Ethernet frame is a OSI data link layer (layer 2) protocol data unit for Ethernet networks. In practice, many other networks and/or in-file dumps adopted the same format for encapsulation purposes.
This page hosts a formal specification of Ethernet frame (layer 2, IEEE 802.3) 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 EthernetFrame(new KaitaiStream(arrayBuffer));
After that, one can get various attributes from the structure by accessing fields or properties like:
data.dstMac // => Destination MAC address
data.etherType // => Ether type can be specied in several places in the frame. If
first location bears special marker (0x8100), then it is not the
real ether frame yet, an additional payload (`tci`) is expected
and real ether type is upcoming next.
// 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', './Ipv4Packet', './Ipv6Packet'], factory);
} else if (typeof module === 'object' && module.exports) {
module.exports = factory(require('kaitai-struct/KaitaiStream'), require('./Ipv4Packet'), require('./Ipv6Packet'));
} else {
root.EthernetFrame = factory(root.KaitaiStream, root.Ipv4Packet, root.Ipv6Packet);
}
}(typeof self !== 'undefined' ? self : this, function (KaitaiStream, Ipv4Packet, Ipv6Packet) {
/**
* Ethernet frame is a OSI data link layer (layer 2) protocol data unit
* for Ethernet networks. In practice, many other networks and/or
* in-file dumps adopted the same format for encapsulation purposes.
* @see {@link https://ieeexplore.ieee.org/document/7428776|Source}
*/
var EthernetFrame = (function() {
EthernetFrame.EtherTypeEnum = Object.freeze({
IPV4: 2048,
X_75_INTERNET: 2049,
NBS_INTERNET: 2050,
ECMA_INTERNET: 2051,
CHAOSNET: 2052,
X_25_LEVEL_3: 2053,
ARP: 2054,
IEEE_802_1Q_TPID: 33024,
IPV6: 34525,
2048: "IPV4",
2049: "X_75_INTERNET",
2050: "NBS_INTERNET",
2051: "ECMA_INTERNET",
2052: "CHAOSNET",
2053: "X_25_LEVEL_3",
2054: "ARP",
33024: "IEEE_802_1Q_TPID",
34525: "IPV6",
});
function EthernetFrame(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root || this;
this._read();
}
EthernetFrame.prototype._read = function() {
this.dstMac = this._io.readBytes(6);
this.srcMac = this._io.readBytes(6);
this.etherType1 = this._io.readU2be();
if (this.etherType1 == EthernetFrame.EtherTypeEnum.IEEE_802_1Q_TPID) {
this.tci = new TagControlInfo(this._io, this, this._root);
}
if (this.etherType1 == EthernetFrame.EtherTypeEnum.IEEE_802_1Q_TPID) {
this.etherType2 = this._io.readU2be();
}
switch (this.etherType) {
case EthernetFrame.EtherTypeEnum.IPV4:
this._raw_body = this._io.readBytesFull();
var _io__raw_body = new KaitaiStream(this._raw_body);
this.body = new Ipv4Packet(_io__raw_body, this, null);
break;
case EthernetFrame.EtherTypeEnum.IPV6:
this._raw_body = this._io.readBytesFull();
var _io__raw_body = new KaitaiStream(this._raw_body);
this.body = new Ipv6Packet(_io__raw_body, this, null);
break;
default:
this.body = this._io.readBytesFull();
break;
}
}
/**
* Tag Control Information (TCI) is an extension of IEEE 802.1Q to
* support VLANs on normal IEEE 802.3 Ethernet network.
*/
var TagControlInfo = EthernetFrame.TagControlInfo = (function() {
function TagControlInfo(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root || this;
this._read();
}
TagControlInfo.prototype._read = function() {
this.priority = this._io.readBitsIntBe(3);
this.dropEligible = this._io.readBitsIntBe(1) != 0;
this.vlanId = this._io.readBitsIntBe(12);
}
/**
* Priority Code Point (PCP) is used to specify priority for
* different kinds of traffic.
*/
/**
* Drop Eligible Indicator (DEI) specifies if frame is eligible
* to dropping while congestion is detected for certain classes
* of traffic.
*/
/**
* VLAN Identifier (VID) specifies which VLAN this frame
* belongs to.
*/
return TagControlInfo;
})();
/**
* Ether type can be specied in several places in the frame. If
* first location bears special marker (0x8100), then it is not the
* real ether frame yet, an additional payload (`tci`) is expected
* and real ether type is upcoming next.
*/
Object.defineProperty(EthernetFrame.prototype, 'etherType', {
get: function() {
if (this._m_etherType !== undefined)
return this._m_etherType;
this._m_etherType = (this.etherType1 == EthernetFrame.EtherTypeEnum.IEEE_802_1Q_TPID ? this.etherType2 : this.etherType1);
return this._m_etherType;
}
});
/**
* Destination MAC address
*/
/**
* Source MAC address
*/
/**
* Either ether type or TPID if it is a IEEE 802.1Q frame
*/
return EthernetFrame;
})();
return EthernetFrame;
}));