Net::Netmask(3pm) User Contributed Perl Documentation Net::Netmask(3pm)
NAME
Net::Netmask - parse, manipulate and lookup IP network blocks
SYNOPSIS
use Net::Netmask;
$block = Net::Netmask->safe_new(network block)
$block = Net::Netmask->safe_new(network block, netmask)
$block = Net::Netmask->new2(network block)
$block = Net::Netmask->new2(network block, netmask)
$block = Net::Netmask->new(network block) # Don't use in new code!
$block = Net::Netmask->new(network block, netmask) # Don't use in new code!
print $block; # a.b.c.d/bits or 1:2:3::4/bits
print $block->base()
print $block->mask()
print $block->hostmask()
print $block->bits()
print $block->size()
print $block->maxblock()
print $block->broadcast()
print $block->next()
print $block->match($ip);
print $block->nth(1, [$bitstep]);
print $block->protocol();
if ($block->sameblock("network block")) ...
if ($block->cmpblocks("network block")) ...
$newblock = $block->nextblock([count]);
for $ip ($block->enumerate([$bitstep])) { }
for $zone ($block->inaddr()) { }
my $table = {};
$block->storeNetblock([$table])
$block->deleteNetblock([$table])
@missingblocks = $block->cidrs2inverse(@blocks)
$block = findNetblock(ip, [$table])
$block = findOuterNetblock(ip, [$table])
@blocks = findAllNetblock(ip, [$table])
if ($block->checkNetblock([$table]) ...
$block2 = $block1->findOuterNetblock([$table])
@blocks = dumpNetworkTable([$table])
@blocks = range2cidrlist($beginip, $endip);
@blocks = cidrs2cidrs(@blocks_with_dups)
@listofblocks = cidrs2contiglists(@blocks);
@blocks = sort @blocks
@blocks = sort_network_blocks(@blocks)
@sorted_ip_addrs = sort_by_ip_address(@unsorted_ip_addrs)
DESCRIPTION
Net::Netmask parses and understands IPv4 and IPv6 CIDR blocks (see
<https://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing> for more
information on CIDR blocks). It's built with an object-oriented
interface, with functions being methods that operate on a Net::Netmask
object.
These methods provide nearly all types of information about a network
block that you might want.
There are also functions to insert a network block into a table and
then later lookup network blocks by IP address using that table. There
are functions to turn a IP address range into a list of CIDR blocks.
There are functions to turn a list of CIDR blocks into a list of IP
addresses.
There is a function for sorting by text IP address.
All functions understand both IPv4 and IPv6. Matches, finds, etc, will
always return false when an IPv4 address is matched against an IPv6
address.
IPv6 support was added in 1.9104.
CONSTRUCTING
Net::Netmask objects are created with an IP address and optionally a
mask. There are many forms that are recognized:
'216.240.32.0/24' The preferred IPv4 form.
'216.240.32.0:255.255.255.0'
'216.240.32.0-255.255.255.0'
'216.240.32.0', '255.255.255.0'
'216.240.32.0', '0xffffff00'
'216.240.32.0 - 216.240.32.255'
'216.240.32.4' A /32 block.
'default' or 'any' 0.0.0.0/0 (the default route)
'216.240.32.0#0.0.31.255' A hostmask (as used by Cisco access-
lists - that is, the hostmask is the
bitwise inverse of a netmask).
'2001:db8:1234:5678::/64' The preferred IPv6 form.
'2001:db8:1234:5678::9876' A /128 block.
'default6' or 'any6' ::/0 (the default route)
There are two constructor methods: "new" and "safe_new" (also known as
"new2").
"safe_new" differs from "new" in that it will return undef for invalid
netmasks, while "new" will return a netmask object even if the
constructor could not figure out what the network block should be.
With "new", the error string can be found as $block->{'ERROR'}. With
"safe_new" the error can be found as Net::Netmask::errstr or
$Net::Netmask::error.
