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 = null;
 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     private static final long serialVersionUID = 3286316764910316507L;
 303 
 304     /*
 305      * Load net library into runtime, and perform initializations.
 306      */
 307     static {
 308         String str = java.security.AccessController.doPrivileged(
 309                 new GetPropertyAction("java.net.preferIPv6Addresses"));
 310         if (str == null) {
 311             preferIPv6Address = PREFER_IPV6_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         AccessController.doPrivileged(
 322             new java.security.PrivilegedAction<>() {
 323                 public Void run() {
 324                     System.loadLibrary("net");
 325                     return null;
 326                 }
 327             });
 328         SharedSecrets.setJavaNetInetAddressAccess(
 329                 new JavaNetInetAddressAccess() {
 330                     public String getOriginalHostName(InetAddress ia) {
 331                         return ia.holder.getOriginalHostName();
 332                     }
 333 
 334                     public InetAddress getByName(String hostName,
 335                                                  InetAddress hostAddress)
 336                             throws UnknownHostException
 337                     {
 338                         return InetAddress.getByName(hostName, hostAddress);
 339                     }
 340                 }
 341         );
 342         init();
 343     }
 344 
 345     /**
 346      * Constructor for the Socket.accept() method.
 347      * This creates an empty InetAddress, which is filled in by
 348      * the accept() method.  This InetAddress, however, is not
 349      * put in the address cache, since it is not created by name.
 350      */
 351     InetAddress() {
 352         holder = new InetAddressHolder();
 353     }
 354 
 355     /**
 356      * Replaces the de-serialized object with an Inet4Address object.
 357      *
 358      * @return the alternate object to the de-serialized object.
 359      *
 360      * @throws ObjectStreamException if a new object replacing this
 361      * object could not be created
 362      */
 363     private Object readResolve() throws ObjectStreamException {
 364         // will replace the deserialized 'this' object
 365         return new Inet4Address(holder().getHostName(), holder().getAddress());
 366     }
 367 
 368     /**
 369      * Utility routine to check if the InetAddress is an
 370      * IP multicast address.
 371      * @return a {@code boolean} indicating if the InetAddress is
 372      * an IP multicast address
 373      * @since   1.1
 374      */
 375     public boolean isMulticastAddress() {
 376         return false;
 377     }
 378 
 379     /**
 380      * Utility routine to check if the InetAddress is a wildcard address.
 381      * @return a {@code boolean} indicating if the InetAddress is
 382      *         a wildcard address.
 383      * @since 1.4
 384      */
 385     public boolean isAnyLocalAddress() {
 386         return false;
 387     }
 388 
 389     /**
 390      * Utility routine to check if the InetAddress is a loopback address.
 391      *
 392      * @return a {@code boolean} indicating if the InetAddress is
 393      * a loopback address; or false otherwise.
 394      * @since 1.4
 395      */
 396     public boolean isLoopbackAddress() {
 397         return false;
 398     }
 399 
 400     /**
 401      * Utility routine to check if the InetAddress is an link local address.
 402      *
 403      * @return a {@code boolean} indicating if the InetAddress is
 404      * a link local address; or false if address is not a link local unicast address.
 405      * @since 1.4
 406      */
 407     public boolean isLinkLocalAddress() {
 408         return false;
 409     }
 410 
 411     /**
 412      * Utility routine to check if the InetAddress is a site local address.
 413      *
 414      * @return a {@code boolean} indicating if the InetAddress is
 415      * a site local address; or false if address is not a site local unicast address.
 416      * @since 1.4
 417      */
 418     public boolean isSiteLocalAddress() {
 419         return false;
 420     }
 421 
 422     /**
 423      * Utility routine to check if the multicast address has global scope.
 424      *
 425      * @return a {@code boolean} indicating if the address has
 426      *         is a multicast address of global scope, false if it is not
 427      *         of global scope or it is not a multicast address
 428      * @since 1.4
 429      */
 430     public boolean isMCGlobal() {
 431         return false;
 432     }
 433 
 434     /**
 435      * Utility routine to check if the multicast address has node scope.
 436      *
 437      * @return a {@code boolean} indicating if the address has
 438      *         is a multicast address of node-local scope, false if it is not
 439      *         of node-local scope or it is not a multicast address
 440      * @since 1.4
 441      */
 442     public boolean isMCNodeLocal() {
 443         return false;
 444     }
 445 
 446     /**
 447      * Utility routine to check if the multicast address has link scope.
 448      *
 449      * @return a {@code boolean} indicating if the address has
 450      *         is a multicast address of link-local scope, false if it is not
 451      *         of link-local scope or it is not a multicast address
 452      * @since 1.4
 453      */
 454     public boolean isMCLinkLocal() {
 455         return false;
 456     }
 457 
 458     /**
 459      * Utility routine to check if the multicast address has site scope.
 460      *
 461      * @return a {@code boolean} indicating if the address has
 462      *         is a multicast address of site-local scope, false if it is not
 463      *         of site-local scope or it is not a multicast address
 464      * @since 1.4
 465      */
 466     public boolean isMCSiteLocal() {
 467         return false;
 468     }
 469 
 470     /**
 471      * Utility routine to check if the multicast address has organization scope.
 472      *
 473      * @return a {@code boolean} indicating if the address has
 474      *         is a multicast address of organization-local scope,
 475      *         false if it is not of organization-local scope
 476      *         or it is not a multicast address
 477      * @since 1.4
 478      */
 479     public boolean isMCOrgLocal() {
 480         return false;
 481     }
 482 
 483 
 484     /**
 485      * Test whether that address is reachable. Best effort is made by the
 486      * implementation to try to reach the host, but firewalls and server
 487      * configuration may block requests resulting in a unreachable status
 488      * while some specific ports may be accessible.
 489      * A typical implementation will use ICMP ECHO REQUESTs if the
 490      * privilege can be obtained, otherwise it will try to establish
 491      * a TCP connection on port 7 (Echo) of the destination host.
 492      * <p>
 493      * The timeout value, in milliseconds, indicates the maximum amount of time
 494      * the try should take. If the operation times out before getting an
 495      * answer, the host is deemed unreachable. A negative value will result
 496      * in an IllegalArgumentException being thrown.
 497      *
 498      * @param   timeout the time, in milliseconds, before the call aborts
 499      * @return a {@code boolean} indicating if the address is reachable.
 500      * @throws IOException if a network error occurs
 501      * @throws  IllegalArgumentException if {@code timeout} is negative.
