001/*
002 * Copyright (C) 2008 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.net;
016
017import static com.google.common.base.Preconditions.checkArgument;
018import static com.google.common.base.Preconditions.checkNotNull;
019
020import com.google.common.annotations.Beta;
021import com.google.common.annotations.GwtIncompatible;
022import com.google.common.base.CharMatcher;
023import com.google.common.base.MoreObjects;
024import com.google.common.hash.Hashing;
025import com.google.common.io.ByteStreams;
026import com.google.common.primitives.Ints;
027import java.math.BigInteger;
028import java.net.Inet4Address;
029import java.net.Inet6Address;
030import java.net.InetAddress;
031import java.net.UnknownHostException;
032import java.nio.ByteBuffer;
033import java.util.Arrays;
034import java.util.Locale;
035import javax.annotation.CheckForNull;
036
037/**
038 * Static utility methods pertaining to {@link InetAddress} instances.
039 *
040 * <p><b>Important note:</b> Unlike {@code InetAddress.getByName()}, the methods of this class never
041 * cause DNS services to be accessed. For this reason, you should prefer these methods as much as
042 * possible over their JDK equivalents whenever you are expecting to handle only IP address string
043 * literals -- there is no blocking DNS penalty for a malformed string.
044 *
045 * <p>When dealing with {@link Inet4Address} and {@link Inet6Address} objects as byte arrays (vis.
046 * {@code InetAddress.getAddress()}) they are 4 and 16 bytes in length, respectively, and represent
047 * the address in network byte order.
048 *
049 * <p>Examples of IP addresses and their byte representations:
050 *
051 * <dl>
052 *   <dt>The IPv4 loopback address, {@code "127.0.0.1"}.
053 *   <dd>{@code 7f 00 00 01}
054 *   <dt>The IPv6 loopback address, {@code "::1"}.
055 *   <dd>{@code 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01}
056 *   <dt>From the IPv6 reserved documentation prefix ({@code 2001:db8::/32}), {@code "2001:db8::1"}.
057 *   <dd>{@code 20 01 0d b8 00 00 00 00 00 00 00 00 00 00 00 01}
058 *   <dt>An IPv6 "IPv4 compatible" (or "compat") address, {@code "::192.168.0.1"}.
059 *   <dd>{@code 00 00 00 00 00 00 00 00 00 00 00 00 c0 a8 00 01}
060 *   <dt>An IPv6 "IPv4 mapped" address, {@code "::ffff:192.168.0.1"}.
061 *   <dd>{@code 00 00 00 00 00 00 00 00 00 00 ff ff c0 a8 00 01}
062 * </dl>
063 *
064 * <p>A few notes about IPv6 "IPv4 mapped" addresses and their observed use in Java.
065 *
066 * <p>"IPv4 mapped" addresses were originally a representation of IPv4 addresses for use on an IPv6
067 * socket that could receive both IPv4 and IPv6 connections (by disabling the {@code IPV6_V6ONLY}
068 * socket option on an IPv6 socket). Yes, it's confusing. Nevertheless, these "mapped" addresses
069 * were never supposed to be seen on the wire. That assumption was dropped, some say mistakenly, in
070 * later RFCs with the apparent aim of making IPv4-to-IPv6 transition simpler.
071 *
072 * <p>Technically one <i>can</i> create a 128bit IPv6 address with the wire format of a "mapped"
073 * address, as shown above, and transmit it in an IPv6 packet header. However, Java's InetAddress
074 * creation methods appear to adhere doggedly to the original intent of the "mapped" address: all
075 * "mapped" addresses return {@link Inet4Address} objects.
076 *
077 * <p>For added safety, it is common for IPv6 network operators to filter all packets where either
078 * the source or destination address appears to be a "compat" or "mapped" address. Filtering
079 * suggestions usually recommend discarding any packets with source or destination addresses in the
080 * invalid range {@code ::/3}, which includes both of these bizarre address formats. For more
081 * information on "bogons", including lists of IPv6 bogon space, see:
082 *
083 * <ul>
084 *   <li><a target="_parent"
085 *       href="http://en.wikipedia.org/wiki/Bogon_filtering">http://en.wikipedia.
086 *       org/wiki/Bogon_filtering</a>
087 *   <li><a target="_parent"
088 *       href="http://www.cymru.com/Bogons/ipv6.txt">http://www.cymru.com/Bogons/ ipv6.txt</a>
089 *   <li><a target="_parent" href="http://www.cymru.com/Bogons/v6bogon.html">http://www.cymru.com/
090 *       Bogons/v6bogon.html</a>
091 *   <li><a target="_parent" href="http://www.space.net/~gert/RIPE/ipv6-filters.html">http://www.
092 *       space.net/~gert/RIPE/ipv6-filters.html</a>
093 * </ul>
094 *
095 * @author Erik Kline
096 * @since 5.0
097 */
098@Beta
099@GwtIncompatible
100@ElementTypesAreNonnullByDefault
101public final class InetAddresses {
102  private static final int IPV4_PART_COUNT = 4;
103  private static final int IPV6_PART_COUNT = 8;
104  private static final char IPV4_DELIMITER = '.';
105  private static final char IPV6_DELIMITER = ':';
106  private static final CharMatcher IPV4_DELIMITER_MATCHER = CharMatcher.is(IPV4_DELIMITER);
107  private static final CharMatcher IPV6_DELIMITER_MATCHER = CharMatcher.is(IPV6_DELIMITER);
108  private static final Inet4Address LOOPBACK4 = (Inet4Address) forString("127.0.0.1");
109  private static final Inet4Address ANY4 = (Inet4Address) forString("0.0.0.0");
110
111  private InetAddresses() {}
112
113  /**
114   * Returns an {@link Inet4Address}, given a byte array representation of the IPv4 address.
115   *
116   * @param bytes byte array representing an IPv4 address (should be of length 4)
117   * @return {@link Inet4Address} corresponding to the supplied byte array
118   * @throws IllegalArgumentException if a valid {@link Inet4Address} can not be created
119   */
120  private static Inet4Address getInet4Address(byte[] bytes) {
121    checkArgument(
122        bytes.length == 4,
123        "Byte array has invalid length for an IPv4 address: %s != 4.",
124        bytes.length);
125
126    // Given a 4-byte array, this cast should always succeed.
