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	/*
	* Copyright (c) 1995, 2018, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.net;

	import java.util.HashMap;
	import java.util.LinkedHashMap;
	import java.util.Random;
	import java.util.Iterator;
	import java.util.LinkedList;
	import java.util.List;
	import java.util.ArrayList;
	import java.util.ServiceLoader;
	import java.security.AccessController;
	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 sun.security.action.*;
	import sun.net.InetAddressCachePolicy;
	import sun.net.util.IPAddressUtil;
	import sun.net.spi.nameservice.*;

	/**
	* 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 790:
	* Assigned Numbers</i></a>, <a
	* href="http://www.ietf.org/rfc/rfc1918.txt"> <i>RFC 1918:
	* Address Allocation for Private Internets</i></a>, <a
	* href="http://www.ietf.org/rfc/rfc2365.txt"><i>RFC 2365:
	* Administratively Scoped IP Multicast</i></a>, and <a
	* href="http://www.ietf.org/rfc/rfc2373.txt"><i>RFC 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>
	*
	* <blockquote><table cellspacing=2 summary="Description of unicast and multicast address types">
	* <tr><th valign=top><i>unicast</i></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 valign=top><i>multicast</i></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>
	* </table></blockquote>
	*
	* <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:
	*
	* <blockquote>
	* <dl>
	* <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 as 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 as 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>
	* </blockquote>
	*
	* @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 JDK1.0
	*/
	public
	class InetAddress implements java.io.Serializable {
	/**
	* Specify the address family: Internet Protocol, Version 4
	* @since 1.4
	*/
	static final int IPv4 = 1;

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

	/* Specify address family preference */
	static transient boolean preferIPv6Address = false;

	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
	* sun.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 List<NameService> nameServices = null;

	/* Used to store the best available hostname */
	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 {
	preferIPv6Address = java.security.AccessController.doPrivileged(
	new GetBooleanAction("java.net.preferIPv6Addresses")).booleanValue();
	AccessController.doPrivileged(
	new java.security.PrivilegedAction<Void>() {
	public Void run() {
	System.loadLibrary("net");
	return null;
	}
	});
	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 JDK1.1
	*/
	public boolean isMulticastAddress() {
	return false;
	}

	/**
	* Utility routine to check if the InetAddress in 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() {
	if (canonicalHostName == null) {
	canonicalHostName =
	InetAddress.getHostFromNameService(this, true);
	}
	return canonicalHostName;
	}

	/**
	* 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;
	for (NameService nameService : nameServices) {
	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;
	}

	break;

	} catch (SecurityException e) {
	host = addr.getHostAddress();
	break;
	} 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 JDK1.0.2
	*/
	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 ((hostName != null) ? hostName : "")
	+ "/" + getHostAddress();
	}

	/*
	* Cached addresses - our own litle nis, not!
	*/
	private static Cache addressCache = new Cache(Cache.Type.Positive);

	private static Cache negativeCache = new Cache(Cache.Type.Negative);

	private static boolean addressCacheInit = false;

	static InetAddress[] unknown_array; // put THIS in cache

	static InetAddressImpl impl;

	private static final HashMap<String, Void> lookupTable = new HashMap<>();

	/**
	* Represents a cache entry
	*/
	static final class CacheEntry {

	CacheEntry(InetAddress[] addresses, long expiration) {
	this.addresses = addresses;
	this.expiration = expiration;
	}

	InetAddress[] addresses;
	long expiration;
	}

	/**
	* A cache that manages entries based on a policy specified
	* at creation time.
	*/
	static final class Cache {
	private LinkedHashMap<String, CacheEntry> cache;
	private Type type;

	enum Type {Positive, Negative};

	/**
	* Create cache
	*/
	public Cache(Type type) {
	this.type = type;
	cache = new LinkedHashMap<String, CacheEntry>();
	}

	private int getPolicy() {
	if (type == Type.Positive) {
	return InetAddressCachePolicy.get();
	} else {
	return InetAddressCachePolicy.getNegative();
	}
	}

