Varnish 4.x to force HTTPS

ForceHTTPSVarnish4.vcl

sub vcl_recv {
  if (req.http.X-Forwarded-Proto !~ "https") {
    return (synth(850, "Moved Permanently"));
  }
}

sub vcl_synth {
  if(resp.status == 850) {
    set resp.http.Location = "https://" + req.http.host + req.url;
    set resp.status = 301;
    return(deliver);
  }
}

sub vcl_hash {
  hash_data(req.http.X-Forwarded-Proto);
}