/*
    * Copyright (C) 2008 The Guava Authors
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    * http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.google.common.net;
  
  import com.google.common.annotations.Beta;
  import com.google.common.base.MoreObjects;
  import com.google.common.base.Preconditions;
  import com.google.common.hash.Hashing;
  import com.google.common.io.ByteStreams;
  import com.google.common.primitives.Ints;
  
  import java.net.Inet4Address;
  import java.net.Inet6Address;
  import java.net.InetAddress;
  import java.net.UnknownHostException;
  import java.nio.ByteBuffer;
  import java.util.Arrays;
  
  import javax.annotation.Nullable;
  
  /**
   * Static utility methods pertaining to {@link InetAddress} instances.
   *
   * <p><b>Important note:</b> Unlike {@code InetAddress.getByName()}, the
   * methods of this class never cause DNS services to be accessed. For
   * this reason, you should prefer these methods as much as possible over
   * their JDK equivalents whenever you are expecting to handle only
   * IP address string literals -- there is no blocking DNS penalty for a
   * malformed string.
   *
   * <p>When dealing with {@link Inet4Address} and {@link Inet6Address}
   * objects as byte arrays (vis. {@code InetAddress.getAddress()}) they
   * are 4 and 16 bytes in length, respectively, and represent the address
   * in network byte order.
   *
   * <p>Examples of IP addresses and their byte representations:
   * <ul>
   * <li>The IPv4 loopback address, {@code "127.0.0.1"}.<br/>
   *     {@code 7f 00 00 01}
   *
   * <li>The IPv6 loopback address, {@code "::1"}.<br/>
   *     {@code 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01}
   *
   * <li>From the IPv6 reserved documentation prefix ({@code 2001:db8::/32}),
   *     {@code "2001:db8::1"}.<br/>
   *     {@code 20 01 0d b8 00 00 00 00 00 00 00 00 00 00 00 01}
   *
   * <li>An IPv6 "IPv4 compatible" (or "compat") address,
   *     {@code "::192.168.0.1"}.<br/>
   *     {@code 00 00 00 00 00 00 00 00 00 00 00 00 c0 a8 00 01}
   *
   * <li>An IPv6 "IPv4 mapped" address, {@code "::ffff:192.168.0.1"}.<br/>
   *     {@code 00 00 00 00 00 00 00 00 00 00 ff ff c0 a8 00 01}
   * </ul>
   *
   * <p>A few notes about IPv6 "IPv4 mapped" addresses and their observed
   * use in Java.
   * <br><br>
   * "IPv4 mapped" addresses were originally a representation of IPv4
   * addresses for use on an IPv6 socket that could receive both IPv4
   * and IPv6 connections (by disabling the {@code IPV6_V6ONLY} socket
   * option on an IPv6 socket).  Yes, it's confusing.  Nevertheless,
   * these "mapped" addresses were never supposed to be seen on the
   * wire.  That assumption was dropped, some say mistakenly, in later
   * RFCs with the apparent aim of making IPv4-to-IPv6 transition simpler.
   *
   * <p>Technically one <i>can</i> create a 128bit IPv6 address with the wire
   * format of a "mapped" address, as shown above, and transmit it in an
   * IPv6 packet header.  However, Java's InetAddress creation methods
   * appear to adhere doggedly to the original intent of the "mapped"
   * address: all "mapped" addresses return {@link Inet4Address} objects.
   *
   * <p>For added safety, it is common for IPv6 network operators to filter
   * all packets where either the source or destination address appears to
   * be a "compat" or "mapped" address.  Filtering suggestions usually
   * recommend discarding any packets with source or destination addresses
   * in the invalid range {@code ::/3}, which includes both of these bizarre
   * address formats.  For more information on "bogons", including lists
   * of IPv6 bogon space, see:
   *
   * <ul>
   * <li><a target="_parent"
   *        href="http://en.wikipedia.org/wiki/Bogon_filtering"
   *       >http://en.wikipedia.org/wiki/Bogon_filtering</a>;
   * <li><a target="_parent"
  *        href="http://www.cymru.com/Bogons/ipv6.txt"
  *       >http://www.cymru.com/Bogons/ipv6.txt</a>;
  * <li><a target="_parent"
  *        href="http://www.cymru.com/Bogons/v6bogon.html"
  *       >http://www.cymru.com/Bogons/v6bogon.html</a>;
  * <li><a target="_parent"
  *        href="http://www.space.net/~gert/RIPE/ipv6-filters.html"
  *       >http://www.space.net/~gert/RIPE/ipv6-filters.html</a>;
  * </ul>
  *
  * @author Erik Kline
  * @since 5.0
  */
 @Beta
 public final class InetAddresses {
   private static final int IPV4_PART_COUNT = 4;
   private static final int IPV6_PART_COUNT = 8;
   private static final Inet4Address LOOPBACK4 = (Inet4Address) forString("127.0.0.1");
   private static final Inet4Address ANY4 = (Inet4Address) forString("0.0.0.0");
 
   private InetAddresses() {}
 
   /**
    * Returns an {@link Inet4Address}, given a byte array representation of the IPv4 address.
    *
    * @param bytes byte array representing an IPv4 address (should be of length 4)
    * @return {@link Inet4Address} corresponding to the supplied byte array
    * @throws IllegalArgumentException if a valid {@link Inet4Address} can not be created
    */
   private static Inet4Address getInet4Address(byte[] bytes) {
     Preconditions.checkArgument(bytes.length == 4,
         "Byte array has invalid length for an IPv4 address: %s != 4.",
         bytes.length);
 
