NETMASK(1)

NAME
Net::Netmask - parse, manipulate and lookup IP network blocks

SYNOPSIS
        use Net::Netmask;
        $block = new Net::Netmask (network block)
        $block = new Net::Netmask (network block, netmask)
        $block = new2 Net::Netmask (network block)
        $block = new2 Net::Netmask (network block, netmask)
        print $block->desc()            # a.b.c.d/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]);
        for $ip ($block->enumerate([$bitstep])) { }
        for $zone ($block->inaddr()) { }
        my $table = {};
        $block->storeNetblock([$table])
        $block->deleteNetblock([$table])
        $block = findNetblock(ip, [$table])
        $block = findOuterNetblock(ip, [$table])
        @blocks = findAllNetblock(ip, [$table])
        @blocks = range2cidrlist($beginip, $endip);
        @listofblocks = cidrs2contiglists(@blocks);
        @sorted_ip_addrs = sort_by_ip_address(@unsorted_ip_addrs)

DESCRIPTION
Net::Netmask parses and understands IPv4 CIDR blocks. It's built with an object-oriented interface. Nearly all functions are methods that operate on a Net::Netmask object.

There are methods that provide the nearly all bits of information about a network block that you might want.

There are also functions to put a network block into a table and then later lookup network blocks by IP address in 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.

CONSTRUCTING
Net::Netmask objects are created with an IP address and optionally a mask. There are many forms that are recognized: The preferred form. A /32 block. Always a /24 block. Always a /16 block. Always a /8 block. 0.0.0.0/0 (the default route)

There are two constructor methods: `new' and `new2'. The difference is that `new2' will return undef for invalid netmasks and `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 `new2' the error can be found as Net::Netmask::errstr or $Net::Netmask::error.

METHODS
Returns base address of the network block as a string. Eg: 216.240.32.0. Base does not give an indication of the size of the network block. Returns the netmask as a string. Eg: 255.255.255.0. Returns the host mask which is the oposite of the netmask. Eg: 0.0.0.255. Returns the netmask as a number of bits in the network portion of the address for this block. Eg: 24. Returns the number of IP addresses in a block. Eg: 256. The blocks broadcast address. (The last IP address inside the block.) Eg: 192.168.1.0/24 => 192.168.1.255 The first IP address following the block. (The IP address following the broadcase address.) Eg: 192.168.1.0/24 => 192.168.2.0 Returns a true if the IP number $ip matches the given network. That is, a true value is returned if $ip is between base() amd 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")

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) || die;
  $pos += 0;
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 larges block that the current block's address would allow it to be. The size is given in bits. Eg: 23. 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). 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 adress, use nth(-2). Returns an inline list of tuples. There is a tuple for each DNS zone name 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: '82.174.140.in-addr.arpa', 0, 255, '83.174.140.in-addr.arpa', 0, 255. The list returned for the block '216.240.32.64/27' would be: '82.174.140.in-addr.arpa', 64, 95. 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. 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.

FUNCTIONS
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)'. 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. 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 largest network block will be the one returned.

The return value is either a Net::Netmask object or undef. 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. 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 corrospond to:

        216.240.32.128/25
        216.240.33.0/24
        216.240.34.0/23
        216.240.36.0/25
`cidrs2contiglists' will rearange a list of Net::Netmask objects such that contigueous sets are in sublists and each sublist is discontigeous with the next.

For example, given a list of Net::Netmask objects corrosponding 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
The behavior for overlapping blocks is not currently defined.

LICENSE
Copyright (C) 1998, 2001 David Muir Sharnoff. License hereby granted for anyone to use, modify or redistribute this module at their own risk. Please feed useful changes back to muir@idiom.com.