mc/mcns

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Kyle Isom a545fec658 Add ARCHITECTURE.md for custom Go DNS server replacing CoreDNS

Design MCNS as a purpose-built authoritative DNS server with SQLite-backed
zone/record storage and a gRPC+REST management API. Supports A, AAAA, and
CNAME records with upstream forwarding for non-authoritative queries.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

2026-03-26 18:24:07 -07:00

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CLAUDE.md

Overview

MCNS (Metacircular Networking Service) is an authoritative DNS server for the Metacircular platform. It serves DNS zones from SQLite, forwards non-authoritative queries to upstream resolvers, and exposes a gRPC/REST management API authenticated through MCIAS.

Build Commands

make all         # vet → lint → test → build
make build       # go build ./...
make test        # go test ./...
make vet         # go vet ./...
make lint        # golangci-lint run ./...
make proto       # regenerate gRPC code from .proto files
make proto-lint  # buf lint + buf breaking
make mcns        # build mcns binary with version injection
make docker      # build container image
make clean       # remove binaries
make devserver   # build and run against srv/ config

Run a single test: go test ./internal/dns/ -run TestHandlerA

Architecture

Three listeners on one binary:

DNS server (:53, UDP+TCP) — serves authoritative zones from SQLite, forwards everything else to upstream resolvers. No authentication.
REST API (:8443) — management API for zones and records. MCIAS auth.
gRPC API (:9443) — same management operations. MCIAS auth.

Records stored in SQLite. Changes visible to DNS immediately on commit.

Project Structure

cmd/mcns/            CLI entry point (server, snapshot, status)
internal/
  config/            TOML config with DNS-specific sections
  db/                SQLite schema, migrations, zone/record queries
  dns/               DNS server, handler, forwarder, cache
  server/            REST API routes and handlers
  grpcserver/        gRPC server, interceptors, service handlers
proto/mcns/v1/       Protobuf definitions
gen/mcns/v1/         Generated Go code (do not edit)
deploy/              Docker, systemd, install scripts, examples

Ignored Directories

srv/ — local dev runtime data
gen/ — regenerated from proto, not hand-edited

Critical Rules

REST/gRPC sync: Every REST endpoint must have a corresponding gRPC RPC, updated in the same change.
gRPC interceptor maps: New RPCs must be added to the correct interceptor map (Public, AuthRequired, AdminRequired). Forgetting this is a security defect.
CNAME exclusivity: A name cannot have both CNAME and A/AAAA records. Enforced in the database layer within a transaction.
SOA serial: Auto-incremented on every record mutation. Never manually set or decremented.
DNS has no auth: Port 53 serves records to any client. All mutations go through the authenticated management API.

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