#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/stddef.h>
#include <linux/netdevice.h>

MODULE_LICENSE("GPL");

struct net_device *dev;

static int my_eth_init(struct net_device *dev)
{
    // Initialize device
    printk(KERN_INFO "My Ethernet device initialized\n");
    netif_start_queue(dev);
    return 0;

}

static void my_eth_exit(struct net_device *dev)
{
    // Cleanup device
    pr_info(KERN_INFO "My Ethernet device exited\n");
    netif_stop_queue(dev);
}

static netdev_tx_t my_eth_start_xmit(struct sk_buff *skb, 
                             struct net_device *dev)
{
    // Start xmit
    printk(KERN_INFO "My Ethernet device start xmit\n");
    printk("len: %d\n", skb->len);
    for (int i = 0; i < skb->len; i++) {
        printk("data: %c\n", skb->data[i]);
    }
    printk("protocol: %d\n", skb->protocol);

    netif_receive_skb(skb);

    return NETDEV_TX_OK;
}

static struct net_device_ops my_netdev_ops = {
    .ndo_init = my_eth_init,
    .ndo_uninit = my_eth_exit,
    .ndo_start_xmit = my_eth_start_xmit
};

void init_testcard(struct net_device *dev) 
{
    dev->netdev_ops = &my_netdev_ops;
    printk("Init testcard\n");
}

struct net_device testcard;

int register_device(void) {
    dev = alloc_netdev(0, "myeth%d", NET_NAME_UNKNOWN, init_testcard);

    if (!dev)
        return -ENOMEM;

    printk("Registering\n");

    if (register_netdev(dev)) {
        printk("Failed :(\n");
        free_netdev(dev);
        return -ENODEV;
    }
    
    printk("Registered\n");
    
    return 0;
}

int __init custom_init(void)
{
    int err;
    if ((err = register_device())) {
        printk("Error loading postage\n");
        return err;
    }

    return 0;
}

void __exit custom_exit(void)
{
    if (!dev) {
        printk(KERN_ERR "Ethernet device not found\n");
        return;
    }

    unregister_netdev(dev);
    printk(KERN_INFO "Ethernet device unregistered\n");

    free_netdev(dev);
    printk(KERN_INFO "Ethernet device freed\n");
}

module_init(custom_init);
module_exit(custom_exit);