1 /*
   2  * Copyright (c) 1995, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.net;
  27 
  28 import java.util.NavigableSet;
  29 import java.util.ArrayList;
  30 import java.util.Objects;
  31 import java.util.Scanner;
  32 import java.security.AccessController;
  33 import java.io.File;
  34 import java.io.FileNotFoundException;
  35 import java.io.ObjectStreamException;
  36 import java.io.ObjectStreamField;
  37 import java.io.IOException;
  38 import java.io.InvalidObjectException;
  39 import java.io.ObjectInputStream;
  40 import java.io.ObjectInputStream.GetField;
  41 import java.io.ObjectOutputStream;
  42 import java.io.ObjectOutputStream.PutField;
  43 import java.lang.annotation.Native;
  44 import java.util.concurrent.ConcurrentHashMap;
  45 import java.util.concurrent.ConcurrentMap;
  46 import java.util.concurrent.ConcurrentSkipListSet;
  47 import java.util.concurrent.atomic.AtomicLong;
  48 import java.util.Arrays;
  49 
  50 import jdk.internal.access.JavaNetInetAddressAccess;
  51 import jdk.internal.access.SharedSecrets;
  52 import sun.security.action.*;
  53 import sun.net.InetAddressCachePolicy;
  54 import sun.net.util.IPAddressUtil;
  55 
  56 /**
  57  * This class represents an Internet Protocol (IP) address.
  58  *
  59  * <p> An IP address is either a 32-bit or 128-bit unsigned number
  60  * used by IP, a lower-level protocol on which protocols like UDP and
  61  * TCP are built. The IP address architecture is defined by <a
  62  * href="http://www.ietf.org/rfc/rfc790.txt"><i>RFC&nbsp;790:
  63  * Assigned Numbers</i></a>, <a
  64  * href="http://www.ietf.org/rfc/rfc1918.txt"> <i>RFC&nbsp;1918:
  65  * Address Allocation for Private Internets</i></a>, <a
  66  * href="http://www.ietf.org/rfc/rfc2365.txt"><i>RFC&nbsp;2365:
  67  * Administratively Scoped IP Multicast</i></a>, and <a
  68  * href="http://www.ietf.org/rfc/rfc2373.txt"><i>RFC&nbsp;2373: IP
  69  * Version 6 Addressing Architecture</i></a>. An instance of an
  70  * InetAddress consists of an IP address and possibly its
  71  * corresponding host name (depending on whether it is constructed
  72  * with a host name or whether it has already done reverse host name
  73  * resolution).
  74  *
  75  * <h2> Address types </h2>
  76  *
  77  * <table class="striped" style="margin-left:2em">
  78  *   <caption style="display:none">Description of unicast and multicast address types</caption>
  79  *   <thead>
  80  *   <tr><th scope="col">Address Type</th><th scope="col">Description</th></tr>
  81  *   </thead>
  82  *   <tbody>
  83  *   <tr><th scope="row" style="vertical-align:top">unicast</th>
  84  *       <td>An identifier for a single interface. A packet sent to
  85  *         a unicast address is delivered to the interface identified by
  86  *         that address.
  87  *
  88  *         <p> The Unspecified Address -- Also called anylocal or wildcard
  89  *         address. It must never be assigned to any node. It indicates the
  90  *         absence of an address. One example of its use is as the target of
  91  *         bind, which allows a server to accept a client connection on any
  92  *         interface, in case the server host has multiple interfaces.
  93  *
  94  *         <p> The <i>unspecified</i> address must not be used as
  95  *         the destination address of an IP packet.
  96  *
  97  *         <p> The <i>Loopback</i> Addresses -- This is the address
  98  *         assigned to the loopback interface. Anything sent to this
  99  *         IP address loops around and becomes IP input on the local
 100  *         host. This address is often used when testing a
 101  *         client.</td></tr>
 102  *   <tr><th scope="row" style="vertical-align:top">multicast</th>
 103  *       <td>An identifier for a set of interfaces (typically belonging
 104  *         to different nodes). A packet sent to a multicast address is
 105  *         delivered to all interfaces identified by that address.</td></tr>
 106  * </tbody>
 107  * </table>
 108  *
 109  * <h3> IP address scope </h3>
 110  *
 111  * <p> <i>Link-local</i> addresses are designed to be used for addressing
 112  * on a single link for purposes such as auto-address configuration,
 113  * neighbor discovery, or when no routers are present.
 114  *
 115  * <p> <i>Site-local</i> addresses are designed to be used for addressing
 116  * inside of a site without the need for a global prefix.
 117  *
 118  * <p> <i>Global</i> addresses are unique across the internet.
 119  *
 120  * <h3> Textual representation of IP addresses </h3>
 121  *
 122  * The textual representation of an IP address is address family specific.
 123  *
 124  * <p>
 125  *
 126  * For IPv4 address format, please refer to <A
 127  * HREF="Inet4Address.html#format">Inet4Address#format</A>; For IPv6
 128  * address format, please refer to <A
 129  * HREF="Inet6Address.html#format">Inet6Address#format</A>.
 130  *
 131  * <P>There is a <a href="doc-files/net-properties.html#Ipv4IPv6">couple of
 132  * System Properties</a> affecting how IPv4 and IPv6 addresses are used.</P>
 133  *
 134  * <h3> Host Name Resolution </h3>
 135  *
 136  * Host name-to-IP address <i>resolution</i> is accomplished through
 137  * the use of a combination of local machine configuration information
 138  * and network naming services such as the Domain Name System (DNS)
 139  * and Network Information Service(NIS). The particular naming
 140  * services(s) being used is by default the local machine configured
 141  * one. For any host name, its corresponding IP address is returned.
 142  *
 143  * <p> <i>Reverse name resolution</i> means that for any IP address,
 144  * the host associated with the IP address is returned.
 145  *
 146  * <p> The InetAddress class provides methods to resolve host names to
 147  * their IP addresses and vice versa.
 148  *
 149  * <h3> InetAddress Caching </h3>
 150  *
 151  * The InetAddress class has a cache to store successful as well as
 152  * unsuccessful host name resolutions.
 153  *
 154  * <p> By default, when a security manager is installed, in order to
 155  * protect against DNS spoofing attacks,
 156  * the result of positive host name resolutions are
 157  * cached forever. When a security manager is not installed, the default
 158  * behavior is to cache entries for a finite (implementation dependent)
 159  * period of time. The result of unsuccessful host
 160  * name resolution is cached for a very short period of time (10
 161  * seconds) to improve performance.
 162  *
 163  * <p> If the default behavior is not desired, then a Java security property
 164  * can be set to a different Time-to-live (TTL) value for positive
 165  * caching. Likewise, a system admin can configure a different
 166  * negative caching TTL value when needed.
 167  *
 168  * <p> Two Java security properties control the TTL values used for
 169  *  positive and negative host name resolution caching:
 170  *
 171  * <dl style="margin-left:2em">
 172  * <dt><b>networkaddress.cache.ttl</b></dt>
 173  * <dd>Indicates the caching policy for successful name lookups from
 174  * the name service. The value is specified as an integer to indicate
 175  * the number of seconds to cache the successful lookup. The default
 176  * setting is to cache for an implementation specific period of time.
 177  * <p>
 178  * A value of -1 indicates "cache forever".
 179  * </dd>
 180  * <dt><b>networkaddress.cache.negative.ttl</b> (default: 10)</dt>
 181  * <dd>Indicates the caching policy for un-successful name lookups
 182  * from the name service. The value is specified as an integer to
 183  * indicate the number of seconds to cache the failure for
 184  * un-successful lookups.
 185  * <p>
 186  * A value of 0 indicates "never cache".
 187  * A value of -1 indicates "cache forever".
