1 /*
   2  * Copyright (c) 1995, 2017, 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.ObjectInputStream;
  39 import java.io.ObjectInputStream.GetField;
  40 import java.io.ObjectOutputStream;
  41 import java.io.ObjectOutputStream.PutField;
  42 import java.lang.annotation.Native;
  43 import java.util.concurrent.ConcurrentHashMap;
  44 import java.util.concurrent.ConcurrentMap;
  45 import java.util.concurrent.ConcurrentSkipListSet;
  46 import java.util.concurrent.atomic.AtomicLong;
  47 
  48 import jdk.internal.misc.JavaNetInetAddressAccess;
  49 import jdk.internal.misc.SharedSecrets;
  50 import sun.security.action.*;
  51 import sun.net.InetAddressCachePolicy;
  52 import sun.net.util.IPAddressUtil;
  53 
  54 /**
  55  * This class represents an Internet Protocol (IP) address.
  56  *
  57  * <p> An IP address is either a 32-bit or 128-bit unsigned number
  58  * used by IP, a lower-level protocol on which protocols like UDP and
  59  * TCP are built. The IP address architecture is defined by <a
  60  * href="http://www.ietf.org/rfc/rfc790.txt"><i>RFC&nbsp;790:
  61  * Assigned Numbers</i></a>, <a
  62  * href="http://www.ietf.org/rfc/rfc1918.txt"> <i>RFC&nbsp;1918:
  63  * Address Allocation for Private Internets</i></a>, <a
  64  * href="http://www.ietf.org/rfc/rfc2365.txt"><i>RFC&nbsp;2365:
  65  * Administratively Scoped IP Multicast</i></a>, and <a
  66  * href="http://www.ietf.org/rfc/rfc2373.txt"><i>RFC&nbsp;2373: IP
  67  * Version 6 Addressing Architecture</i></a>. An instance of an
  68  * InetAddress consists of an IP address and possibly its
  69  * corresponding host name (depending on whether it is constructed
  70  * with a host name or whether it has already done reverse host name
  71  * resolution).
  72  *
  73  * <h3> Address types </h3>
  74  *
  75  * <table class="striped" style="margin-left:2em">
  76  *   <caption style="display:none">Description of unicast and multicast address types</caption>
  77  *   <thead>
  78  *   <tr><th scope="col">Address Type</th><th scope="col">Description</th></tr>
  79  *   </thead>
  80  *   <tbody>
  81  *   <tr><th scope="row" style="vertical-align:top">unicast</th>
  82  *       <td>An identifier for a single interface. A packet sent to
  83  *         a unicast address is delivered to the interface identified by
  84  *         that address.
  85  *
  86  *         <p> The Unspecified Address -- Also called anylocal or wildcard
  87  *         address. It must never be assigned to any node. It indicates the
  88  *         absence of an address. One example of its use is as the target of
  89  *         bind, which allows a server to accept a client connection on any
  90  *         interface, in case the server host has multiple interfaces.
  91  *
  92  *         <p> The <i>unspecified</i> address must not be used as
  93  *         the destination address of an IP packet.
  94  *
  95  *         <p> The <i>Loopback</i> Addresses -- This is the address
  96  *         assigned to the loopback interface. Anything sent to this
  97  *         IP address loops around and becomes IP input on the local
  98  *         host. This address is often used when testing a
  99  *         client.</td></tr>
 100  *   <tr><th scope="row" style="vertical-align:top">multicast</th>
 101  *       <td>An identifier for a set of interfaces (typically belonging
 102  *         to different nodes). A packet sent to a multicast address is
 103  *         delivered to all interfaces identified by that address.</td></tr>
 104  * </tbody>
 105  * </table>
 106  *
 107  * <h4> IP address scope </h4>
 108  *
 109  * <p> <i>Link-local</i> addresses are designed to be used for addressing
 110  * on a single link for purposes such as auto-address configuration,
 111  * neighbor discovery, or when no routers are present.
 112  *
 113  * <p> <i>Site-local</i> addresses are designed to be used for addressing
 114  * inside of a site without the need for a global prefix.
 115  *
 116  * <p> <i>Global</i> addresses are unique across the internet.
 117  *
 118  * <h4> Textual representation of IP addresses </h4>
 119  *
 120  * The textual representation of an IP address is address family specific.
 121  *
 122  * <p>
 123  *
 124  * For IPv4 address format, please refer to <A
 125  * HREF="Inet4Address.html#format">Inet4Address#format</A>; For IPv6
 126  * address format, please refer to <A
 127  * HREF="Inet6Address.html#format">Inet6Address#format</A>.
 128  *
 129  * <P>There is a <a href="doc-files/net-properties.html#Ipv4IPv6">couple of
 130  * System Properties</a> affecting how IPv4 and IPv6 addresses are used.</P>
 131  *
 132  * <h4> Host Name Resolution </h4>
 133  *
 134  * Host name-to-IP address <i>resolution</i> is accomplished through
 135  * the use of a combination of local machine configuration information
 136  * and network naming services such as the Domain Name System (DNS)
 137  * and Network Information Service(NIS). The particular naming
 138  * services(s) being used is by default the local machine configured
 139  * one. For any host name, its corresponding IP address is returned.
 140  *
 141  * <p> <i>Reverse name resolution</i> means that for any IP address,
 142  * the host associated with the IP address is returned.
 143  *
 144  * <p> The InetAddress class provides methods to resolve host names to
 145  * their IP addresses and vice versa.
 146  *
 147  * <h4> InetAddress Caching </h4>
 148  *
 149  * The InetAddress class has a cache to store successful as well as
 150  * unsuccessful host name resolutions.
 151  *
 152  * <p> By default, when a security manager is installed, in order to
 153  * protect against DNS spoofing attacks,
 154  * the result of positive host name resolutions are
 155  * cached forever. When a security manager is not installed, the default
 156  * behavior is to cache entries for a finite (implementation dependent)
 157  * period of time. The result of unsuccessful host
 158  * name resolution is cached for a very short period of time (10
 159  * seconds) to improve performance.
 160  *
 161  * <p> If the default behavior is not desired, then a Java security property
 162  * can be set to a different Time-to-live (TTL) value for positive
 163  * caching. Likewise, a system admin can configure a different
 164  * negative caching TTL value when needed.
 165  *
 166  * <p> Two Java security properties control the TTL values used for
 167  *  positive and negative host name resolution caching:
 168  *
 169  * <dl style="margin-left:2em">
 170  * <dt><b>networkaddress.cache.ttl</b></dt>
 171  * <dd>Indicates the caching policy for successful name lookups from
 172  * the name service. The value is specified as an integer to indicate
 173  * the number of seconds to cache the successful lookup. The default
 174  * setting is to cache for an implementation specific period of time.
 175  * <p>
 176  * A value of -1 indicates "cache forever".
 177  * </dd>
 178  * <dt><b>networkaddress.cache.negative.ttl</b> (default: 10)</dt>
 179  * <dd>Indicates the caching policy for un-successful name lookups
 180  * from the name service. The value is specified as an integer to
 181  * indicate the number of seconds to cache the failure for
 182  * un-successful lookups.
 183  * <p>
 184  * A value of 0 indicates "never cache".
 185  * A value of -1 indicates "cache forever".
 186  * </dd>
 187  * </dl>
 188  *
 189  * @author  Chris Warth
 190  * @see     java.net.InetAddress#getByAddress(byte[])
 191  * @see     java.net.InetAddress#getByAddress(java.lang.String, byte[])
 192  * @see     java.net.InetAddress#getAllByName(java.lang.String)
 193  * @see     java.net.InetAddress#getByName(java.lang.String)
 194  * @see     java.net.InetAddress#getLocalHost()
 195  * @since 1.0
 196  */
 197 public
 198 class InetAddress implements java.io.Serializable {
 199 
 200     @Native static final int PREFER_IPV4_VALUE = 0;
 201     @Native static final int PREFER_IPV6_VALUE = 1;
 202     @Native static final int PREFER_SYSTEM_VALUE = 2;
 203 
 204     /**
 205      * Specify the address family: Internet Protocol, Version 4
 206      * @since 1.4
 207      */
 208     @Native static final int IPv4 = 1;
 209 
 210     /**
 211      * Specify the address family: Internet Protocol, Version 6
 212      * @since 1.4
 213      */
 214     @Native static final int IPv6 = 2;
 215 
 216     /* Specify address family preference */
 217     static transient final int preferIPv6Address;
 218 
 219     static class InetAddressHolder {
 220         /**
 221          * Reserve the original application specified hostname.
