Reverse proxy cockpit, but leave URL Root as / for local accces

[chriswiggins]

We are looking into deploying cockpit on many servers, where we want to access them either via a reverse proxy or locally.

I have been through commit 8e4958a to understand where the UrlRoot parameter comes from, but I'm trying to understand why this is hard-coded? Can't all the pathing etc to the cockpit endpoint just be relative?

Ideally we would like to dynamically reverse-proxy through our own middleware, whereby the server being accessed needs to have no knowledge of the URL that it is getting accessed through.

We do this in many other instances already, where an example nginx config looks something like this (note the forward slashes):

location /gateway/some-server/ {
        proxy_pass https://10.1.2.3/;
        proxy_http_version 1.1;
        proxy_buffering off;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
  }

Perhaps I'm missing something, but is there a reason Cockpit doesn't support relative paths? Happy to open a PR changing this, just need to be pointed in the right direction!

Alternatively, would there be interest in supporting a header which tells cockpit which URL it is being served from?

Thanks, Chris