PHP5 calculate IPv6 range from cidr prefix?

对着背影说爱祢 提交于 2019-11-28 01:59:20

First of all: IPv6 doesn't have network and broadcast addresses. You can use all addresses in a prefix. Second: On a LAN the prefix length is always (well, 99.x% of the time) a /64. Routing a /68 would break IPv6 features like stateless auto configuration.

Below is a verbose implementation of an IPv6 prefix calculator:

<?php

/*
 * This is definitely not the fastest way to do it!
 */

// An example prefix
$prefix = '2001:db8:abc:1400::/54';

// Split in address and prefix length
list($firstaddrstr, $prefixlen) = explode('/', $prefix);

// Parse the address into a binary string
$firstaddrbin = inet_pton($firstaddrstr);

// Convert the binary string to a string with hexadecimal characters
# unpack() can be replaced with bin2hex()
# unpack() is used for symmetry with pack() below
$firstaddrhex = reset(unpack('H*', $firstaddrbin));

// Overwriting first address string to make sure notation is optimal
$firstaddrstr = inet_ntop($firstaddrbin);

// Calculate the number of 'flexible' bits
$flexbits = 128 - $prefixlen;

// Build the hexadecimal string of the last address
$lastaddrhex = $firstaddrhex;

// We start at the end of the string (which is always 32 characters long)
$pos = 31;
while ($flexbits > 0) {
  // Get the character at this position
  $orig = substr($lastaddrhex, $pos, 1);

  // Convert it to an integer
  $origval = hexdec($orig);

  // OR it with (2^flexbits)-1, with flexbits limited to 4 at a time
  $newval = $origval | (pow(2, min(4, $flexbits)) - 1);

  // Convert it back to a hexadecimal character
  $new = dechex($newval);

  // And put that character back in the string
  $lastaddrhex = substr_replace($lastaddrhex, $new, $pos, 1);

  // We processed one nibble, move to previous position
  $flexbits -= 4;
  $pos -= 1;
}

// Convert the hexadecimal string to a binary string
# Using pack() here
# Newer PHP version can use hex2bin()
$lastaddrbin = pack('H*', $lastaddrhex);

// And create an IPv6 address from the binary string
$lastaddrstr = inet_ntop($lastaddrbin);

// Report to user
echo "Prefix: $prefix\n";
echo "First: $firstaddrstr\n";
echo "Last: $lastaddrstr\n";

?>

It should output:

Prefix: 2001:db8:abc:1400::/54
First: 2001:db8:abc:1400::
Last: 2001:db8:abc:17ff:ffff:ffff:ffff:ffff

For those who stumble upon this question, you can do this more effectively using the dtr_pton and dtr_ntop functions and dTRIP class found on GitHub.

We also have noticed a lack of focus and tools with IPv6 in PHP, and put together this article, http://www.highonphp.com/5-tips-for-working-with-ipv6-in-php, which may be of help to others.

Function Source

This converts and IP to a binary representation:

/**
 * dtr_pton
 *
 * Converts a printable IP into an unpacked binary string
 *
 * @author Mike Mackintosh - mike@bakeryphp.com
 * @param string $ip
 * @return string $bin
 */
function dtr_pton( $ip ){

    if(filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)){
        return current( unpack( "A4", inet_pton( $ip ) ) );
    }
    elseif(filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)){
        return current( unpack( "A16", inet_pton( $ip ) ) );
    }

    throw new \Exception("Please supply a valid IPv4 or IPv6 address");

    return false;
}

This converts a binary representation to printable IP:

/**
 * dtr_ntop
 *
 * Converts an unpacked binary string into a printable IP
 *
 * @author Mike Mackintosh - mike@bakeryphp.com
 * @param string $str
 * @return string $ip
 */
function dtr_ntop( $str ){
    if( strlen( $str ) == 16 OR strlen( $str ) == 4 ){
        return inet_ntop( pack( "A".strlen( $str ) , $str ) );
    }

    throw new \Exception( "Please provide a 4 or 16 byte string" );

    return false;
}

Examples

Using the dtr_pton function you can:

$ip = dtr_pton("fe80:1:2:3:a:bad:1dea:dad");
$mask = dtr_pton("ffff:ffff:ffff:ffff:ffff:fff0::");

Get your Network and Broadcast:

var_dump( dtr_ntop( $ip & $mask ) );
var_dump( dtr_ntop( $ip | ~ $mask ) );

And your output would be:

string(18) "fe80:1:2:3:a:ba0::"
string(26) "fe80:1:2:3:a:baf:ffff:ffff"

Well, for posterity, I'm adding my code here. And also as a thanks to you guys who helped me nail this down as I needed it for an ipv6/ip2country script.