 188  * </dd>
 189  * </dl>
 190  *
 191  * @author  Chris Warth
 192  * @see     java.net.InetAddress#getByAddress(byte[])
 193  * @see     java.net.InetAddress#getByAddress(java.lang.String, byte[])
 194  * @see     java.net.InetAddress#getAllByName(java.lang.String)
 195  * @see     java.net.InetAddress#getByName(java.lang.String)
 196  * @see     java.net.InetAddress#getLocalHost()
 197  * @since 1.0
 198  */
 199 public
 200 class InetAddress implements java.io.Serializable {
 201 
 202     @Native static final int PREFER_IPV4_VALUE = 0;
 203     @Native static final int PREFER_IPV6_VALUE = 1;
 204     @Native static final int PREFER_SYSTEM_VALUE = 2;
 205 
 206     /**
 207      * Specify the address family: Internet Protocol, Version 4
 208      * @since 1.4
 209      */
 210     @Native static final int IPv4 = 1;
 211 
 212     /**
 213      * Specify the address family: Internet Protocol, Version 6
 214      * @since 1.4
 215      */
 216     @Native static final int IPv6 = 2;
 217 
 218     /* Specify address family preference */
 219     static transient final int preferIPv6Address;
 220 
 221     static class InetAddressHolder {
 222         /**
 223          * Reserve the original application specified hostname.
 224          *
 225          * The original hostname is useful for domain-based endpoint
 226          * identification (see RFC 2818 and RFC 6125).  If an address
 227          * was created with a raw IP address, a reverse name lookup
 228          * may introduce endpoint identification security issue via
 229          * DNS forging.
 230          *
 231          * Oracle JSSE provider is using this original hostname, via
 232          * jdk.internal.misc.JavaNetAccess, for SSL/TLS endpoint identification.
 233          *
 234          * Note: May define a new public method in the future if necessary.
 235          */
 236         String originalHostName;
 237 
 238         InetAddressHolder() {}
 239 
 240         InetAddressHolder(String hostName, int address, int family) {
 241             this.originalHostName = hostName;
 242             this.hostName = hostName;
 243             this.address = address;
 244             this.family = family;
 245         }
 246 
 247         void init(String hostName, int family) {
 248             this.originalHostName = hostName;
 249             this.hostName = hostName;
 250             if (family != -1) {
 251                 this.family = family;
 252             }
 253         }
 254 
 255         String hostName;
 256 
 257         String getHostName() {
 258             return hostName;
 259         }
 260 
 261         String getOriginalHostName() {
 262             return originalHostName;
 263         }
 264 
 265         /**
 266          * Holds a 32-bit IPv4 address.
 267          */
 268         int address;
 269 
 270         int getAddress() {
 271             return address;
 272         }
 273 
 274         /**
 275          * Specifies the address family type, for instance, '1' for IPv4
 276          * addresses, and '2' for IPv6 addresses.
 277          */
 278         int family;
 279 
 280         int getFamily() {
 281             return family;
 282         }
 283     }
 284 
 285     /* Used to store the serializable fields of InetAddress */
 286     final transient InetAddressHolder holder;
 287 
 288     InetAddressHolder holder() {
 289         return holder;
 290     }
 291 
 292     /* Used to store the name service provider */
 293     private static transient NameService nameService;
 294 
 295     /**
 296      * Used to store the best available hostname.
 297      * Lazily initialized via a data race; safe because Strings are immutable.
 298      */
 299     private transient String canonicalHostName = null;
 300 
 301     /** use serialVersionUID from JDK 1.0.2 for interoperability */
 302     @java.io.Serial
 303     private static final long serialVersionUID = 3286316764910316507L;
 304 
 305     /*
 306      * Load net library into runtime, and perform initializations.
 307      */
 308     static {
 309         String str = GetPropertyAction.privilegedGetProperty("java.net.preferIPv6Addresses");
 310         if (str == null) {
 311             preferIPv6Address = PREFER_IPV4_VALUE;
 312         } else if (str.equalsIgnoreCase("true")) {
 313             preferIPv6Address = PREFER_IPV6_VALUE;
 314         } else if (str.equalsIgnoreCase("false")) {
 315             preferIPv6Address = PREFER_IPV4_VALUE;
 316         } else if (str.equalsIgnoreCase("system")) {
 317             preferIPv6Address = PREFER_SYSTEM_VALUE;
 318         } else {
 319             preferIPv6Address = PREFER_IPV4_VALUE;
 320         }
 321         jdk.internal.loader.BootLoader.loadLibrary("net");
 322         SharedSecrets.setJavaNetInetAddressAccess(
 323                 new JavaNetInetAddressAccess() {
 324                     public String getOriginalHostName(InetAddress ia) {
 325                         return ia.holder.getOriginalHostName();
 326                     }
 327 
 328                     public InetAddress getByName(String hostName,
 329                                                  InetAddress hostAddress)
 330                             throws UnknownHostException
 331                     {
 332                         return InetAddress.getByName(hostName, hostAddress);
 333                     }
 334                 }
 335         );
 336         init();
 337     }
 338 
 339     /**
 340      * Constructor for the Socket.accept() method.
 341      * This creates an empty InetAddress, which is filled in by
 342      * the accept() method.  This InetAddress, however, is not
 343      * put in the address cache, since it is not created by name.
 344      */
 345     InetAddress() {
 346         holder = new InetAddressHolder();
 347     }
 348 
 349     /**
 350      * Replaces the de-serialized object with an Inet4Address object.
 351      *
 352      * @return the alternate object to the de-serialized object.
 353      *
 354      * @throws ObjectStreamException if a new object replacing this
 355      * object could not be created
 356      */
 357     @java.io.Serial
 358     private Object readResolve() throws ObjectStreamException {
 359         // will replace the deserialized 'this' object
 360         return new Inet4Address(holder().getHostName(), holder().getAddress());
 361     }
 362 
 363     /**
 364      * Utility routine to check if the InetAddress is an
 365      * IP multicast address.
 366      * @return a {@code boolean} indicating if the InetAddress is
 367      * an IP multicast address
 368      * @since   1.1
 369      */
 370     public boolean isMulticastAddress() {
 371         return false;
 372     }
 373 
 374     /**
 375      * Utility routine to check if the InetAddress is a wildcard address.
 376      * @return a {@code boolean} indicating if the InetAddress is
 377      *         a wildcard address.
 378      * @since 1.4
 379      */
 380     public boolean isAnyLocalAddress() {
 381         return false;
 382     }
 383 
 384     /**
 385      * Utility routine to check if the InetAddress is a loopback address.
 386      *
 387      * @return a {@code boolean} indicating if the InetAddress is
 388      * a loopback address; or false otherwise.
 389      * @since 1.4
 390      */
 391     public boolean isLoopbackAddress() {
 392         return false;
 393     }
 394 
 395     /**
 396      * Utility routine to check if the InetAddress is an link local address.
 397      *
 398      * @return a {@code boolean} indicating if the InetAddress is
 399      * a link local address; or false if address is not a link local unicast address.
 400      * @since 1.4
 401      */
 402     public boolean isLinkLocalAddress() {
 403         return false;
 404     }
 405 
 406     /**
 407      * Utility routine to check if the InetAddress is a site local address.
 408      *
 409      * @return a {@code boolean} indicating if the InetAddress is
 410      * a site local address; or false if address is not a site local unicast address.
 411      * @since 1.4
 412      */
 413     public boolean isSiteLocalAddress() {
 414         return false;
 415     }
 416 
 417     /**
 418      * Utility routine to check if the multicast address has global scope.
 419      *
 420      * @return a {@code boolean} indicating if the address has
 421      *         is a multicast address of global scope, false if it is not
 422      *         of global scope or it is not a multicast address
 423      * @since 1.4
 424      */
 425     public boolean isMCGlobal() {
 426         return false;
 427     }
 428 
 429     /**
 430      * Utility routine to check if the multicast address has node scope.
 431      *
 432      * @return a {@code boolean} indicating if the address has
 433      *         is a multicast address of node-local scope, false if it is not
 434      *         of node-local scope or it is not a multicast address
 435      * @since 1.4
 436      */
 437     public boolean isMCNodeLocal() {
 438         return false;
 439     }
 440 
 441     /**
 442      * Utility routine to check if the multicast address has link scope.