127    return (Inet4Address) bytesToInetAddress(bytes);
128  }
129
130  /**
131   * Returns the {@link InetAddress} having the given string representation.
132   *
133   * <p>This deliberately avoids all nameservice lookups (e.g. no DNS).
134   *
135   * <p>Anything after a {@code %} in an IPv6 address is ignored (assumed to be a Scope ID).
136   *
137   * <p>This method accepts non-ASCII digits, for example {@code "192.168.0.1"} (those are fullwidth
138   * characters). That is consistent with {@link InetAddress}, but not with various RFCs. If you
139   * want to accept ASCII digits only, you can use something like {@code
140   * CharMatcher.ascii().matchesAllOf(ipString)}.
141   *
142   * @param ipString {@code String} containing an IPv4 or IPv6 string literal, e.g. {@code
143   *     "192.168.0.1"} or {@code "2001:db8::1"}
144   * @return {@link InetAddress} representing the argument
145   * @throws IllegalArgumentException if the argument is not a valid IP string literal
146   */
147  public static InetAddress forString(String ipString) {
148    byte[] addr = ipStringToBytes(ipString);
149
150    // The argument was malformed, i.e. not an IP string literal.
151    if (addr == null) {
152      throw formatIllegalArgumentException("'%s' is not an IP string literal.", ipString);
153    }
154
155    return bytesToInetAddress(addr);
156  }
157
158  /**
159   * Returns {@code true} if the supplied string is a valid IP string literal, {@code false}
160   * otherwise.
161   *
162   * <p>This method accepts non-ASCII digits, for example {@code "192.168.0.1"} (those are fullwidth
163   * characters). That is consistent with {@link InetAddress}, but not with various RFCs. If you
164   * want to accept ASCII digits only, you can use something like {@code
165   * CharMatcher.ascii().matchesAllOf(ipString)}.
166   *
167   * @param ipString {@code String} to evaluated as an IP string literal
168   * @return {@code true} if the argument is a valid IP string literal
169   */
170  public static boolean isInetAddress(String ipString) {
171    return ipStringToBytes(ipString) != null;
172  }
173
174  /** Returns {@code null} if unable to parse into a {@code byte[]}. */
175  @CheckForNull
176  private static byte[] ipStringToBytes(String ipStringParam) {
177    String ipString = ipStringParam;
178    // Make a first pass to categorize the characters in this string.
179    boolean hasColon = false;
180    boolean hasDot = false;
181    int percentIndex = -1;
182    for (int i = 0; i < ipString.length(); i++) {
183      char c = ipString.charAt(i);
184      if (c == '.') {
185        hasDot = true;
186      } else if (c == ':') {
187        if (hasDot) {
188          return null; // Colons must not appear after dots.
189        }
190        hasColon = true;
191      } else if (c == '%') {
192        percentIndex = i;
193        break; // everything after a '%' is ignored (it's a Scope ID): http://superuser.com/a/99753
194      } else if (Character.digit(c, 16) == -1) {
195        return null; // Everything else must be a decimal or hex digit.
196      }
197    }
198
199    // Now decide which address family to parse.
200    if (hasColon) {
201      if (hasDot) {
202        ipString = convertDottedQuadToHex(ipString);
203        if (ipString == null) {
204          return null;
205        }
206      }
207      if (percentIndex != -1) {
208        ipString = ipString.substring(0, percentIndex);
209      }
210      return textToNumericFormatV6(ipString);
211    } else if (hasDot) {
212      if (percentIndex != -1) {
213        return null; // Scope IDs are not supported for IPV4
214      }
215      return textToNumericFormatV4(ipString);
216    }
217    return null;
218  }
219
220  @CheckForNull
221  private static byte[] textToNumericFormatV4(String ipString) {
222    if (IPV4_DELIMITER_MATCHER.countIn(ipString) + 1 != IPV4_PART_COUNT) {
223      return null; // Wrong number of parts
224    }
225
226    byte[] bytes = new byte[IPV4_PART_COUNT];
227    int start = 0;
228    // Iterate through the parts of the ip string.
229    // Invariant: start is always the beginning of an octet.
230    for (int i = 0; i < IPV4_PART_COUNT; i++) {
231      int end = ipString.indexOf(IPV4_DELIMITER, start);
232      if (end == -1) {
233        end = ipString.length();
234      }
235      try {
236        bytes[i] = parseOctet(ipString, start, end);
237      } catch (NumberFormatException ex) {
238        return null;
239      }
240      start = end + 1;
241    }
242
243    return bytes;
244  }
245
246  @CheckForNull
247  private static byte[] textToNumericFormatV6(String ipString) {
248    // An address can have [2..8] colons.
249    int delimiterCount = IPV6_DELIMITER_MATCHER.countIn(ipString);
250    if (delimiterCount < 2 || delimiterCount > IPV6_PART_COUNT) {
251      return null;
252    }
253    int partsSkipped = IPV6_PART_COUNT - (delimiterCount + 1); // estimate; may be modified later
254    boolean hasSkip = false;
255    // Scan for the appearance of ::, to mark a skip-format IPV6 string and adjust the partsSkipped
256    // estimate.
257    for (int i = 0; i < ipString.length() - 1; i++) {
258      if (ipString.charAt(i) == IPV6_DELIMITER && ipString.charAt(i + 1) == IPV6_DELIMITER) {
259        if (hasSkip) {
260          return null; // Can't have more than one ::
261        }
262        hasSkip = true;
263        partsSkipped++; // :: means we skipped an extra part in between the two delimiters.
264        if (i == 0) {
265          partsSkipped++; // Begins with ::, so we skipped the part preceding the first :
266        }
267        if (i == ipString.length() - 2) {
268          partsSkipped++; // Ends with ::, so we skipped the part after the last :
269        }
270      }
271    }
272    if (ipString.charAt(0) == IPV6_DELIMITER && ipString.charAt(1) != IPV6_DELIMITER) {
273      return null; // ^: requires ^::
274    }
275    if (ipString.charAt(ipString.length() - 1) == IPV6_DELIMITER
276        && ipString.charAt(ipString.length() - 2) != IPV6_DELIMITER) {
277      return null; // :$ requires ::$
278    }
279    if (hasSkip && partsSkipped <= 0) {
280      return null; // :: must expand to at least one '0'
281    }
282    if (!hasSkip && delimiterCount + 1 != IPV6_PART_COUNT) {
283      return null; // Incorrect number of parts
284    }
285
286    ByteBuffer rawBytes = ByteBuffer.allocate(2 * IPV6_PART_COUNT);
287    try {
288      // Iterate through the parts of the ip string.