     // Given a 4-byte array, this cast should always succeed.
     return (Inet4Address) bytesToInetAddress(bytes);
   }
 
   /**
    * Returns the {@link InetAddress} having the given string representation.
    *
    * <p>This deliberately avoids all nameservice lookups (e.g. no DNS).
    *
    * @param ipString {@code String} containing an IPv4 or IPv6 string literal, e.g.
    *     {@code "192.168.0.1"} or {@code "2001:db8::1"}
    * @return {@link InetAddress} representing the argument
    * @throws IllegalArgumentException if the argument is not a valid IP string literal
    */
   public static InetAddress forString(String ipString) {
     byte[] addr = ipStringToBytes(ipString);
 
     // The argument was malformed, i.e. not an IP string literal.
     if (addr == null) {
       throw new IllegalArgumentException(
           String.format("'%s' is not an IP string literal.", ipString));
     }
 
     return bytesToInetAddress(addr);
   }
 
   /**
    * Returns {@code true} if the supplied string is a valid IP string
    * literal, {@code false} otherwise.
    *
    * @param ipString {@code String} to evaluated as an IP string literal
    * @return {@code true} if the argument is a valid IP string literal
    */
   public static boolean isInetAddress(String ipString) {
     return ipStringToBytes(ipString) != null;
   }
 
   private static byte[] ipStringToBytes(String ipString) {
     // Make a first pass to categorize the characters in this string.
     boolean hasColon = false;
     boolean hasDot = false;
     for (int i = 0; i < ipString.length(); i++) {
       char c = ipString.charAt(i);
       if (c == '.') {
         hasDot = true;
       } else if (c == ':') {
         if (hasDot) {
           return null;  // Colons must not appear after dots.
         }
         hasColon = true;
       } else if (Character.digit(c, 16) == -1) {
         return null;  // Everything else must be a decimal or hex digit.
       }
     }
 
     // Now decide which address family to parse.
     if (hasColon) {
       if (hasDot) {
         ipString = convertDottedQuadToHex(ipString);
         if (ipString == null) {
           return null;
         }
       }
       return textToNumericFormatV6(ipString);
     } else if (hasDot) {
       return textToNumericFormatV4(ipString);
     }
     return null;
   }
 
   private static byte[] textToNumericFormatV4(String ipString) {
     String[] address = ipString.split("\\.", IPV4_PART_COUNT + 1);
     if (address.length != IPV4_PART_COUNT) {
       return null;
     }
 
     byte[] bytes = new byte[IPV4_PART_COUNT];
     try {
       for (int i = 0; i < bytes.length; i++) {
         bytes[i] = parseOctet(address[i]);
       }
     } catch (NumberFormatException ex) {
       return null;
     }
 
     return bytes;
   }
 
   private static byte[] textToNumericFormatV6(String ipString) {
     // An address can have [2..8] colons, and N colons make N+1 parts.
     String[] parts = ipString.split(":", IPV6_PART_COUNT + 2);
     if (parts.length < 3 || parts.length > IPV6_PART_COUNT + 1) {
       return null;
     }
 
     // Disregarding the endpoints, find "::" with nothing in between.
     // This indicates that a run of zeroes has been skipped.
     int skipIndex = -1;
     for (int i = 1; i < parts.length - 1; i++) {
       if (parts[i].length() == 0) {
         if (skipIndex >= 0) {
           return null;  // Can't have more than one ::
         }
         skipIndex = i;
       }
     }
 
     int partsHi;  // Number of parts to copy from above/before the "::"
     int partsLo;  // Number of parts to copy from below/after the "::"
     if (skipIndex >= 0) {
       // If we found a "::", then check if it also covers the endpoints.
       partsHi = skipIndex;
       partsLo = parts.length - skipIndex - 1;
       if (parts[0].length() == 0 && --partsHi != 0) {
         return null;  // ^: requires ^::
       }
       if (parts[parts.length - 1].length() == 0 && --partsLo != 0) {
         return null;  // :$ requires ::$
       }
     } else {
       // Otherwise, allocate the entire address to partsHi.  The endpoints
       // could still be empty, but parseHextet() will check for that.
       partsHi = parts.length;
       partsLo = 0;
     }
 
     // If we found a ::, then we must have skipped at least one part.
     // Otherwise, we must have exactly the right number of parts.
     int partsSkipped = IPV6_PART_COUNT - (partsHi + partsLo);
     if (!(skipIndex >= 0 ? partsSkipped >= 1 : partsSkipped == 0)) {
       return null;
     }
 
