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+<?php
+/**
+ * Copyright 2014, 2015 Brandon Black <blblack@gmail.com>
+ *
+ * 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 Brandon Black <blblack@gmail.com>
+ */
+namespace IPSet;
+
+/**
+ * Matches IP addresses against a set of CIDR specifications
+ *
+ * Usage:
+ *
+ * // At startup, calculate the optimized data structure for the set:
+ * $ipset = new IPSet( array(
+ * '208.80.154.0/26',
+ * '2620:0:861:1::/64',
+ * '10.64.0.0/22',
+ * ) );
+ *
+ * // Runtime check against cached set (returns bool):
+ * $allowme = $ipset->match( $ip );
+ *
+ * In rough benchmarking, this takes about 80% more time than
+ * in_array() checks on a short (a couple hundred at most) array
+ * of addresses. It's fast either way at those levels, though,
+ * and IPSet would scale better than in_array if the array were
+ * much larger.
+ *
+ * For mixed-family CIDR sets, however, this code gives well over
+ * 100x speedup vs iterating IP::isInRange() over an array
+ * of CIDR specs.
+ *
+ * The basic implementation is two separate binary trees
+ * (IPv4 and IPv6) as nested php arrays with keys named 0 and 1.
+ * The values false and true are terminal match-fail and match-success,
+ * otherwise the value is a deeper node in the tree.
+ *
+ * A simple depth-compression scheme is also implemented: whole-byte
+ * tree compression at whole-byte boundaries only, where no branching
+ * occurs during that whole byte of depth. A compressed node has
+ * keys 'comp' (the byte to compare) and 'next' (the next node to
+ * recurse into if 'comp' matched successfully).
+ *
+ * For example, given these inputs:
+ *
+ * 25.0.0.0/9
+ * 25.192.0.0/10
+ *
+ * The v4 tree would look like:
+ *
+ * root4 => array(
+ * 'comp' => 25,
+ * 'next' => array(
+ * 0 => true,
+ * 1 => array(
+ * 0 => false,
+ * 1 => true,
+ * ),
+ * ),
+ * );
+ *
+ * (multi-byte compression nodes were attempted as well, but were
+ * a net loss in my test scenarios due to additional match complexity)
+ */
+class IPSet {
+ /** @var array $root4 The root of the IPv4 matching tree */
+ private $root4 = array( false, false );
+
+ /** @var array $root6 The root of the IPv6 matching tree */
+ private $root6 = array( false, false );
+
+ /**
+ * Instantiate the object from an array of CIDR specs
+ *
+ * Invalid input network/mask values in $cfg will result in issuing
+ * E_WARNING and/or E_USER_WARNING and the bad values being ignored.
+ *
+ * @param array $cfg Array of IPv[46] CIDR specs as strings
+ */
+ public function __construct( array $cfg ) {
+ foreach ( $cfg as $cidr ) {
+ $this->addCidr( $cidr );
+ }
+
+ self::recOptimize( $this->root4 );
+ self::recCompress( $this->root4, 0, 24 );
+ self::recOptimize( $this->root6 );
+ self::recCompress( $this->root6, 0, 120 );
+ }
+
+ /**
+ * Add a single CIDR spec to the internal matching trees
+ *
+ * @param string $cidr String CIDR spec, IPv[46], optional /mask (def all-1's)
+ */
+ private function addCidr( $cidr ) {
+ // v4 or v6 check
+ if ( strpos( $cidr, ':' ) === false ) {
+ $node =& $this->root4;
+ $defMask = '32';
+ } else {
+ $node =& $this->root6;
+ $defMask = '128';
+ }
+
+ // Default to all-1's mask if no netmask in the input
+ if ( strpos( $cidr, '/' ) === false ) {
+ $net = $cidr;
+ $mask = $defMask;
+ } else {
+ list( $net, $mask ) = explode( '/', $cidr, 2 );
+ if ( !ctype_digit( $mask ) || intval( $mask ) > $defMask ) {
+ trigger_error( "IPSet: Bad mask '$mask' from '$cidr', ignored", E_USER_WARNING );
+ return;
+ }
+ }
+ $mask = intval( $mask ); // explicit integer convert, checked above
+
+ // convert $net to an array of integer bytes, length 4 or 16:
+ $raw = inet_pton( $net );
+ if ( $raw === false ) {
+ return; // inet_pton() sends an E_WARNING for us
+ }
+ $rawOrd = array_map( 'ord', str_split( $raw ) );
+
+ // special-case: zero mask overwrites the whole tree with a pair of terminal successes