 222          *
 223          * The original hostname is useful for domain-based endpoint
 224          * identification (see RFC 2818 and RFC 6125).  If an address
 225          * was created with a raw IP address, a reverse name lookup
 226          * may introduce endpoint identification security issue via
 227          * DNS forging.
 228          *
 229          * Oracle JSSE provider is using this original hostname, via
 230          * jdk.internal.misc.JavaNetAccess, for SSL/TLS endpoint identification.
 231          *
 232          * Note: May define a new public method in the future if necessary.
 233          */
 234         String originalHostName;
 235 
 236         InetAddressHolder() {}
 237 
 238         InetAddressHolder(String hostName, int address, int family) {
 239             this.originalHostName = hostName;
 240             this.hostName = hostName;
 241             this.address = address;
 242             this.family = family;
 243         }
 244 
 245         void init(String hostName, int family) {
 246             this.originalHostName = hostName;
 247             this.hostName = hostName;
 248             if (family != -1) {
 249                 this.family = family;
 250             }
 251         }
 252 
 253         String hostName;
 254 
 255         String getHostName() {
 256             return hostName;
 257         }
 258 
 259         String getOriginalHostName() {
 260             return originalHostName;
 261         }
 262 
 263         /**
 264          * Holds a 32-bit IPv4 address.
 265          */
 266         int address;
 267 
 268         int getAddress() {
 269             return address;
 270         }
 271 
 272         /**
 273          * Specifies the address family type, for instance, '1' for IPv4
 274          * addresses, and '2' for IPv6 addresses.
 275          */
 276         int family;
 277 
 278         int getFamily() {
 279             return family;
 280         }
 281     }
 282 
 283     /* Used to store the serializable fields of InetAddress */
 284     final transient InetAddressHolder holder;
 285 
 286     InetAddressHolder holder() {
 287         return holder;
 288     }
 289 
 290     /* Used to store the name service provider */
 291     private static transient NameService nameService = null;
 292 
 293     /**
 294      * Used to store the best available hostname.
 295      * Lazily initialized via a data race; safe because Strings are immutable.
 296      */
 297     private transient String canonicalHostName = null;
 298 
 299     /** use serialVersionUID from JDK 1.0.2 for interoperability */
 300     private static final long serialVersionUID = 3286316764910316507L;
 301 
 302     /*
 303      * Load net library into runtime, and perform initializations.
 304      */
 305     static {
 306         String str = java.security.AccessController.doPrivileged(
 307                 new GetPropertyAction("java.net.preferIPv6Addresses"));
 308         if (str == null) {
 309             preferIPv6Address = PREFER_IPV4_VALUE;
 310         } else if (str.equalsIgnoreCase("true")) {
 311             preferIPv6Address = PREFER_IPV6_VALUE;
 312         } else if (str.equalsIgnoreCase("false")) {
 313             preferIPv6Address = PREFER_IPV4_VALUE;
 314         } else if (str.equalsIgnoreCase("system")) {
 315             preferIPv6Address = PREFER_SYSTEM_VALUE;
 316         } else {
 317             preferIPv6Address = PREFER_IPV4_VALUE;
 318         }
 319         AccessController.doPrivileged(
 320             new java.security.PrivilegedAction<>() {
 321                 public Void run() {
 322                     System.loadLibrary("net");
 323                     return null;
 324                 }
 325             });
 326         SharedSecrets.setJavaNetInetAddressAccess(
 327                 new JavaNetInetAddressAccess() {
 328                     public String getOriginalHostName(InetAddress ia) {
 329                         return ia.holder.getOriginalHostName();
 330                     }
 331 
 332                     public InetAddress getByName(String hostName,
 333                                                  InetAddress hostAddress)
 334                             throws UnknownHostException
 335                     {
 336                         return InetAddress.getByName(hostName, hostAddress);
 337                     }
 338                 }
 339         );
 340         init();
 341     }
 342 
 343     /**
 344      * Constructor for the Socket.accept() method.
 345      * This creates an empty InetAddress, which is filled in by
 346      * the accept() method.  This InetAddress, however, is not
 347      * put in the address cache, since it is not created by name.
 348      */
 349     InetAddress() {
 350         holder = new InetAddressHolder();
 351     }
 352 
 353     /**
 354      * Replaces the de-serialized object with an Inet4Address object.
 355      *
 356      * @return the alternate object to the de-serialized object.
 357      *
 358      * @throws ObjectStreamException if a new object replacing this
 359      * object could not be created
 360      */
 361     private Object readResolve() throws ObjectStreamException {
 362         // will replace the deserialized 'this' object
 363         return new Inet4Address(holder().getHostName(), holder().getAddress());
 364     }
 365 
 366     /**
 367      * Utility routine to check if the InetAddress is an
 368      * IP multicast address.
 369      * @return a {@code boolean} indicating if the InetAddress is
 370      * an IP multicast address
 371      * @since   1.1
 372      */
 373     public boolean isMulticastAddress() {
 374         return false;
 375     }
 376 
 377     /**
 378      * Utility routine to check if the InetAddress is a wildcard address.
 379      * @return a {@code boolean} indicating if the Inetaddress is
 380      *         a wildcard address.
 381      * @since 1.4
 382      */
 383     public boolean isAnyLocalAddress() {
 384         return false;
 385     }
 386 
 387     /**
 388      * Utility routine to check if the InetAddress is a loopback address.
 389      *
 390      * @return a {@code boolean} indicating if the InetAddress is
 391      * a loopback address; or false otherwise.
 392      * @since 1.4
 393      */
 394     public boolean isLoopbackAddress() {
 395         return false;
 396     }
 397 
 398     /**
 399      * Utility routine to check if the InetAddress is an link local address.
 400      *
 401      * @return a {@code boolean} indicating if the InetAddress is
 402      * a link local address; or false if address is not a link local unicast address.
 403      * @since 1.4
 404      */
 405     public boolean isLinkLocalAddress() {
 406         return false;
 407     }
 408 
 409     /**
 410      * Utility routine to check if the InetAddress is a site local address.
 411      *
 412      * @return a {@code boolean} indicating if the InetAddress is
 413      * a site local address; or false if address is not a site local unicast address.
 414      * @since 1.4
 415      */
 416     public boolean isSiteLocalAddress() {
 417         return false;
 418     }
 419 
 420     /**
 421      * Utility routine to check if the multicast address has global scope.
 422      *
 423      * @return a {@code boolean} indicating if the address has
 424      *         is a multicast address of global scope, false if it is not
 425      *         of global scope or it is not a multicast address
 426      * @since 1.4
 427      */
 428     public boolean isMCGlobal() {
 429         return false;
 430     }
 431 
 432     /**
 433      * Utility routine to check if the multicast address has node scope.
 434      *
 435      * @return a {@code boolean} indicating if the address has
 436      *         is a multicast address of node-local scope, false if it is not
 437      *         of node-local scope or it is not a multicast address
 438      * @since 1.4
 439      */
 440     public boolean isMCNodeLocal() {
 441         return false;
 442     }
 443 
 444     /**
 445      * Utility routine to check if the multicast address has link scope.
 446      *
 447      * @return a {@code boolean} indicating if the address has
 448      *         is a multicast address of link-local scope, false if it is not
 449      *         of link-local scope or it is not a multicast address
 450      * @since 1.4
 451      */
 452     public boolean isMCLinkLocal() {
 453         return false;
 454     }
 455 
 456     /**
 457      * Utility routine to check if the multicast address has site scope.