 502      * @since 1.5
 503      */
 504     public boolean isReachable(int timeout) throws IOException {
 505         return isReachable(null, 0 , timeout);
 506     }
 507 
 508     /**
 509      * Test whether that address is reachable. Best effort is made by the
 510      * implementation to try to reach the host, but firewalls and server
 511      * configuration may block requests resulting in a unreachable status
 512      * while some specific ports may be accessible.
 513      * A typical implementation will use ICMP ECHO REQUESTs if the
 514      * privilege can be obtained, otherwise it will try to establish
 515      * a TCP connection on port 7 (Echo) of the destination host.
 516      * <p>
 517      * The {@code network interface} and {@code ttl} parameters
 518      * let the caller specify which network interface the test will go through
 519      * and the maximum number of hops the packets should go through.
 520      * A negative value for the {@code ttl} will result in an
 521      * IllegalArgumentException being thrown.
 522      * <p>
 523      * The timeout value, in milliseconds, indicates the maximum amount of time
 524      * the try should take. If the operation times out before getting an
 525      * answer, the host is deemed unreachable. A negative value will result
 526      * in an IllegalArgumentException being thrown.
 527      *
 528      * @param   netif   the NetworkInterface through which the
 529      *                    test will be done, or null for any interface
 530      * @param   ttl     the maximum numbers of hops to try or 0 for the
 531      *                  default
 532      * @param   timeout the time, in milliseconds, before the call aborts
 533      * @throws  IllegalArgumentException if either {@code timeout}
 534      *                          or {@code ttl} are negative.
 535      * @return a {@code boolean} indicating if the address is reachable.
 536      * @throws IOException if a network error occurs
 537      * @since 1.5
 538      */
 539     public boolean isReachable(NetworkInterface netif, int ttl,
 540                                int timeout) throws IOException {
 541         if (ttl < 0)
 542             throw new IllegalArgumentException("ttl can't be negative");
 543         if (timeout < 0)
 544             throw new IllegalArgumentException("timeout can't be negative");
 545 
 546         return impl.isReachable(this, timeout, netif, ttl);
 547     }
 548 
 549     /**
 550      * Gets the host name for this IP address.
 551      *
 552      * <p>If this InetAddress was created with a host name,
 553      * this host name will be remembered and returned;
 554      * otherwise, a reverse name lookup will be performed
 555      * and the result will be returned based on the system
 556      * configured name lookup service. If a lookup of the name service
 557      * is required, call
 558      * {@link #getCanonicalHostName() getCanonicalHostName}.
 559      *
 560      * <p>If there is a security manager, its
 561      * {@code checkConnect} method is first called
 562      * with the hostname and {@code -1}
 563      * as its arguments to see if the operation is allowed.
 564      * If the operation is not allowed, it will return
 565      * the textual representation of the IP address.
 566      *
 567      * @return  the host name for this IP address, or if the operation
 568      *    is not allowed by the security check, the textual
 569      *    representation of the IP address.
 570      *
 571      * @see InetAddress#getCanonicalHostName
 572      * @see SecurityManager#checkConnect
 573      */
 574     public String getHostName() {
 575         return getHostName(true);
 576     }
 577 
 578     /**
 579      * Returns the hostname for this address.
 580      * If the host is equal to null, then this address refers to any
 581      * of the local machine's available network addresses.
 582      * this is package private so SocketPermission can make calls into
 583      * here without a security check.
 584      *
 585      * <p>If there is a security manager, this method first
 586      * calls its {@code checkConnect} method
 587      * with the hostname and {@code -1}
 588      * as its arguments to see if the calling code is allowed to know
 589      * the hostname for this IP address, i.e., to connect to the host.
 590      * If the operation is not allowed, it will return
 591      * the textual representation of the IP address.
 592      *
 593      * @return  the host name for this IP address, or if the operation
 594      *    is not allowed by the security check, the textual
 595      *    representation of the IP address.
 596      *
 597      * @param check make security check if true
 598      *
 599      * @see SecurityManager#checkConnect
 600      */
 601     String getHostName(boolean check) {
 602         if (holder().getHostName() == null) {
 603             holder().hostName = InetAddress.getHostFromNameService(this, check);
 604         }
 605         return holder().getHostName();
 606     }
 607 
 608     /**
 609      * Gets the fully qualified domain name for this IP address.
 610      * Best effort method, meaning we may not be able to return
 611      * the FQDN depending on the underlying system configuration.
 612      *
 613      * <p>If there is a security manager, this method first
 614      * calls its {@code checkConnect} method
 615      * with the hostname and {@code -1}
 616      * as its arguments to see if the calling code is allowed to know
 617      * the hostname for this IP address, i.e., to connect to the host.
 618      * If the operation is not allowed, it will return
 619      * the textual representation of the IP address.
 620      *
 621      * @return  the fully qualified domain name for this IP address,
 622      *    or if the operation is not allowed by the security check,
 623      *    the textual representation of the IP address.
 624      *
 625      * @see SecurityManager#checkConnect
 626      *
 627      * @since 1.4
 628      */
 629     public String getCanonicalHostName() {
 630         String value = canonicalHostName;
 631         if (value == null)
 632             canonicalHostName = value =
 633                 InetAddress.getHostFromNameService(this, true);
 634         return value;
 635     }
 636 
 637     /**
 638      * Returns the hostname for this address.
 639      *
 640      * <p>If there is a security manager, this method first
 641      * calls its {@code checkConnect} method
 642      * with the hostname and {@code -1}
 643      * as its arguments to see if the calling code is allowed to know
 644      * the hostname for this IP address, i.e., to connect to the host.
 645      * If the operation is not allowed, it will return
 646      * the textual representation of the IP address.
 647      *
 648      * @return  the host name for this IP address, or if the operation
 649      *    is not allowed by the security check, the textual
 650      *    representation of the IP address.
 651      *
 652      * @param check make security check if true
 653      *
 654      * @see SecurityManager#checkConnect
 655      */
 656     private static String getHostFromNameService(InetAddress addr, boolean check) {
 657         String host = null;
 658             try {
 659                 // first lookup the hostname
 660                 host = nameService.getHostByAddr(addr.getAddress());
 661 
 662                 /* check to see if calling code is allowed to know
 663                  * the hostname for this IP address, ie, connect to the host
 664                  */
 665                 if (check) {
 666                     SecurityManager sec = System.getSecurityManager();
 667                     if (sec != null) {
 668                         sec.checkConnect(host, -1);
 669                     }
 670                 }
 671 
 672                 /* now get all the IP addresses for this hostname,
 673                  * and make sure one of them matches the original IP
 674                  * address. We do this to try and prevent spoofing.
