// IfreqMTU is struct ifreq used to get or set a network device's MTU.
type IfreqMTU struct {
	Name [IFNAMSIZ]byte
	MTU  int32
}

// IoctlGetIfreqMTU performs the SIOCGIFMTU ioctl operation on fd to get the MTU
// of the network device specified by ifname.
func IoctlGetIfreqMTU(fd int, ifname string) (*IfreqMTU, error) {
	var ifreq IfreqMTU
	copy(ifreq.Name[:], ifname)
	err := ioctlPtr(fd, SIOCGIFMTU, unsafe.Pointer(&ifreq))