dns_resolver

A recursive DNS resolver written in Python using raw UDP sockets. Resolves domains by walking the full delegation chain , Root servers → TLD nameservers → Authoritative nameservers.

How it works

Every query triggers a full recursive resolution from scratch:

1. A random root server is selected from the 13 IANA root server IPs
2. The TLD nameserver (e.g. .com) is extracted from the root response
3. The authoritative nameserver for the domain is resolved from the TLD response
4. The final query is sent to the authoritative nameserver and the answer is relayed back to the client

DNS packets are parsed manually using struct.unpack directly on the raw byte stream. The question section, authority records, and additional records are all walked by hand to extract nameserver IPs and glue records.

Getting started

Requires Python 3.x. No external dependencies.

git clone https://github.com/so1icitx/dns-resolver.git
cd dns-resolver

The server binds to port 53 and may require root privileges:

sudo python3 main.py

Test with nslookup:

nslookup google.com 127.0.0.1

Known limitations

• Glue record handling is fragile , if a nameserver's IP isn't in the additional section of the response, resolution fails
• UDP only; no TCP fallback for responses over 512 bytes
• No caching , every query walks the full chain from root servers
• No support for reverse lookups (arpa queries are silently dropped)
• Single-threaded; one query at a time