rev 51958 : 8211122: Reduce the number of internal classes made accessible to jdk.unsupported
Reviewed-by: alanb, dfuchs, kvn

   1 /*
   2  * Copyright (c) 1995, 2018, 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 
  49 import jdk.internal.access.JavaNetInetAddressAccess;
  50 import jdk.internal.access.SharedSecrets;
  51 import sun.security.action.*;
  52 import sun.net.InetAddressCachePolicy;
  53 import sun.net.util.IPAddressUtil;
  54 
  55 /**
  56  * This class represents an Internet Protocol (IP) address.
  57  *
  58  * <p> An IP address is either a 32-bit or 128-bit unsigned number
  59  * used by IP, a lower-level protocol on which protocols like UDP and
  60  * TCP are built. The IP address architecture is defined by <a
  61  * href="http://www.ietf.org/rfc/rfc790.txt"><i>RFC&nbsp;790:
  62  * Assigned Numbers</i></a>, <a
  63  * href="http://www.ietf.org/rfc/rfc1918.txt"> <i>RFC&nbsp;1918:
  64  * Address Allocation for Private Internets</i></a>, <a
  65  * href="http://www.ietf.org/rfc/rfc2365.txt"><i>RFC&nbsp;2365:
  66  * Administratively Scoped IP Multicast</i></a>, and <a
  67  * href="http://www.ietf.org/rfc/rfc2373.txt"><i>RFC&nbsp;2373: IP
  68  * Version 6 Addressing Architecture</i></a>. An instance of an
  69  * InetAddress consists of an IP address and possibly its
  70  * corresponding host name (depending on whether it is constructed
  71  * with a host name or whether it has already done reverse host name
  72  * resolution).
  73  *
  74  * <h3> Address types </h3>
  75  *
  76  * <table class="striped" style="margin-left:2em">
  77  *   <caption style="display:none">Description of unicast and multicast address types</caption>
  78  *   <thead>
  79  *   <tr><th scope="col">Address Type</th><th scope="col">Description</th></tr>
  80  *   </thead>
  81  *   <tbody>
  82  *   <tr><th scope="row" style="vertical-align:top">unicast</th>
  83  *       <td>An identifier for a single interface. A packet sent to
  84  *         a unicast address is delivered to the interface identified by
  85  *         that address.
  86  *
  87  *         <p> The Unspecified Address -- Also called anylocal or wildcard
  88  *         address. It must never be assigned to any node. It indicates the
  89  *         absence of an address. One example of its use is as the target of
  90  *         bind, which allows a server to accept a client connection on any
  91  *         interface, in case the server host has multiple interfaces.
  92  *
  93  *         <p> The <i>unspecified</i> address must not be used as
  94  *         the destination address of an IP packet.
  95  *
  96  *         <p> The <i>Loopback</i> Addresses -- This is the address
  97  *         assigned to the loopback interface. Anything sent to this
  98  *         IP address loops around and becomes IP input on the local
  99  *         host. This address is often used when testing a
 100  *         client.</td></tr>
 101  *   <tr><th scope="row" style="vertical-align:top">multicast</th>
 102  *       <td>An identifier for a set of interfaces (typically belonging
 103  *         to different nodes). A packet sent to a multicast address is
 104  *         delivered to all interfaces identified by that address.</td></tr>
 105  * </tbody>
 106  * </table>
 107  *
 108  * <h4> IP address scope </h4>
 109  *
 110  * <p> <i>Link-local</i> addresses are designed to be used for addressing
 111  * on a single link for purposes such as auto-address configuration,
 112  * neighbor discovery, or when no routers are present.
 113  *
 114  * <p> <i>Site-local</i> addresses are designed to be used for addressing
 115  * inside of a site without the need for a global prefix.
 116  *
 117  * <p> <i>Global</i> addresses are unique across the internet.
 118  *
 119  * <h4> Textual representation of IP addresses </h4>
 120  *
 121  * The textual representation of an IP address is address family specific.
 122  *
 123  * <p>
 124  *
 125  * For IPv4 address format, please refer to <A
 126  * HREF="Inet4Address.html#format">Inet4Address#format</A>; For IPv6
 127  * address format, please refer to <A
 128  * HREF="Inet6Address.html#format">Inet6Address#format</A>.
 129  *
 130  * <P>There is a <a href="doc-files/net-properties.html#Ipv4IPv6">couple of
 131  * System Properties</a> affecting how IPv4 and IPv6 addresses are used.</P>
 132  *
 133  * <h4> Host Name Resolution </h4>
 134  *
 135  * Host name-to-IP address <i>resolution</i> is accomplished through
 136  * the use of a combination of local machine configuration information
 137  * and network naming services such as the Domain Name System (DNS)
 138  * and Network Information Service(NIS). The particular naming
 139  * services(s) being used is by default the local machine configured
 140  * one. For any host name, its corresponding IP address is returned.
 141  *
 142  * <p> <i>Reverse name resolution</i> means that for any IP address,
 143  * the host associated with the IP address is returned.
 144  *
 145  * <p> The InetAddress class provides methods to resolve host names to
 146  * their IP addresses and vice versa.
 147  *
 148  * <h4> InetAddress Caching </h4>
 149  *
 150  * The InetAddress class has a cache to store successful as well as
 151  * unsuccessful host name resolutions.
 152  *
 153  * <p> By default, when a security manager is installed, in order to
 154  * protect against DNS spoofing attacks,
 155  * the result of positive host name resolutions are
 156  * cached forever. When a security manager is not installed, the default
 157  * behavior is to cache entries for a finite (implementation dependent)
 158  * period of time. The result of unsuccessful host
 159  * name resolution is cached for a very short period of time (10
 160  * seconds) to improve performance.
 161  *
 162  * <p> If the default behavior is not desired, then a Java security property
 163  * can be set to a different Time-to-live (TTL) value for positive
 164  * caching. Likewise, a system admin can configure a different
 165  * negative caching TTL value when needed.
 166  *
 167  * <p> Two Java security properties control the TTL values used for
 168  *  positive and negative host name resolution caching:
 169  *
 170  * <dl style="margin-left:2em">
 171  * <dt><b>networkaddress.cache.ttl</b></dt>
 172  * <dd>Indicates the caching policy for successful name lookups from
 173  * the name service. The value is specified as an integer to indicate
 174  * the number of seconds to cache the successful lookup. The default
 175  * setting is to cache for an implementation specific period of time.
 176  * <p>
 177  * A value of -1 indicates "cache forever".
 178  * </dd>
 179  * <dt><b>networkaddress.cache.negative.ttl</b> (default: 10)</dt>
 180  * <dd>Indicates the caching policy for un-successful name lookups
 181  * from the name service. The value is specified as an integer to
 182  * indicate the number of seconds to cache the failure for
 183  * un-successful lookups.
 184  * <p>
 185  * A value of 0 indicates "never cache".
 186  * A value of -1 indicates "cache forever".
