summaryrefslogtreecommitdiff
path: root/includes/IP.php
blob: 50d57583fb86848ba36706ccd95a159b14cd6773 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
<?php
/**
 * Functions and constants to play with IP addresses and ranges
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @author Ashar Voultoiz <hashar at free dot fr>, Aaron Schulz
 */

// Some regex definition to "play" with IP address and IP address blocks

// An IPv4 address is made of 4 bytes from x00 to xFF which is d0 to d255
define( 'RE_IP_BYTE', '(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|0?[0-9]?[0-9])' );
define( 'RE_IP_ADD', RE_IP_BYTE . '\.' . RE_IP_BYTE . '\.' . RE_IP_BYTE . '\.' . RE_IP_BYTE );
// An IPv4 block is an IP address and a prefix (d1 to d32)
define( 'RE_IP_PREFIX', '(3[0-2]|[12]?\d)' );
define( 'RE_IP_BLOCK', RE_IP_ADD . '\/' . RE_IP_PREFIX );

// An IPv6 address is made up of 8 words (each x0000 to xFFFF).
// However, the "::" abbreviation can be used on consecutive x0000 words.
define( 'RE_IPV6_WORD', '([0-9A-Fa-f]{1,4})' );
define( 'RE_IPV6_PREFIX', '(12[0-8]|1[01][0-9]|[1-9]?\d)');
define( 'RE_IPV6_ADD',
	'(?:' . // starts with "::" (including "::")
		':(?::|(?::' . RE_IPV6_WORD . '){1,7})' .
	'|' . // ends with "::" (except "::")
		RE_IPV6_WORD . '(?::' . RE_IPV6_WORD . '){0,6}::' .
	'|' . // contains one "::" in the middle, ending in "::WORD"
		RE_IPV6_WORD . '(?::' . RE_IPV6_WORD . '){0,5}' . '::' . RE_IPV6_WORD .
	'|' . // contains one "::" in the middle, not ending in "::WORD" (regex for PCRE 4.0+)
		RE_IPV6_WORD . '(?::(?P<abn>:(?P<iabn>))?' . RE_IPV6_WORD . '(?!:(?P=abn))){1,5}' .
			':' . RE_IPV6_WORD . '(?P=iabn)' .
		// NOTE: (?!(?P=abn)) fails iff "::" used twice; (?P=iabn) passes iff a "::" was found.
	'|' . // contains no "::"
		RE_IPV6_WORD . '(?::' . RE_IPV6_WORD . '){7}' .
	')'
	// NOTE: With PCRE 7.2+, we can combine the two '"::" in the middle' cases into:
	//		RE_IPV6_WORD . '(?::((?(-1)|:))?' . RE_IPV6_WORD . '){1,6}(?(-2)|^)'
	// This also improves regex concatenation by using relative references.
);
// An IPv6 block is an IP address and a prefix (d1 to d128)
define( 'RE_IPV6_BLOCK', RE_IPV6_ADD . '\/' . RE_IPV6_PREFIX );
// For IPv6 canonicalization (NOT for strict validation; these are quite lax!)
define( 'RE_IPV6_GAP', ':(?:0+:)*(?::(?:0+:)*)?' );
define( 'RE_IPV6_V4_PREFIX', '0*' . RE_IPV6_GAP . '(?:ffff:)?' );

// This might be useful for regexps used elsewhere, matches any IPv6 or IPv6 address or network
define( 'IP_ADDRESS_STRING',
	'(?:' .
		RE_IP_ADD . '(?:\/' . RE_IP_PREFIX . ')?' . // IPv4
	'|' .
		RE_IPV6_ADD . '(?:\/' . RE_IPV6_PREFIX . ')?' . // IPv6
	')'
);