     // Now parse the hextets into a byte array.
     ByteBuffer rawBytes = ByteBuffer.allocate(2 * IPV6_PART_COUNT);
     try {
       for (int i = 0; i < partsHi; i++) {
         rawBytes.putShort(parseHextet(parts[i]));
       }
       for (int i = 0; i < partsSkipped; i++) {
         rawBytes.putShort((short) 0);
       }
       for (int i = partsLo; i > 0; i--) {
         rawBytes.putShort(parseHextet(parts[parts.length - i]));
       }
     } catch (NumberFormatException ex) {
       return null;
     }
     return rawBytes.array();
   }
 
   private static String convertDottedQuadToHex(String ipString) {
     int lastColon = ipString.lastIndexOf(':');
     String initialPart = ipString.substring(0, lastColon + 1);
     String dottedQuad = ipString.substring(lastColon + 1);
     byte[] quad = textToNumericFormatV4(dottedQuad);
     if (quad == null) {
       return null;
     }
     String penultimate = Integer.toHexString(((quad[0] & 0xff) << 8) | (quad[1] & 0xff));
     String ultimate = Integer.toHexString(((quad[2] & 0xff) << 8) | (quad[3] & 0xff));
     return initialPart + penultimate + ":" + ultimate;
   }
 
   private static byte parseOctet(String ipPart) {
     // Note: we already verified that this string contains only hex digits.
     int octet = Integer.parseInt(ipPart);
     // Disallow leading zeroes, because no clear standard exists on
     // whether these should be interpreted as decimal or octal.
     if (octet > 255 || (ipPart.startsWith("0") && ipPart.length() > 1)) {
       throw new NumberFormatException();
     }
     return (byte) octet;
   }
 
   private static short parseHextet(String ipPart) {
     // Note: we already verified that this string contains only hex digits.
     int hextet = Integer.parseInt(ipPart, 16);
     if (hextet > 0xffff) {
       throw new NumberFormatException();
     }
     return (short) hextet;
   }
 
   /**
    * Convert a byte array into an InetAddress.
    *
    * {@link InetAddress#getByAddress} is documented as throwing a checked
    * exception "if IP address if of illegal length."  We replace it with
    * an unchecked exception, for use by callers who already know that addr
    * is an array of length 4 or 16.
    *
    * @param addr the raw 4-byte or 16-byte IP address in big-endian order
    * @return an InetAddress object created from the raw IP address
    */
   private static InetAddress bytesToInetAddress(byte[] addr) {
     try {
       return InetAddress.getByAddress(addr);
     } catch (UnknownHostException e) {
       throw new AssertionError(e);
     }
   }
 
   /**
    * Returns the string representation of an {@link InetAddress}.
    *
    * <p>For IPv4 addresses, this is identical to
    * {@link InetAddress#getHostAddress()}, but for IPv6 addresses, the output
    * follows <a href="http://tools.ietf.org/html/rfc5952">RFC 5952</a>
    * section 4.  The main difference is that this method uses "::" for zero
    * compression, while Java's version uses the uncompressed form.
    *
    * <p>This method uses hexadecimal for all IPv6 addresses, including
    * IPv4-mapped IPv6 addresses such as "::c000:201".  The output does not
    * include a Scope ID.
    *
    * @param ip {@link InetAddress} to be converted to an address string
    * @return {@code String} containing the text-formatted IP address
    * @since 10.0
    */
   public static String toAddrString(InetAddress ip) {
     Preconditions.checkNotNull(ip);
     if (ip instanceof Inet4Address) {
       // For IPv4, Java's formatting is good enough.
       return ip.getHostAddress();
     }
     Preconditions.checkArgument(ip instanceof Inet6Address);
     byte[] bytes = ip.getAddress();
     int[] hextets = new int[IPV6_PART_COUNT];
     for (int i = 0; i < hextets.length; i++) {
       hextets[i] = Ints.fromBytes(
           (byte) 0, (byte) 0, bytes[2 * i], bytes[2 * i + 1]);
     }
     compressLongestRunOfZeroes(hextets);
     return hextetsToIPv6String(hextets);
   }
 
   /**
    * Identify and mark the longest run of zeroes in an IPv6 address.
    *
    * <p>Only runs of two or more hextets are considered.  In case of a tie, the
    * leftmost run wins.  If a qualifying run is found, its hextets are replaced
    * by the sentinel value -1.
    *
    * @param hextets {@code int[]} mutable array of eight 16-bit hextets
    */
   private static void compressLongestRunOfZeroes(int[] hextets) {
     int bestRunStart = -1;
     int bestRunLength = -1;
     int runStart = -1;
     for (int i = 0; i < hextets.length + 1; i++) {
       if (i < hextets.length && hextets[i] == 0) {
         if (runStart < 0) {
           runStart = i;
         }
       } else if (runStart >= 0) {
         int runLength = i - runStart;
         if (runLength > bestRunLength) {
           bestRunStart = runStart;
           bestRunLength = runLength;
         }
         runStart = -1;
       }
     }
     if (bestRunLength >= 2) {
       Arrays.fill(hextets, bestRunStart, bestRunStart + bestRunLength, -1);
     }
   }
 
