0001. Rust, with hickory-proto and our own server loop

• Status: Accepted
• Date: 2026-10-15

Context

dns-rs replaces Pi-hole, whose core is a fork of dnsmasq written in C, surrounded by Bash scripts. That stack is hard to evolve, to test and to secure. The replacement must be memory-safe, fast enough to answer from cache in microseconds, and easy to ship as a small static binary.

Decision

• Write dns-rs in Rust on the tokio runtime, with unsafe code forbidden.
• Use hickory-proto only to parse and serialize DNS messages, and write our own UDP/TCP server loop, request handler and upstream client, so the pipeline (validation, blocking, cache, forwarding, logging) stays fully under our control and testable.

Consequences

• Protocol details are our responsibility and are covered by tests that cite the RFCs: truncation (RFC 1035), EDNS (RFC 6891), TCP framing and pipelining (RFC 7766), negative caching (RFC 2308).
• The upstream client checks message IDs and questions itself, to resist spoofed responses.
• Encrypted upstreams (DoH, DoT) can come later from hickory-resolver or our own client, behind the same Upstream trait.