/**
 * A collection of public static functions to play with IP address
 * and IP blocks.
 */
class IP {
	/**
	 * Determine if a string is as valid IP address or network (CIDR prefix).
	 * SIIT IPv4-translated addresses are rejected.
	 * Note: canonicalize() tries to convert translated addresses to IPv4.
	 *
	 * @param $ip String: possible IP address
	 * @return Boolean
	 */
	public static function isIPAddress( $ip ) {
		return (bool)preg_match( '/^' . IP_ADDRESS_STRING . '$/', $ip );
	}

	/**
	 * Given a string, determine if it as valid IP in IPv6 only.
	 * Note: Unlike isValid(), this looks for networks too.
	 *
	 * @param $ip String: possible IP address
	 * @return Boolean
	 */
	public static function isIPv6( $ip ) {
		return (bool)preg_match( '/^' . RE_IPV6_ADD . '(?:\/' . RE_IPV6_PREFIX . ')?$/', $ip );
	}

	/**
	 * Given a string, determine if it as valid IP in IPv4 only.
	 * Note: Unlike isValid(), this looks for networks too.
	 *
	 * @param $ip String: possible IP address
	 * @return Boolean
	 */
	public static function isIPv4( $ip ) {
		return (bool)preg_match( '/^' . RE_IP_ADD . '(?:\/' . RE_IP_PREFIX . ')?$/', $ip );
	}

	/**
	 * Validate an IP address. Ranges are NOT considered valid.
	 * SIIT IPv4-translated addresses are rejected.
	 * Note: canonicalize() tries to convert translated addresses to IPv4.
	 *
	 * @param $ip String
	 * @return Boolean: True if it is valid.
	 */
	public static function isValid( $ip ) {
		return ( preg_match( '/^' . RE_IP_ADD . '$/', $ip )
			|| preg_match( '/^' . RE_IPV6_ADD . '$/', $ip ) );
	}

	/**
	 * Validate an IP Block (valid address WITH a valid prefix).
	 * SIIT IPv4-translated addresses are rejected.
	 * Note: canonicalize() tries to convert translated addresses to IPv4.
	 *
	 * @param $ipblock String
	 * @return Boolean: True if it is valid.
	 */
	public static function isValidBlock( $ipblock ) {
		return ( preg_match( '/^' . RE_IPV6_BLOCK . '$/', $ipblock )
			|| preg_match( '/^' . RE_IP_BLOCK . '$/', $ipblock ) );
	}

	/**
	 * Convert an IP into a nice standard form.
	 * IPv6 addresses in octet notation are expanded to 8 words.
	 * IPv4 addresses are just trimmed.
	 *
	 * @param $ip String: IP address in quad or octet form (CIDR or not).
	 * @return String
	 */
	public static function sanitizeIP( $ip ) {
		$ip = trim( $ip );
		if ( $ip === '' ) {
			return null;
		}
		if ( self::isIPv4( $ip ) || !self::isIPv6( $ip ) ) {
			return $ip; // nothing else to do for IPv4 addresses or invalid ones
		}
		// Remove any whitespaces, convert to upper case
		$ip = strtoupper( $ip );
		// Expand zero abbreviations
		$abbrevPos = strpos( $ip, '::' );
		if ( $abbrevPos !== false ) {
			// We know this is valid IPv6. Find the last index of the
			// address before any CIDR number (e.g. "a:b:c::/24").
			$CIDRStart = strpos( $ip, "/" );
			$addressEnd = ( $CIDRStart !== false )
				? $CIDRStart - 1
				: strlen( $ip ) - 1;
			// If the '::' is at the beginning...
			if ( $abbrevPos == 0 ) {
				$repeat = '0:';
				$extra = ( $ip == '::' ) ? '0' : ''; // for the address '::'
				$pad = 9; // 7+2 (due to '::')
			// If the '::' is at the end...
			} elseif ( $abbrevPos == ( $addressEnd - 1 ) ) {
				$repeat = ':0';
				$extra = '';
				$pad = 9; // 7+2 (due to '::')
			// If the '::' is in the middle...
			} else {
				$repeat = ':0';
				$extra = ':';
				$pad = 8; // 6+2 (due to '::')
			}
			$ip = str_replace( '::',
				str_repeat( $repeat, $pad - substr_count( $ip, ':' ) ) . $extra,
				$ip
			);
		}
		// Remove leading zereos from each bloc as needed
		$ip = preg_replace( '/(^|:)0+(' . RE_IPV6_WORD . ')/', '$1$2', $ip );
		return $ip;
	}