   /**
    * Convert a list of hextets into a human-readable IPv6 address.
    *
    * <p>In order for "::" compression to work, the input should contain negative
    * sentinel values in place of the elided zeroes.
    *
    * @param hextets {@code int[]} array of eight 16-bit hextets, or -1s
    */
   private static String hextetsToIPv6String(int[] hextets) {
     /*
      * While scanning the array, handle these state transitions:
      *   start->num => "num"     start->gap => "::"
      *   num->num   => ":num"    num->gap   => "::"
      *   gap->num   => "num"     gap->gap   => ""
      */
     StringBuilder buf = new StringBuilder(39);
     boolean lastWasNumber = false;
     for (int i = 0; i < hextets.length; i++) {
       boolean thisIsNumber = hextets[i] >= 0;
       if (thisIsNumber) {
         if (lastWasNumber) {
           buf.append(':');
         }
         buf.append(Integer.toHexString(hextets[i]));
       } else {
         if (i == 0 || lastWasNumber) {
           buf.append("::");
         }
       }
       lastWasNumber = thisIsNumber;
     }
     return buf.toString();
   }
 
   /**
    * Returns the string representation of an {@link InetAddress} suitable
    * for inclusion in a URI.
    *
    * <p>For IPv4 addresses, this is identical to
    * {@link InetAddress#getHostAddress()}, but for IPv6 addresses it
    * compresses zeroes and surrounds the text with square brackets; for example
    * {@code "[2001:db8::1]"}.
    *
    * <p>Per section 3.2.2 of
    * <a target="_parent"
    *    href="http://tools.ietf.org/html/rfc3986#section-3.2.2"
    *  >http://tools.ietf.org/html/rfc3986</a>,
    * a URI containing an IPv6 string literal is of the form
    * {@code "http://[2001:db8::1]:8888/index.html"}.
    *
    * <p>Use of either {@link InetAddresses#toAddrString},
    * {@link InetAddress#getHostAddress()}, or this method is recommended over
    * {@link InetAddress#toString()} when an IP address string literal is
    * desired.  This is because {@link InetAddress#toString()} prints the
    * hostname and the IP address string joined by a "/".
    *
    * @param ip {@link InetAddress} to be converted to URI string literal
    * @return {@code String} containing URI-safe string literal
    */
   public static String toUriString(InetAddress ip) {
     if (ip instanceof Inet6Address) {
       return "[" + toAddrString(ip) + "]";
     }
     return toAddrString(ip);
   }
 
   /**
    * Returns an InetAddress representing the literal IPv4 or IPv6 host
    * portion of a URL, encoded in the format specified by RFC 3986 section 3.2.2.
    *
    * <p>This function is similar to {@link InetAddresses#forString(String)},
    * however, it requires that IPv6 addresses are surrounded by square brackets.
    *
    * <p>This function is the inverse of
    * {@link InetAddresses#toUriString(java.net.InetAddress)}.
    *
    * @param hostAddr A RFC 3986 section 3.2.2 encoded IPv4 or IPv6 address
    * @return an InetAddress representing the address in {@code hostAddr}
    * @throws IllegalArgumentException if {@code hostAddr} is not a valid
    *     IPv4 address, or IPv6 address surrounded by square brackets
    */
   public static InetAddress forUriString(String hostAddr) {
     Preconditions.checkNotNull(hostAddr);
 
     // Decide if this should be an IPv6 or IPv4 address.
     String ipString;
     int expectBytes;
     if (hostAddr.startsWith("[") && hostAddr.endsWith("]")) {
       ipString = hostAddr.substring(1, hostAddr.length() - 1);
       expectBytes = 16;
     } else {
       ipString = hostAddr;
       expectBytes = 4;
     }
 
     // Parse the address, and make sure the length/version is correct.
     byte[] addr = ipStringToBytes(ipString);
     if (addr == null || addr.length != expectBytes) {
       throw new IllegalArgumentException(
           String.format("Not a valid URI IP literal: '%s'", hostAddr));
     }
 
     return bytesToInetAddress(addr);
   }
 
   /**
    * Returns {@code true} if the supplied string is a valid URI IP string
    * literal, {@code false} otherwise.
    *
    * @param ipString {@code String} to evaluated as an IP URI host string literal
    * @return {@code true} if the argument is a valid IP URI host
    */
   public static boolean isUriInetAddress(String ipString) {
     try {
       forUriString(ipString);
       return true;
     } catch (IllegalArgumentException e) {
       return false;
     }
   }
 