 675                  */
 676 
 677                 InetAddress[] arr = InetAddress.getAllByName0(host, check);
 678                 boolean ok = false;
 679 
 680                 if(arr != null) {
 681                     for(int i = 0; !ok && i < arr.length; i++) {
 682                         ok = addr.equals(arr[i]);
 683                     }
 684                 }
 685 
 686                 //XXX: if it looks a spoof just return the address?
 687                 if (!ok) {
 688                     host = addr.getHostAddress();
 689                     return host;
 690                 }
 691             } catch (SecurityException e) {
 692                 host = addr.getHostAddress();
 693             } catch (UnknownHostException e) {
 694                 host = addr.getHostAddress();
 695                 // let next provider resolve the hostname
 696             }
 697         return host;
 698     }
 699 
 700     /**
 701      * Returns the raw IP address of this {@code InetAddress}
 702      * object. The result is in network byte order: the highest order
 703      * byte of the address is in {@code getAddress()[0]}.
 704      *
 705      * @return  the raw IP address of this object.
 706      */
 707     public byte[] getAddress() {
 708         return null;
 709     }
 710 
 711     /**
 712      * Returns the IP address string in textual presentation.
 713      *
 714      * @return  the raw IP address in a string format.
 715      * @since   1.0.2
 716      */
 717     public String getHostAddress() {
 718         return null;
 719      }
 720 
 721     /**
 722      * Returns a hashcode for this IP address.
 723      *
 724      * @return  a hash code value for this IP address.
 725      */
 726     public int hashCode() {
 727         return -1;
 728     }
 729 
 730     /**
 731      * Compares this object against the specified object.
 732      * The result is {@code true} if and only if the argument is
 733      * not {@code null} and it represents the same IP address as
 734      * this object.
 735      * <p>
 736      * Two instances of {@code InetAddress} represent the same IP
 737      * address if the length of the byte arrays returned by
 738      * {@code getAddress} is the same for both, and each of the
 739      * array components is the same for the byte arrays.
 740      *
 741      * @param   obj   the object to compare against.
 742      * @return  {@code true} if the objects are the same;
 743      *          {@code false} otherwise.
 744      * @see     java.net.InetAddress#getAddress()
 745      */
 746     public boolean equals(Object obj) {
 747         return false;
 748     }
 749 
 750     /**
 751      * Converts this IP address to a {@code String}. The
 752      * string returned is of the form: hostname / literal IP
 753      * address.
 754      *
 755      * If the host name is unresolved, no reverse name service lookup
 756      * is performed. The hostname part will be represented by an empty string.
 757      *
 758      * @return  a string representation of this IP address.
 759      */
 760     public String toString() {
 761         String hostName = holder().getHostName();
 762         return Objects.toString(hostName, "")
 763             + "/" + getHostAddress();
 764     }
 765 
 766     // mapping from host name to Addresses - either NameServiceAddresses (while
 767     // still being looked-up by NameService(s)) or CachedAddresses when cached
 768     private static final ConcurrentMap<String, Addresses> cache =
 769         new ConcurrentHashMap<>();
 770 
 771     // CachedAddresses that have to expire are kept ordered in this NavigableSet
 772     // which is scanned on each access
 773     private static final NavigableSet<CachedAddresses> expirySet =
 774         new ConcurrentSkipListSet<>();
 775 
 776     // common interface
 777     private interface Addresses {
 778         InetAddress[] get() throws UnknownHostException;
 779     }
 780 
 781     // a holder for cached addresses with required metadata
 782     private static final class CachedAddresses  implements Addresses, Comparable<CachedAddresses> {
 783         private static final AtomicLong seq = new AtomicLong();
 784         final String host;
 785         final InetAddress[] inetAddresses;
 786         final long expiryTime; // time of expiry (in terms of System.nanoTime())
 787         final long id = seq.incrementAndGet(); // each instance is unique
 788 
 789         CachedAddresses(String host, InetAddress[] inetAddresses, long expiryTime) {
 790             this.host = host;
 791             this.inetAddresses = inetAddresses;
 792             this.expiryTime = expiryTime;
 793         }
 794 
 795         @Override
 796         public InetAddress[] get() throws UnknownHostException {
 797             if (inetAddresses == null) {
 798                 throw new UnknownHostException(host);
 799             }
 800             return inetAddresses;
 801         }
 802 
 803         @Override
 804         public int compareTo(CachedAddresses other) {
 805             // natural order is expiry time -
 806             // compare difference of expiry times rather than
 807             // expiry times directly, to avoid possible overflow.
 808             // (see System.nanoTime() recommendations...)
 809             long diff = this.expiryTime - other.expiryTime;
 810             if (diff < 0L) return -1;
 811             if (diff > 0L) return 1;
 812             // ties are broken using unique id
 813             return Long.compare(this.id, other.id);
 814         }
 815     }
 816 
 817     // a name service lookup based Addresses implementation which replaces itself
 818     // in cache when the result is obtained
 819     private static final class NameServiceAddresses implements Addresses {
 820         private final String host;
 821         private final InetAddress reqAddr;
 822 
 823         NameServiceAddresses(String host, InetAddress reqAddr) {
 824             this.host = host;
 825             this.reqAddr = reqAddr;
 826         }
 827 
 828         @Override
 829         public InetAddress[] get() throws UnknownHostException {
 830             Addresses addresses;
 831             // only one thread is doing lookup to name service
 832             // for particular host at any time.
 833             synchronized (this) {
 834                 // re-check that we are still us + re-install us if slot empty
 835                 addresses = cache.putIfAbsent(host, this);
 836                 if (addresses == null) {
 837                     // this can happen when we were replaced by CachedAddresses in
 838                     // some other thread, then CachedAddresses expired and were
 839                     // removed from cache while we were waiting for lock...
 840                     addresses = this;
 841                 }
 842                 // still us ?