	/**
	* Add an entry to the cache. If there's already an
	* entry then for this host then the entry will be
	* replaced.
	*/
	public Cache put(String host, InetAddress[] addresses) {
	int policy = getPolicy();
	if (policy == InetAddressCachePolicy.NEVER) {
	return this;
	}

	// purge any expired entries

	if (policy != InetAddressCachePolicy.FOREVER) {

	// As we iterate in insertion order we can
	// terminate when a non-expired entry is found.
	LinkedList<String> expired = new LinkedList<>();
	long now = System.currentTimeMillis();
	for (String key : cache.keySet()) {
	CacheEntry entry = cache.get(key);

	if (entry.expiration >= 0 && entry.expiration < now) {
	expired.add(key);
	} else {
	break;
	}
	}

	for (String key : expired) {
	cache.remove(key);
	}
	}

	// create new entry and add it to the cache
	// -- as a HashMap replaces existing entries we
	// don't need to explicitly check if there is
	// already an entry for this host.
	long expiration;
	if (policy == InetAddressCachePolicy.FOREVER) {
	expiration = -1;
	} else {
	expiration = System.currentTimeMillis() + (policy * 1000);
	}
	CacheEntry entry = new CacheEntry(addresses, expiration);
	cache.put(host, entry);
	return this;
	}

	/**
	* Query the cache for the specific host. If found then
	* return its CacheEntry, or null if not found.
	*/
	public CacheEntry get(String host) {
	int policy = getPolicy();
	if (policy == InetAddressCachePolicy.NEVER) {
	return null;
	}
	CacheEntry entry = cache.get(host);

	// check if entry has expired
	if (entry != null && policy != InetAddressCachePolicy.FOREVER) {
	if (entry.expiration >= 0 &&
	entry.expiration < System.currentTimeMillis()) {
	cache.remove(host);
	entry = null;
	}
	}

	return entry;
	}
	}

	/*
	* Initialize cache and insert anyLocalAddress into the
	* unknown array with no expiry.
	*/
	private static void cacheInitIfNeeded() {
	assert Thread.holdsLock(addressCache);
	if (addressCacheInit) {
	return;
	}
	unknown_array = new InetAddress[1];
	unknown_array[0] = impl.anyLocalAddress();

	addressCache.put(impl.anyLocalAddress().getHostName(),
	unknown_array);

	addressCacheInit = true;
	}

	/*
	* Cache the given hostname and addresses.
	*/
	private static void cacheAddresses(String hostname,
	InetAddress[] addresses,
	boolean success) {
	hostname = hostname.toLowerCase();
	synchronized (addressCache) {
	cacheInitIfNeeded();
	if (success) {
	addressCache.put(hostname, addresses);
	} else {
	negativeCache.put(hostname, addresses);
	}
	}
	}

	/*
	* Lookup hostname in cache (positive & negative cache). If
	* found return addresses, null if not found.
	*/
	private static InetAddress[] getCachedAddresses(String hostname) {
	hostname = hostname.toLowerCase();

	// search both positive & negative caches

	synchronized (addressCache) {
	cacheInitIfNeeded();

	CacheEntry entry = addressCache.get(hostname);
	if (entry == null) {
	entry = negativeCache.get(hostname);
	}

	if (entry != null) {
	return entry.addresses;
	}
	}

	// not found
	return null;
	}

	private static NameService createNSProvider(String provider) {
	if (provider == null)
	return null;

