1 /*
   2  * Copyright (c) 1995, 2010, 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.HashMap;
  29 import java.util.LinkedHashMap;
  30 import java.util.Random;
  31 import java.util.Iterator;
  32 import java.util.LinkedList;
  33 import java.util.List;
  34 import java.util.ArrayList;
  35 import java.security.AccessController;
  36 import java.io.ObjectStreamException;
  37 import java.io.IOException;
  38 import java.io.ObjectInputStream;
  39 import sun.security.action.*;
  40 import sun.net.InetAddressCachePolicy;
  41 import sun.net.util.IPAddressUtil;
  42 import sun.misc.Service;
  43 import sun.net.spi.nameservice.*;
  44 
  45 /**
  46  * This class represents an Internet Protocol (IP) address.
  47  *
  48  * <p> An IP address is either a 32-bit or 128-bit unsigned number
  49  * used by IP, a lower-level protocol on which protocols like UDP and
  50  * TCP are built. The IP address architecture is defined by <a
  51  * href="http://www.ietf.org/rfc/rfc790.txt"><i>RFC&nbsp;790:
  52  * Assigned Numbers</i></a>, <a
  53  * href="http://www.ietf.org/rfc/rfc1918.txt"> <i>RFC&nbsp;1918:
  54  * Address Allocation for Private Internets</i></a>, <a
  55  * href="http://www.ietf.org/rfc/rfc2365.txt"><i>RFC&nbsp;2365:
  56  * Administratively Scoped IP Multicast</i></a>, and <a
  57  * href="http://www.ietf.org/rfc/rfc2373.txt"><i>RFC&nbsp;2373: IP
  58  * Version 6 Addressing Architecture</i></a>. An instance of an
  59  * InetAddress consists of an IP address and possibly its
  60  * corresponding host name (depending on whether it is constructed
  61  * with a host name or whether it has already done reverse host name
  62  * resolution).
  63  *
  64  * <h4> Address types </h4>
  65  *
  66  * <blockquote><table cellspacing=2 summary="Description of unicast and multicast address types">
  67  *   <tr><th valign=top><i>unicast</i></th>
  68  *       <td>An identifier for a single interface. A packet sent to
  69  *         a unicast address is delivered to the interface identified by
  70  *         that address.
  71  *
  72  *         <p> The Unspecified Address -- Also called anylocal or wildcard
  73  *         address. It must never be assigned to any node. It indicates the
  74  *         absence of an address. One example of its use is as the target of
  75  *         bind, which allows a server to accept a client connection on any
  76  *         interface, in case the server host has multiple interfaces.
  77  *
  78  *         <p> The <i>unspecified</i> address must not be used as
  79  *         the destination address of an IP packet.
  80  *
  81  *         <p> The <i>Loopback</i> Addresses -- This is the address
  82  *         assigned to the loopback interface. Anything sent to this
  83  *         IP address loops around and becomes IP input on the local
  84  *         host. This address is often used when testing a
  85  *         client.</td></tr>
  86  *   <tr><th valign=top><i>multicast</i></th>
  87  *       <td>An identifier for a set of interfaces (typically belonging
  88  *         to different nodes). A packet sent to a multicast address is
  89  *         delivered to all interfaces identified by that address.</td></tr>
  90  * </table></blockquote>
  91  *
  92  * <h4> IP address scope </h4>
  93  *
  94  * <p> <i>Link-local</i> addresses are designed to be used for addressing
  95  * on a single link for purposes such as auto-address configuration,
  96  * neighbor discovery, or when no routers are present.
  97  *
  98  * <p> <i>Site-local</i> addresses are designed to be used for addressing
  99  * inside of a site without the need for a global prefix.
 100  *
 101  * <p> <i>Global</i> addresses are unique across the internet.
 102  *
 103  * <h4> Textual representation of IP addresses </h4>
 104  *
 105  * The textual representation of an IP address is address family specific.
 106  *
 107  * <p>
 108  *
 109  * For IPv4 address format, please refer to <A
 110  * HREF="Inet4Address.html#format">Inet4Address#format</A>; For IPv6
 111  * address format, please refer to <A
 112  * HREF="Inet6Address.html#format">Inet6Address#format</A>.
 113  *
 114  * <P>There is a <a href="doc-files/net-properties.html#Ipv4IPv6">couple of
 115  * System Properties</a> affecting how IPv4 and IPv6 addresses are used.</P>
 116  *
 117  * <h4> Host Name Resolution </h4>
 118  *
 119  * Host name-to-IP address <i>resolution</i> is accomplished through
 120  * the use of a combination of local machine configuration information
 121  * and network naming services such as the Domain Name System (DNS)
 122  * and Network Information Service(NIS). The particular naming
 123  * services(s) being used is by default the local machine configured
 124  * one. For any host name, its corresponding IP address is returned.
 125  *
 126  * <p> <i>Reverse name resolution</i> means that for any IP address,
 127  * the host associated with the IP address is returned.
 128  *
 129  * <p> The InetAddress class provides methods to resolve host names to
 130  * their IP addresses and vice versa.
 131  *
 132  * <h4> InetAddress Caching </h4>
 133  *
 134  * The InetAddress class has a cache to store successful as well as
 135  * unsuccessful host name resolutions.
 136  *
 137  * <p> By default, when a security manager is installed, in order to
 138  * protect against DNS spoofing attacks,
 139  * the result of positive host name resolutions are
 140  * cached forever. When a security manager is not installed, the default
 141  * behavior is to cache entries for a finite (implementation dependent)
 142  * period of time. The result of unsuccessful host
 143  * name resolution is cached for a very short period of time (10
 144  * seconds) to improve performance.
 145  *
 146  * <p> If the default behavior is not desired, then a Java security property
 147  * can be set to a different Time-to-live (TTL) value for positive
 148  * caching. Likewise, a system admin can configure a different
 149  * negative caching TTL value when needed.
 150  *
 151  * <p> Two Java security properties control the TTL values used for
 152  *  positive and negative host name resolution caching:
 153  *
 154  * <blockquote>
 155  * <dl>
 156  * <dt><b>networkaddress.cache.ttl</b></dt>
 157  * <dd>Indicates the caching policy for successful name lookups from
 158  * the name service. The value is specified as as integer to indicate
 159  * the number of seconds to cache the successful lookup. The default
 160  * setting is to cache for an implementation specific period of time.
 161  * <p>
 162  * A value of -1 indicates "cache forever".
 163  * </dd>
 164  * <p>
 165  * <dt><b>networkaddress.cache.negative.ttl</b> (default: 10)</dt>
 166  * <dd>Indicates the caching policy for un-successful name lookups
 167  * from the name service. The value is specified as as integer to
 168  * indicate the number of seconds to cache the failure for
 169  * un-successful lookups.