 843                 if (addresses == this) {
 844                     // lookup name services
 845                     InetAddress[] inetAddresses;
 846                     UnknownHostException ex;
 847                     int cachePolicy;
 848                     try {
 849                         inetAddresses = getAddressesFromNameService(host, reqAddr);
 850                         ex = null;
 851                         cachePolicy = InetAddressCachePolicy.get();
 852                     } catch (UnknownHostException uhe) {
 853                         inetAddresses = null;
 854                         ex = uhe;
 855                         cachePolicy = InetAddressCachePolicy.getNegative();
 856                     }
 857                     // remove or replace us with cached addresses according to cachePolicy
 858                     if (cachePolicy == InetAddressCachePolicy.NEVER) {
 859                         cache.remove(host, this);
 860                     } else {
 861                         CachedAddresses cachedAddresses = new CachedAddresses(
 862                             host,
 863                             inetAddresses,
 864                             cachePolicy == InetAddressCachePolicy.FOREVER
 865                             ? 0L
 866                             // cachePolicy is in [s] - we need [ns]
 867                             : System.nanoTime() + 1000_000_000L * cachePolicy
 868                         );
 869                         if (cache.replace(host, this, cachedAddresses) &&
 870                             cachePolicy != InetAddressCachePolicy.FOREVER) {
 871                             // schedule expiry
 872                             expirySet.add(cachedAddresses);
 873                         }
 874                     }
 875                     if (inetAddresses == null) {
 876                         throw ex == null ? new UnknownHostException(host) : ex;
 877                     }
 878                     return inetAddresses;
 879                 }
 880                 // else addresses != this
 881             }
 882             // delegate to different addresses when we are already replaced
 883             // but outside of synchronized block to avoid any chance of dead-locking
 884             return addresses.get();
 885         }
 886     }
 887 
 888     /**
 889      * NameService provides host and address lookup service
 890      *
 891      * @since 9
 892      */
 893     private interface NameService {
 894 
 895         /**
 896          * Lookup a host mapping by name. Retrieve the IP addresses
 897          * associated with a host
 898          *
 899          * @param host the specified hostname
 900          * @return array of IP addresses for the requested host
 901          * @throws UnknownHostException
 902          *             if no IP address for the {@code host} could be found
 903          */
 904         InetAddress[] lookupAllHostAddr(String host)
 905                 throws UnknownHostException;
 906 
 907         /**
 908          * Lookup the host corresponding to the IP address provided
 909          *
 910          * @param addr byte array representing an IP address
 911          * @return {@code String} representing the host name mapping
 912          * @throws UnknownHostException
 913          *             if no host found for the specified IP address
 914          */
 915         String getHostByAddr(byte[] addr) throws UnknownHostException;
 916 
 917     }
 918 
 919     /**
 920      * The default NameService implementation, which delegates to the underlying
 921      * OS network libraries to resolve host address mappings.
 922      *
 923      * @since 9
 924      */
 925     private static final class PlatformNameService implements NameService {
 926 
 927         public InetAddress[] lookupAllHostAddr(String host)
 928             throws UnknownHostException
 929         {
 930             return impl.lookupAllHostAddr(host);
 931         }
 932 
 933         public String getHostByAddr(byte[] addr)
 934             throws UnknownHostException
 935         {
 936             return impl.getHostByAddr(addr);
 937         }
 938     }
 939 
 940     /**
 941      * The HostsFileNameService provides host address mapping
 942      * by reading the entries in a hosts file, which is specified by
 943      * {@code jdk.net.hosts.file} system property
 944      *
 945      * <p>The file format is that which corresponds with the /etc/hosts file
 946      * IP Address host alias list.
 947      *
 948      * <p>When the file lookup is enabled it replaces the default NameService
 949      * implementation
 950      *
 951      * @since 9
 952      */
 953     private static final class HostsFileNameService implements NameService {
 954 
 955         private final String hostsFile;
 956 
 957         public HostsFileNameService (String hostsFileName) {
 958             this.hostsFile = hostsFileName;
 959         }
 960 
 961         private  String addrToString(byte addr[]) {
 962           String stringifiedAddress = null;
 963 
 964             if (addr.length == Inet4Address.INADDRSZ) {
 965                 stringifiedAddress = Inet4Address.numericToTextFormat(addr);
 966             } else { // treat as an IPV6 jobby
 967                 byte[] newAddr
 968                     = IPAddressUtil.convertFromIPv4MappedAddress(addr);
 969                 if (newAddr != null) {
 970                    stringifiedAddress = Inet4Address.numericToTextFormat(addr);
 971                 } else {
 972                     stringifiedAddress = Inet6Address.numericToTextFormat(addr);
 973                 }
 974             }
 975             return stringifiedAddress;
 976         }
 977 
 978         /**
 979          * Lookup the host name  corresponding to the IP address provided.
 980          * Search the configured host file a host name corresponding to
 981          * the specified IP address.
 982          *
 983          * @param addr byte array representing an IP address
 984          * @return {@code String} representing the host name mapping
 985          * @throws UnknownHostException
 986          *             if no host found for the specified IP address
 987          */
 988         @Override
 989         public String getHostByAddr(byte[] addr) throws UnknownHostException {
 990             String hostEntry;
 991             String host = null;
 992 
 993             try (Scanner hostsFileScanner = new Scanner(new File(hostsFile), "UTF-8")) {
 994                 while (hostsFileScanner.hasNextLine()) {
 995                     hostEntry = hostsFileScanner.nextLine();
 996                     if (!hostEntry.startsWith("#")) {
 997                         hostEntry = removeComments(hostEntry);
 998                         String[] mapping = hostEntry.split("\\s+");
 999                         if (mapping.length >= 2 &&
1000                             Arrays.equals(addr, createAddressByteArray(mapping[0]))) {
1001                             host = mapping[1];
1002                             break;
1003                         }
1004                     }
1005                 }
1006             } catch (FileNotFoundException e) {
1007                 throw new UnknownHostException("Unable to resolve address "
1008                         + Arrays.toString(addr) + " as hosts file " + hostsFile
1009                         + " not found ");
1010             }
1011 
1012             if ((host == null) || (host.isEmpty()) || (host.equals(" "))) {
1013                 throw new UnknownHostException("Requested address "
1014                         + Arrays.toString(addr)
1015                         + " resolves to an invalid entry in hosts file "
1016                         + hostsFile);
1017             }
1018             return host;
1019         }
1020 
1021         /**
1022          * <p>Lookup a host mapping by name. Retrieve the IP addresses
1023          * associated with a host.
1024          *
1025          * <p>Search the configured hosts file for the addresses associated
1026          * with the specified host name.
