Adding IOCTL interface to networking loopback device driver

The loopback driver was introduced to readers in this article (here). We will now add an IOCTL interface to the loopback network device driver. The netdevice operations structure net_device_ops provides a function registration for IOCTLs. In earlier versions of the Linux kernel, the OP callback in the net_device_ops structure was ndo_do_ioctl. However, this callback is [ ]