 170  * <p>
 171  * A value of 0 indicates "never cache".
 172  * A value of -1 indicates "cache forever".
 173  * </dd>
 174  * </dl>
 175  * </blockquote>
 176  *
 177  * @author  Chris Warth
 178  * @see     java.net.InetAddress#getByAddress(byte[])
 179  * @see     java.net.InetAddress#getByAddress(java.lang.String, byte[])
 180  * @see     java.net.InetAddress#getAllByName(java.lang.String)
 181  * @see     java.net.InetAddress#getByName(java.lang.String)
 182  * @see     java.net.InetAddress#getLocalHost()
 183  * @since JDK1.0
 184  */
 185 public
 186 class InetAddress implements java.io.Serializable {
 187     /**
 188      * Specify the address family: Internet Protocol, Version 4
 189      * @since 1.4
 190      */
 191     static final int IPv4 = 1;
 192 
 193     /**
 194      * Specify the address family: Internet Protocol, Version 6
 195      * @since 1.4
 196      */
 197     static final int IPv6 = 2;
 198 
 199     /* Specify address family preference */
 200     static transient boolean preferIPv6Address = false;
 201 
 202     /**
 203      * @serial
 204      */
 205     String hostName;
 206 
 207     /**
 208      * Holds a 32-bit IPv4 address.
 209      *
 210      * @serial
 211      */
 212     int address;
 213 
 214     /**
 215      * Specifies the address family type, for instance, '1' for IPv4
 216      * addresses, and '2' for IPv6 addresses.
 217      *
 218      * @serial
 219      */
 220     int family;
 221 
 222     /* Used to store the name service provider */
 223     private static List<NameService> nameServices = null;
 224 
 225     /* Used to store the best available hostname */
 226     private transient String canonicalHostName = null;
 227 
 228     /** use serialVersionUID from JDK 1.0.2 for interoperability */
 229     private static final long serialVersionUID = 3286316764910316507L;
 230 
 231     /*
 232      * Load net library into runtime, and perform initializations.
 233      */
 234     static {
 235         preferIPv6Address = java.security.AccessController.doPrivileged(
 236             new GetBooleanAction("java.net.preferIPv6Addresses")).booleanValue();
 237         AccessController.doPrivileged(new LoadLibraryAction("net"));
 238         init();
 239     }
 240 
 241     /**
 242      * Constructor for the Socket.accept() method.
 243      * This creates an empty InetAddress, which is filled in by
 244      * the accept() method.  This InetAddress, however, is not
 245      * put in the address cache, since it is not created by name.
 246      */
 247     InetAddress() {
 248     }
 249 
 250     /**
 251      * Replaces the de-serialized object with an Inet4Address object.
 252      *
 253      * @return the alternate object to the de-serialized object.
 254      *
 255      * @throws ObjectStreamException if a new object replacing this
 256      * object could not be created
 257      */
 258     private Object readResolve() throws ObjectStreamException {
 259         // will replace the deserialized 'this' object
 260         return new Inet4Address(this.hostName, this.address);
 261     }
 262 
 263     /**
 264      * Utility routine to check if the InetAddress is an
 265      * IP multicast address.
 266      * @return a <code>boolean</code> indicating if the InetAddress is
 267      * an IP multicast address
 268      * @since   JDK1.1
 269      */
 270     public boolean isMulticastAddress() {
 271         return false;
 272     }
 273 
 274     /**
 275      * Utility routine to check if the InetAddress in a wildcard address.
 276      * @return a <code>boolean</code> indicating if the Inetaddress is
 277      *         a wildcard address.
 278      * @since 1.4
 279      */
 280     public boolean isAnyLocalAddress() {
 281         return false;
 282     }
 283 
 284     /**
 285      * Utility routine to check if the InetAddress is a loopback address.
 286      *
 287      * @return a <code>boolean</code> indicating if the InetAddress is
 288      * a loopback address; or false otherwise.
 289      * @since 1.4
 290      */
 291     public boolean isLoopbackAddress() {
 292         return false;
 293     }
 294 
 295     /**
 296      * Utility routine to check if the InetAddress is an link local address.
 297      *
 298      * @return a <code>boolean</code> indicating if the InetAddress is
 299      * a link local address; or false if address is not a link local unicast address.
 300      * @since 1.4
 301      */
 302     public boolean isLinkLocalAddress() {
 303         return false;
 304     }
 305 
 306     /**
 307      * Utility routine to check if the InetAddress is a site local address.
 308      *
 309      * @return a <code>boolean</code> indicating if the InetAddress is
 310      * a site local address; or false if address is not a site local unicast address.
 311      * @since 1.4
 312      */
 313     public boolean isSiteLocalAddress() {
 314         return false;
 315     }
 316 
 317     /**
 318      * Utility routine to check if the multicast address has global scope.
 319      *
 320      * @return a <code>boolean</code> indicating if the address has
 321      *         is a multicast address of global scope, false if it is not
 322      *         of global scope or it is not a multicast address
 323      * @since 1.4
 324      */
 325     public boolean isMCGlobal() {
 326         return false;
 327     }
 328 
 329     /**
 330      * Utility routine to check if the multicast address has node scope.
 331      *
 332      * @return a <code>boolean</code> indicating if the address has
 333      *         is a multicast address of node-local scope, false if it is not
 334      *         of node-local scope or it is not a multicast address
 335      * @since 1.4
 336      */
 337     public boolean isMCNodeLocal() {
 338         return false;
 339     }
 340 
 341     /**
 342      * Utility routine to check if the multicast address has link scope.
 343      *
 344      * @return a <code>boolean</code> indicating if the address has
 345      *         is a multicast address of link-local scope, false if it is not
 346      *         of link-local scope or it is not a multicast address
 347      * @since 1.4
 348      */
 349     public boolean isMCLinkLocal() {
 350         return false;
 351     }
 352 
 353     /**
 354      * Utility routine to check if the multicast address has site scope.
 355      *
 356      * @return a <code>boolean</code> indicating if the address has
 357      *         is a multicast address of site-local scope, false if it is not
 358      *         of site-local scope or it is not a multicast address
 359      * @since 1.4
 360      */
 361     public boolean isMCSiteLocal() {
 362         return false;
 363     }
 364 
 365     /**
 366      * Utility routine to check if the multicast address has organization scope.
