rpaf is for backend Apache servers what mod_proxy_add_forward is for frontend
Apache servers. It does excactly the opposite of mod_proxy_add_forward written
by Ask Bjørn Hansen. It will also work with mod_proxy in Apache starting with
release 1.3.25 and mod_proxy that is distributed with Apache2
from version 2.0.36.
It changes the remote address of the client visible to other Apache modules when
two conditions are satisfied. First condition is that the remote client
is actually a proxy that is defined in httpd.conf. Secondly if there is an
incoming X-Forwarded-For header and the proxy is in it's list of known proxies
it takes the last IP from the incoming X-Forwarded-For header and changes the
remote address of the client in the request structure. It also takes the
incoming X-Host header and updates the virtualhost settings accordingly.
For Apache2 mod_proxy it takes the X-Forwared-Host header and updates
# Preparation step (unpackung and patching if necessary)