1027          *
1028          * @param host the specified hostname
1029          * @return array of IP addresses for the requested host
1030          * @throws UnknownHostException
1031          *             if no IP address for the {@code host} could be found
1032          */
1033         public InetAddress[] lookupAllHostAddr(String host)
1034                 throws UnknownHostException {
1035             String hostEntry;
1036             String addrStr = null;
1037             InetAddress[] res = null;
1038             byte addr[] = new byte[4];
1039             ArrayList<InetAddress> inetAddresses = null;
1040 
1041             // lookup the file and create a list InetAddress for the specified host
1042             try (Scanner hostsFileScanner = new Scanner(new File(hostsFile), "UTF-8")) {
1043                 while (hostsFileScanner.hasNextLine()) {
1044                     hostEntry = hostsFileScanner.nextLine();
1045                     if (!hostEntry.startsWith("#")) {
1046                         hostEntry = removeComments(hostEntry);
1047                         if (hostEntry.contains(host)) {
1048                             addrStr = extractHostAddr(hostEntry, host);
1049                             if ((addrStr != null) && (!addrStr.isEmpty())) {
1050                                 addr = createAddressByteArray(addrStr);
1051                                 if (inetAddresses == null) {
1052                                     inetAddresses = new ArrayList<>(1);
1053                                 }
1054                                 if (addr != null) {
1055                                     inetAddresses.add(InetAddress.getByAddress(host, addr));
1056                                 }
1057                             }
1058                         }
1059                     }
1060                 }
1061             } catch (FileNotFoundException e) {
1062                 throw new UnknownHostException("Unable to resolve host " + host
1063                         + " as hosts file " + hostsFile + " not found ");
1064             }
1065 
1066             if (inetAddresses != null) {
1067                 res = inetAddresses.toArray(new InetAddress[inetAddresses.size()]);
1068             } else {
1069                 throw new UnknownHostException("Unable to resolve host " + host
1070                         + " in hosts file " + hostsFile);
1071             }
1072             return res;
1073         }
1074 
1075         private String removeComments(String hostsEntry) {
1076             String filteredEntry = hostsEntry;
1077             int hashIndex;
1078 
1079             if ((hashIndex = hostsEntry.indexOf("#")) != -1) {
1080                 filteredEntry = hostsEntry.substring(0, hashIndex);
1081             }
1082             return filteredEntry;
1083         }
1084 
1085         private byte [] createAddressByteArray(String addrStr) {
1086             byte[] addrArray;
1087             // check if IPV4 address - most likely
1088             addrArray = IPAddressUtil.textToNumericFormatV4(addrStr);
1089             if (addrArray == null) {
1090                 addrArray = IPAddressUtil.textToNumericFormatV6(addrStr);
1091             }
1092             return addrArray;
1093         }
1094 
1095         /** host to ip address mapping */
1096         private String extractHostAddr(String hostEntry, String host) {
1097             String[] mapping = hostEntry.split("\\s+");
1098             String hostAddr = null;
1099 
1100             if (mapping.length >= 2) {
1101                 // look at the host aliases
1102                 for (int i = 1; i < mapping.length; i++) {
1103                     if (mapping[i].equalsIgnoreCase(host)) {
1104                         hostAddr = mapping[0];
1105                     }
1106                 }
1107             }
1108             return hostAddr;
1109         }
1110     }
1111 
1112     static final InetAddressImpl  impl;
1113 
1114     static {
1115         // create the impl
1116         impl = InetAddressImplFactory.create();
1117 
1118         // create name service
1119         nameService = createNameService();
1120         }
1121 
1122     /**
1123      * Create an instance of the NameService interface based on
1124      * the setting of the {@code jdk.net.hosts.file} system property.
1125      *
1126      * <p>The default NameService is the PlatformNameService, which typically
1127      * delegates name and address resolution calls to the underlying
1128      * OS network libraries.
1129      *
1130      * <p> A HostsFileNameService is created if the {@code jdk.net.hosts.file}
1131      * system property is set. If the specified file doesn't exist, the name or
1132      * address lookup will result in an UnknownHostException. Thus, non existent
1133      * hosts file is handled as if the file is empty.
1134      *
1135      * @return a NameService
1136      */
1137     private static NameService createNameService() {
1138 
1139         String hostsFileName =
1140                 GetPropertyAction.privilegedGetProperty("jdk.net.hosts.file");
1141         NameService theNameService;
1142         if (hostsFileName != null) {
1143             theNameService = new HostsFileNameService(hostsFileName);
1144         } else {
1145             theNameService = new PlatformNameService();
1146         }
1147         return theNameService;
1148     }
1149 
1150     /**
1151      * Creates an InetAddress based on the provided host name and IP address.
1152      * No name service is checked for the validity of the address.
1153      *
1154      * <p> The host name can either be a machine name, such as
1155      * "{@code www.example.com}", or a textual representation of its IP
1156      * address.
1157      * <p> No validity checking is done on the host name either.
1158      *
1159      * <p> If addr specifies an IPv4 address an instance of Inet4Address
1160      * will be returned; otherwise, an instance of Inet6Address
1161      * will be returned.
1162      *
1163      * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
1164      * must be 16 bytes long
1165      *
1166      * @param host the specified host
1167      * @param addr the raw IP address in network byte order
1168      * @return  an InetAddress object created from the raw IP address.
1169      * @exception  UnknownHostException  if IP address is of illegal length
1170      * @since 1.4
1171      */
1172     public static InetAddress getByAddress(String host, byte[] addr)
1173         throws UnknownHostException {
1174         if (host != null && !host.isEmpty() && host.charAt(0) == '[') {
1175             if (host.charAt(host.length()-1) == ']') {
1176                 host = host.substring(1, host.length() -1);
1177             }
1178         }
1179         if (addr != null) {
1180             if (addr.length == Inet4Address.INADDRSZ) {
1181                 return new Inet4Address(host, addr);
1182             } else if (addr.length == Inet6Address.INADDRSZ) {
1183                 byte[] newAddr
1184                     = IPAddressUtil.convertFromIPv4MappedAddress(addr);
1185                 if (newAddr != null) {
1186                     return new Inet4Address(host, newAddr);
1187                 } else {
1188                     return new Inet6Address(host, addr);
1189                 }
1190             }
1191         }
1192         throw new UnknownHostException("addr is of illegal length");
1193     }
1194 
1195 
1196     /**
1197      * Determines the IP address of a host, given the host's name.
1198      *
1199      * <p> The host name can either be a machine name, such as
1200      * "{@code www.example.com}", or a textual representation of its
1201      * IP address. If a literal IP address is supplied, only the
1202      * validity of the address format is checked.
1203      *
1204      * <p> For {@code host} specified in literal IPv6 address,
1205      * either the form defined in RFC 2732 or the literal IPv6 address
1206      * format defined in RFC 2373 is accepted. IPv6 scoped addresses are also
1207      * supported. See <a href="Inet6Address.html#scoped">here</a> for a description of IPv6
1208      * scoped addresses.
1209      *
1210      * <p> If the host is {@code null} or {@code host.length()} is equal
1211      * to zero, then an {@code InetAddress} representing an address of the
1212      * loopback interface is returned.
1213      * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC&nbsp;3330</a>
1214      * section&nbsp;2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC&nbsp;2373</a>
1215      * section&nbsp;2.5.3.
1216      *
1217      * <p> If there is a security manager, and {@code host} is not {@code null}
1218      * or {@code host.length() } is not equal to zero, the security manager's
1219      * {@code checkConnect} method is called with the hostname and {@code -1}
1220      * as its arguments to determine if the operation is allowed.