 367      *
 368      * @return a <code>boolean</code> indicating if the address has
 369      *         is a multicast address of organization-local scope,
 370      *         false if it is not of organization-local scope
 371      *         or it is not a multicast address
 372      * @since 1.4
 373      */
 374     public boolean isMCOrgLocal() {
 375         return false;
 376     }
 377 
 378 
 379     /**
 380      * Test whether that address is reachable. Best effort is made by the
 381      * implementation to try to reach the host, but firewalls and server
 382      * configuration may block requests resulting in a unreachable status
 383      * while some specific ports may be accessible.
 384      * A typical implementation will use ICMP ECHO REQUESTs if the
 385      * privilege can be obtained, otherwise it will try to establish
 386      * a TCP connection on port 7 (Echo) of the destination host.
 387      * <p>
 388      * The timeout value, in milliseconds, indicates the maximum amount of time
 389      * the try should take. If the operation times out before getting an
 390      * answer, the host is deemed unreachable. A negative value will result
 391      * in an IllegalArgumentException being thrown.
 392      *
 393      * @param   timeout the time, in milliseconds, before the call aborts
 394      * @return a <code>boolean</code> indicating if the address is reachable.
 395      * @throws IOException if a network error occurs
 396      * @throws  IllegalArgumentException if <code>timeout</code> is negative.
 397      * @since 1.5
 398      */
 399     public boolean isReachable(int timeout) throws IOException {
 400         return isReachable(null, 0 , timeout);
 401     }
 402 
 403     /**
 404      * Test whether that address is reachable. Best effort is made by the
 405      * implementation to try to reach the host, but firewalls and server
 406      * configuration may block requests resulting in a unreachable status
 407      * while some specific ports may be accessible.
 408      * A typical implementation will use ICMP ECHO REQUESTs if the
 409      * privilege can be obtained, otherwise it will try to establish
 410      * a TCP connection on port 7 (Echo) of the destination host.
 411      * <p>
 412      * The <code>network interface</code> and <code>ttl</code> parameters
 413      * let the caller specify which network interface the test will go through
 414      * and the maximum number of hops the packets should go through.
 415      * A negative value for the <code>ttl</code> will result in an
 416      * IllegalArgumentException being thrown.
 417      * <p>
 418      * The timeout value, in milliseconds, indicates the maximum amount of time
 419      * the try should take. If the operation times out before getting an
 420      * answer, the host is deemed unreachable. A negative value will result
 421      * in an IllegalArgumentException being thrown.
 422      *
 423      * @param   netif   the NetworkInterface through which the
 424      *                    test will be done, or null for any interface
 425      * @param   ttl     the maximum numbers of hops to try or 0 for the
 426      *                  default
 427      * @param   timeout the time, in milliseconds, before the call aborts
 428      * @throws  IllegalArgumentException if either <code>timeout</code>
 429      *                          or <code>ttl</code> are negative.
 430      * @return a <code>boolean</code>indicating if the address is reachable.
 431      * @throws IOException if a network error occurs
 432      * @since 1.5
 433      */
 434     public boolean isReachable(NetworkInterface netif, int ttl,
 435                                int timeout) throws IOException {
 436         if (ttl < 0)
 437             throw new IllegalArgumentException("ttl can't be negative");
 438         if (timeout < 0)
 439             throw new IllegalArgumentException("timeout can't be negative");
 440 
 441         return impl.isReachable(this, timeout, netif, ttl);
 442     }
 443 
 444     /**
 445      * Gets the host name for this IP address.
 446      *
 447      * <p>If this InetAddress was created with a host name,
 448      * this host name will be remembered and returned;
 449      * otherwise, a reverse name lookup will be performed
 450      * and the result will be returned based on the system
 451      * configured name lookup service. If a lookup of the name service
 452      * is required, call
 453      * {@link #getCanonicalHostName() getCanonicalHostName}.
 454      *
 455      * <p>If there is a security manager, its
 456      * <code>checkConnect</code> method is first called
 457      * with the hostname and <code>-1</code>
 458      * as its arguments to see if the operation is allowed.
 459      * If the operation is not allowed, it will return
 460      * the textual representation of the IP address.
 461      *
 462      * @return  the host name for this IP address, or if the operation
 463      *    is not allowed by the security check, the textual
 464      *    representation of the IP address.
 465      *
 466      * @see InetAddress#getCanonicalHostName
 467      * @see SecurityManager#checkConnect
 468      */
 469     public String getHostName() {
 470         return getHostName(true);
 471     }
 472 
 473     /**
 474      * Returns the hostname for this address.
 475      * If the host is equal to null, then this address refers to any
 476      * of the local machine's available network addresses.
 477      * this is package private so SocketPermission can make calls into
 478      * here without a security check.
 479      *
 480      * <p>If there is a security manager, this method first
 481      * calls its <code>checkConnect</code> method
 482      * with the hostname and <code>-1</code>
 483      * as its arguments to see if the calling code is allowed to know
 484      * the hostname for this IP address, i.e., to connect to the host.
 485      * If the operation is not allowed, it will return
 486      * the textual representation of the IP address.
 487      *
 488      * @return  the host name for this IP address, or if the operation
 489      *    is not allowed by the security check, the textual
 490      *    representation of the IP address.
 491      *
 492      * @param check make security check if true
 493      *
 494      * @see SecurityManager#checkConnect
 495      */
 496     String getHostName(boolean check) {
 497         if (hostName == null) {
 498             hostName = InetAddress.getHostFromNameService(this, check);
 499         }
 500         return hostName;
 501     }
 502 
 503     /**
 504      * Gets the fully qualified domain name for this IP address.
 505      * Best effort method, meaning we may not be able to return
 506      * the FQDN depending on the underlying system configuration.
 507      *
 508      * <p>If there is a security manager, this method first
 509      * calls its <code>checkConnect</code> method
 510      * with the hostname and <code>-1</code>
 511      * as its arguments to see if the calling code is allowed to know
 512      * the hostname for this IP address, i.e., to connect to the host.
 513      * If the operation is not allowed, it will return
 514      * the textual representation of the IP address.
 515      *
 516      * @return  the fully qualified domain name for this IP address,
 517      *    or if the operation is not allowed by the security check,
 518      *    the textual representation of the IP address.
 519      *
 520      * @see SecurityManager#checkConnect
 521      *
 522      * @since 1.4
 523      */
 524     public String getCanonicalHostName() {
 525         if (canonicalHostName == null) {
 526             canonicalHostName =
 527                 InetAddress.getHostFromNameService(this, true);
 528         }
 529         return canonicalHostName;
 530     }
 531 
 532     /**
 533      * Returns the hostname for this address.
 534      *
 535      * <p>If there is a security manager, this method first
 536      * calls its <code>checkConnect</code> method
 537      * with the hostname and <code>-1</code>
 538      * as its arguments to see if the calling code is allowed to know
 539      * the hostname for this IP address, i.e., to connect to the host.
