網絡卡驅動設計---架構分析加回環網絡卡驅動設計(網絡卡驅動上)
網絡卡驅動架構分析:
1. Linux網路子系統
2. 重要資料結構
總結一下三個重要的資料結構:
2.1. net_device
2.2. net_device_ops
2.3. sk_buff
3. 網絡卡驅動架構分析
CS8900.c //早期2410使用的網絡卡晶片
3.1. 網絡卡初始化
首先找到驅動程式的入口:
早期的驅動入口並不是module_init()函式,而是init_module,所以找到這個函式
int __init init_module(void) { struct net_device *dev = alloc_etherdev(sizeof(struct net_local)); struct net_local *lp; int ret = 0; #if DEBUGGING net_debug = debug; #else debug = 0; #endif if (!dev) return -ENOMEM; dev->irq = irq; dev->base_addr = io; lp = netdev_priv(dev); #if ALLOW_DMA if (use_dma) { lp->use_dma = use_dma; lp->dma = dma; lp->dmasize = dmasize; } #endif spin_lock_init(&lp->lock); /* boy, they'd better get these right */ if (!strcmp(media, "rj45")) lp->adapter_cnf = A_CNF_MEDIA_10B_T | A_CNF_10B_T; else if (!strcmp(media, "aui")) lp->adapter_cnf = A_CNF_MEDIA_AUI | A_CNF_AUI; else if (!strcmp(media, "bnc")) lp->adapter_cnf = A_CNF_MEDIA_10B_2 | A_CNF_10B_2; else lp->adapter_cnf = A_CNF_MEDIA_10B_T | A_CNF_10B_T; if (duplex==-1) lp->auto_neg_cnf = AUTO_NEG_ENABLE; if (io == 0) { printk(KERN_ERR "cs89x0.c: Module autoprobing not allowed.\n"); printk(KERN_ERR "cs89x0.c: Append io=0xNNN\n"); ret = -EPERM; goto out; } else if (io <= 0x1ff) { ret = -ENXIO; goto out; }
第一步:分配net_device結構,
第二步:初始化net_device結構,
dev->irq = irq;//分配中斷號
dev->base_addr = io;//裝置基地址
lp = netdev_priv(dev);
第三步:
ret = cs89x0_probe1(dev, io, 1);\\這一步其實也是初始化硬體的!還有一部分是對device結構進行一些初始化
這個函式比較長就不貼程式碼了,其中一行比較重要:
dev->netdev_ops
= &net_ops; \\這個是對netdev_ops成員進行初始化
最後一步註冊網絡卡驅動!上圖中第二個紅色箭頭所指向的地方!
總結一下上圖:
3.2. 網絡卡資料的傳送
這個結合前面的經驗,找到網絡卡的函式操作集結構:
可以看到這個成員函式的名字叫做:net_send_packet
產生一箇中斷這個可以查查request_irq函式,在這個函式被呼叫的地方可以看到這樣的一行程式碼:static netdev_tx_t net_send_packet(struct sk_buff *skb,struct net_device *dev) { struct net_local *lp = netdev_priv(dev); unsigned long flags; if (net_debug > 3) { printk("%s: sent %d byte packet of type %x\n", dev->name, skb->len, (skb->data[ETH_ALEN+ETH_ALEN] << 8) | skb->data[ETH_ALEN+ETH_ALEN+1]); } /* keep the upload from being interrupted, since we ask the chip to start transmitting before the whole packet has been completely uploaded. */ spin_lock_irqsave(&lp->lock, flags); netif_stop_queue(dev);//1. 網絡卡驅動在向上層傳送資料的時候暫時停止接收上層發來的資料 /* initiate a transmit sequence */ writeword(dev->base_addr, TX_CMD_PORT, lp->send_cmd);//2. 將skb中的資料寫入暫存器 writeword(dev->base_addr, TX_LEN_PORT, skb->len); /* Test to see if the chip has allocated memory for the packet */ if ((readreg(dev, PP_BusST) & READY_FOR_TX_NOW) == 0) { /* * Gasp! It hasn't. But that shouldn't happen since * we're waiting for TxOk, so return 1 and requeue this packet. */ spin_unlock_irqrestore(&lp->lock, flags); if (net_debug) printk("cs89x0: Tx buffer not free!\n"); return NETDEV_TX_BUSY; } /* Write the contents of the packet */ writewords(dev->base_addr, TX_FRAME_PORT,skb->data,(skb->len+1) >>1); spin_unlock_irqrestore(&lp->lock, flags); dev->stats.tx_bytes += skb->len; dev_kfree_skb (skb);//3. 釋放skb結構 //傳送資料完後,網絡卡會產生一箇中斷 return NETDEV_TX_OK; }
ret = request_irq(dev->irq, net_interrupt, 0, dev->name, dev);</span>
可以看到這裡呼叫了net_initerupt函式,網絡卡傳送和接收中斷!
