raw-socket - homepage

This module implements raw sockets for Node.js.

This module has been created primarily to implement another, separate module, for the purpose of sending ICMP echo (ping) requests to many hosts at once. That module will be available shortly.

This module is installed using node package manager (npm):

# This module contains C++ source code which will be compiled
# during installation using node-gyp.  A suitable build chain
# must be configured before installation.

npm install raw-socket

It is loaded using the require() function:

var raw = require ("raw-socket");

Raw sockets can then be created, and data sent using Node.js Buffer objects:

var socket = raw.createSocket ({protocol: raw.Protocol.None});

socket.on ("message", function (buffer, source) {
    console.log ("received " + buffer.length + " bytes from " + source);
});

socket.send (buffer, 0, buffer.length, "1.1.1.1", function (error, bytes) {
    if (error)
        console.log (error.toString ());
});

Network Protocol Support

The raw sockets exposed by this module support IPv4 (soon to include IPv6).

Raw sockets are created using the operating systems socket() function, and the socket type SOCK_RAW specified.

Automatic Checksum Generation

This module offers the ability to automatically generate checksums in C++. This offers a performance benefit over generating checksums in JavaScript. This can be used to generate checksums for UDP, TCP and ICMP packets, for example.

Checksums produced by this module are 16 bits long, which falls in line with the checksums required for UDP, TCP and ICMP.

To enable automatic checksum generation specify the generateChecksums and checksumOffset parameters to the createSocket() method exposed by this module.

For example this module can be instructed to automatically generate ICMP checksums. ICMP checksums are located in bytes 3 and 4 of ICMP packets. Offsets start from 0 so 2 must be specified when creating the socket:

var options = {
    protocol: raw.Protocol.ICMP,
    generateChecksums: true,
    checksumOffset: 2
};

var socket = raw.createSocket (options);

When ICMP packets are sent using the created socket a 16 bit checksum will be generated and placed into bytes 3 and 4 before the packet is sent.

Automatic checksum generation can be disabled after socket creation using the generateChecksums() method exposed by the Socket class:

socket.generateChecksums (false).send (...).generateChecksums (true, 2);

Constants

The following sections describe constants exported and used by this module.

raw.Protocol

This object contains constants which can be used for the protocol option to the createSocket() function exposed by this module. This option specifies the protocol number to place in the protocol field of IP headers generated by the operating system.

The following constants are defined in this object:

• None - protocol number 0
• ICMP - protocol number 1
• TCP - protocol number 6
• UDP - protocol number 17

Using This Module

Raw sockets are represented by an instance of the Socket class. This module exports the createSocket() function which is used to create instances of the Socket class.

raw.createSocket ([options])

The createSocket() function instantiates and returns an instance of the Socket class:

// Default options
var options = {
    protocol: raw.Protocol.ICMP,
    bufferSize: 4096,
    generateChecksums: false,
    checksumOffset: 0
};

var socket = raw.createSocket (options);

The optional options parameter is an object, and can contain the following items:

• protocol - Either one of the constants defined in the raw.Protocol object or the protocol number to use for the socket, defaults to the consant raw.Protocol.None
• bufferSize - Size, in bytes, of the sockets internal receive buffer, defaults to 4096
• generateChecksums - Either true or false to enable or disable the automatic checksum generation feature, defaults to false
• checksumOffset - When generateChecksums is true specifies how many bytes to index into the send buffer to write automatically generated checksums, defaults to 0

An exception will be thrown if the underlying raw socket could not be created. The error will be an instance of the Error class.

When data is sent using the instantiated raw socket the operating system will automatically build IP headers and place them in outgoing packets.

The protocol parameter, or its default value of the constant raw.Protocol.None, will be specified in the protocol field of each IP header.

Upon receiving packets IP headers are NOT removed by the operating system. IP headers in received packets will be included in data presented by this module.

This module hopes to support the IP_HDRINCL socket option in the near future, which controls the inclusion of IP headers in outgoing packets.

socket.on ("close", callback)

The close event is emitted by the socket when the underlying raw socket is closed.

No arguments are passed to the callback.

The following example prints a message to the console when the socket is closed:

socket.on ("close", function () {
    console.log ("socket closed");
});

socket.on ("error", callback)

The error event is emitted by the socket when an error occurs sending or receiving data.

The following arguments will be passed to the callback function:

• error - An instance of the Error class, the exposed message attribute will contain a detailed error message.

The following example prints a message to the console when an error occurs, after which the socket is closed:

socket.on ("error", function (error) {
    console.log (error.toString ());
    socket.close ();
});

socket.on ("message", callback)

The message event is emitted by the socket when data has been received.

The following arguments will be passed to the callback function:

• buffer - A Node.js Buffer object containing the data received, the buffer will be sized to fit the data received, that is the length attribute of buffer will specify how many bytes were received
• address - Dotted quad formatted source IP address of the message, e.g "192.168.1.254"

The following example prints received messages in hexadecimal to the console:

socket.on ("message", function (message, address) {
    console.log ("received " + buffer.length + " bytes from " + address
            + ": " + buffer.toString ("hex"));
});

socket.generateChecksums (generate, offset)

The generateChecksums() method is used to specify whether automatic checksum generation should be performed by the socket.

The generate parameter is either true or false to enable or disable the feature. The optional offset parameter specifies how many bytes to index into the send buffer when writing the generated checksum to the send buffer.

The following example enables automatic checksum generation at offset 2 resulting in checksums being written to byte 3 and 4 of the send buffer (offsets start from 0, meaning byte 1):

socket.generateChecksums (true, 2);

socket.send (buffer, offset, length, address, callback)

The send() method sends data to a remote host.

The buffer parameter is a Node.js Buffer object containing the data to be sent. The length parameter specifies how many bytes from buffer, beginning at offset offset, to send. The address parameter contains the dotted quad formatted IP address of the remote host to send the data to. The callback function is called once the data has been sent. The following arguments will be passed to the callback function:

• error - Instance of the Error class, or null if no error occurred
• bytes - Number of bytes sent

The following example sends a ICMP ping message to a remote host:

// ICMP echo (ping) request, checksum should be ok
var buffer = new Buffer ([
        0x08, 0x00, 0x43, 0x52, 0x00, 0x01, 0x0a, 0x09,
        0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,
        0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, 0x70,
        0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x61,
        0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69]);

socket.send (buffer, 0, buffer.length, target, function (error, bytes) {
    if (error)
        console.log (error.toString ());
    else
        console.log ("sent " + bytes + " bytes");
});

Example Programs

Example programs are included under the modules example directory.

Bugs & Known Issues

None, yet!

Bug reports should be sent to stephen.vickers.sv@gmail.com.

Changes

Version 1.0.0 - 29/01/2013

• Initial release

Version 1.0.1 - 01/02/2013

• Move SOCKET_ERRNO define from raw.cc to raw.h
• Error in exception thrown by SocketWrap::New in raw.cc stated that two arguments were required, this should be one
• Corrections to the README.md
• Missing includes causes compilation error on some systems (maybe Node version dependant)

Version 1.0.2 - 02/02/2013

• Support automatic checksum generation

Roadmap

In no particular order:

• Enhance performance by moving the send queue into the C++ raw::SocketWrap class
• Support IP_HDRINCL socket option
• Support IPv6

Suggestions and requirements should be sent to stephen.vickers.sv@gmail.com.

License

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses.

Author

Stephen Vickers stephen.vickers.sv@gmail.com