I have Nginx listening on port 443 as an SSL terminator, and proxying unencrypted traffic to Varnish on the same server. Varnish 3 is handling this traffic, and traffic coming in directly on port 80. All traffic is passed, unencrypted, to Apache instances on other servers in the cluster. The Apache instances use mod_rpaf to replace the logged client IP with the contents of the X-Forwarded-For header.

My problem is that if the traffic is coming via Nginx, while the 'correct' client IP is getting logged in the VarnishNCSA logs, it looks as if Varnish is (understandably) replacing Nginx's X-Forwarded-For header with 127.0.0.1 downstream, and this is getting logged with Apache. Is there a nice simple way to stop Varnish rewriting X-Forwarded-For if it's already populated?