content: /*
   * Copyright (C) 2014 The Android Open Source Project
   * Copyright (c) 1995, 2015, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package java.net;
  
  import java.io.ObjectStreamException;
  import java.io.ObjectStreamField;
  import java.io.IOException;
  import java.io.ObjectInputStream;
  import java.io.ObjectInputStream.GetField;
  import java.io.ObjectOutputStream;
  import java.io.ObjectOutputStream.PutField;
  import libcore.net.InetAddressUtils;
  import sun.net.util.IPAddressUtil;
  import sun.net.spi.nameservice.*;
  import libcore.io.Libcore;
  
  /**
   * This class represents an Internet Protocol (IP) address.
   *
   * <p> An IP address is either a 32-bit or 128-bit unsigned number
   * used by IP, a lower-level protocol on which protocols like UDP and
   * TCP are built. The IP address architecture is defined by <a
   * href="http://www.ietf.org/rfc/rfc790.txt"><i>RFC&nbsp;790:
   * Assigned Numbers</i></a>, <a
   * href="http://www.ietf.org/rfc/rfc1918.txt"> <i>RFC&nbsp;1918:
   * Address Allocation for Private Internets</i></a>, <a
   * href="http://www.ietf.org/rfc/rfc2365.txt"><i>RFC&nbsp;2365:
   * Administratively Scoped IP Multicast</i></a>, and <a
   * href="http://www.ietf.org/rfc/rfc2373.txt"><i>RFC&nbsp;2373: IP
   * Version 6 Addressing Architecture</i></a>. An instance of an
   * InetAddress consists of an IP address and possibly its
   * corresponding host name (depending on whether it is constructed
   * with a host name or whether it has already done reverse host name
   * resolution).
   *
   * <h3> Address types </h3>
   *
   * <blockquote><table cellspacing=2 summary="Description of unicast and multicast address types">
   *   <tr><th valign=top><i>unicast</i></th>
   *       <td>An identifier for a single interface. A packet sent to
   *         a unicast address is delivered to the interface identified by
   *         that address.
   *
   *         <p> The Unspecified Address -- Also called anylocal or wildcard
   *         address. It must never be assigned to any node. It indicates the
   *         absence of an address. One example of its use is as the target of
   *         bind, which allows a server to accept a client connection on any
   *         interface, in case the server host has multiple interfaces.
   *
   *         <p> The <i>unspecified</i> address must not be used as
   *         the destination address of an IP packet.
   *
   *         <p> The <i>Loopback</i> Addresses -- This is the address
   *         assigned to the loopback interface. Anything sent to this
   *         IP address loops around and becomes IP input on the local
   *         host. This address is often used when testing a
   *         client.</td></tr>
   *   <tr><th valign=top><i>multicast</i></th>
   *       <td>An identifier for a set of interfaces (typically belonging
   *         to different nodes). A packet sent to a multicast address is
   *         delivered to all interfaces identified by that address.</td></tr>
   * </table></blockquote>
   *
   * <h4> IP address scope </h4>
   *
   * <p> <i>Link-local</i> addresses are designed to be used for addressing
   * on a single link for purposes such as auto-address configuration,
   * neighbor discovery, or when no routers are present.
   *
   * <p> <i>Site-local</i> addresses are designed to be used for addressing
   * inside of a site without the need for a global prefix.
   *
   * <p> <i>Global</i> addresses are unique across the internet.
   *
   * <h4> Textual representation of IP addresses </h4>
   *
   * The textual representation of an IP address is address family specific.
   *
   * <p>
   *
   * For IPv4 address format, please refer to <A
   * HREF="Inet4Address.html#format">Inet4Address#format</A>; For IPv6
   * address format, please refer to <A
   * HREF="Inet6Address.html#format">Inet6Address#format</A>.
   *
   * <P>There is a <a href="doc-files/net-properties.html#Ipv4IPv6">couple of
   * System Properties</a> affecting how IPv4 and IPv6 addresses are used.</P>
   *
   * <h4> Host Name Resolution </h4>
   *
   * Host name-to-IP address <i>resolution</i> is accomplished through
   * the use of a combination of local machine configuration information
   * and network naming services such as the Domain Name System (DNS)
   * and Network Information Service(NIS). The particular naming
   * services(s) being used is by default the local machine configured
   * one. For any host name, its corresponding IP address is returned.
   *
   * <p> <i>Reverse name resolution</i> means that for any IP address,
   * the host associated with the IP address is returned.
   *
   * <p> The InetAddress class provides methods to resolve host names to
   * their IP addresses and vice versa.
   *
   * <h4> InetAddress Caching </h4>
   *
   * The InetAddress class has a cache to store successful as well as
   * unsuccessful host name resolutions.
   *
   * <p> By default, when a security manager is installed, in order to
   * protect against DNS spoofing attacks,
   * the result of positive host name resolutions are
   * cached forever. When a security manager is not installed, the default
   * behavior is to cache entries for a finite (implementation dependent)
   * period of time. The result of unsuccessful host
   * name resolution is cached for a very short period of time (10
   * seconds) to improve performance.
   *
   * <p> If the default behavior is not desired, then a Java security property
   * can be set to a different Time-to-live (TTL) value for positive
   * caching. Likewise, a system admin can configure a different
   * negative caching TTL value when needed.
   *
   * <p> Two Java security properties control the TTL values used for
   *  positive and negative host name resolution caching:
   *
   * <blockquote>
   * <dl>
   * <dt><b>networkaddress.cache.ttl</b></dt>
   * <dd>Indicates the caching policy for successful name lookups from
   * the name service. The value is specified as as integer to indicate
   * the number of seconds to cache the successful lookup. The default
   * setting is to cache for an implementation specific period of time.
   * <p>
   * A value of -1 indicates "cache forever".
   * </dd>
   * <dt><b>networkaddress.cache.negative.ttl</b> (default: 10)</dt>
   * <dd>Indicates the caching policy for un-successful name lookups
   * from the name service. The value is specified as as integer to
   * indicate the number of seconds to cache the failure for
   * un-successful lookups.
   * <p>
   * A value of 0 indicates "never cache".
   * A value of -1 indicates "cache forever".
   * </dd>
   * </dl>
   * </blockquote>
   *
   * @author  Chris Warth
   * @see     InetAddress#getByAddress(byte[])
   * @see     InetAddress#getByAddress(String, byte[])
   * @see     InetAddress#getAllByName(String)
   * @see     InetAddress#getByName(String)
   * @see     InetAddress#getLocalHost()
   * @since JDK1.0
   */
  public
  class InetAddress implements java.io.Serializable {
      // BEGIN Android-removed: Android uses linux-based OsConstants.
      /*
       * Specify the address family: Internet Protocol, Version 4
       * @since 1.4
       *
      static final int IPv4 = 1;
  
      /**
       * Specify the address family: Internet Protocol, Version 6
       * @since 1.4
       *
      static final int IPv6 = 2;
      */
      // END Android-removed: Android uses linux-based OsConstants.
  
