code: function goodbyes (name, packet) {
    return packet.answers.concat(packet.additionals)
      .filter(function (rr) {
        return rr.type === 'PTR' && rr.ttl === 0 && dnsEqual(rr.name, name)
      })
      .map(function (rr) {
        return rr.data
      })
  }
docs: PTR records with a TTL of 0 is considered a "goodbye" announcement. I.e. a DNS response broadcasted when a service shuts down in order to let the network know that the service is no longer going to be available.  For more info see: https://tools.ietf.org/html/rfc6762#section-8.4  This function returns an array of all resource records considered a goodbye record