netmask

What is netmask?

The netmask npm package is used for parsing and manipulating network addresses (IPv4 and IPv6). It allows for operations such as parsing CIDR notation, calculating network ranges, subnetting, and checking if an IP address is part of a network. This package is particularly useful for network-related programming tasks, security analysis, and systems administration.

What are netmask's main functionalities?

Parsing and creating netmasks

This feature allows for the creation of netmask objects by parsing CIDR notation. It enables the extraction of the base address and the subnet mask.

const { Netmask } = require('netmask');
const block = new Netmask('192.168.1.0/24');
console.log(block.base); // '192.168.1.0'
console.log(block.mask); // '255.255.255.0'

Checking if an IP is within a subnet

This functionality enables checking whether a specific IP address falls within a defined subnet, which is useful for network security and management.

const { Netmask } = require('netmask');
const block = new Netmask('192.168.1.0/24');
console.log(block.contains('192.168.1.123')); // true
console.log(block.contains('192.168.2.123')); // false

Iterating over all IPs in a subnet

This feature allows for iterating over each IP address within a subnet. It's particularly useful for network scanning or allocation tasks.

const { Netmask } = require('netmask');
const block = new Netmask('192.168.1.0/30');
block.forEach(ip => console.log(ip));

Other packages similar to netmask

ip

The 'ip' package provides utilities for handling IPv4 and IPv6 addresses. While it offers functionality for IP manipulation, it lacks the direct subnetting and CIDR parsing capabilities of netmask, focusing more on IP address validation and manipulation.

cidr-js

The 'cidr-js' package is used for calculating CIDR subnet information. It provides functionality similar to netmask for working with CIDR notations, such as calculating subnet ranges and checking if an IP is within a CIDR range. However, it might not offer as comprehensive IP manipulation features outside of CIDR operations.

README

Netmask

The Netmask class parses and understands IPv4 CIDR blocks so they can be explored and compared. This module is highly inspired by Perl Net::Netmask module.

Synopsis

var Netmask = require('netmask').Netmask

var block = new Netmask('10.0.0.0/12');
block.base;                     // 10.0.0.0
block.mask;                     // 255.240.0.0
block.bitmask;                  // 12
block.hostmask;                 // 0.15.255.255
block.broadcast;                // 10.15.255.255
block.size;                     // 1048576
block.first;                    // 10.0.0.1
block.last;                     // 10.15.255.254

block.contains('10.0.8.10');    // true
block.contains('10.8.0.10');    // true
block.contains('192.168.1.20'); // false

block.forEach(function(ip, long, index));

block.next()                    // Netmask('10.16.0.0/12')

Constructing

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 form.
'216.240.32.0/255.255.255.0'
'216.240.32.0', '255.255.255.0'
'216.240.32.0', 0xffffff00
'216.240.32.4'                  // A /32 block.
'0330.0360.040.04'              // Octal form
'0xd8.0xf0.0x20.0x4'            // Hex form

API

• .base: The 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.
• .mask: The netmask as a string (eg: 255.255.255.0).
• .hostmask: The host mask which is the opposite of the netmask (eg: 0.0.0.255).
• .bitmask: The netmask as a number of bits in the network portion of the address for this block (eg: 24).
• .size: The number of IP addresses in a block (eg: 256).
• .broadcast: The blocks broadcast address (eg: 192.168.1.0/24 => 192.168.1.255)
• .first, .last: First and last useable address
• .contains(ip or block): Returns a true if the IP number ip is part of the network. That is, a true value is returned if ip is between base and broadcast. If a Netmask object or a block is given, it returns true only of the given block fits inside the network.
• .forEach(fn): Similar to the Array prototype method. It loops through all the useable addresses, ie between first and last.
• .next(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.
• .toString(): The netmask in base/bitmask format (e.g., '216.240.32.0/24')

Installation

$ npm install netmask

License

(The MIT License)

Copyright (c) 2011 Olivier Poitrey [e-mail]

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Changelog

v2.0.0 (Mar 19, 2021)

Breaking Change

Previous API was treating IPs with less than four bytes as IP with a netmask of the size of the provided bytes (1=8, 2=16, 3=24) and was interpreting the IP as if it was completed with 0s on the right side.

Proper IP parsing for these is to consider missing bytes as being 0s on the left side.

Mask size is no longer infered by the number of bytes provided.

This means that the input 216.240 will no longer be interpreted as 216.240.0.0/16, but as 0.0.216.240/32, as per convention.

See the change.

Bugfixes

• Fix improper parsing of hex bytes