 187  * </dd>
 188  * </dl>
 189  *
 190  * @author  Chris Warth
 191  * @see     java.net.InetAddress#getByAddress(byte[])
 192  * @see     java.net.InetAddress#getByAddress(java.lang.String, byte[])
 193  * @see     java.net.InetAddress#getAllByName(java.lang.String)
 194  * @see     java.net.InetAddress#getByName(java.lang.String)
 195  * @see     java.net.InetAddress#getLocalHost()
 196  * @since 1.0
 197  */
 198 public
 199 class InetAddress implements java.io.Serializable {
 200 
 201     @Native static final int PREFER_IPV4_VALUE = 0;
 202     @Native static final int PREFER_IPV6_VALUE = 1;
 203     @Native static final int PREFER_SYSTEM_VALUE = 2;
 204 
 205     /**
 206      * Specify the address family: Internet Protocol, Version 4
 207      * @since 1.4
 208      */
 209     @Native static final int IPv4 = 1;
 210 
 211     /**
 212      * Specify the address family: Internet Protocol, Version 6
 213      * @since 1.4
 214      */
 215     @Native static final int IPv6 = 2;
 216 
 217     /* Specify address family preference */
 218     static transient final int preferIPv6Address;
 219 
 220     static class InetAddressHolder {
 221         /**
 222          * Reserve the original application specified hostname.
 223          *
 224          * The original hostname is useful for domain-based endpoint
 225          * identification (see RFC 2818 and RFC 6125).  If an address
 226          * was created with a raw IP address, a reverse name lookup
 227          * may introduce endpoint identification security issue via
 228          * DNS forging.
 229          *
 230          * Oracle JSSE provider is using this original hostname, via
 231          * jdk.internal.misc.JavaNetAccess, for SSL/TLS endpoint identification.
 232          *
 233          * Note: May define a new public method in the future if necessary.
 234          */
 235         String originalHostName;
 236 
 237         InetAddressHolder() {}
 238 
 239         InetAddressHolder(String hostName, int address, int family) {
 240             this.originalHostName = hostName;
 241             this.hostName = hostName;
 242             this.address = address;
 243             this.family = family;
 244         }
 245 
 246         void init(String hostName, int family) {
 247             this.originalHostName = hostName;
 248             this.hostName = hostName;
 249             if (family != -1) {
 250                 this.family = family;
 251             }
 252         }
 253 
 254         String hostName;
 255 
 256         String getHostName() {
 257             return hostName;
 258         }
 259 
 260         String getOriginalHostName() {
 261             return originalHostName;
 262         }
 263 
 264         /**
 265          * Holds a 32-bit IPv4 address.
 266          */
 267         int address;
 268 
 269         int getAddress() {
 270             return address;
 271         }
 272 
 273         /**
 274          * Specifies the address family type, for instance, '1' for IPv4
 275          * addresses, and '2' for IPv6 addresses.
 276          */
 277         int family;
 278 
 279         int getFamily() {
 280             return family;
 281         }
 282     }
 283 
 284     /* Used to store the serializable fields of InetAddress */
 285     final transient InetAddressHolder holder;
 286 
 287     InetAddressHolder holder() {
 288         return holder;
 289     }
 290 
 291     /* Used to store the name service provider */
 292     private static transient NameService nameService = null;
 293 
 294     /**
 295      * Used to store the best available hostname.
 296      * Lazily initialized via a data race; safe because Strings are immutable.
 297      */
 298     private transient String canonicalHostName = null;
 299 
 300     /** use serialVersionUID from JDK 1.0.2 for interoperability */
 301     private static final long serialVersionUID = 3286316764910316507L;
 302 
 303     /*
 304      * Load net library into runtime, and perform initializations.
 305      */
 306     static {
 307         String str = java.security.AccessController.doPrivileged(
 308                 new GetPropertyAction("java.net.preferIPv6Addresses"));
 309         if (str == null) {
 310             preferIPv6Address = PREFER_IPV4_VALUE;
 311         } else if (str.equalsIgnoreCase("true")) {
 312             preferIPv6Address = PREFER_IPV6_VALUE;
 313         } else if (str.equalsIgnoreCase("false")) {
 314             preferIPv6Address = PREFER_IPV4_VALUE;
 315         } else if (str.equalsIgnoreCase("system")) {
 316             preferIPv6Address = PREFER_SYSTEM_VALUE;
 317         } else {
 318             preferIPv6Address = PREFER_IPV4_VALUE;
 319         }
 320         AccessController.doPrivileged(
 321             new java.security.PrivilegedAction<>() {
 322                 public Void run() {
 323                     System.loadLibrary("net");
 324                     return null;
 325                 }
 326             });
 327         SharedSecrets.setJavaNetInetAddressAccess(
 328                 new JavaNetInetAddressAccess() {
 329                     public String getOriginalHostName(InetAddress ia) {
 330                         return ia.holder.getOriginalHostName();
 331                     }
 332 
 333                     public InetAddress getByName(String hostName,
 334                                                  InetAddress hostAddress)
 335                             throws UnknownHostException
 336                     {
 337                         return InetAddress.getByName(hostName, hostAddress);
 338                     }
 339                 }
 340         );
 341         init();
 342     }
 343 
 344     /**
 345      * Constructor for the Socket.accept() method.
 346      * This creates an empty InetAddress, which is filled in by
 347      * the accept() method.  This InetAddress, however, is not
 348      * put in the address cache, since it is not created by name.
 349      */
 350     InetAddress() {
 351         holder = new InetAddressHolder();
 352     }
 353 
 354     /**
 355      * Replaces the de-serialized object with an Inet4Address object.
 356      *
 357      * @return the alternate object to the de-serialized object.
 358      *
 359      * @throws ObjectStreamException if a new object replacing this
 360      * object could not be created
 361      */
 362     private Object readResolve() throws ObjectStreamException {
 363         // will replace the deserialized 'this' object
 364         return new Inet4Address(holder().getHostName(), holder().getAddress());
 365     }
 366 
 367     /**
 368      * Utility routine to check if the InetAddress is an
 369      * IP multicast address.
 370      * @return a {@code boolean} indicating if the InetAddress is
 371      * an IP multicast address
 372      * @since   1.1
 373      */
 374     public boolean isMulticastAddress() {
 375         return false;
 376     }
 377 
 378     /**
 379      * Utility routine to check if the InetAddress is a wildcard address.
 380      * @return a {@code boolean} indicating if the Inetaddress is
 381      *         a wildcard address.
 382      * @since 1.4
 383      */
 384     public boolean isAnyLocalAddress() {
 385         return false;
 386     }
 387 
 388     /**
 389      * Utility routine to check if the InetAddress is a loopback address.
 390      *
 391      * @return a {@code boolean} indicating if the InetAddress is
 392      * a loopback address; or false otherwise.
 393      * @since 1.4
 394      */
 395     public boolean isLoopbackAddress() {
 396         return false;
 397     }
 398 
 399     /**
 400      * Utility routine to check if the InetAddress is an link local address.
 401      *
 402      * @return a {@code boolean} indicating if the InetAddress is
 403      * a link local address; or false if address is not a link local unicast address.
 404      * @since 1.4
 405      */
 406     public boolean isLinkLocalAddress() {
 407         return false;
 408     }
 409 
 410     /**
 411      * Utility routine to check if the InetAddress is a site local address.
 412      *
 413      * @return a {@code boolean} indicating if the InetAddress is
 414      * a site local address; or false if address is not a site local unicast address.
 415      * @since 1.4
 416      */
 417     public boolean isSiteLocalAddress() {
 418         return false;
 419     }
 420 
 421     /**
 422      * Utility routine to check if the multicast address has global scope.
 423      *
 424      * @return a {@code boolean} indicating if the address has
 425      *         is a multicast address of global scope, false if it is not
 426      *         of global scope or it is not a multicast address
 427      * @since 1.4
 428      */
 429     public boolean isMCGlobal() {
 430         return false;
 431     }
 432 
 433     /**
 434      * Utility routine to check if the multicast address has node scope.
