Linux驅動程序之網卡驅動(一)

Linux驅動程序之網卡驅動(一)

app： socket

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kernel： BSD協議棧

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hard_start_xmit()netif_rx()

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硬件相關的驅動程序

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硬件

編寫網卡驅動步驟：

1、分配一個net_dev結構體

2、設置：

2.1、發包函數：hard_start_xmit()

2.2、收到數據時（在中斷處理函數裏）用netif_rx上報數據

2.3、其他設置

3、註冊：register_netdev

一、網絡驅動代碼的基本框架:

/*
 * 參考 drivers\net\cs89x0.c
 */

static struct net_device *vnet_dev;

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 */

	/* 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");

二、增加發送函數：

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;

	/* 3. 註冊 */
	//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);

	/* 對於真實的網卡, 把skb裏的數據通過網卡發送出去 */

	/* 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;

	

	/* 3. 註冊 */
	//register_netdevice(vnet_dev);
	register_netdev(vnet_dev);
	
	return 0;
}

四、增加接受函數

static struct net_device *vnet_dev;

static void emulator_rx_packet(struct sk_buff *skb, struct net_device *dev)
{
	/* 參考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;
		
	// 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;
}