 540      * If the operation is not allowed, it will return
 541      * the textual representation of the IP address.
 542      *
 543      * @return  the host name for this IP address, or if the operation
 544      *    is not allowed by the security check, the textual
 545      *    representation of the IP address.
 546      *
 547      * @param check make security check if true
 548      *
 549      * @see SecurityManager#checkConnect
 550      */
 551     private static String getHostFromNameService(InetAddress addr, boolean check) {
 552         String host = null;
 553         for (NameService nameService : nameServices) {
 554             try {
 555                 // first lookup the hostname
 556                 host = nameService.getHostByAddr(addr.getAddress());
 557 
 558                 /* check to see if calling code is allowed to know
 559                  * the hostname for this IP address, ie, connect to the host
 560                  */
 561                 if (check) {
 562                     SecurityManager sec = System.getSecurityManager();
 563                     if (sec != null) {
 564                         sec.checkConnect(host, -1);
 565                     }
 566                 }
 567 
 568                 /* now get all the IP addresses for this hostname,
 569                  * and make sure one of them matches the original IP
 570                  * address. We do this to try and prevent spoofing.
 571                  */
 572 
 573                 InetAddress[] arr = InetAddress.getAllByName0(host, check);
 574                 boolean ok = false;
 575 
 576                 if(arr != null) {
 577                     for(int i = 0; !ok && i < arr.length; i++) {
 578                         ok = addr.equals(arr[i]);
 579                     }
 580                 }
 581 
 582                 //XXX: if it looks a spoof just return the address?
 583                 if (!ok) {
 584                     host = addr.getHostAddress();
 585                     return host;
 586                 }
 587 
 588                 break;
 589 
 590             } catch (SecurityException e) {
 591                 host = addr.getHostAddress();
 592                 break;
 593             } catch (UnknownHostException e) {
 594                 host = addr.getHostAddress();
 595                 // let next provider resolve the hostname
 596             }
 597         }
 598 
 599         return host;
 600     }
 601 
 602     /**
 603      * Returns the raw IP address of this <code>InetAddress</code>
 604      * object. The result is in network byte order: the highest order
 605      * byte of the address is in <code>getAddress()[0]</code>.
 606      *
 607      * @return  the raw IP address of this object.
 608      */
 609     public byte[] getAddress() {
 610         return null;
 611     }
 612 
 613     /**
 614      * Returns the IP address string in textual presentation.
 615      *
 616      * @return  the raw IP address in a string format.
 617      * @since   JDK1.0.2
 618      */
 619     public String getHostAddress() {
 620         return null;
 621      }
 622 
 623     /**
 624      * Returns a hashcode for this IP address.
 625      *
 626      * @return  a hash code value for this IP address.
 627      */
 628     public int hashCode() {
 629         return -1;
 630     }
 631 
 632     /**
 633      * Compares this object against the specified object.
 634      * The result is <code>true</code> if and only if the argument is
 635      * not <code>null</code> and it represents the same IP address as
 636      * this object.
 637      * <p>
 638      * Two instances of <code>InetAddress</code> represent the same IP
 639      * address if the length of the byte arrays returned by
 640      * <code>getAddress</code> is the same for both, and each of the
 641      * array components is the same for the byte arrays.
 642      *
 643      * @param   obj   the object to compare against.
 644      * @return  <code>true</code> if the objects are the same;
 645      *          <code>false</code> otherwise.
 646      * @see     java.net.InetAddress#getAddress()
 647      */
 648     public boolean equals(Object obj) {
 649         return false;
 650     }
 651 
 652     /**
 653      * Converts this IP address to a <code>String</code>. The
 654      * string returned is of the form: hostname / literal IP
 655      * address.
 656      *
 657      * If the host name is unresolved, no reverse name service lookup
 658      * is performed. The hostname part will be represented by an empty string.
 659      *
 660      * @return  a string representation of this IP address.
 661      */
 662     public String toString() {
 663         return ((hostName != null) ? hostName : "")
 664             + "/" + getHostAddress();
 665     }
 666 
 667     /*
 668      * Cached addresses - our own litle nis, not!
 669      */
 670     private static Cache addressCache = new Cache(Cache.Type.Positive);
 671 
 672     private static Cache negativeCache = new Cache(Cache.Type.Negative);
 673 
 674     private static boolean addressCacheInit = false;
 675 
 676     static InetAddress[]    unknown_array; // put THIS in cache
 677 
 678     static InetAddressImpl  impl;
 679 
 680     private static final HashMap<String, Void> lookupTable = new HashMap<>();
 681 
 682     /**
 683      * Represents a cache entry
 684      */
 685     static final class CacheEntry {
 686 
 687         CacheEntry(InetAddress[] addresses, long expiration) {
 688             this.addresses = addresses;
 689             this.expiration = expiration;
 690         }
 691 
 692         InetAddress[] addresses;
 693         long expiration;
 694     }
 695 
 696     /**
 697      * A cache that manages entries based on a policy specified
 698      * at creation time.
 699      */
 700     static final class Cache {
 701         private LinkedHashMap<String, CacheEntry> cache;
 702         private Type type;
 703 
 704         enum Type {Positive, Negative};
 705 
 706         /**
 707          * Create cache
 708          */
 709         public Cache(Type type) {
 710             this.type = type;
 711             cache = new LinkedHashMap<String, CacheEntry>();
 712         }
 713 
 714         private int getPolicy() {
 715             if (type == Type.Positive) {
 716                 return InetAddressCachePolicy.get();
 717             } else {
 718                 return InetAddressCachePolicy.getNegative();
 719             }
 720         }
 721 
 722         /**
 723          * Add an entry to the cache. If there's already an
 724          * entry then for this host then the entry will be
 725          * replaced.
 726          */
 727         public Cache put(String host, InetAddress[] addresses) {
 728             int policy = getPolicy();
 729             if (policy == InetAddressCachePolicy.NEVER) {
 730                 return this;
 731             }
 732 
 733             // purge any expired entries
 734 
 735             if (policy != InetAddressCachePolicy.FOREVER) {
 736 
 737                 // As we iterate in insertion order we can
 738                 // terminate when a non-expired entry is found.
 739                 LinkedList<String> expired = new LinkedList<>();
 740                 long now = System.currentTimeMillis();
 741                 for (String key : cache.keySet()) {
 742                     CacheEntry entry = cache.get(key);
 743 
 744                     if (entry.expiration >= 0 && entry.expiration < now) {
 745                         expired.add(key);
 746                     } else {
 747                         break;
 748                     }
 749                 }
 750 
 751                 for (String key : expired) {
 752                     cache.remove(key);
 753                 }
 754             }
 755 
 756             // create new entry and add it to the cache
 757             // -- as a HashMap replaces existing entries we
 758             //    don't need to explicitly check if there is
 759             //    already an entry for this host.