1221      *
1222      * @param      host   the specified host, or {@code null}.
1223      * @return     an IP address for the given host name.
1224      * @exception  UnknownHostException  if no IP address for the
1225      *               {@code host} could be found, or if a scope_id was specified
1226      *               for a global IPv6 address.
1227      * @exception  SecurityException if a security manager exists
1228      *             and its checkConnect method doesn't allow the operation
1229      */
1230     public static InetAddress getByName(String host)
1231         throws UnknownHostException {
1232         return InetAddress.getAllByName(host)[0];
1233     }
1234 
1235     // called from deployment cache manager
1236     private static InetAddress getByName(String host, InetAddress reqAddr)
1237         throws UnknownHostException {
1238         return InetAddress.getAllByName(host, reqAddr)[0];
1239     }
1240 
1241     /**
1242      * Given the name of a host, returns an array of its IP addresses,
1243      * based on the configured name service on the system.
1244      *
1245      * <p> The host name can either be a machine name, such as
1246      * "{@code www.example.com}", or a textual representation of its IP
1247      * address. If a literal IP address is supplied, only the
1248      * validity of the address format is checked.
1249      *
1250      * <p> For {@code host} specified in <i>literal IPv6 address</i>,
1251      * either the form defined in RFC 2732 or the literal IPv6 address
1252      * format defined in RFC 2373 is accepted. A literal IPv6 address may
1253      * also be qualified by appending a scoped zone identifier or scope_id.
1254      * The syntax and usage of scope_ids is described
1255      * <a href="Inet6Address.html#scoped">here</a>.
1256      *
1257      * <p> If the host is {@code null} or {@code host.length()} is equal
1258      * to zero, then an {@code InetAddress} representing an address of the
1259      * loopback interface is returned.
1260      * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC&nbsp;3330</a>
1261      * section&nbsp;2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC&nbsp;2373</a>
1262      * section&nbsp;2.5.3. </p>
1263      *
1264      * <p> If there is a security manager, and {@code host} is not {@code null}
1265      * or {@code host.length() } is not equal to zero, the security manager's
1266      * {@code checkConnect} method is called with the hostname and {@code -1}
1267      * as its arguments to determine if the operation is allowed.
1268      *
1269      * @param      host   the name of the host, or {@code null}.
1270      * @return     an array of all the IP addresses for a given host name.
1271      *
1272      * @exception  UnknownHostException  if no IP address for the
1273      *               {@code host} could be found, or if a scope_id was specified
1274      *               for a global IPv6 address.
1275      * @exception  SecurityException  if a security manager exists and its
1276      *               {@code checkConnect} method doesn't allow the operation.
1277      *
1278      * @see SecurityManager#checkConnect
1279      */
1280     public static InetAddress[] getAllByName(String host)
1281         throws UnknownHostException {
1282         return getAllByName(host, null);
1283     }
1284 
1285     private static InetAddress[] getAllByName(String host, InetAddress reqAddr)
1286         throws UnknownHostException {
1287 
1288         if (host == null || host.isEmpty()) {
1289             InetAddress[] ret = new InetAddress[1];
1290             ret[0] = impl.loopbackAddress();
1291             return ret;
1292         }
1293 
1294         boolean ipv6Expected = false;
1295         if (host.charAt(0) == '[') {
1296             // This is supposed to be an IPv6 literal
1297             if (host.length() > 2 && host.charAt(host.length()-1) == ']') {
1298                 host = host.substring(1, host.length() -1);
1299                 ipv6Expected = true;
1300             } else {
1301                 // This was supposed to be a IPv6 address, but it's not!
1302                 throw new UnknownHostException(host + ": invalid IPv6 address");
1303             }
1304         }
1305 
1306         // if host is an IP address, we won't do further lookup
1307         if (Character.digit(host.charAt(0), 16) != -1
1308             || (host.charAt(0) == ':')) {
1309             byte[] addr = null;
1310             int numericZone = -1;
1311             String ifname = null;
1312             // see if it is IPv4 address
1313             addr = IPAddressUtil.textToNumericFormatV4(host);
1314             if (addr == null) {
1315                 // This is supposed to be an IPv6 literal
1316                 // Check if a numeric or string zone id is present
1317                 int pos;
1318                 if ((pos=host.indexOf ('%')) != -1) {
1319                     numericZone = checkNumericZone (host);
1320                     if (numericZone == -1) { /* remainder of string must be an ifname */
1321                         ifname = host.substring (pos+1);
1322                     }
1323                 }
1324                 if ((addr = IPAddressUtil.textToNumericFormatV6(host)) == null && host.contains(":")) {
1325                     throw new UnknownHostException(host + ": invalid IPv6 address");
1326                 }
1327             } else if (ipv6Expected) {
1328                 // Means an IPv4 literal between brackets!
1329                 throw new UnknownHostException("["+host+"]");
1330             }
1331             InetAddress[] ret = new InetAddress[1];
1332             if(addr != null) {
1333                 if (addr.length == Inet4Address.INADDRSZ) {
1334                     ret[0] = new Inet4Address(null, addr);
1335                 } else {
1336                     if (ifname != null) {
1337                         ret[0] = new Inet6Address(null, addr, ifname);
1338                     } else {
1339                         ret[0] = new Inet6Address(null, addr, numericZone);
1340                     }
1341                 }
1342                 return ret;
1343             }
1344         } else if (ipv6Expected) {
1345             // We were expecting an IPv6 Literal, but got something else
1346             throw new UnknownHostException("["+host+"]");
1347         }
1348         return getAllByName0(host, reqAddr, true, true);
1349     }
1350 
1351     /**
1352      * Returns the loopback address.
1353      * <p>
1354      * The InetAddress returned will represent the IPv4
1355      * loopback address, 127.0.0.1, or the IPv6 loopback
1356      * address, ::1. The IPv4 loopback address returned
1357      * is only one of many in the form 127.*.*.*
1358      *
1359      * @return  the InetAddress loopback instance.
1360      * @since 1.7
1361      */
1362     public static InetAddress getLoopbackAddress() {
1363         return impl.loopbackAddress();
1364     }
1365 
1366 
1367     /**
1368      * check if the literal address string has %nn appended
1369      * returns -1 if not, or the numeric value otherwise.
1370      *
1371      * %nn may also be a string that represents the displayName of
1372      * a currently available NetworkInterface.