      // Android-removed: Android doesn't support the preference.
      // /* Specify address family preference */
      //static transient boolean preferIPv6Address = false;
  
      static class InetAddressHolder {
          /**
           * Reserve the original application specified hostname.
           *
           * The original hostname is useful for domain-based endpoint
           * identification (see RFC 2818 and RFC 6125).  If an address
           * was created with a raw IP address, a reverse name lookup
           * may introduce endpoint identification security issue via
           * DNS forging.
           *
           * Oracle JSSE provider is using this original hostname, via
           * sun.misc.JavaNetAccess, for SSL/TLS endpoint identification.
           *
           * Note: May define a new public method in the future if necessary.
           */
          String originalHostName;
  
          InetAddressHolder() {}
  
          InetAddressHolder(String hostName, int address, int family) {
              this.originalHostName = hostName;
              this.hostName = hostName;
              this.address = address;
              this.family = family;
          }
  
          void init(String hostName, int family) {
              this.originalHostName = hostName;
              this.hostName = hostName;
              if (family != -1) {
                  this.family = family;
              }
          }
  
          String hostName;
  
          String getHostName() {
              return hostName;
          }
  
          String getOriginalHostName() {
              return originalHostName;
          }
  
          /**
           * Holds a 32-bit IPv4 address.
           */
          int address;
  
          int getAddress() {
              return address;
          }
  
          // Android-changed: Documentation: use Linux-based OsConstants.
          /**
           * Specifies the address family type, for instance, AF_INET for IPv4
           * addresses, and AF_INET6 for IPv6 addresses.
           */
          int family;
  
          int getFamily() {
              return family;
          }
      }
  
      transient InetAddressHolder holder;
  
      InetAddressHolder holder() {
          return holder;
      }
  
      /* The implementation is always dual stack IPv6/IPv4 on android */
      static final InetAddressImpl impl = new Inet6AddressImpl();
  
      /* Used to store the name service provider */
      // Android-changed: Android has only one name service.
      // Android doesn't allow user to provide custom name services.
      // private static List<NameService> nameServices = null;
      private static final NameService nameService = new NameService() {
          public InetAddress[] lookupAllHostAddr(String host, int netId)
                  throws UnknownHostException {
              return impl.lookupAllHostAddr(host, netId);
          }
          public String getHostByAddr(byte[] addr)
                  throws UnknownHostException {
              return impl.getHostByAddr(addr);
          }
      };
  
      /* Used to store the best available hostname */
      private transient String canonicalHostName = null;
  
      /** use serialVersionUID from JDK 1.0.2 for interoperability */
      private static final long serialVersionUID = 3286316764910316507L;
  
  
      // BEGIN Android-removed: Android doesn't need to load native library.
      /*
       * Load net library into runtime, and perform initializations.
       *
      static {
          preferIPv6Address = java.security.AccessController.doPrivileged(
              new GetBooleanAction("java.net.preferIPv6Addresses")).booleanValue();
          AccessController.doPrivileged(
              new java.security.PrivilegedAction<Void>() {
                  public Void run() {
                      System.loadLibrary("net");
                      return null;
                  }
              });
          init();
      }
      */
      // END Android-removed: Android doesn't need to load native library.
  
      /**
       * Constructor for the Socket.accept() method.
       * This creates an empty InetAddress, which is filled in by
       * the accept() method.  This InetAddress, however, is not
       * put in the address cache, since it is not created by name.
       */
      InetAddress() {
          holder = new InetAddressHolder();
      }
  
      /**
       * Replaces the de-serialized object with an Inet4Address object.
       *
       * @return the alternate object to the de-serialized object.
       *
       * @throws ObjectStreamException if a new object replacing this
       * object could not be created
       */
      private Object readResolve() throws ObjectStreamException {
          // will replace the deserialized 'this' object
          return new Inet4Address(holder().getHostName(), holder().getAddress());
      }
  
      /**
       * Utility routine to check if the InetAddress is an
       * IP multicast address.
       * @return a {@code boolean} indicating if the InetAddress is
       * an IP multicast address
       * @since   JDK1.1
       */
      public boolean isMulticastAddress() {
          return false;
      }
  
      /**
       * Utility routine to check if the InetAddress in a wildcard address.
       * @return a {@code boolean} indicating if the Inetaddress is
       *         a wildcard address.
       * @since 1.4
       */
      public boolean isAnyLocalAddress() {
          return false;
      }
  
      /**
       * Utility routine to check if the InetAddress is a loopback address.
       *
       * @return a {@code boolean} indicating if the InetAddress is
       * a loopback address; or false otherwise.
       * @since 1.4
       */
      public boolean isLoopbackAddress() {
          return false;
      }
  
      /**
       * Utility routine to check if the InetAddress is an link local address.
       *
       * @return a {@code boolean} indicating if the InetAddress is
       * a link local address; or false if address is not a link local unicast address.
       * @since 1.4
       */
      public boolean isLinkLocalAddress() {
          return false;
      }
  
      /**
       * Utility routine to check if the InetAddress is a site local address.
       *
       * @return a {@code boolean} indicating if the InetAddress is
       * a site local address; or false if address is not a site local unicast address.
       * @since 1.4
       */
      public boolean isSiteLocalAddress() {
          return false;
      }
  
      /**
       * Utility routine to check if the multicast address has global scope.
       *
       * @return a {@code boolean} indicating if the address has
       *         is a multicast address of global scope, false if it is not
       *         of global scope or it is not a multicast address
       * @since 1.4
       */
      public boolean isMCGlobal() {
          return false;
      }
  
      /**
       * Utility routine to check if the multicast address has node scope.
       *
       * @return a {@code boolean} indicating if the address has
       *         is a multicast address of node-local scope, false if it is not
       *         of node-local scope or it is not a multicast address
       * @since 1.4
       */
      public boolean isMCNodeLocal() {
          return false;
      }
  
      /**
       * Utility routine to check if the multicast address has link scope.
       *
       * @return a {@code boolean} indicating if the address has
       *         is a multicast address of link-local scope, false if it is not
       *         of link-local scope or it is not a multicast address
       * @since 1.4
       */
      public boolean isMCLinkLocal() {
          return false;
      }
  
      /**
       * Utility routine to check if the multicast address has site scope.
       *
       * @return a {@code boolean} indicating if the address has
       *         is a multicast address of site-local scope, false if it is not
       *         of site-local scope or it is not a multicast address
       * @since 1.4
       */
      public boolean isMCSiteLocal() {
          return false;
      }
  
