/*
 
* Copyright (c) 1995, 2018, 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.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Random;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.ArrayList;
import java.util.ServiceLoader;
import java.security.AccessController;
import java.io.ObjectStreamException;
import java.io.ObjectStreamField;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectInputStream.GetField;
import java.io.ObjectOutputStream;
import java.io.ObjectOutputStream.PutField;
import sun.security.action.*;
import sun.net.InetAddressCachePolicy;
import sun.net.util.IPAddressUtil;
import sun.net.spi.nameservice.*;

/**
 
* 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
     
java.net.InetAddress#getByAddress(byte[])
 
* @see
     
java.net.InetAddress#getByAddress(java.lang.String, byte[])
 
* @see
     
java.net.InetAddress#getAllByName(java.lang.String)
 
* @see
     
java.net.InetAddress#getByName(java.lang.String)
 
* @see
     
java.net.InetAddress#getLocalHost()
 
* @since JDK1.0
 
*/

public
class
InetAddress implements java.io.Serializable {
    
/**
     
* 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;

    
/* 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;
        
}

        
/**
         
* Specifies the address family type, for instance, '1' for IPv4
         
* addresses, and '2' for IPv6 addresses.
         
*/

        
int family;

        
int getFamily() {
            
return family;
        
}
    
}

    
/* Used to store the serializable fields of InetAddress */
    
final transient InetAddressHolder holder;

    
InetAddressHolder holder() {
        
return holder;
    
}

    
/* Used to store the name service provider */
    
private static List<NameService> nameServices = null;

    
/* 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;

    
/*
     
* 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();
    
}

    
/**
     
* 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;
    
}


    
/**
     
* 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.
     
* A typical implementation will use ICMP ECHO REQUESTs if the
     
* privilege can be obtained, otherwise it will try to establish
     
* a TCP connection on port 7 (Echo) of the destination host.
     
* <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);
    
}

    
/**
     
* 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.
     
* A typical implementation will use ICMP ECHO REQUESTs if the
     
* privilege can be obtained, otherwise it will try to establish
     
* a TCP connection on port 7 (Echo) of the destination host.
     
* <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
   
netifthe NetworkInterface through which the
     
*
                    
test will be done, or null for any interface
     
* @param
   
ttlthe 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);
    
}

    
/**
     
* 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() {
        
return getHostName(true);
    
}

    
/**
     
* 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();
    
}

    
/**
     
* 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() {
        
if (canonicalHostName == null) {
            
canonicalHostName =
                
InetAddress.getHostFromNameService(this, true);
        
}
        
return canonicalHostName;
    
}

    
/**
     
* 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.
     
*
     
* @param check make security check if true
     
*
     
* @see SecurityManager#checkConnect
     
*/

    
private static String getHostFromNameService(InetAddress addr, boolean check) {
        
String host = null;
        
for (NameService nameService : nameServices) {
            
try {
                
// first lookup the hostname
                
host = nameService.getHostByAddr(addr.getAddress());

                
/* check to see if calling code is allowed to know
                 
* the hostname for this IP address, ie, connect to the host
                 
*/

                
if (check) {
                    
SecurityManager sec = System.getSecurityManager();
                    
if (sec != null) {
                        
sec.checkConnect(host, -1);
                    
}
                
}

                
/* 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 = InetAddress.getAllByName0(host, check);
                
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;
                
}

                
break;

            
} catch (SecurityException e) {
                
host = addr.getHostAddress();
                
break;
            
} catch (UnknownHostException e) {
                
host = addr.getHostAddress();
                
// let next provider resolve the hostname
            
}
        
}

        
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
   
objthe object to compare against.
     
* @return
  
{@code true} if the objects are the same;
     
*
          
{@code false} otherwise.
     
* @seejava.net.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();
    
}

    
/*
     
* 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);
        
}
    
}

    
/**
     
* 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
  
UnknownHostExceptionif IP address is of illegal length
     
* @since 1.4
     
*/

    
public static InetAddress getByAddress(String host, byte[] addr)
        
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);
                
}
            
}
        
}
        
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}.
     
* @returnan IP address for the given host name.
     
* @exception
  
UnknownHostExceptionif 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 {
        
return InetAddress.getAllByName(host)[0];
    
}

    
// called from deployment cache manager
    
private static InetAddress getByName(String host, InetAddress reqAddr)
        
throws UnknownHostException {
        
return InetAddress.getAllByName(host, reqAddr)[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}.
     
* @returnan array of all the IP addresses for a given host name.
     
*
     
* @exception
  
UnknownHostExceptionif no IP address for the
     
*
               
{@code host} could be found, or if a scope_id was specified
     
*
               
for a global IPv6 address.
     
