How to create your own PROXY service?

Question

proxy

Here are 3 options, maybe they can be combined, but I explained how I could ....
Hello, I'm selling hosting services, and the question arose "Proxying sites with visible JS loading." In simple words, I want to make an analogue of CloudFlare (not advertising) with a visible JS preloader.
1) In which direction to dig if I want to arrange everything on VDS (place proxies for several sites on 1 VDS)?
2) Also, is it possible to do this in PHP with adding your own JS preloader and replacing all links? It may not protect against DDoS, but is it possible? If this option is possible, then you can help with the implementation, at least the code. If you like it, I can pay for revision. Example: I have a website and I want to make a redirect to vk.com, that is, when entering domain.ru, a person sees a preloader (mine), and then the vk.com page, while if on any page (on vk.com) will be a link to vk.com/test123, then when you click led to domain2.ru/test123 (and the content of vk.com/test123 was shown there)
3) A complete analogue of CloudFlare with full automation, I saw our analogue on Cloud-Shield (they have everything automated on WHMCS), maybe someone has a creamer.
PS I don't know how to explain, but now I've done my best.

Answer 1

The fate of Fedor Vlasov did not teach anything? Proxying VKontakte is an extremely dangerous business...

Answer 2

You misunderstand how CloudFare works.
1. And here DNS.
The original site remains on its ip. And dns will resolve the request to the site to one of the
CDN-proxy servers.
The original ip is theoretically now known only to the proxying system.
But if you knew it, then by adjusting etc/host on your computer you will be able to get
to the site directly.
2. JS preloader is one of the defense mechanisms, not the main functionality.
3. Simplified.
We now hit nginx in proxy mode with a smart firewall in front of it.
If the load grows, then the heuristics are turned on. skip request to backend or discard.
We doubt. We give a special page (according to your JS preloader), but it only has
one task is to determine that this is a live visitor, and not a bot.
Defined as a person, all now his request will be passed to the backend.