 760             long expiration;
 761             if (policy == InetAddressCachePolicy.FOREVER) {
 762                 expiration = -1;
 763             } else {
 764                 expiration = System.currentTimeMillis() + (policy * 1000);
 765             }
 766             CacheEntry entry = new CacheEntry(addresses, expiration);
 767             cache.put(host, entry);
 768             return this;
 769         }
 770 
 771         /**
 772          * Query the cache for the specific host. If found then
 773          * return its CacheEntry, or null if not found.
 774          */
 775         public CacheEntry get(String host) {
 776             int policy = getPolicy();
 777             if (policy == InetAddressCachePolicy.NEVER) {
 778                 return null;
 779             }
 780             CacheEntry entry = cache.get(host);
 781 
 782             // check if entry has expired
 783             if (entry != null && policy != InetAddressCachePolicy.FOREVER) {
 784                 if (entry.expiration >= 0 &&
 785                     entry.expiration < System.currentTimeMillis()) {
 786                     cache.remove(host);
 787                     entry = null;
 788                 }
 789             }
 790 
 791             return entry;
 792         }
 793     }
 794 
 795     /*
 796      * Initialize cache and insert anyLocalAddress into the
 797      * unknown array with no expiry.
 798      */
 799     private static void cacheInitIfNeeded() {
 800         assert Thread.holdsLock(addressCache);
 801         if (addressCacheInit) {
 802             return;
 803         }
 804         unknown_array = new InetAddress[1];
 805         unknown_array[0] = impl.anyLocalAddress();
 806 
 807         addressCache.put(impl.anyLocalAddress().getHostName(),
 808                          unknown_array);
 809 
 810         addressCacheInit = true;
 811     }
 812 
 813     /*
 814      * Cache the given hostname and addresses.
 815      */
 816     private static void cacheAddresses(String hostname,
 817                                        InetAddress[] addresses,
 818                                        boolean success) {
 819         hostname = hostname.toLowerCase();
 820         synchronized (addressCache) {
 821             cacheInitIfNeeded();
 822             if (success) {
 823                 addressCache.put(hostname, addresses);
 824             } else {
 825                 negativeCache.put(hostname, addresses);
 826             }
 827         }
 828     }
 829 
 830     /*
 831      * Lookup hostname in cache (positive & negative cache). If
 832      * found return addresses, null if not found.
 833      */
 834     private static InetAddress[] getCachedAddresses(String hostname) {
 835         hostname = hostname.toLowerCase();
 836 
 837         // search both positive & negative caches
 838 
 839         synchronized (addressCache) {
 840             cacheInitIfNeeded();
 841 
 842             CacheEntry entry = addressCache.get(hostname);
 843             if (entry == null) {
 844                 entry = negativeCache.get(hostname);
 845             }
 846 
 847             if (entry != null) {
 848                 return entry.addresses;
 849             }
 850         }
 851 
 852         // not found
 853         return null;
 854     }
 855 
 856     private static NameService createNSProvider(String provider) {
 857         if (provider == null)
 858             return null;
 859 
 860         NameService nameService = null;
 861         if (provider.equals("default")) {
 862             // initialize the default name service
 863             nameService = new NameService() {
 864                 public InetAddress[] lookupAllHostAddr(String host)
 865                     throws UnknownHostException {
 866                     return impl.lookupAllHostAddr(host);
 867                 }
 868                 public String getHostByAddr(byte[] addr)
 869                     throws UnknownHostException {
 870                     return impl.getHostByAddr(addr);
 871                 }
 872             };
 873         } else {
 874             final String providerName = provider;
 875             try {
 876                 nameService = java.security.AccessController.doPrivileged(
 877                     new java.security.PrivilegedExceptionAction<NameService>() {
 878                         public NameService run() {
 879                             Iterator itr = Service.providers(NameServiceDescriptor.class);
 880                             while (itr.hasNext()) {
 881                                 NameServiceDescriptor nsd
 882                                     = (NameServiceDescriptor)itr.next();
 883                                 if (providerName.
 884                                     equalsIgnoreCase(nsd.getType()+","
 885                                         +nsd.getProviderName())) {
 886                                     try {
 887                                         return nsd.createNameService();
 888                                     } catch (Exception e) {
 889                                         e.printStackTrace();
 890                                         System.err.println(
 891                                             "Cannot create name service:"
 892                                              +providerName+": " + e);
 893                                     }
 894                                 }
 895                             }
 896 
 897                             return null;
 898                         }
 899                     }
 900                 );
 901             } catch (java.security.PrivilegedActionException e) {
 902             }
 903         }
 904 
 905         return nameService;
 906     }
 907 
 908     static {
 909         // create the impl
 910         impl = InetAddressImplFactory.create();
 911 
 912         // get name service if provided and requested
 913         String provider = null;;
 914         String propPrefix = "sun.net.spi.nameservice.provider.";
 915         int n = 1;
 916         nameServices = new ArrayList<NameService>();
 917         provider = AccessController.doPrivileged(
 918                 new GetPropertyAction(propPrefix + n));
 919         while (provider != null) {
 920             NameService ns = createNSProvider(provider);
 921             if (ns != null)
 922                 nameServices.add(ns);
 923 
 924             n++;
 925             provider = AccessController.doPrivileged(
 926                     new GetPropertyAction(propPrefix + n));
 927         }
 928 
 929         // if not designate any name services provider,
 930         // create a default one
 931         if (nameServices.size() == 0) {
 932             NameService ns = createNSProvider("default");
 933             nameServices.add(ns);
 934         }
 935     }
 936 
 937     /**
 938      * Creates an InetAddress based on the provided host name and IP address.
 939      * No name service is checked for the validity of the address.
 940      *
 941      * <p> The host name can either be a machine name, such as
 942      * "<code>java.sun.com</code>", or a textual representation of its IP
 943      * address.
 944      * <p> No validity checking is done on the host name either.
 945      *
 946      * <p> If addr specifies an IPv4 address an instance of Inet4Address
 947      * will be returned; otherwise, an instance of Inet6Address
 948      * will be returned.
 949      *
 950      * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
 951      * must be 16 bytes long
 952      *
 953      * @param host the specified host
 954      * @param addr the raw IP address in network byte order
 955      * @return  an InetAddress object created from the raw IP address.
