cap-decoders

Description
===========

Network packet decoders (extracted from cap module)

Requirements
============

* node.js -- v4.0.0 or newer

Install
============

npm install cap

Examples
========

* Capture and decode all outgoing TCP data packets destined for port 80 on the interface for 192.168.0.10:

``javascript
var Cap = require('cap').Cap;
var decoders = require('cap-decoders');
var PROTOCOL = decoders.PROTOCOL;

var c = new Cap();
var device = Cap.findDevice('192.168.0.10');
var filter = 'tcp and dst port 80';
var bufSize = 10 1024 1024;
var buffer = Buffer.alloc(65535);

var linkType = c.open(device, filter, bufSize, buffer);

c.setMinBytes && c.setMinBytes(0);

c.on('packet', function(nbytes, trunc) {
console.log('packet: length ' + nbytes + ' bytes, truncated? '
+ (trunc ? 'yes' : 'no'));

// raw packet data === buffer.slice(0, nbytes)

if (linkType === 'ETHERNET') {
var ret = decoders.Ethernet(buffer);

if (ret.info.type === PROTOCOL.ETHERNET.IPV4) {
console.log('Decoding IPv4 ...');

ret = decoders.IPV4(buffer, ret.offset);
console.log('from: ' + ret.info.srcaddr + ' to ' + ret.info.dstaddr);

if (ret.info.protocol === PROTOCOL.IP.TCP) {
var datalen = ret.info.totallen - ret.hdrlen;

console.log('Decoding TCP ...');

ret = decoders.TCP(buffer, ret.offset);
console.log(' from port: ' + ret.info.srcport + ' to port: ' + ret.info.dstport);
datalen -= ret.hdrlen;
console.log(buffer.toString('binary', ret.offset, ret.offset + datalen));
} else if (ret.info.protocol === PROTOCOL.IP.UDP) {
console.log('Decoding UDP ...');

ret = decoders.UDP(buffer, ret.offset);
console.log(' from port: ' + ret.info.srcport + ' to port: ' + ret.info.dstport);
console.log(buffer.toString('binary', ret.offset, ret.offset + ret.info.length));
} else
console.log('Unsupported IPv4 protocol: ' + PROTOCOL.IP[ret.info.protocol]);
} else
console.log('Unsupported Ethertype: ' + PROTOCOL.ETHERNET[ret.info.type]);
}
});
`

Static methods
-----------------------

The following methods are available off of require('cap-decoders')`. They parse the relevant protocol header and return an object containing the parsed information:

* Link Layer Protocols

* Ethernet(< _Buffer_ buf[, < _integer_ >bufOffset=0])

* Internet Layer Protocols

* IPV4(< _Buffer_ buf[, < _integer_ >bufOffset=0])

* IPV6(< _Buffer_ buf[, < _integer_ >bufOffset=0])

* ICMPV4(< _Buffer_ buf, < _integer_ >nbytes[, < _integer_ >bufOffset=0])

* Transport Layer Protocols

* TCP(< _Buffer_ buf[, < _integer_ >bufOffset=0])

* UDP(< _Buffer_ buf[, < _integer_ >bufOffset=0])

* SCTP(< _Buffer_ buf, < _integer_ >nbytes[, < _integer_ >bufOffset=0])