F5 config - X-Forward-Proto (XFP)

f5_xfp.txt

Recommended solution would be: 
-	Use Insert header, in the custom HTTP profile that you applied to the virtual servers. 

For HTTPS Virtuals, insert: X-Forwarded-Proto, with a value of https 
For HTTP Virtuals, insert: X-Forwarded-Proto, with a value of http 

Of course you could also use apply an iRule to the Virtual Server, something like this should work: 

when HTTP_REQUEST {
    if { [SSL::mode] == 1 } {
        if {!( [HTTP::header "X-Forwarded-Proto"] eq "https") }{
            HTTP::header insert X-Forwarded-Proto "https"
        }
        if { !( [HTTP::header exists "X-Forwarded-Port"]) }{
            HTTP::header insert X-Forwarded-Port [TCP::local_port]
        }
    }
}