Coding Challenge 44 - Build Your Own DNS Forwarder

This challenge is to build your own DNS Forwarder.

I’d Like You Input!

I’ve had some requests for Coding Challenges to provide automates tests for each step of the challenges and some form of leaderboard. In short to build something a bit like CodeCrafters.

Is that something you’d like to see, or should I focus on the courses? Please comment below or message me with your thoughts.

A DNS Forwarder is a nameserver used to resolve DNS queries instead of directly using the authoritative nameserver chain. Often they are used to sit on the edge of a local area network and provide DNS resolution to the computers on the network, reducing external traffic and speeding up external access by serving the answer from a local cache.

The Challenge - Building A DNS Forwarder

In this challenge we’re going build a simple DNS Forwarder that can resolve the IP address for a host either from it’s local cache, or by forwarding the request to an authoritative nameserver.

Step Zero

In this introductory step you’re going to set your development environment up ready to begin developing and testing your solution.

I’ll leave you to choose your target platform, setup your editor and programming language of choice. I’d encourage you to pick a tech stack that you’re comfortable doing network programming with - we’re going to be creating, sending and receiving UDP packets.

Step 1

In this step your goal is to create a UDP server that will listen on a specified port for incoming requests. Your server should use port 53 if no port is provided, otherwise it should use the provided port (i.e. add a command line option to specify it). Note for testing we’ll use a port above 1023 as many OSs don’t allow non-privileged users to use a port below 1023.

Once you have your server running you can test it with dig. That might look like this:

% dig @127.0.0.1 -p 1053 www.google.com
        

With the server so far running in another terminal.

% ccdns
MSG received
        

All the server does so far is listen for messages, so I’m just printing out the fact that something was received. We’ll handle it in a later step.

Continued...

You can find Step 2 and beyond on the Coding Challenges website as build your ownDNS Forwarder.

Or if you'd rather get the whole challenge delivered to you inbox every week, you can subscribe on the Coding Challenges Substack.

2 Other Ways I Can Help You:

1. I write another FREE newsletter?Developing Skills?that helps you level up the other skills you need to be a great software developer.
2. I have some courses available: Become a Better Software Developer by Building Your Own Redis Server (Python Edition) which guides you through solving the Redis Coding Challenge in Python. Build Your Own Shell (Go Edition) which guides you through solving the Shell Coding Challenge in Go.