一個是傳送中斷,一個是接收中斷,
netif_wake_queue(dev);/* Inform upper layers. */ // 這行程式碼表示在傳送中斷處理過程中,通知上層協議,可以再次向網絡卡傳輸資料。
3.3. 網絡卡資料的接收
網絡卡資料的接收入口是在中斷中完成的,這個是從中斷函式中可以看到net_interrupt
接收中斷處理函式net_rx(dev)
/* We have a good packet(s), get it/them out of the buffers. */
static void
net_rx(struct net_device *dev)
{
struct sk_buff *skb;
int status, length;
int ioaddr = dev->base_addr;
status = readword(ioaddr, RX_FRAME_PORT);//讀取暫存器,網絡卡接收狀態
length = readword(ioaddr, RX_FRAME_PORT);//網絡卡接收位元組長度
if ((status & RX_OK) == 0) {
count_rx_errors(status, dev);
return;
}
/* Malloc up new buffer. */
skb = dev_alloc_skb(length + 2);//分配skb結構 +2位元組空間是為頭預留的
if (skb == NULL) {
#if 0 /* Again, this seems a cruel thing to do */
printk(KERN_WARNING "%s: Memory squeeze, dropping packet.\n", dev->name);
#endif
dev->stats.rx_dropped++;
return;
}
skb_reserve(skb, 2); /* longword align L3 header */
readwords(ioaddr, RX_FRAME_PORT, skb_put(skb, length), length >> 1);//將收到的資料填充入skb
if (length & 1)
skb->data[length-1] = readword(ioaddr, RX_FRAME_PORT);
if (net_debug > 3) {
printk( "%s: received %d byte packet of type %x\n",
dev->name, length,
(skb->data[ETH_ALEN+ETH_ALEN] << 8) | skb->data[ETH_ALEN+ETH_ALEN+1]);
}
skb->protocol=eth_type_trans(skb,dev);
netif_rx(skb);//將skb提交到協議棧
dev->stats.rx_packets++;
dev->stats.rx_bytes += length;
}
迴環網絡卡驅動設計:
使用ifocnfig,可以看到除了eth0還有一個l0, eth0代表的是一個物理網絡卡,l0代表的就是迴環網絡卡,從上面的列印資訊可以看到l0的IP地址是127.0.0.1,可以看到當ping 127.0.0.x的時候能ping通,其實l0就是網絡卡的tx和rx在軟體層的短接!所以才叫做迴環網絡卡!
其實核心程式碼中也可以找到迴環網絡卡的驅動!Lookback.c
這個檔案中的程式碼部分其實不是核心模組,而是由其它部分的呼叫的!
刪掉核心程式碼中的原有的loopback.c,結合上面的的分析和原有原始碼的分析重寫編寫loopback.c,
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <linux/if_ether.h> /* For the statistics structure. */
unsigned long bytes = 0;
unsigned long packets = 0;//skb包
static int loopback_xmit(struct sk_buff *skb, struct net_device *dev)//資料傳送
{
skb->protocol = eth_type_trans(skb,dev);//表明skb包的協議 乙太網協議
bytes += skb->len;//傳送的資料量
packets++; //傳送的資料包也要加一
netif_rx(skb);//將skb向回送, 迴環網絡卡驅動就是這實現的,這是很關鍵的一步
return 0;
}
static struct net_device_stats *loopback_get_stats(struct net_device *dev)//獲取網絡卡狀態
{
struct net_device_stats *stats = &dev->stats;//首先把state這個成員取出來
stats->rx_packets = packets;//表示網絡卡收到了多少個包
stats->tx_packets = packets;//表示網絡卡傳送了多少個包
stats->rx_bytes = bytes;//表示網絡卡接收到了多少個位元組
stats->tx_bytes = bytes;
return stats;//返回狀態
}
static const struct net_device_ops loopback_ops = {//定義一個net_device_ops 結構
.ndo_start_xmit= loopback_xmit,//傳送指標
.ndo_get_stats = loopback_get_stats,//獲取網絡卡狀態的函式
};
static void loopback_setup(struct net_device *dev)//初始化設定操作
{
dev->mtu = (16 * 1024) + 20 + 20 + 12;//網絡卡最大接收包的尺寸:16K + TCP頭 + IP頭 + 乙太網頭
dev->flags = IFF_LOOPBACK;//迴環網絡卡專有標誌 這是一個巨集核心程式碼可查
dev->header_ops = ð_header_ops;//這個是網路包的函式操作集,核心可以看這個成員的資料結構
dev->netdev_ops = &loopback_ops;//網絡卡所支援操作的集合
}
static __net_init int loopback_net_init(struct net *net)
{
struct net_device *dev;
int err;
err = -ENOMEM;
dev = alloc_netdev(0, "lo", loopback_setup);//分配一個net_device結構,loopback為一個初始化函式
if (!dev)
goto out;
err = register_netdev(dev);//註冊網絡卡驅動程式
if (err)
goto out_free_netdev;
net->loopback_dev = dev;
return 0;
out_free_netdev:
free_netdev(dev);
out:
if (net == &init_net)
panic("loopback: Failed to register netdevice: %d\n", err);
return err;
}
static __net_exit void loopback_net_exit(struct net *net)
{
struct net_device *dev = net->loopback_dev;
unregister_netdev(dev);//登出網絡卡驅動程式
}
/* Registered in net/core/dev.c */
struct pernet_operations __net_initdata loopback_net_ops = {
.init = loopback_net_init,
.exit = loopback_net_exit,
};
</span>
儲存,然後重新編譯核心,下載到開發板看執行效果!
