ipaddr.js — an IPv6 and IPv4 address manipulation library

ipaddr.js is a small (1.9K minified and gzipped) library for manipulating IP addresses in JavaScript environments. It runs on both CommonJS runtimes (e.g. nodejs) and in a web browser.

ipaddr.js allows you to verify and parse string representation of an IP address, match it against a CIDR range or range list, determine if it falls into some reserved ranges (examples include loopback and private ranges), and convert between IPv4 and IPv4-mapped IPv6 addresses.

# Installation

`npm install ipaddr.js`

or

`bower install ipaddr.js`

# API

ipaddr.js defines one object in the global scope: `ipaddr`. In CommonJS, it is exported from the module:

var ipaddr = require('ipaddr.js');

The API consists of several global methods and two classes: ipaddr.IPv6 and ipaddr.IPv4.

## Global methods

There are three global methods defined: `ipaddr.isValid`, `ipaddr.parse` and `ipaddr.process`. All of them receive a string as a single parameter.

The `ipaddr.isValid` method returns `true` if the address is a valid IPv4 or IPv6 address, and `false` otherwise. It does not throw any exceptions.

The `ipaddr.parse` method returns an object representing the IP address, or throws an `Error` if the passed string is not a valid representation of an IP address.

The `ipaddr.process` method works just like the `ipaddr.parse` one, but it automatically converts IPv4-mapped IPv6 addresses to their IPv4 counterparts before returning. It is useful when you have a Node.js instance listening on an IPv6 socket, and the `net.ivp6.bindv6only` sysctl parameter (or its equivalent on non-Linux OS) is set to 0. In this case, you can accept IPv4 connections on your IPv6-only socket, but the remote address will be mangled. Use `ipaddr.process` method to automatically demangle it.

## Object representation

Parsing methods return an object which descends from `ipaddr.IPv6` or `ipaddr.IPv4`. These objects share some properties, but most of them differ.

### Shared properties

One can determine the type of address by calling `addr.kind()`. It will return either `"ipv6"` or `"ipv4"`.

An address can be converted back to its string representation with `addr.toString()`. Note that this method:

- does not return the original string used to create the object (in fact, there is no way of getting that string)
- returns a compact representation (when it is applicable)

A `match(range, bits)` method can be used to check if the address falls into a certain CIDR range. Note that an address can be (obviously) matched only against an address of the same type.

For example:

var addr = ipaddr.parse("2001:db8:1234::1");
var range = ipaddr.parse("2001:db8::");
addr.match(range, 32); // => true

Alternatively, `match` can also be called as `match([range, bits])`. In this way, it can be used together with the `parseCIDR(string)` method, which parses an IP address together with a CIDR range.

For example:

var addr = ipaddr.parse("2001:db8:1234::1");
addr.match(ipaddr.parseCIDR("2001:db8::/32")); // => true

A `range()` method returns one of predefined names for several special ranges defined by IP protocols. The exact names (and their respective CIDR ranges) can be looked up in the source: IPv6 ranges and IPv4 ranges. Some common ones include `"unicast"` (the default one) and `"reserved"`.

You can match against your own range list by using `ipaddr.subnetMatch(address, rangeList, defaultName)` method. It can work with a mix of IPv6 or IPv4 addresses, and accepts a name-to-subnet map as the range list. For example:

var rangeList = {
documentationOnly: [ ipaddr.parse('2001:db8::'), 32 ],
tunnelProviders: [
[ ipaddr.parse('2001:470::'), 32 ], // he.net
[ ipaddr.parse('2001:5c0::'), 32 ] // freenet6
]
};
ipaddr.subnetMatch(ipaddr.parse('2001:470:8:66::1'), rangeList, 'unknown'); // => "tunnelProviders"

The addresses can be converted to their byte representation with `toByteArray()`. (Actually, JavaScript mostly does not know about byte buffers. They are emulated with arrays of numbers, each in range of 0..255.)

var bytes = ipaddr.parse('2a00:1450:8007::68').toByteArray(); // ipv6.google.com
bytes // => [42, 0x00, 0x14, 0x50, 0x80, 0x07, 0x00, <zeroes...>, 0x00, 0x68 ]

The `ipaddr.IPv4` and `ipaddr.IPv6` objects have some methods defined, too. All of them have the same interface for both protocols, and are similar to global methods.