 443      *
 444      * @return a {@code boolean} indicating if the address has
 445      *         is a multicast address of link-local scope, false if it is not
 446      *         of link-local scope or it is not a multicast address
 447      * @since 1.4
 448      */
 449     public boolean isMCLinkLocal() {
 450         return false;
 451     }
 452 
 453     /**
 454      * Utility routine to check if the multicast address has site scope.
 455      *
 456      * @return a {@code boolean} indicating if the address has
 457      *         is a multicast address of site-local scope, false if it is not
 458      *         of site-local scope or it is not a multicast address
 459      * @since 1.4
 460      */
 461     public boolean isMCSiteLocal() {
 462         return false;
 463     }
 464 
 465     /**
 466      * Utility routine to check if the multicast address has organization scope.
 467      *
 468      * @return a {@code boolean} indicating if the address has
 469      *         is a multicast address of organization-local scope,
 470      *         false if it is not of organization-local scope
 471      *         or it is not a multicast address
 472      * @since 1.4
 473      */
 474     public boolean isMCOrgLocal() {
 475         return false;
 476     }
 477 
 478 
 479     /**
 480      * Test whether that address is reachable. Best effort is made by the
 481      * implementation to try to reach the host, but firewalls and server
 482      * configuration may block requests resulting in a unreachable status
 483      * while some specific ports may be accessible.
 484      * A typical implementation will use ICMP ECHO REQUESTs if the
 485      * privilege can be obtained, otherwise it will try to establish
 486      * a TCP connection on port 7 (Echo) of the destination host.
 487      * <p>
 488      * The timeout value, in milliseconds, indicates the maximum amount of time
 489      * the try should take. If the operation times out before getting an
 490      * answer, the host is deemed unreachable. A negative value will result
 491      * in an IllegalArgumentException being thrown.
 492      *
 493      * @param   timeout the time, in milliseconds, before the call aborts
 494      * @return a {@code boolean} indicating if the address is reachable.
 495      * @throws IOException if a network error occurs
 496      * @throws  IllegalArgumentException if {@code timeout} is negative.
 497      * @since 1.5
 498      */
 499     public boolean isReachable(int timeout) throws IOException {
 500         return isReachable(null, 0 , timeout);
 501     }
 502 
 503     /**
 504      * Test whether that address is reachable. Best effort is made by the
 505      * implementation to try to reach the host, but firewalls and server
 506      * configuration may block requests resulting in a unreachable status
 507      * while some specific ports may be accessible.
 508      * A typical implementation will use ICMP ECHO REQUESTs if the
 509      * privilege can be obtained, otherwise it will try to establish
 510      * a TCP connection on port 7 (Echo) of the destination host.
 511      * <p>
 512      * The {@code network interface} and {@code ttl} parameters
 513      * let the caller specify which network interface the test will go through
 514      * and the maximum number of hops the packets should go through.
 515      * A negative value for the {@code ttl} will result in an
 516      * IllegalArgumentException being thrown.
 517      * <p>
 518      * The timeout value, in milliseconds, indicates the maximum amount of time
 519      * the try should take. If the operation times out before getting an
 520      * answer, the host is deemed unreachable. A negative value will result
 521      * in an IllegalArgumentException being thrown.
 522      *
 523      * @param   netif   the NetworkInterface through which the
 524      *                    test will be done, or null for any interface
 525      * @param   ttl     the maximum numbers of hops to try or 0 for the
 526      *                  default
 527      * @param   timeout the time, in milliseconds, before the call aborts
 528      * @throws  IllegalArgumentException if either {@code timeout}
 529      *                          or {@code ttl} are negative.
 530      * @return a {@code boolean} indicating if the address is reachable.
 531      * @throws IOException if a network error occurs
 532      * @since 1.5
 533      */
 534     public boolean isReachable(NetworkInterface netif, int ttl,
 535                                int timeout) throws IOException {
 536         if (ttl < 0)
 537             throw new IllegalArgumentException("ttl can't be negative");
 538         if (timeout < 0)
 539             throw new IllegalArgumentException("timeout can't be negative");
 540 
 541         return impl.isReachable(this, timeout, netif, ttl);
 542     }
 543 
 544     /**
 545      * Gets the host name for this IP address.
 546      *
 547      * <p>If this InetAddress was created with a host name,
 548      * this host name will be remembered and returned;
 549      * otherwise, a reverse name lookup will be performed
 550      * and the result will be returned based on the system
 551      * configured name lookup service. If a lookup of the name service
 552      * is required, call
 553      * {@link #getCanonicalHostName() getCanonicalHostName}.
 554      *
 555      * <p>If there is a security manager, its
 556      * {@code checkConnect} method is first called
 557      * with the hostname and {@code -1}
 558      * as its arguments to see if the operation is allowed.
 559      * If the operation is not allowed, it will return
 560      * the textual representation of the IP address.
 561      *
 562      * @return  the host name for this IP address, or if the operation
 563      *    is not allowed by the security check, the textual
 564      *    representation of the IP address.
 565      *
 566      * @see InetAddress#getCanonicalHostName
 567      * @see SecurityManager#checkConnect
 568      */
 569     public String getHostName() {
 570         return getHostName(true);
 571     }
 572 
 573     /**
 574      * Returns the hostname for this address.
 575      * If the host is equal to null, then this address refers to any
 576      * of the local machine's available network addresses.
 577      * this is package private so SocketPermission can make calls into
 578      * here without a security check.
 579      *
 580      * <p>If there is a security manager, this method first
 581      * calls its {@code checkConnect} method
 582      * with the hostname and {@code -1}
 583      * as its arguments to see if the calling code is allowed to know
 584      * the hostname for this IP address, i.e., to connect to the host.
 585      * If the operation is not allowed, it will return
 586      * the textual representation of the IP address.
 587      *
 588      * @return  the host name for this IP address, or if the operation
 589      *    is not allowed by the security check, the textual
 590      *    representation of the IP address.
 591      *
 592      * @param check make security check if true
 593      *
 594      * @see SecurityManager#checkConnect
 595      */
 596     String getHostName(boolean check) {
 597         if (holder().getHostName() == null) {
 598             holder().hostName = InetAddress.getHostFromNameService(this, check);
 599         }
 600         return holder().getHostName();
 601     }
 602 
 603     /**
 604      * Gets the fully qualified domain name for this IP address.
 605      * Best effort method, meaning we may not be able to return
 606      * the FQDN depending on the underlying system configuration.
 607      *
 608      * <p>If there is a security manager, this method first
 609      * calls its {@code checkConnect} method
 610      * with the hostname and {@code -1}
 611      * as its arguments to see if the calling code is allowed to know
 612      * the hostname for this IP address, i.e., to connect to the host.
 613      * If the operation is not allowed, it will return
 614      * the textual representation of the IP address.
 615      *
 616      * @return  the fully qualified domain name for this IP address,
 617      *    or if the operation is not allowed by the security check,
 618      *    the textual representation of the IP address.
 619      *
 620      * @see SecurityManager#checkConnect
 621      *
 622      * @since 1.4
 623      */
 624     public String getCanonicalHostName() {
 625         String value = canonicalHostName;
 626         if (value == null)
 627             canonicalHostName = value =
 628                 InetAddress.getHostFromNameService(this, true);
 629         return value;
 630     }
 631 
 632     /**
 633      * Returns the hostname for this address.
 634      *
 635      * <p>If there is a security manager, this method first
 636      * calls its {@code checkConnect} method
 637      * with the hostname and {@code -1}
 638      * as its arguments to see if the calling code is allowed to know
 639      * the hostname for this IP address, i.e., to connect to the host.
 640      * If the operation is not allowed, it will return
 641      * the textual representation of the IP address.
 642      *
 643      * @return  the host name for this IP address, or if the operation
 644      *    is not allowed by the security check, the textual
 645      *    representation of the IP address.