   /**
    * Evaluates whether the argument is an IPv6 "compat" address.
    *
    * <p>An "IPv4 compatible", or "compat", address is one with 96 leading
    * bits of zero, with the remaining 32 bits interpreted as an
    * IPv4 address.  These are conventionally represented in string
    * literals as {@code "::192.168.0.1"}, though {@code "::c0a8:1"} is
    * also considered an IPv4 compatible address (and equivalent to
    * {@code "::192.168.0.1"}).
    *
    * <p>For more on IPv4 compatible addresses see section 2.5.5.1 of
    * <a target="_parent"
    *    href="http://tools.ietf.org/html/rfc4291#section-2.5.5.1"
    *    >http://tools.ietf.org/html/rfc4291</a>;
    *
    * <p>NOTE: This method is different from
    * {@link Inet6Address#isIPv4CompatibleAddress} in that it more
    * correctly classifies {@code "::"} and {@code "::1"} as
    * proper IPv6 addresses (which they are), NOT IPv4 compatible
    * addresses (which they are generally NOT considered to be).
    *
    * @param ip {@link Inet6Address} to be examined for embedded IPv4 compatible address format
    * @return {@code true} if the argument is a valid "compat" address
    */
   public static boolean isCompatIPv4Address(Inet6Address ip) {
     if (!ip.isIPv4CompatibleAddress()) {
       return false;
     }
 
     byte[] bytes = ip.getAddress();
     if ((bytes[12] == 0) && (bytes[13] == 0) && (bytes[14] == 0)
         && ((bytes[15] == 0) || (bytes[15] == 1))) {
       return false;
     }
 
     return true;
   }
 
   /**
    * Returns the IPv4 address embedded in an IPv4 compatible address.
    *
    * @param ip {@link Inet6Address} to be examined for an embedded IPv4 address
    * @return {@link Inet4Address} of the embedded IPv4 address
    * @throws IllegalArgumentException if the argument is not a valid IPv4 compatible address
    */
   public static Inet4Address getCompatIPv4Address(Inet6Address ip) {
     Preconditions.checkArgument(isCompatIPv4Address(ip),
         "Address '%s' is not IPv4-compatible.", toAddrString(ip));
 
     return getInet4Address(Arrays.copyOfRange(ip.getAddress(), 12, 16));
   }
 
   /**
    * Evaluates whether the argument is a 6to4 address.
    *
    * <p>6to4 addresses begin with the {@code "2002::/16"} prefix.
    * The next 32 bits are the IPv4 address of the host to which
    * IPv6-in-IPv4 tunneled packets should be routed.
    *
    * <p>For more on 6to4 addresses see section 2 of
    * <a target="_parent" href="http://tools.ietf.org/html/rfc3056#section-2"
    *    >http://tools.ietf.org/html/rfc3056</a>;
    *
    * @param ip {@link Inet6Address} to be examined for 6to4 address format
    * @return {@code true} if the argument is a 6to4 address
    */
   public static boolean is6to4Address(Inet6Address ip) {
     byte[] bytes = ip.getAddress();
     return (bytes[0] == (byte) 0x20) && (bytes[1] == (byte) 0x02);
   }
 
   /**
    * Returns the IPv4 address embedded in a 6to4 address.
    *
    * @param ip {@link Inet6Address} to be examined for embedded IPv4 in 6to4 address
    * @return {@link Inet4Address} of embedded IPv4 in 6to4 address
    * @throws IllegalArgumentException if the argument is not a valid IPv6 6to4 address
    */
   public static Inet4Address get6to4IPv4Address(Inet6Address ip) {
     Preconditions.checkArgument(is6to4Address(ip),
         "Address '%s' is not a 6to4 address.", toAddrString(ip));
 
     return getInet4Address(Arrays.copyOfRange(ip.getAddress(), 2, 6));
   }
 
   /**
    * A simple immutable data class to encapsulate the information to be found in a
    * Teredo address.
    *
    * <p>All of the fields in this class are encoded in various portions
    * of the IPv6 address as part of the protocol.  More protocols details
    * can be found at:
    * <a target="_parent" href="http://en.wikipedia.org/wiki/Teredo_tunneling"
    *    >http://en.wikipedia.org/wiki/Teredo_tunneling</a>.
    *
    * <p>The RFC can be found here:
    * <a target="_parent" href="http://tools.ietf.org/html/rfc4380"
    *    >http://tools.ietf.org/html/rfc4380</a>.
    *
    * @since 5.0
    */
   @Beta
   public static final class TeredoInfo {
     private final Inet4Address server;
     private final Inet4Address client;
     private final int port;
     private final int flags;
 