 435      *
 436      * @return a {@code boolean} indicating if the address has
 437      *         is a multicast address of node-local scope, false if it is not
 438      *         of node-local scope or it is not a multicast address
 439      * @since 1.4
 440      */
 441     public boolean isMCNodeLocal() {
 442         return false;
 443     }
 444 
 445     /**
 446      * Utility routine to check if the multicast address has link scope.
 447      *
 448      * @return a {@code boolean} indicating if the address has
 449      *         is a multicast address of link-local scope, false if it is not
 450      *         of link-local scope or it is not a multicast address
 451      * @since 1.4
 452      */
 453     public boolean isMCLinkLocal() {
 454         return false;
 455     }
 456 
 457     /**
 458      * Utility routine to check if the multicast address has site scope.
 459      *
 460      * @return a {@code boolean} indicating if the address has
 461      *         is a multicast address of site-local scope, false if it is not
 462      *         of site-local scope or it is not a multicast address
 463      * @since 1.4
 464      */
 465     public boolean isMCSiteLocal() {
 466         return false;
 467     }
 468 
 469     /**
 470      * Utility routine to check if the multicast address has organization scope.
 471      *
 472      * @return a {@code boolean} indicating if the address has
 473      *         is a multicast address of organization-local scope,
 474      *         false if it is not of organization-local scope
 475      *         or it is not a multicast address
 476      * @since 1.4
 477      */
 478     public boolean isMCOrgLocal() {
 479         return false;
 480     }
 481 
 482 
 483     /**
 484      * Test whether that address is reachable. Best effort is made by the
 485      * implementation to try to reach the host, but firewalls and server
 486      * configuration may block requests resulting in a unreachable status
 487      * while some specific ports may be accessible.
 488      * A typical implementation will use ICMP ECHO REQUESTs if the
 489      * privilege can be obtained, otherwise it will try to establish
 490      * a TCP connection on port 7 (Echo) of the destination host.
 491      * <p>
 492      * The timeout value, in milliseconds, indicates the maximum amount of time
 493      * the try should take. If the operation times out before getting an
 494      * answer, the host is deemed unreachable. A negative value will result
 495      * in an IllegalArgumentException being thrown.
 496      *
 497      * @param   timeout the time, in milliseconds, before the call aborts
 498      * @return a {@code boolean} indicating if the address is reachable.
 499      * @throws IOException if a network error occurs
 500      * @throws  IllegalArgumentException if {@code timeout} is negative.
 501      * @since 1.5
 502      */
 503     public boolean isReachable(int timeout) throws IOException {
 504         return isReachable(null, 0 , timeout);
 505     }
 506 
 507     /**
 508      * Test whether that address is reachable. Best effort is made by the
 509      * implementation to try to reach the host, but firewalls and server
 510      * configuration may block requests resulting in a unreachable status
 511      * while some specific ports may be accessible.
 512      * A typical implementation will use ICMP ECHO REQUESTs if the
 513      * privilege can be obtained, otherwise it will try to establish
 514      * a TCP connection on port 7 (Echo) of the destination host.
 515      * <p>
 516      * The {@code network interface} and {@code ttl} parameters
 517      * let the caller specify which network interface the test will go through
 518      * and the maximum number of hops the packets should go through.
 519      * A negative value for the {@code ttl} will result in an
 520      * IllegalArgumentException being thrown.
 521      * <p>
 522      * The timeout value, in milliseconds, indicates the maximum amount of time
 523      * the try should take. If the operation times out before getting an
 524      * answer, the host is deemed unreachable. A negative value will result
 525      * in an IllegalArgumentException being thrown.
 526      *
 527      * @param   netif   the NetworkInterface through which the
 528      *                    test will be done, or null for any interface
 529      * @param   ttl     the maximum numbers of hops to try or 0 for the
 530      *                  default
 531      * @param   timeout the time, in milliseconds, before the call aborts
 532      * @throws  IllegalArgumentException if either {@code timeout}
 533      *                          or {@code ttl} are negative.
 534      * @return a {@code boolean}indicating if the address is reachable.
 535      * @throws IOException if a network error occurs
 536      * @since 1.5
 537      */
 538     public boolean isReachable(NetworkInterface netif, int ttl,
 539                                int timeout) throws IOException {
 540         if (ttl < 0)
 541             throw new IllegalArgumentException("ttl can't be negative");
 542         if (timeout < 0)
 543             throw new IllegalArgumentException("timeout can't be negative");
 544 
 545         return impl.isReachable(this, timeout, netif, ttl);
 546     }
 547 
 548     /**
 549      * Gets the host name for this IP address.
 550      *
 551      * <p>If this InetAddress was created with a host name,
 552      * this host name will be remembered and returned;
 553      * otherwise, a reverse name lookup will be performed
 554      * and the result will be returned based on the system
 555      * configured name lookup service. If a lookup of the name service
 556      * is required, call
 557      * {@link #getCanonicalHostName() getCanonicalHostName}.
 558      *
 559      * <p>If there is a security manager, its
 560      * {@code checkConnect} method is first called
 561      * with the hostname and {@code -1}
 562      * as its arguments to see if the operation is allowed.
 563      * If the operation is not allowed, it will return
 564      * the textual representation of the IP address.
 565      *
 566      * @return  the host name for this IP address, or if the operation
 567      *    is not allowed by the security check, the textual
 568      *    representation of the IP address.
 569      *
 570      * @see InetAddress#getCanonicalHostName
 571      * @see SecurityManager#checkConnect
 572      */
 573     public String getHostName() {
 574         return getHostName(true);
 575     }
 576 
 577     /**
 578      * Returns the hostname for this address.
 579      * If the host is equal to null, then this address refers to any
 580      * of the local machine's available network addresses.
 581      * this is package private so SocketPermission can make calls into
 582      * here without a security check.
 583      *
 584      * <p>If there is a security manager, this method first
 585      * calls its {@code checkConnect} method
 586      * with the hostname and {@code -1}
 587      * as its arguments to see if the calling code is allowed to know
 588      * the hostname for this IP address, i.e., to connect to the host.
 589      * If the operation is not allowed, it will return
 590      * the textual representation of the IP address.
 591      *
 592      * @return  the host name for this IP address, or if the operation
 593      *    is not allowed by the security check, the textual
 594      *    representation of the IP address.
 595      *
 596      * @param check make security check if true
 597      *
 598      * @see SecurityManager#checkConnect
 599      */
 600     String getHostName(boolean check) {
 601         if (holder().getHostName() == null) {
 602             holder().hostName = InetAddress.getHostFromNameService(this, check);
 603         }
 604         return holder().getHostName();
 605     }
 606 
 607     /**
 608      * Gets the fully qualified domain name for this IP address.
 609      * Best effort method, meaning we may not be able to return
 610      * the FQDN depending on the underlying system configuration.
 611      *
 612      * <p>If there is a security manager, this method first
 613      * calls its {@code checkConnect} method
 614      * with the hostname and {@code -1}
 615      * as its arguments to see if the calling code is allowed to know
 616      * the hostname for this IP address, i.e., to connect to the host.
 617      * If the operation is not allowed, it will return
 618      * the textual representation of the IP address.
 619      *
 620      * @return  the fully qualified domain name for this IP address,
 621      *    or if the operation is not allowed by the security check,
 622      *    the textual representation of the IP address.
 623      *
 624      * @see SecurityManager#checkConnect
 625      *
 626      * @since 1.4
 627      */
 628     public String getCanonicalHostName() {
 629         String value = canonicalHostName;
 630         if (value == null)
 631             canonicalHostName = value =
 632                 InetAddress.getHostFromNameService(this, true);
 633         return value;
 634     }
 635 
 636     /**
 637      * Returns the hostname for this address.
