How to redirect all HTTP requests and add information to them?

Question

Domain Name System

Given: There are several wi-fi routers. Clients connect to them.
Required: Redirect any http request to www.example.com/{router_identifier}. Or add a header or cookies to the request with the router ID. In general, you need to make it clear to the script on example.com which router the client making the request is connected to.
I found a simple solution for redirection: raise a DNS server on the hosting, which will give the IP of my www.example.com to any DNS request, but I don’t understand how to add the required path or header to the client’s http request.

Answer 1

In my opinion, with such a redirect through DNS it is impossible to do what you want.
As I understand it, you will have to upload your firmware to routers so that they act according to this algorithm:
no GET routerID parameter?
then a redirect to: request + "?routerID=123"
A redirect in HTTP is done by returning a 302 code (for example) and adding a
location header: example.com?routerID=123