Linux驱动程序之网卡驱动(一)

Linux驱动程序之网卡驱动(一)

app： socket

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kernel： BSD协议栈

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hard_start_xmit()netif_rx()

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硬件相关的驱动程序

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硬件

编写网卡驱动步骤：

1、分配一个net_dev结构体

2、设置：

2.1、发包函数：hard_start_xmit()

2.2、收到数据时（在中断处理函数里）用netif_rx上报数据

2.3、其他设置

3、注册：register_netdev

一、网络驱动代码的基本框架:

/*
* 参考 drivers\net\cs89x0.c
*/

static struct net_device *vnet_dev;

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 */

/* 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_LICENSE("GPL");

二、增加发送函数：

static struct net_device *vnet_dev;

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);
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;

/* 3. 注册 */
//register_netdevice(vnet_dev);
register_netdev(vnet_dev);

return 0;
}

三、
static struct net_device *vnet_dev;

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 */

/* 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;

/* 3. 注册 */
//register_netdevice(vnet_dev);
register_netdev(vnet_dev);

return 0;
}

四、增加接受函数
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;
}