code: def disable_openssh_rdns(distribution):
      
      log_green('Disabling openssh reverse dns lookups')
      openssh_config_file = '/etc/ssh/sshd_config'
      dns_config = 'UseDNS no'
      if not file_contains(openssh_config_file, dns_config, use_sudo=True):
          file_append(openssh_config_file, dns_config, use_sudo=True)
          service_name = 'sshd'
          if 'ubuntu' in distribution:
              service_name = 'ssh'
          sudo('service {} reload'.format(service_name))
docs: Set 'UseDNS no' in openssh config to disable rDNS lookups
  
      On each request for a new channel openssh defaults to an
      rDNS lookup on the client IP. This can be slow, if it fails
      for instance, adding 10s of overhead to every request
      for a new channel (not connection). This can add a lot of
      time to a process that opens lots of channels (e.g. running
      several commands via fabric.)
  
      This function will disable rDNS lookups in the openssh
      config and reload ssh to adjust the running instance.
  
      :param bytes distribution: the name of the distribution
          running on the node.