node-tuntap

Node-tuntap is a node module that allows creating and using tun and tap interfaces in javascript.

TL;DR

Simple sample :

var tuntap = require('./index.js');

try {
	var tt = tuntap({
		type: 'tun',
		name: 'tun12',
		mtu: 1500,
		addr: '192.168.123.1',
		dest: '192.168.123.2',
		mask: '255.255.255.192',
		ethtype_comp: 'half',
		persist: false,
		up: true,
		running: true,
	});
}
catch(e) {
	console.log('Tuntap creation error: ', e);
	process.exit(0);
}

tt.pipe(tt);

Building/installing

To build the module, just run make. node-gyp is required to build it.

There is currently no way to install it. You will have to copy the files in the right places by hand.

Available options

These options can be given in the tuntap constructor, in an object.

• type The interface type. May be 'tun' or 'tap'. The default is 'tun'.
• name The name of the interface. If nothing is given, the next available name will be used (selected by the Operating System).
• mtu The MTU, in bytes. The default value is 1500.
• addr The network address of the interface. If nothing is given, no address is set.
• dest The network remote address of the tunnel. If nothing is given, no address is set.
• mask The network mask of the interface, in dotted notation.
• ethtype_comp The compression of the ethernet header (Only for the 'tap' type). May be 'none', 'half' or 'full'. The default is 'none'. See the next part for more explanations.
• persist Tells if the interface will persist when it will be closed. Defaults to true.
• up Tells if the interface should be up. Defaults to true.
• running Tells if the interface should be running. Defaults to true.

On a tun or tap interface, the operating system adds 4 bytes in front of each datagram, that contains the protocol code of the datagram. The ethtype_comp option can be used to reduce the overhead of these 4 bytes. The 'none' option send the full header as given by the interface (No encoding/decoding is done). the 'half' option remove the two first bytes of the header (They are often unused, since the protocol type is often 2 bytes only (If you know an exception, tell me please)). The 'full' option maps the 4 bytes most common values to a 1 byte equivalent, used internally in the module (See the ethertypes.itm files for a list of supported codes). The supported codes for the 'full' option are only for the 'tun' mode.

Available methods

• open(options) Open the interface (When a new interface is created, it is already open. Close it first to reopen it later). The options are the same as in the constructor.
• close() Close the interface. This function takes no arguments.
• set(options) Set the given options on the interface. The object given can contain the same parameters as the constructor, except the type key.
• unset(array) Unset the given options (Can be useful to unset an IP Address). The only parameter is an array of constructor keys to unset. The available elements are addr, mtu, persist, up, running and ethtype_comp.

Two classes are also available :

• tuntap.muxer
• tuntap.demuxer

These classes can be used to wrap packets from/to tuntap interfaces, for example if you have to send them through a tcp connection. They take only one parameter in the constructor : the datagram maximum size (for an MTU of 1500 on a TAP interface, the maximum size can be 1518, 1516 ot 1515, if you are using a 'none', 'half' or 'full' compression with ethtype_comp. See the ethernet frame format for more informations).

Usage example :

var tt = tuntap();
var muxer = tuntap.muxer(1504);
var demuxer = tuntap.demuxer(1504);

[...]

tt.pipe(muxer).pipe(someTcpConnection).pipe(demuxer).pipe(tt);

Any of the tuntap, tuntap.muxer and tuntap.demuxer classes are streams and can be used like it (.on('data'), .write(), .pipe()).

TODO

• Support IPv6 for IP addresses
• Check if it works on BSD
• Allow custom mapping for the ethtype_comp option
• Maybe add a windows support?...