`ipaddr.IPvX.isValid(string)` can be used to check if the string is a valid address for particular protocol, and `ipaddr.IPvX.parse(string)` is the error-throwing parser.

`ipaddr.IPvX.isValid(string)` uses the same format for parsing as the POSIX `inet_ntoa` function, which accepts unusual formats like `0xc0.168.1.1` or `0x10000000`. The function `ipaddr.IPv4.isValidFourPartDecimal(string)` validates the IPv4 address and also ensures that it is written in four-part decimal format.

### IPv6 properties

Sometimes you will want to convert IPv6 not to a compact string representation (with the `::` substitution); the `toNormalizedString()` method will return an address where all zeroes are explicit.

For example:

var addr = ipaddr.parse("2001:0db8::0001");
addr.toString(); // => "2001:db8::1"
addr.toNormalizedString(); // => "2001:db8:0:0:0:0:0:1"

The `isIPv4MappedAddress()` method will return `true` if this address is an IPv4-mapped one, and `toIPv4Address()` will return an IPv4 object address.

To access the underlying binary representation of the address, use `addr.parts`.

var addr = ipaddr.parse("2001:db8:10::1234:DEAD");
addr.parts // => [0x2001, 0xdb8, 0x10, 0, 0, 0, 0x1234, 0xdead]

A IPv6 zone index can be accessed via `addr.zoneId`:

var addr = ipaddr.parse("2001:db8::%eth0");
addr.zoneId // => 'eth0'

### IPv4 properties

`toIPv4MappedAddress()` will return a corresponding IPv4-mapped IPv6 address.

To access the underlying representation of the address, use `addr.octets`.

var addr = ipaddr.parse("192.168.1.1");
addr.octets // => [192, 168, 1, 1]

`prefixLengthFromSubnetMask()` will return a CIDR prefix length for a valid IPv4 netmask or null if the netmask is not valid.

ipaddr.IPv4.parse('255.255.255.240').prefixLengthFromSubnetMask() == 28
ipaddr.IPv4.parse('255.192.164.0').prefixLengthFromSubnetMask() == null

`subnetMaskFromPrefixLength()` will return an IPv4 netmask for a valid CIDR prefix length.

ipaddr.IPv4.subnetMaskFromPrefixLength(24) == "255.255.255.0"
ipaddr.IPv4.subnetMaskFromPrefixLength(29) == "255.255.255.248"

`broadcastAddressFromCIDR()` will return the broadcast address for a given IPv4 interface and netmask in CIDR notation.

ipaddr.IPv4.broadcastAddressFromCIDR("172.0.0.1/24") == "172.0.0.255"

`networkAddressFromCIDR()` will return the network address for a given IPv4 interface and netmask in CIDR notation.

ipaddr.IPv4.networkAddressFromCIDR("172.0.0.1/24") == "172.0.0.0"

### Conversion

IPv4 and IPv6 can be converted bidirectionally to and from network byte order (MSB) byte arrays.

The `fromByteArray()` method will take an array and create an appropriate IPv4 or IPv6 object if the input satisfies the requirements. For IPv4 it has to be an array of four 8-bit values, while for IPv6 it has to be an array of sixteen 8-bit values.

For example:

var addr = ipaddr.fromByteArray([0x7f, 0, 0, 1]);
addr.toString(); // => "127.0.0.1"

or

var addr = ipaddr.fromByteArray([0x20, 1, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1])
addr.toString(); // => "2001:db8::1"

Both objects also offer a `toByteArray()` method, which returns an array in network byte order (MSB).

For example:

var addr = ipaddr.parse("127.0.0.1");
addr.toByteArray(); // => [0x7f, 0, 0, 1]

or

var addr = ipaddr.parse("2001:db8::1");
addr.toByteArray(); // => [0x20, 1, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1]