IMPORTANT: You want to use "safe_new" or "new2" ("new2" is a synonym
for "safe_new") in new code!
As of version 2.000, the following abbreviated IPv4 netblocks are not
accepted by default, but can be accepted with options.
'216.240.32' Always a /24 block.
'216.240' Always a /16 block.
'140' Always a /8 block.
'216.240.32/24'
'216.240/16'
To accept these, you can call the constructor with a "shortnet" option
set to a true value. Example:
my $block = Net::Netmask->safe_new("216.240/16", shortnet => 1);
For compatibility with older codebases, it's also possible to change
the default to use the old behavior. To do this, you can set the
$Net::Netmask::SHORTNET_DEFAULT variable to a true value. It is
recommended that this be done by localizing the variable. Example:
local $Net::Netmask::SHORTNET_DEFAULT = 1
my $block = Net::Netmask->safe_new("216.240/16");
Please be aware that there are security implications to this as other
Perl modules, system libraries, or utilities may not parse these
addresses the same way. This is why the default was changed.
For instance:
perl -MNet::Netmask -E "say Net::Netmask->safe_new("10.20", shortnet => 1)"
Will print "10.2.0.0/16". However:
perl -MSocket -E "say inet_ntoa(inet_aton('10.20'))"
Will often print "10.0.0.20" which is obviously very different, and if
the Net::Netmask module was used to check an IP aggainst an ACL, and
then another program was executed (that uses inet_aton(), for
instance), the ACL processing might not match the connection.
Thus, it is advised to use this with caution.
METHODS
->desc() Returns a description of the network block.
Eg: "216.240.32.0/19" or "2001:db8:1234::/48".
This is also available as overloaded
stringification.
->base() Returns base address of the network block as a
string. Eg: "216.240.32.0". or
"2001:db8:1234::/48". Base does not give an
indication of the size of the network block.
->mask() Returns the netmask as a string. Eg:
"255.255.255.0" or "ffff:ffff:ffff:ffff::"
->hostmask() Returns the host mask which is the opposite of
the netmask. Eg: "0.0.0.255" or
"::ffff:ffff:ffff:ffff".
->bits() Returns the netmask as a number of bits in the
network portion of the address for this block.
Eg: 24.
->size() Returns the number of IP addresses in a block.
Eg: 256. For IPv6 addresses, this will be a
Math::BigInt object.
->broadcast() The blocks broadcast address. (The last IP
address inside the block.) Eg: 192.168.1.0/24
=> 192.168.1.255 or 2001:db8::/64 =>
2001:db8::ffff:ffff:ffff:ffff
->next() The first IP address following the block. (The
IP address following the broadcast address.)
Eg: 192.168.1.0/24 => 192.168.2.0 or
2001:db8:0:1::/64 => 2001:db8:0:2::/64
->first() & ->last() Synonyms for ->base() and ->broadcast()
->protocol() Added in version 1.9102.
Returns the address family/protocol
represented by the block. Either 'IPv4' or
'IPv6'.
->match($ip) Returns a true if the IP number $ip matches
the given network. That is, a true value is
returned if $ip is between base() and
broadcast(). For example, if we have the
network 192.168.1.0/24, then
192.168.0.255 => 0
192.168.1.0 => "0 "
192.168.1.1 => 1
...
192.168.1.255 => 255
$ip should be a dotted-quad (eg:
"192.168.66.3") or an IPv6 address in standard
notation (eg: "2001:db8::1").
It just happens that the return value is the
position within the block. Since zero is a
legal position, the true string "0 " is
returned in it's place. "0 " is numerically
zero though. When wanting to know the
position inside the block, a good idiom is:
$pos = $block->match($ip) or die;
$pos += 0;
->maxblock() Much of the time, it is not possible to
determine the size of a network block just
from it's base address. For example, with the
network block '216.240.32.0/27', if you only
had the '216.240.32.0' portion you wouldn't be
able to tell for certain the size of the
block. '216.240.32.0' could be anything from
a '/23' to a '/32'. The maxblock() method
gives the size of the largest block that the
current block's address would allow it to be.