* @exception
  
SecurityExceptionif 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 {
        
return getAllByName(host, null);
    
}

    
private static InetAddress[] getAllByName(String host, InetAddress reqAddr)
        
throws UnknownHostException {

        
if (host == null || host.length() == 0) {
            
InetAddress[] ret = new InetAddress[1];
            
ret[0] = impl.loopbackAddress();
            
return ret;
        
}

        
boolean ipv6Expected = false;
        
if (host.charAt(0) == '[') {
            
// This is supposed to be an IPv6 literal
            
if (host.length() > 2 && host.charAt(host.length()-1) == ']') {
                
host = host.substring(1, host.length() -1);
                
ipv6Expected = true;
            
} else {
                
// This was supposed to be a IPv6 address, but it's not!
                
throw new UnknownHostException(host + ": invalid IPv6 address");
            
}
        
}

        
// if host is an IP address, we won't do further lookup
        
if (Character.digit(host.charAt(0), 16) != -1
            
|| (host.charAt(0) == ':')) {
            
byte[] addr = null;
            
int numericZone = -1;
            
String ifname = null;
            
// see if it is IPv4 address
            
addr = IPAddressUtil.textToNumericFormatV4(host);
            
if (addr == null) {
                
// This is supposed to be an IPv6 literal
                
// Check if a numeric or string zone id is present
                
int pos;
                
if ((pos=host.indexOf ("%")) != -1) {
                    
numericZone = checkNumericZone (host);
                    
if (numericZone == -1) { /* remainder of string must be an ifname */
                        
ifname = host.substring (pos+1);
                    
}
                
}
                
if ((addr = IPAddressUtil.textToNumericFormatV6(host)) == null && host.contains(":")) {
                    
throw new UnknownHostException(host + ": invalid IPv6 address");
                
}
            
} else if (ipv6Expected) {
                
// Means an IPv4 litteral between brackets!
                
throw new UnknownHostException("["+host+"]");
            
}
            
InetAddress[] ret = new InetAddress[1];
            
if(addr != null) {
                
if (addr.length == Inet4Address.INADDRSZ) {
                    
ret[0] = new Inet4Address(null, addr);
                
} else {
                    
if (ifname != null) {
                        
ret[0] = new Inet6Address(null, addr, ifname);
                    
} else {
                        
ret[0] = new Inet6Address(null, addr, numericZone);
                    
}
                
}
                
return ret;
            
}
        
} else if (ipv6Expected) {
            
// We were expecting an IPv6 Litteral, but got something else
            
throw new UnknownHostException("["+host+"]");
        
}
        
return getAllByName0(host, reqAddr, true);
    
}

    
/**
     
* 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() {
        
return impl.loopbackAddress();
    
}


    
/**
     
* 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();
        
}
    
}

    
/**
     
* 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
  
UnknownHostExceptionif IP address is of illegal length
     
* @since 1.4
     
*/

    
public static InetAddress getByAddress(byte[] addr)
        
throws UnknownHostException {
        
return getByAddress(null, addr);
    
}

    
private static InetAddress cachedLocalHost = null;
    
private static long cacheTime = 0;
    
private static final long maxCacheTime = 5000L;
    
private static final Object cacheLock = new Object();

    
/**
     
* 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.
     
*
     
* @returnthe address of the local host.
     
*
     
* @exception
  
UnknownHostExceptionif the local host name could not
     
*
             
be resolved into an address.
     
*
     
* @see SecurityManager#checkConnect
     
* @see java.net.InetAddress#getByName(java.lang.String)
     
*/

    
public static InetAddress getLocalHost() throws UnknownHostException {

        
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();
        
}
    
}

    
/**
     
* Perform class load-time initializations.
     
*/
    
private static native void init();


    
/*
     
* Returns the InetAddress representing anyLocalAddress
     
* (typically 0.0.0.0 or ::0)
     
*/

    
static InetAddress anyLocalAddress() {
        
return impl.anyLocalAddress();
    
}

    
/*
     
* 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;
    
}

    
private void readObjectNoData (ObjectInputStream s) throws
                         
IOException, ClassNotFoundException {
        
if (getClass().getClassLoader() != null) {
            
throw new SecurityException ("invalid address type");
        
}
    
}

    
private static final long FIELDS_OFFSET;
    
private static final sun.misc.Unsafe UNSAFE;

    
static {
        
try {
            
sun.misc.Unsafe unsafe = sun.misc.Unsafe.getUnsafe();
            
FIELDS_OFFSET = unsafe.objectFieldOffset(
                
InetAddress.class.getDeclaredField("holder")
            
);
            
UNSAFE = unsafe;
        
} catch (ReflectiveOperationException e) {
            
throw new Error(e);
        
}
    
}

    
private void readObject (ObjectInputStream s) throws
                         
IOException, ClassNotFoundException {
        
if (getClass().getClassLoader() != null) {
            
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);
        
if (family != IPv4 && family != IPv6) {
            
throw new InvalidObjectException("invalid address family type: " + family);
        
}
        
InetAddressHolder h = new InetAddressHolder(host, address, family);
        
UNSAFE.putObject(this, FIELDS_OFFSET, h);
    
}

    
/* 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 {
        
if (getClass().getClassLoader() != null) {
            
throw new SecurityException ("invalid address type");
        
}
        
PutField pf = s.putFields();
        
pf.put("hostName", holder().getHostName());
        
pf.put("address", holder().getAddress());
        
pf.put("family", holder().getFamily());
        
s.writeFields();
    
}
}

/*
 
* Simple factory to create the impl
 
*/
class InetAddressImplFactory {

    
static InetAddressImpl create() {
        
return InetAddress.loadImpl(isIPv6Supported() ?
                                    
"Inet6AddressImpl" : "Inet4AddressImpl");
    
}

    
static native boolean isIPv6Supported();
}