 646      *
 647      * @param check make security check if true
 648      *
 649      * @see SecurityManager#checkConnect
 650      */
 651     private static String getHostFromNameService(InetAddress addr, boolean check) {
 652         String host = null;
 653             try {
 654                 // first lookup the hostname
 655                 host = nameService.getHostByAddr(addr.getAddress());
 656 
 657                 /* check to see if calling code is allowed to know
 658                  * the hostname for this IP address, ie, connect to the host
 659                  */
 660                 if (check) {
 661                     SecurityManager sec = System.getSecurityManager();
 662                     if (sec != null) {
 663                         sec.checkConnect(host, -1);
 664                     }
 665                 }
 666 
 667                 /* now get all the IP addresses for this hostname,
 668                  * and make sure one of them matches the original IP
 669                  * address. We do this to try and prevent spoofing.
 670                  */
 671 
 672                 InetAddress[] arr = InetAddress.getAllByName0(host, check);
 673                 boolean ok = false;
 674 
 675                 if(arr != null) {
 676                     for(int i = 0; !ok && i < arr.length; i++) {
 677                         ok = addr.equals(arr[i]);
 678                     }
 679                 }
 680 
 681                 //XXX: if it looks a spoof just return the address?
 682                 if (!ok) {
 683                     host = addr.getHostAddress();
 684                     return host;
 685                 }
 686             } catch (SecurityException e) {
 687                 host = addr.getHostAddress();
 688             } catch (UnknownHostException e) {
 689                 host = addr.getHostAddress();
 690                 // let next provider resolve the hostname
 691             }
 692         return host;
 693     }
 694 
 695     /**
 696      * Returns the raw IP address of this {@code InetAddress}
 697      * object. The result is in network byte order: the highest order
 698      * byte of the address is in {@code getAddress()[0]}.
 699      *
 700      * @return  the raw IP address of this object.
 701      */
 702     public byte[] getAddress() {
 703         return null;
 704     }
 705 
 706     /**
 707      * Returns the IP address string in textual presentation.
 708      *
 709      * @return  the raw IP address in a string format.
 710      * @since   1.0.2
 711      */
 712     public String getHostAddress() {
 713         return null;
 714      }
 715 
 716     /**
 717      * Returns a hashcode for this IP address.
 718      *
 719      * @return  a hash code value for this IP address.
 720      */
 721     public int hashCode() {
 722         return -1;
 723     }
 724 
 725     /**
 726      * Compares this object against the specified object.
 727      * The result is {@code true} if and only if the argument is
 728      * not {@code null} and it represents the same IP address as
 729      * this object.
 730      * <p>
 731      * Two instances of {@code InetAddress} represent the same IP
 732      * address if the length of the byte arrays returned by
 733      * {@code getAddress} is the same for both, and each of the
 734      * array components is the same for the byte arrays.
 735      *
 736      * @param   obj   the object to compare against.
 737      * @return  {@code true} if the objects are the same;
 738      *          {@code false} otherwise.
 739      * @see     java.net.InetAddress#getAddress()
 740      */
 741     public boolean equals(Object obj) {
 742         return false;
 743     }
 744 
 745     /**
 746      * Converts this IP address to a {@code String}. The
 747      * string returned is of the form: hostname / literal IP
 748      * address.
 749      *
 750      * If the host name is unresolved, no reverse name service lookup
 751      * is performed. The hostname part will be represented by an empty string.
 752      *
 753      * @return  a string representation of this IP address.
 754      */
 755     public String toString() {
 756         String hostName = holder().getHostName();
 757         return Objects.toString(hostName, "")
 758             + "/" + getHostAddress();
 759     }
 760 
 761     // mapping from host name to Addresses - either NameServiceAddresses (while
 762     // still being looked-up by NameService(s)) or CachedAddresses when cached
 763     private static final ConcurrentMap<String, Addresses> cache =
 764         new ConcurrentHashMap<>();
 765 
 766     // CachedAddresses that have to expire are kept ordered in this NavigableSet
 767     // which is scanned on each access
 768     private static final NavigableSet<CachedAddresses> expirySet =
 769         new ConcurrentSkipListSet<>();
 770 
 771     // common interface
 772     private interface Addresses {
 773         InetAddress[] get() throws UnknownHostException;
 774     }
 775 
 776     // a holder for cached addresses with required metadata
 777     private static final class CachedAddresses  implements Addresses, Comparable<CachedAddresses> {
 778         private static final AtomicLong seq = new AtomicLong();
 779         final String host;
 780         final InetAddress[] inetAddresses;
 781         final long expiryTime; // time of expiry (in terms of System.nanoTime())
 782         final long id = seq.incrementAndGet(); // each instance is unique
 783 
 784         CachedAddresses(String host, InetAddress[] inetAddresses, long expiryTime) {
 785             this.host = host;
 786             this.inetAddresses = inetAddresses;
 787             this.expiryTime = expiryTime;
 788         }
 789 
 790         @Override
 791         public InetAddress[] get() throws UnknownHostException {
 792             if (inetAddresses == null) {
 793                 throw new UnknownHostException(host);
 794             }
 795             return inetAddresses;
 796         }
 797 
 798         @Override
 799         public int compareTo(CachedAddresses other) {
 800             // natural order is expiry time -
 801             // compare difference of expiry times rather than
 802             // expiry times directly, to avoid possible overflow.
 803             // (see System.nanoTime() recommendations...)
 804             long diff = this.expiryTime - other.expiryTime;
 805             if (diff < 0L) return -1;
 806             if (diff > 0L) return 1;
 807             // ties are broken using unique id
 808             return Long.compare(this.id, other.id);
 809         }
 810     }
 811 
 812     // a name service lookup based Addresses implementation which replaces itself
 813     // in cache when the result is obtained
 814     private static final class NameServiceAddresses implements Addresses {
 815         private final String host;
 816         private final InetAddress reqAddr;
 817 
 818         NameServiceAddresses(String host, InetAddress reqAddr) {
 819             this.host = host;
 820             this.reqAddr = reqAddr;
 821         }
 822 
 823         @Override
 824         public InetAddress[] get() throws UnknownHostException {
 825             Addresses addresses;
 826             // only one thread is doing lookup to name service
 827             // for particular host at any time.
 828             synchronized (this) {
 829                 // re-check that we are still us + re-install us if slot empty
 830                 addresses = cache.putIfAbsent(host, this);
 831                 if (addresses == null) {
 832                     // this can happen when we were replaced by CachedAddresses in
 833                     // some other thread, then CachedAddresses expired and were
 834                     // removed from cache while we were waiting for lock...
 835                     addresses = this;
 836                 }
 837                 // still us ?
 838                 if (addresses == this) {
 839                     // lookup name services
 840                     InetAddress[] inetAddresses;
 841                     UnknownHostException ex;
 842                     int cachePolicy;
 843                     try {
 844                         inetAddresses = getAddressesFromNameService(host, reqAddr);
 845                         ex = null;
 846                         cachePolicy = InetAddressCachePolicy.get();
 847                     } catch (UnknownHostException uhe) {
 848                         inetAddresses = null;
 849                         ex = uhe;
 850                         cachePolicy = InetAddressCachePolicy.getNegative();
 851                     }
 852                     // remove or replace us with cached addresses according to cachePolicy
 853                     if (cachePolicy == InetAddressCachePolicy.NEVER) {
 854                         cache.remove(host, this);
 855                     } else {
 856                         CachedAddresses cachedAddresses = new CachedAddresses(
 857                             host,
 858                             inetAddresses,
 859                             cachePolicy == InetAddressCachePolicy.FOREVER
 860                             ? 0L
 861                             // cachePolicy is in [s] - we need [ns]
 862                             : System.nanoTime() + 1000_000_000L * cachePolicy
 863                         );
 864                         if (cache.replace(host, this, cachedAddresses) &&
 865                             cachePolicy != InetAddressCachePolicy.FOREVER) {
 866                             // schedule expiry
 867                             expirySet.add(cachedAddresses);
 868                         }
 869                     }
 870                     if (inetAddresses == null) {
 871                         throw ex == null ? new UnknownHostException(host) : ex;
 872                     }
 873                     return inetAddresses;
 874                 }
 875                 // else addresses != this
 876             }
 877             // delegate to different addresses when we are already replaced
 878             // but outside of synchronized block to avoid any chance of dead-locking
 879             return addresses.get();
 880         }
 881     }
 882 
 883     /**
 884      * NameService provides host and address lookup service
 885      *
 886      * @since 9
 887      */
 888     private interface NameService {
 889 
 890         /**
 891          * Lookup a host mapping by name. Retrieve the IP addresses
 892          * associated with a host
 893          *
 894          * @param host the specified hostname
 895          * @return array of IP addresses for the requested host
 896          * @throws UnknownHostException
 897          *             if no IP address for the {@code host} could be found
 898          */
 899         InetAddress[] lookupAllHostAddr(String host)
 900                 throws UnknownHostException;
 901 
 902         /**
 903          * Lookup the host corresponding to the IP address provided
 904          *
 905          * @param addr byte array representing an IP address
 906          * @return {@code String} representing the host name mapping
 907          * @throws UnknownHostException
 908          *             if no host found for the specified IP address
 909          */
 910         String getHostByAddr(byte[] addr) throws UnknownHostException;
 911 
 912     }
 913 
 914     /**
 915      * The default NameService implementation, which delegates to the underlying
 916      * OS network libraries to resolve host address mappings.
