php: ip2long returning negative val

Question

function ip_address_to_number($IPaddress) { 
     if(!$IPaddress) {
      return false;
     } else {
      $ips = split('\.',$IPaddress);
      return($ips[3] + $ips[2]*256 + $ips[1]*65536 + $ips[0]*16777216);
     }
}

that function executes the same code as the php bundled function ip2long. however, when i print these 2 values, i get 2 different returns. why? (im using php 5.2.10 on a wamp environment).

ip2long('200.117.248.17'); //returns **-931792879**

ip_address_to_number('200.117.248.17'); // returns **3363174417**

Applied and continued here: Showing my country based on my IP, mysql optimized

Answer 1

Did some performance tests to compare running ip2long through sprintf vs array explode and then times or bitwise shift:

<?php
    header ('Content-Type: text/plain');

    function ip_range($start, $count) {
        $start = ip2long($start);
        return array_map('long2ip', range($start, $start + $count) );
    }

    $iterations = 500000;
    $results = array();
    $ips = ip_range('192.168.1.1', $iterations);
    $time = microtime(true);
    foreach ($ips as $ip) {
        $result = sprintf('%u', ip2long($ip));
    }
    $time = microtime(true) - $time;
    $results['ip2long'] = array ('total' => $time, 'cycles' => $iterations, 'average' => ($time / $iterations) . 's', 'speed' => ($iterations/$time) . ' hashes per second.' );

    $time = microtime(true);
    foreach ($ips as $ip) {
        $aIp = explode('.', $ip);
        if (count($aIp) == 4) {
            $result = /*sprintf('%u',*/ $aIp[0]*16777216 + $aIp[1]*65536 + $aIp[2]*256 + $aIp[3] /*)*/;
        }
        else
        {
            $result = false;
        }
    }
    $time = microtime(true) - $time;
    $results['explode multiple'] = array ('total' => $time, 'cycles' => $iterations, 'average' => ($time / $iterations) . 's', 'speed' => ($iterations/$time) . ' hashes per second.' );

    $time = microtime(true);
    foreach ($ips as $ip) {
        $aIp = explode('.', $ip);
        if (count($aIp) == 4) {
            $result = /*sprintf('%u',*/ $aIp[3] | $aIp[2] << 8 | $aIp[1] << 16 | $aIp[0] << 24 /*)*/;
        }
        else
        {
            $result = false;
        }
    }
    $time = microtime(true) - $time;
    $results['explode bitwise'] = array ('total' => $time, 'cycles' => $iterations, 'average' => ($time / $iterations) . 's', 'speed' => ($iterations/$time) . ' hashes per second.' );


    die(var_dump($results));

These are the results:

array(3) {


["ip2long"]=>
  array(4) {
    ["total"]=>
    float(0.92530012130737)
    ["cycles"]=>
    int(500000)
    ["average"]=>
    string(19) "1.8506002426147E-6s"
    ["speed"]=>
    string(34) "540365.21609177 hashes per second."
  }
  ["explode multiple"]=>
  array(4) {
    ["total"]=>
    float(0.91870212554932)
    ["cycles"]=>
    int(500000)
    ["average"]=>
    string(19) "1.8374042510986E-6s"
    ["speed"]=>
    string(34) "544246.04678153 hashes per second."
  }
  ["explode bitwise"]=>
  array(4) {
    ["total"]=>
    float(0.9184091091156)
    ["cycles"]=>
    int(500000)
    ["average"]=>
    string(19) "1.8368182182312E-6s"
    ["speed"]=>
    string(34) "544419.68730197 hashes per second."
  }
}

When wrapping the bitwise and multiply in sprintf they are slower than ip2long but since it's not needed, they are faster.

Answer 2

  $ips[3]                             = 17
+ $ips[2] * 256 = 248 * 256           = 63488
+ $ips[1] * 65536 = 117 * 65536       = 7667712
+ $ips[0] * 16777216 = 200 * 16777216 = 3355443200
                                      = 3363174417

PHP max integer value (32-bit) is 2147483647, which is < 3363174417

Quoting from the ip2long() PHP manual page

Note: Because PHP's integer type is signed, and many IP addresses will result in negative integers, you need to use the "%u" formatter of sprintf() or printf() to get the string representation of the unsigned IP address.

Answer 3

<?php
function _ip2long($input)
{
    $r = null;
    if (is_string($input))
    {
        $_input = trim($input);
        if (filter_var($_input, FILTER_VALIDATE_IP))
        {
            $PRE_r = explode('.', $_input);
            $r = ($PRE_r[0] * pow(256, 3)) + ($PRE_r[1] * pow(256, 2)) + ($PRE_r[2] * 256) + ($PRE_r[0]);
        } else
        { 
            $r = false;
        }
    } else
    {
        $r = false;
    }
    return ($r);
}
$out = _ip2long('127.0.0.1');
if (false === $out)
{
  print('Invalid IP');
} else
{
  print($out);
}
?>

Answer 4

Try this instead:

$ip = sprintf('%u', ip2long($_SERVER['REMOTE_ADDR']));

sprintf will then write it as an unsigned integer.

Answer 5

glopes@nebm:~$ php -r "printf('%u', -931792879);"
3363174417

There you go. My guess is that you are on a system with 32-bit ints and your ip_address_to_number is actually returning a float.

You see, with 32-bit ints, your maximum positive integer is (2^31) - 1 = 2 147 483 647, so the integer wraps around.

If you want to mimic the behaviour of the PHP function, do:

function ip_address_to_number($IPaddress) { 
 if(!$IPaddress) {
  return false;
 } else {
  $ips = split('\.',$IPaddress);
  return($ips[3] | $ips[2] << 8 | $ips[1] << 16 | $ips[0] << 24);
 }
}

(by the way, split has been deprecated)

Answer 6

You can use -

// IP Address to Number
function inet_aton($ip)
{
    $ip = trim($ip);
    if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)) return 0;
    return sprintf("%u", ip2long($ip));  
}

// Number to IP Address
function inet_ntoa($num)
{
    $num = trim($num);
    if ($num == "0") return "0.0.0.0";
    return long2ip(-(4294967295 - ($num - 1))); 
}