code: func (e *Ethtool) LinkState(intf string) (uint32, error) {
  	x := ethtoolLink{
  		cmd: ETHTOOL_GLINK,
  	}
  
  	if err := e.ioctl(intf, uintptr(unsafe.Pointer(&x))); err != nil {
  		return 0, err
  	}
  
  	return x.data, nil
  }
docs: // Get state of a link.