Created
April 13, 2020 20:18
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PERL script that takes a list of CIDRs and reduces them to a minimal set
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#!/usr/bin/perl -w | |
use strict; | |
use Data::Dumper; | |
my @ips; | |
sub ipCmp($$) { | |
my $ip1 = shift; | |
my $ip2 = shift; | |
my $r = ($ip1->[0] <=> $ip2->[0]); | |
return $r ? $r : ($ip2->[1] <=> $ip1->[1]); | |
} | |
sub ipStr($) { | |
my $i = shift; | |
my @ip; | |
foreach (0..3) { | |
unshift @ip, $i & 0xff; | |
$i >>= 8; | |
} | |
return join('.', @ip); | |
} | |
sub reduce($$) { | |
my $start = shift; | |
my $end = shift; | |
my @ret; | |
while ($start <= $end) { | |
my $nmb = 1; | |
while (1) { | |
my $nm = (2 ** $nmb) - 1; | |
last if (($start & ~$nm) != $start) || (($start | $nm) > $end); | |
++$nmb; | |
} | |
--$nmb; | |
push @ret, ipStr($start) . '/' . (32 - $nmb); | |
$start += 2 ** $nmb; | |
} | |
return @ret; | |
} | |
print STDERR "Reading...\n"; | |
while (<>) { | |
my ($ip, $nm) = /(?:\s|^)((?:\d+\.){0,3}(?:\d+))(?:\/(\d+))(?:\s|$)/; | |
next unless $ip; | |
$nm = 32 unless $nm; | |
my @ipa = split(/\./, $ip); | |
unshift @ipa, 0, 0, 0 if @ipa == 1; | |
splice @ipa, 1, 0, 0 while @ipa < 4; | |
my $start = 0; | |
foreach (@ipa) { | |
$start = ($start << 8) | ($_ & 0xff); | |
} | |
my $nmb = ((2 ** $nm) - 1) << (32 - $nm); | |
$start &= $nmb; | |
my $end = $start | (~$nmb & 0xffffffff); | |
push @ips, [ $start, $end, "$ip/$nm" ]; | |
} | |
print STDERR "Sorting...\n"; | |
@ips = sort { ipCmp($a, $b) } @ips; | |
print STDERR "Reducing...\n"; | |
my $start = $ips[0]->[0]; | |
my $end = $ips[0]->[1]; | |
foreach my $ip (@ips) { | |
if ($ip->[0] <= $end + 1) { | |
$end = $ip->[1] if $ip->[1] > $end; | |
next; | |
} | |
my @r = reduce($start, $end); | |
print join("\n", @r), "\n"; | |
$start = $ip->[0]; | |
$end = $ip->[1]; | |
} | |
my @r = reduce($start, $end); | |
print join("\n", @r), "\n"; | |
exit 0; |
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