以虚拟网卡驱动为例
框架入口源文件：vir_net.c
（可根据入口源文件，再按着框架到内核走一遍）
内核版本：linux_2.6.22.6 硬件平台：JZ2440
以下是驱动框架：
以下是驱动代码 vir_net.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> //定义一个 device_net结构体 static struct net_device *s3c_vir_net; //netif_rx static int sent_up_sk_buff(struct sk_buff *skb,struct net_device *dev) //copy frome LLD3 { 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); } //hard_start_xmit static int receive_sk_buff(struct sk_buff *vir_sk_buff,struct net_device *vir_net_device) { //发包计数 static int cnt=0; printk("the number of sent pack is : %d ",++cnt); //停止队列 发送sk_buff包到网卡中 netif_stop_queue(vir_net_device); //从网卡中直接读取数据sk_buff，通过netif_rx发送给上层网络结构，（这里自己构造sk_buff包上报） sent_up_sk_buff(vir_sk_buff,vir_net_device); //清除sk_buff dev_kfree_skb(vir_sk_buff); //恢复队列 netif_wake_queue(vir_net_device); //设置统计信息 包个数.... vir_net_device->stats.tx_packets++; vir_net_device->stats.tx_bytes+=vir_sk_buff->len; return 0; } static int vir_net_init(void) { //分配一个device_net结构体 s3c_vir_net = alloc_netdev(0,"fake_net", ether_setup); //设置结构体函数 MAC地址 ping功能 s3c_vir_net->hard_start_xmit = receive_sk_buff; s3c_vir_net->dev_addr[0] =0x08; s3c_vir_net->dev_addr[1] =0x89; s3c_vir_net->dev_addr[2] =0x89; s3c_vir_net->dev_addr[3] =0x89; s3c_vir_net->dev_addr[4] =0x89; s3c_vir_net->dev_addr[5] =0x11; s3c_vir_net->flags |= IFF_NOARP; s3c_vir_net->features |= NETIF_F_NO_CSUM; //注册结构体 register_netdev(s3c_vir_net); return 0; } static void vir_net_exit(void) { unregister_netdev(s3c_vir_net); free_netdev(s3c_vir_net); } module_init(vir_net_init); module_exit(vir_net_exit); MODULE_LICENSE("GPL");
以下是编译驱动的Makefile：
KER_DIR=/work/systems/kernel/linux-2/linux-2.6.22.6 all: make -C $(KER_DIR) M=`pwd` modules clean: make -C $(KER_DIR) M=`pwd` modules clean rm -fr modules.order obj-m += vir_net.o