289      // Invariant: start is always the beginning of a hextet, or the second ':' of the skip
290      // sequence "::"
291      int start = 0;
292      if (ipString.charAt(0) == IPV6_DELIMITER) {
293        start = 1;
294      }
295      while (start < ipString.length()) {
296        int end = ipString.indexOf(IPV6_DELIMITER, start);
297        if (end == -1) {
298          end = ipString.length();
299        }
300        if (ipString.charAt(start) == IPV6_DELIMITER) {
301          // expand zeroes
302          for (int i = 0; i < partsSkipped; i++) {
303            rawBytes.putShort((short) 0);
304          }
305
306        } else {
307          rawBytes.putShort(parseHextet(ipString, start, end));
308        }
309        start = end + 1;
310      }
311    } catch (NumberFormatException ex) {
312      return null;
313    }
314    return rawBytes.array();
315  }
316
317  @CheckForNull
318  private static String convertDottedQuadToHex(String ipString) {
319    int lastColon = ipString.lastIndexOf(':');
320    String initialPart = ipString.substring(0, lastColon + 1);
321    String dottedQuad = ipString.substring(lastColon + 1);
322    byte[] quad = textToNumericFormatV4(dottedQuad);
323    if (quad == null) {
324      return null;
325    }
326    String penultimate = Integer.toHexString(((quad[0] & 0xff) << 8) | (quad[1] & 0xff));
327    String ultimate = Integer.toHexString(((quad[2] & 0xff) << 8) | (quad[3] & 0xff));
328    return initialPart + penultimate + ":" + ultimate;
329  }
330
331  private static byte parseOctet(String ipString, int start, int end) {
332    // Note: we already verified that this string contains only hex digits, but the string may still
333    // contain non-decimal characters.
334    int length = end - start;
335    if (length <= 0 || length > 3) {
336      throw new NumberFormatException();
337    }
338    // Disallow leading zeroes, because no clear standard exists on
339    // whether these should be interpreted as decimal or octal.
340    if (length > 1 && ipString.charAt(start) == '0') {
341      throw new NumberFormatException();
342    }
343    int octet = 0;
344    for (int i = start; i < end; i++) {
345      octet *= 10;
346      int digit = Character.digit(ipString.charAt(i), 10);
347      if (digit < 0) {
348        throw new NumberFormatException();
349      }
350      octet += digit;
351    }
352    if (octet > 255) {
353      throw new NumberFormatException();
354    }
355    return (byte) octet;
356  }
357
358  // Parse a hextet out of the ipString from start (inclusive) to end (exclusive)
359  private static short parseHextet(String ipString, int start, int end) {
360    // Note: we already verified that this string contains only hex digits.
361    int length = end - start;
362    if (length <= 0 || length > 4) {
363      throw new NumberFormatException();
364    }
365    int hextet = 0;
366    for (int i = start; i < end; i++) {
367      hextet = hextet << 4;
368      hextet |= Character.digit(ipString.charAt(i), 16);
369    }
370    return (short) hextet;
371  }
372
373  /**
374   * Convert a byte array into an InetAddress.
375   *
376   * <p>{@link InetAddress#getByAddress} is documented as throwing a checked exception "if IP
377   * address is of illegal length." We replace it with an unchecked exception, for use by callers
378   * who already know that addr is an array of length 4 or 16.
379   *
380   * @param addr the raw 4-byte or 16-byte IP address in big-endian order
381   * @return an InetAddress object created from the raw IP address
382   */
383  private static InetAddress bytesToInetAddress(byte[] addr) {
384    try {
385      return InetAddress.getByAddress(addr);
386    } catch (UnknownHostException e) {
387      throw new AssertionError(e);
388    }
389  }
390
391  /**
392   * Returns the string representation of an {@link InetAddress}.
393   *
394   * <p>For IPv4 addresses, this is identical to {@link InetAddress#getHostAddress()}, but for IPv6
395   * addresses, the output follows <a href="http://tools.ietf.org/html/rfc5952">RFC 5952</a> section
396   * 4. The main difference is that this method uses "::" for zero compression, while Java's version
397   * uses the uncompressed form.
398   *
399   * <p>This method uses hexadecimal for all IPv6 addresses, including IPv4-mapped IPv6 addresses
400   * such as "::c000:201". The output does not include a Scope ID.
401   *
402   * @param ip {@link InetAddress} to be converted to an address string
403   * @return {@code String} containing the text-formatted IP address
404   * @since 10.0
405   */
406  public static String toAddrString(InetAddress ip) {
407    checkNotNull(ip);
408    if (ip instanceof Inet4Address) {
409      // For IPv4, Java's formatting is good enough.
410      return ip.getHostAddress();
411    }
412    checkArgument(ip instanceof Inet6Address);
413    byte[] bytes = ip.getAddress();
414    int[] hextets = new int[IPV6_PART_COUNT];
415    for (int i = 0; i < hextets.length; i++) {
416      hextets[i] = Ints.fromBytes((byte) 0, (byte) 0, bytes[2 * i], bytes[2 * i + 1]);
417    }
418    compressLongestRunOfZeroes(hextets);
419    return hextetsToIPv6String(hextets);
420  }
421
422  /**
423   * Identify and mark the longest run of zeroes in an IPv6 address.
424   *
425   * <p>Only runs of two or more hextets are considered. In case of a tie, the leftmost run wins. If
426   * a qualifying run is found, its hextets are replaced by the sentinel value -1.
