NAME¶
Net::Subnet - Fast IP-in-subnet matcher for IPv4 and IPv6, CIDR or mask.
SYNOPSIS¶
use Net::Subnet;
# CIDR notation
my $is_rfc1918 = subnet_matcher qw(
10.0.0.0/8
172.16.0.0/12
192.168.0.0/16
);
# Subnet mask notation
my $is_rfc1918 = subnet_matcher qw(
10.0.0.0/255.0.0.0
172.16.0.0/255.240.0.0
192.168.0.0/255.255.0.0
);
print $is_rfc1918->('192.168.1.1') ? 'yes' : 'no'; # prints "yes"
print $is_rfc1918->('8.8.8.8') ? 'yes' : 'no'; # prints "no"
# Mixed IPv4 and IPv6
my $in_office_network = subnet_matcher qw(
192.168.1.0/24
2001:db8:1337::/48
);
$x = $in_office_network->('192.168.1.1'); # $x is true
$x = $in_office_network->('2001:db8:dead:beef::5'); # $x is false
my $classifier = subnet_classifier qw(
192.168.1.0/24
2001:db8:1337::/48
10.0.0.0/255.0.0.0
);
$x = $classifier->('192.168.1.250'); # $x is '192.168.1.0/24'
$x = $classifier->('2001:db8:1337::babe'); # $x is '2001:db8:1337::/48'
$x = $classifier->('10.2.127.1'); # $x is '10.0.0.0/255.0.0.0'
$x = $classifier->('8.8.8.8'); # $x is undef
# More specific subnets (smaller subnets) must be listed first
my @subnets = sort_subnets(
'192.168.0.0/24', # second
'192.168.0.1/32', # first
'192.168.0.0/16', # third
);
my $classifier = subnet_classifier @subnets;
DESCRIPTION¶
This is a simple but fast pure Perl module for determining whether a given IP
address is in a given set of IP subnets. It's iterative, and it doesn't use
any fancy tries, but because it uses simple bitwise operations on strings it's
still very fast.
All documented functions are exported by default.
Subnets have to be given in "address/mask" or
"address/length" (CIDR) format. The Socket and Socket6 modules are
used to normalise addresses, which means that any of the address formats
supported by inet_aton and inet_pton can be used with Net::Subnet.
FUNCTIONS¶
subnet_matcher(@subnets)¶
Returns a reference to a function that returns true if the given IP address is
in @subnets, false it it's not.
subnet_classifier(@subnets)¶
Returns a reference to a function that returns the element from @subnets that
matches the given IP address, or undef if none matched.
sort_subnets(@subnets)¶
Returns @subnets in reverse order of prefix length and prefix; use this with
subnet_matcher or subnet_classifier if your subnet list has overlapping ranges
and it's not already sorted most-specific-first.
TRICKS¶
Generating PTR records for IPv6¶
If you need to classify an IP address, but want some other value than the
original subnet string, just use a hash. You could even use code references;
here's an example of how to generate dynamic reverse DNS records for IPv6
addresses:
my %ptr = (
'2001:db8:1337:d00d::/64' => sub {
my $hostname = get_machine_name(shift);
return $hostname =~ /\.$/ ? $hostname : "$hostname.example.org.";
},
'2001:db8:1337:babe::/64' => sub {
my $hostname = get_machine_name(shift);
return $hostname =~ /\.$/ ? $hostname : "$hostname.example.net.";
},
'::/0' => sub {
(my $ip = shift) =~ s/:/x/g;
return "$ip.unknown.example.com.";
},
);
my $classifier = subnet_classifier sort_subnets keys %ptr;
while (my $ip = readline) {
# We get IP addresses from STDIN and return the hostnames on STDOUT
print $ptr{ $classifier->($ip) }->($ip), "\n";
}
Matching ::ffff:192.168.1.200¶
IPv4 subnets only match IPv4 addresses. If you need to match IPv4-mapped IPv6
addresses, i.e. IPv4 addresses with "::ffff:" stuck in front of
them, simply remove that part before matching:
my $matcher = subnet_matcher qw(192.168.1.0/22);
$ip =~ s/^::ffff://;
my $boolean = $matcher->($ip);
Alternatively, translate the subnet definition to IPv6 notation:
"1.2.3.0/24" becomes "::ffff:1.2.3.0/120". If you do this,
hexadecimal addresses such as "::ffff:102:304" will also match, but
IPv4 addresses without "::ffff:" will no longer match unless you
include "1.2.3.0/24" as well.
my $matcher = subnet_matcher qw(::ffff:192.168.1.0/118 192.168.1.0/22);
my $boolean = $matcher->($ip);
CAVEATS¶
No argument verification is done; garbage in, garbage out. If you give it
hostnames, DNS may be used to resolve them, courtesy of the Socket and Socket6
modules.
AUTHOR¶
Juerd Waalboer <juerd#@tnx.nl>
LICENSE¶
This library is free software; you can redistribute it and/or modify it under
the same terms as Perl itself.