      /**
       * Utility routine to check if the multicast address has organization scope.
       *
       * @return a {@code boolean} indicating if the address has
       *         is a multicast address of organization-local scope,
       *         false if it is not of organization-local scope
       *         or it is not a multicast address
       * @since 1.4
       */
      public boolean isMCOrgLocal() {
          return false;
      }
  
  
      // Android-changed: Document that impl tries ICMP ECHO REQUESTs first.
      // The sole implementation, Inet6AddressImpl.isReachable(), tries ICMP ECHO REQUESTs before
      // TCP ECHO REQUESTs on Android. On Android, these are both possible without root access.
      /**
       * Test whether that address is reachable. Best effort is made by the
       * implementation to try to reach the host, but firewalls and server
       * configuration may block requests resulting in a unreachable status
       * while some specific ports may be accessible.
       * <p>
       * Android implementation attempts ICMP ECHO REQUESTs first, on failure it
       * will fall back to TCP ECHO REQUESTs. Success on either protocol will
       * return true.
       * <p>
       * The timeout value, in milliseconds, indicates the maximum amount of time
       * the try should take. If the operation times out before getting an
       * answer, the host is deemed unreachable. A negative value will result
       * in an IllegalArgumentException being thrown.
       *
       * @param   timeout the time, in milliseconds, before the call aborts
       * @return a {@code boolean} indicating if the address is reachable.
       * @throws IOException if a network error occurs
       * @throws  IllegalArgumentException if {@code timeout} is negative.
       * @since 1.5
       */
      public boolean isReachable(int timeout) throws IOException {
          return isReachable(null, 0 , timeout);
      }
  
      // Android-changed: Document that impl tries ICMP ECHO REQUESTs first.
      // The sole implementation, Inet6AddressImpl.isReachable(), tries ICMP ECHO REQUESTs before
      // TCP ECHO REQUESTs on Android. On Android, these are both possible without root access.
      /**
       * Test whether that address is reachable. Best effort is made by the
       * implementation to try to reach the host, but firewalls and server
       * configuration may block requests resulting in a unreachable status
       * while some specific ports may be accessible.
       * <p>
       * Android implementation attempts ICMP ECHO REQUESTs first, on failure it
       * will fall back to TCP ECHO REQUESTs. Success on either protocol will
       * return true.
       * <p>
       * The {@code network interface} and {@code ttl} parameters
       * let the caller specify which network interface the test will go through
       * and the maximum number of hops the packets should go through.
       * A negative value for the {@code ttl} will result in an
       * IllegalArgumentException being thrown.
       * <p>
       * The timeout value, in milliseconds, indicates the maximum amount of time
       * the try should take. If the operation times out before getting an
       * answer, the host is deemed unreachable. A negative value will result
       * in an IllegalArgumentException being thrown.
       *
       * @param   netif   the NetworkInterface through which the
       *                    test will be done, or null for any interface
       * @param   ttl     the maximum numbers of hops to try or 0 for the
       *                  default
       * @param   timeout the time, in milliseconds, before the call aborts
       * @throws  IllegalArgumentException if either {@code timeout}
       *                          or {@code ttl} are negative.
       * @return a {@code boolean}indicating if the address is reachable.
       * @throws IOException if a network error occurs
       * @since 1.5
       */
      public boolean isReachable(NetworkInterface netif, int ttl,
                                 int timeout) throws IOException {
          if (ttl < 0)
              throw new IllegalArgumentException("ttl can't be negative");
          if (timeout < 0)
              throw new IllegalArgumentException("timeout can't be negative");
  
          return impl.isReachable(this, timeout, netif, ttl);
      }
  
      // BEGIN Android-added: isReachableByICMP(timeout).
      /**
       * @hide For testing only
       */
      public boolean isReachableByICMP(int timeout) throws IOException {
          return ((Inet6AddressImpl) impl).icmpEcho(this, timeout, null, 0);
      }
      // END Android-added: isReachableByICMP(timeout).
  
      /**
       * Gets the host name for this IP address.
       *
       * <p>If this InetAddress was created with a host name,
       * this host name will be remembered and returned;
       * otherwise, a reverse name lookup will be performed
       * and the result will be returned based on the system
       * configured name lookup service. If a lookup of the name service
       * is required, call
       * {@link #getCanonicalHostName() getCanonicalHostName}.
       *
       * <p>If there is a security manager, its
       * {@code checkConnect} method is first called
       * with the hostname and {@code -1}
       * as its arguments to see if the operation is allowed.
       * If the operation is not allowed, it will return
       * the textual representation of the IP address.
       *
       * @return  the host name for this IP address, or if the operation
       *    is not allowed by the security check, the textual
       *    representation of the IP address.
       *
       * @see InetAddress#getCanonicalHostName
       * @see SecurityManager#checkConnect
       */
      public String getHostName() {
          // Android-changed: Remove SecurityManager check.
          if (holder().getHostName() == null) {
              holder().hostName = InetAddress.getHostFromNameService(this);
          }
          return holder().getHostName();
      }
  
      // BEGIN Android-removed: Android doesn't support SecurityManager.
      /*
       * Returns the hostname for this address.
       * If the host is equal to null, then this address refers to any
       * of the local machine's available network addresses.
       * this is package private so SocketPermission can make calls into
       * here without a security check.
       *
       * <p>If there is a security manager, this method first
       * calls its {@code checkConnect} method
       * with the hostname and {@code -1}
       * as its arguments to see if the calling code is allowed to know
       * the hostname for this IP address, i.e., to connect to the host.
       * If the operation is not allowed, it will return
       * the textual representation of the IP address.
       *
       * @return  the host name for this IP address, or if the operation
       *    is not allowed by the security check, the textual
       *    representation of the IP address.
       *
       * @param check make security check if true
       *
       * @see SecurityManager#checkConnect
       *
      String getHostName(boolean check) {
          if (holder().getHostName() == null) {
              holder().hostName = InetAddress.getHostFromNameService(this, check);
          }
          return holder().getHostName();
      }
      */
      // END Android-removed: Android doesn't support SecurityManager.
  