 458      *
 459      * @return a {@code boolean} indicating if the address has
 460      *         is a multicast address of site-local scope, false if it is not
 461      *         of site-local scope or it is not a multicast address
 462      * @since 1.4
 463      */
 464     public boolean isMCSiteLocal() {
 465         return false;
 466     }
 467 
 468     /**
 469      * Utility routine to check if the multicast address has organization scope.
 470      *
 471      * @return a {@code boolean} indicating if the address has
 472      *         is a multicast address of organization-local scope,
 473      *         false if it is not of organization-local scope
 474      *         or it is not a multicast address
 475      * @since 1.4
 476      */
 477     public boolean isMCOrgLocal() {
 478         return false;
 479     }
 480 
 481 
 482     /**
 483      * Test whether that address is reachable. Best effort is made by the
 484      * implementation to try to reach the host, but firewalls and server
 485      * configuration may block requests resulting in a unreachable status
 486      * while some specific ports may be accessible.
 487      * A typical implementation will use ICMP ECHO REQUESTs if the
 488      * privilege can be obtained, otherwise it will try to establish
 489      * a TCP connection on port 7 (Echo) of the destination host.
 490      * <p>
 491      * The timeout value, in milliseconds, indicates the maximum amount of time
 492      * the try should take. If the operation times out before getting an
 493      * answer, the host is deemed unreachable. A negative value will result
 494      * in an IllegalArgumentException being thrown.
 495      *
 496      * @param   timeout the time, in milliseconds, before the call aborts
 497      * @return a {@code boolean} indicating if the address is reachable.
 498      * @throws IOException if a network error occurs
 499      * @throws  IllegalArgumentException if {@code timeout} is negative.
 500      * @since 1.5
 501      */
 502     public boolean isReachable(int timeout) throws IOException {
 503         return isReachable(null, 0 , timeout);
 504     }
 505 
 506     /**
 507      * Test whether that address is reachable. Best effort is made by the
 508      * implementation to try to reach the host, but firewalls and server
 509      * configuration may block requests resulting in a unreachable status
 510      * while some specific ports may be accessible.
 511      * A typical implementation will use ICMP ECHO REQUESTs if the
 512      * privilege can be obtained, otherwise it will try to establish
 513      * a TCP connection on port 7 (Echo) of the destination host.
 514      * <p>
 515      * The {@code network interface} and {@code ttl} parameters
 516      * let the caller specify which network interface the test will go through
 517      * and the maximum number of hops the packets should go through.
 518      * A negative value for the {@code ttl} will result in an
 519      * IllegalArgumentException being thrown.
 520      * <p>
 521      * The timeout value, in milliseconds, indicates the maximum amount of time
 522      * the try should take. If the operation times out before getting an
 523      * answer, the host is deemed unreachable. A negative value will result
 524      * in an IllegalArgumentException being thrown.
 525      *
 526      * @param   netif   the NetworkInterface through which the
 527      *                    test will be done, or null for any interface
 528      * @param   ttl     the maximum numbers of hops to try or 0 for the
 529      *                  default
 530      * @param   timeout the time, in milliseconds, before the call aborts
 531      * @throws  IllegalArgumentException if either {@code timeout}
 532      *                          or {@code ttl} are negative.
 533      * @return a {@code boolean}indicating if the address is reachable.
 534      * @throws IOException if a network error occurs
 535      * @since 1.5
 536      */
 537     public boolean isReachable(NetworkInterface netif, int ttl,
 538                                int timeout) throws IOException {
 539         if (ttl < 0)
 540             throw new IllegalArgumentException("ttl can't be negative");
 541         if (timeout < 0)
 542             throw new IllegalArgumentException("timeout can't be negative");
 543 
 544         return impl.isReachable(this, timeout, netif, ttl);
 545     }
 546 
 547     /**
 548      * Gets the host name for this IP address.
 549      *
 550      * <p>If this InetAddress was created with a host name,
 551      * this host name will be remembered and returned;
 552      * otherwise, a reverse name lookup will be performed
 553      * and the result will be returned based on the system
 554      * configured name lookup service. If a lookup of the name service
 555      * is required, call
 556      * {@link #getCanonicalHostName() getCanonicalHostName}.
 557      *
 558      * <p>If there is a security manager, its
 559      * {@code checkConnect} method is first called
 560      * with the hostname and {@code -1}
 561      * as its arguments to see if the operation is allowed.
 562      * If the operation is not allowed, it will return
 563      * the textual representation of the IP address.
 564      *
 565      * @return  the host name for this IP address, or if the operation
 566      *    is not allowed by the security check, the textual
 567      *    representation of the IP address.
 568      *
 569      * @see InetAddress#getCanonicalHostName
 570      * @see SecurityManager#checkConnect
 571      */
 572     public String getHostName() {
 573         return getHostName(true);
 574     }
 575 
 576     /**
 577      * Returns the hostname for this address.
 578      * If the host is equal to null, then this address refers to any
 579      * of the local machine's available network addresses.
 580      * this is package private so SocketPermission can make calls into
 581      * here without a security check.
 582      *
 583      * <p>If there is a security manager, this method first
 584      * calls its {@code checkConnect} method
 585      * with the hostname and {@code -1}
 586      * as its arguments to see if the calling code is allowed to know
 587      * the hostname for this IP address, i.e., to connect to the host.
 588      * If the operation is not allowed, it will return
 589      * the textual representation of the IP address.
 590      *
 591      * @return  the host name for this IP address, or if the operation
 592      *    is not allowed by the security check, the textual
 593      *    representation of the IP address.
 594      *
 595      * @param check make security check if true
 596      *
 597      * @see SecurityManager#checkConnect
 598      */
 599     String getHostName(boolean check) {
 600         if (holder().getHostName() == null) {
 601             holder().hostName = InetAddress.getHostFromNameService(this, check);
 602         }
 603         return holder().getHostName();
 604     }
 605 
 606     /**
 607      * Gets the fully qualified domain name for this IP address.
 608      * Best effort method, meaning we may not be able to return
 609      * the FQDN depending on the underlying system configuration.
 610      *
 611      * <p>If there is a security manager, this method first
 612      * calls its {@code checkConnect} method
 613      * with the hostname and {@code -1}
 614      * as its arguments to see if the calling code is allowed to know
 615      * the hostname for this IP address, i.e., to connect to the host.
 616      * If the operation is not allowed, it will return
 617      * the textual representation of the IP address.
 618      *
 619      * @return  the fully qualified domain name for this IP address,
 620      *    or if the operation is not allowed by the security check,
 621      *    the textual representation of the IP address.
 622      *
 623      * @see SecurityManager#checkConnect
 624      *
 625      * @since 1.4
 626      */
 627     public String getCanonicalHostName() {
 628         String value = canonicalHostName;
 629         if (value == null)
 630             canonicalHostName = value =
 631                 InetAddress.getHostFromNameService(this, true);
 632         return value;
 633     }
 634 
 635     /**
 636      * Returns the hostname for this address.
 637      *
 638      * <p>If there is a security manager, this method first
 639      * calls its {@code checkConnect} method
 640      * with the hostname and {@code -1}
 641      * as its arguments to see if the calling code is allowed to know
 642      * the hostname for this IP address, i.e., to connect to the host.
 643      * If the operation is not allowed, it will return
 644      * the textual representation of the IP address.
 645      *
 646      * @return  the host name for this IP address, or if the operation
 647      *    is not allowed by the security check, the textual
 648      *    representation of the IP address.
 649      *
 650      * @param check make security check if true
 651      *
 652      * @see SecurityManager#checkConnect
 653      */
 654     private static String getHostFromNameService(InetAddress addr, boolean check) {
 655         String host = null;
 656             try {
 657                 // first lookup the hostname
 658                 host = nameService.getHostByAddr(addr.getAddress());
 659 
 660                 /* check to see if calling code is allowed to know
 661                  * the hostname for this IP address, ie, connect to the host
 662                  */
 663                 if (check) {
 664                     SecurityManager sec = System.getSecurityManager();
 665                     if (sec != null) {
 666                         sec.checkConnect(host, -1);
 667                     }
 668                 }
 669 
 670                 /* now get all the IP addresses for this hostname,
 671                  * and make sure one of them matches the original IP
 672                  * address. We do this to try and prevent spoofing.