 917      *
 918      * @since 9
 919      */
 920     private static final class PlatformNameService implements NameService {
 921 
 922         public InetAddress[] lookupAllHostAddr(String host)
 923             throws UnknownHostException
 924         {
 925             return impl.lookupAllHostAddr(host);
 926         }
 927 
 928         public String getHostByAddr(byte[] addr)
 929             throws UnknownHostException
 930         {
 931             return impl.getHostByAddr(addr);
 932         }
 933     }
 934 
 935     /**
 936      * The HostsFileNameService provides host address mapping
 937      * by reading the entries in a hosts file, which is specified by
 938      * {@code jdk.net.hosts.file} system property
 939      *
 940      * <p>The file format is that which corresponds with the /etc/hosts file
 941      * IP Address host alias list.
 942      *
 943      * <p>When the file lookup is enabled it replaces the default NameService
 944      * implementation
 945      *
 946      * @since 9
 947      */
 948     private static final class HostsFileNameService implements NameService {
 949 
 950         private final String hostsFile;
 951 
 952         public HostsFileNameService (String hostsFileName) {
 953             this.hostsFile = hostsFileName;
 954         }
 955 
 956         private  String addrToString(byte addr[]) {
 957           String stringifiedAddress = null;
 958 
 959             if (addr.length == Inet4Address.INADDRSZ) {
 960                 stringifiedAddress = Inet4Address.numericToTextFormat(addr);
 961             } else { // treat as an IPV6 jobby
 962                 byte[] newAddr
 963                     = IPAddressUtil.convertFromIPv4MappedAddress(addr);
 964                 if (newAddr != null) {
 965                    stringifiedAddress = Inet4Address.numericToTextFormat(addr);
 966                 } else {
 967                     stringifiedAddress = Inet6Address.numericToTextFormat(addr);
 968                 }
 969             }
 970             return stringifiedAddress;
 971         }
 972 
 973         /**
 974          * Lookup the host name  corresponding to the IP address provided.
 975          * Search the configured host file a host name corresponding to
 976          * the specified IP address.
 977          *
 978          * @param addr byte array representing an IP address
 979          * @return {@code String} representing the host name mapping
 980          * @throws UnknownHostException
 981          *             if no host found for the specified IP address
 982          */
 983         @Override
 984         public String getHostByAddr(byte[] addr) throws UnknownHostException {
 985             String hostEntry;
 986             String host = null;
 987 
 988             try (Scanner hostsFileScanner = new Scanner(new File(hostsFile), "UTF-8")) {
 989                 while (hostsFileScanner.hasNextLine()) {
 990                     hostEntry = hostsFileScanner.nextLine();
 991                     if (!hostEntry.startsWith("#")) {
 992                         hostEntry = removeComments(hostEntry);
 993                         String[] mapping = hostEntry.split("\\s+");
 994                         if (mapping.length >= 2 &&
 995                             Arrays.equals(addr, createAddressByteArray(mapping[0]))) {
 996                             host = mapping[1];
 997                             break;
 998                         }
 999                     }
1000                 }
1001             } catch (FileNotFoundException e) {
1002                 throw new UnknownHostException("Unable to resolve address "
1003                         + Arrays.toString(addr) + " as hosts file " + hostsFile
1004                         + " not found ");
1005             }
1006 
1007             if ((host == null) || (host.isEmpty()) || (host.equals(" "))) {
1008                 throw new UnknownHostException("Requested address "
1009                         + Arrays.toString(addr)
1010                         + " resolves to an invalid entry in hosts file "
1011                         + hostsFile);
1012             }
1013             return host;
1014         }
1015 
1016         /**
1017          * <p>Lookup a host mapping by name. Retrieve the IP addresses
1018          * associated with a host.
1019          *
1020          * <p>Search the configured hosts file for the addresses associated
1021          * with the specified host name.
1022          *
1023          * @param host the specified hostname
1024          * @return array of IP addresses for the requested host
1025          * @throws UnknownHostException
1026          *             if no IP address for the {@code host} could be found
1027          */
1028         public InetAddress[] lookupAllHostAddr(String host)
1029                 throws UnknownHostException {
1030             String hostEntry;
1031             String addrStr = null;
1032             InetAddress[] res = null;
1033             byte addr[] = new byte[4];
1034             ArrayList<InetAddress> inetAddresses = null;
1035 
1036             // lookup the file and create a list InetAddress for the specified host
1037             try (Scanner hostsFileScanner = new Scanner(new File(hostsFile), "UTF-8")) {
1038                 while (hostsFileScanner.hasNextLine()) {
1039                     hostEntry = hostsFileScanner.nextLine();
1040                     if (!hostEntry.startsWith("#")) {
1041                         hostEntry = removeComments(hostEntry);
1042                         if (hostEntry.contains(host)) {
1043                             addrStr = extractHostAddr(hostEntry, host);
1044                             if ((addrStr != null) && (!addrStr.isEmpty())) {
1045                                 addr = createAddressByteArray(addrStr);
1046                                 if (inetAddresses == null) {
1047                                     inetAddresses = new ArrayList<>(1);
1048                                 }
1049                                 if (addr != null) {
1050                                     inetAddresses.add(InetAddress.getByAddress(host, addr));
1051                                 }
1052                             }
1053                         }
1054                     }
1055                 }
1056             } catch (FileNotFoundException e) {
1057                 throw new UnknownHostException("Unable to resolve host " + host
1058                         + " as hosts file " + hostsFile + " not found ");
1059             }
1060 
1061             if (inetAddresses != null) {
1062                 res = inetAddresses.toArray(new InetAddress[inetAddresses.size()]);
1063             } else {
1064                 throw new UnknownHostException("Unable to resolve host " + host
1065                         + " in hosts file " + hostsFile);
1066             }
1067             return res;
1068         }
1069 
1070         private String removeComments(String hostsEntry) {
1071             String filteredEntry = hostsEntry;
1072             int hashIndex;
1073 
1074             if ((hashIndex = hostsEntry.indexOf("#")) != -1) {
1075                 filteredEntry = hostsEntry.substring(0, hashIndex);
1076             }
1077             return filteredEntry;
1078         }
1079 
1080         private byte [] createAddressByteArray(String addrStr) {
1081             byte[] addrArray;
1082             // check if IPV4 address - most likely
1083             addrArray = IPAddressUtil.textToNumericFormatV4(addrStr);
1084             if (addrArray == null) {
1085                 addrArray = IPAddressUtil.textToNumericFormatV6(addrStr);
1086             }
1087             return addrArray;
1088         }
1089 
1090         /** host to ip address mapping */
1091         private String extractHostAddr(String hostEntry, String host) {
1092             String[] mapping = hostEntry.split("\\s+");
1093             String hostAddr = null;
1094 
1095             if (mapping.length >= 2) {
1096                 // look at the host aliases
1097                 for (int i = 1; i < mapping.length; i++) {
1098                     if (mapping[i].equalsIgnoreCase(host)) {
1099                         hostAddr = mapping[0];
1100                     }
1101                 }
1102             }
1103             return hostAddr;
1104         }
1105     }
1106 
1107     static final InetAddressImpl  impl;
1108 
1109     static {
1110         // create the impl
1111         impl = InetAddressImplFactory.create();
1112 
1113         // create name service
1114         nameService = createNameService();
1115         }
1116 
1117     /**
1118      * Create an instance of the NameService interface based on
1119      * the setting of the {@code jdk.net.hosts.file} system property.
