DNS GO — Code Overview

This project is a minimal DNS server written in Go, designed to answer only A record (IPv4 address) queries for a small set of domains. It is intentionally simple, making it easy to understand the DNS protocol and Go networking basics.

How It Works

Supported Record Types:

• Only DNS A records (IPv4) are supported. All other record types (e.g., AAAA, MX) will return no answer.

Supported Domains:

• The list of domains and their IPv4 addresses is defined in names.json. Example:
  • google.com → 3.1.3.7
  • acint.net → 192.168.0.102
  • yadavaman.duckdns.org → 100.125.140.68

Port:

• The server listens on UDP port 8282.

File Roles

• main.go: Entry point. Sets up the UDP server, handles incoming DNS requests, parses queries, and sends responses.
• dblookup.go: Loads the domain-to-IP mapping from names.json and provides lookup logic.
• models/dns.go: Contains Go structs for DNS headers, resource records, and domain models.
• names.json: The configuration file listing supported domains and their IPv4 addresses.

Request/Response Flow

1. DNS Query Sent:

• A client (e.g., using dig) sends a DNS query for an A record to UDP port 8282.

2. Server Receives Query:

• main.go reads the UDP packet, parses the DNS header and question section.

3. Domain Lookup:

• The server checks if the query is for an A record (TypeA) and if the domain exists in names.json.
• If both match, it prepares a DNS response with the mapped IPv4 address.
• If not, it returns an empty answer section.

4. Response Sent:

• The server serializes the DNS response and sends it back to the client over UDP.

Example Query and Flow

Suppose you run:

dig @127.0.0.1 -p 8282 google.com A

What happens:

• The server receives the query for google.com A record on port 8282.
• It finds google.com in names.json and responds with 3.1.3.7.
• The dig output will show this IP in the ANSWER section.

If you query for an unsupported record type or unknown domain, the ANSWER section will be empty.

Summary

• Only A records for domains in names.json are answered.
• The server is intentionally simple and easy to read.
• Great for learning about DNS and Go networking.

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MIT License. Free to use, modify, and share.

Project Structure

• main.go — Entry point, starts the DNS server
• dblookup.go — Handles DNS record lookups
• models/ — Data models (e.g., DNS record structs)
• names.json — Example DNS records or configuration
• tmp/ — Temporary files or runtime data

Why Use This Project?

• Simplicity: The codebase is small and easy to understand.
• Learning: Great for learning about DNS and Go networking.
• Customization: Easily add your own DNS logic or records.

License

MIT License. Free to use, modify, and share.