 673                  */
 674 
 675                 InetAddress[] arr = InetAddress.getAllByName0(host, check);
 676                 boolean ok = false;
 677 
 678                 if(arr != null) {
 679                     for(int i = 0; !ok && i < arr.length; i++) {
 680                         ok = addr.equals(arr[i]);
 681                     }
 682                 }
 683 
 684                 //XXX: if it looks a spoof just return the address?
 685                 if (!ok) {
 686                     host = addr.getHostAddress();
 687                     return host;
 688                 }
 689             } catch (SecurityException e) {
 690                 host = addr.getHostAddress();
 691             } catch (UnknownHostException e) {
 692                 host = addr.getHostAddress();
 693                 // let next provider resolve the hostname
 694             }
 695         return host;
 696     }
 697 
 698     /**
 699      * Returns the raw IP address of this {@code InetAddress}
 700      * object. The result is in network byte order: the highest order
 701      * byte of the address is in {@code getAddress()[0]}.
 702      *
 703      * @return  the raw IP address of this object.
 704      */
 705     public byte[] getAddress() {
 706         return null;
 707     }
 708 
 709     /**
 710      * Returns the IP address string in textual presentation.
 711      *
 712      * @return  the raw IP address in a string format.
 713      * @since   1.0.2
 714      */
 715     public String getHostAddress() {
 716         return null;
 717      }
 718 
 719     /**
 720      * Returns a hashcode for this IP address.
 721      *
 722      * @return  a hash code value for this IP address.
 723      */
 724     public int hashCode() {
 725         return -1;
 726     }
 727 
 728     /**
 729      * Compares this object against the specified object.
 730      * The result is {@code true} if and only if the argument is
 731      * not {@code null} and it represents the same IP address as
 732      * this object.
 733      * <p>
 734      * Two instances of {@code InetAddress} represent the same IP
 735      * address if the length of the byte arrays returned by
 736      * {@code getAddress} is the same for both, and each of the
 737      * array components is the same for the byte arrays.
 738      *
 739      * @param   obj   the object to compare against.
 740      * @return  {@code true} if the objects are the same;
 741      *          {@code false} otherwise.
 742      * @see     java.net.InetAddress#getAddress()
 743      */
 744     public boolean equals(Object obj) {
 745         return false;
 746     }
 747 
 748     /**
 749      * Converts this IP address to a {@code String}. The
 750      * string returned is of the form: hostname / literal IP
 751      * address.
 752      *
 753      * If the host name is unresolved, no reverse name service lookup
 754      * is performed. The hostname part will be represented by an empty string.
 755      *
 756      * @return  a string representation of this IP address.
 757      */
 758     public String toString() {
 759         String hostName = holder().getHostName();
 760         return Objects.toString(hostName, "")
 761             + "/" + getHostAddress();
 762     }
 763 
 764     // mapping from host name to Addresses - either NameServiceAddresses (while
 765     // still being looked-up by NameService(s)) or CachedAddresses when cached
 766     private static final ConcurrentMap<String, Addresses> cache =
 767         new ConcurrentHashMap<>();
 768 
 769     // CachedAddresses that have to expire are kept ordered in this NavigableSet
 770     // which is scanned on each access
 771     private static final NavigableSet<CachedAddresses> expirySet =
 772         new ConcurrentSkipListSet<>();
 773 
 774     // common interface
 775     private interface Addresses {
 776         InetAddress[] get() throws UnknownHostException;
 777     }
 778 
 779     // a holder for cached addresses with required metadata
 780     private static final class CachedAddresses  implements Addresses, Comparable<CachedAddresses> {
 781         private static final AtomicLong seq = new AtomicLong();
 782         final String host;
 783         final InetAddress[] inetAddresses;
 784         final long expiryTime; // time of expiry (in terms of System.nanoTime())
 785         final long id = seq.incrementAndGet(); // each instance is unique
 786 
 787         CachedAddresses(String host, InetAddress[] inetAddresses, long expiryTime) {
 788             this.host = host;
 789             this.inetAddresses = inetAddresses;
 790             this.expiryTime = expiryTime;
 791         }
 792 
 793         @Override
 794         public InetAddress[] get() throws UnknownHostException {
 795             if (inetAddresses == null) {
 796                 throw new UnknownHostException(host);
 797             }
 798             return inetAddresses;
 799         }
 800 
 801         @Override
 802         public int compareTo(CachedAddresses other) {
 803             // natural order is expiry time -
 804             // compare difference of expiry times rather than
 805             // expiry times directly, to avoid possible overflow.
 806             // (see System.nanoTime() recommendations...)
 807             long diff = this.expiryTime - other.expiryTime;
 808             if (diff < 0L) return -1;
 809             if (diff > 0L) return 1;
 810             // ties are broken using unique id
 811             return Long.compare(this.id, other.id);
 812         }
 813     }
 814 
 815     // a name service lookup based Addresses implementation which replaces itself
 816     // in cache when the result is obtained
 817     private static final class NameServiceAddresses implements Addresses {
 818         private final String host;
 819         private final InetAddress reqAddr;
 820 
 821         NameServiceAddresses(String host, InetAddress reqAddr) {
 822             this.host = host;
 823             this.reqAddr = reqAddr;
 824         }
 825 
 826         @Override
 827         public InetAddress[] get() throws UnknownHostException {
 828             Addresses addresses;
 829             // only one thread is doing lookup to name service
 830             // for particular host at any time.
 831             synchronized (this) {
 832                 // re-check that we are still us + re-install us if slot empty
 833                 addresses = cache.putIfAbsent(host, this);
 834                 if (addresses == null) {
 835                     // this can happen when we were replaced by CachedAddresses in
 836                     // some other thread, then CachedAddresses expired and were
 837                     // removed from cache while we were waiting for lock...
 838                     addresses = this;
 839                 }
 840                 // still us ?
 841                 if (addresses == this) {
 842                     // lookup name services
 843                     InetAddress[] inetAddresses;
 844                     UnknownHostException ex;
 845                     int cachePolicy;
 846                     try {
 847                         inetAddresses = getAddressesFromNameService(host, reqAddr);
 848                         ex = null;
 849                         cachePolicy = InetAddressCachePolicy.get();
 850                     } catch (UnknownHostException uhe) {
 851                         inetAddresses = null;
 852                         ex = uhe;
 853                         cachePolicy = InetAddressCachePolicy.getNegative();
 854                     }
 855                     // remove or replace us with cached addresses according to cachePolicy
 856                     if (cachePolicy == InetAddressCachePolicy.NEVER) {
 857                         cache.remove(host, this);
 858                     } else {
 859                         CachedAddresses cachedAddresses = new CachedAddresses(
 860                             host,
 861                             inetAddresses,
 862                             cachePolicy == InetAddressCachePolicy.FOREVER
 863                             ? 0L
 864                             // cachePolicy is in [s] - we need [ns]
 865                             : System.nanoTime() + 1000_000_000L * cachePolicy
 866                         );
 867                         if (cache.replace(host, this, cachedAddresses) &&
 868                             cachePolicy != InetAddressCachePolicy.FOREVER) {
 869                             // schedule expiry
 870                             expirySet.add(cachedAddresses);
 871                         }
 872                     }
 873                     if (inetAddresses == null) {
 874                         throw ex == null ? new UnknownHostException(host) : ex;
 875                     }
 876                     return inetAddresses;
 877                 }
 878                 // else addresses != this
 879             }
 880             // delegate to different addresses when we are already replaced
 881             // but outside of synchronized block to avoid any chance of dead-locking
 882             return addresses.get();
 883         }
 884     }
 885 
 886     /**
 887      * NameService provides host and address lookup service
 888      *
 889      * @since 9
 890      */
 891     private interface NameService {
 892 
 893         /**
 894          * Lookup a host mapping by name. Retrieve the IP addresses
 895          * associated with a host
 896          *
 897          * @param host the specified hostname
 898          * @return array of IP addresses for the requested host
 899          * @throws UnknownHostException
 900          *             if no IP address for the {@code host} could be found
 901          */
 902         InetAddress[] lookupAllHostAddr(String host)
 903                 throws UnknownHostException;
 904 
 905         /**
 906          * Lookup the host corresponding to the IP address provided
 907          *
 908          * @param addr byte array representing an IP address
 909          * @return {@code String} representing the host name mapping
 910          * @throws UnknownHostException
 911          *             if no host found for the specified IP address
 912          */
 913         String getHostByAddr(byte[] addr) throws UnknownHostException;
 914 
 915     }
 916 
 917     /**
 918      * The default NameService implementation, which delegates to the underlying
 919      * OS network libraries to resolve host address mappings.
