網卡驅動

完成網卡驅動程序流程：
1.分配一個net_device結構體
2.設置
2.1發包函數：hard_start_xmit
2.2收到數據時（在中斷處理函數裏）用netif_rx上報數據
2.3其他設置
3.註冊：register_netdev

linux3.0內核下虛擬網卡

#include <linux/errno.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/fcntl.h>
#include <linux/interrupt.h>
#include <linux/ioport.h>
#include <linux/in.h>
#include <linux/skbuff.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/bitops.h>
#include <linux/delay.h>
#include <linux/gfp.h>
#include<linux/ip.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/irq.h>
static struct net_device *vnet_dev;
static void emulator_rx_packet(struct sk_buff *skb,struct net_device *dev)
{
    /*參考LDD3*/
    unsigned char *type;
    struct iphdr *ih;
    __be32 *saddr,*daddr,tmp;
    unsigned char tmp_dev_addr[ETH_ALEN];
    struct ethhdr *ethhdr;
    struct sk_buff *rx_skb;

    //從硬件讀出/保存數據
    /*對調“源/目的”的mac地址*/
    ethhdr = (struct ethhdr *)skb->data;
    memcpy(tmp_dev_addr,ethhdr->h_dest,ETH_ALEN);
    memcpy(ethhdr->h_dest,ethhdr->h_source,ETH_ALEN);
    memcpy(ethhdr->h_source,tmp_dev_addr,ETH_ALEN);

    /*對調"源/目的"的IP地址*/
    ih=(struct iphdr *)(skb->data+sizeof(struct ethhdr));
    saddr = &ih->saddr;
    daddr = &ih->daddr;
    tmp = *saddr;
    *saddr = *daddr;
    *daddr = tmp;
    type=skb->data+sizeof(struct ethhdr)+sizeof(struct iphdr);
    *type = 0;
    ih->check=0;
    ih->check=ip_fast_csum((unsigned char *)ih,ih->ihl);

    //構造一個sk_buff
    rx_skb=dev_alloc_skb(skb->len+2);
    skb_reserve(rx_skb,2);/* align IP on 16B boundary */
    memcpy(skb_put(rx_skb,skb->len),skb->data,skb->len);

    rx_skb->dev=dev;
    rx_skb->protocol=eth_type_trans(rx_skb,dev);
    rx_skb->ip_summed=CHECKSUM_UNNECESSARY;
    dev->stats.rx_packets++;
    dev->stats.rx_bytes+=skb->len;
    netif_rx(rx_skb);
}
static int net_send_packet(struct sk_buff *skb,struct net_device *dev)
{
    static int cnt=0;
    printk("virt_net_send_packet cnt = %d\n",++cnt);
    /*對於真實的網卡，把skb裏的數據通過網卡發送出去*/
    netif_stop_queue(dev);/*停止該網卡的隊列*/
    //把skb的數據寫入網絡
    /*構造一個假的sk_buff,上報*/
    emulator_rx_packet(skb,dev);
    dev_kfree_skb(skb);/*釋放skb*/
    netif_wake_queue(dev);/*數據全部發送出去，喚醒網卡的隊列*/
    /*更新統計信息*/
    dev->stats.tx_packets++;
    dev->stats.tx_bytes +=skb->len;


    return 0;
}
struct net_device_ops vnet_devices_ops={
    .ndo_start_xmit=net_send_packet,
    };

static int virt_net_init(void)
{
    /* 1. 分配一個net_device結構體 */
    vnet_dev = alloc_netdev(0, "vnet%d", ether_setup);  /* alloc_etherdev */

    /* 2. 設置 */


    vnet_dev->dev_addr[0] = 0x11;

    vnet_dev->dev_addr[1] = 0x22;

    vnet_dev->dev_addr[2] = 0x33;

    vnet_dev->dev_addr[3] = 0x44;
    vnet_dev->dev_addr[4] = 0x55;
    vnet_dev->dev_addr[5] = 0x66;

    /*設置下面兩項才能ping通*/
    vnet_dev->flags |=IFF_NOARP;
    vnet_dev->features |=NETIF_F_NO_CSUM;
    /* 3. 註冊 */
    vnet_dev->netdev_ops=&vnet_devices_ops;
    register_netdev(vnet_dev);

    return 0;
}

static void virt_net_exit(void)
{
    unregister_netdev(vnet_dev);
    free_netdev(vnet_dev);
}

module_init(virt_net_init);
module_exit(virt_net_exit);

MODULE_AUTHOR("chenmiaohong");
MODULE_LICENSE("GPL");

測試1th:
1.insmod virt_net.ko
2.ifconfig vnet0 3.3.3.3
3.ping 3.3.3.4