	/**
	 * Given an unsigned integer, returns an IPv6 address in octet notation
	 *
	 * @param $ip_int String: IP address.
	 * @return String
	 */
	public static function toOctet( $ip_int ) {
		return self::hexToOctet( wfBaseConvert( $ip_int, 10, 16, 32, false ) );
	}

	/**
	 * Convert an IPv4 or IPv6 hexadecimal representation back to readable format
	 *
	 * @param $hex String: number, with "v6-" prefix if it is IPv6
	 * @return String: quad-dotted (IPv4) or octet notation (IPv6)
	 */
	public static function formatHex( $hex ) {
		if ( substr( $hex, 0, 3 ) == 'v6-' ) { // IPv6
			return self::hexToOctet( substr( $hex, 3 ) );
		} else { // IPv4
			return self::hexToQuad( $hex );
		}
	}

	/**
	 * Converts a hexadecimal number to an IPv6 address in octet notation
	 *
	 * @param $ip_hex String: pure hex (no v6- prefix)
	 * @return String (of format a:b:c:d:e:f:g:h)
	 */
	public static function hexToOctet( $ip_hex ) {
		// Pad hex to 32 chars (128 bits)
		$ip_hex = str_pad( strtoupper( $ip_hex ), 32, '0', STR_PAD_LEFT );
		// Separate into 8 words
		$ip_oct = substr( $ip_hex, 0, 4 );
		for ( $n = 1; $n < 8; $n++ ) {
			$ip_oct .= ':' . substr( $ip_hex, 4 * $n, 4 );
		}
		// NO leading zeroes
		$ip_oct = preg_replace( '/(^|:)0+(' . RE_IPV6_WORD . ')/', '$1$2', $ip_oct );
		return $ip_oct;
	}

	/**
	 * Converts a hexadecimal number to an IPv4 address in quad-dotted notation
	 *
	 * @param $ip_hex String: pure hex
	 * @return String (of format a.b.c.d)
	 */
	public static function hexToQuad( $ip_hex ) {
		// Pad hex to 8 chars (32 bits)
		$ip_hex = str_pad( strtoupper( $ip_hex ), 8, '0', STR_PAD_LEFT );
		// Separate into four quads
		$s = '';
		for ( $i = 0; $i < 4; $i++ ) {
			if ( $s !== '' ) {
				$s .= '.';
			}
			$s .= base_convert( substr( $ip_hex, $i * 2, 2 ), 16, 10 );
		}
		return $s;
	}

	/**
	 * Determine if an IP address really is an IP address, and if it is public,
	 * i.e. not RFC 1918 or similar
	 * Comes from ProxyTools.php
	 *
	 * @param $ip String
	 * @return Boolean
	 */
	public static function isPublic( $ip ) {
		if ( self::isIPv6( $ip ) ) {
			return self::isPublic6( $ip );
		}
		$n = self::toUnsigned( $ip );
		if ( !$n ) {
			return false;
		}

		// ip2long accepts incomplete addresses, as well as some addresses
		// followed by garbage characters. Check that it's really valid.
		if ( $ip != long2ip( $n ) ) {
			return false;
		}

		static $privateRanges = false;
		if ( !$privateRanges ) {
			$privateRanges = array(
				array( '10.0.0.0',    '10.255.255.255' ),   # RFC 1918 (private)
				array( '172.16.0.0',  '172.31.255.255' ),   #     "
				array( '192.168.0.0', '192.168.255.255' ),  #     "
				array( '0.0.0.0',     '0.255.255.255' ),    # this network
				array( '127.0.0.0',   '127.255.255.255' ),  # loopback
			);
		}

		foreach ( $privateRanges as $r ) {
			$start = self::toUnsigned( $r[0] );
			$end = self::toUnsigned( $r[1] );
			if ( $n >= $start && $n <= $end ) {
				return false;
			}
		}
		return true;
	}

