网卡驱动程序之编写虚拟网卡(二)

一、virt_net.c

/*

 * 参考 drivers\net\cs89x0.c

 */



#include <linux/module.h>

#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/slab.h>

#include <linux/spinlock.h>

#include <linux/string.h>

#include <linux/init.h>

#include <linux/bitops.h>

#include <linux/delay.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)

{

    /* 参考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;

        

    // 从硬件读出/保存数据

    /* 对调"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);



    /* 对调"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;

    

    //((u8 *)saddr)[2] ^= 1; /* change the third octet (class C) */

    //((u8 *)daddr)[2] ^= 1;

    type = skb->data + sizeof(struct ethhdr) + sizeof(struct iphdr);

    //printk("tx package type = %02x\n", *type);

    // 修改类型, 原来0x8表示ping

    *type = 0; /* 0表示reply */

    

    ih->check = 0;           /* and rebuild the checksum (ip needs it) */

    ih->check = ip_fast_csum((unsigned char *)ih,ih->ihl);

    

    // 构造一个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);



    /* Write metadata, and then pass to the receive level */

    rx_skb->dev = dev;

    rx_skb->protocol = eth_type_trans(rx_skb, dev);

    rx_skb->ip_summed = CHECKSUM_UNNECESSARY; /* don't check it */

    dev->stats.rx_packets++;

    dev->stats.rx_bytes += skb->len;



    // 提交sk_buff

    netif_rx(rx_skb);

}



static int virt_net_send_packet(struct sk_buff *skb, struct net_device *dev)

{

    static int cnt = 0;

    printk("virt_net_send_packet cnt = %d\n", ++cnt);



    /* 对于真实的网卡, 把skb里的数据通过网卡发送出去 */

    netif_stop_queue(dev); /* 停止该网卡的队列 */

    /* ...... */           /* 把skb的数据写入网卡 */



    /* 构造一个假的sk_buff,上报 */

    emulator_rx_packet(skb, dev);



    dev_kfree_skb (skb);   /* 释放skb */

    netif_wake_queue(dev); /* 数据全部发送出去后,唤醒网卡的队列 */



    /* 更新统计信息 */

    dev->stats.tx_packets++;

    dev->stats.tx_bytes += skb->len;

    

    return 0;

}





static int virt_net_init(void)

{

    /* 1. 分配一个net_device结构体 */

    vnet_dev = alloc_netdev(0, "vnet%d", ether_setup);;  /* alloc_etherdev */



    /* 2. 设置 */

    vnet_dev->hard_start_xmit = virt_net_send_packet;



    /* 设置MAC地址 */

    vnet_dev->dev_addr[0] = 0x08;

    vnet_dev->dev_addr[1] = 0x89;

    vnet_dev->dev_addr[2] = 0x89;

    vnet_dev->dev_addr[3] = 0x89;

    vnet_dev->dev_addr[4] = 0x89;

    vnet_dev->dev_addr[5] = 0x11;



    /* 设置下面两项才能ping通 */

    vnet_dev->flags           |= IFF_NOARP;

    vnet_dev->features        |= NETIF_F_NO_CSUM;    



    /* 3. 注册 */

    //register_netdevice(vnet_dev);

    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("[email protected],[email protected]");

MODULE_LICENSE("GPL");

二、Makefile

KERN_DIR = /work/system/linux-2.6.22.6



all:

    make -C $(KERN_DIR) M=`pwd` modules 



clean:

    make -C $(KERN_DIR) M=`pwd` modules clean

    rm -rf modules.order



obj-m    += virt_net.o

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