427   *
428   * @param hextets {@code int[]} mutable array of eight 16-bit hextets
429   */
430  private static void compressLongestRunOfZeroes(int[] hextets) {
431    int bestRunStart = -1;
432    int bestRunLength = -1;
433    int runStart = -1;
434    for (int i = 0; i < hextets.length + 1; i++) {
435      if (i < hextets.length && hextets[i] == 0) {
436        if (runStart < 0) {
437          runStart = i;
438        }
439      } else if (runStart >= 0) {
440        int runLength = i - runStart;
441        if (runLength > bestRunLength) {
442          bestRunStart = runStart;
443          bestRunLength = runLength;
444        }
445        runStart = -1;
446      }
447    }
448    if (bestRunLength >= 2) {
449      Arrays.fill(hextets, bestRunStart, bestRunStart + bestRunLength, -1);
450    }
451  }
452
453  /**
454   * Convert a list of hextets into a human-readable IPv6 address.
455   *
456   * <p>In order for "::" compression to work, the input should contain negative sentinel values in
457   * place of the elided zeroes.
458   *
459   * @param hextets {@code int[]} array of eight 16-bit hextets, or -1s
460   */
461  private static String hextetsToIPv6String(int[] hextets) {
462    // While scanning the array, handle these state transitions:
463    //   start->num => "num"     start->gap => "::"
464    //   num->num   => ":num"    num->gap   => "::"
465    //   gap->num   => "num"     gap->gap   => ""
466    StringBuilder buf = new StringBuilder(39);
467    boolean lastWasNumber = false;
468    for (int i = 0; i < hextets.length; i++) {
469      boolean thisIsNumber = hextets[i] >= 0;
470      if (thisIsNumber) {
471        if (lastWasNumber) {
472          buf.append(':');
473        }
474        buf.append(Integer.toHexString(hextets[i]));
475      } else {
476        if (i == 0 || lastWasNumber) {
477          buf.append("::");
478        }
479      }
480      lastWasNumber = thisIsNumber;
481    }
482    return buf.toString();
483  }
484
485  /**
486   * Returns the string representation of an {@link InetAddress} suitable for inclusion in a URI.
487   *
488   * <p>For IPv4 addresses, this is identical to {@link InetAddress#getHostAddress()}, but for IPv6
489   * addresses it compresses zeroes and surrounds the text with square brackets; for example {@code
490   * "[2001:db8::1]"}.
491   *
492   * <p>Per section 3.2.2 of <a target="_parent"
493   * href="http://tools.ietf.org/html/rfc3986#section-3.2.2">RFC 3986</a>, a URI containing an IPv6
494   * string literal is of the form {@code "http://[2001:db8::1]:8888/index.html"}.
495   *
496   * <p>Use of either {@link InetAddresses#toAddrString}, {@link InetAddress#getHostAddress()}, or
497   * this method is recommended over {@link InetAddress#toString()} when an IP address string
498   * literal is desired. This is because {@link InetAddress#toString()} prints the hostname and the
499   * IP address string joined by a "/".
500   *
501   * @param ip {@link InetAddress} to be converted to URI string literal
502   * @return {@code String} containing URI-safe string literal
503   */
504  public static String toUriString(InetAddress ip) {
505    if (ip instanceof Inet6Address) {
506      return "[" + toAddrString(ip) + "]";
507    }
508    return toAddrString(ip);
509  }
510
511  /**
512   * Returns an InetAddress representing the literal IPv4 or IPv6 host portion of a URL, encoded in
513   * the format specified by RFC 3986 section 3.2.2.
514   *
515   * <p>This method is similar to {@link InetAddresses#forString(String)}, however, it requires that
516   * IPv6 addresses are surrounded by square brackets.
517   *
518   * <p>This method is the inverse of {@link InetAddresses#toUriString(java.net.InetAddress)}.
519   *
520   * <p>This method accepts non-ASCII digits, for example {@code "192.168.0.1"} (those are fullwidth
521   * characters). That is consistent with {@link InetAddress}, but not with various RFCs. If you
522   * want to accept ASCII digits only, you can use something like {@code
523   * CharMatcher.ascii().matchesAllOf(ipString)}.
524   *
525   * @param hostAddr A RFC 3986 section 3.2.2 encoded IPv4 or IPv6 address
526   * @return an InetAddress representing the address in {@code hostAddr}
527   * @throws IllegalArgumentException if {@code hostAddr} is not a valid IPv4 address, or IPv6
528   *     address surrounded by square brackets
529   */
530  public static InetAddress forUriString(String hostAddr) {
531    InetAddress addr = forUriStringNoThrow(hostAddr);
532    if (addr == null) {
533      throw formatIllegalArgumentException("Not a valid URI IP literal: '%s'", hostAddr);
534    }
535
536    return addr;
537  }
538
539  @CheckForNull
540  private static InetAddress forUriStringNoThrow(String hostAddr) {
541    checkNotNull(hostAddr);
542
543    // Decide if this should be an IPv6 or IPv4 address.
544    String ipString;
545    int expectBytes;
546    if (hostAddr.startsWith("[") && hostAddr.endsWith("]")) {
547      ipString = hostAddr.substring(1, hostAddr.length() - 1);
548      expectBytes = 16;
549    } else {
550      ipString = hostAddr;
551      expectBytes = 4;
552    }
553
554    // Parse the address, and make sure the length/version is correct.
555    byte[] addr = ipStringToBytes(ipString);
556    if (addr == null || addr.length != expectBytes) {
557      return null;
558    }
559
560    return bytesToInetAddress(addr);
561  }
562
563  /**
564   * Returns {@code true} if the supplied string is a valid URI IP string literal, {@code false}
565   * otherwise.
566   *
567   * <p>This method accepts non-ASCII digits, for example {@code "192.168.0.1"} (those are fullwidth
568   * characters). That is consistent with {@link InetAddress}, but not with various RFCs. If you
569   * want to accept ASCII digits only, you can use something like {@code
570   * CharMatcher.ascii().matchesAllOf(ipString)}.
571   *
572   * @param ipString {@code String} to evaluated as an IP URI host string literal
573   * @return {@code true} if the argument is a valid IP URI host
574   */
575  public static boolean isUriInetAddress(String ipString) {
576    return forUriStringNoThrow(ipString) != null;
577  }
578
579  /**
580   * Evaluates whether the argument is an IPv6 "compat" address.