1373      */
1374     private static int checkNumericZone (String s) throws UnknownHostException {
1375         int percent = s.indexOf ('%');
1376         int slen = s.length();
1377         int digit, zone=0;
1378         if (percent == -1) {
1379             return -1;
1380         }
1381         for (int i=percent+1; i<slen; i++) {
1382             char c = s.charAt(i);
1383             if (c == ']') {
1384                 if (i == percent+1) {
1385                     /* empty per-cent field */
1386                     return -1;
1387                 }
1388                 break;
1389             }
1390             if ((digit = Character.digit (c, 10)) < 0) {
1391                 return -1;
1392             }
1393             zone = (zone * 10) + digit;
1394         }
1395         return zone;
1396     }
1397 
1398     private static InetAddress[] getAllByName0 (String host)
1399         throws UnknownHostException
1400     {
1401         return getAllByName0(host, true);
1402     }
1403 
1404     /**
1405      * package private so SocketPermission can call it
1406      */
1407     static InetAddress[] getAllByName0 (String host, boolean check)
1408         throws UnknownHostException  {
1409         return getAllByName0 (host, null, check, true);
1410     }
1411 
1412     /**
1413      * Designated lookup method.
1414      *
1415      * @param host host name to look up
1416      * @param reqAddr requested address to be the 1st in returned array
1417      * @param check perform security check
1418      * @param useCache use cached value if not expired else always
1419      *                 perform name service lookup (and cache the result)
1420      * @return array of InetAddress(es)
1421      * @throws UnknownHostException if host name is not found
1422      */
1423     private static InetAddress[] getAllByName0(String host,
1424                                                InetAddress reqAddr,
1425                                                boolean check,
1426                                                boolean useCache)
1427         throws UnknownHostException  {
1428 
1429         /* If it gets here it is presumed to be a hostname */
1430 
1431         /* make sure the connection to the host is allowed, before we
1432          * give out a hostname
1433          */
1434         if (check) {
1435             SecurityManager security = System.getSecurityManager();
1436             if (security != null) {
1437                 security.checkConnect(host, -1);
1438             }
1439         }
1440 
1441         // remove expired addresses from cache - expirySet keeps them ordered
1442         // by expiry time so we only need to iterate the prefix of the NavigableSet...
1443         long now = System.nanoTime();
1444         for (CachedAddresses caddrs : expirySet) {
1445             // compare difference of time instants rather than
1446             // time instants directly, to avoid possible overflow.
1447             // (see System.nanoTime() recommendations...)
1448             if ((caddrs.expiryTime - now) < 0L) {
1449                 // ConcurrentSkipListSet uses weakly consistent iterator,
1450                 // so removing while iterating is OK...
1451                 if (expirySet.remove(caddrs)) {
1452                     // ... remove from cache
1453                     cache.remove(caddrs.host, caddrs);
1454                 }
1455             } else {
1456                 // we encountered 1st element that expires in future
1457                 break;
1458             }
1459         }
1460 
1461         // look-up or remove from cache
1462         Addresses addrs;
1463         if (useCache) {
1464             addrs = cache.get(host);
1465         } else {
1466             addrs = cache.remove(host);
1467             if (addrs != null) {
1468                 if (addrs instanceof CachedAddresses) {
1469                     // try removing from expirySet too if CachedAddresses
1470                     expirySet.remove(addrs);
1471                 }
1472                 addrs = null;
1473             }
1474         }
1475 
1476         if (addrs == null) {
1477             // create a NameServiceAddresses instance which will look up
1478             // the name service and install it within cache...
1479             Addresses oldAddrs = cache.putIfAbsent(
1480                 host,
1481                 addrs = new NameServiceAddresses(host, reqAddr)
1482             );
1483             if (oldAddrs != null) { // lost putIfAbsent race
1484                 addrs = oldAddrs;
1485             }
1486         }
1487 
1488         // ask Addresses to get an array of InetAddress(es) and clone it
1489         return addrs.get().clone();
1490     }
1491 
1492     static InetAddress[] getAddressesFromNameService(String host, InetAddress reqAddr)
1493         throws UnknownHostException
1494     {
1495         InetAddress[] addresses = null;
1496         UnknownHostException ex = null;
1497 
1498             try {
1499                 addresses = nameService.lookupAllHostAddr(host);
1500             } catch (UnknownHostException uhe) {
1501                 if (host.equalsIgnoreCase("localhost")) {
1502                     addresses = new InetAddress[] { impl.loopbackAddress() };
1503                 }
1504                 else {
1505                     ex = uhe;
1506                 }
1507             }
1508 
1509         if (addresses == null) {
1510             throw ex == null ? new UnknownHostException(host) : ex;
1511         }
1512 
1513         // More to do?
1514         if (reqAddr != null && addresses.length > 1 && !addresses[0].equals(reqAddr)) {
1515             // Find it?
1516             int i = 1;
1517             for (; i < addresses.length; i++) {
1518                 if (addresses[i].equals(reqAddr)) {
1519                     break;
1520                 }
1521             }
1522             // Rotate
1523             if (i < addresses.length) {
1524                 InetAddress tmp, tmp2 = reqAddr;
1525                 for (int j = 0; j < i; j++) {
1526                     tmp = addresses[j];
1527                     addresses[j] = tmp2;
1528                     tmp2 = tmp;
1529                 }
1530                 addresses[i] = tmp2;
1531             }
1532         }
1533 
1534         return addresses;
1535     }
1536 
1537     /**
1538      * Returns an {@code InetAddress} object given the raw IP address .
1539      * The argument is in network byte order: the highest order
1540      * byte of the address is in {@code getAddress()[0]}.
1541      *
1542      * <p> This method doesn't block, i.e. no reverse name service lookup
1543      * is performed.
1544      *
1545      * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
1546      * must be 16 bytes long
1547      *
1548      * @param addr the raw IP address in network byte order
1549      * @return  an InetAddress object created from the raw IP address.
1550      * @exception  UnknownHostException  if IP address is of illegal length
1551      * @since 1.4
1552      */
1553     public static InetAddress getByAddress(byte[] addr)
1554         throws UnknownHostException {
1555         return getByAddress(null, addr);
1556     }
1557 
1558     private static final class CachedLocalHost {
1559         final String host;
1560         final InetAddress addr;
1561         final long expiryTime = System.nanoTime() + 5000_000_000L; // now + 5s;
1562 
1563         CachedLocalHost(String host, InetAddress addr) {
1564             this.host = host;
1565             this.addr = addr;
1566         }
1567     }
1568 
1569     private static volatile CachedLocalHost cachedLocalHost;
1570 
1571     /**
1572      * Returns the address of the local host. This is achieved by retrieving
1573      * the name of the host from the system, then resolving that name into
1574      * an {@code InetAddress}.
1575      *
1576      * <P>Note: The resolved address may be cached for a short period of time.