 638      *
 639      * <p>If there is a security manager, this method first
 640      * calls its {@code checkConnect} method
 641      * with the hostname and {@code -1}
 642      * as its arguments to see if the calling code is allowed to know
 643      * the hostname for this IP address, i.e., to connect to the host.
 644      * If the operation is not allowed, it will return
 645      * the textual representation of the IP address.
 646      *
 647      * @return  the host name for this IP address, or if the operation
 648      *    is not allowed by the security check, the textual
 649      *    representation of the IP address.
 650      *
 651      * @param check make security check if true
 652      *
 653      * @see SecurityManager#checkConnect
 654      */
 655     private static String getHostFromNameService(InetAddress addr, boolean check) {
 656         String host = null;
 657             try {
 658                 // first lookup the hostname
 659                 host = nameService.getHostByAddr(addr.getAddress());
 660 
 661                 /* check to see if calling code is allowed to know
 662                  * the hostname for this IP address, ie, connect to the host
 663                  */
 664                 if (check) {
 665                     SecurityManager sec = System.getSecurityManager();
 666                     if (sec != null) {
 667                         sec.checkConnect(host, -1);
 668                     }
 669                 }
 670 
 671                 /* now get all the IP addresses for this hostname,
 672                  * and make sure one of them matches the original IP
 673                  * address. We do this to try and prevent spoofing.
 674                  */
 675 
 676                 InetAddress[] arr = InetAddress.getAllByName0(host, check);
 677                 boolean ok = false;
 678 
 679                 if(arr != null) {
 680                     for(int i = 0; !ok && i < arr.length; i++) {
 681                         ok = addr.equals(arr[i]);
 682                     }
 683                 }
 684 
 685                 //XXX: if it looks a spoof just return the address?
 686                 if (!ok) {
 687                     host = addr.getHostAddress();
 688                     return host;
 689                 }
 690             } catch (SecurityException e) {
 691                 host = addr.getHostAddress();
 692             } catch (UnknownHostException e) {
 693                 host = addr.getHostAddress();
 694                 // let next provider resolve the hostname
 695             }
 696         return host;
 697     }
 698 
 699     /**
 700      * Returns the raw IP address of this {@code InetAddress}
 701      * object. The result is in network byte order: the highest order
 702      * byte of the address is in {@code getAddress()[0]}.
 703      *
 704      * @return  the raw IP address of this object.
 705      */
 706     public byte[] getAddress() {
 707         return null;
 708     }
 709 
 710     /**
 711      * Returns the IP address string in textual presentation.
 712      *
 713      * @return  the raw IP address in a string format.
 714      * @since   1.0.2
 715      */
 716     public String getHostAddress() {
 717         return null;
 718      }
 719 
 720     /**
 721      * Returns a hashcode for this IP address.
 722      *
 723      * @return  a hash code value for this IP address.
 724      */
 725     public int hashCode() {
 726         return -1;
 727     }
 728 
 729     /**
 730      * Compares this object against the specified object.
 731      * The result is {@code true} if and only if the argument is
 732      * not {@code null} and it represents the same IP address as
 733      * this object.
 734      * <p>
 735      * Two instances of {@code InetAddress} represent the same IP
 736      * address if the length of the byte arrays returned by
 737      * {@code getAddress} is the same for both, and each of the
 738      * array components is the same for the byte arrays.
 739      *
 740      * @param   obj   the object to compare against.
 741      * @return  {@code true} if the objects are the same;
 742      *          {@code false} otherwise.
 743      * @see     java.net.InetAddress#getAddress()
 744      */
 745     public boolean equals(Object obj) {
 746         return false;
 747     }
 748 
 749     /**
 750      * Converts this IP address to a {@code String}. The
 751      * string returned is of the form: hostname / literal IP
 752      * address.
 753      *
 754      * If the host name is unresolved, no reverse name service lookup
 755      * is performed. The hostname part will be represented by an empty string.
 756      *
 757      * @return  a string representation of this IP address.
 758      */
 759     public String toString() {
 760         String hostName = holder().getHostName();
 761         return Objects.toString(hostName, "")
 762             + "/" + getHostAddress();
 763     }
 764 
 765     // mapping from host name to Addresses - either NameServiceAddresses (while
 766     // still being looked-up by NameService(s)) or CachedAddresses when cached
 767     private static final ConcurrentMap<String, Addresses> cache =
 768         new ConcurrentHashMap<>();
 769 
 770     // CachedAddresses that have to expire are kept ordered in this NavigableSet
 771     // which is scanned on each access
 772     private static final NavigableSet<CachedAddresses> expirySet =
 773         new ConcurrentSkipListSet<>();
 774 
 775     // common interface
 776     private interface Addresses {
 777         InetAddress[] get() throws UnknownHostException;
 778     }
 779 
 780     // a holder for cached addresses with required metadata
 781     private static final class CachedAddresses  implements Addresses, Comparable<CachedAddresses> {
 782         private static final AtomicLong seq = new AtomicLong();
 783         final String host;
 784         final InetAddress[] inetAddresses;
 785         final long expiryTime; // time of expiry (in terms of System.nanoTime())
 786         final long id = seq.incrementAndGet(); // each instance is unique
 787 
 788         CachedAddresses(String host, InetAddress[] inetAddresses, long expiryTime) {
 789             this.host = host;
 790             this.inetAddresses = inetAddresses;
 791             this.expiryTime = expiryTime;
 792         }
 793 
 794         @Override
 795         public InetAddress[] get() throws UnknownHostException {
 796             if (inetAddresses == null) {
 797                 throw new UnknownHostException(host);
 798             }
 799             return inetAddresses;
 800         }
 801 
 802         @Override
 803         public int compareTo(CachedAddresses other) {
 804             // natural order is expiry time -
 805             // compare difference of expiry times rather than
 806             // expiry times directly, to avoid possible overflow.
 807             // (see System.nanoTime() recommendations...)
 808             long diff = this.expiryTime - other.expiryTime;
 809             if (diff < 0L) return -1;
 810             if (diff > 0L) return 1;
 811             // ties are broken using unique id
 812             return Long.compare(this.id, other.id);
 813         }
 814     }
 815 
 816     // a name service lookup based Addresses implementation which replaces itself
 817     // in cache when the result is obtained
 818     private static final class NameServiceAddresses implements Addresses {
 819         private final String host;
 820         private final InetAddress reqAddr;
 821 
 822         NameServiceAddresses(String host, InetAddress reqAddr) {
 823             this.host = host;
 824             this.reqAddr = reqAddr;
 825         }
 826 
 827         @Override
 828         public InetAddress[] get() throws UnknownHostException {
 829             Addresses addresses;
 830             // only one thread is doing lookup to name service
 831             // for particular host at any time.
 832             synchronized (this) {
 833                 // re-check that we are still us + re-install us if slot empty
 834                 addresses = cache.putIfAbsent(host, this);
 835                 if (addresses == null) {
 836                     // this can happen when we were replaced by CachedAddresses in
 837                     // some other thread, then CachedAddresses expired and were
 838                     // removed from cache while we were waiting for lock...
 839                     addresses = this;
 840                 }
 841                 // still us ?