      /**
       * Gets the fully qualified domain name for this IP address.
       * Best effort method, meaning we may not be able to return
       * the FQDN depending on the underlying system configuration.
       *
       * <p>If there is a security manager, this method first
       * calls its {@code checkConnect} method
       * with the hostname and {@code -1}
       * as its arguments to see if the calling code is allowed to know
       * the hostname for this IP address, i.e., to connect to the host.
       * If the operation is not allowed, it will return
       * the textual representation of the IP address.
       *
       * @return  the fully qualified domain name for this IP address,
       *    or if the operation is not allowed by the security check,
       *    the textual representation of the IP address.
       *
       * @see SecurityManager#checkConnect
       *
       * @since 1.4
       */
      public String getCanonicalHostName() {
          // Android-changed: Remove SecurityManager check.
          if (canonicalHostName == null) {
              canonicalHostName = InetAddress.getHostFromNameService(this);
          }
          return canonicalHostName;
      }
  
      // Android-changed: Remove SecurityManager check.
      // * @param check make security check if true
      /**
       * Returns the hostname for this address.
       *
       * <p>If there is a security manager, this method first
       * calls its {@code checkConnect} method
       * with the hostname and {@code -1}
       * as its arguments to see if the calling code is allowed to know
       * the hostname for this IP address, i.e., to connect to the host.
       * If the operation is not allowed, it will return
       * the textual representation of the IP address.
       *
       * @return  the host name for this IP address, or if the operation
       *    is not allowed by the security check, the textual
       *    representation of the IP address.
       *
       * @see SecurityManager#checkConnect
       */
      private static String getHostFromNameService(InetAddress addr) {
          String host = null;
          try {
              // first lookup the hostname
              // Android-changed: Android has only one name service.
              host = nameService.getHostByAddr(addr.getAddress());
  
                  /* now get all the IP addresses for this hostname,
                   * and make sure one of them matches the original IP
                   * address. We do this to try and prevent spoofing.
                   */
              InetAddress[] arr = nameService.lookupAllHostAddr(host, NETID_UNSET);
              boolean ok = false;
  
              if (arr != null) {
                  for(int i = 0; !ok && i < arr.length; i++) {
                      ok = addr.equals(arr[i]);
                  }
              }
  
              //XXX: if it looks a spoof just return the address?
              if (!ok) {
                  host = addr.getHostAddress();
                  return host;
              }
          } catch (UnknownHostException e) {
              host = addr.getHostAddress();
          }
  
          return host;
      }
  
      /**
       * Returns the raw IP address of this {@code InetAddress}
       * object. The result is in network byte order: the highest order
       * byte of the address is in {@code getAddress()[0]}.
       *
       * @return  the raw IP address of this object.
       */
      public byte[] getAddress() {
          return null;
      }
  
      /**
       * Returns the IP address string in textual presentation.
       *
       * @return  the raw IP address in a string format.
       * @since   JDK1.0.2
       */
      public String getHostAddress() {
          return null;
       }
  
      /**
       * Returns a hashcode for this IP address.
       *
       * @return  a hash code value for this IP address.
       */
      public int hashCode() {
          return -1;
      }
  
      /**
       * Compares this object against the specified object.
       * The result is {@code true} if and only if the argument is
       * not {@code null} and it represents the same IP address as
       * this object.
       * <p>
       * Two instances of {@code InetAddress} represent the same IP
       * address if the length of the byte arrays returned by
       * {@code getAddress} is the same for both, and each of the
       * array components is the same for the byte arrays.
       *
       * @param   obj   the object to compare against.
       * @return  {@code true} if the objects are the same;
       *          {@code false} otherwise.
       * @see     InetAddress#getAddress()
       */
      public boolean equals(Object obj) {
          return false;
      }
  
      /**
       * Converts this IP address to a {@code String}. The
       * string returned is of the form: hostname / literal IP
       * address.
       *
       * If the host name is unresolved, no reverse name service lookup
       * is performed. The hostname part will be represented by an empty string.
       *
       * @return  a string representation of this IP address.
       */
      public String toString() {
          String hostName = holder().getHostName();
          return ((hostName != null) ? hostName : "")
              + "/" + getHostAddress();
      }
  
      // BEGIN Android-removed: Resolves a hostname using Libcore.os.
      /*
       * Cached addresses - our own litle nis, not!
       *
      private static Cache addressCache = new Cache(Cache.Type.Positive);
  
      private static Cache negativeCache = new Cache(Cache.Type.Negative);
  
      private static boolean addressCacheInit = false;
  
      static InetAddress[]    unknown_array; // put THIS in cache
  
      static InetAddressImpl  impl;
  
      private static final HashMap<String, Void> lookupTable = new HashMap<>();
  
      /**
       * Represents a cache entry
       *
      static final class CacheEntry {
  
          CacheEntry(InetAddress[] addresses, long expiration) {
              this.addresses = addresses;
              this.expiration = expiration;
          }
  
          InetAddress[] addresses;
          long expiration;
      }
  
      /**
       * A cache that manages entries based on a policy specified
       * at creation time.
       *
      static final class Cache {
          private LinkedHashMap<String, CacheEntry> cache;
          private Type type;
  
          enum Type {Positive, Negative};
  
          /**
           * Create cache
           *
          public Cache(Type type) {
              this.type = type;
              cache = new LinkedHashMap<String, CacheEntry>();
          }
  
          private int getPolicy() {
              if (type == Type.Positive) {
                  return InetAddressCachePolicy.get();
              } else {
                  return InetAddressCachePolicy.getNegative();
              }
          }
  
          /**
           * Add an entry to the cache. If there's already an
           * entry then for this host then the entry will be
           * replaced.
           *
          public Cache put(String host, InetAddress[] addresses) {
              int policy = getPolicy();
              if (policy == InetAddressCachePolicy.NEVER) {
                  return this;
              }
  
              // purge any expired entries
  
              if (policy != InetAddressCachePolicy.FOREVER) {
  
                  // As we iterate in insertion order we can
                  // terminate when a non-expired entry is found.
                  LinkedList<String> expired = new LinkedList<>();
                  long now = System.currentTimeMillis();
                  for (String key : cache.keySet()) {
                      CacheEntry entry = cache.get(key);
  
                      if (entry.expiration >= 0 && entry.expiration < now) {
                          expired.add(key);
                      } else {
                          break;
                      }
                  }
  
                  for (String key : expired) {
                      cache.remove(key);
                  }
              }
  
              // create new entry and add it to the cache
              // -- as a HashMap replaces existing entries we
              //    don't need to explicitly check if there is
              //    already an entry for this host.
              long expiration;
              if (policy == InetAddressCachePolicy.FOREVER) {
                  expiration = -1;
              } else {
                  expiration = System.currentTimeMillis() + (policy * 1000);
              }
              CacheEntry entry = new CacheEntry(addresses, expiration);
              cache.put(host, entry);
              return this;
          }
  
          /**
           * Query the cache for the specific host. If found then
           * return its CacheEntry, or null if not found.
           *
          public CacheEntry get(String host) {
              int policy = getPolicy();
              if (policy == InetAddressCachePolicy.NEVER) {
                  return null;
              }
              CacheEntry entry = cache.get(host);
  
