How to write extensions for wifi router?

Question

Programming

What's up, software.
I climbed here in the router settings, and found a bunch of interesting things there that I was going to write myself.
There were a couple of points that were interesting to me, namely:
- Prohibition of users from a network with a specific poppy address from using the Internet
- Restricting access to users from this network to specific sites by URL or IP.
I have a question. I would like to write the simplest plugin or extension, even if it works independently of the router, either as a web application or as a desktop.
There should be just 2 trivial functions and 2 fields with a button, i.e.
In one field you enter the URL that you want to block for this network, and in the other the poppy address or IP of the computer that will not be able to go to this URL.
I have some knowledge in programming, and a lot of desire, but I have no idea yet how it even works.
I wrote desktop, client-server applications in Java, scripts in python and JS, and various micro-toys on the crosses, i.e., I can deal with some libraries, but I need something like a plan and an approximate implementation.
Help, friends.

Answer 1

OpenWrt already has these buttons, and if it doesn't, then they are in the repositories as additional software.
Well, cross-compilation will help you, if you want to write your bike.

Answer 2

well, it's linux. so the approach is the same.