Short little function, Takes 2 IP and compares them - returning true or false. Also takes a CIDR netblock and an IP and returns true if the IP is within the netblock.
# Quick example
print (ip_comp("192.168.3.0/16","192.168.2.5")?"MATCH":"NO-MATCH");

sub ip_comp
{
my ($n, $i) = @_;
 # $n - the "network ip"
 #    x.x.x.x or x.x.x.x/c
 #    where x is 0-255 and c is the CIDR netblock
 # $i is the ip we want to check
return ($i eq $n) unless $n =~ /^(.*)\/(.*)$/;
return (((unpack('N',pack('C4',split(/\./,$i))) ^ unpack('N',pack('C4'
+,split(/\./,$1)))) & (0xFFFFFFFF << (32 - $2))) == 0);
}

[download]

Replies are listed 'Best First'.
Re: Check IP with support for CIDR
by ehdonhon (Curate) on Apr 11, 2002 at 12:21 UTC
[reply]
(MeowChow) Re: Check IP with support for CIDR
by MeowChow (Vicar) on Apr 12, 2002 at 01:24 UTC
    You can simplify the CIDR mask check: 
    return unpack ('N', pack ('C4', split /\./, $i) ^ pack ('C4', split /\
+./, $1)) >> 32 - $2;

    [download]
       MeowChow                                   
               s aamecha.s a..a\u$&owag.print
[reply]
[d/l]
      Could not get that to work. However, it did make me think and hence this: 
      return ( (unpack('N',pack('C4',split(/\./,$i))) ^ unpack('N',pack('C4'
+,split(/\./,$1)))) >> (32-$2) ) == 0;

      [download]
      --
      TTFN, FNORD
[reply]
[d/l]
        My bad, I forgot to negate the result: 
        return not unpack ('N', pack ('C4', split /\./, $i) ^ pack ('C4', spli
+t /\./, $1)) >> 32 - $2;

        [download]
           MeowChow                                   
               s aamecha.s a..a\u$&owag.print
[reply]
[d/l]

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