              // check if entry has expired
              if (entry != null && policy != InetAddressCachePolicy.FOREVER) {
                  if (entry.expiration >= 0 &&
                          entry.expiration < System.currentTimeMillis()) {
                      cache.remove(host);
                      entry = null;
                  }
              }
  
              return entry;
          }
      }
  
      /*
       * Initialize cache and insert anyLocalAddress into the
       * unknown array with no expiry.
       *
      private static void cacheInitIfNeeded() {
          assert Thread.holdsLock(addressCache);
          if (addressCacheInit) {
              return;
          }
          unknown_array = new InetAddress[1];
          unknown_array[0] = impl.anyLocalAddress();
  
          addressCache.put(impl.anyLocalAddress().getHostName(),
                           unknown_array);
  
          addressCacheInit = true;
      }
  
      /*
       * Cache the given hostname and addresses.
       *
      private static void cacheAddresses(String hostname,
                                         InetAddress[] addresses,
                                         boolean success) {
          hostname = hostname.toLowerCase();
          synchronized (addressCache) {
              cacheInitIfNeeded();
              if (success) {
                  addressCache.put(hostname, addresses);
              } else {
                  negativeCache.put(hostname, addresses);
              }
          }
      }
  
      /*
       * Lookup hostname in cache (positive & negative cache). If
       * found return addresses, null if not found.
       *
      private static InetAddress[] getCachedAddresses(String hostname) {
          hostname = hostname.toLowerCase();
  
          // search both positive & negative caches
  
          synchronized (addressCache) {
              cacheInitIfNeeded();
  
              CacheEntry entry = addressCache.get(hostname);
              if (entry == null) {
                  entry = negativeCache.get(hostname);
              }
  
              if (entry != null) {
                  return entry.addresses;
              }
          }
  
          // not found
          return null;
      }
  
      private static NameService createNSProvider(String provider) {
          if (provider == null)
              return null;
  
          NameService nameService = null;
          if (provider.equals("default")) {
              // initialize the default name service
              nameService = new NameService() {
                  public InetAddress[] lookupAllHostAddr(String host)
                      throws UnknownHostException {
                      return impl.lookupAllHostAddr(host);
                  }
                  public String getHostByAddr(byte[] addr)
                      throws UnknownHostException {
                      return impl.getHostByAddr(addr);
                  }
              };
          } else {
              final String providerName = provider;
              try {
                  nameService = java.security.AccessController.doPrivileged(
                      new java.security.PrivilegedExceptionAction<NameService>() {
                          public NameService run() {
                              Iterator<NameServiceDescriptor> itr =
                                  ServiceLoader.load(NameServiceDescriptor.class)
                                      .iterator();
                              while (itr.hasNext()) {
                                  NameServiceDescriptor nsd = itr.next();
                                  if (providerName.
                                      equalsIgnoreCase(nsd.getType()+","
                                          +nsd.getProviderName())) {
                                      try {
                                          return nsd.createNameService();
                                      } catch (Exception e) {
                                          e.printStackTrace();
                                          System.err.println(
                                              "Cannot create name service:"
                                               +providerName+": " + e);
                                      }
                                  }
                              }
  
                              return null;
                          }
                      }
                  );
              } catch (java.security.PrivilegedActionException e) {
              }
          }
  
          return nameService;
      }
  
      static {
          // create the impl
          impl = InetAddressImplFactory.create();
  
          // get name service if provided and requested
          String provider = null;;
          String propPrefix = "sun.net.spi.nameservice.provider.";
          int n = 1;
          nameServices = new ArrayList<NameService>();
          provider = AccessController.doPrivileged(
                  new GetPropertyAction(propPrefix + n));
          while (provider != null) {
              NameService ns = createNSProvider(provider);
              if (ns != null)
                  nameServices.add(ns);
  
              n++;
              provider = AccessController.doPrivileged(
                      new GetPropertyAction(propPrefix + n));
          }
  
          // if not designate any name services provider,
          // create a default one
          if (nameServices.size() == 0) {
              NameService ns = createNSProvider("default");
              nameServices.add(ns);
          }
      }
      */
      // END Android-removed: Resolves a hostname using Libcore.os.
  
      /**
       * Creates an InetAddress based on the provided host name and IP address.
       * No name service is checked for the validity of the address.
       *
       * <p> The host name can either be a machine name, such as
       * "{@code java.sun.com}", or a textual representation of its IP
       * address.
       * <p> No validity checking is done on the host name either.
       *
       * <p> If addr specifies an IPv4 address an instance of Inet4Address
       * will be returned; otherwise, an instance of Inet6Address
       * will be returned.
       *
       * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
       * must be 16 bytes long
       *
       * @param host the specified host
       * @param addr the raw IP address in network byte order
       * @return  an InetAddress object created from the raw IP address.
       * @exception  UnknownHostException  if IP address is of illegal length
       * @since 1.4
       */
      public static InetAddress getByAddress(String host, byte[] addr) throws UnknownHostException {
          return getByAddress(host, addr, -1 /* scopeId */);
      }
  
      // Android-added: Called by native code in Libcore.io.
      // Do not delete. Called from native code.
      private static InetAddress getByAddress(String host, byte[] addr, int scopeId)
          throws UnknownHostException {
          if (host != null && host.length() > 0 && host.charAt(0) == '[') {
              if (host.charAt(host.length()-1) == ']') {
                  host = host.substring(1, host.length() -1);
              }
          }
          if (addr != null) {
              if (addr.length == Inet4Address.INADDRSZ) {
                  return new Inet4Address(host, addr);
              } else if (addr.length == Inet6Address.INADDRSZ) {
                  byte[] newAddr
                      = IPAddressUtil.convertFromIPv4MappedAddress(addr);
                  if (newAddr != null) {
                      return new Inet4Address(host, newAddr);
                  } else {
                      return new Inet6Address(host, addr, scopeId);
                  }
              }
          }
          throw new UnknownHostException("addr is of illegal length");
      }
  
  
      /**
       * Determines the IP address of a host, given the host's name.
       *
       * <p> The host name can either be a machine name, such as
       * "{@code java.sun.com}", or a textual representation of its
       * IP address. If a literal IP address is supplied, only the
       * validity of the address format is checked.
       *
       * <p> For {@code host} specified in literal IPv6 address,
       * either the form defined in RFC 2732 or the literal IPv6 address
       * format defined in RFC 2373 is accepted. IPv6 scoped addresses are also
       * supported. See <a href="Inet6Address.html#scoped">here</a> for a description of IPv6
       * scoped addresses.
       *
       * <p> If the host is {@code null} then an {@code InetAddress}
       * representing an address of the loopback interface is returned.
       * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC&nbsp;3330</a>
       * section&nbsp;2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC&nbsp;2373</a>
       * section&nbsp;2.5.3. </p>
       *
       * @param      host   the specified host, or {@code null}.
       * @return     an IP address for the given host name.
       * @exception  UnknownHostException  if no IP address for the
       *               {@code host} could be found, or if a scope_id was specified
       *               for a global IPv6 address.
       * @exception  SecurityException if a security manager exists
       *             and its checkConnect method doesn't allow the operation
       */
      public static InetAddress getByName(String host)
          throws UnknownHostException {
          // Android-changed: Rewritten on the top of Libcore.os.
          return impl.lookupAllHostAddr(host, NETID_UNSET)[0];
      }
  
