Go-DNS-Server: Recursive & Authoritative DNS Resolver

A high-performance, recursive, and authoritative DNS server built from scratch in Go. This project implements the full resolution chain: Root → TLD → Authoritative → Final Answer.

Unlike typical DNS forwarders, this server does not depend on Google (8.8.8.8) or Cloudflare (1.1.1.1)—it performs true iterative resolution.

Source

---

Features

1. True Recursive Iterative Resolution

Instead of forwarding queries, the resolver starts at the Root Servers and walks the hierarchy. The resolver sets RecursionDesired = false so upstream servers treat it as a peer resolver.

2. Glue Record & Sub-Resolution Handling

When a DNS server refers to another nameserver without providing its IP, this resolver pauses the main query, resolves the nameserver hostname, and continues the original resolution.

3. High-Performance DNS Cache

• Implemented using sync.Map
• Thread-safe and TTL-aware
• Returns cached answers in ~0ms, preventing repeated upstream queries.

4. Authoritative Overrides (Local DNS)

Override any domain using config.json for local development, network-wide ad-blocking, or internal service routing.

5. Hot-Safe Concurrency

The server handles thousands of concurrent requests using goroutines. Thread safety is guaranteed using sync.RWMutex for config and sync.Map for caching.

Interactive System Flow

Trace Request Reset

---

Architecture

graph TD
    A[Client] -->|DNS Query| B[DNS Handler]
    B --> C{Cache Hit?}
    C -- Yes --> D[Return Cached Answer]
    C -- No --> E{Local Override?}
    E -- Yes --> F[Return Local Record]
    E -- No --> G[Recursive Navigator]

    G --> H[Root Servers]
    H --> I[TLD Servers]
    I --> J[Authoritative Servers]
    J --> K[Final Answer]

    K --> L[Update Cache]
    L --> M[Return to Client]

---

How Resolution Works

1. Query Arrives: The server receives a UDP packet.
2. Check Cache/Local: Fast-path for known or overridden records.
3. Start at Root: Begins at A.ROOT-SERVERS.NET (198.41.0.4).
4. Follow Referrals: Iteratively queries TLDs and Authoritative servers.
5. Handle Glue: Resolves missing nameserver IPs on-the-fly.
6. Store & Return: Caches the final resource record and responds to the client.

---

Project Structure

cmd/
 └── server/
      └── main.go        # UDP listener, socket handling

internal/
 └── dns/
      ├── handler.go    # Query flow: Cache → Local → Resolve
      ├── resolver.go   # Iterative recursive engine
      ├── cache.go      # TTL-aware concurrent cache

config.json             # Local DNS overrides

---

Built With

• Go (Golang)
• golang.org/x/net/dns/dnsmessage (DNS packet parsing)
• sync package (Thread-safe caching and concurrency)

Comments