 956      * @exception  UnknownHostException  if IP address is of illegal length
 957      * @since 1.4
 958      */
 959     public static InetAddress getByAddress(String host, byte[] addr)
 960         throws UnknownHostException {
 961         if (host != null && host.length() > 0 && host.charAt(0) == '[') {
 962             if (host.charAt(host.length()-1) == ']') {
 963                 host = host.substring(1, host.length() -1);
 964             }
 965         }
 966         if (addr != null) {
 967             if (addr.length == Inet4Address.INADDRSZ) {
 968                 return new Inet4Address(host, addr);
 969             } else if (addr.length == Inet6Address.INADDRSZ) {
 970                 byte[] newAddr
 971                     = IPAddressUtil.convertFromIPv4MappedAddress(addr);
 972                 if (newAddr != null) {
 973                     return new Inet4Address(host, newAddr);
 974                 } else {
 975                     return new Inet6Address(host, addr);
 976                 }
 977             }
 978         }
 979         throw new UnknownHostException("addr is of illegal length");
 980     }
 981 
 982 
 983     /**
 984      * Determines the IP address of a host, given the host's name.
 985      *
 986      * <p> The host name can either be a machine name, such as
 987      * "<code>java.sun.com</code>", or a textual representation of its
 988      * IP address. If a literal IP address is supplied, only the
 989      * validity of the address format is checked.
 990      *
 991      * <p> For <code>host</code> specified in literal IPv6 address,
 992      * either the form defined in RFC 2732 or the literal IPv6 address
 993      * format defined in RFC 2373 is accepted. IPv6 scoped addresses are also
 994      * supported. See <a href="Inet6Address.html#scoped">here</a> for a description of IPv6
 995      * scoped addresses.
 996      *
 997      * <p> If the host is <tt>null</tt> then an <tt>InetAddress</tt>
 998      * representing an address of the loopback interface is returned.
 999      * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC&nbsp;3330</a>
1000      * section&nbsp;2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC&nbsp;2373</a>
1001      * section&nbsp;2.5.3. </p>
1002      *
1003      * @param      host   the specified host, or <code>null</code>.
1004      * @return     an IP address for the given host name.
1005      * @exception  UnknownHostException  if no IP address for the
1006      *               <code>host</code> could be found, or if a scope_id was specified
1007      *               for a global IPv6 address.
1008      * @exception  SecurityException if a security manager exists
1009      *             and its checkConnect method doesn't allow the operation
1010      */
1011     public static InetAddress getByName(String host)
1012         throws UnknownHostException {
1013         return InetAddress.getAllByName(host)[0];
1014     }
1015 
1016     /**
1017      * Given the name of a host, returns an array of its IP addresses,
1018      * based on the configured name service on the system.
1019      *
1020      * <p> The host name can either be a machine name, such as
1021      * "<code>java.sun.com</code>", or a textual representation of its IP
1022      * address. If a literal IP address is supplied, only the
1023      * validity of the address format is checked.
1024      *
1025      * <p> For <code>host</code> specified in <i>literal IPv6 address</i>,
1026      * either the form defined in RFC 2732 or the literal IPv6 address
1027      * format defined in RFC 2373 is accepted. A literal IPv6 address may
1028      * also be qualified by appending a scoped zone identifier or scope_id.
1029      * The syntax and usage of scope_ids is described
1030      * <a href="Inet6Address.html#scoped">here</a>.
1031      * <p> If the host is <tt>null</tt> then an <tt>InetAddress</tt>
1032      * representing an address of the loopback interface is returned.
1033      * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC&nbsp;3330</a>
1034      * section&nbsp;2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC&nbsp;2373</a>
1035      * section&nbsp;2.5.3. </p>
1036      *
1037      * <p> If there is a security manager and <code>host</code> is not
1038      * null and <code>host.length() </code> is not equal to zero, the
1039      * security manager's
1040      * <code>checkConnect</code> method is called
1041      * with the hostname and <code>-1</code>
1042      * as its arguments to see if the operation is allowed.
1043      *
1044      * @param      host   the name of the host, or <code>null</code>.
1045      * @return     an array of all the IP addresses for a given host name.
1046      *
1047      * @exception  UnknownHostException  if no IP address for the
1048      *               <code>host</code> could be found, or if a scope_id was specified
1049      *               for a global IPv6 address.
1050      * @exception  SecurityException  if a security manager exists and its
1051      *               <code>checkConnect</code> method doesn't allow the operation.
1052      *
1053      * @see SecurityManager#checkConnect
1054      */
1055     public static InetAddress[] getAllByName(String host)
1056         throws UnknownHostException {
1057 
1058         if (host == null || host.length() == 0) {
1059             InetAddress[] ret = new InetAddress[1];
1060             ret[0] = impl.loopbackAddress();
1061             return ret;
1062         }
1063 
1064         boolean ipv6Expected = false;
1065         if (host.charAt(0) == '[') {
1066             // This is supposed to be an IPv6 literal
1067             if (host.length() > 2 && host.charAt(host.length()-1) == ']') {
1068                 host = host.substring(1, host.length() -1);
1069                 ipv6Expected = true;
1070             } else {
1071                 // This was supposed to be a IPv6 address, but it's not!
1072                 throw new UnknownHostException(host + ": invalid IPv6 address");
1073             }
1074         }
1075 
1076         // if host is an IP address, we won't do further lookup
1077         if (Character.digit(host.charAt(0), 16) != -1
1078             || (host.charAt(0) == ':')) {
1079             byte[] addr = null;
1080             int numericZone = -1;
1081             String ifname = null;
1082             // see if it is IPv4 address
1083             addr = IPAddressUtil.textToNumericFormatV4(host);
1084             if (addr == null) {
1085                 // see if it is IPv6 address
1086                 // Check if a numeric or string zone id is present
1087                 int pos;
1088                 if ((pos=host.indexOf ("%")) != -1) {
1089                     numericZone = checkNumericZone (host);
1090                     if (numericZone == -1) { /* remainder of string must be an ifname */
1091                         ifname = host.substring (pos+1);
1092                     }
1093                 }
1094                 addr = IPAddressUtil.textToNumericFormatV6(host);
1095             } else if (ipv6Expected) {
1096                 // Means an IPv4 litteral between brackets!
1097                 throw new UnknownHostException("["+host+"]");
1098             }
1099             InetAddress[] ret = new InetAddress[1];
1100             if(addr != null) {
1101                 if (addr.length == Inet4Address.INADDRSZ) {
1102                     ret[0] = new Inet4Address(null, addr);
1103                 } else {
1104                     if (ifname != null) {
1105                         ret[0] = new Inet6Address(null, addr, ifname);
1106                     } else {
1107                         ret[0] = new Inet6Address(null, addr, numericZone);
1108                     }
1109                 }
1110                 return ret;
1111             }
1112             } else if (ipv6Expected) {
1113                 // We were expecting an IPv6 Litteral, but got something else
1114                 throw new UnknownHostException("["+host+"]");
1115             }
1116         return getAllByName0(host);
1117     }
1118 
1119     /**
1120      * Returns the loopback address.
