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 * 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,

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 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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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.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&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>

 *

 * <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 {

        InetAddressHolder() {}

        InetAddressHolder(String hostName, int address, int family) {

            this.hostName = hostName;

            this.address = address;

            this.family = family;

        }

        String hostName;

        String getHostName() {

            return hostName;

        }

        /**

         * 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 */

    private 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.