      /**
       * Given the name of a host, returns an array of its IP addresses,
       * based on the configured name service on the system.
       *
       * <p> The host name can either be a machine name, such as
       * "{@code java.sun.com}", or a textual representation of its IP
       * address. If a literal IP address is supplied, only the
       * validity of the address format is checked.
       *
       * <p> For {@code host} specified in <i>literal IPv6 address</i>,
       * either the form defined in RFC 2732 or the literal IPv6 address
       * format defined in RFC 2373 is accepted. A literal IPv6 address may
       * also be qualified by appending a scoped zone identifier or scope_id.
       * The syntax and usage of scope_ids is described
       * <a href="Inet6Address.html#scoped">here</a>.
       * <p> If the host is {@code null} then an {@code InetAddress}
       * representing an address of the loopback interface is returned.
       * See <a href="http://www.ietf.org/rfc/rfc3330.txt">RFC&nbsp;3330</a>
       * section&nbsp;2 and <a href="http://www.ietf.org/rfc/rfc2373.txt">RFC&nbsp;2373</a>
       * section&nbsp;2.5.3. </p>
       *
       * <p> If there is a security manager and {@code host} is not
       * null and {@code host.length() } is not equal to zero, the
       * security manager's
       * {@code checkConnect} method is called
       * with the hostname and {@code -1}
       * as its arguments to see if the operation is allowed.
       *
       * @param      host   the name of the host, or {@code null}.
       * @return     an array of all the IP addresses for a given host name.
       *
       * @exception  UnknownHostException  if no IP address for the
       *               {@code host} could be found, or if a scope_id was specified
       *               for a global IPv6 address.
       * @exception  SecurityException  if a security manager exists and its
       *               {@code checkConnect} method doesn't allow the operation.
       *
       * @see SecurityManager#checkConnect
       */
      public static InetAddress[] getAllByName(String host)
          throws UnknownHostException {
          // Android-changed: Resolves a hostname using Libcore.os.
          // Also, returns both the Inet4 and Inet6 loopback for null/empty host
          return impl.lookupAllHostAddr(host, NETID_UNSET).clone();
      }
  
      /**
       * Returns the loopback address.
       * <p>
       * The InetAddress returned will represent the IPv4
       * loopback address, 127.0.0.1, or the IPv6 loopback
       * address, ::1. The IPv4 loopback address returned
       * is only one of many in the form 127.*.*.*
       *
       * @return  the InetAddress loopback instance.
       * @since 1.7
       */
      public static InetAddress getLoopbackAddress() {
          // Android-changed: Always returns IPv6 loopback address in Android.
          return impl.loopbackAddresses()[0];
      }
  
      // BEGIN Android-removed: Resolves a hostname using Libcore.os.
      /*
       * check if the literal address string has %nn appended
       * returns -1 if not, or the numeric value otherwise.
       *
       * %nn may also be a string that represents the displayName of
       * a currently available NetworkInterface.
       *
      private static int checkNumericZone (String s) throws UnknownHostException {
          int percent = s.indexOf ('%');
          int slen = s.length();
          int digit, zone=0;
          if (percent == -1) {
              return -1;
          }
          for (int i=percent+1; i<slen; i++) {
              char c = s.charAt(i);
              if (c == ']') {
                  if (i == percent+1) {
                      /* empty per-cent field *
                      return -1;
                  }
                  break;
              }
              if ((digit = Character.digit (c, 10)) < 0) {
                  return -1;
              }
              zone = (zone * 10) + digit;
          }
          return zone;
      }
  
      private static InetAddress[] getAllByName0 (String host)
          throws UnknownHostException
      {
          return getAllByName0(host, true);
      }
  
      /**
       * package private so SocketPermission can call it
       *
      static InetAddress[] getAllByName0 (String host, boolean check)
          throws UnknownHostException  {
          return getAllByName0 (host, null, check);
      }
  
      private static InetAddress[] getAllByName0 (String host, InetAddress reqAddr, boolean check)
          throws UnknownHostException  {
  
          /* If it gets here it is presumed to be a hostname */
          /* Cache.get can return: null, unknownAddress, or InetAddress[] */
  
          /* make sure the connection to the host is allowed, before we
           * give out a hostname
           *
          if (check) {
              SecurityManager security = System.getSecurityManager();
              if (security != null) {
                  security.checkConnect(host, -1);
              }
          }
  
          InetAddress[] addresses = getCachedAddresses(host);
  
          /* If no entry in cache, then do the host lookup *
          if (addresses == null) {
              addresses = getAddressesFromNameService(host, reqAddr);
          }
  
          if (addresses == unknown_array)
              throw new UnknownHostException(host);
  
          return addresses.clone();
      }
  
      private static InetAddress[] getAddressesFromNameService(String host, InetAddress reqAddr)
          throws UnknownHostException
      {
          InetAddress[] addresses = null;
          boolean success = false;
          UnknownHostException ex = null;
  
          // Check whether the host is in the lookupTable.
          // 1) If the host isn't in the lookupTable when
          //    checkLookupTable() is called, checkLookupTable()
          //    would add the host in the lookupTable and
          //    return null. So we will do the lookup.
          // 2) If the host is in the lookupTable when
          //    checkLookupTable() is called, the current thread
          //    would be blocked until the host is removed
          //    from the lookupTable. Then this thread
          //    should try to look up the addressCache.
          //     i) if it found the addresses in the
          //        addressCache, checkLookupTable()  would
          //        return the addresses.
          //     ii) if it didn't find the addresses in the
          //         addressCache for any reason,
          //         it should add the host in the
          //         lookupTable and return null so the
          //         following code would do  a lookup itself.
          if ((addresses = checkLookupTable(host)) == null) {
              try {
                  // This is the first thread which looks up the addresses
                  // this host or the cache entry for this host has been
                  // expired so this thread should do the lookup.
                  for (NameService nameService : nameServices) {
                      try {
                          /*
                           * Do not put the call to lookup() inside the
                           * constructor.  if you do you will still be
                           * allocating space when the lookup fails.
                           *
  
                          addresses = nameService.lookupAllHostAddr(host);
                          success = true;
                          break;
                      } catch (UnknownHostException uhe) {
                          if (host.equalsIgnoreCase("localhost")) {
                              InetAddress[] local = new InetAddress[] { impl.loopbackAddress() };
                              addresses = local;
                              success = true;
                              break;
                          }
                          else {
                              addresses = unknown_array;
                              success = false;
                              ex = uhe;
                          }
                      }
                  }
  