 842                 if (addresses == this) {
 843                     // lookup name services
 844                     InetAddress[] inetAddresses;
 845                     UnknownHostException ex;
 846                     int cachePolicy;
 847                     try {
 848                         inetAddresses = getAddressesFromNameService(host, reqAddr);
 849                         ex = null;
 850                         cachePolicy = InetAddressCachePolicy.get();
 851                     } catch (UnknownHostException uhe) {
 852                         inetAddresses = null;
 853                         ex = uhe;
 854                         cachePolicy = InetAddressCachePolicy.getNegative();
 855                     }
 856                     // remove or replace us with cached addresses according to cachePolicy
 857                     if (cachePolicy == InetAddressCachePolicy.NEVER) {
 858                         cache.remove(host, this);
 859                     } else {
 860                         CachedAddresses cachedAddresses = new CachedAddresses(
 861                             host,
 862                             inetAddresses,
 863                             cachePolicy == InetAddressCachePolicy.FOREVER
 864                             ? 0L
 865                             // cachePolicy is in [s] - we need [ns]
 866                             : System.nanoTime() + 1000_000_000L * cachePolicy
 867                         );
 868                         if (cache.replace(host, this, cachedAddresses) &&
 869                             cachePolicy != InetAddressCachePolicy.FOREVER) {
 870                             // schedule expiry
 871                             expirySet.add(cachedAddresses);
 872                         }
 873                     }
 874                     if (inetAddresses == null) {
 875                         throw ex == null ? new UnknownHostException(host) : ex;
 876                     }
 877                     return inetAddresses;
 878                 }
 879                 // else addresses != this
 880             }
 881             // delegate to different addresses when we are already replaced
 882             // but outside of synchronized block to avoid any chance of dead-locking
 883             return addresses.get();
 884         }
 885     }
 886 
 887     /**
 888      * NameService provides host and address lookup service
 889      *
 890      * @since 9
 891      */
 892     private interface NameService {
 893 
 894         /**
 895          * Lookup a host mapping by name. Retrieve the IP addresses
 896          * associated with a host
 897          *
 898          * @param host the specified hostname
 899          * @return array of IP addresses for the requested host
 900          * @throws UnknownHostException
 901          *             if no IP address for the {@code host} could be found
 902          */
 903         InetAddress[] lookupAllHostAddr(String host)
 904                 throws UnknownHostException;
 905 
 906         /**
 907          * Lookup the host corresponding to the IP address provided
 908          *
 909          * @param addr byte array representing an IP address
 910          * @return {@code String} representing the host name mapping
 911          * @throws UnknownHostException
 912          *             if no host found for the specified IP address
 913          */
 914         String getHostByAddr(byte[] addr) throws UnknownHostException;
 915 
 916     }
 917 
 918     /**
 919      * The default NameService implementation, which delegates to the underlying
 920      * OS network libraries to resolve host address mappings.
 921      *
 922      * @since 9
 923      */
 924     private static final class PlatformNameService implements NameService {
 925 
 926         public InetAddress[] lookupAllHostAddr(String host)
 927             throws UnknownHostException
 928         {
 929             return impl.lookupAllHostAddr(host);
 930         }
 931 
 932         public String getHostByAddr(byte[] addr)
 933             throws UnknownHostException
 934         {
 935             return impl.getHostByAddr(addr);
 936         }
 937     }
 938 
 939     /**
 940      * The HostsFileNameService provides host address mapping
 941      * by reading the entries in a hosts file, which is specified by
 942      * {@code jdk.net.hosts.file} system property
 943      *
 944      * <p>The file format is that which corresponds with the /etc/hosts file
 945      * IP Address host alias list.
 946      *
 947      * <p>When the file lookup is enabled it replaces the default NameService
 948      * implementation
 949      *
 950      * @since 9
 951      */
 952     private static final class HostsFileNameService implements NameService {
 953 
 954         private final String hostsFile;
 955 
 956         public HostsFileNameService (String hostsFileName) {
 957             this.hostsFile = hostsFileName;
 958         }
 959 
 960         private  String addrToString(byte addr[]) {
 961           String stringifiedAddress = null;
 962 
 963             if (addr.length == Inet4Address.INADDRSZ) {
 964                 stringifiedAddress = Inet4Address.numericToTextFormat(addr);
 965             } else { // treat as an IPV6 jobby
 966                 byte[] newAddr
 967                     = IPAddressUtil.convertFromIPv4MappedAddress(addr);
 968                 if (newAddr != null) {
 969                    stringifiedAddress = Inet4Address.numericToTextFormat(addr);
 970                 } else {
 971                     stringifiedAddress = Inet6Address.numericToTextFormat(addr);
 972                 }
 973             }
 974             return stringifiedAddress;
 975         }
 976 
 977         /**
 978          * Lookup the host name  corresponding to the IP address provided.
 979          * Search the configured host file a host name corresponding to
 980          * the specified IP address.
 981          *
 982          * @param addr byte array representing an IP address
 983          * @return {@code String} representing the host name mapping
 984          * @throws UnknownHostException
 985          *             if no host found for the specified IP address
 986          */
 987         @Override
 988         public String getHostByAddr(byte[] addr) throws UnknownHostException {
 989             String hostEntry;
 990             String host = null;
 991 
 992             String addrString = addrToString(addr);
 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                         if (hostEntry.contains(addrString)) {
 999                             host = extractHost(hostEntry, addrString);
1000                             if (host != null) {
1001                                 break;
1002                             }
1003                         }
1004                     }
1005                 }
1006             } catch (FileNotFoundException e) {
1007                 throw new UnknownHostException("Unable to resolve address "
1008                         + addrString + " as hosts file " + hostsFile
1009                         + " not found ");
1010             }
1011 
1012             if ((host == null) || (host.equals("")) || (host.equals(" "))) {
1013                 throw new UnknownHostException("Requested address "
1014                         + addrString
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 assocaited with
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 specfied 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.equals(""))) {
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          * IP Address to host mapping
1113          * use first host alias in list
1114          */
1115         private String extractHost(String hostEntry, String addrString) {
1116             String[] mapping = hostEntry.split("\\s+");
1117             String host = null;
1118 
1119             if (mapping.length >= 2) {
1120                 if (mapping[0].equalsIgnoreCase(addrString)) {
1121                     host = mapping[1];
1122                 }
1123             }
1124             return host;
1125         }
1126     }
1127 
1128     static final InetAddressImpl  impl;
1129 
1130     static {
1131         // create the impl
1132         impl = InetAddressImplFactory.create();
1133 
1134         // create name service
1135         nameService = createNameService();
1136         }
1137 
1138     /**
1139      * Create an instance of the NameService interface based on
1140      * the setting of the {@code jdk.net.hosts.file} system property.
1141      *
1142      * <p>The default NameService is the PlatformNameService, which typically
1143      * delegates name and address resolution calls to the underlying
1144      * OS network libraries.
1145      *
1146      * <p> A HostsFileNameService is created if the {@code jdk.net.hosts.file}
1147      * system property is set. If the specified file doesn't exist, the name or
1148      * address lookup will result in an UnknownHostException. Thus, non existent
1149      * hosts file is handled as if the file is empty.
1150      *
1151      * @return a NameService
1152      */
1153     private static NameService createNameService() {
1154 
1155         String hostsFileName =
1156                 GetPropertyAction.privilegedGetProperty("jdk.net.hosts.file");
1157         NameService theNameService;
1158         if (hostsFileName != null) {
1159             theNameService = new HostsFileNameService(hostsFileName);
1160         } else {
1161             theNameService = new PlatformNameService();
1162         }
1163         return theNameService;
1164     }
1165 
1166     /**
1167      * Creates an InetAddress based on the provided host name and IP address.
1168      * No name service is checked for the validity of the address.
1169      *
1170      * <p> The host name can either be a machine name, such as
1171      * "{@code java.sun.com}", or a textual representation of its IP
1172      * address.