	/**
	 * Determine if an IPv6 address really is an IP address, and if it is public,
	 * i.e. not RFC 4193 or similar
	 *
	 * @param $ip String
	 * @return Boolean
	 */
	private static function isPublic6( $ip ) {
		static $privateRanges = false;
		if ( !$privateRanges ) {
			$privateRanges = array(
				array( 'fc00::', 'fdff:ffff:ffff:ffff:ffff:ffff:ffff:ffff' ), # RFC 4193 (local)
				array( '0:0:0:0:0:0:0:1', '0:0:0:0:0:0:0:1' ), # loopback
			);
		}
		$n = self::toHex( $ip );
		foreach ( $privateRanges as $r ) {
			$start = self::toHex( $r[0] );
			$end = self::toHex( $r[1] );
			if ( $n >= $start && $n <= $end ) {
				return false;
			}
		}
		return true;
	}

	/**
	 * Return a zero-padded upper case hexadecimal representation of an IP address.
	 *
	 * Hexadecimal addresses are used because they can easily be extended to
	 * IPv6 support. To separate the ranges, the return value from this
	 * function for an IPv6 address will be prefixed with "v6-", a non-
	 * hexadecimal string which sorts after the IPv4 addresses.
	 *
	 * @param $ip String: quad dotted/octet IP address.
	 * @return String
	 */
	public static function toHex( $ip ) {
		if ( self::isIPv6( $ip ) ) {
			$n = 'v6-' . self::IPv6ToRawHex( $ip );
		} else {
			$n = self::toUnsigned( $ip );
			if ( $n !== false ) {
				$n = wfBaseConvert( $n, 10, 16, 8, false );
			}
		}
		return $n;
	}

	/**
	 * Given an IPv6 address in octet notation, returns a pure hex string.
	 *
	 * @param $ip String: octet ipv6 IP address.
	 * @return String: pure hex (uppercase)
	 */
	private static function IPv6ToRawHex( $ip ) {
		$ip = self::sanitizeIP( $ip );
		if ( !$ip ) {
			return null;
		}
		$r_ip = '';
		foreach ( explode( ':', $ip ) as $v ) {
			$r_ip .= str_pad( $v, 4, 0, STR_PAD_LEFT );
		}
		return $r_ip;
	}

	/**
	 * Given an IP address in dotted-quad/octet notation, returns an unsigned integer.
	 * Like ip2long() except that it actually works and has a consistent error return value.
	 * Comes from ProxyTools.php
	 *
	 * @param $ip String: quad dotted IP address.
	 * @return Mixed: string/int/false
	 */
	public static function toUnsigned( $ip ) {
		if ( self::isIPv6( $ip ) ) {
			$n = self::toUnsigned6( $ip );
		} else {
			$n = ip2long( $ip );
			if ( $n < 0 ) {
				$n += pow( 2, 32 );
			}
		}
		return $n;
	}

	private static function toUnsigned6( $ip ) {
		return wfBaseConvert( self::IPv6ToRawHex( $ip ), 16, 10 );
	}

	/**
	 * Convert a network specification in CIDR notation
	 * to an integer network and a number of bits
	 *
	 * @param $range String: IP with CIDR prefix
	 * @return array(int or string, int)
	 */
	public static function parseCIDR( $range ) {
		if ( self::isIPv6( $range ) ) {
			return self::parseCIDR6( $range );
		}
		$parts = explode( '/', $range, 2 );
		if ( count( $parts ) != 2 ) {
			return array( false, false );
		}
		list( $network, $bits ) = $parts;
		$network = ip2long( $network );
		if ( $network !== false && is_numeric( $bits ) && $bits >= 0 && $bits <= 32 ) {
			if ( $bits == 0 ) {
				$network = 0;
			} else {
				$network &= ~( ( 1 << ( 32 - $bits ) ) - 1);
			}
			# Convert to unsigned
			if ( $network < 0 ) {
				$network += pow( 2, 32 );
			}
		} else {
			$network = false;
			$bits = false;
		}
		return array( $network, $bits );
	}