1120      *
1121      * <p>The default NameService is the PlatformNameService, which typically
1122      * delegates name and address resolution calls to the underlying
1123      * OS network libraries.
1124      *
1125      * <p> A HostsFileNameService is created if the {@code jdk.net.hosts.file}
1126      * system property is set. If the specified file doesn't exist, the name or
1127      * address lookup will result in an UnknownHostException. Thus, non existent
1128      * hosts file is handled as if the file is empty.
1129      *
1130      * @return a NameService
1131      */
1132     private static NameService createNameService() {
1133 
1134         String hostsFileName =
1135                 GetPropertyAction.privilegedGetProperty("jdk.net.hosts.file");
1136         NameService theNameService;
1137         if (hostsFileName != null) {
1138             theNameService = new HostsFileNameService(hostsFileName);
1139         } else {
1140             theNameService = new PlatformNameService();
1141         }
1142         return theNameService;
1143     }
1144 
1145     /**
1146      * Creates an InetAddress based on the provided host name and IP address.
1147      * No name service is checked for the validity of the address.
1148      *
1149      * <p> The host name can either be a machine name, such as
1150      * "{@code www.example.com}", or a textual representation of its IP
1151      * address.
1152      * <p> No validity checking is done on the host name either.
1153      *
1154      * <p> If addr specifies an IPv4 address an instance of Inet4Address
1155      * will be returned; otherwise, an instance of Inet6Address
1156      * will be returned.
1157      *
1158      * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
1159      * must be 16 bytes long
1160      *
1161      * @param host the specified host
1162      * @param addr the raw IP address in network byte order
1163      * @return  an InetAddress object created from the raw IP address.
1164      * @exception  UnknownHostException  if IP address is of illegal length
1165      * @since 1.4
1166      */
1167     public static InetAddress getByAddress(String host, byte[] addr)
1168         throws UnknownHostException {
1169         if (host != null && !host.isEmpty() && host.charAt(0) == '[') {
1170             if (host.charAt(host.length()-1) == ']') {
1171                 host = host.substring(1, host.length() -1);
1172             }
1173         }
1174         if (addr != null) {
1175             if (addr.length == Inet4Address.INADDRSZ) {
1176                 return new Inet4Address(host, addr);
1177             } else if (addr.length == Inet6Address.INADDRSZ) {
1178                 byte[] newAddr
1179                     = IPAddressUtil.convertFromIPv4MappedAddress(addr);
1180                 if (newAddr != null) {
1181                     return new Inet4Address(host, newAddr);
1182                 } else {
1183                     return new Inet6Address(host, addr);
1184                 }
1185             }
1186         }
1187         throw new UnknownHostException("addr is of illegal length");
1188     }
1189 
1190 
1191     /**
1192      * Determines the IP address of a host, given the host's name.
1193      *
1194      * <p> The host name can either be a machine name, such as
1195      * "{@code www.example.com}", or a textual representation of its
1196      * IP address. If a literal IP address is supplied, only the
1197      * validity of the address format is checked.
1198      *
1199      * <p> For {@code host} specified in literal IPv6 address,
1200      * either the form defined in RFC 2732 or the literal IPv6 address
1201      * format defined in RFC 2373 is accepted. IPv6 scoped addresses are also
1202      * supported. See <a href="Inet6Address.html#scoped">here</a> for a description of IPv6
1203      * scoped addresses.
1204      *
1205      * <p> If the host is {@code null} or {@code host.length()} is equal
1206      * to zero, then an {@code InetAddress} representing an address of the
1207      * loopback interface is returned.
1208      * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC&nbsp;3330</a>
1209      * section&nbsp;2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC&nbsp;2373</a>
1210      * section&nbsp;2.5.3.
1211      *
1212      * <p> If there is a security manager, and {@code host} is not {@code null}
1213      * or {@code host.length() } is not equal to zero, the security manager's
1214      * {@code checkConnect} method is called with the hostname and {@code -1}
1215      * as its arguments to determine if the operation is allowed.
1216      *
1217      * @param      host   the specified host, or {@code null}.
1218      * @return     an IP address for the given host name.
1219      * @exception  UnknownHostException  if no IP address for the
1220      *               {@code host} could be found, or if a scope_id was specified
1221      *               for a global IPv6 address.
1222      * @exception  SecurityException if a security manager exists
1223      *             and its checkConnect method doesn't allow the operation
1224      */
1225     public static InetAddress getByName(String host)
1226         throws UnknownHostException {
1227         return InetAddress.getAllByName(host)[0];
1228     }
1229 
1230     // called from deployment cache manager
1231     private static InetAddress getByName(String host, InetAddress reqAddr)
1232         throws UnknownHostException {
1233         return InetAddress.getAllByName(host, reqAddr)[0];
1234     }
1235 
1236     /**
1237      * Given the name of a host, returns an array of its IP addresses,
1238      * based on the configured name service on the system.
1239      *
1240      * <p> The host name can either be a machine name, such as
1241      * "{@code www.example.com}", or a textual representation of its IP
1242      * address. If a literal IP address is supplied, only the
1243      * validity of the address format is checked.
1244      *
1245      * <p> For {@code host} specified in <i>literal IPv6 address</i>,
1246      * either the form defined in RFC 2732 or the literal IPv6 address
1247      * format defined in RFC 2373 is accepted. A literal IPv6 address may
1248      * also be qualified by appending a scoped zone identifier or scope_id.
1249      * The syntax and usage of scope_ids is described
1250      * <a href="Inet6Address.html#scoped">here</a>.
1251      *
1252      * <p> If the host is {@code null} or {@code host.length()} is equal
1253      * to zero, then an {@code InetAddress} representing an address of the
1254      * loopback interface is returned.
1255      * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC&nbsp;3330</a>
1256      * section&nbsp;2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC&nbsp;2373</a>
1257      * section&nbsp;2.5.3. </p>
1258      *
1259      * <p> If there is a security manager, and {@code host} is not {@code null}
1260      * or {@code host.length() } is not equal to zero, the security manager's
1261      * {@code checkConnect} method is called with the hostname and {@code -1}
1262      * as its arguments to determine if the operation is allowed.
1263      *
1264      * @param      host   the name of the host, or {@code null}.
1265      * @return     an array of all the IP addresses for a given host name.
1266      *
1267      * @exception  UnknownHostException  if no IP address for the
1268      *               {@code host} could be found, or if a scope_id was specified
1269      *               for a global IPv6 address.
1270      * @exception  SecurityException  if a security manager exists and its
1271      *               {@code checkConnect} method doesn't allow the operation.
1272      *
1273      * @see SecurityManager#checkConnect
1274      */
1275     public static InetAddress[] getAllByName(String host)
1276         throws UnknownHostException {
1277         return getAllByName(host, null);
1278     }
1279 
1280     private static InetAddress[] getAllByName(String host, InetAddress reqAddr)
1281         throws UnknownHostException {
1282 
1283         if (host == null || host.isEmpty()) {
1284             InetAddress[] ret = new InetAddress[1];
1285             ret[0] = impl.loopbackAddress();
1286             return ret;
1287         }
1288 
1289         boolean ipv6Expected = false;
1290         if (host.charAt(0) == '[') {
1291             // This is supposed to be an IPv6 literal
1292             if (host.length() > 2 && host.charAt(host.length()-1) == ']') {
1293                 host = host.substring(1, host.length() -1);
1294                 ipv6Expected = true;
1295             } else {
1296                 // This was supposed to be a IPv6 address, but it's not!