It's slightly inspired by code posted here by @mikemacintosh and @Sander Steffann, slightly improved (whishful thinking) and returns a nice object packing all the data you do/don't need:

/**
* This:
* <code>
* Ipv6_Prefix2Range('2001:43f8:10::/48');
* </code>
* returns this:
* <code>
* object(stdClass)#2 (4) {
*   ["Prefix"]=>
*   string(17) "2001:43f8:10::/48"
*   ["FirstHex"]=>
*   string(32) "200143f8001000000000000000000000"
*   ["LastHex"]=>
*   string(32) "200143f80010ffffffffffffffffffff"
*   ["MaskHex"]=>
*   string(32) "ffffffffffff00000000000000000000"
*   // Optional bin equivalents available
* }
* </code>
* 
* Tested against:
* @link https://www.ultratools.com/tools/ipv6CIDRToRange
* 
* @param string $a_Prefix
* @param bool $a_WantBins
* @return object
*/
function Ipv6_Prefix2Range($a_Prefix, $a_WantBins = false){
    // Validate input superficially with a RegExp and split accordingly
    if(!preg_match('~^([0-9a-f:]+)[[:punct:]]([0-9]+)$~i', trim($a_Prefix), $v_Slices)){
        return false;
    }
    // Make sure we have a valid ipv6 address
    if(!filter_var($v_FirstAddress = $v_Slices[1], FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)){
        return false;
    }
    // The /## end of the range
    $v_PrefixLength = intval($v_Slices[2]);
    if($v_PrefixLength > 128){
        return false; // kind'a stupid :)
    }
    $v_SuffixLength = 128 - $v_PrefixLength;

    // Convert the binary string to a hexadecimal string
    $v_FirstAddressBin = inet_pton($v_FirstAddress);
    $v_FirstAddressHex = bin2hex($v_FirstAddressBin);

    // Build the hexadecimal string of the network mask
    // (if the manually formed binary is too large, base_convert() chokes on it... so we split it up)
    $v_NetworkMaskHex = str_repeat('1', $v_PrefixLength) . str_repeat('0', $v_SuffixLength);
    $v_NetworkMaskHex_parts = str_split($v_NetworkMaskHex, 8);
    foreach($v_NetworkMaskHex_parts as &$v_NetworkMaskHex_part){
        $v_NetworkMaskHex_part = base_convert($v_NetworkMaskHex_part, 2, 16);
        $v_NetworkMaskHex_part = str_pad($v_NetworkMaskHex_part, 2, '0', STR_PAD_LEFT);
    }
    $v_NetworkMaskHex = implode(null, $v_NetworkMaskHex_parts);
    unset($v_NetworkMaskHex_part, $v_NetworkMaskHex_parts);
    $v_NetworkMaskBin = inet_pton(implode(':', str_split($v_NetworkMaskHex, 4)));

    // We have the network mask so we also apply it to First Address
    $v_FirstAddressBin &= $v_NetworkMaskBin;
    $v_FirstAddressHex = bin2hex($v_FirstAddressBin);

    // Convert the last address in hexadecimal
    $v_LastAddressBin = $v_FirstAddressBin | ~$v_NetworkMaskBin;
    $v_LastAddressHex =  bin2hex($v_LastAddressBin);

    // Return a neat object with information
    $v_Return = array(
        'Prefix'    => "{$v_FirstAddress}/{$v_PrefixLength}",
        'FirstHex'  => $v_FirstAddressHex,
        'LastHex'   => $v_LastAddressHex,
        'MaskHex'   => $v_NetworkMaskHex,
    );
    // Bins are optional...
    if($a_WantBins){
        $v_Return = array_merge($v_Return, array(
            'FirstBin'  => $v_FirstAddressBin,
            'LastBin'   => $v_LastAddressBin,
            'MaskBin'   => $v_NetworkMaskBin,
        ));
    }
    return (object)$v_Return;
}

I like functions and classes and dislike non-reusable code where reusable functionality is implemented.

PS: If you find issues with it, please get back to me. I'm far from an expert in IPv6.

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