                  // More to do?
                  if (reqAddr != null && addresses.length > 1 && !addresses[0].equals(reqAddr)) {
                      // Find it?
                      int i = 1;
                      for (; i < addresses.length; i++) {
                          if (addresses[i].equals(reqAddr)) {
                              break;
                          }
                      }
                      // Rotate
                      if (i < addresses.length) {
                          InetAddress tmp, tmp2 = reqAddr;
                          for (int j = 0; j < i; j++) {
                              tmp = addresses[j];
                              addresses[j] = tmp2;
                              tmp2 = tmp;
                          }
                          addresses[i] = tmp2;
                      }
                  }
                  // Cache the address.
                  cacheAddresses(host, addresses, success);
  
                  if (!success && ex != null)
                      throw ex;
  
              } finally {
                  // Delete host from the lookupTable and notify
                  // all threads waiting on the lookupTable monitor.
                  updateLookupTable(host);
              }
          }
  
          return addresses;
      }
  
  
      private static InetAddress[] checkLookupTable(String host) {
          synchronized (lookupTable) {
              // If the host isn't in the lookupTable, add it in the
              // lookuptable and return null. The caller should do
              // the lookup.
              if (lookupTable.containsKey(host) == false) {
                  lookupTable.put(host, null);
                  return null;
              }
  
              // If the host is in the lookupTable, it means that another
              // thread is trying to look up the addresses of this host.
              // This thread should wait.
              while (lookupTable.containsKey(host)) {
                  try {
                      lookupTable.wait();
                  } catch (InterruptedException e) {
                  }
              }
          }
  
          // The other thread has finished looking up the addresses of
          // the host. This thread should retry to get the addresses
          // from the addressCache. If it doesn't get the addresses from
          // the cache, it will try to look up the addresses itself.
          InetAddress[] addresses = getCachedAddresses(host);
          if (addresses == null) {
              synchronized (lookupTable) {
                  lookupTable.put(host, null);
                  return null;
              }
          }
  
          return addresses;
      }
  
      private static void updateLookupTable(String host) {
          synchronized (lookupTable) {
              lookupTable.remove(host);
              lookupTable.notifyAll();
          }
      }
      */
      // END Android-removed: Resolves a hostname using Libcore.os.
  
      /**
       * Returns an {@code InetAddress} object given the raw IP address .
       * The argument is in network byte order: the highest order
       * byte of the address is in {@code getAddress()[0]}.
       *
       * <p> This method doesn't block, i.e. no reverse name service lookup
       * is performed.
       *
       * <p> IPv4 address byte array must be 4 bytes long and IPv6 byte array
       * must be 16 bytes long
       *
       * @param addr the raw IP address in network byte order
       * @return  an InetAddress object created from the raw IP address.
       * @exception  UnknownHostException  if IP address is of illegal length
       * @since 1.4
       */
      public static InetAddress getByAddress(byte[] addr)
          throws UnknownHostException {
          return getByAddress(null, addr);
      }
  
      // BEGIN Android-removed: Resolves a hostname using Libcore.os.
      /*
      private static InetAddress cachedLocalHost = null;
      private static long cacheTime = 0;
      private static final long maxCacheTime = 5000L;
      private static final Object cacheLock = new Object();
      */
      // END Android-removed: Resolves a hostname using Libcore.os.
  
      /**
       * Returns the address of the local host. This is achieved by retrieving
       * the name of the host from the system, then resolving that name into
       * an {@code InetAddress}.
       *
       * <P>Note: The resolved address may be cached for a short period of time.
       * </P>
       *
       * <p>If there is a security manager, its
       * {@code checkConnect} method is called
       * with the local host name and {@code -1}
       * as its arguments to see if the operation is allowed.
       * If the operation is not allowed, an InetAddress representing
       * the loopback address is returned.
       *
       * @return     the address of the local host.
       *
       * @exception  UnknownHostException  if the local host name could not
       *             be resolved into an address.
       *
       * @see SecurityManager#checkConnect
       * @see InetAddress#getByName(String)
       */
      public static InetAddress getLocalHost() throws UnknownHostException {
          // BEGIN Android-changed: Resolves a hostname using Libcore.os.
          /*
          SecurityManager security = System.getSecurityManager();
          try {
              String local = impl.getLocalHostName();
  
              if (security != null) {
                  security.checkConnect(local, -1);
              }
  
              if (local.equals("localhost")) {
                  return impl.loopbackAddress();
              }
  
              InetAddress ret = null;
              synchronized (cacheLock) {
                  long now = System.currentTimeMillis();
                  if (cachedLocalHost != null) {
                      if ((now - cacheTime) < maxCacheTime) // Less than 5s old?
                          ret = cachedLocalHost;
                      else
                          cachedLocalHost = null;
                  }
  
                  // we are calling getAddressesFromNameService directly
                  // to avoid getting localHost from cache
                  if (ret == null) {
                      InetAddress[] localAddrs;
                      try {
                          localAddrs =
                              InetAddress.getAddressesFromNameService(local, null);
                      } catch (UnknownHostException uhe) {
                          // Rethrow with a more informative error message.
                          UnknownHostException uhe2 =
                              new UnknownHostException(local + ": " +
                                                       uhe.getMessage());
                          uhe2.initCause(uhe);
                          throw uhe2;
                      }
                      cachedLocalHost = localAddrs[0];
                      cacheTime = now;
                      ret = localAddrs[0];
                  }
              }
              return ret;
          } catch (java.lang.SecurityException e) {
              return impl.loopbackAddress();
          }
          */
          String local = Libcore.os.uname().nodename;
          return impl.lookupAllHostAddr(local, NETID_UNSET)[0];
          // END Android-changed: Resolves a hostname using Libcore.os.
      }
  
      // BEGIN Android-removed: Android doesn't need to call native init.
      /**
       * Perform class load-time initializations.
       *
      private static native void init();
      */
      // END Android-removed: Android doesn't need to call native init.
  
