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DNS Server in Rust

A minimal DNS server implementation in Rust that demonstrates the fundamentals of the DNS protocol - packet parsing, recursive resolution, and UDP socket handling

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Rust Networking DNS Protocol UDP Binary Parsing

Project Overview

A minimal DNS server implementation in Rust that demonstrates the fundamentals of the DNS protocol - packet parsing, recursive resolution, and UDP socket handling

README.md
README.md

Project Overview

A from-scratch DNS server implementation in Rust that handles DNS query resolution at the protocol level. This project demystifies how DNS works by implementing packet parsing, header construction, and recursive resolution without relying on external DNS libraries.

Key Features

DNS Protocol Implementation

  • Full DNS packet parsing and construction
  • Support for A, AAAA, CNAME, and NS record types
  • DNS header flag manipulation (QR, OPCODE, RCODE)
  • Question and resource record encoding/decoding

UDP Socket Handling

  • Custom UDP server implementation
  • Request/response matching via transaction IDs
  • Timeout and retry logic for reliability

Recursive Resolution

  • Root server querying
  • Iterative resolution following referrals
  • CNAME chain following
  • Response caching for performance

Technical Implementation

Core Components

DNS Packet Structure

struct DnsHeader {
    id: u16,
    flags: u16,
    questions: u16,
    answer_rrs: u16,
    authority_rrs: u16,
    additional_rrs: u16,
}

Label Encoding

  • DNS name compression support
  • Pointer following for compressed labels
  • Proper length-prefixed encoding

Technologies Used

  • Rust: Memory-safe systems programming
  • Tokio: Async runtime for UDP handling
  • Nom (optional): Parser combinators for binary parsing

Learning Outcomes

DNS Protocol Deep Dive

  • Understood binary DNS packet format
  • Learned about the distributed nature of DNS
  • Implemented compression pointer chasing
  • Gained appreciation for protocol design decisions

Rust Skills

  • Low-level binary data manipulation
  • Bitwise operations for flag handling
  • UDP socket programming
  • Error handling in network protocols
  • Zero-copy parsing where possible

Networking Concepts

  • UDP vs TCP for DNS
  • Root server hierarchy
  • DNS caching and TTL
  • Recursion vs iteration

Why This Project Matters

Most developers use DNS daily but have no idea how it actually works under the hood. Building a DNS server from scratch:

  • Demystifies a critical internet infrastructure component
  • Demonstrates ability to implement network protocols
  • Shows comfort with low-level binary data
  • Proves Rust competency for systems programming
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