1173      * <p> No validity checking is done on the host name either.
1174      *
1175      * <p> If addr specifies an IPv4 address an instance of Inet4Address
1176      * will be returned; otherwise, an instance of Inet6Address
1177      * will be returned.
1178      *
1179      * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
1180      * must be 16 bytes long
1181      *
1182      * @param host the specified host
1183      * @param addr the raw IP address in network byte order
1184      * @return  an InetAddress object created from the raw IP address.
1185      * @exception  UnknownHostException  if IP address is of illegal length
1186      * @since 1.4
1187      */
1188     public static InetAddress getByAddress(String host, byte[] addr)
1189         throws UnknownHostException {
1190         if (host != null && !host.isEmpty() && host.charAt(0) == '[') {
1191             if (host.charAt(host.length()-1) == ']') {
1192                 host = host.substring(1, host.length() -1);
1193             }
1194         }
1195         if (addr != null) {
1196             if (addr.length == Inet4Address.INADDRSZ) {
1197                 return new Inet4Address(host, addr);
1198             } else if (addr.length == Inet6Address.INADDRSZ) {
1199                 byte[] newAddr
1200                     = IPAddressUtil.convertFromIPv4MappedAddress(addr);
1201                 if (newAddr != null) {
1202                     return new Inet4Address(host, newAddr);
1203                 } else {
1204                     return new Inet6Address(host, addr);
1205                 }
1206             }
1207         }
1208         throw new UnknownHostException("addr is of illegal length");
1209     }
1210 
1211 
1212     /**
1213      * Determines the IP address of a host, given the host's name.
1214      *
1215      * <p> The host name can either be a machine name, such as
1216      * "{@code java.sun.com}", or a textual representation of its
1217      * IP address. If a literal IP address is supplied, only the
1218      * validity of the address format is checked.
1219      *
1220      * <p> For {@code host} specified in literal IPv6 address,
1221      * either the form defined in RFC 2732 or the literal IPv6 address
1222      * format defined in RFC 2373 is accepted. IPv6 scoped addresses are also
1223      * supported. See <a href="Inet6Address.html#scoped">here</a> for a description of IPv6
1224      * scoped addresses.
1225      *
1226      * <p> If the host is {@code null} or {@code host.length()} is equal
1227      * to zero, then an {@code InetAddress} representing an address of the
1228      * loopback interface is returned.
1229      * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC&nbsp;3330</a>
1230      * section&nbsp;2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC&nbsp;2373</a>
1231      * section&nbsp;2.5.3.
1232      *
1233      * <p> If there is a security manager, and {@code host} is not {@code null}
1234      * or {@code host.length() } is not equal to zero, the security manager's
1235      * {@code checkConnect} method is called with the hostname and {@code -1}
1236      * as its arguments to determine if the operation is allowed.
1237      *
1238      * @param      host   the specified host, or {@code null}.
1239      * @return     an IP address for the given host name.
1240      * @exception  UnknownHostException  if no IP address for the
1241      *               {@code host} could be found, or if a scope_id was specified
1242      *               for a global IPv6 address.
1243      * @exception  SecurityException if a security manager exists
1244      *             and its checkConnect method doesn't allow the operation
1245      */
1246     public static InetAddress getByName(String host)
1247         throws UnknownHostException {
1248         return InetAddress.getAllByName(host)[0];
1249     }
1250 
1251     // called from deployment cache manager
1252     private static InetAddress getByName(String host, InetAddress reqAddr)
1253         throws UnknownHostException {
1254         return InetAddress.getAllByName(host, reqAddr)[0];
1255     }
1256 
1257     /**
1258      * Given the name of a host, returns an array of its IP addresses,
1259      * based on the configured name service on the system.
1260      *
1261      * <p> The host name can either be a machine name, such as
1262      * "{@code java.sun.com}", or a textual representation of its IP
1263      * address. If a literal IP address is supplied, only the
1264      * validity of the address format is checked.
1265      *
1266      * <p> For {@code host} specified in <i>literal IPv6 address</i>,
1267      * either the form defined in RFC 2732 or the literal IPv6 address
1268      * format defined in RFC 2373 is accepted. A literal IPv6 address may
1269      * also be qualified by appending a scoped zone identifier or scope_id.
1270      * The syntax and usage of scope_ids is described
1271      * <a href="Inet6Address.html#scoped">here</a>.
1272      *
1273      * <p> If the host is {@code null} or {@code host.length()} is equal
1274      * to zero, then an {@code InetAddress} representing an address of the
1275      * loopback interface is returned.
1276      * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC&nbsp;3330</a>
1277      * section&nbsp;2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC&nbsp;2373</a>
1278      * section&nbsp;2.5.3. </p>
1279      *
1280      * <p> If there is a security manager, and {@code host} is not {@code null}
1281      * or {@code host.length() } is not equal to zero, the security manager's
1282      * {@code checkConnect} method is called with the hostname and {@code -1}
1283      * as its arguments to determine if the operation is allowed.
1284      *
1285      * @param      host   the name of the host, or {@code null}.
1286      * @return     an array of all the IP addresses for a given host name.
1287      *
1288      * @exception  UnknownHostException  if no IP address for the
1289      *               {@code host} could be found, or if a scope_id was specified
1290      *               for a global IPv6 address.
1291      * @exception  SecurityException  if a security manager exists and its
1292      *               {@code checkConnect} method doesn't allow the operation.
1293      *
1294      * @see SecurityManager#checkConnect
1295      */
1296     public static InetAddress[] getAllByName(String host)
1297         throws UnknownHostException {
1298         return getAllByName(host, null);
1299     }
1300 
1301     private static InetAddress[] getAllByName(String host, InetAddress reqAddr)
1302         throws UnknownHostException {
1303 
1304         if (host == null || host.isEmpty()) {
1305             InetAddress[] ret = new InetAddress[1];
1306             ret[0] = impl.loopbackAddress();
1307             return ret;
1308         }
1309 
1310         boolean ipv6Expected = false;
1311         if (host.charAt(0) == '[') {
1312             // This is supposed to be an IPv6 literal
1313             if (host.length() > 2 && host.charAt(host.length()-1) == ']') {
1314                 host = host.substring(1, host.length() -1);
1315                 ipv6Expected = true;
1316             } else {
1317                 // This was supposed to be a IPv6 address, but it's not!
1318                 throw new UnknownHostException(host + ": invalid IPv6 address");
1319             }
1320         }
1321 
1322         // if host is an IP address, we won't do further lookup
1323         if (Character.digit(host.charAt(0), 16) != -1
1324             || (host.charAt(0) == ':')) {
1325             byte[] addr = null;
1326             int numericZone = -1;
1327             String ifname = null;
1328             // see if it is IPv4 address
1329             addr = IPAddressUtil.textToNumericFormatV4(host);
1330             if (addr == null) {
1331                 // This is supposed to be an IPv6 literal
1332                 // Check if a numeric or string zone id is present
1333                 int pos;
1334                 if ((pos=host.indexOf ('%')) != -1) {
1335                     numericZone = checkNumericZone (host);
1336                     if (numericZone == -1) { /* remainder of string must be an ifname */
1337                         ifname = host.substring (pos+1);
1338                     }
1339                 }
1340                 if ((addr = IPAddressUtil.textToNumericFormatV6(host)) == null && host.contains(":")) {
1341                     throw new UnknownHostException(host + ": invalid IPv6 address");
1342                 }
1343             } else if (ipv6Expected) {
1344                 // Means an IPv4 litteral between brackets!
