The IP address using XFF only works when passing through proxy

The client (curl) does not pass the originating IP address, so when responding to requests based on IP it would be great to have access to whatever the IP address that ends up in the log is as a variable. The x_forwarded_for addition is excellent, but it's not helping when not going through a proxy, as far as I can tell?

Tested using curl 7.76.1