 ret[0] = new Inet4Address(null, addr);
 } else {
 if (ifname != null) {
 ret[0] = new Inet6Address(null, addr, ifname);
 } else {
 ret[0] = new Inet6Address(null, addr, numericZone);
 }
 }
 return ret;
 }
 } else if (ipv6Expected) {
 // We were expecting an IPv6 Litteral, but got something else
 throw new UnknownHostException("["+host+"]");
 }
 return getAllByName0(host, reqAddr, true, true);
 }

 /**
 * Returns the loopback address.
 * <p>
 * The InetAddress returned will represent the IPv4
 * loopback address, 127.0.0.1, or the IPv6 loopback
 * address, ::1. The IPv4 loopback address returned
 * is only one of many in the form 127.*.*.*
 *
 * @return the InetAddress loopback instance.
 * @since 1.7
 */
 public static InetAddress getLoopbackAddress() {
 return impl.loopbackAddress();
 }


 /**
 * check if the literal address string has %nn appended
 * returns -1 if not, or the numeric value otherwise.
 *
 * %nn may also be a string that represents the displayName of
 * a currently available NetworkInterface.
 */
 private static int checkNumericZone (String s) throws UnknownHostException {
 int percent = s.indexOf ('%');
 int slen = s.length();
 int digit, zone=0;
 if (percent == -1) {
 return -1;
 }
 for (int i=percent+1; i<slen; i++) {
 char c = s.charAt(i);
 if (c == ']') {
 if (i == percent+1) {
 /* empty per-cent field */
 return -1;
 }
 break;
 }
 if ((digit = Character.digit (c, 10)) < 0) {
 return -1;
 }
 zone = (zone * 10) + digit;
 }
 return zone;
 }

 private static InetAddress[] getAllByName0 (String host)
 throws UnknownHostException
 {
 return getAllByName0(host, true);
 }

 /**
 * package private so SocketPermission can call it
 */
 static InetAddress[] getAllByName0 (String host, boolean check)
 throws UnknownHostException {
 return getAllByName0 (host, null, check, true);
 }

 /**
 * Designated lookup method.
 *
 * @param host host name to look up
 * @param reqAddr requested address to be the 1st in returned array
 * @param check perform security check
 * @param useCache use cached value if not expired else always
 * perform name service lookup (and cache the result)
 * @return array of InetAddress(es)
 * @throws UnknownHostException if host name is not found
 */
 private static InetAddress[] getAllByName0(String host,
 InetAddress reqAddr,
 boolean check,
 boolean useCache)
 throws UnknownHostException {

 /* If it gets here it is presumed to be a hostname */

 /* make sure the connection to the host is allowed, before we
 * give out a hostname
 */
 if (check) {
 SecurityManager security = System.getSecurityManager();
 if (security != null) {
 security.checkConnect(host, -1);
 }
 }

 // remove expired addresses from cache - expirySet keeps them ordered
 // by expiry time so we only need to iterate the prefix of the NavigableSet...
 long now = System.nanoTime();
 for (CachedAddresses caddrs : expirySet) {
 // compare difference of time instants rather than
 // time instants directly, to avoid possible overflow.
 // (see System.nanoTime() recommendations...)
 if ((caddrs.expiryTime - now) < 0L) {
 // ConcurrentSkipListSet uses weakly consistent iterator,
 // so removing while iterating is OK...
 if (expirySet.remove(caddrs)) {
 // ... remove from cache
 cache.remove(caddrs.host, caddrs);
 }
 } else {
 // we encountered 1st element that expires in future
 break;
 }
 }

 // look-up or remove from cache
 Addresses addrs;
 if (useCache) {
 addrs = cache.get(host);
 } else {
 addrs = cache.remove(host);
 if (addrs != null) {
 if (addrs instanceof CachedAddresses) {
 // try removing from expirySet too if CachedAddresses
 expirySet.remove(addrs);
 }
 addrs = null;
 }
 }

 if (addrs == null) {
 // create a NameServiceAddresses instance which will look up
 // the name service and install it within cache...
 Addresses oldAddrs = cache.putIfAbsent(
 host,
 addrs = new NameServiceAddresses(host, reqAddr)
 );
 if (oldAddrs != null) { // lost putIfAbsent race
 addrs = oldAddrs;
 }
 }