581   *
582   * <p>An "IPv4 compatible", or "compat", address is one with 96 leading bits of zero, with the
583   * remaining 32 bits interpreted as an IPv4 address. These are conventionally represented in
584   * string literals as {@code "::192.168.0.1"}, though {@code "::c0a8:1"} is also considered an
585   * IPv4 compatible address (and equivalent to {@code "::192.168.0.1"}).
586   *
587   * <p>For more on IPv4 compatible addresses see section 2.5.5.1 of <a target="_parent"
588   * href="http://tools.ietf.org/html/rfc4291#section-2.5.5.1">RFC 4291</a>.
589   *
590   * <p>NOTE: This method is different from {@link Inet6Address#isIPv4CompatibleAddress} in that it
591   * more correctly classifies {@code "::"} and {@code "::1"} as proper IPv6 addresses (which they
592   * are), NOT IPv4 compatible addresses (which they are generally NOT considered to be).
593   *
594   * @param ip {@link Inet6Address} to be examined for embedded IPv4 compatible address format
595   * @return {@code true} if the argument is a valid "compat" address
596   */
597  public static boolean isCompatIPv4Address(Inet6Address ip) {
598    if (!ip.isIPv4CompatibleAddress()) {
599      return false;
600    }
601
602    byte[] bytes = ip.getAddress();
603    if ((bytes[12] == 0)
604        && (bytes[13] == 0)
605        && (bytes[14] == 0)
606        && ((bytes[15] == 0) || (bytes[15] == 1))) {
607      return false;
608    }
609
610    return true;
611  }
612
613  /**
614   * Returns the IPv4 address embedded in an IPv4 compatible address.
615   *
616   * @param ip {@link Inet6Address} to be examined for an embedded IPv4 address
617   * @return {@link Inet4Address} of the embedded IPv4 address
618   * @throws IllegalArgumentException if the argument is not a valid IPv4 compatible address
619   */
620  public static Inet4Address getCompatIPv4Address(Inet6Address ip) {
621    checkArgument(
622        isCompatIPv4Address(ip), "Address '%s' is not IPv4-compatible.", toAddrString(ip));
623
624    return getInet4Address(Arrays.copyOfRange(ip.getAddress(), 12, 16));
625  }
626
627  /**
628   * Evaluates whether the argument is a 6to4 address.
629   *
630   * <p>6to4 addresses begin with the {@code "2002::/16"} prefix. The next 32 bits are the IPv4
631   * address of the host to which IPv6-in-IPv4 tunneled packets should be routed.
632   *
633   * <p>For more on 6to4 addresses see section 2 of <a target="_parent"
634   * href="http://tools.ietf.org/html/rfc3056#section-2">RFC 3056</a>.
635   *
636   * @param ip {@link Inet6Address} to be examined for 6to4 address format
637   * @return {@code true} if the argument is a 6to4 address
638   */
639  public static boolean is6to4Address(Inet6Address ip) {
640    byte[] bytes = ip.getAddress();
641    return (bytes[0] == (byte) 0x20) && (bytes[1] == (byte) 0x02);
642  }
643
644  /**
645   * Returns the IPv4 address embedded in a 6to4 address.
646   *
647   * @param ip {@link Inet6Address} to be examined for embedded IPv4 in 6to4 address
648   * @return {@link Inet4Address} of embedded IPv4 in 6to4 address
649   * @throws IllegalArgumentException if the argument is not a valid IPv6 6to4 address
650   */
651  public static Inet4Address get6to4IPv4Address(Inet6Address ip) {
652    checkArgument(is6to4Address(ip), "Address '%s' is not a 6to4 address.", toAddrString(ip));
653
654    return getInet4Address(Arrays.copyOfRange(ip.getAddress(), 2, 6));
655  }
656
657  /**
658   * A simple immutable data class to encapsulate the information to be found in a Teredo address.
659   *
660   * <p>All of the fields in this class are encoded in various portions of the IPv6 address as part
661   * of the protocol. More protocols details can be found at: <a target="_parent"
662   * href="http://en.wikipedia.org/wiki/Teredo_tunneling">http://en.wikipedia.
663   * org/wiki/Teredo_tunneling</a>.
664   *
665   * <p>The RFC can be found here: <a target="_parent" href="http://tools.ietf.org/html/rfc4380">RFC
666   * 4380</a>.
667   *
668   * @since 5.0
669   */
670  @Beta
671  public static final class TeredoInfo {
672    private final Inet4Address server;
673    private final Inet4Address client;
674    private final int port;
675    private final int flags;
676
677    /**
678     * Constructs a TeredoInfo instance.
679     *
680     * <p>Both server and client can be {@code null}, in which case the value {@code "0.0.0.0"} will
681     * be assumed.
682     *
683     * @throws IllegalArgumentException if either of the {@code port} or the {@code flags} arguments
684     *     are out of range of an unsigned short
685     */
686    // TODO: why is this public?
687    public TeredoInfo(
688        @CheckForNull Inet4Address server, @CheckForNull Inet4Address client, int port, int flags) {
689      checkArgument(
690          (port >= 0) && (port <= 0xffff), "port '%s' is out of range (0 <= port <= 0xffff)", port);
691      checkArgument(
692          (flags >= 0) && (flags <= 0xffff),
693          "flags '%s' is out of range (0 <= flags <= 0xffff)",
694          flags);
695
696      this.server = MoreObjects.firstNonNull(server, ANY4);
697      this.client = MoreObjects.firstNonNull(client, ANY4);
698      this.port = port;
699      this.flags = flags;
700    }
701
702    public Inet4Address getServer() {
703      return server;
704    }
705
706    public Inet4Address getClient() {
707      return client;
708    }
709
710    public int getPort() {
711      return port;
712    }
713
714    public int getFlags() {
715      return flags;
716    }
717  }
718
719  /**
720   * Evaluates whether the argument is a Teredo address.
721   *
722   * <p>Teredo addresses begin with the {@code "2001::/32"} prefix.
