I was wondering if there is an option to create a tcp tunnel directly to haproxy, wich can serve as a backend?
Sort of what ngrok is doing.
No, there is not.
Something ingenious with some plugin or lua scripting is not possible?
Everything is possible. I’m not aware of a specific solution.
Had to resolve it with something like this
An experimental feature is in 2.9-dev4 called “reverse HTTP”:
https://www.mail-archive.com/haproxy@formilux.org/msg43924.html
Again that is a experimental feature in a development branch of haproxy, so this is a long way from being production ready. It’s a first step.