1121      * <p>
1122      * The InetAddress returned will represent the IPv4
1123      * loopback address, 127.0.0.1, or the IPv6 loopback
1124      * address, ::1. The IPv4 loopback address returned
1125      * is only one of many in the form 127.*.*.*
1126      *
1127      * @return  the InetAddress loopback instance.
1128      * @since 1.7
1129      */
1130     public static InetAddress getLoopbackAddress() {
1131         return impl.loopbackAddress();
1132     }
1133 
1134 
1135     /**
1136      * check if the literal address string has %nn appended
1137      * returns -1 if not, or the numeric value otherwise.
1138      *
1139      * %nn may also be a string that represents the displayName of
1140      * a currently available NetworkInterface.
1141      */
1142     private static int checkNumericZone (String s) throws UnknownHostException {
1143         int percent = s.indexOf ('%');
1144         int slen = s.length();
1145         int digit, zone=0;
1146         if (percent == -1) {
1147             return -1;
1148         }
1149         for (int i=percent+1; i<slen; i++) {
1150             char c = s.charAt(i);
1151             if (c == ']') {
1152                 if (i == percent+1) {
1153                     /* empty per-cent field */
1154                     return -1;
1155                 }
1156                 break;
1157             }
1158             if ((digit = Character.digit (c, 10)) < 0) {
1159                 return -1;
1160             }
1161             zone = (zone * 10) + digit;
1162         }
1163         return zone;
1164     }
1165 
1166     private static InetAddress[] getAllByName0 (String host)
1167         throws UnknownHostException
1168     {
1169         return getAllByName0(host, true);
1170     }
1171 
1172     /**
1173      * package private so SocketPermission can call it
1174      */
1175     static InetAddress[] getAllByName0 (String host, boolean check)
1176         throws UnknownHostException  {
1177         /* If it gets here it is presumed to be a hostname */
1178         /* Cache.get can return: null, unknownAddress, or InetAddress[] */
1179 
1180         /* make sure the connection to the host is allowed, before we
1181          * give out a hostname
1182          */
1183         if (check) {
1184             SecurityManager security = System.getSecurityManager();
1185             if (security != null) {
1186                 security.checkConnect(host, -1);
1187             }
1188         }
1189 
1190         InetAddress[] addresses = getCachedAddresses(host);
1191 
1192         /* If no entry in cache, then do the host lookup */
1193         if (addresses == null) {
1194             addresses = getAddressesFromNameService(host);
1195         }
1196 
1197         if (addresses == unknown_array)
1198             throw new UnknownHostException(host);
1199 
1200         return addresses.clone();
1201     }
1202 
1203     private static InetAddress[] getAddressesFromNameService(String host)
1204         throws UnknownHostException
1205     {
1206         InetAddress[] addresses = null;
1207         boolean success = false;
1208         UnknownHostException ex = null;
1209 
1210         // Check whether the host is in the lookupTable.
1211         // 1) If the host isn't in the lookupTable when
1212         //    checkLookupTable() is called, checkLookupTable()
1213         //    would add the host in the lookupTable and
1214         //    return null. So we will do the lookup.
1215         // 2) If the host is in the lookupTable when
1216         //    checkLookupTable() is called, the current thread
1217         //    would be blocked until the host is removed
1218         //    from the lookupTable. Then this thread
1219         //    should try to look up the addressCache.
1220         //     i) if it found the addresses in the
1221         //        addressCache, checkLookupTable()  would
1222         //        return the addresses.
1223         //     ii) if it didn't find the addresses in the
1224         //         addressCache for any reason,
1225         //         it should add the host in the
1226         //         lookupTable and return null so the
1227         //         following code would do  a lookup itself.
1228         if ((addresses = checkLookupTable(host)) == null) {
1229             try {
1230                 // This is the first thread which looks up the addresses
1231                 // this host or the cache entry for this host has been
1232                 // expired so this thread should do the lookup.
1233                 for (NameService nameService : nameServices) {
1234                     try {
1235                         /*
1236                          * Do not put the call to lookup() inside the
1237                          * constructor.  if you do you will still be
1238                          * allocating space when the lookup fails.
1239                          */
1240 
1241                         addresses = nameService.lookupAllHostAddr(host);
1242                         success = true;
1243                         break;
1244                     } catch (UnknownHostException uhe) {
1245                         if (host.equalsIgnoreCase("localhost")) {
1246                             InetAddress[] local = new InetAddress[] { impl.loopbackAddress() };
1247                             addresses = local;
1248                             success = true;
1249                             break;
1250                         }
1251                         else {
1252                             addresses = unknown_array;
1253                             success = false;
1254                             ex = uhe;
1255                         }
1256                     }
1257                 }
1258 
1259                 // Cache the addresses.
1260                 cacheAddresses(host, addresses, success);
1261                 if (!success && ex != null)
1262                     throw ex;
1263             } finally {
1264                 // Delete host from the lookupTable and notify
1265                 // all threads waiting on the lookupTable monitor.
1266                 updateLookupTable(host);
1267             }
1268         }
1269 
1270         return addresses;
1271     }
1272 
1273 
1274     private static InetAddress[] checkLookupTable(String host) {
1275         synchronized (lookupTable) {
1276             // If the host isn't in the lookupTable, add it in the
1277             // lookuptable and return null. The caller should do
1278             // the lookup.
1279             if (lookupTable.containsKey(host) == false) {
1280                 lookupTable.put(host, null);
1281                 return null;
1282             }
1283 
1284             // If the host is in the lookupTable, it means that another
1285             // thread is trying to look up the addresses of this host.
1286             // This thread should wait.
1287             while (lookupTable.containsKey(host)) {
1288                 try {
1289                     lookupTable.wait();
1290                 } catch (InterruptedException e) {
1291                 }
1292             }
1293         }
1294 
1295         // The other thread has finished looking up the addresses of
1296         // the host. This thread should retry to get the addresses
1297         // from the addressCache. If it doesn't get the addresses from
1298         // the cache, it will try to look up the addresses itself.
