swift-ietf/swift-rfc-791

Swift implementation of RFC 791: Internet Protocol (IPv4).

Overview

This package is the pure domain model of the IPv4 header defined in RFC 791 (September 1981): every header field is a distinct type carrying its invariants, derived quantities and well-known values, and the IPv4 address carries its class and its dotted-decimal text form. It has no parser, serializer or formatter dependencies.

The wire forms live in the sibling package swift-rfc-791-coder: <Type>.Coder over a byte cursor for every field, Binary.Serializable conformances, and the address's ASCII.Parseable/ASCII.Serializable text form and Binary.Parseable.

Products

RFC 791 — the domain model.
RFC 791 Standard Library Integration — RFC_791.IPv4.Address(::::) from four UInt8 octets.
RFC 791 Foundation Integration — Codable for every type (addresses code as dotted-decimal text, fields as their raw numbers).

Installation

dependencies: [
    .package(url: "https://github.com/swift-ietf/swift-rfc-791.git", branch: "main")
]

.target(
    name: "YourTarget",
    dependencies: [
        .product(name: "RFC 791", package: "swift-rfc-791")
    ]
)

Quick Start

import RFC_791

let address = try RFC_791.IPv4.Address("192.168.1.1")
address.octets        // (192, 168, 1, 1)
address.class         // .c
address.description   // "192.168.1.1"

let ttl = RFC_791.TTL.default64
let proto = RFC_791.`Protocol`.tcp
let flags = RFC_791.Flags(dontFragment: true, moreFragments: false)

Usage

IPv4 addresses

let fromText = try RFC_791.IPv4.Address("10.0.0.1")
let fromRawValue = RFC_791.IPv4.Address(rawValue: 0xC0A8_0001)
let fromOctets = RFC_791.IPv4.Address(Byte(bitPattern: 127), Byte(bitPattern: 0), Byte(bitPattern: 0), Byte(bitPattern: 1))

fromText.class          // .a
fromText.is.multicast   // false
fromText.is.reserved    // false

RFC_791.IPv4.Address.any        // 0.0.0.0
RFC_791.IPv4.Address.broadcast  // 255.255.255.255
RFC_791.IPv4.Address.loopback   // 127.0.0.1

IP header fields

RFC_791.Version.v4.isIPv4                    // true

let ihl = RFC_791.IHL.minimum
ihl.byteLength                               // 20
ihl.hasOptions                               // false

let ttl = RFC_791.TTL(rawValue: 64)
ttl.isExpired                                // false
ttl.decremented?.rawValue                    // 63

RFC_791.`Protocol`.icmp.rawValue             // 1
RFC_791.`Protocol`.tcp.rawValue              // 6
RFC_791.`Protocol`.udp.rawValue              // 17

RFC_791.Identification(rawValue: 0x1234)
RFC_791.TotalLength(rawValue: 1500)?.maximumDataLength  // 1480

Type of Service

let tos = RFC_791.TypeOfService(
    precedence: .immediate,
    lowDelay: true,
    highThroughput: false,
    highReliability: true
)

tos.precedence          // .immediate
tos.lowDelay            // true

RFC_791.Precedence.routine.rawValue          // 0
RFC_791.Precedence.networkControl.rawValue   // 7

Fragmentation

let flags = RFC_791.Flags(dontFragment: false, moreFragments: true)
flags.moreFragments     // true

let offset = RFC_791.FragmentOffset(rawValue: 185)!
offset.byteOffset       // 1480
offset.isFirstFragment  // false

RFC_791.FragmentOffset.fromByteOffset(0)!.isFirstFragment  // true

Header checksum

let header: [Byte] = [
    0x45, 0x00, 0x00, 0x73, 0x00, 0x00, 0x40, 0x00,
    0x40, 0x11, 0x00, 0x00,
    0xC0, 0xA8, 0x00, 0x01, 0xC0, 0xA8, 0x00, 0xC7,
].map(Byte.init(bitPattern:))

RFC_791.HeaderChecksum.compute(over: header).rawValue  // 0xB861

let complete: [Byte] = [
    0x45, 0x00, 0x00, 0x73, 0x00, 0x00, 0x40, 0x00,
    0x40, 0x11, 0xB8, 0x61,
    0xC0, 0xA8, 0x00, 0x01, 0xC0, 0xA8, 0x00, 0xC7,
].map(Byte.init(bitPattern:))

RFC_791.HeaderChecksum.verify(header: complete)  // true

Header format

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version|  IHL  |Type of Service|          Total Length         |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|         Identification        |Flags|      Fragment Offset    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Time to Live |    Protocol   |         Header Checksum       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                       Source Address                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                    Destination Address                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| Field | Bits | Type | |-------|------|------| | Version | 4 | RFC_791.Version | | IHL | 4 | RFC_791.IHL | | Type of Service | 8 | RFC_791.TypeOfService | | Total Length | 16 | RFC_791.TotalLength | | Identification | 16 | RFC_791.Identification | | Flags | 3 | RFC_791.Flags | | Fragment Offset | 13 | RFC_791.FragmentOffset | | Time to Live | 8 | RFC_791.TTL | | Protocol | 8 | RFC_791.Protocol | | Header Checksum | 16 | RFC_791.HeaderChecksum | | Source Address | 32 | RFC_791.IPv4.Address | | Destination Address | 32 | RFC_791.IPv4.Address |

License

This package is licensed under the Apache License 2.0. See LICENSE.md for details.

Package Metadata

Repository: swift-ietf/swift-rfc-791

Default branch: main

README: README.md