How to remove the last IP from X-Forwarded-For

Hello,

Given the XFF in general list format, I would do so:

Incoming: X-Forwarded-For: 10.10.10.10, 10.10.10.20, 10.10.10.30
Outgoing: X-Forwarded-For: 10.10.10.10, 10.10.10.20

Sintax:

when HTTP_REQUEST {
    if { [HTTP::header exists X-Forwarded-For] && [HTTP::header X-Forwarded-For] contains "," } {
        set xff [HTTP::header X-Forwarded-For]
        HTTP::header replace X-Forwarded-For [string range $xff 0 [expr {[string last , $xff]-1}]]
    }
}

Regards.