How we prevent conflicts in authoritative DNS configuration using formal verification

What this post added

This post details the Topaz system, a formal verification framework for Cloudflare's authoritative DNS addressing behavior. It introduces a Lisp-like DSL for encoding DNS business objectives as programs, which are then formally verified using a model checker written in Racket + Rosette. The post explains the components of a Topaz program (config, match, response) and provides examples of how these programs are used to determine IP addresses for proxied domains, including scenarios for attack mitigation, feature testing, and renumbering. It highlights the system's production use and its role in ensuring correctness and preventing conflicts in DNS configuration.