Linux Minimal ioctl Network Device Example

chriz_ioctl_kernel.c

#include <linux/module.h>	/* Needed by all modules */
#include <linux/kernel.h>	/* Needed for KERN_INFO */
#include <linux/init.h>		/* Needed for the macros */

#include <linux/netdevice.h> 

static int chriz_open(struct net_device *dev)
{
	printk(KERN_INFO "chriz open...\n");
	netif_start_queue(dev);
	return 0;
}

static int chriz_release(struct net_device *dev)
{
	printk(KERN_INFO "chriz release...\n");
	netif_stop_queue(dev);
	return 0;
}

static int chriz_xmit(struct sk_buff *skb, struct net_device *dev)
{
	printk(KERN_INFO "chriz xmit...\n");
	dev_kfree_skb(skb);
	return 0;
}

static int chriz_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
{
	printk(KERN_INFO "chriz ioctl: command: %x\n", cmd);
	return 0;
}

// ---------------------------------------------------------------

static const struct net_device_ops chriz_netdev_ops = {
	.ndo_open = chriz_open,
	.ndo_stop = chriz_release,
	.ndo_start_xmit = chriz_xmit,
	.ndo_do_ioctl = chriz_ioctl,
};

void chriz_init(struct net_device *dev)
{

	ether_setup(dev);
	dev->netdev_ops = &chriz_netdev_ops;
	printk(KERN_INFO "chriz device initialized!\n");
}

// ---------------------------------------------------------------

struct net_device *chriz_dev = NULL;

static int __init chriz_init_module(void)
{
	printk(KERN_INFO "chriz init module...\n");
	chriz_dev = alloc_netdev(0, "chriz", NET_NAME_UNKNOWN, chriz_init);
	if (register_netdev(chriz_dev)) {
		printk("chriz: device init error\n");
		return 1;
	}
	return 0;
}

static void __exit chriz_exit_module(void)
{
	unregister_netdev(chriz_dev);
	printk(KERN_INFO "chriz exit module... Goodbye!\n");
}

module_init(chriz_init_module);
module_exit(chriz_exit_module);

chriz_ioctl_user.c

#include <net/if.h>
#include <net/if_arp.h>
#include <fcntl.h>      /* open */
#include <unistd.h>     /* exit */
#include <sys/ioctl.h>  /* ioctl */
#include <sys/socket.h>
#include <errno.h>

#include <stdio.h>
#include <string.h>
#include <linux/wireless.h> // struct iwreq


#define SIOC_CHRIZ        SIOCDEVPRIVATE+1

char interface_name[16] = "chriz";

int main() {

	int sock = 0;
	int ret = 0;

	struct iwreq iwr;
	struct ifreq ifr;
	
	printf("Start...\n");

	// init net socket
	sock = socket(AF_INET, SOCK_DGRAM, 0);
	if (sock < 0) {
		printf("socket error\n");
		return 1;
	}

	// fill in interface name
	memset(&iwr, 0, sizeof(iwr));             // for wireless
	strcpy(iwr.ifr_name, interface_name); 
	memset(&ifr, 0, sizeof(ifr));             // for ethernet
	strcpy(ifr.ifr_name, interface_name);

	// do ioctl
	ret = ioctl(sock, SIOC_CHRIZ, &ifr);
	if (ret < 0) {
		printf("ioctl error %d, err: %s\n", ret, strerror(errno));
	}

	// finished
	printf("Finished...\n");
	close(sock);
	return 0;

}

Makefile

KDIR := /home/chriz/repositories/WSL2-Linux-Kernel/

obj-m += chriz_ioctl_kernel.o

all:
	$(MAKE) -C $(KDIR) M=$(PWD) modules
	gcc -o chriz_ioctl_user chriz_ioctl_user.c

clean:
	rm -rf *.o *.ko *.mod.* *.cmd .module* modules* Module* .*.cmd .tmp*
	make -C ${KDIR} M=$(PWD) clean
	rm -f chriz_ioctl_user