code: func (s *ProxyServer) CleanupAndExit() error {
  	encounteredError := userspace.CleanupLeftovers(s.IptInterface)
  	encounteredError = iptables.CleanupLeftovers(s.IptInterface) || encounteredError
  	encounteredError = ipvs.CleanupLeftovers(s.IpvsInterface, s.IptInterface, s.IpsetInterface, s.CleanupIPVS) || encounteredError
  	if encounteredError {
  		return errors.New("encountered an error while tearing down rules")
  	}
  
  	return nil
  }
docs: // CleanupAndExit remove iptables rules and exit if success return nil