1577      * </P>
1578      *
1579      * <p>If there is a security manager, its
1580      * {@code checkConnect} method is called
1581      * with the local host name and {@code -1}
1582      * as its arguments to see if the operation is allowed.
1583      * If the operation is not allowed, an InetAddress representing
1584      * the loopback address is returned.
1585      *
1586      * @return     the address of the local host.
1587      *
1588      * @exception  UnknownHostException  if the local host name could not
1589      *             be resolved into an address.
1590      *
1591      * @see SecurityManager#checkConnect
1592      * @see java.net.InetAddress#getByName(java.lang.String)
1593      */
1594     public static InetAddress getLocalHost() throws UnknownHostException {
1595 
1596         SecurityManager security = System.getSecurityManager();
1597         try {
1598             // is cached data still valid?
1599             CachedLocalHost clh = cachedLocalHost;
1600             if (clh != null && (clh.expiryTime - System.nanoTime()) >= 0L) {
1601                 if (security != null) {
1602                     security.checkConnect(clh.host, -1);
1603                 }
1604                 return clh.addr;
1605             }
1606 
1607             String local = impl.getLocalHostName();
1608 
1609             if (security != null) {
1610                 security.checkConnect(local, -1);
1611             }
1612 
1613             InetAddress localAddr;
1614             if (local.equals("localhost")) {
1615                 // shortcut for "localhost" host name
1616                 localAddr = impl.loopbackAddress();
1617             } else {
1618                 // call getAllByName0 without security checks and
1619                 // without using cached data
1620                 try {
1621                     localAddr = getAllByName0(local, null, false, false)[0];
1622                 } catch (UnknownHostException uhe) {
1623                     // Rethrow with a more informative error message.
1624                     UnknownHostException uhe2 =
1625                         new UnknownHostException(local + ": " +
1626                                                  uhe.getMessage());
1627                     uhe2.initCause(uhe);
1628                     throw uhe2;
1629                 }
1630             }
1631             cachedLocalHost = new CachedLocalHost(local, localAddr);
1632             return localAddr;
1633         } catch (java.lang.SecurityException e) {
1634             return impl.loopbackAddress();
1635         }
1636     }
1637 
1638     /**
1639      * Perform class load-time initializations.
1640      */
1641     private static native void init();
1642 
1643 
1644     /*
1645      * Returns the InetAddress representing anyLocalAddress
1646      * (typically 0.0.0.0 or ::0)
1647      */
1648     static InetAddress anyLocalAddress() {
1649         return impl.anyLocalAddress();
1650     }
1651 
1652     /*
1653      * Load and instantiate an underlying impl class
1654      */
1655     static InetAddressImpl loadImpl(String implName) {
1656         Object impl = null;
1657 
1658         /*
1659          * Property "impl.prefix" will be prepended to the classname
1660          * of the implementation object we instantiate, to which we
1661          * delegate the real work (like native methods).  This
1662          * property can vary across implementations of the java.
1663          * classes.  The default is an empty String "".
1664          */
1665         String prefix = GetPropertyAction.privilegedGetProperty("impl.prefix", "");
1666         try {
1667             @SuppressWarnings("deprecation")
1668             Object tmp = Class.forName("java.net." + prefix + implName).newInstance();
1669             impl = tmp;
1670         } catch (ClassNotFoundException e) {
1671             System.err.println("Class not found: java.net." + prefix +
1672                                implName + ":\ncheck impl.prefix property " +
1673                                "in your properties file.");
1674         } catch (InstantiationException e) {
1675             System.err.println("Could not instantiate: java.net." + prefix +
1676                                implName + ":\ncheck impl.prefix property " +
1677                                "in your properties file.");
1678         } catch (IllegalAccessException e) {
1679             System.err.println("Cannot access class: java.net." + prefix +
1680                                implName + ":\ncheck impl.prefix property " +
1681                                "in your properties file.");
1682         }
1683 
1684         if (impl == null) {
1685             try {
1686                 @SuppressWarnings("deprecation")
1687                 Object tmp = Class.forName(implName).newInstance();
1688                 impl = tmp;
1689             } catch (Exception e) {
1690                 throw new Error("System property impl.prefix incorrect");
1691             }
1692         }
1693 
1694         return (InetAddressImpl) impl;
1695     }
1696 
1697     private void readObjectNoData () {
1698         if (getClass().getClassLoader() != null) {
1699             throw new SecurityException ("invalid address type");
1700         }
1701     }
1702 
1703     private static final jdk.internal.misc.Unsafe UNSAFE
1704             = jdk.internal.misc.Unsafe.getUnsafe();
1705     private static final long FIELDS_OFFSET
1706             = UNSAFE.objectFieldOffset(InetAddress.class, "holder");
1707 
1708     private void readObject (ObjectInputStream s) throws
1709                          IOException, ClassNotFoundException {
1710         if (getClass().getClassLoader() != null) {
1711             throw new SecurityException ("invalid address type");
1712         }
1713         GetField gf = s.readFields();
1714         String host = (String)gf.get("hostName", null);
1715         int address = gf.get("address", 0);
1716         int family = gf.get("family", 0);
1717         if (family != IPv4 && family != IPv6) {
1718             throw new InvalidObjectException("invalid address family type: " + family);
1719         }
1720         InetAddressHolder h = new InetAddressHolder(host, address, family);
1721         UNSAFE.putReference(this, FIELDS_OFFSET, h);
1722     }
1723 
1724     /* needed because the serializable fields no longer exist */
1725 
1726     /**
1727      * @serialField hostName String
1728      * @serialField address int
1729      * @serialField family int
1730      */
1731     private static final ObjectStreamField[] serialPersistentFields = {
1732         new ObjectStreamField("hostName", String.class),
1733         new ObjectStreamField("address", int.class),
1734         new ObjectStreamField("family", int.class),
1735     };
1736 
1737     private void writeObject (ObjectOutputStream s) throws
1738                         IOException {
1739         if (getClass().getClassLoader() != null) {
1740             throw new SecurityException ("invalid address type");
1741         }
1742         PutField pf = s.putFields();
1743         pf.put("hostName", holder().getHostName());
1744         pf.put("address", holder().getAddress());
1745         pf.put("family", holder().getFamily());
1746         s.writeFields();
1747     }
1748 }
1749 
1750 /*
1751  * Simple factory to create the impl
1752  */
1753 class InetAddressImplFactory {
1754 
1755     static InetAddressImpl create() {
1756         return InetAddress.loadImpl(isIPv6Supported() ?
1757                                     "Inet6AddressImpl" : "Inet4AddressImpl");
1758     }
1759 
1760     static native boolean isIPv6Supported();
1761 }