dnsguide

DNS is the system that translates human-readable website addresses into the numeric addresses computers actually use to connect to each other. Before DNS existed, a single shared text file on a Stanford server tracked every host on the internet. That file got manually copied around via FTP. As the internet grew, that approach fell apart, and in 1983 a researcher named Paul Mockapetris designed DNS as a scalable replacement. It has handled the internet's growth from thousands of computers to billions ever since.

This repository is a written guide that walks you through building your own DNS server from scratch using the Rust programming language. It is not a finished product you install and run. It is a learning resource: you read through the chapters, follow along with the code samples, and end up understanding how DNS actually works at a low level, including how packets are structured and how servers look up addresses by talking to other servers.

The guide is organized into five chapters. The first explains the DNS wire protocol, meaning how data is formatted when sent over the network. The second builds a basic resolver, which is the part that asks a DNS server for an answer. The third adds support for more record types beyond the basic address lookup. The fourth builds a minimal DNS server. The fifth adds recursive resolution, where your server can find answers itself by querying upstream servers in a chain.

Each chapter has a matching Rust source file containing all the code written up to that point. You can run each sample directly using Rust's standard build tool. The guide was originally written in 2016 and was updated in 2020 to fix a security flaw, modernize the code style, and clean up inefficiencies.

This is intended for people who want to understand network programming and DNS internals by working through a concrete, practical example. No prior knowledge of DNS is assumed.