 920      *
 921      * @since 9
 922      */
 923     private static final class PlatformNameService implements NameService {
 924 
 925         public InetAddress[] lookupAllHostAddr(String host)
 926             throws UnknownHostException
 927         {
 928             return impl.lookupAllHostAddr(host);
 929         }
 930 
 931         public String getHostByAddr(byte[] addr)
 932             throws UnknownHostException
 933         {
 934             return impl.getHostByAddr(addr);
 935         }
 936     }
 937 
 938     /**
 939      * The HostsFileNameService provides host address mapping
 940      * by reading the entries in a hosts file, which is specified by
 941      * {@code jdk.net.hosts.file} system property
 942      *
 943      * <p>The file format is that which corresponds with the /etc/hosts file
 944      * IP Address host alias list.
 945      *
 946      * <p>When the file lookup is enabled it replaces the default NameService
 947      * implementation
 948      *
 949      * @since 9
 950      */
 951     private static final class HostsFileNameService implements NameService {
 952 
 953         private final String hostsFile;
 954 
 955         public HostsFileNameService (String hostsFileName) {
 956             this.hostsFile = hostsFileName;
 957         }
 958 
 959         private  String addrToString(byte addr[]) {
 960           String stringifiedAddress = null;
 961 
 962             if (addr.length == Inet4Address.INADDRSZ) {
 963                 stringifiedAddress = Inet4Address.numericToTextFormat(addr);
 964             } else { // treat as an IPV6 jobby
 965                 byte[] newAddr
 966                     = IPAddressUtil.convertFromIPv4MappedAddress(addr);
 967                 if (newAddr != null) {
 968                    stringifiedAddress = Inet4Address.numericToTextFormat(addr);
 969                 } else {
 970                     stringifiedAddress = Inet6Address.numericToTextFormat(addr);
 971                 }
 972             }
 973             return stringifiedAddress;
 974         }
 975 
 976         /**
 977          * Lookup the host name  corresponding to the IP address provided.
 978          * Search the configured host file a host name corresponding to
 979          * the specified IP address.
 980          *
 981          * @param addr byte array representing an IP address
 982          * @return {@code String} representing the host name mapping
 983          * @throws UnknownHostException
 984          *             if no host found for the specified IP address
 985          */
 986         @Override
 987         public String getHostByAddr(byte[] addr) throws UnknownHostException {
 988             String hostEntry;
 989             String host = null;
 990 
 991             String addrString = addrToString(addr);
 992             try (Scanner hostsFileScanner = new Scanner(new File(hostsFile), "UTF-8")) {
 993                 while (hostsFileScanner.hasNextLine()) {
 994                     hostEntry = hostsFileScanner.nextLine();
 995                     if (!hostEntry.startsWith("#")) {
 996                         hostEntry = removeComments(hostEntry);
 997                         if (hostEntry.contains(addrString)) {
 998                             host = extractHost(hostEntry, addrString);
 999                             if (host != null) {
1000                                 break;
1001                             }
1002                         }
1003                     }
1004                 }
1005             } catch (FileNotFoundException e) {
1006                 throw new UnknownHostException("Unable to resolve address "
1007                         + addrString + " as hosts file " + hostsFile
1008                         + " not found ");
1009             }
1010 
1011             if ((host == null) || (host.equals("")) || (host.equals(" "))) {
1012                 throw new UnknownHostException("Requested address "
1013                         + addrString
1014                         + " resolves to an invalid entry in hosts file "
1015                         + hostsFile);
1016             }
1017             return host;
1018         }
1019 
1020         /**
1021          * <p>Lookup a host mapping by name. Retrieve the IP addresses
1022          * associated with a host.
1023          *
1024          * <p>Search the configured hosts file for the addresses assocaited with
1025          * with the specified host name.
1026          *
1027          * @param host the specified hostname
1028          * @return array of IP addresses for the requested host
1029          * @throws UnknownHostException
1030          *             if no IP address for the {@code host} could be found
1031          */
1032         public InetAddress[] lookupAllHostAddr(String host)
1033                 throws UnknownHostException {
1034             String hostEntry;
1035             String addrStr = null;
1036             InetAddress[] res = null;
1037             byte addr[] = new byte[4];
1038             ArrayList<InetAddress> inetAddresses = null;
1039 
1040             // lookup the file and create a list InetAddress for the specfied host
1041             try (Scanner hostsFileScanner = new Scanner(new File(hostsFile), "UTF-8")) {
1042                 while (hostsFileScanner.hasNextLine()) {
1043                     hostEntry = hostsFileScanner.nextLine();
1044                     if (!hostEntry.startsWith("#")) {
1045                         hostEntry = removeComments(hostEntry);
1046                         if (hostEntry.contains(host)) {
1047                             addrStr = extractHostAddr(hostEntry, host);
1048                             if ((addrStr != null) && (!addrStr.equals(""))) {
1049                                 addr = createAddressByteArray(addrStr);
1050                                 if (inetAddresses == null) {
1051                                     inetAddresses = new ArrayList<>(1);
1052                                 }
1053                                 if (addr != null) {
1054                                     inetAddresses.add(InetAddress.getByAddress(host, addr));
1055                                 }
1056                             }
1057                         }
1058                     }
1059                 }
1060             } catch (FileNotFoundException e) {
1061                 throw new UnknownHostException("Unable to resolve host " + host
1062                         + " as hosts file " + hostsFile + " not found ");
1063             }
1064 
1065             if (inetAddresses != null) {
1066                 res = inetAddresses.toArray(new InetAddress[inetAddresses.size()]);
1067             } else {
1068                 throw new UnknownHostException("Unable to resolve host " + host
1069                         + " in hosts file " + hostsFile);
1070             }
1071             return res;
1072         }
1073 
1074         private String removeComments(String hostsEntry) {
1075             String filteredEntry = hostsEntry;
1076             int hashIndex;
1077 
1078             if ((hashIndex = hostsEntry.indexOf("#")) != -1) {
1079                 filteredEntry = hostsEntry.substring(0, hashIndex);
1080             }
1081             return filteredEntry;
1082         }
1083 
1084         private byte [] createAddressByteArray(String addrStr) {
1085             byte[] addrArray;
1086             // check if IPV4 address - most likely
1087             addrArray = IPAddressUtil.textToNumericFormatV4(addrStr);
1088             if (addrArray == null) {
1089                 addrArray = IPAddressUtil.textToNumericFormatV6(addrStr);
1090             }
1091             return addrArray;
1092         }
1093 
1094         /** host to ip address mapping */
1095         private String extractHostAddr(String hostEntry, String host) {
1096             String[] mapping = hostEntry.split("\\s+");
1097             String hostAddr = null;
1098 
1099             if (mapping.length >= 2) {
1100                 // look at the host aliases
1101                 for (int i = 1; i < mapping.length; i++) {
1102                     if (mapping[i].equalsIgnoreCase(host)) {
1103                         hostAddr = mapping[0];
1104                     }
1105                 }
1106             }
1107             return hostAddr;
1108         }
1109 
1110         /**
1111          * IP Address to host mapping
1112          * use first host alias in list
1113          */
1114         private String extractHost(String hostEntry, String addrString) {
1115             String[] mapping = hostEntry.split("\\s+");
1116             String host = null;
1117 
1118             if (mapping.length >= 2) {
1119                 if (mapping[0].equalsIgnoreCase(addrString)) {
1120                     host = mapping[1];
1121                 }
1122             }
1123             return host;
1124         }
1125     }
1126 
1127     static final InetAddressImpl  impl;
1128 
1129     static {
1130         // create the impl
1131         impl = InetAddressImplFactory.create();
1132 
1133         // create name service
1134         nameService = createNameService();
1135         }
1136 
1137     /**
1138      * Create an instance of the NameService interface based on
1139      * the setting of the {@code jdk.net.hosts.file} system property.