      /*
       * Returns the InetAddress representing anyLocalAddress
       * (typically 0.0.0.0 or ::0)
       */
      static InetAddress anyLocalAddress() {
          return impl.anyLocalAddress();
      }
  
      // BEGIN Android-removed: Android doesn't load user-provided implementation.
      /*
       * Load and instantiate an underlying impl class
       *
      static InetAddressImpl loadImpl(String implName) {
          Object impl = null;
  
          /*
           * Property "impl.prefix" will be prepended to the classname
           * of the implementation object we instantiate, to which we
           * delegate the real work (like native methods).  This
           * property can vary across implementations of the java.
           * classes.  The default is an empty String "".
           *
          String prefix = AccessController.doPrivileged(
                        new GetPropertyAction("impl.prefix", ""));
          try {
              impl = Class.forName("java.net." + prefix + implName).newInstance();
          } catch (ClassNotFoundException e) {
              System.err.println("Class not found: java.net." + prefix +
                                 implName + ":\ncheck impl.prefix property " +
                                 "in your properties file.");
          } catch (InstantiationException e) {
              System.err.println("Could not instantiate: java.net." + prefix +
                                 implName + ":\ncheck impl.prefix property " +
                                 "in your properties file.");
          } catch (IllegalAccessException e) {
              System.err.println("Cannot access class: java.net." + prefix +
                                 implName + ":\ncheck impl.prefix property " +
                                 "in your properties file.");
          }
  
          if (impl == null) {
              try {
                  impl = Class.forName(implName).newInstance();
              } catch (Exception e) {
                  throw new Error("System property impl.prefix incorrect");
              }
          }
  
          return (InetAddressImpl) impl;
      }
      */
      // END Android-removed: Android doesn't load user-provided implementation.
  
      private void readObjectNoData (ObjectInputStream s) throws
                           IOException, ClassNotFoundException {
          // Android-changed: Don't use null to mean the boot classloader.
          if (getClass().getClassLoader() != BOOT_CLASSLOADER) {
              throw new SecurityException ("invalid address type");
          }
      }
  
      // Android-changed: Don't use null to mean the boot classloader.
      private static final ClassLoader BOOT_CLASSLOADER = Object.class.getClassLoader();
  
      private void readObject (ObjectInputStream s) throws
                           IOException, ClassNotFoundException {
          // Android-changed: Don't use null to mean the boot classloader.
          if (getClass().getClassLoader() != BOOT_CLASSLOADER) {
              throw new SecurityException ("invalid address type");
          }
          GetField gf = s.readFields();
          String host = (String)gf.get("hostName", null);
          int address= gf.get("address", 0);
          int family= gf.get("family", 0);
          holder = new InetAddressHolder(host, address, family);
      }
  
      /* needed because the serializable fields no longer exist */
  
      /**
       * @serialField hostName String
       * @serialField address int
       * @serialField family int
       */
      private static final ObjectStreamField[] serialPersistentFields = {
          new ObjectStreamField("hostName", String.class),
          new ObjectStreamField("address", int.class),
          new ObjectStreamField("family", int.class),
      };
  
      private void writeObject (ObjectOutputStream s) throws
                          IOException {
          // Android-changed: Don't use null to mean the boot classloader.
          if (getClass().getClassLoader() != BOOT_CLASSLOADER) {
              throw new SecurityException ("invalid address type");
          }
          PutField pf = s.putFields();
          pf.put("hostName", holder().hostName);
          pf.put("address", holder().address);
          pf.put("family", holder().family);
          s.writeFields();
          s.flush();
      }
  
      static final int NETID_UNSET = 0;
  
      // BEGIN Android-added: Add methods required by frameworks/base.
      // Particularly those required to deal with scope ids.
      /**
       * Returns true if the string is a valid numeric IPv4 or IPv6 address (such as "192.168.0.1").
       *
       * <p>This copes with all forms of address that Java supports, detailed in the
       * {@link InetAddress} class documentation. An empty string is not treated as numeric.
       *
       * @hide used by frameworks/base to ensure that a getAllByName won't cause a DNS lookup.
       * @deprecated Use {@link InetAddressUtils#isNumericAddress(String)} instead, if possible.
       * @throws NullPointerException if the {@code address} is {@code null}.
       */
      @Deprecated
      public static boolean isNumeric(String address) {
          return InetAddressUtils.parseNumericAddressNoThrowStripOptionalBrackets(address) != null;
      }
  
      /**
       * Returns an InetAddress corresponding to the given numeric address (such
       * as {@code "192.168.0.1"} or {@code "2001:4860:800d::68"}).
       *
       * <p>This method will never do a DNS lookup. Non-numeric addresses are errors. Passing either
       * an empty string or a {@code null} as the {@code numericAddress} will return the
       * {@link Inet6Address#LOOPBACK} address.
       *
       * @hide used by frameworks/base's NetworkUtils.numericToInetAddress
       * @throws IllegalArgumentException if {@code numericAddress} is not a numeric address
       * @deprecated Use {@link InetAddressUtils#parseNumericAddress(String)} instead, if possible.
       */
      @Deprecated
      public static InetAddress parseNumericAddress(String numericAddress) {
          if (numericAddress == null || numericAddress.isEmpty()) {
              return Inet6Address.LOOPBACK;
          }
          InetAddress result = InetAddressUtils
                  .parseNumericAddressNoThrowStripOptionalBrackets(numericAddress);
          if (result == null) {
              throw new IllegalArgumentException("Not a numeric address: " + numericAddress);
          }
          return result;
      }
  
      /**
       * Removes all entries from the VM's DNS cache. This does not affect the C library's DNS
       * cache, nor any caching DNS servers between you and the canonical server.
       * @hide
       */
      public static void clearDnsCache() {
          impl.clearAddressCache();
      }
      // END Android-added: Add methods required by frameworks/base.
      // BEGIN Android-added: Support for network (netId)-specific DNS resolution.
      /**
       * Operates identically to {@code getByName} except host resolution is
       * performed on the network designated by {@code netId}.
       *
       * @param host
       *            the hostName to be resolved to an address or {@code null}.
       * @param netId the network to use for host resolution.
       * @return the {@code InetAddress} instance representing the host.
       * @throws UnknownHostException if the address lookup fails.
       * @hide internal use only
       */
      public static InetAddress getByNameOnNet(String host, int netId) throws UnknownHostException {
          return impl.lookupAllHostAddr(host, netId)[0];
      }
  
      /**
       * Operates identically to {@code getAllByName} except host resolution is
       * performed on the network designated by {@code netId}.
       *
       * @param host the hostname or literal IP string to be resolved.
       * @param netId the network to use for host resolution.
       * @return the array of addresses associated with the specified host.
       * @throws UnknownHostException if the address lookup fails.
       * @hide internal use only
       */
      public static InetAddress[] getAllByNameOnNet(String host, int netId) throws UnknownHostException {
          return impl.lookupAllHostAddr(host, netId).clone();
      }
      // END Android-added: Support for network (netId)-specific DNS resolution.
  }
  // BEGIN Android-removed: Android doesn't load user-provided implementation.
  /*
   * Simple factory to create the impl
   *
  class InetAddressImplFactory {
  
      static InetAddressImpl create() {
          return InetAddress.loadImpl(isIPv6Supported() ?
                                      "Inet6AddressImpl" : "Inet4AddressImpl");
      }
  
      static native boolean isIPv6Supported();
  }
  */
  // END Android-removed: Android doesn't load user-provided implementation.
  