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Net::Subnet(3)	      User Contributed Perl Documentation	Net::Subnet(3)

       Net::Subnet - Fast IP-in-subnet matcher for IPv4	and IPv6, CIDR or

	   use Net::Subnet;

	   # CIDR notation
	   my $is_rfc1918 = subnet_matcher qw(

	   # Subnet mask notation
	   my $is_rfc1918 = subnet_matcher qw(

	   print $is_rfc1918->('') ?	'yes' :	'no';  # prints	"yes"
	   print $is_rfc1918->('')     ?	'yes' :	'no';  # prints	"no"

	   # Mixed IPv4	and IPv6
	   my $in_office_network = subnet_matcher qw(

	   $x =	$in_office_network->('');		# $x is	true
	   $x =	$in_office_network->('2001:db8:dead:beef::5');	# $x is	false

	   my $classifier = subnet_classifier qw(

	   $x =	$classifier->('');	       # $x is ''
	   $x =	$classifier->('2001:db8:1337::babe');  # $x is '2001:db8:1337::/48'
	   $x =	$classifier->('');	       # $x is ''
	   $x =	$classifier->('');	       # $x is undef

	   # More specific subnets (smaller subnets) must be listed first
	   my @subnets = sort_subnets(
	       '',  # second
	       '',  # first
	       '',  # third
	   my $classifier = subnet_classifier @subnets;

       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.

       Returns a reference to a	function that returns true if the given	IP
       address is in @subnets, false it	it's not.

       Returns a reference to a	function that returns the element from
       @subnets	that matches the given IP address, or undef if none matched.

       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.

   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 $hostname =~ /\.$/ ? $hostname : "$";
	       '2001:db8:1337:babe::/64' => sub	{
		   my $hostname	= get_machine_name(shift);
		   return $hostname =~ /\.$/ ? $hostname : "$";
	       '::/0' => sub {
		   (my $ip = shift) =~ s/:/x/g;
		   return "$";
	   my $classifier = subnet_classifier sort_subnets keys	%ptr;

	   while (my $ip = readline) {
	       # We get	IP adresses from STDIN and return the hostnames	on STDOUT

	       print $ptr{ $classifier->($ip) }->($ip),	"\n";

   Matching ::ffff:
       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(;
	   $ip =~ s/^::ffff://;
	   my $boolean = $matcher->($ip);

       Alternatively, translate	the subnet definition to IPv6 notation:
       "" becomes "::ffff:". 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 ""
       as well.

	   my $matcher = subnet_matcher	qw(::ffff:;
	   my $boolean = $matcher->($ip);

       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.

       Juerd Waalboer <>

       This library is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.

perl v5.32.1			  2013-06-03			Net::Subnet(3)


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