     /**
      * Constructs a TeredoInfo instance.
      *
      * <p>Both server and client can be {@code null}, in which case the
      * value {@code "0.0.0.0"} will be assumed.
      *
      * @throws IllegalArgumentException if either of the {@code port} or the {@code flags}
      *     arguments are out of range of an unsigned short
      */
     // TODO: why is this public?
     public TeredoInfo(
         @Nullable Inet4Address server, @Nullable Inet4Address client, int port, int flags) {
       Preconditions.checkArgument((port >= 0) && (port <= 0xffff),
           "port '%s' is out of range (0 <= port <= 0xffff)", port);
       Preconditions.checkArgument((flags >= 0) && (flags <= 0xffff),
           "flags '%s' is out of range (0 <= flags <= 0xffff)", flags);
 
       this.server = MoreObjects.firstNonNull(server, ANY4);
       this.client = MoreObjects.firstNonNull(client, ANY4);
       this.port = port;
       this.flags = flags;
     }
 
     public Inet4Address getServer() {
       return server;
     }
 
     public Inet4Address getClient() {
       return client;
     }
 
     public int getPort() {
       return port;
     }
 
     public int getFlags() {
       return flags;
     }
   }
 
   /**
    * Evaluates whether the argument is a Teredo address.
    *
    * <p>Teredo addresses begin with the {@code "2001::/32"} prefix.
    *
    * @param ip {@link Inet6Address} to be examined for Teredo address format
    * @return {@code true} if the argument is a Teredo address
    */
   public static boolean isTeredoAddress(Inet6Address ip) {
     byte[] bytes = ip.getAddress();
     return (bytes[0] == (byte) 0x20) && (bytes[1] == (byte) 0x01)
            && (bytes[2] == 0) && (bytes[3] == 0);
   }
 
   /**
    * Returns the Teredo information embedded in a Teredo address.
    *
    * @param ip {@link Inet6Address} to be examined for embedded Teredo information
    * @return extracted {@code TeredoInfo}
    * @throws IllegalArgumentException if the argument is not a valid IPv6 Teredo address
    */
   public static TeredoInfo getTeredoInfo(Inet6Address ip) {
     Preconditions.checkArgument(isTeredoAddress(ip),
         "Address '%s' is not a Teredo address.", toAddrString(ip));
 
     byte[] bytes = ip.getAddress();
     Inet4Address server = getInet4Address(Arrays.copyOfRange(bytes, 4, 8));
 
     int flags = ByteStreams.newDataInput(bytes, 8).readShort() & 0xffff;
 
     // Teredo obfuscates the mapped client port, per section 4 of the RFC.
     int port = ~ByteStreams.newDataInput(bytes, 10).readShort() & 0xffff;
 
     byte[] clientBytes = Arrays.copyOfRange(bytes, 12, 16);
     for (int i = 0; i < clientBytes.length; i++) {
       // Teredo obfuscates the mapped client IP, per section 4 of the RFC.
       clientBytes[i] = (byte) ~clientBytes[i];
     }
     Inet4Address client = getInet4Address(clientBytes);
 
     return new TeredoInfo(server, client, port, flags);
   }
 
   /**
    * Evaluates whether the argument is an ISATAP address.
    *
    * <p>From RFC 5214: "ISATAP interface identifiers are constructed in
    * Modified EUI-64 format [...] by concatenating the 24-bit IANA OUI
    * (00-00-5E), the 8-bit hexadecimal value 0xFE, and a 32-bit IPv4
    * address in network byte order [...]"
    *
    * <p>For more on ISATAP addresses see section 6.1 of
    * <a target="_parent" href="http://tools.ietf.org/html/rfc5214#section-6.1"
    *    >http://tools.ietf.org/html/rfc5214</a>;
    *
    * @param ip {@link Inet6Address} to be examined for ISATAP address format
    * @return {@code true} if the argument is an ISATAP address
    */
   public static boolean isIsatapAddress(Inet6Address ip) {
 
     // If it's a Teredo address with the right port (41217, or 0xa101)
     // which would be encoded as 0x5efe then it can't be an ISATAP address.
     if (isTeredoAddress(ip)) {
       return false;
     }
 
     byte[] bytes = ip.getAddress();
 
     if ((bytes[8] | (byte) 0x03) != (byte) 0x03) {
 
       // Verify that high byte of the 64 bit identifier is zero, modulo
       // the U/L and G bits, with which we are not concerned.
       return false;
     }
 
     return (bytes[9] == (byte) 0x00) && (bytes[10] == (byte) 0x5e)
            && (bytes[11] == (byte) 0xfe);
   }
 
   /**
    * Returns the IPv4 address embedded in an ISATAP address.
    *
    * @param ip {@link Inet6Address} to be examined for embedded IPv4 in ISATAP address
    * @return {@link Inet4Address} of embedded IPv4 in an ISATAP address
    * @throws IllegalArgumentException if the argument is not a valid IPv6 ISATAP address
    */
   public static Inet4Address getIsatapIPv4Address(Inet6Address ip) {
     Preconditions.checkArgument(isIsatapAddress(ip),
         "Address '%s' is not an ISATAP address.", toAddrString(ip));
 
     return getInet4Address(Arrays.copyOfRange(ip.getAddress(), 12, 16));
   }
 
   /**
    * Examines the Inet6Address to determine if it is an IPv6 address of one
    * of the specified address types that contain an embedded IPv4 address.
    *
    * <p>NOTE: ISATAP addresses are explicitly excluded from this method
    * due to their trivial spoofability.  With other transition addresses
    * spoofing involves (at least) infection of one's BGP routing table.
    *
    * @param ip {@link Inet6Address} to be examined for embedded IPv4 client address
    * @return {@code true} if there is an embedded IPv4 client address
    * @since 7.0
    */
   public static boolean hasEmbeddedIPv4ClientAddress(Inet6Address ip) {
     return isCompatIPv4Address(ip) || is6to4Address(ip) || isTeredoAddress(ip);
   }
 
