Simple DNS Server for Ads Blocker

Nowadays, people have to cope with annoying advertisements, trackers, and telemetry services while browsing the internet. This project is a simple DNS server written in Go that can block unwanted domains before they are resolved by the operating system.

The primary goal of this project is educational: to learn how the DNS protocol works at a low level, how DNS packets are structured, and how a DNS server communicates over UDP.

Features

• Parse DNS queries manually
• Resolve and forward DNS requests to upstream DNS servers
• Block domains using a configurable blocklist
• Support wildcard-like blocking through domain suffix matching
• Return custom DNS responses for blocked domains
• Lightweight and dependency-free

Technologies

This project is built entirely with Go's standard library:

• net — UDP networking and DNS forwarding
• sync — buffer pooling and concurrency primitives
• bufio — efficient blocklist file reading
• os — file handling
• strings — domain parsing and matching
• fmt — logging and debugging

Project Structure

cmd/
├── config/blocklists
└── server/


internal/
├── blocker/
├── dns/
├── pool/
└── server/

Learning Objectives

This project explores:

• DNS packet structure
• DNS header fields
• Question and Answer sections
• Domain name encoding (QName)
• UDP communication
• DNS forwarding
• Concurrent request handling with goroutines

How To Run

go build cmd/server/main.go
./main # or ./main.exe if on windows

./main --help # for more options

P/S: Still not be able to really ads block :<