1297                 throw new UnknownHostException(host + ": invalid IPv6 address");
1298             }
1299         }
1300 
1301         // if host is an IP address, we won't do further lookup
1302         if (Character.digit(host.charAt(0), 16) != -1
1303             || (host.charAt(0) == ':')) {
1304             byte[] addr = null;
1305             int numericZone = -1;
1306             String ifname = null;
1307             // see if it is IPv4 address
1308             addr = IPAddressUtil.textToNumericFormatV4(host);
1309             if (addr == null) {
1310                 // This is supposed to be an IPv6 literal
1311                 // Check if a numeric or string zone id is present
1312                 int pos;
1313                 if ((pos=host.indexOf ('%')) != -1) {
1314                     numericZone = checkNumericZone (host);
1315                     if (numericZone == -1) { /* remainder of string must be an ifname */
1316                         ifname = host.substring (pos+1);
1317                     }
1318                 }
1319                 if ((addr = IPAddressUtil.textToNumericFormatV6(host)) == null && host.contains(":")) {
1320                     throw new UnknownHostException(host + ": invalid IPv6 address");
1321                 }
1322             } else if (ipv6Expected) {
1323                 // Means an IPv4 literal between brackets!
1324                 throw new UnknownHostException("["+host+"]");
1325             }
1326             InetAddress[] ret = new InetAddress[1];
1327             if(addr != null) {
1328                 if (addr.length == Inet4Address.INADDRSZ) {
1329                     ret[0] = new Inet4Address(null, addr);
1330                 } else {
1331                     if (ifname != null) {
1332                         ret[0] = new Inet6Address(null, addr, ifname);
1333                     } else {
1334                         ret[0] = new Inet6Address(null, addr, numericZone);
1335                     }
1336                 }
1337                 return ret;
1338             }
1339         } else if (ipv6Expected) {
1340             // We were expecting an IPv6 Literal, but got something else
1341             throw new UnknownHostException("["+host+"]");
1342         }
1343         return getAllByName0(host, reqAddr, true, true);
1344     }
1345 
1346     /**
1347      * Returns the loopback address.
1348      * <p>
1349      * The InetAddress returned will represent the IPv4
1350      * loopback address, 127.0.0.1, or the IPv6 loopback
1351      * address, ::1. The IPv4 loopback address returned
1352      * is only one of many in the form 127.*.*.*
1353      *
1354      * @return  the InetAddress loopback instance.
1355      * @since 1.7
1356      */
1357     public static InetAddress getLoopbackAddress() {
1358         return impl.loopbackAddress();
1359     }
1360 
1361 
1362     /**
1363      * check if the literal address string has %nn appended
1364      * returns -1 if not, or the numeric value otherwise.
1365      *
1366      * %nn may also be a string that represents the displayName of
1367      * a currently available NetworkInterface.
1368      */
1369     private static int checkNumericZone (String s) throws UnknownHostException {
1370         int percent = s.indexOf ('%');
1371         int slen = s.length();
1372         int digit, zone=0;
1373         if (percent == -1) {
1374             return -1;
1375         }
1376         for (int i=percent+1; i<slen; i++) {
1377             char c = s.charAt(i);
1378             if (c == ']') {
1379                 if (i == percent+1) {
1380                     /* empty per-cent field */
1381                     return -1;
1382                 }
1383                 break;
1384             }
1385             if ((digit = Character.digit (c, 10)) < 0) {
1386                 return -1;
1387             }
1388             zone = (zone * 10) + digit;
1389         }
1390         return zone;
1391     }
1392 
1393     private static InetAddress[] getAllByName0 (String host)
1394         throws UnknownHostException
1395     {
1396         return getAllByName0(host, true);
1397     }
1398 
1399     /**
1400      * package private so SocketPermission can call it
1401      */
1402     static InetAddress[] getAllByName0 (String host, boolean check)
1403         throws UnknownHostException  {
1404         return getAllByName0 (host, null, check, true);
1405     }
1406 
1407     /**
1408      * Designated lookup method.
1409      *
1410      * @param host host name to look up
1411      * @param reqAddr requested address to be the 1st in returned array
1412      * @param check perform security check
1413      * @param useCache use cached value if not expired else always
1414      *                 perform name service lookup (and cache the result)
1415      * @return array of InetAddress(es)
1416      * @throws UnknownHostException if host name is not found
1417      */
1418     private static InetAddress[] getAllByName0(String host,
1419                                                InetAddress reqAddr,
1420                                                boolean check,
1421                                                boolean useCache)
1422         throws UnknownHostException  {
1423 
1424         /* If it gets here it is presumed to be a hostname */
1425 
1426         /* make sure the connection to the host is allowed, before we
1427          * give out a hostname
1428          */
1429         if (check) {
1430             SecurityManager security = System.getSecurityManager();
1431             if (security != null) {
1432                 security.checkConnect(host, -1);
1433             }
1434         }
1435 
1436         // remove expired addresses from cache - expirySet keeps them ordered
1437         // by expiry time so we only need to iterate the prefix of the NavigableSet...
1438         long now = System.nanoTime();
1439         for (CachedAddresses caddrs : expirySet) {
1440             // compare difference of time instants rather than
1441             // time instants directly, to avoid possible overflow.
1442             // (see System.nanoTime() recommendations...)
1443             if ((caddrs.expiryTime - now) < 0L) {
1444                 // ConcurrentSkipListSet uses weakly consistent iterator,
1445                 // so removing while iterating is OK...
1446                 if (expirySet.remove(caddrs)) {
1447                     // ... remove from cache
1448                     cache.remove(caddrs.host, caddrs);
1449                 }
1450             } else {
1451                 // we encountered 1st element that expires in future
1452                 break;
1453             }
1454         }
1455 
1456         // look-up or remove from cache
1457         Addresses addrs;
1458         if (useCache) {
1459             addrs = cache.get(host);
1460         } else {
1461             addrs = cache.remove(host);
1462             if (addrs != null) {
1463                 if (addrs instanceof CachedAddresses) {
1464                     // try removing from expirySet too if CachedAddresses
1465                     expirySet.remove(addrs);
1466                 }
1467                 addrs = null;
1468             }
1469         }
1470 
1471         if (addrs == null) {
1472             // create a NameServiceAddresses instance which will look up
1473             // the name service and install it within cache...
1474             Addresses oldAddrs = cache.putIfAbsent(
1475                 host,
1476                 addrs = new NameServiceAddresses(host, reqAddr)
1477             );
1478             if (oldAddrs != null) { // lost putIfAbsent race
1479                 addrs = oldAddrs;
1480             }
1481         }
1482 
1483         // ask Addresses to get an array of InetAddress(es) and clone it
1484         return addrs.get().clone();
1485     }
1486 
1487     static InetAddress[] getAddressesFromNameService(String host, InetAddress reqAddr)
1488         throws UnknownHostException
1489     {
1490         InetAddress[] addresses = null;
1491         UnknownHostException ex = null;
1492 
1493             try {
1494                 addresses = nameService.lookupAllHostAddr(host);
1495             } catch (UnknownHostException uhe) {
1496                 if (host.equalsIgnoreCase("localhost")) {
1497                     addresses = new InetAddress[] { impl.loopbackAddress() };
1498                 }
1499                 else {
1500                     ex = uhe;
1501                 }
1502             }
1503 
1504         if (addresses == null) {
1505             throw ex == null ? new UnknownHostException(host) : ex;
1506         }
1507 
1508         // More to do?
1509         if (reqAddr != null && addresses.length > 1 && !addresses[0].equals(reqAddr)) {
1510             // Find it?
1511             int i = 1;
1512             for (; i < addresses.length; i++) {
1513                 if (addresses[i].equals(reqAddr)) {
1514                     break;
1515                 }
1516             }
1517             // Rotate
1518             if (i < addresses.length) {
1519                 InetAddress tmp, tmp2 = reqAddr;
1520                 for (int j = 0; j < i; j++) {
1521                     tmp = addresses[j];
1522                     addresses[j] = tmp2;
1523                     tmp2 = tmp;
1524                 }
1525                 addresses[i] = tmp2;
1526             }
1527         }
1528 
1529         return addresses;
1530     }
1531 
1532     /**
1533      * Returns an {@code InetAddress} object given the raw IP address .