723   *
724   * @param ip {@link Inet6Address} to be examined for Teredo address format
725   * @return {@code true} if the argument is a Teredo address
726   */
727  public static boolean isTeredoAddress(Inet6Address ip) {
728    byte[] bytes = ip.getAddress();
729    return (bytes[0] == (byte) 0x20)
730        && (bytes[1] == (byte) 0x01)
731        && (bytes[2] == 0)
732        && (bytes[3] == 0);
733  }
734
735  /**
736   * Returns the Teredo information embedded in a Teredo address.
737   *
738   * @param ip {@link Inet6Address} to be examined for embedded Teredo information
739   * @return extracted {@code TeredoInfo}
740   * @throws IllegalArgumentException if the argument is not a valid IPv6 Teredo address
741   */
742  public static TeredoInfo getTeredoInfo(Inet6Address ip) {
743    checkArgument(isTeredoAddress(ip), "Address '%s' is not a Teredo address.", toAddrString(ip));
744
745    byte[] bytes = ip.getAddress();
746    Inet4Address server = getInet4Address(Arrays.copyOfRange(bytes, 4, 8));
747
748    int flags = ByteStreams.newDataInput(bytes, 8).readShort() & 0xffff;
749
750    // Teredo obfuscates the mapped client port, per section 4 of the RFC.
751    int port = ~ByteStreams.newDataInput(bytes, 10).readShort() & 0xffff;
752
753    byte[] clientBytes = Arrays.copyOfRange(bytes, 12, 16);
754    for (int i = 0; i < clientBytes.length; i++) {
755      // Teredo obfuscates the mapped client IP, per section 4 of the RFC.
756      clientBytes[i] = (byte) ~clientBytes[i];
757    }
758    Inet4Address client = getInet4Address(clientBytes);
759
760    return new TeredoInfo(server, client, port, flags);
761  }
762
763  /**
764   * Evaluates whether the argument is an ISATAP address.
765   *
766   * <p>From RFC 5214: "ISATAP interface identifiers are constructed in Modified EUI-64 format [...]
767   * by concatenating the 24-bit IANA OUI (00-00-5E), the 8-bit hexadecimal value 0xFE, and a 32-bit
768   * IPv4 address in network byte order [...]"
769   *
770   * <p>For more on ISATAP addresses see section 6.1 of <a target="_parent"
771   * href="http://tools.ietf.org/html/rfc5214#section-6.1">RFC 5214</a>.
772   *
773   * @param ip {@link Inet6Address} to be examined for ISATAP address format
774   * @return {@code true} if the argument is an ISATAP address
775   */
776  public static boolean isIsatapAddress(Inet6Address ip) {
777
778    // If it's a Teredo address with the right port (41217, or 0xa101)
779    // which would be encoded as 0x5efe then it can't be an ISATAP address.
780    if (isTeredoAddress(ip)) {
781      return false;
782    }
783
784    byte[] bytes = ip.getAddress();
785
786    if ((bytes[8] | (byte) 0x03) != (byte) 0x03) {
787
788      // Verify that high byte of the 64 bit identifier is zero, modulo
789      // the U/L and G bits, with which we are not concerned.
790      return false;
791    }
792
793    return (bytes[9] == (byte) 0x00) && (bytes[10] == (byte) 0x5e) && (bytes[11] == (byte) 0xfe);
794  }
795
796  /**
797   * Returns the IPv4 address embedded in an ISATAP address.
798   *
799   * @param ip {@link Inet6Address} to be examined for embedded IPv4 in ISATAP address
800   * @return {@link Inet4Address} of embedded IPv4 in an ISATAP address
801   * @throws IllegalArgumentException if the argument is not a valid IPv6 ISATAP address
802   */
803  public static Inet4Address getIsatapIPv4Address(Inet6Address ip) {
804    checkArgument(isIsatapAddress(ip), "Address '%s' is not an ISATAP address.", toAddrString(ip));
805
806    return getInet4Address(Arrays.copyOfRange(ip.getAddress(), 12, 16));
807  }
808
809  /**
810   * Examines the Inet6Address to determine if it is an IPv6 address of one of the specified address
811   * types that contain an embedded IPv4 address.
812   *
813   * <p>NOTE: ISATAP addresses are explicitly excluded from this method due to their trivial
814   * spoofability. With other transition addresses spoofing involves (at least) infection of one's
815   * BGP routing table.
816   *
817   * @param ip {@link Inet6Address} to be examined for embedded IPv4 client address
818   * @return {@code true} if there is an embedded IPv4 client address
819   * @since 7.0
820   */
821  public static boolean hasEmbeddedIPv4ClientAddress(Inet6Address ip) {
822    return isCompatIPv4Address(ip) || is6to4Address(ip) || isTeredoAddress(ip);
823  }
824
825  /**
826   * Examines the Inet6Address to extract the embedded IPv4 client address if the InetAddress is an
827   * IPv6 address of one of the specified address types that contain an embedded IPv4 address.
828   *
829   * <p>NOTE: ISATAP addresses are explicitly excluded from this method due to their trivial
830   * spoofability. With other transition addresses spoofing involves (at least) infection of one's
831   * BGP routing table.
832   *
833   * @param ip {@link Inet6Address} to be examined for embedded IPv4 client address
834   * @return {@link Inet4Address} of embedded IPv4 client address
835   * @throws IllegalArgumentException if the argument does not have a valid embedded IPv4 address
836   */
837  public static Inet4Address getEmbeddedIPv4ClientAddress(Inet6Address ip) {
838    if (isCompatIPv4Address(ip)) {
839      return getCompatIPv4Address(ip);
840    }
841
842    if (is6to4Address(ip)) {
843      return get6to4IPv4Address(ip);
844    }
845
846    if (isTeredoAddress(ip)) {
847      return getTeredoInfo(ip).getClient();
848    }
849
850    throw formatIllegalArgumentException("'%s' has no embedded IPv4 address.", toAddrString(ip));
851  }
852
853  /**
854   * Evaluates whether the argument is an "IPv4 mapped" IPv6 address.
855   *
856   * <p>An "IPv4 mapped" address is anything in the range ::ffff:0:0/96 (sometimes written as
857   * ::ffff:0.0.0.0/96), with the last 32 bits interpreted as an IPv4 address.
858   *
859   * <p>For more on IPv4 mapped addresses see section 2.5.5.2 of <a target="_parent"
860   * href="http://tools.ietf.org/html/rfc4291#section-2.5.5.2">RFC 4291</a>.