+ if ( $mask == 0 ) {
+ $node = array( true, true );
+ return;
+ }
+
+ // iterate the bits of the address while walking the tree structure for inserts
+ $curBit = 0;
+ while ( 1 ) {
+ $maskShift = 7 - ( $curBit & 7 );
+ $node =& $node[( $rawOrd[$curBit >> 3] & ( 1 << $maskShift ) ) >> $maskShift];
+ ++$curBit;
+ if ( $node === true ) {
+ // already added a larger supernet, no need to go deeper
+ return;
+ } elseif ( $curBit == $mask ) {
+ // this may wipe out deeper subnets from earlier
+ $node = true;
+ return;
+ } elseif ( $node === false ) {
+ // create new subarray to go deeper
+ $node = array( false, false );
+ }
+ }
+ }
+
+ /**
+ * Match an IP address against the set
+ *
+ * If $ip is unparseable, inet_pton may issue an E_WARNING to that effect
+ *
+ * @param string $ip string IPv[46] address
+ * @return bool True is match success, false is match failure
+ */
+ public function match( $ip ) {
+ $raw = inet_pton( $ip );
+ if ( $raw === false ) {
+ return false; // inet_pton() sends an E_WARNING for us
+ }
+
+ $rawOrd = array_map( 'ord', str_split( $raw ) );
+ if ( count( $rawOrd ) == 4 ) {
+ $node =& $this->root4;
+ } else {
+ $node =& $this->root6;
+ }
+
+ $curBit = 0;
+ while ( 1 ) {
+ if ( isset( $node['comp'] ) ) {
+ // compressed node, matches 1 whole byte on a byte boundary
+ if ( $rawOrd[$curBit >> 3] != $node['comp'] ) {
+ return false;
+ }
+ $curBit += 8;
+ $node =& $node['next'];
+ } else {
+ // uncompressed node, walk in the correct direction for the current bit-value
+ $maskShift = 7 - ( $curBit & 7 );
+ $node =& $node[( $rawOrd[$curBit >> 3] & ( 1 << $maskShift ) ) >> $maskShift];
+ ++$curBit;
+ }
+
+ if ( $node === true || $node === false ) {
+ return $node;
+ }
+ }
+ }
+
+ /**
+ * Recursively merges adjacent nets into larger supernets
+ *
+ * @param array &$node Tree node to optimize, by-reference
+ *
+ * e.g.: 8.0.0.0/8 + 9.0.0.0/8 -> 8.0.0.0/7
+ */
+ private static function recOptimize( &$node ) {
+ if ( $node[0] !== false && $node[0] !== true && self::recOptimize( $node[0] ) ) {
+ $node[0] = true;
+ }
+ if ( $node[1] !== false && $node[1] !== true && self::recOptimize( $node[1] ) ) {
+ $node[1] = true;
+ }
+ if ( $node[0] === true && $node[1] === true ) {
+ return true;
+ }
+ return false;
+ }
+
+ /**
+ * Recursively compresses a tree
+ *
+ * @param array &$node Tree node to compress, by-reference
+ * @param integer $curBit current depth in the tree
+ * @param integer $maxCompStart maximum depth at which compression can start, family-specific
+ *
+ * This is a very simplistic compression scheme: if we go through a whole
+ * byte of address starting at a byte boundary with no real branching
+ * other than immediate false-vs-(node|true), compress that subtree down to a single
+ * byte-matching node.
+ * The $maxCompStart check elides recursing the final 7 levels of depth (family-dependent)
+ */
+ private static function recCompress( &$node, $curBit, $maxCompStart ) {
+ if ( !( $curBit & 7 ) ) { // byte boundary, check for depth-8 single path(s)
+ $byte = 0;
+ $cnode =& $node;
+ $i = 8;
+ while ( $i-- ) {
+ if ( $cnode[0] === false ) {
+ $byte |= 1 << $i;
+ $cnode =& $cnode[1];
+ } elseif ( $cnode[1] === false ) {
+ $cnode =& $cnode[0];
+ } else {
+ // partial-byte branching, give up
+ break;
+ }
+ }
+ if ( $i == -1 ) { // means we did not exit the while() via break
+ $node = array(
+ 'comp' => $byte,
+ 'next' => &$cnode,
+ );
+ $curBit += 8;
+ if ( $cnode !== true ) {
+ self::recCompress( $cnode, $curBit, $maxCompStart );
+ }
+ return;
+ }
+ }
+
+ ++$curBit;
+ if ( $curBit <= $maxCompStart ) {
+ if ( $node[0] !== false && $node[0] !== true ) {
+ self::recCompress( $node[0], $curBit, $maxCompStart );
+ }
+ if ( $node[1] !== false && $node[1] !== true ) {
+ self::recCompress( $node[1], $curBit, $maxCompStart );
+ }
+ }
+ }
+}
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