code: func isLocalNetwork(ip net.IP) bool {
  	if classA.Contains(ip) {
  		return true
  	}
  	if classB.Contains(ip) {
  		return true
  	}
  	if classC.Contains(ip) {
  		return true
  	}
  	if ip.IsLinkLocalUnicast() {
  		return true
  	}
  	if ip.IsLoopback() {
  		return true
  	}
  	return false
  }
docs: // Per http://www.libtorrent.org/dht_sec.html#enforcement, the IP is
  // considered a local network address and should be exempted from node ID
  // verification.