The static pages of the blog here are served from a lighttpd container with an nginx proxy in front.
I was looking through the lighttpd access logs and was a bit annoyed as it showed the internal IP of the nginx proxy.

My nginx instance is already setup to forward the actual remote IP in the X-Real-IP header.
Thus I needed to make lighttpd use the forwarded IP from the header in the access logs.
This can be achieved with the extforward module using the following configuration snippet:

server.modules += ("mod_extforward")
extforward.headers = ("X-Real-IP")
extforward.forwarder = ("10.111.0.0/16" => "trust")

With this config, lighttpd uses the X-Real-IP in the access logs.
The override is only performed when the connection comes from the 10.111.0.0/16 subnet. Which prevents remote IP spoofing via injected/faked headers.
(the 10.111.0.0/16 subnet is my internal container network where nginx is running)