performance impact of adding XFF header

[Wolfgang]

Following XFF Header injection over source NATed HTTP/S connections (checkpoint.com) we can add XFF-header to every http request.

Any experience out there which performance impact has this feature ? I've a feeling that changing every http/https-request needs a lot.

I think to add the XFF-header to a HTTPS-request full HTTPS inspection is needed. From the requirements in sk167578 "For HTTPS traffic: Enable HTTPS inspection on the relevant connections." 

But I'm not sure if the XFF-header is part of the whole encrypted HTTP-request-header or maybe readable unencrypted ?

[PhoneBoy]

At minimum you need to activate APCL/URLF and HTTPS Inspection as all HTTP Headers are encrypted.
Not sure what the performance impact is above and beyond that.