code: func ipRunOutput(cmd string, args ...interface{}) (string, error) {
  	cmdStr := fmt.Sprintf(cmd, args...)
  	ipArgs := strings.Split(cmdStr, " ")
  	log.Infof("%s %s", ipCmd, cmdStr)
  	ip := exec.Command(ipCmd, ipArgs...)
  	out, err := ip.Output()
  	if err != nil {
  		return "", fmt.Errorf("IP run %q: %v", cmdStr, err)
  	}
  	return string(out), nil
  }
docs: // ipRunOutput runs the Linux ip(1) command with the specified arguments and
  // returns the output.