   /**
    * Examines the Inet6Address to extract the embedded IPv4 client address
    * if the InetAddress is an IPv6 address of one of the specified address
    * types that contain an embedded IPv4 address.
    *
    * <p>NOTE: ISATAP addresses are explicitly excluded from this method
    * due to their trivial spoofability.  With other transition addresses
    * spoofing involves (at least) infection of one's BGP routing table.
    *
    * @param ip {@link Inet6Address} to be examined for embedded IPv4 client address
    * @return {@link Inet4Address} of embedded IPv4 client address
    * @throws IllegalArgumentException if the argument does not have a valid embedded IPv4 address
    */
   public static Inet4Address getEmbeddedIPv4ClientAddress(Inet6Address ip) {
     if (isCompatIPv4Address(ip)) {
       return getCompatIPv4Address(ip);
     }
 
     if (is6to4Address(ip)) {
       return get6to4IPv4Address(ip);
     }
 
     if (isTeredoAddress(ip)) {
       return getTeredoInfo(ip).getClient();
     }
 
     throw new IllegalArgumentException(
         String.format("'%s' has no embedded IPv4 address.", toAddrString(ip)));
   }
 
   /**
    * Evaluates whether the argument is an "IPv4 mapped" IPv6 address.
    *
    * <p>An "IPv4 mapped" address is anything in the range ::ffff:0:0/96
    * (sometimes written as ::ffff:0.0.0.0/96), with the last 32 bits
    * interpreted as an IPv4 address.
    *
    * <p>For more on IPv4 mapped addresses see section 2.5.5.2 of
    * <a target="_parent"
    *    href="http://tools.ietf.org/html/rfc4291#section-2.5.5.2"
    *    >http://tools.ietf.org/html/rfc4291</a>;
    *
    * <p>Note: This method takes a {@code String} argument because
    * {@link InetAddress} automatically collapses mapped addresses to IPv4.
    * (It is actually possible to avoid this using one of the obscure
    * {@link Inet6Address} methods, but it would be unwise to depend on such
    * a poorly-documented feature.)
    *
    * @param ipString {@code String} to be examined for embedded IPv4-mapped IPv6 address format
    * @return {@code true} if the argument is a valid "mapped" address
    * @since 10.0
    */
   public static boolean isMappedIPv4Address(String ipString) {
     byte[] bytes = ipStringToBytes(ipString);
     if (bytes != null && bytes.length == 16) {
       for (int i = 0; i < 10; i++) {
         if (bytes[i] != 0) {
           return false;
         }
       }
       for (int i = 10; i < 12; i++) {
         if (bytes[i] != (byte) 0xff) {
           return false;
         }
       }
       return true;
     }
     return false;
   }
 
   /**
    * Coerces an IPv6 address into an IPv4 address.
    *
    * <p>HACK: As long as applications continue to use IPv4 addresses for
    * indexing into tables, accounting, et cetera, it may be necessary to
    * <b>coerce</b> IPv6 addresses into IPv4 addresses. This function does
    * so by hashing the upper 64 bits into {@code 224.0.0.0/3}
    * (64 bits into 29 bits).
    *
    * <p>A "coerced" IPv4 address is equivalent to itself.
    *
    * <p>NOTE: This function is failsafe for security purposes: ALL IPv6
    * addresses (except localhost (::1)) are hashed to avoid the security
    * risk associated with extracting an embedded IPv4 address that might
    * permit elevated privileges.
    *
    * @param ip {@link InetAddress} to "coerce"
    * @return {@link Inet4Address} represented "coerced" address
    * @since 7.0
    */
   public static Inet4Address getCoercedIPv4Address(InetAddress ip) {
     if (ip instanceof Inet4Address) {
       return (Inet4Address) ip;
     }
 
     // Special cases:
     byte[] bytes = ip.getAddress();
     boolean leadingBytesOfZero = true;
     for (int i = 0; i < 15; ++i) {
       if (bytes[i] != 0) {
         leadingBytesOfZero = false;
         break;
       }
     }
     if (leadingBytesOfZero && (bytes[15] == 1)) {
       return LOOPBACK4;  // ::1
     } else if (leadingBytesOfZero && (bytes[15] == 0)) {
       return ANY4;  // ::0
     }
 
