Varnish: clean up 127.0.0.1 from X-Forwarded-For header in VCL

clean-x-forwarded-for.vcl

#
# Varnish appends ${localhost} (= 127.0.0.1) to the XFF header
# automatically and transparently *before* calling vcl_recv().
#
# Not a problem for the Rest backend, but in the interest of
# trying to be as transparent as possible, we have the option
# to clean it out.
#
sub clean_x_forwarded_for {
    if (req.http.X-Forwarded-For != "") {
        set req.http.X-Forwarded-For = regsub(req.http.X-Forwarded-For,
            "^(.+)\s*,\s*127\.0\.0\.1$", "\1");
    }
}