inserting client ip address into header when using SNAT

This is actually something a lot of people do...

So here is an example that preserves the original client IP in a HTTP header called "ORIG_CLIENT_IP" (you could replace the name with any other name you want and/or also put it in a cookie to the server:

  
  rule preserve_client_ip {  
     when HTTP_REQUEST {  
        HTTP::header insert ORIG_CLIENT_IP [IP::remote_addr]  
     }  
  }  
  

And there you have it. If you wanted to add it as a cookie then use the instead:

HTTP::cookie insert ORIG_CLIENT_IP [IP::remote_addr]