1140      *
1141      * <p>The default NameService is the PlatformNameService, which typically
1142      * delegates name and address resolution calls to the underlying
1143      * OS network libraries.
1144      *
1145      * <p> A HostsFileNameService is created if the {@code jdk.net.hosts.file}
1146      * system property is set. If the specified file doesn't exist, the name or
1147      * address lookup will result in an UnknownHostException. Thus, non existent
1148      * hosts file is handled as if the file is empty.
1149      *
1150      * @return a NameService
1151      */
1152     private static NameService createNameService() {
1153 
1154         String hostsFileName =
1155                 GetPropertyAction.privilegedGetProperty("jdk.net.hosts.file");
1156         NameService theNameService;
1157         if (hostsFileName != null) {
1158             theNameService = new HostsFileNameService(hostsFileName);
1159         } else {
1160             theNameService = new PlatformNameService();
1161         }
1162         return theNameService;
1163     }
1164 
1165     /**
1166      * Creates an InetAddress based on the provided host name and IP address.
1167      * No name service is checked for the validity of the address.
1168      *
1169      * <p> The host name can either be a machine name, such as
1170      * "{@code java.sun.com}", or a textual representation of its IP
1171      * address.
1172      * <p> No validity checking is done on the host name either.
1173      *
1174      * <p> If addr specifies an IPv4 address an instance of Inet4Address
1175      * will be returned; otherwise, an instance of Inet6Address
1176      * will be returned.
1177      *
1178      * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
1179      * must be 16 bytes long
1180      *
1181      * @param host the specified host
1182      * @param addr the raw IP address in network byte order
1183      * @return  an InetAddress object created from the raw IP address.
1184      * @exception  UnknownHostException  if IP address is of illegal length
1185      * @since 1.4
1186      */
1187     public static InetAddress getByAddress(String host, byte[] addr)
1188         throws UnknownHostException {
1189         if (host != null && host.length() > 0 && host.charAt(0) == '[') {
1190             if (host.charAt(host.length()-1) == ']') {
1191                 host = host.substring(1, host.length() -1);
1192             }
1193         }
1194         if (addr != null) {
1195             if (addr.length == Inet4Address.INADDRSZ) {
1196                 return new Inet4Address(host, addr);
1197             } else if (addr.length == Inet6Address.INADDRSZ) {
1198                 byte[] newAddr
1199                     = IPAddressUtil.convertFromIPv4MappedAddress(addr);
1200                 if (newAddr != null) {
1201                     return new Inet4Address(host, newAddr);
1202                 } else {
1203                     return new Inet6Address(host, addr);
1204                 }
1205             }
1206         }
1207         throw new UnknownHostException("addr is of illegal length");
1208     }
1209 
1210 
1211     /**
1212      * Determines the IP address of a host, given the host's name.
1213      *
1214      * <p> The host name can either be a machine name, such as
1215      * "{@code java.sun.com}", or a textual representation of its
1216      * IP address. If a literal IP address is supplied, only the
1217      * validity of the address format is checked.
1218      *
1219      * <p> For {@code host} specified in literal IPv6 address,
1220      * either the form defined in RFC 2732 or the literal IPv6 address
1221      * format defined in RFC 2373 is accepted. IPv6 scoped addresses are also
1222      * supported. See <a href="Inet6Address.html#scoped">here</a> for a description of IPv6
1223      * scoped addresses.
1224      *
1225      * <p> If the host is {@code null} or {@code host.length()} is equal
1226      * to zero, then an {@code InetAddress} representing an address of the
1227      * loopback interface is returned.
1228      * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC&nbsp;3330</a>
1229      * section&nbsp;2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC&nbsp;2373</a>
1230      * section&nbsp;2.5.3.
1231      *
1232      * <p> If there is a security manager, and {@code host} is not {@code null}
1233      * or {@code host.length() } is not equal to zero, the security manager's
1234      * {@code checkConnect} method is called with the hostname and {@code -1}
1235      * as its arguments to determine if the operation is allowed.
1236      *
1237      * @param      host   the specified host, or {@code null}.
1238      * @return     an IP address for the given host name.
1239      * @exception  UnknownHostException  if no IP address for the
1240      *               {@code host} could be found, or if a scope_id was specified
1241      *               for a global IPv6 address.
1242      * @exception  SecurityException if a security manager exists
1243      *             and its checkConnect method doesn't allow the operation
1244      */
1245     public static InetAddress getByName(String host)
1246         throws UnknownHostException {
1247         return InetAddress.getAllByName(host)[0];
1248     }
1249 
1250     // called from deployment cache manager
1251     private static InetAddress getByName(String host, InetAddress reqAddr)
1252         throws UnknownHostException {
1253         return InetAddress.getAllByName(host, reqAddr)[0];
1254     }
1255 
1256     /**
1257      * Given the name of a host, returns an array of its IP addresses,
1258      * based on the configured name service on the system.
1259      *
1260      * <p> The host name can either be a machine name, such as
1261      * "{@code java.sun.com}", or a textual representation of its IP
1262      * address. If a literal IP address is supplied, only the
1263      * validity of the address format is checked.
1264      *
1265      * <p> For {@code host} specified in <i>literal IPv6 address</i>,
1266      * either the form defined in RFC 2732 or the literal IPv6 address
1267      * format defined in RFC 2373 is accepted. A literal IPv6 address may
1268      * also be qualified by appending a scoped zone identifier or scope_id.
1269      * The syntax and usage of scope_ids is described
1270      * <a href="Inet6Address.html#scoped">here</a>.
1271      *
1272      * <p> If the host is {@code null} or {@code host.length()} is equal
1273      * to zero, then an {@code InetAddress} representing an address of the
1274      * loopback interface is returned.
1275      * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC&nbsp;3330</a>
1276      * section&nbsp;2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC&nbsp;2373</a>
1277      * section&nbsp;2.5.3. </p>
1278      *
1279      * <p> If there is a security manager, and {@code host} is not {@code null}
1280      * or {@code host.length() } is not equal to zero, the security manager's
1281      * {@code checkConnect} method is called with the hostname and {@code -1}
1282      * as its arguments to determine if the operation is allowed.
1283      *
1284      * @param      host   the name of the host, or {@code null}.
1285      * @return     an array of all the IP addresses for a given host name.
1286      *
1287      * @exception  UnknownHostException  if no IP address for the
1288      *               {@code host} could be found, or if a scope_id was specified
1289      *               for a global IPv6 address.
1290      * @exception  SecurityException  if a security manager exists and its
1291      *               {@code checkConnect} method doesn't allow the operation.
1292      *
1293      * @see SecurityManager#checkConnect
1294      */
1295     public static InetAddress[] getAllByName(String host)
1296         throws UnknownHostException {
1297         return getAllByName(host, null);
1298     }
1299 
1300     private static InetAddress[] getAllByName(String host, InetAddress reqAddr)
1301         throws UnknownHostException {
1302 
1303         if (host == null || host.length() == 0) {
1304             InetAddress[] ret = new InetAddress[1];
1305             ret[0] = impl.loopbackAddress();
1306             return ret;
1307         }
1308 
1309         boolean ipv6Expected = false;
1310         if (host.charAt(0) == '[') {
1311             // This is supposed to be an IPv6 literal
1312             if (host.length() > 2 && host.charAt(host.length()-1) == ']') {
1313                 host = host.substring(1, host.length() -1);
1314                 ipv6Expected = true;
1315             } else {
1316                 // This was supposed to be a IPv6 address, but it's not!