861   *
862   * <p>Note: This method takes a {@code String} argument because {@link InetAddress} automatically
863   * collapses mapped addresses to IPv4. (It is actually possible to avoid this using one of the
864   * obscure {@link Inet6Address} methods, but it would be unwise to depend on such a
865   * poorly-documented feature.)
866   *
867   * <p>This method accepts non-ASCII digits. That is consistent with {@link InetAddress}, but not
868   * with various RFCs. If you want to accept ASCII digits only, you can use something like {@code
869   * CharMatcher.ascii().matchesAllOf(ipString)}.
870   *
871   * @param ipString {@code String} to be examined for embedded IPv4-mapped IPv6 address format
872   * @return {@code true} if the argument is a valid "mapped" address
873   * @since 10.0
874   */
875  public static boolean isMappedIPv4Address(String ipString) {
876    byte[] bytes = ipStringToBytes(ipString);
877    if (bytes != null && bytes.length == 16) {
878      for (int i = 0; i < 10; i++) {
879        if (bytes[i] != 0) {
880          return false;
881        }
882      }
883      for (int i = 10; i < 12; i++) {
884        if (bytes[i] != (byte) 0xff) {
885          return false;
886        }
887      }
888      return true;
889    }
890    return false;
891  }
892
893  /**
894   * Coerces an IPv6 address into an IPv4 address.
895   *
896   * <p>HACK: As long as applications continue to use IPv4 addresses for indexing into tables,
897   * accounting, et cetera, it may be necessary to <b>coerce</b> IPv6 addresses into IPv4 addresses.
898   * This method does so by hashing 64 bits of the IPv6 address into {@code 224.0.0.0/3} (64 bits
899   * into 29 bits):
900   *
901   * <ul>
902   *   <li>If the IPv6 address contains an embedded IPv4 address, the function hashes that.
903   *   <li>Otherwise, it hashes the upper 64 bits of the IPv6 address.
904   * </ul>
905   *
906   * <p>A "coerced" IPv4 address is equivalent to itself.
907   *
908   * <p>NOTE: This method is failsafe for security purposes: ALL IPv6 addresses (except localhost
909   * (::1)) are hashed to avoid the security risk associated with extracting an embedded IPv4
910   * address that might permit elevated privileges.
911   *
912   * @param ip {@link InetAddress} to "coerce"
913   * @return {@link Inet4Address} represented "coerced" address
914   * @since 7.0
915   */
916  public static Inet4Address getCoercedIPv4Address(InetAddress ip) {
917    if (ip instanceof Inet4Address) {
918      return (Inet4Address) ip;
919    }
920
921    // Special cases:
922    byte[] bytes = ip.getAddress();
923    boolean leadingBytesOfZero = true;
924    for (int i = 0; i < 15; ++i) {
925      if (bytes[i] != 0) {
926        leadingBytesOfZero = false;
927        break;
928      }
929    }
930    if (leadingBytesOfZero && (bytes[15] == 1)) {
931      return LOOPBACK4; // ::1
932    } else if (leadingBytesOfZero && (bytes[15] == 0)) {
933      return ANY4; // ::0
934    }
935
936    Inet6Address ip6 = (Inet6Address) ip;
937    long addressAsLong = 0;
938    if (hasEmbeddedIPv4ClientAddress(ip6)) {
939      addressAsLong = getEmbeddedIPv4ClientAddress(ip6).hashCode();
940    } else {
941      // Just extract the high 64 bits (assuming the rest is user-modifiable).
942      addressAsLong = ByteBuffer.wrap(ip6.getAddress(), 0, 8).getLong();
943    }
944
945    // Many strategies for hashing are possible. This might suffice for now.
946    int coercedHash = Hashing.murmur3_32_fixed().hashLong(addressAsLong).asInt();
947
948    // Squash into 224/4 Multicast and 240/4 Reserved space (i.e. 224/3).
949    coercedHash |= 0xe0000000;
950
951    // Fixup to avoid some "illegal" values. Currently the only potential
952    // illegal value is 255.255.255.255.
953    if (coercedHash == 0xffffffff) {
954      coercedHash = 0xfffffffe;
955    }
956
957    return getInet4Address(Ints.toByteArray(coercedHash));
958  }
959
960  /**
961   * Returns an integer representing an IPv4 address regardless of whether the supplied argument is
962   * an IPv4 address or not.
963   *
964   * <p>IPv6 addresses are <b>coerced</b> to IPv4 addresses before being converted to integers.
965   *
966   * <p>As long as there are applications that assume that all IP addresses are IPv4 addresses and
967   * can therefore be converted safely to integers (for whatever purpose) this function can be used
968   * to handle IPv6 addresses as well until the application is suitably fixed.
969   *
970   * <p>NOTE: an IPv6 address coerced to an IPv4 address can only be used for such purposes as
971   * rudimentary identification or indexing into a collection of real {@link InetAddress}es. They
972   * cannot be used as real addresses for the purposes of network communication.
973   *
974   * @param ip {@link InetAddress} to convert
975   * @return {@code int}, "coerced" if ip is not an IPv4 address
976   * @since 7.0
977   */
978  public static int coerceToInteger(InetAddress ip) {
979    return ByteStreams.newDataInput(getCoercedIPv4Address(ip).getAddress()).readInt();
980  }
981
982  /**
983   * Returns a BigInteger representing the address.
984   *
985   * <p>Unlike {@code coerceToInteger}, IPv6 addresses are not coerced to IPv4 addresses.
986   *
987   * @param address {@link InetAddress} to convert
988   * @return {@code BigInteger} representation of the address
989   * @since 28.2
990   */
991  public static BigInteger toBigInteger(InetAddress address) {
992    return new BigInteger(1, address.getAddress());
993  }
994
995  /**
996   * Returns an Inet4Address having the integer value specified by the argument.
997   *
998   * @param address {@code int}, the 32bit integer address to be converted
999   * @return {@link Inet4Address} equivalent of the argument
1000   */
1001  public static Inet4Address fromInteger(int address) {
1002    return getInet4Address(Ints.toByteArray(address));
1003  }
1004
1005  /**
1006   * Returns the {@code Inet4Address} corresponding to a given {@code BigInteger}.
