網絡設備驅動程序
學習網絡設備驅動程序之筆記，實現一個最簡單的虛擬網卡
#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)
{
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;
//((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);
// 修改類型, 原來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);
// 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);
/* 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);
/* 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的數據寫入網卡 */
/* 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); /* 數據全部發送出去後,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;
}
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->hard_start_xmit = virt_net_send_packet;
/* 設置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;
/* 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 */
//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_LICENSE("GPL");