     Inet6Address ip6 = (Inet6Address) ip;
     long addressAsLong = 0;
     if (hasEmbeddedIPv4ClientAddress(ip6)) {
       addressAsLong = getEmbeddedIPv4ClientAddress(ip6).hashCode();
     } else {
 
       // Just extract the high 64 bits (assuming the rest is user-modifiable).
       addressAsLong = ByteBuffer.wrap(ip6.getAddress(), 0, 8).getLong();
     }
 
     // Many strategies for hashing are possible.  This might suffice for now.
     int coercedHash = Hashing.murmur3_32().hashLong(addressAsLong).asInt();
 
     // Squash into 224/4 Multicast and 240/4 Reserved space (i.e. 224/3).
     coercedHash |= 0xe0000000;
 
     // Fixup to avoid some "illegal" values.  Currently the only potential
     // illegal value is 255.255.255.255.
     if (coercedHash == 0xffffffff) {
       coercedHash = 0xfffffffe;
     }
 
     return getInet4Address(Ints.toByteArray(coercedHash));
   }
 
   /**
    * Returns an integer representing an IPv4 address regardless of
    * whether the supplied argument is an IPv4 address or not.
    *
    * <p>IPv6 addresses are <b>coerced</b> to IPv4 addresses before being
    * converted to integers.
    *
    * <p>As long as there are applications that assume that all IP addresses
    * are IPv4 addresses and can therefore be converted safely to integers
    * (for whatever purpose) this function can be used to handle IPv6
    * addresses as well until the application is suitably fixed.
    *
    * <p>NOTE: an IPv6 address coerced to an IPv4 address can only be used
    * for such purposes as rudimentary identification or indexing into a
    * collection of real {@link InetAddress}es.  They cannot be used as
    * real addresses for the purposes of network communication.
    *
    * @param ip {@link InetAddress} to convert
    * @return {@code int}, "coerced" if ip is not an IPv4 address
    * @since 7.0
    */
   public static int coerceToInteger(InetAddress ip) {
     return ByteStreams.newDataInput(getCoercedIPv4Address(ip).getAddress()).readInt();
   }
 
   /**
    * Returns an Inet4Address having the integer value specified by
    * the argument.
    *
    * @param address {@code int}, the 32bit integer address to be converted
    * @return {@link Inet4Address} equivalent of the argument
    */
   public static Inet4Address fromInteger(int address) {
     return getInet4Address(Ints.toByteArray(address));
   }
 
   /**
    * Returns an address from a <b>little-endian ordered</b> byte array
    * (the opposite of what {@link InetAddress#getByAddress} expects).
    *
    * <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 little-endian byte order
    * @return an InetAddress object created from the raw IP address
    * @throws UnknownHostException if IP address is of illegal length
    */
   public static InetAddress fromLittleEndianByteArray(byte[] addr) throws UnknownHostException {
     byte[] reversed = new byte[addr.length];
     for (int i = 0; i < addr.length; i++) {
       reversed[i] = addr[addr.length - i - 1];
     }
     return InetAddress.getByAddress(reversed);
   }
 
   /**
    * Returns a new InetAddress that is one less than the passed in address.
    * This method works for both IPv4 and IPv6 addresses.
    *
    * @param address the InetAddress to decrement
    * @return a new InetAddress that is one less than the passed in address
    * @throws IllegalArgumentException if InetAddress is at the beginning of its range
    * @since 18.0
    */
   public static InetAddress decrement(InetAddress address) {
     byte[] addr = address.getAddress();
     int i = addr.length - 1;
     while (i >= 0 && addr[i] == (byte) 0x00) {
       addr[i] = (byte) 0xff;
       i--;
     }
 
     Preconditions.checkArgument(i >= 0, "Decrementing %s would wrap.", address);
 
     addr[i]--;
     return bytesToInetAddress(addr);
   }
 
   /**
    * Returns a new InetAddress that is one more than the passed in address.
    * This method works for both IPv4 and IPv6 addresses.
    *
    * @param address the InetAddress to increment
    * @return a new InetAddress that is one more than the passed in address
    * @throws IllegalArgumentException if InetAddress is at the end of its range
    * @since 10.0
    */
   public static InetAddress increment(InetAddress address) {
     byte[] addr = address.getAddress();
     int i = addr.length - 1;
     while (i >= 0 && addr[i] == (byte) 0xff) {
       addr[i] = 0;
       i--;
     }
 
     Preconditions.checkArgument(i >= 0, "Incrementing %s would wrap.", address);
 
     addr[i]++;
     return bytesToInetAddress(addr);
   }
 
   /**
    * Returns true if the InetAddress is either 255.255.255.255 for IPv4 or
    * ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff for IPv6.
    *
    * @return true if the InetAddress is either 255.255.255.255 for IPv4 or
    *     ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff for IPv6
    * @since 10.0
    */
   public static boolean isMaximum(InetAddress address) {
     byte[] addr = address.getAddress();
     for (int i = 0; i < addr.length; i++) {
       if (addr[i] != (byte) 0xff) {
         return false;
       }
     }
     return true;
   }
 }