1317                 throw new UnknownHostException(host + ": invalid IPv6 address");
1318             }
1319         }
1320 
1321         // if host is an IP address, we won't do further lookup
1322         if (Character.digit(host.charAt(0), 16) != -1
1323             || (host.charAt(0) == ':')) {
1324             byte[] addr = null;
1325             int numericZone = -1;
1326             String ifname = null;
1327             // see if it is IPv4 address
1328             addr = IPAddressUtil.textToNumericFormatV4(host);
1329             if (addr == null) {
1330                 // This is supposed to be an IPv6 literal
1331                 // Check if a numeric or string zone id is present
1332                 int pos;
1333                 if ((pos=host.indexOf ('%')) != -1) {
1334                     numericZone = checkNumericZone (host);
1335                     if (numericZone == -1) { /* remainder of string must be an ifname */
1336                         ifname = host.substring (pos+1);
1337                     }
1338                 }
1339                 if ((addr = IPAddressUtil.textToNumericFormatV6(host)) == null && host.contains(":")) {
1340                     throw new UnknownHostException(host + ": invalid IPv6 address");
1341                 }
1342             } else if (ipv6Expected) {
1343                 // Means an IPv4 litteral between brackets!
1344                 throw new UnknownHostException("["+host+"]");
1345             }
1346             InetAddress[] ret = new InetAddress[1];
1347             if(addr != null) {
1348                 if (addr.length == Inet4Address.INADDRSZ) {
1349                     ret[0] = new Inet4Address(null, addr);
1350                 } else {
1351                     if (ifname != null) {
1352                         ret[0] = new Inet6Address(null, addr, ifname);
1353                     } else {
1354                         ret[0] = new Inet6Address(null, addr, numericZone);
1355                     }
1356                 }
1357                 return ret;
1358             }
1359         } else if (ipv6Expected) {
1360             // We were expecting an IPv6 Litteral, but got something else
1361             throw new UnknownHostException("["+host+"]");
1362         }
1363         return getAllByName0(host, reqAddr, true, true);
1364     }
1365 
1366     /**
1367      * Returns the loopback address.
1368      * <p>
1369      * The InetAddress returned will represent the IPv4
1370      * loopback address, 127.0.0.1, or the IPv6 loopback
1371      * address, ::1. The IPv4 loopback address returned
1372      * is only one of many in the form 127.*.*.*
1373      *
1374      * @return  the InetAddress loopback instance.
1375      * @since 1.7
1376      */
1377     public static InetAddress getLoopbackAddress() {
1378         return impl.loopbackAddress();
1379     }
1380 
1381 
1382     /**
1383      * check if the literal address string has %nn appended
1384      * returns -1 if not, or the numeric value otherwise.
1385      *
1386      * %nn may also be a string that represents the displayName of
1387      * a currently available NetworkInterface.
1388      */
1389     private static int checkNumericZone (String s) throws UnknownHostException {
1390         int percent = s.indexOf ('%');
1391         int slen = s.length();
1392         int digit, zone=0;
1393         if (percent == -1) {
1394             return -1;
1395         }
1396         for (int i=percent+1; i<slen; i++) {
1397             char c = s.charAt(i);
1398             if (c == ']') {
1399                 if (i == percent+1) {
1400                     /* empty per-cent field */
1401                     return -1;
1402                 }
1403                 break;
1404             }
1405             if ((digit = Character.digit (c, 10)) < 0) {
1406                 return -1;
1407             }
1408             zone = (zone * 10) + digit;
1409         }
1410         return zone;
1411     }
1412 
1413     private static InetAddress[] getAllByName0 (String host)
1414         throws UnknownHostException
1415     {
1416         return getAllByName0(host, true);
1417     }
1418 
1419     /**
1420      * package private so SocketPermission can call it
1421      */
1422     static InetAddress[] getAllByName0 (String host, boolean check)
1423         throws UnknownHostException  {
1424         return getAllByName0 (host, null, check, true);
1425     }
1426 
1427     /**
1428      * Designated lookup method.
1429      *
1430      * @param host host name to look up
1431      * @param reqAddr requested address to be the 1st in returned array
1432      * @param check perform security check
1433      * @param useCache use cached value if not expired else always
1434      *                 perform name service lookup (and cache the result)
1435      * @return array of InetAddress(es)
1436      * @throws UnknownHostException if host name is not found
1437      */
1438     private static InetAddress[] getAllByName0(String host,
1439                                                InetAddress reqAddr,
1440                                                boolean check,
1441                                                boolean useCache)
1442         throws UnknownHostException  {
1443 
1444         /* If it gets here it is presumed to be a hostname */
1445 
1446         /* make sure the connection to the host is allowed, before we
1447          * give out a hostname
1448          */
1449         if (check) {
1450             SecurityManager security = System.getSecurityManager();
1451             if (security != null) {
1452                 security.checkConnect(host, -1);
1453             }
1454         }
1455 
1456         // remove expired addresses from cache - expirySet keeps them ordered
1457         // by expiry time so we only need to iterate the prefix of the NavigableSet...
1458         long now = System.nanoTime();
1459         for (CachedAddresses caddrs : expirySet) {
1460             // compare difference of time instants rather than
1461             // time instants directly, to avoid possible overflow.
1462             // (see System.nanoTime() recommendations...)
1463             if ((caddrs.expiryTime - now) < 0L) {
1464                 // ConcurrentSkipListSet uses weakly consistent iterator,
1465                 // so removing while iterating is OK...
1466                 if (expirySet.remove(caddrs)) {
1467                     // ... remove from cache
1468                     cache.remove(caddrs.host, caddrs);
1469                 }
1470             } else {
1471                 // we encountered 1st element that expires in future
1472                 break;
1473             }
1474         }
1475 
1476         // look-up or remove from cache
1477         Addresses addrs;
1478         if (useCache) {
1479             addrs = cache.get(host);
1480         } else {
1481             addrs = cache.remove(host);
1482             if (addrs != null) {
1483                 if (addrs instanceof CachedAddresses) {
1484                     // try removing from expirySet too if CachedAddresses
1485                     expirySet.remove(addrs);
1486                 }
1487                 addrs = null;
1488             }
1489         }
1490 
1491         if (addrs == null) {
1492             // create a NameServiceAddresses instance which will look up
1493             // the name service and install it within cache...
1494             Addresses oldAddrs = cache.putIfAbsent(
1495                 host,
1496                 addrs = new NameServiceAddresses(host, reqAddr)
1497             );
1498             if (oldAddrs != null) { // lost putIfAbsent race
1499                 addrs = oldAddrs;
1500             }
1501         }
1502 
1503         // ask Addresses to get an array of InetAddress(es) and clone it
1504         return addrs.get().clone();
1505     }
1506 
1507     static InetAddress[] getAddressesFromNameService(String host, InetAddress reqAddr)
1508         throws UnknownHostException
1509     {
1510         InetAddress[] addresses = null;
1511         UnknownHostException ex = null;
1512 
1513             try {
1514                 addresses = nameService.lookupAllHostAddr(host);
1515             } catch (UnknownHostException uhe) {
1516                 if (host.equalsIgnoreCase("localhost")) {
1517                     addresses = new InetAddress[] { impl.loopbackAddress() };
1518                 }
1519                 else {
1520                     ex = uhe;
1521                 }
1522             }
1523 
1524         if (addresses == null) {
1525             throw ex == null ? new UnknownHostException(host) : ex;
1526         }
1527 
1528         // More to do?
1529         if (reqAddr != null && addresses.length > 1 && !addresses[0].equals(reqAddr)) {
1530             // Find it?
1531             int i = 1;
1532             for (; i < addresses.length; i++) {
1533                 if (addresses[i].equals(reqAddr)) {
1534                     break;
1535                 }
1536             }
1537             // Rotate
1538             if (i < addresses.length) {
1539                 InetAddress tmp, tmp2 = reqAddr;
1540                 for (int j = 0; j < i; j++) {
1541                     tmp = addresses[j];
1542                     addresses[j] = tmp2;
1543                     tmp2 = tmp;
1544                 }
1545                 addresses[i] = tmp2;
1546             }
1547         }
1548 
1549         return addresses;
1550     }
1551 
1552     /**
1553      * Returns an {@code InetAddress} object given the raw IP address .