 // ask Addresses to get an array of InetAddress(es) and clone it
 return addrs.get().clone();
 }

 static InetAddress[] getAddressesFromNameService(String host, InetAddress reqAddr)
 throws UnknownHostException
 {
 InetAddress[] addresses = null;
 UnknownHostException ex = null;

 try {
 addresses = nameService.lookupAllHostAddr(host);
 } catch (UnknownHostException uhe) {
 if (host.equalsIgnoreCase("localhost")) {
 addresses = new InetAddress[] { impl.loopbackAddress() };
 }
 else {
 ex = uhe;
 }
 }

 if (addresses == null) {
 throw ex == null ? new UnknownHostException(host) : ex;
 }

 // More to do?
 if (reqAddr != null && addresses.length > 1 && !addresses[0].equals(reqAddr)) {
 // Find it?
 int i = 1;
 for (; i < addresses.length; i++) {
 if (addresses[i].equals(reqAddr)) {
 break;
 }
 }
 // Rotate
 if (i < addresses.length) {
 InetAddress tmp, tmp2 = reqAddr;
 for (int j = 0; j < i; j++) {
 tmp = addresses[j];
 addresses[j] = tmp2;
 tmp2 = tmp;
 }
 addresses[i] = tmp2;
 }
 }

 return addresses;
 }

 /**
 * Returns an {@code InetAddress} object given the raw IP address .
 * The argument is in network byte order: the highest order
 * byte of the address is in {@code getAddress()[0]}.
 *
 * <p> This method doesn't block, i.e. no reverse name service lookup
 * is performed.
 *
 * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
 * must be 16 bytes long
 *
 * @param addr the raw IP address in network byte order
 * @return an InetAddress object created from the raw IP address.
 * @exception UnknownHostException if IP address is of illegal length
 * @since 1.4
 */
 public static InetAddress getByAddress(byte[] addr)
 throws UnknownHostException {
 return getByAddress(null, addr);
 }

 private static final class CachedLocalHost {
 final String host;
 final InetAddress addr;
 final long expiryTime = System.nanoTime() + 5000_000_000L; // now + 5s;

 CachedLocalHost(String host, InetAddress addr) {
 this.host = host;
 this.addr = addr;
 }
 }

 private static volatile CachedLocalHost cachedLocalHost;

 /**
 * Returns the address of the local host. This is achieved by retrieving
 * the name of the host from the system, then resolving that name into
 * an {@code InetAddress}.
 *
 * <P>Note: The resolved address may be cached for a short period of time.
 * </P>
 *
 * <p>If there is a security manager, its
 * {@code checkConnect} method is called
 * with the local host name and {@code -1}
 * as its arguments to see if the operation is allowed.
 * If the operation is not allowed, an InetAddress representing
 * the loopback address is returned.
 *
 * @return the address of the local host.
 *
 * @exception UnknownHostException if the local host name could not
 * be resolved into an address.
 *
 * @see SecurityManager#checkConnect
 * @see java.net.InetAddress#getByName(java.lang.String)
 */
 public static InetAddress getLocalHost() throws UnknownHostException {

 SecurityManager security = System.getSecurityManager();
 try {
 // is cached data still valid?
 CachedLocalHost clh = cachedLocalHost;
 if (clh != null && (clh.expiryTime - System.nanoTime()) >= 0L) {
 if (security != null) {
 security.checkConnect(clh.host, -1);
 }
 return clh.addr;
 }

 String local = impl.getLocalHostName();

 if (security != null) {
 security.checkConnect(local, -1);
 }

 InetAddress localAddr;
 if (local.equals("localhost")) {
 // shortcut for "localhost" host name
 localAddr = impl.loopbackAddress();
 } else {
 // call getAllByName0 without security checks and
 // without using cached data
 try {
 localAddr = getAllByName0(local, null, false, false)[0];
 } catch (UnknownHostException uhe) {
 // Rethrow with a more informative error message.
 UnknownHostException uhe2 =
 new UnknownHostException(local + ": " +
 uhe.getMessage());
 uhe2.initCause(uhe);
 throw uhe2;
 }
 }
 cachedLocalHost = new CachedLocalHost(local, localAddr);
 return localAddr;
 } catch (java.lang.SecurityException e) {
 return impl.loopbackAddress();
 }
 }

