135 lines
4.5 KiB
Markdown
135 lines
4.5 KiB
Markdown
# DoH Forwarder — Project Plan
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## Overview
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A lightweight DNS-over-HTTPS (DoH) forwarder that accepts DNS queries over HTTPS (RFC 8484) and forwards them to upstream DoH resolvers, with caching, logging, and optional blocking.
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## Goals
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- Accept DoH queries (GET and POST per RFC 8484)
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- Forward to configurable upstream DoH resolvers (Cloudflare, Google, Quad9, custom)
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- In-memory DNS response cache with configurable TTL
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- Query logging (stdout/file)
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- Optional domain blocklist (ad-blocking / parental control)
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- Health-check endpoint
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- Low resource footprint, single binary
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## Architecture
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```
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┌─────────────┐ ┌──────────────────┐ ┌─────────────────┐
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│ DNS Client │─────▶│ DoH Forwarder │─────▶│ Upstream DoH │
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│ (browser, │ HTTPS│ (this project) │ HTTPS│ (1.1.1.1, │
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│ OS, app) │◀─────│ │◀─────│ 8.8.8.8, …) │
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└─────────────┘ └──────────────────┘ └─────────────────┘
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│ ▲
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│ UDP/TCP :53 │
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└─────────────────────┘
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System DNS (resolv.conf)
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```
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## Tech Stack
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- **Language**: Rust
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- **HTTP server**: Axum
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- **DNS wire-format**: hickory-proto (formerly trust-dns-proto)
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- **Async runtime**: Tokio
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- **Config**: TOML (config file) + env vars
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- **Logging**: tracing + tracing-subscriber
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## Milestones
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### M1 — Core Forwarding
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- [x] Project scaffold (Cargo workspace, CI)
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- [x] HTTP server with `/dns-query` endpoint (GET + POST)
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- [x] Parse incoming DNS wire-format queries
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- [x] Forward to a single upstream DoH resolver
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- [x] Return DNS wire-format response
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- [x] Basic integration test
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### M2 — Multiple Upstreams & Config
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- [x] TOML config file support
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- [x] Multiple upstream resolver support
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- [x] Upstream selection strategy (round-robin / failover)
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- [x] Environment variable overrides
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- [x] Graceful shutdown
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### M3 — Local DNS Listener
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- [ ] UDP listener on configurable port (default 53)
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- [ ] TCP listener on configurable port (default 53)
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- [ ] Receive standard DNS wire-format queries
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- [ ] Forward through DoH pipeline (shared upstream client)
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- [ ] Return DNS wire-format response over UDP/TCP
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- [ ] Config: `[dns]` section with `listen` address
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- [ ] Integration test with UDP/TCP clients
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### M4 — Caching
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- [ ] In-memory DNS response cache
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- [ ] Cache key = (query name, query type)
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- [ ] Respect DNS response TTL (with configurable max)
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- [ ] Cache eviction (TTL-based + LRU size cap)
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- [ ] Cache stats endpoint (`/cache/stats`)
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### M5 — Observability
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- [ ] Structured logging (tracing)
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- [ ] Request logging middleware (query name, type, latency, upstream used)
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- [ ] Health endpoint (`/health`)
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- [ ] Metrics endpoint (optional, Prometheus format)
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### M6 — Blocking & Filtering
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- [ ] Domain blocklist (file-based, one domain per line)
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- [ ] Wildcard / suffix matching
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- [ ] Return NXDOMAIN for blocked queries
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- [ ] Hot-reload blocklist on SIGHUP
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### M7 — Production Hardening
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- [ ] Rate limiting (per-IP)
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- [ ] Request timeout for upstream queries
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- [ ] Dockerfile (multi-stage, distroless)
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- [ ] Helm chart
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- [ ] CI pipeline (lint, test, build, image push)
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## Directory Structure (target)
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```
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doh-forwarder/
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├── Cargo.toml
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├── src/
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│ ├── main.rs # entrypoint, server setup
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│ ├── lib.rs # public API re-exports
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│ ├── config.rs # config parsing
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│ ├── dns/
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│ │ ├── mod.rs
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│ │ ├── query.rs # parse incoming DNS queries
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│ │ ├── response.rs # build/parse DNS responses
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│ │ └── listener.rs # UDP/TCP DNS listener
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│ ├── upstream/
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│ │ ├── mod.rs
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│ │ └── doh_client.rs # DoH forwarding client
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│ ├── cache.rs # DNS cache
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│ ├── blocklist.rs # domain blocking
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│ ├── routes.rs # HTTP route handlers
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│ └── middleware.rs # logging, rate-limit
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├── config/
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│ └── default.toml
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├── docs/
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│ └── plan.md
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├── DEVELOP.md
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└── tests/
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└── integration.rs
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```
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## Non-Goals (for now)
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- DNS-over-TLS (DoT) listener
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- DNSSEC validation
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- Persistent cache (Redis / disk)
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- Web UI / dashboard
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