1299         InetAddress[] addresses = getCachedAddresses(host);
1300         if (addresses == null) {
1301             synchronized (lookupTable) {
1302                 lookupTable.put(host, null);
1303                 return null;
1304             }
1305         }
1306 
1307         return addresses;
1308     }
1309 
1310     private static void updateLookupTable(String host) {
1311         synchronized (lookupTable) {
1312             lookupTable.remove(host);
1313             lookupTable.notifyAll();
1314         }
1315     }
1316 
1317     /**
1318      * Returns an <code>InetAddress</code> object given the raw IP address .
1319      * The argument is in network byte order: the highest order
1320      * byte of the address is in <code>getAddress()[0]</code>.
1321      *
1322      * <p> This method doesn't block, i.e. no reverse name service lookup
1323      * is performed.
1324      *
1325      * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
1326      * must be 16 bytes long
1327      *
1328      * @param addr the raw IP address in network byte order
1329      * @return  an InetAddress object created from the raw IP address.
1330      * @exception  UnknownHostException  if IP address is of illegal length
1331      * @since 1.4
1332      */
1333     public static InetAddress getByAddress(byte[] addr)
1334         throws UnknownHostException {
1335         return getByAddress(null, addr);
1336     }
1337 
1338     private static InetAddress cachedLocalHost = null;
1339     private static long cacheTime = 0;
1340     private static final long maxCacheTime = 5000L;
1341     private static final Object cacheLock = new Object();
1342 
1343     /**
1344      * Returns the address of the local host. This is achieved by retrieving
1345      * the name of the host from the system, then resolving that name into
1346      * an <code>InetAddress</code>.
1347      *
1348      * <P>Note: The resolved address may be cached for a short period of time.
1349      * </P>
1350      *
1351      * <p>If there is a security manager, its
1352      * <code>checkConnect</code> method is called
1353      * with the local host name and <code>-1</code>
1354      * as its arguments to see if the operation is allowed.
1355      * If the operation is not allowed, an InetAddress representing
1356      * the loopback address is returned.
1357      *
1358      * @return     the address of the local host.
1359      *
1360      * @exception  UnknownHostException  if the local host name could not
1361      *             be resolved into an address.
1362      *
1363      * @see SecurityManager#checkConnect
1364      * @see java.net.InetAddress#getByName(java.lang.String)
1365      */
1366     public static InetAddress getLocalHost() throws UnknownHostException {
1367 
1368         SecurityManager security = System.getSecurityManager();
1369         try {
1370             String local = impl.getLocalHostName();
1371 
1372             if (security != null) {
1373                 security.checkConnect(local, -1);
1374             }
1375 
1376             if (local.equals("localhost")) {
1377                 return impl.loopbackAddress();
1378             }
1379 
1380             InetAddress ret = null;
1381             synchronized (cacheLock) {
1382                 long now = System.currentTimeMillis();
1383                 if (cachedLocalHost != null) {
1384                     if ((now - cacheTime) < maxCacheTime) // Less than 5s old?
1385                         ret = cachedLocalHost;
1386                     else
1387                         cachedLocalHost = null;
1388                 }
1389 
1390                 // we are calling getAddressesFromNameService directly
1391                 // to avoid getting localHost from cache
1392                 if (ret == null) {
1393                     InetAddress[] localAddrs;
1394                     try {
1395                         localAddrs =
1396                             InetAddress.getAddressesFromNameService(local);
1397                     } catch (UnknownHostException uhe) {
1398                         // Rethrow with a more informative error message.
1399                         UnknownHostException uhe2 =
1400                             new UnknownHostException(local + ": " +
1401                                                      uhe.getMessage());
1402                         uhe2.initCause(uhe);
1403                         throw uhe2;
1404                     }
1405                     cachedLocalHost = localAddrs[0];
1406                     cacheTime = now;
1407                     ret = localAddrs[0];
1408                 }
1409             }
1410             return ret;
1411         } catch (java.lang.SecurityException e) {
1412             return impl.loopbackAddress();
1413         }
1414     }
1415 
1416     /**
1417      * Perform class load-time initializations.
1418      */
1419     private static native void init();
1420 
1421 
1422     /*
1423      * Returns the InetAddress representing anyLocalAddress
1424      * (typically 0.0.0.0 or ::0)
1425      */
1426     static InetAddress anyLocalAddress() {
1427         return impl.anyLocalAddress();
1428     }
1429 
1430     /*
1431      * Load and instantiate an underlying impl class
1432      */
1433     static InetAddressImpl loadImpl(String implName) {
1434         Object impl = null;
1435 
1436         /*
1437          * Property "impl.prefix" will be prepended to the classname
1438          * of the implementation object we instantiate, to which we
1439          * delegate the real work (like native methods).  This
1440          * property can vary across implementations of the java.
1441          * classes.  The default is an empty String "".
1442          */
1443         String prefix = AccessController.doPrivileged(
1444                       new GetPropertyAction("impl.prefix", ""));
1445         try {
1446             impl = Class.forName("java.net." + prefix + implName).newInstance();
1447         } catch (ClassNotFoundException e) {
1448             System.err.println("Class not found: java.net." + prefix +
1449                                implName + ":\ncheck impl.prefix property " +
1450                                "in your properties file.");
1451         } catch (InstantiationException e) {
1452             System.err.println("Could not instantiate: java.net." + prefix +
1453                                implName + ":\ncheck impl.prefix property " +
1454                                "in your properties file.");
1455         } catch (IllegalAccessException e) {
1456             System.err.println("Cannot access class: java.net." + prefix +
1457                                implName + ":\ncheck impl.prefix property " +
1458                                "in your properties file.");
1459         }
1460 
1461         if (impl == null) {
1462             try {
1463                 impl = Class.forName(implName).newInstance();
1464             } catch (Exception e) {
1465                 throw new Error("System property impl.prefix incorrect");
1466             }
1467         }
1468 
1469         return (InetAddressImpl) impl;
1470     }
1471 
1472     private void readObjectNoData (ObjectInputStream s) throws
1473                          IOException, ClassNotFoundException {
1474         if (getClass().getClassLoader() != null) {
1475             throw new SecurityException ("invalid address type");
1476         }
1477     }
1478 
1479     private void readObject (ObjectInputStream s) throws
1480                          IOException, ClassNotFoundException {
1481         s.defaultReadObject ();
1482         if (getClass().getClassLoader() != null) {
1483             hostName = null;
1484             address = 0;
1485             throw new SecurityException ("invalid address type");
1486         }
1487     }
1488 }
1489 
1490 /*
1491  * Simple factory to create the impl
1492  */
1493 class InetAddressImplFactory {
1494 
1495     static InetAddressImpl create() {
1496         return InetAddress.loadImpl(isIPv6Supported() ?
1497                                     "Inet6AddressImpl" : "Inet4AddressImpl");
1498     }
1499 
1500     static native boolean isIPv6Supported();
1501 }