 /**
 * Perform class load-time initializations.
 */
 private static native void init();


 /*
 * Returns the InetAddress representing anyLocalAddress
 * (typically 0.0.0.0 or ::0)
 */
 static InetAddress anyLocalAddress() {
 return impl.anyLocalAddress();
 }

 /*
 * Load and instantiate an underlying impl class
 */
 static InetAddressImpl loadImpl(String implName) {
 Object impl = null;

 /*
 * Property "impl.prefix" will be prepended to the classname
 * of the implementation object we instantiate, to which we
 * delegate the real work (like native methods). This
 * property can vary across implementations of the java.
 * classes. The default is an empty String "".
 */
 String prefix = GetPropertyAction.privilegedGetProperty("impl.prefix", "");
 try {
 @SuppressWarnings("deprecation")
 Object tmp = Class.forName("java.net." + prefix + implName).newInstance();
 impl = tmp;
 } catch (ClassNotFoundException e) {
 System.err.println("Class not found: java.net." + prefix +
 implName + ":\ncheck impl.prefix property " +
 "in your properties file.");
 } catch (InstantiationException e) {
 System.err.println("Could not instantiate: java.net." + prefix +
 implName + ":\ncheck impl.prefix property " +
 "in your properties file.");
 } catch (IllegalAccessException e) {
 System.err.println("Cannot access class: java.net." + prefix +
 implName + ":\ncheck impl.prefix property " +
 "in your properties file.");
 }

 if (impl == null) {
 try {
 @SuppressWarnings("deprecation")
 Object tmp = Class.forName(implName).newInstance();
 impl = tmp;
 } catch (Exception e) {
 throw new Error("System property impl.prefix incorrect");
 }
 }

 return (InetAddressImpl) impl;
 }

 private void readObjectNoData () throws
 IOException, ClassNotFoundException {
 if (getClass().getClassLoader() != null) {
 throw new SecurityException ("invalid address type");
 }
 }

 private static final jdk.internal.misc.Unsafe UNSAFE
 = jdk.internal.misc.Unsafe.getUnsafe();
 private static final long FIELDS_OFFSET
 = UNSAFE.objectFieldOffset(InetAddress.class, "holder");

 private void readObject (ObjectInputStream s) throws
 IOException, ClassNotFoundException {
 if (getClass().getClassLoader() != null) {
 throw new SecurityException ("invalid address type");
 }
 GetField gf = s.readFields();
 String host = (String)gf.get("hostName", null);
 int address = gf.get("address", 0);
 int family = gf.get("family", 0);
 if (family != IPv4 && family != IPv6) {
 throw new InvalidObjectException("invalid address family type: " + family);
 }
 InetAddressHolder h = new InetAddressHolder(host, address, family);
 UNSAFE.putObject(this, FIELDS_OFFSET, h);
 }

 /* needed because the serializable fields no longer exist */

 /**
 * @serialField hostName String
 * @serialField address int
 * @serialField family int
 */
 private static final ObjectStreamField[] serialPersistentFields = {
 new ObjectStreamField("hostName", String.class),
 new ObjectStreamField("address", int.class),
 new ObjectStreamField("family", int.class),
 };

 private void writeObject (ObjectOutputStream s) throws
 IOException {
 if (getClass().getClassLoader() != null) {
 throw new SecurityException ("invalid address type");
 }
 PutField pf = s.putFields();
 pf.put("hostName", holder().getHostName());
 pf.put("address", holder().getAddress());
 pf.put("family", holder().getFamily());
 s.writeFields();
 }
}

/*
 * Simple factory to create the impl
 */
class InetAddressImplFactory {

 static InetAddressImpl create() {
 return InetAddress.loadImpl(isIPv6Supported() ?
 "Inet6AddressImpl" : "Inet4AddressImpl");
 }

 static native boolean isIPv6Supported();
}