const { compile } = require('struct-compile');
const { OsiModelLayers } = require('./osi');
const { IPProtocolTypes, IPv4OptionTypes } = require('./enums');
const { inetPton, inetNtop, ntohs } = require('#lib/converters');
const { AF_INET } = require('#lib/socket');
const { checksums } = require('#lib/bindings');
const child = require('./child');
const mixins = require('./mixins');
const IP_DONT_FRAGMENT = 0x40;
const IP_MORE_FRAGMENTS = 0x20;
const { IPv4Header } = compile(`
//@NE
struct IPv4Header {
//IP header length, has the value of 5 for IPv4
uint8_t headerLength:4;
//IP version number, has the value of 4 for IPv4
uint8_t version:4;
//type of service, same as Differentiated Services Code Point (DSCP)
uint8_t typeOfService;
//Entire packet (fragment) size, including header and data, in bytes
uint16_t totalLength;
//Identification field. Primarily used for uniquely identifying the group of fragments of a single IP datagram
uint16_t id;
//Fragment offset field, measured in units of eight-byte blocks (64 bits) @LE
uint16_t fragmentOffsetRaw;
//An eight-bit time to live field helps prevent datagrams from persisting (e.g. going in circles) on an internet. In practice, the field has become a hop count
uint8_t timeToLive;
//Defines the protocol used in the data portion of the IP datagram. Must be one of ::IPProtocolTypes
uint8_t protocol;
//Error-checking of the header
uint16_t checksum;
//@LE IPv4 address of the sender of the packet
uint32_t src;
//@LE IPv4 address of the receiver of the packet
uint32_t dst;
/*The options start here.*/
} __attribute__(packed);
`);
const { length: baseLength } = IPv4Header.prototype.config;
const childProto = {
[IPProtocolTypes.UDP]: 'UDP',
[IPProtocolTypes.TCP]: 'TCP',
[IPProtocolTypes.ICMP]: 'ICMP',
[IPProtocolTypes.GRE]: 'GRE',
[IPProtocolTypes.IGMP]: 'IGMP',
[IPProtocolTypes.AH]: 'AuthenticationHeader',
[IPProtocolTypes.ESP]: 'ESP',
[IPProtocolTypes.IPV6]: 'IPv6',
[IPProtocolTypes.VRRP]: 'VRRP',
};
const lookupChild = child.lookupChild(childProto);
const lookupKey = child.lookupKey(childProto);
/**
* IPv4 protocol layer
* @class
* @implements {Layer}
* @property {number} headerLength - IP header length, has the value of 5 for IPv4.
* @property {number} version - IP version number, has the value of 4 for IPv4.
* @property {number} typeOfService - type of service, same as Differentiated Services Code Point (DSCP)
* @property {number} totalLength - Entire packet (fragment) size, including header and data, in bytes
* @property {number} id - Identification field. Primarily used for uniquely identifying the group of fragments of a single IP datagram
* @property {number} fragmentOffsetRaw - Fragment offset field, measured in units of eight-byte blocks (64 bits) @LE
* @property {number} timeToLive - An eight-bit time to live field helps prevent datagrams from persisting (e.g. going in circles) on an internet. In practice, the field has become a hop count
* @property {number} protocol - Defines the protocol used in the data portion of the IP datagram. Must be one of ::IPProtocolTypes
* @property {number} checksum - Error-checking of the header
* @property {string} src - IPv4 address of the sender of the packet
* @property {string} dst - IPv4 address of the receiver of the packet
* @implements {Layer}
*/
class IPv4 extends IPv4Header {
name = 'IPv4';
/**
* @param {Buffer|Object} data - Input buffer or object with protocol fields.
* @param {Object} opts - Options for the layer.
*/
constructor(data, opts = {}) {
super(data);
mixins.ctor(this, data, opts);
this.length = opts.allocated ?? this.headerLength * 4;
}
static toAlloc = (data) => baseLength + IPv4.prototype.optionsLength(data.options);
static OptionTypes = IPv4OptionTypes;
osi = OsiModelLayers.Network;
/**
* The source IP address in human-readable format.
* @type {string}
*/
get src() {
return inetNtop(AF_INET, super.src);
}
set src(val) {
super.src = inetPton(AF_INET, val);
}
/**
* The destination IP address in human-readable format.
* @type {string}
*/
get dst() {
return inetNtop(AF_INET, super.dst);
}
set dst(val) {
super.dst = inetPton(AF_INET, val);
}
/**
* Calculates and updates the checksum for the IPv4 layer.
* This method mutates the object by setting the `checksum` property
* based on the current state of the `buffer`.
*/
calculateChecksum() {
this.checksum = checksums.ip(this.buffer.subarray(0, this.length));
}
/**
* @type {number}
*/
get fragmentOffsetFlags() {
return super.fragmentOffsetRaw & 0xE0;
}
/**
* @type {boolean}
*/
get isFragment() {
return ((this.fragmentOffsetFlags & IP_MORE_FRAGMENTS) != 0 || this.fragmentOffsetValue != 0);
}
/**
* @type {boolean}
*/
get isFirstFragment() {
return isFragment() && (this.fragmentOffsetValue == 0);
}
/**
* @type {boolean}
*/
get isLastFragment() {
return this.isFragment && ((this.fragmentOffsetFlags & IP_MORE_FRAGMENTS) == 0);
}
/**
* @type {number}
*/
get fragmentOffsetValue() {
return ntohs(super.fragmentOffsetRaw & 0xFF1F) * 8;
}
toObject() {
return {
...super.toObject(),
fragmentInfo: {
isFragment: this.isFragment,
value: this.fragmentOffsetValue,
flags: this.fragmentOffsetFlags,
},
options: [...this.options],
};
}
defaults(obj = {}, layers) {
if (!obj.headerLength) {
this.headerLength = IPv4.toAlloc(obj) / 4;
this.length = this.headerLength * 4;
}
if (!obj.version) {
this.version = 4;
}
if (!obj.typeOfService) {
this.typeOfService = 0;
}
if (!obj.id) {
this.id = 0;
}
if (!obj.timeToLive) {
this.timeToLive = 64;
}
if (!obj.totalLength) {
this.totalLength = this.length + (this.next?.length ?? 0);
}
if (!obj.protocol) {
if (!this.next) {
this.protocol = IPProtocolTypes.RAW;
}
this.protocol = lookupKey(layers, this.next) ?? IPProtocolTypes.RAW;
}
}
checksums(obj) {
if (!obj.checksum) {
this.calculateChecksum();
}
}
nextProto(layers) {
if (this.isFragment) {
return new layers.Payload(this._buf.subarray(this.length), this);
}
if (this.protocol == IPProtocolTypes.IPIP) {
const { version } = this;
if (version == 4) {
return new layers.IPv4(this._buf.subarray(this.length), this);
}
else if (version == 6) {
return new layers.IPv6(this._buf.subarray(this.length), this);
}
else {
throw new Error(`Invalid IP version ${version}`);
}
}
return lookupChild(layers, this.protocol, this);
}
};
mixins.withOptions(IPv4.prototype, { baseLength });
module.exports = { IPv4 };