1007   *
1008   * @param address BigInteger representing the IPv4 address
1009   * @return Inet4Address representation of the given BigInteger
1010   * @throws IllegalArgumentException if the BigInteger is not between 0 and 2^32-1
1011   * @since 28.2
1012   */
1013  public static Inet4Address fromIPv4BigInteger(BigInteger address) {
1014    return (Inet4Address) fromBigInteger(address, false);
1015  }
1016  /**
1017   * Returns the {@code Inet6Address} corresponding to a given {@code BigInteger}.
1018   *
1019   * @param address BigInteger representing the IPv6 address
1020   * @return Inet6Address representation of the given BigInteger
1021   * @throws IllegalArgumentException if the BigInteger is not between 0 and 2^128-1
1022   * @since 28.2
1023   */
1024  public static Inet6Address fromIPv6BigInteger(BigInteger address) {
1025    return (Inet6Address) fromBigInteger(address, true);
1026  }
1027
1028  /**
1029   * Converts a BigInteger to either an IPv4 or IPv6 address. If the IP is IPv4, it must be
1030   * constrainted to 32 bits, otherwise it is constrained to 128 bits.
1031   *
1032   * @param address the address represented as a big integer
1033   * @param isIpv6 whether the created address should be IPv4 or IPv6
1034   * @return the BigInteger converted to an address
1035   * @throws IllegalArgumentException if the BigInteger is not between 0 and maximum value for IPv4
1036   *     or IPv6 respectively
1037   */
1038  private static InetAddress fromBigInteger(BigInteger address, boolean isIpv6) {
1039    checkArgument(address.signum() >= 0, "BigInteger must be greater than or equal to 0");
1040
1041    int numBytes = isIpv6 ? 16 : 4;
1042
1043    byte[] addressBytes = address.toByteArray();
1044    byte[] targetCopyArray = new byte[numBytes];
1045
1046    int srcPos = Math.max(0, addressBytes.length - numBytes);
1047    int copyLength = addressBytes.length - srcPos;
1048    int destPos = numBytes - copyLength;
1049
1050    // Check the extra bytes in the BigInteger are all zero.
1051    for (int i = 0; i < srcPos; i++) {
1052      if (addressBytes[i] != 0x00) {
1053        throw formatIllegalArgumentException(
1054            "BigInteger cannot be converted to InetAddress because it has more than %d"
1055                + " bytes: %s",
1056            numBytes, address);
1057      }
1058    }
1059
1060    // Copy the bytes into the least significant positions.
1061    System.arraycopy(addressBytes, srcPos, targetCopyArray, destPos, copyLength);
1062
1063    try {
1064      return InetAddress.getByAddress(targetCopyArray);
1065    } catch (UnknownHostException impossible) {
1066      throw new AssertionError(impossible);
1067    }
1068  }
1069
1070  /**
1071   * Returns an address from a <b>little-endian ordered</b> byte array (the opposite of what {@link
1072   * InetAddress#getByAddress} expects).
1073   *
1074   * <p>IPv4 address byte array must be 4 bytes long and IPv6 byte array must be 16 bytes long.
1075   *
1076   * @param addr the raw IP address in little-endian byte order
1077   * @return an InetAddress object created from the raw IP address
1078   * @throws UnknownHostException if IP address is of illegal length
1079   */
1080  public static InetAddress fromLittleEndianByteArray(byte[] addr) throws UnknownHostException {
1081    byte[] reversed = new byte[addr.length];
1082    for (int i = 0; i < addr.length; i++) {
1083      reversed[i] = addr[addr.length - i - 1];
1084    }
1085    return InetAddress.getByAddress(reversed);
1086  }
1087
1088  /**
1089   * Returns a new InetAddress that is one less than the passed in address. This method works for
1090   * both IPv4 and IPv6 addresses.
1091   *
1092   * @param address the InetAddress to decrement
1093   * @return a new InetAddress that is one less than the passed in address
1094   * @throws IllegalArgumentException if InetAddress is at the beginning of its range
1095   * @since 18.0
1096   */
1097  public static InetAddress decrement(InetAddress address) {
1098    byte[] addr = address.getAddress();
1099    int i = addr.length - 1;
1100    while (i >= 0 && addr[i] == (byte) 0x00) {
1101      addr[i] = (byte) 0xff;
1102      i--;
1103    }
1104
1105    checkArgument(i >= 0, "Decrementing %s would wrap.", address);
1106
1107    addr[i]--;
1108    return bytesToInetAddress(addr);
1109  }
1110
1111  /**
1112   * Returns a new InetAddress that is one more than the passed in address. This method works for
1113   * both IPv4 and IPv6 addresses.
1114   *
1115   * @param address the InetAddress to increment
1116   * @return a new InetAddress that is one more than the passed in address
1117   * @throws IllegalArgumentException if InetAddress is at the end of its range
1118   * @since 10.0
1119   */
1120  public static InetAddress increment(InetAddress address) {
1121    byte[] addr = address.getAddress();
1122    int i = addr.length - 1;
1123    while (i >= 0 && addr[i] == (byte) 0xff) {
1124      addr[i] = 0;
1125      i--;
1126    }
1127
1128    checkArgument(i >= 0, "Incrementing %s would wrap.", address);
1129
1130    addr[i]++;
1131    return bytesToInetAddress(addr);
1132  }
1133
1134  /**
1135   * Returns true if the InetAddress is either 255.255.255.255 for IPv4 or
1136   * ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff for IPv6.
1137   *
1138   * @return true if the InetAddress is either 255.255.255.255 for IPv4 or
1139   *     ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff for IPv6
1140   * @since 10.0
1141   */
1142  public static boolean isMaximum(InetAddress address) {
1143    byte[] addr = address.getAddress();
1144    for (byte b : addr) {
1145      if (b != (byte) 0xff) {
1146        return false;
1147      }
1148    }
1149    return true;
1150  }
1151
1152  private static IllegalArgumentException formatIllegalArgumentException(
1153      String format, Object... args) {
1154    return new IllegalArgumentException(String.format(Locale.ROOT, format, args));
1155  }
1156}