This page hosts a formal specification of IPv4 network packet using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
All parsing code for JavaScript generated by Kaitai Struct depends on the JavaScript runtime library. You have to install it before you can parse data.
The JavaScript runtime library is available at npm:
npm install kaitai-structSee the usage examples in the JavaScript notes.
Parse structure from an ArrayBuffer:
var arrayBuffer = ...;
var data = new Ipv4Packet(new KaitaiStream(arrayBuffer));
After that, one can get various attributes from the structure by accessing fields or properties like:
data.b1 // => get b1
// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
(function (root, factory) {
if (typeof define === 'function' && define.amd) {
define(['kaitai-struct/KaitaiStream', './ProtocolBody'], factory);
} else if (typeof module === 'object' && module.exports) {
module.exports = factory(require('kaitai-struct/KaitaiStream'), require('./ProtocolBody'));
} else {
root.Ipv4Packet = factory(root.KaitaiStream, root.ProtocolBody);
}
}(typeof self !== 'undefined' ? self : this, function (KaitaiStream, ProtocolBody) {
var Ipv4Packet = (function() {
function Ipv4Packet(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root || this;
this._read();
}
Ipv4Packet.prototype._read = function() {
this.b1 = this._io.readU1();
this.b2 = this._io.readU1();
this.totalLength = this._io.readU2be();
this.identification = this._io.readU2be();
this.b67 = this._io.readU2be();
this.ttl = this._io.readU1();
this.protocol = this._io.readU1();
this.headerChecksum = this._io.readU2be();
this.srcIpAddr = this._io.readBytes(4);
this.dstIpAddr = this._io.readBytes(4);
this._raw_options = this._io.readBytes((this.ihlBytes - 20));
var _io__raw_options = new KaitaiStream(this._raw_options);
this.options = new Ipv4Options(_io__raw_options, this, this._root);
this._raw_body = this._io.readBytes((this.totalLength - this.ihlBytes));
var _io__raw_body = new KaitaiStream(this._raw_body);
this.body = new ProtocolBody(_io__raw_body, this, null, this.protocol);
}
var Ipv4Options = Ipv4Packet.Ipv4Options = (function() {
function Ipv4Options(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root || this;
this._read();
}
Ipv4Options.prototype._read = function() {
this.entries = [];
var i = 0;
while (!this._io.isEof()) {
this.entries.push(new Ipv4Option(this._io, this, this._root));
i++;
}
}
return Ipv4Options;
})();
var Ipv4Option = Ipv4Packet.Ipv4Option = (function() {
function Ipv4Option(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root || this;
this._read();
}
Ipv4Option.prototype._read = function() {
this.b1 = this._io.readU1();
this.len = this._io.readU1();
this.body = this._io.readBytes((this.len > 2 ? (this.len - 2) : 0));
}
Object.defineProperty(Ipv4Option.prototype, 'copy', {
get: function() {
if (this._m_copy !== undefined)
return this._m_copy;
this._m_copy = ((this.b1 & 128) >>> 7);
return this._m_copy;
}
});
Object.defineProperty(Ipv4Option.prototype, 'optClass', {
get: function() {
if (this._m_optClass !== undefined)
return this._m_optClass;
this._m_optClass = ((this.b1 & 96) >>> 5);
return this._m_optClass;
}
});
Object.defineProperty(Ipv4Option.prototype, 'number', {
get: function() {
if (this._m_number !== undefined)
return this._m_number;
this._m_number = (this.b1 & 31);
return this._m_number;
}
});
return Ipv4Option;
})();
Object.defineProperty(Ipv4Packet.prototype, 'version', {
get: function() {
if (this._m_version !== undefined)
return this._m_version;
this._m_version = ((this.b1 & 240) >>> 4);
return this._m_version;
}
});
Object.defineProperty(Ipv4Packet.prototype, 'ihl', {
get: function() {
if (this._m_ihl !== undefined)
return this._m_ihl;
this._m_ihl = (this.b1 & 15);
return this._m_ihl;
}
});
Object.defineProperty(Ipv4Packet.prototype, 'ihlBytes', {
get: function() {
if (this._m_ihlBytes !== undefined)
return this._m_ihlBytes;
this._m_ihlBytes = (this.ihl * 4);
return this._m_ihlBytes;
}
});
return Ipv4Packet;
})();
return Ipv4Packet;
}));