The size is given in bits. Eg: 23.
->enumerate([$bitstep) Returns a list of all the IP addresses in the
block. Be very careful not to use this
function of large blocks. The IP addresses
are returned as strings. Eg: '216.240.32.0',
'216.240.32.1', ... '216.240.32.255'.
If the optional argument is given, step
through the block in increments of a given
network size. To step by 4, use a bitstep of
30 (as in a /30 network).
Note that for IPv6, this will return failure
if more than 1,000,000,000 addresses would be
returned.
->nth($index, [$bitstep])
Returns the nth element of the array that
enumerate would return if it were called. So,
to get the first usable address in a block,
use nth(1). To get the broadcast address, use
nth(-1). To get the last usable address, use
nth(-2).
->inaddr() Returns an inline list of tuples.
For IPv4:
There is a tuple for each DNS zone name (at
the /24 level) in the block. If the block is
smaller than a /24, then the zone of the
enclosing /24 is returned.
Each tuple contains: the DNS zone name, the
last component of the first IP address in the
block in that zone, the last component of the
last IP address in the block in that zone.
Examples: the list returned for the block
'216.240.32.0/23' would be:
'32.240.216.in-addr.arpa', 0, 255,
'33.240.216.in-addr.arpa', 0, 255. The list
returned for the block '216.240.32.64/27'
would be: '32.240.216.in-addr.arpa', 64, 95.
For IPv6:
A list is returned with each DNS zone name at
the shortest-prefix length possible. This is
not returned as a tuple, but just a list of
strings.
Examples: the list returned for the block
'2002::/16' would be a one element list,
containing just 2.0.0.2.ip6.arpa'. The list
for '2002::/17' would return a two element
list containing '0.2.0.0.2.ip6.arpa' and
'1.2.0.0.2.ip6.arpa'.
->nextblock([$count]) Without a $count, return the next block of the
same size after the current one. With a
count, return the Nth block after the current
one. A count of -1 returns the previous
block. Undef will be returned if out of legal
address space.
->sameblock($block) Compares two blocks. The second block will be
auto-converted from a string if it isn't
already a Net::Netmask object. Returns 1 if
they are identical.
->cmpblocks($block) Compares two blocks. The second block will be
auto-converted from a string if it isn't
already a Net::Netmask object. Returns -1, 0,
or 1 depending on which one has the lower base
address or which one is larger if they have
the same base address.
->contains($block) Compares two blocks. The second block will be
auto-converted from a string if it isn't
already a Net::Netmask object. Returns 1 if
the second block fits inside the first block.
Returns 0 otherwise.
->storeNetblock([$t]) Adds the current block to an table of network
blocks. The table can be used to query which
network block a given IP address is in.
The optional argument allows there to be more
than one table. By default, an internal table
is used. If more than one table is needed,
then supply a reference to a HASH to store the
data in.
->deleteNetblock([$t]) Deletes the current block from a table of
network blocks.
The optional argument allows there to be more
than one table. By default, an internal table
is used. If more than one table is needed,
then supply a reference to a HASH to store the
data in.
->checkNetblock([$t]) Returns true of the netblock is already in the
network table.
->tag($name [, $value]) Tag network blocks with your own data. The
first argument is the name of your tag (hash
key) and the second argument (if present) is
the new value. The old value is returned.
->split($parts) Splits a netmask into a number of sub
netblocks. This number must be a base 2 number
(2,4,8,16,etc.) and the number must not exceed
the number of IPs within this netmask.