	NameService nameService = null;
	if (provider.equals("default")) {
	// initialize the default name service
	nameService = new NameService() {
	public InetAddress[] lookupAllHostAddr(String host)
	throws UnknownHostException {
	return impl.lookupAllHostAddr(host);
	}
	public String getHostByAddr(byte[] addr)
	throws UnknownHostException {
	return impl.getHostByAddr(addr);
	}
	};
	} else {
	final String providerName = provider;
	try {
	nameService = java.security.AccessController.doPrivileged(
	new java.security.PrivilegedExceptionAction<NameService>() {
	public NameService run() {
	Iterator<NameServiceDescriptor> itr =
	ServiceLoader.load(NameServiceDescriptor.class)
	.iterator();
	while (itr.hasNext()) {
	NameServiceDescriptor nsd = itr.next();
	if (providerName.
	equalsIgnoreCase(nsd.getType()+","
	+nsd.getProviderName())) {
	try {
	return nsd.createNameService();
	} catch (Exception e) {
	e.printStackTrace();
	System.err.println(
	"Cannot create name service:"
	+providerName+": " + e);
	}
	}
	}

	return null;
	}
	}
	);
	} catch (java.security.PrivilegedActionException e) {
	}
	}

	return nameService;
	}

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

	// get name service if provided and requested
	String provider = null;;
	String propPrefix = "sun.net.spi.nameservice.provider.";
	int n = 1;
	nameServices = new ArrayList<NameService>();
	provider = AccessController.doPrivileged(
	new GetPropertyAction(propPrefix + n));
	while (provider != null) {
	NameService ns = createNSProvider(provider);
	if (ns != null)
	nameServices.add(ns);

	n++;
	provider = AccessController.doPrivileged(
	new GetPropertyAction(propPrefix + n));
	}

	// if not designate any name services provider,
	// create a default one
	if (nameServices.size() == 0) {
	NameService ns = createNSProvider("default");
	nameServices.add(ns);
	}
	}

	/**
	* 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} then an {@code InetAddress}
	* representing an address of the loopback interface is returned.
	* See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC 3330</a>
	* section 2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC 2373</a>
	* section 2.5.3. </p>
	*
	* @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} then an {@code InetAddress}
	* representing an address of the loopback interface is returned.
	* See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC 3330</a>
	* section 2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC 2373</a>
	* section 2.5.3. </p>
	*
	* <p> If there is a security manager and {@code host} is not
	* null and {@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 see 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);
	}

	/**
	* 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);
	}

	private static InetAddress[] getAllByName0 (String host, InetAddress reqAddr, boolean check)
	throws UnknownHostException {

	/* If it gets here it is presumed to be a hostname */
	/* Cache.get can return: null, unknownAddress, or InetAddress[] */

	/* 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);
	}
	}

	InetAddress[] addresses = getCachedAddresses(host);

	/* If no entry in cache, then do the host lookup */
	if (addresses == null) {
	addresses = getAddressesFromNameService(host, reqAddr);
	}

	if (addresses == unknown_array)
	throw new UnknownHostException(host);

	return addresses.clone();
	}

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

	// Check whether the host is in the lookupTable.
	// 1) If the host isn't in the lookupTable when
	// checkLookupTable() is called, checkLookupTable()
	// would add the host in the lookupTable and
	// return null. So we will do the lookup.
	// 2) If the host is in the lookupTable when
	// checkLookupTable() is called, the current thread
	// would be blocked until the host is removed
	// from the lookupTable. Then this thread
	// should try to look up the addressCache.
	// i) if it found the addresses in the
	// addressCache, checkLookupTable() would
	// return the addresses.
	// ii) if it didn't find the addresses in the
	// addressCache for any reason,
	// it should add the host in the
	// lookupTable and return null so the
	// following code would do a lookup itself.
	if ((addresses = checkLookupTable(host)) == null) {
	try {
	// This is the first thread which looks up the addresses
	// this host or the cache entry for this host has been
	// expired so this thread should do the lookup.
	for (NameService nameService : nameServices) {
	try {
	/*
	* Do not put the call to lookup() inside the
	* constructor. if you do you will still be
	* allocating space when the lookup fails.
	*/

	addresses = nameService.lookupAllHostAddr(host);
	success = true;
	break;
	} catch (UnknownHostException uhe) {
	if (host.equalsIgnoreCase("localhost")) {
	InetAddress[] local = new InetAddress[] { impl.loopbackAddress() };
	addresses = local;
	success = true;
	break;
	}
	else {
	addresses = unknown_array;
	success = false;
	ex = uhe;
	}
	}
	}

