Greetings,
I'd like to check to see if an ip is within an ip cidr style network
block (192.75.242.157 with 192.75.242.0/23). Initially, I started off
with some code derived from some perl code that I found (code below).
However, the bitmask calcution did not work ( $bitmask = 0xffffffff <<
(32 - $nbits);) and the hexdec did not appear to support values as bit
as 0xffffffff.
So I did a bit more research and found a relevant posting on the php
mailing list. If the function 'within' works properly it should return
true if the ip is within the network block but I cannot seem to get it
to work properly. Are there any CIDR/bitwise operator wiz's out there
that could help me get this straightened out. Thanks.
/Paul
Input:
remote_ip = 192.75.242.88
cidr = 192.75.242.0/24
Output:
ip = -1068764584
start = -1068764672
mask = -16777216
function within ($remote_ip, $cidr) {
## within function checks whether an ip is within a network
block
## example with("192.75.242.157", "192.75.242.0/24")
## returns true if ip is within range
$ip=ip2long($remote_ip);
list ($quad, $nbits) = split ("/", $cidr, 2);
$shift_mask = (integer) $nbits;
$start=ip2long($quad);
$mask = -1<<$shift_mask;
return $ip & $start == $mask;
}
PERL derived code:
$cidr = $valid_client; /* db value 192.55.192.0/24 */
list ($quad, $nbits) = split ("/", $cidr, 2);
$byte = explode (".", $quad);
$address_required = ($byte[0] << 24) | ($byte[1] << 16) | ($byte[2] <<
8) | $byte[3];
/* remote host info */
$byte = explode(".", $ip); /* ip from $HTTP_SERVER_VARS['REMOTE_ADDR']
*/
$address_client = ($byte[0] << 24) | ($byte[1] << 16) | ($byte[2] << 8)
| $byte[3];
$bitmask = 0xffffffff << (32 - $nbits);
if (($address_client & $bitmask) == ($address_required & $bitmask)) {
echo "Ip is within block";
} else {
echo "Ip is NOT within block";
}
--
________________________________________________________________
Paul Wolstenholme
SMA Webware
http://www.zzube.com/
What do you know?
http://make.zzube.com/
Vancouver, BC Canada
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