[Zope] How to log real user and ip in Z2.log behind squid/apache?

Hi, I run zope-2.7.1 behind squid and apache. Z2.log captures the ip of squid/apache (they are on the same machine), and the user is always Anonymous. How to configure Z2.log to log the real ip of users and their login name? I tried "trusted-proxy" in zope.conf but didn't work. May be it's not related. Thanks and regards, ZhiMIn