Recursive DNS Resolver (WIP, C)

A low-level DNS resolver being built from scratch in C, focusing on manual packet construction, parsing, and protocol-level understanding of networking.

Current Status

This project is in early development.

At the moment, it focuses on:

• Raw packet structure definitions (Ethernet, IP, UDP, DNS)
• Manual parsing of IP headers
• DNS query packet construction
• Endianness handling and byte-level manipulation

This is not yet a fully functional recursive resolver.

What This Project Aims To Become

A fully working recursive DNS resolver that:

• Sends DNS queries directly to root servers
• Performs iterative resolution (root → TLD → authoritative)
• Parses DNS responses manually
• Caches results for efficiency
• Handles multiple query types (A, AAAA, CNAME, etc.)

Current Capabilities

• Packet Structures
  • Ethernet (eth)
  • IPv4 (ip, ip_details)
  • UDP (udp)
  • DNS header + question section

All structures are manually defined using packed memory layout.

Packet Construction

• Constructs DNS query manually (e.g., google.com)
• Builds question section byte-by-byte
• Sets query type (A) and class (IN)

Endianness Handling

• Custom byte-order conversion:
  • conv16()
  • conv32()
• Runtime endianness detection

How It Works (Current Flow)

1. Define raw buffer

2. Cast buffer into protocol structures

3. Extract header fields manually

4. Construct DNS query name (google.com) in wire format:

   • 6 google 3 com 0

5. Append DNS question tail