	// 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;
	}
	}
	// Cache the address.
	cacheAddresses(host, addresses, success);

	if (!success && ex != null)
	throw ex;

	} finally {
	// Delete host from the lookupTable and notify
	// all threads waiting on the lookupTable monitor.
	updateLookupTable(host);
	}
	}

	return addresses;
	}


	private static InetAddress[] checkLookupTable(String host) {
	synchronized (lookupTable) {
	// If the host isn't in the lookupTable, add it in the
	// lookuptable and return null. The caller should do
	// the lookup.
	if (lookupTable.containsKey(host) == false) {
	lookupTable.put(host, null);
	return null;
	}

	// If the host is in the lookupTable, it means that another
	// thread is trying to look up the addresses of this host.
	// This thread should wait.
	while (lookupTable.containsKey(host)) {
	try {
	lookupTable.wait();
	} catch (InterruptedException e) {
	}
	}
	}

	// The other thread has finished looking up the addresses of
	// the host. This thread should retry to get the addresses
	// from the addressCache. If it doesn't get the addresses from
	// the cache, it will try to look up the addresses itself.
	InetAddress[] addresses = getCachedAddresses(host);
	if (addresses == null) {
	synchronized (lookupTable) {
	lookupTable.put(host, null);
	return null;
	}
	}

	return addresses;
	}

	private static void updateLookupTable(String host) {
	synchronized (lookupTable) {
	lookupTable.remove(host);
	lookupTable.notifyAll();
	}
	}

	/**
	* 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 InetAddress cachedLocalHost = null;
	private static long cacheTime = 0;
	private static final long maxCacheTime = 5000L;
	private static final Object cacheLock = new Object();

	/**
	* 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 {
	String local = impl.getLocalHostName();

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

	if (local.equals("localhost")) {
	return impl.loopbackAddress();
	}

	InetAddress ret = null;
	synchronized (cacheLock) {
	long now = System.currentTimeMillis();
	if (cachedLocalHost != null) {
	if ((now - cacheTime) < maxCacheTime) // Less than 5s old?
	ret = cachedLocalHost;
	else
	cachedLocalHost = null;
	}

	// we are calling getAddressesFromNameService directly
	// to avoid getting localHost from cache
	if (ret == null) {
	InetAddress[] localAddrs;
	try {
	localAddrs =
	InetAddress.getAddressesFromNameService(local, null);
	} catch (UnknownHostException uhe) {
	// Rethrow with a more informative error message.
	UnknownHostException uhe2 =
	new UnknownHostException(local + ": " +
	uhe.getMessage());
	uhe2.initCause(uhe);
	throw uhe2;
	}
	cachedLocalHost = localAddrs[0];
	cacheTime = now;
	ret = localAddrs[0];
	}
	}
	return ret;
	} 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 = AccessController.doPrivileged(
	new GetPropertyAction("impl.prefix", ""));
	try {
	impl = Class.forName("java.net." + prefix + implName).newInstance();
	} 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 {
	impl = Class.forName(implName).newInstance();
	} catch (Exception e) {
	throw new Error("System property impl.prefix incorrect");
	}
	}

	return (InetAddressImpl) impl;
	}

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

	private static final long FIELDS_OFFSET;
	private static final sun.misc.Unsafe UNSAFE;

	static {
	try {
	sun.misc.Unsafe unsafe = sun.misc.Unsafe.getUnsafe();
	FIELDS_OFFSET = unsafe.objectFieldOffset(
	InetAddress.class.getDeclaredField("holder")
	);
	UNSAFE = unsafe;
	} catch (ReflectiveOperationException e) {
	throw new Error(e);
	}
	}

	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();
	}

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