网卡驱动程序之编写虚拟网卡(二)

一、virt_net.c

/*
 * 参考 drivers
etcs89x0.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
", *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
", ++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("thisway.diy@163.com,17653039@qq.com");
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