1554      * The argument is in network byte order: the highest order
1555      * byte of the address is in {@code getAddress()[0]}.
1556      *
1557      * <p> This method doesn't block, i.e. no reverse name service lookup
1558      * is performed.
1559      *
1560      * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
1561      * must be 16 bytes long
1562      *
1563      * @param addr the raw IP address in network byte order
1564      * @return  an InetAddress object created from the raw IP address.
1565      * @exception  UnknownHostException  if IP address is of illegal length
1566      * @since 1.4
1567      */
1568     public static InetAddress getByAddress(byte[] addr)
1569         throws UnknownHostException {
1570         return getByAddress(null, addr);
1571     }
1572 
1573     private static final class CachedLocalHost {
1574         final String host;
1575         final InetAddress addr;
1576         final long expiryTime = System.nanoTime() + 5000_000_000L; // now + 5s;
1577 
1578         CachedLocalHost(String host, InetAddress addr) {
1579             this.host = host;
1580             this.addr = addr;
1581         }
1582     }
1583 
1584     private static volatile CachedLocalHost cachedLocalHost;
1585 
1586     /**
1587      * Returns the address of the local host. This is achieved by retrieving
1588      * the name of the host from the system, then resolving that name into
1589      * an {@code InetAddress}.
1590      *
1591      * <P>Note: The resolved address may be cached for a short period of time.
1592      * </P>
1593      *
1594      * <p>If there is a security manager, its
1595      * {@code checkConnect} method is called
1596      * with the local host name and {@code -1}
1597      * as its arguments to see if the operation is allowed.
1598      * If the operation is not allowed, an InetAddress representing
1599      * the loopback address is returned.
1600      *
1601      * @return     the address of the local host.
1602      *
1603      * @exception  UnknownHostException  if the local host name could not
1604      *             be resolved into an address.
1605      *
1606      * @see SecurityManager#checkConnect
1607      * @see java.net.InetAddress#getByName(java.lang.String)
1608      */
1609     public static InetAddress getLocalHost() throws UnknownHostException {
1610 
1611         SecurityManager security = System.getSecurityManager();
1612         try {
1613             // is cached data still valid?
1614             CachedLocalHost clh = cachedLocalHost;
1615             if (clh != null && (clh.expiryTime - System.nanoTime()) >= 0L) {
1616                 if (security != null) {
1617                     security.checkConnect(clh.host, -1);
1618                 }
1619                 return clh.addr;
1620             }
1621 
1622             String local = impl.getLocalHostName();
1623 
1624             if (security != null) {
1625                 security.checkConnect(local, -1);
1626             }
1627 
1628             InetAddress localAddr;
1629             if (local.equals("localhost")) {
1630                 // shortcut for "localhost" host name
1631                 localAddr = impl.loopbackAddress();
1632             } else {
1633                 // call getAllByName0 without security checks and
1634                 // without using cached data
1635                 try {
1636                     localAddr = getAllByName0(local, null, false, false)[0];
1637                 } catch (UnknownHostException uhe) {
1638                     // Rethrow with a more informative error message.
1639                     UnknownHostException uhe2 =
1640                         new UnknownHostException(local + ": " +
1641                                                  uhe.getMessage());
1642                     uhe2.initCause(uhe);
1643                     throw uhe2;
1644                 }
1645             }
1646             cachedLocalHost = new CachedLocalHost(local, localAddr);
1647             return localAddr;
1648         } catch (java.lang.SecurityException e) {
1649             return impl.loopbackAddress();
1650         }
1651     }
1652 
1653     /**
1654      * Perform class load-time initializations.
1655      */
1656     private static native void init();
1657 
1658 
1659     /*
1660      * Returns the InetAddress representing anyLocalAddress
1661      * (typically 0.0.0.0 or ::0)
1662      */
1663     static InetAddress anyLocalAddress() {
1664         return impl.anyLocalAddress();
1665     }
1666 
1667     /*
1668      * Load and instantiate an underlying impl class
1669      */
1670     static InetAddressImpl loadImpl(String implName) {
1671         Object impl = null;
1672 
1673         /*
1674          * Property "impl.prefix" will be prepended to the classname
1675          * of the implementation object we instantiate, to which we
1676          * delegate the real work (like native methods).  This
1677          * property can vary across implementations of the java.
1678          * classes.  The default is an empty String "".
1679          */
1680         String prefix = GetPropertyAction.privilegedGetProperty("impl.prefix", "");
1681         try {
1682             @SuppressWarnings("deprecation")
1683             Object tmp = Class.forName("java.net." + prefix + implName).newInstance();
1684             impl = tmp;
1685         } catch (ClassNotFoundException e) {
1686             System.err.println("Class not found: java.net." + prefix +
1687                                implName + ":\ncheck impl.prefix property " +
1688                                "in your properties file.");
1689         } catch (InstantiationException e) {
1690             System.err.println("Could not instantiate: java.net." + prefix +
1691                                implName + ":\ncheck impl.prefix property " +
1692                                "in your properties file.");
1693         } catch (IllegalAccessException e) {
1694             System.err.println("Cannot access class: java.net." + prefix +
1695                                implName + ":\ncheck impl.prefix property " +
1696                                "in your properties file.");
1697         }
1698 
1699         if (impl == null) {
1700             try {
1701                 @SuppressWarnings("deprecation")
1702                 Object tmp = Class.forName(implName).newInstance();
1703                 impl = tmp;
1704             } catch (Exception e) {
1705                 throw new Error("System property impl.prefix incorrect");
1706             }
1707         }
1708 
1709         return (InetAddressImpl) impl;
1710     }
1711 
1712     private void readObjectNoData () {

1713         if (getClass().getClassLoader() != null) {
1714             throw new SecurityException ("invalid address type");
1715         }
1716     }
1717 
1718     private static final jdk.internal.misc.Unsafe UNSAFE
1719             = jdk.internal.misc.Unsafe.getUnsafe();
1720     private static final long FIELDS_OFFSET
1721             = UNSAFE.objectFieldOffset(InetAddress.class, "holder");
1722 
1723     private void readObject (ObjectInputStream s) throws
1724                          IOException, ClassNotFoundException {
1725         if (getClass().getClassLoader() != null) {
1726             throw new SecurityException ("invalid address type");
1727         }
1728         GetField gf = s.readFields();
1729         String host = (String)gf.get("hostName", null);
1730         int address= gf.get("address", 0);
1731         int family= gf.get("family", 0);
1732         InetAddressHolder h = new InetAddressHolder(host, address, family);
1733         UNSAFE.putObject(this, FIELDS_OFFSET, h);
1734     }
1735 
1736     /* needed because the serializable fields no longer exist */
1737 
1738     /**
1739      * @serialField hostName String
1740      * @serialField address int
1741      * @serialField family int
1742      */
1743     private static final ObjectStreamField[] serialPersistentFields = {
1744         new ObjectStreamField("hostName", String.class),
1745         new ObjectStreamField("address", int.class),
1746         new ObjectStreamField("family", int.class),
1747     };
1748 
1749     private void writeObject (ObjectOutputStream s) throws
1750                         IOException {
1751         if (getClass().getClassLoader() != null) {
1752             throw new SecurityException ("invalid address type");
1753         }
1754         PutField pf = s.putFields();
1755         pf.put("hostName", holder().getHostName());
1756         pf.put("address", holder().getAddress());
1757         pf.put("family", holder().getFamily());
1758         s.writeFields();
1759     }
1760 }
1761 
1762 /*
1763  * Simple factory to create the impl
1764  */
1765 class InetAddressImplFactory {
1766 
1767     static InetAddressImpl create() {
1768         return InetAddress.loadImpl(isIPv6Supported() ?
1769                                     "Inet6AddressImpl" : "Inet4AddressImpl");
1770     }
1771 
1772     static native boolean isIPv6Supported();
1773 }
--- EOF ---