1345                 throw new UnknownHostException("["+host+"]");
1346             }
1347             InetAddress[] ret = new InetAddress[1];
1348             if(addr != null) {
1349                 if (addr.length == Inet4Address.INADDRSZ) {
1350                     ret[0] = new Inet4Address(null, addr);
1351                 } else {
1352                     if (ifname != null) {
1353                         ret[0] = new Inet6Address(null, addr, ifname);
1354                     } else {
1355                         ret[0] = new Inet6Address(null, addr, numericZone);
1356                     }
1357                 }
1358                 return ret;
1359             }
1360         } else if (ipv6Expected) {
1361             // We were expecting an IPv6 Litteral, but got something else
1362             throw new UnknownHostException("["+host+"]");
1363         }
1364         return getAllByName0(host, reqAddr, true, true);
1365     }
1366 
1367     /**
1368      * Returns the loopback address.
1369      * <p>
1370      * The InetAddress returned will represent the IPv4
1371      * loopback address, 127.0.0.1, or the IPv6 loopback
1372      * address, ::1. The IPv4 loopback address returned
1373      * is only one of many in the form 127.*.*.*
1374      *
1375      * @return  the InetAddress loopback instance.
1376      * @since 1.7
1377      */
1378     public static InetAddress getLoopbackAddress() {
1379         return impl.loopbackAddress();
1380     }
1381 
1382 
1383     /**
1384      * check if the literal address string has %nn appended
1385      * returns -1 if not, or the numeric value otherwise.
1386      *
1387      * %nn may also be a string that represents the displayName of
1388      * a currently available NetworkInterface.
1389      */
1390     private static int checkNumericZone (String s) throws UnknownHostException {
1391         int percent = s.indexOf ('%');
1392         int slen = s.length();
1393         int digit, zone=0;
1394         if (percent == -1) {
1395             return -1;
1396         }
1397         for (int i=percent+1; i<slen; i++) {
1398             char c = s.charAt(i);
1399             if (c == ']') {
1400                 if (i == percent+1) {
1401                     /* empty per-cent field */
1402                     return -1;
1403                 }
1404                 break;
1405             }
1406             if ((digit = Character.digit (c, 10)) < 0) {
1407                 return -1;
1408             }
1409             zone = (zone * 10) + digit;
1410         }
1411         return zone;
1412     }
1413 
1414     private static InetAddress[] getAllByName0 (String host)
1415         throws UnknownHostException
1416     {
1417         return getAllByName0(host, true);
1418     }
1419 
1420     /**
1421      * package private so SocketPermission can call it
1422      */
1423     static InetAddress[] getAllByName0 (String host, boolean check)
1424         throws UnknownHostException  {
1425         return getAllByName0 (host, null, check, true);
1426     }
1427 
1428     /**
1429      * Designated lookup method.
1430      *
1431      * @param host host name to look up
1432      * @param reqAddr requested address to be the 1st in returned array
1433      * @param check perform security check
1434      * @param useCache use cached value if not expired else always
1435      *                 perform name service lookup (and cache the result)
1436      * @return array of InetAddress(es)
1437      * @throws UnknownHostException if host name is not found
1438      */
1439     private static InetAddress[] getAllByName0(String host,
1440                                                InetAddress reqAddr,
1441                                                boolean check,
1442                                                boolean useCache)
1443         throws UnknownHostException  {
1444 
1445         /* If it gets here it is presumed to be a hostname */
1446 
1447         /* make sure the connection to the host is allowed, before we
1448          * give out a hostname
1449          */
1450         if (check) {
1451             SecurityManager security = System.getSecurityManager();
1452             if (security != null) {
1453                 security.checkConnect(host, -1);
1454             }
1455         }
1456 
1457         // remove expired addresses from cache - expirySet keeps them ordered
1458         // by expiry time so we only need to iterate the prefix of the NavigableSet...
1459         long now = System.nanoTime();
1460         for (CachedAddresses caddrs : expirySet) {
1461             // compare difference of time instants rather than
1462             // time instants directly, to avoid possible overflow.
1463             // (see System.nanoTime() recommendations...)
1464             if ((caddrs.expiryTime - now) < 0L) {
1465                 // ConcurrentSkipListSet uses weakly consistent iterator,
1466                 // so removing while iterating is OK...
1467                 if (expirySet.remove(caddrs)) {
1468                     // ... remove from cache
1469                     cache.remove(caddrs.host, caddrs);
1470                 }
1471             } else {
1472                 // we encountered 1st element that expires in future
1473                 break;
1474             }
1475         }
1476 
1477         // look-up or remove from cache
1478         Addresses addrs;
1479         if (useCache) {
1480             addrs = cache.get(host);
1481         } else {
1482             addrs = cache.remove(host);
1483             if (addrs != null) {
1484                 if (addrs instanceof CachedAddresses) {
1485                     // try removing from expirySet too if CachedAddresses
1486                     expirySet.remove(addrs);
1487                 }
1488                 addrs = null;
1489             }
1490         }
1491 
1492         if (addrs == null) {
1493             // create a NameServiceAddresses instance which will look up
1494             // the name service and install it within cache...
1495             Addresses oldAddrs = cache.putIfAbsent(
1496                 host,
1497                 addrs = new NameServiceAddresses(host, reqAddr)
1498             );
1499             if (oldAddrs != null) { // lost putIfAbsent race
1500                 addrs = oldAddrs;
1501             }
1502         }
1503 
1504         // ask Addresses to get an array of InetAddress(es) and clone it
1505         return addrs.get().clone();
1506     }
1507 
1508     static InetAddress[] getAddressesFromNameService(String host, InetAddress reqAddr)
1509         throws UnknownHostException
1510     {
1511         InetAddress[] addresses = null;
1512         UnknownHostException ex = null;
1513 
1514             try {
1515                 addresses = nameService.lookupAllHostAddr(host);
1516             } catch (UnknownHostException uhe) {
1517                 if (host.equalsIgnoreCase("localhost")) {
1518                     addresses = new InetAddress[] { impl.loopbackAddress() };
1519                 }
1520                 else {
1521                     ex = uhe;
1522                 }
1523             }
1524 
1525         if (addresses == null) {
1526             throw ex == null ? new UnknownHostException(host) : ex;
1527         }
1528 
1529         // More to do?
1530         if (reqAddr != null && addresses.length > 1 && !addresses[0].equals(reqAddr)) {
1531             // Find it?
1532             int i = 1;
1533             for (; i < addresses.length; i++) {
1534                 if (addresses[i].equals(reqAddr)) {
1535                     break;
1536                 }
1537             }
1538             // Rotate
1539             if (i < addresses.length) {
1540                 InetAddress tmp, tmp2 = reqAddr;
1541                 for (int j = 0; j < i; j++) {
1542                     tmp = addresses[j];
1543                     addresses[j] = tmp2;
1544                     tmp2 = tmp;
1545                 }
1546                 addresses[i] = tmp2;
1547             }
1548         }
1549 
1550         return addresses;
1551     }
1552 
1553     /**
1554      * Returns an {@code InetAddress} object given the raw IP address .
1555      * The argument is in network byte order: the highest order
1556      * byte of the address is in {@code getAddress()[0]}.
1557      *
1558      * <p> This method doesn't block, i.e. no reverse name service lookup
1559      * is performed.
1560      *
1561      * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
1562      * must be 16 bytes long
1563      *
1564      * @param addr the raw IP address in network byte order
1565      * @return  an InetAddress object created from the raw IP address.