	/**
	 * Given a string range in a number of formats,
	 * return the start and end of the range in hexadecimal.
	 *
	 * Formats are:
	 *     1.2.3.4/24          CIDR
	 *     1.2.3.4 - 1.2.3.5   Explicit range
	 *     1.2.3.4             Single IP
	 *
	 *     2001:0db8:85a3::7344/96          			 CIDR
	 *     2001:0db8:85a3::7344 - 2001:0db8:85a3::7344   Explicit range
	 *     2001:0db8:85a3::7344             			 Single IP
	 * @param $range String: IP range
	 * @return array(string, string)
	 */
	public static function parseRange( $range ) {
		// CIDR notation
		if ( strpos( $range, '/' ) !== false ) {
			if ( self::isIPv6( $range ) ) {
				return self::parseRange6( $range );
			}
			list( $network, $bits ) = self::parseCIDR( $range );
			if ( $network === false ) {
				$start = $end = false;
			} else {
				$start = sprintf( '%08X', $network );
				$end = sprintf( '%08X', $network + pow( 2, ( 32 - $bits ) ) - 1 );
			}
		// Explicit range
		} elseif ( strpos( $range, '-' ) !== false ) {
			list( $start, $end ) = array_map( 'trim', explode( '-', $range, 2 ) );
			if ( self::isIPv6( $start ) && self::isIPv6( $end ) ) {
				return self::parseRange6( $range );
			}
			if ( self::isIPv4( $start ) && self::isIPv4( $end ) ) {
				$start = self::toUnsigned( $start );
				$end = self::toUnsigned( $end );
				if ( $start > $end ) {
					$start = $end = false;
				} else {
					$start = sprintf( '%08X', $start );
					$end = sprintf( '%08X', $end );
				}
			} else {
				$start = $end = false;
			}
		} else {
			# Single IP
			$start = $end = self::toHex( $range );
		}
		if ( $start === false || $end === false ) {
			return array( false, false );
		} else {
			return array( $start, $end );
		}
	}

	/**
	 * Convert a network specification in IPv6 CIDR notation to an
	 * integer network and a number of bits
	 *
	 * @return array(string, int)
	 */
	private static function parseCIDR6( $range ) {
		# Explode into <expanded IP,range>
		$parts = explode( '/', IP::sanitizeIP( $range ), 2 );
		if ( count( $parts ) != 2 ) {
			return array( false, false );
		}
		list( $network, $bits ) = $parts;
		$network = self::IPv6ToRawHex( $network );
		if ( $network !== false && is_numeric( $bits ) && $bits >= 0 && $bits <= 128 ) {
			if ( $bits == 0 ) {
				$network = "0";
			} else {
				# Native 32 bit functions WONT work here!!!
				# Convert to a padded binary number
				$network = wfBaseConvert( $network, 16, 2, 128 );
				# Truncate the last (128-$bits) bits and replace them with zeros
				$network = str_pad( substr( $network, 0, $bits ), 128, 0, STR_PAD_RIGHT );
				# Convert back to an integer
				$network = wfBaseConvert( $network, 2, 10 );
			}
		} else {
			$network = false;
			$bits = false;
		}
		return array( $network, (int)$bits );
	}

