code: func getIPv4DefaultRoutes(input io.Reader) ([]Route, error) {
  	routes := []Route{}
  	scanner := bufio.NewReader(input)
  	for {
  		line, err := scanner.ReadString('\n')
  		if err == io.EOF {
  			break
  		}
  		//ignore the headers in the route info
  		if strings.HasPrefix(line, "Iface") {
  			continue
  		}
  		fields := strings.Fields(line)
  		// Interested in fields:
  		//  0 - interface name
  		//  1 - destination address
  		//  2 - gateway
  		dest, err := parseIP(fields[1], familyIPv4)
  		if err != nil {
  			return nil, err
  		}
  		gw, err := parseIP(fields[2], familyIPv4)
  		if err != nil {
  			return nil, err
  		}
  		if !dest.Equal(net.IPv4zero) {
  			continue
  		}
  		routes = append(routes, Route{
  			Interface:   fields[0],
  			Destination: dest,
  			Gateway:     gw,
  			Family:      familyIPv4,
  		})
  	}
  	return routes, nil
  }
docs: // getIPv4DefaultRoutes obtains the IPv4 routes, and filters out non-default routes.