mod_extract_forwarded mod_extract_forwarded hooks itself into Apache's header parsing phase and looks for the X-Forwarded-For header which some (most?) proxies add to the proxied HTTP requests. It extracts the IP from the X-Forwarded-For and modifies the connection data so to the rest of Apache the request looks like it came from that IP rather than the proxy IP.
internet - reverse proxy - web app なんて構成のときに内側までリモートIPを届かせるためのapacheモジュール。 X-Forwarded-For を ROMOTE_ADDR にすげかえるぽ。 結構有名なの？？