1566      * @exception  UnknownHostException  if IP address is of illegal length
1567      * @since 1.4
1568      */
1569     public static InetAddress getByAddress(byte[] addr)
1570         throws UnknownHostException {
1571         return getByAddress(null, addr);
1572     }
1573 
1574     private static final class CachedLocalHost {
1575         final String host;
1576         final InetAddress addr;
1577         final long expiryTime = System.nanoTime() + 5000_000_000L; // now + 5s;
1578 
1579         CachedLocalHost(String host, InetAddress addr) {
1580             this.host = host;
1581             this.addr = addr;
1582         }
1583     }
1584 
1585     private static volatile CachedLocalHost cachedLocalHost;
1586 
1587     /**
1588      * Returns the address of the local host. This is achieved by retrieving
1589      * the name of the host from the system, then resolving that name into
1590      * an {@code InetAddress}.
1591      *
1592      * <P>Note: The resolved address may be cached for a short period of time.
1593      * </P>
1594      *
1595      * <p>If there is a security manager, its
1596      * {@code checkConnect} method is called
1597      * with the local host name and {@code -1}
1598      * as its arguments to see if the operation is allowed.
1599      * If the operation is not allowed, an InetAddress representing
1600      * the loopback address is returned.
1601      *
1602      * @return     the address of the local host.
1603      *
1604      * @exception  UnknownHostException  if the local host name could not
1605      *             be resolved into an address.
1606      *
1607      * @see SecurityManager#checkConnect
1608      * @see java.net.InetAddress#getByName(java.lang.String)
1609      */
1610     public static InetAddress getLocalHost() throws UnknownHostException {
1611 
1612         SecurityManager security = System.getSecurityManager();
1613         try {
1614             // is cached data still valid?
1615             CachedLocalHost clh = cachedLocalHost;
1616             if (clh != null && (clh.expiryTime - System.nanoTime()) >= 0L) {
1617                 if (security != null) {
1618                     security.checkConnect(clh.host, -1);
1619                 }
1620                 return clh.addr;
1621             }
1622 
1623             String local = impl.getLocalHostName();
1624 
1625             if (security != null) {
1626                 security.checkConnect(local, -1);
1627             }
1628 
1629             InetAddress localAddr;
1630             if (local.equals("localhost")) {
1631                 // shortcut for "localhost" host name
1632                 localAddr = impl.loopbackAddress();
1633             } else {
1634                 // call getAllByName0 without security checks and
1635                 // without using cached data
1636                 try {
1637                     localAddr = getAllByName0(local, null, false, false)[0];
1638                 } catch (UnknownHostException uhe) {
1639                     // Rethrow with a more informative error message.
1640                     UnknownHostException uhe2 =
1641                         new UnknownHostException(local + ": " +
1642                                                  uhe.getMessage());
1643                     uhe2.initCause(uhe);
1644                     throw uhe2;
1645                 }
1646             }
1647             cachedLocalHost = new CachedLocalHost(local, localAddr);
1648             return localAddr;
1649         } catch (java.lang.SecurityException e) {
1650             return impl.loopbackAddress();
1651         }
1652     }
1653 
1654     /**
1655      * Perform class load-time initializations.
1656      */
1657     private static native void init();
1658 
1659 
1660     /*
1661      * Returns the InetAddress representing anyLocalAddress
1662      * (typically 0.0.0.0 or ::0)
1663      */
1664     static InetAddress anyLocalAddress() {
1665         return impl.anyLocalAddress();
1666     }
1667 
1668     /*
1669      * Load and instantiate an underlying impl class
1670      */
1671     static InetAddressImpl loadImpl(String implName) {
1672         Object impl = null;
1673 
1674         /*
1675          * Property "impl.prefix" will be prepended to the classname
1676          * of the implementation object we instantiate, to which we
1677          * delegate the real work (like native methods).  This
1678          * property can vary across implementations of the java.
1679          * classes.  The default is an empty String "".
1680          */
1681         String prefix = GetPropertyAction.privilegedGetProperty("impl.prefix", "");
1682         try {
1683             @SuppressWarnings("deprecation")
1684             Object tmp = Class.forName("java.net." + prefix + implName).newInstance();
1685             impl = tmp;
1686         } catch (ClassNotFoundException e) {
1687             System.err.println("Class not found: java.net." + prefix +
1688                                implName + ":\ncheck impl.prefix property " +
1689                                "in your properties file.");
1690         } catch (InstantiationException e) {
1691             System.err.println("Could not instantiate: java.net." + prefix +
1692                                implName + ":\ncheck impl.prefix property " +
1693                                "in your properties file.");
1694         } catch (IllegalAccessException e) {
1695             System.err.println("Cannot access class: java.net." + prefix +
1696                                implName + ":\ncheck impl.prefix property " +
1697                                "in your properties file.");
1698         }
1699 
1700         if (impl == null) {
1701             try {
1702                 @SuppressWarnings("deprecation")
1703                 Object tmp = Class.forName(implName).newInstance();
1704                 impl = tmp;
1705             } catch (Exception e) {
1706                 throw new Error("System property impl.prefix incorrect");
1707             }
1708         }
1709 
1710         return (InetAddressImpl) impl;
1711     }
1712 
1713     private void readObjectNoData () throws
1714                          IOException, ClassNotFoundException {
1715         if (getClass().getClassLoader() != null) {
1716             throw new SecurityException ("invalid address type");
1717         }
1718     }
1719 
1720     private static final jdk.internal.misc.Unsafe UNSAFE
1721             = jdk.internal.misc.Unsafe.getUnsafe();
1722     private static final long FIELDS_OFFSET
1723             = UNSAFE.objectFieldOffset(InetAddress.class, "holder");
1724 
1725     private void readObject (ObjectInputStream s) throws
1726                          IOException, ClassNotFoundException {
1727         if (getClass().getClassLoader() != null) {
1728             throw new SecurityException ("invalid address type");
1729         }
1730         GetField gf = s.readFields();
1731         String host = (String)gf.get("hostName", null);
1732         int address = gf.get("address", 0);
1733         int family = gf.get("family", 0);
1734         if (family != IPv4 && family != IPv6) {
1735             throw new InvalidObjectException("invalid address family type: " + family);
1736         }
1737         InetAddressHolder h = new InetAddressHolder(host, address, family);
1738         UNSAFE.putObject(this, FIELDS_OFFSET, h);
1739     }
1740 
1741     /* needed because the serializable fields no longer exist */
1742 
1743     /**
1744      * @serialField hostName String
1745      * @serialField address int
1746      * @serialField family int
1747      */
1748     private static final ObjectStreamField[] serialPersistentFields = {
1749         new ObjectStreamField("hostName", String.class),
1750         new ObjectStreamField("address", int.class),
1751         new ObjectStreamField("family", int.class),
1752     };
1753 
1754     private void writeObject (ObjectOutputStream s) throws
1755                         IOException {
1756         if (getClass().getClassLoader() != null) {
1757             throw new SecurityException ("invalid address type");
1758         }
1759         PutField pf = s.putFields();
1760         pf.put("hostName", holder().getHostName());
1761         pf.put("address", holder().getAddress());
1762         pf.put("family", holder().getFamily());
1763         s.writeFields();
1764     }
1765 }
1766 
1767 /*
1768  * Simple factory to create the impl
1769  */
1770 class InetAddressImplFactory {
1771 
1772     static InetAddressImpl create() {
1773         return InetAddress.loadImpl(isIPv6Supported() ?
1774                                     "Inet6AddressImpl" : "Inet4AddressImpl");
1775     }
1776 
1777     static native boolean isIPv6Supported();
1778 }
--- EOF ---