Setting serverside IP address to value received in x-forwarded-for header

I am providing this iRule as an example - however I'm not 100% if it work.

Firstly, you need to be confident that return traffic will be directed to the F5 as the only option to change the client IP address is to SNAT the source IP. i.e. your back end servers need to have F5 as the default gateway.

F5 should un-NAT the address for return flows but I've never done this with an IP address that isn't in the same range as a self IP on the device.

when HTTP_REQUEST {
    if {[HTTP::header exists "X-Forwarded-For"]} {
        snat [HTTP::header value "X-Forwarded-For"]
    }
}