	/**
	 * Given a string range in a number of formats, return the
	 * start and end of the range in hexadecimal. For IPv6.
	 *
	 * Formats are:
	 *     2001:0db8:85a3::7344/96          			 CIDR
	 *     2001:0db8:85a3::7344 - 2001:0db8:85a3::7344   Explicit range
	 *     2001:0db8:85a3::7344/96             			 Single IP
	 * @return array(string, string)
	 */
	private static function parseRange6( $range ) {
		# Expand any IPv6 IP
		$range = IP::sanitizeIP( $range );
		// CIDR notation...
		if ( strpos( $range, '/' ) !== false ) {
			list( $network, $bits ) = self::parseCIDR6( $range );
			if ( $network === false ) {
				$start = $end = false;
			} else {
				$start = wfBaseConvert( $network, 10, 16, 32, false );
				# Turn network to binary (again)
				$end = wfBaseConvert( $network, 10, 2, 128 );
				# Truncate the last (128-$bits) bits and replace them with ones
				$end = str_pad( substr( $end, 0, $bits ), 128, 1, STR_PAD_RIGHT );
				# Convert to hex
				$end = wfBaseConvert( $end, 2, 16, 32, false );
				# see toHex() comment
				$start = "v6-$start";
				$end = "v6-$end";
			}
		// Explicit range notation...
		} elseif ( strpos( $range, '-' ) !== false ) {
			list( $start, $end ) = array_map( 'trim', explode( '-', $range, 2 ) );
			$start = self::toUnsigned6( $start );
			$end = self::toUnsigned6( $end );
			if ( $start > $end ) {
				$start = $end = false;
			} else {
				$start = wfBaseConvert( $start, 10, 16, 32, false );
				$end = wfBaseConvert( $end, 10, 16, 32, false );
			}
			# see toHex() comment
			$start = "v6-$start";
			$end = "v6-$end";
		} else {
			# Single IP
			$start = $end = self::toHex( $range );
		}
		if ( $start === false || $end === false ) {
			return array( false, false );
		} else {
			return array( $start, $end );
		}
	}

	/**
	 * Determine if a given IPv4/IPv6 address is in a given CIDR network
	 *
	 * @param $addr String: the address to check against the given range.
	 * @param $range String: the range to check the given address against.
	 * @return Boolean: whether or not the given address is in the given range.
	 */
	public static function isInRange( $addr, $range ) {
		$hexIP = self::toHex( $addr );
		list( $start, $end ) = self::parseRange( $range );
		return ( strcmp( $hexIP, $start ) >= 0 &&
			strcmp( $hexIP, $end ) <= 0 );
	}

	/**
	 * Convert some unusual representations of IPv4 addresses to their
	 * canonical dotted quad representation.
	 *
	 * This currently only checks a few IPV4-to-IPv6 related cases.  More
	 * unusual representations may be added later.
	 *
	 * @param $addr String: something that might be an IP address
	 * @return String: valid dotted quad IPv4 address or null
	 */
	public static function canonicalize( $addr ) {
		if ( self::isValid( $addr ) ) {
			return $addr;
		}
		// Turn mapped addresses from ::ce:ffff:1.2.3.4 to 1.2.3.4
		if ( strpos( $addr, ':' ) !== false && strpos( $addr, '.' ) !== false ) {
			$addr = substr( $addr, strrpos( $addr, ':' ) + 1 );
			if ( self::isIPv4( $addr ) ) {
				return $addr;
			}
		}
		// IPv6 loopback address
		$m = array();
		if ( preg_match( '/^0*' . RE_IPV6_GAP . '1$/', $addr, $m ) ) {
			return '127.0.0.1';
		}
		// IPv4-mapped and IPv4-compatible IPv6 addresses
		if ( preg_match( '/^' . RE_IPV6_V4_PREFIX . '(' . RE_IP_ADD . ')$/i', $addr, $m ) ) {
			return $m[1];
		}
		if ( preg_match( '/^' . RE_IPV6_V4_PREFIX . RE_IPV6_WORD .
			':' . RE_IPV6_WORD . '$/i', $addr, $m ) )
		{
			return long2ip( ( hexdec( $m[1] ) << 16 ) + hexdec( $m[2] ) );
		}

		return null;  // give up
	}
}