docs: def sr1(x, promisc=None, filter=None, iface=None, nofilter=0, *args, **kargs):
      """Send packets at layer 3 and return only the first answer"""
      s = conf.L3socket(promisc=promisc, filter=filter,
                        nofilter=nofilter, iface=iface)
      ans, _ = sndrcv(s, x, *args, **kargs)
      s.close()
      if len(ans) > 0:
          return ans[0][1]
      else:
          return None