For instance,
Net::Netmask->safe_new( '10.0.0.0/24' )->split(2)
is equivalent to
( Net::Netmask( '10.0.0.0/25'), Net::Netmask( '10.0.0.128/25' ) )
METHOD/FUNCTION COMBOS
findOuterNetblock(ip, [$t])
Search the table of network blocks (created
with storeNetBlock) to find if any of them
contain the given IP address. The IP address
can either be a string or a Net::Netmask
object (method invocation). If more than one
block in the table contains the IP address or
block, the largest network block will be the
one returned.
The return value is either a Net::Netmask
object or undef.
cidrs2inverse(block, @listOfBlocks)
Given a block and a list of blocks,
cidrs2inverse() will return a list of blocks
representing the IP addresses that are in the
block but not in the list of blocks. It finds
the gaps.
The block will be auto-converted from a string
if it isn't already a Net::Netmask object.
The list of blocks should be Net::Netmask
objects.
The return value is a list of Net::Netmask
objects.
OVERLOADING
"" Strinification is overloaded to be the
->desc() method.
cmp Numerical and string comparisons have been
overloaded to the ->cmpblocks() method. This
allows blocks to be sorted without specifying
a sort function.
FUNCTIONS
sort_by_ip_address This function is included in "Net::Netmask"
simply because there doesn't seem to be a
better place to put it on CPAN. It turns out
that there is one method for sorting dotted-
quads ("a.b.c.d") that is faster than all the
rest. This is that way. Use it as
"sort_by_ip_address(@list_of_ips)". That was
the theory anyway. Someone sent a faster
version ...
This method also will sort IPv6 addresses, but
is not performance optimized. It is correct,
however.
sort_network_blocks This function is a function to sort
Net::Netmask objects. It's faster than the
simpler "sort @blocks" that also works.
findNetblock(ip, [$t]) Search the table of network blocks (created
with storeNetBlock) to find if any of them
contain the given IP address. The IP address
is expected to be a string. If more than one
block in the table contains the IP address,
the smallest network block will be the one
returned.
The return value is either a Net::Netmask
object or undef.
findAllNetblock(ip, [$t])
Search the table of network blocks (created
with storeNetBlock) to find if any of them
contain the given IP address. The IP address
is expected to be a string. All network
blocks in the table that contain the IP
address will be returned.
The return value is a list of Net::Netmask
objects.
dumpNetworkTable([$t]) Returns a list of the networks in a network
table (as created by ->storeNetblock()).
range2cidrlist($startip, $endip)
Given a range of IP addresses, return a list
of blocks that span that range.
For example, range2cidrlist('216.240.32.128',
'216.240.36.127'), will return a list of
Net::Netmask objects that correspond to:
216.240.32.128/25
216.240.33.0/24
216.240.34.0/23
216.240.36.0/25
cidrs2contiglists(@listOfBlocks)
"cidrs2contiglists" will rearrange a list of
Net::Netmask objects such that contiguous sets
are in sublists and each sublist is
discontiguous with the next.
For example, given a list of Net::Netmask
objects corresponding to the following blocks:
216.240.32.128/25
216.240.33.0/24
216.240.36.0/25
"cidrs2contiglists" will return a list with
two sublists:
216.240.32.128/25 216.240.33.0/24
216.240.36.0/25
Overlapping blocks will be placed in the same
sublist.
cidrs2cidrs(@listOfBlocks)
"cidrs2cidrs" will collapse a list of
Net::Netmask objects by combining adjacent
blocks into larger blocks. It returns a list
of blocks that covers exactly the same IP
space. Overlapping blocks will be collapsed.
AUTHORS
Joelle Maslak <jmaslak@antelope.net> (current maintainer)
David Muir Sharnoff (original creator/author)
LICENSE
Copyright (C) 1998-2006 David Muir Sharnoff.
Copyright (C) 2011-2013 Google, Inc.
Copyright (C) 2018-2021 Joelle Maslak
This module may be used, modified and redistributed under the same
terms as Perl itself.
perl v5.34.0 2022-10-13 Net::Netmask(3pm)
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