1534      * The argument is in network byte order: the highest order
1535      * byte of the address is in {@code getAddress()[0]}.
1536      *
1537      * <p> This method doesn't block, i.e. no reverse name service lookup
1538      * is performed.
1539      *
1540      * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
1541      * must be 16 bytes long
1542      *
1543      * @param addr the raw IP address in network byte order
1544      * @return  an InetAddress object created from the raw IP address.
1545      * @exception  UnknownHostException  if IP address is of illegal length
1546      * @since 1.4
1547      */
1548     public static InetAddress getByAddress(byte[] addr)
1549         throws UnknownHostException {
1550         return getByAddress(null, addr);
1551     }
1552 
1553     private static final class CachedLocalHost {
1554         final String host;
1555         final InetAddress addr;
1556         final long expiryTime = System.nanoTime() + 5000_000_000L; // now + 5s;
1557 
1558         CachedLocalHost(String host, InetAddress addr) {
1559             this.host = host;
1560             this.addr = addr;
1561         }
1562     }
1563 
1564     private static volatile CachedLocalHost cachedLocalHost;
1565 
1566     /**
1567      * Returns the address of the local host. This is achieved by retrieving
1568      * the name of the host from the system, then resolving that name into
1569      * an {@code InetAddress}.
1570      *
1571      * <P>Note: The resolved address may be cached for a short period of time.
1572      * </P>
1573      *
1574      * <p>If there is a security manager, its
1575      * {@code checkConnect} method is called
1576      * with the local host name and {@code -1}
1577      * as its arguments to see if the operation is allowed.
1578      * If the operation is not allowed, an InetAddress representing
1579      * the loopback address is returned.
1580      *
1581      * @return     the address of the local host.
1582      *
1583      * @exception  UnknownHostException  if the local host name could not
1584      *             be resolved into an address.
1585      *
1586      * @see SecurityManager#checkConnect
1587      * @see java.net.InetAddress#getByName(java.lang.String)
1588      */
1589     public static InetAddress getLocalHost() throws UnknownHostException {
1590 
1591         SecurityManager security = System.getSecurityManager();
1592         try {
1593             // is cached data still valid?
1594             CachedLocalHost clh = cachedLocalHost;
1595             if (clh != null && (clh.expiryTime - System.nanoTime()) >= 0L) {
1596                 if (security != null) {
1597                     security.checkConnect(clh.host, -1);
1598                 }
1599                 return clh.addr;
1600             }
1601 
1602             String local = impl.getLocalHostName();
1603 
1604             if (security != null) {
1605                 security.checkConnect(local, -1);
1606             }
1607 
1608             InetAddress localAddr;
1609             if (local.equals("localhost")) {
1610                 // shortcut for "localhost" host name
1611                 localAddr = impl.loopbackAddress();
1612             } else {
1613                 // call getAllByName0 without security checks and
1614                 // without using cached data
1615                 try {
1616                     localAddr = getAllByName0(local, null, false, false)[0];
1617                 } catch (UnknownHostException uhe) {
1618                     // Rethrow with a more informative error message.
1619                     UnknownHostException uhe2 =
1620                         new UnknownHostException(local + ": " +
1621                                                  uhe.getMessage());
1622                     uhe2.initCause(uhe);
1623                     throw uhe2;
1624                 }
1625             }
1626             cachedLocalHost = new CachedLocalHost(local, localAddr);
1627             return localAddr;
1628         } catch (java.lang.SecurityException e) {
1629             return impl.loopbackAddress();
1630         }
1631     }
1632 
1633     /**
1634      * Perform class load-time initializations.
1635      */
1636     private static native void init();
1637 
1638 
1639     /*
1640      * Returns the InetAddress representing anyLocalAddress
1641      * (typically 0.0.0.0 or ::0)
1642      */
1643     static InetAddress anyLocalAddress() {
1644         return impl.anyLocalAddress();
1645     }
1646 
1647     /*
1648      * Load and instantiate an underlying impl class
1649      */
1650     static InetAddressImpl loadImpl(String implName) {
1651         Object impl = null;
1652 
1653         /*
1654          * Property "impl.prefix" will be prepended to the classname
1655          * of the implementation object we instantiate, to which we
1656          * delegate the real work (like native methods).  This
1657          * property can vary across implementations of the java.
1658          * classes.  The default is an empty String "".
1659          */
1660         String prefix = GetPropertyAction.privilegedGetProperty("impl.prefix", "");
1661         try {
1662             @SuppressWarnings("deprecation")
1663             Object tmp = Class.forName("java.net." + prefix + implName).newInstance();
1664             impl = tmp;
1665         } catch (ClassNotFoundException e) {
1666             System.err.println("Class not found: java.net." + prefix +
1667                                implName + ":\ncheck impl.prefix property " +
1668                                "in your properties file.");
1669         } catch (InstantiationException e) {
1670             System.err.println("Could not instantiate: java.net." + prefix +
1671                                implName + ":\ncheck impl.prefix property " +
1672                                "in your properties file.");
1673         } catch (IllegalAccessException e) {
1674             System.err.println("Cannot access class: java.net." + prefix +
1675                                implName + ":\ncheck impl.prefix property " +
1676                                "in your properties file.");
1677         }
1678 
1679         if (impl == null) {
1680             try {
1681                 @SuppressWarnings("deprecation")
1682                 Object tmp = Class.forName(implName).newInstance();
1683                 impl = tmp;
1684             } catch (Exception e) {
1685                 throw new Error("System property impl.prefix incorrect");
1686             }
1687         }
1688 
1689         return (InetAddressImpl) impl;
1690     }
1691 
1692     @java.io.Serial
1693     private void readObjectNoData () {
1694         if (getClass().getClassLoader() != null) {
1695             throw new SecurityException ("invalid address type");
1696         }
1697     }
1698 
1699     private static final jdk.internal.misc.Unsafe UNSAFE
1700             = jdk.internal.misc.Unsafe.getUnsafe();
1701     private static final long FIELDS_OFFSET
1702             = UNSAFE.objectFieldOffset(InetAddress.class, "holder");
1703 
1704     @java.io.Serial
1705     private void readObject (ObjectInputStream s) throws
1706                          IOException, ClassNotFoundException {
1707         if (getClass().getClassLoader() != null) {
1708             throw new SecurityException ("invalid address type");
1709         }
1710         GetField gf = s.readFields();
1711         String host = (String)gf.get("hostName", null);
1712         int address = gf.get("address", 0);
1713         int family = gf.get("family", 0);
1714         if (family != IPv4 && family != IPv6) {
1715             throw new InvalidObjectException("invalid address family type: " + family);
1716         }
1717         InetAddressHolder h = new InetAddressHolder(host, address, family);
1718         UNSAFE.putReference(this, FIELDS_OFFSET, h);
1719     }
1720 
1721     /* needed because the serializable fields no longer exist */
1722 
1723     /**
1724      * @serialField hostName String
1725      * @serialField address int
1726      * @serialField family int
1727      */
1728     @java.io.Serial
1729     private static final ObjectStreamField[] serialPersistentFields = {
1730         new ObjectStreamField("hostName", String.class),
1731         new ObjectStreamField("address", int.class),
1732         new ObjectStreamField("family", int.class),
1733     };
1734 
1735     @java.io.Serial
1736     private void writeObject (ObjectOutputStream s) throws
1737                         IOException {
1738         if (getClass().getClassLoader() != null) {
1739             throw new SecurityException ("invalid address type");
1740         }
1741         PutField pf = s.putFields();
1742         pf.put("hostName", holder().getHostName());
1743         pf.put("address", holder().getAddress());
1744         pf.put("family", holder().getFamily());
1745         s.writeFields();
1746     }
1747 }
1748 
1749 /*
1750  * Simple factory to create the impl
1751  */
1752 class InetAddressImplFactory {
1753 
1754     static InetAddressImpl create() {
1755         return InetAddress.loadImpl(isIPv6Supported() ?
1756                                     "Inet6AddressImpl" : "Inet4AddressImpl");
1757     }
1758 
1759     static native boolean isIPv6Supported();
1760 }