Varnish VCL to detect and redirect file uploads

default.vcl

backend default {
  .host = "127.0.0.1";
  .port = "8080";
}
backend master {
  .host = "10.x.x.x";
  .port = "80";
}
sub vcl_recv {
  # Any uploads or restarts should go to the master backend
  if (req.restarts > 0 ||
      req.http.Content-Type ~ "multipart/form-data") {
        set req.backend = master;
  } 
}

sub vcl_fetch {
  # Restart requests which weren't found here
  if (beresp.status == 404 && req.restarts == 0) {
    return(restart);
  }
}