上面的迴環網絡卡驅動有點問題,ping不同!
這是能ping通的核心自帶的原始碼:
#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/fs.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/socket.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/in.h>
#include <linux/init.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <linux/ethtool.h>
#include <net/sock.h>
#include <net/checksum.h>
#include <linux/if_ether.h> /* For the statistics structure. */
#include <linux/if_arp.h> /* For ARPHRD_ETHER */
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/percpu.h>
#include <net/net_namespace.h>
#include <linux/u64_stats_sync.h>
struct pcpu_lstats {
u64 packets;
u64 bytes;
struct u64_stats_sync syncp;
};
/*
* The higher levels take care of making this non-reentrant (it's
* called with bh's disabled).
*/
static netdev_tx_t loopback_xmit(struct sk_buff *skb,
struct net_device *dev)
{
struct pcpu_lstats *lb_stats;
int len;
skb_orphan(skb);
skb->protocol = eth_type_trans(skb, dev);
/* it's OK to use per_cpu_ptr() because BHs are off */
lb_stats = this_cpu_ptr(dev->lstats);
len = skb->len;
if (likely(netif_rx(skb) == NET_RX_SUCCESS)) {
u64_stats_update_begin(&lb_stats->syncp);
lb_stats->bytes += len;
lb_stats->packets++;
u64_stats_update_end(&lb_stats->syncp);
}
return NETDEV_TX_OK;
}
static struct rtnl_link_stats64 *loopback_get_stats64(struct net_device *dev,
struct rtnl_link_stats64 *stats)
{
u64 bytes = 0;
u64 packets = 0;
int i;
for_each_possible_cpu(i) {
const struct pcpu_lstats *lb_stats;
u64 tbytes, tpackets;
unsigned int start;
lb_stats = per_cpu_ptr(dev->lstats, i);
do {
start = u64_stats_fetch_begin(&lb_stats->syncp);
tbytes = lb_stats->bytes;
tpackets = lb_stats->packets;
} while (u64_stats_fetch_retry(&lb_stats->syncp, start));
bytes += tbytes;
packets += tpackets;
}
stats->rx_packets = packets;
stats->tx_packets = packets;
stats->rx_bytes = bytes;
stats->tx_bytes = bytes;
return stats;
}
static u32 always_on(struct net_device *dev)
{
return 1;
}
static const struct ethtool_ops loopback_ethtool_ops = {
.get_link = always_on,
};
static int loopback_dev_init(struct net_device *dev)
{
dev->lstats = alloc_percpu(struct pcpu_lstats);
if (!dev->lstats)
return -ENOMEM;
return 0;
}
static void loopback_dev_free(struct net_device *dev)
{
free_percpu(dev->lstats);
free_netdev(dev);
}
static const struct net_device_ops loopback_ops = {
.ndo_init = loopback_dev_init,
.ndo_start_xmit= loopback_xmit,
.ndo_get_stats64 = loopback_get_stats64,
};
/*
* The loopback device is special. There is only one instance
* per network namespace.
*/
static void loopback_setup(struct net_device *dev)
{
dev->mtu = (16 * 1024) + 20 + 20 + 12;
dev->hard_header_len = ETH_HLEN; /* 14 */
dev->addr_len = ETH_ALEN; /* 6 */
dev->tx_queue_len = 0;
dev->type = ARPHRD_LOOPBACK; /* 0x0001*/
dev->flags = IFF_LOOPBACK;
dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
dev->hw_features = NETIF_F_ALL_TSO | NETIF_F_UFO;
dev->features = NETIF_F_SG | NETIF_F_FRAGLIST
| NETIF_F_ALL_TSO
| NETIF_F_UFO
| NETIF_F_NO_CSUM
| NETIF_F_RXCSUM
| NETIF_F_HIGHDMA
| NETIF_F_LLTX
| NETIF_F_NETNS_LOCAL
| NETIF_F_VLAN_CHALLENGED
| NETIF_F_LOOPBACK;
dev->ethtool_ops = &loopback_ethtool_ops;
dev->header_ops = ð_header_ops;
dev->netdev_ops = &loopback_ops;
dev->destructor = loopback_dev_free;
}
/* Setup and register the loopback device. */
static __net_init int loopback_net_init(struct net *net)
{
struct net_device *dev;
int err;
err = -ENOMEM;
dev = alloc_netdev(0, "lo", loopback_setup);
if (!dev)
goto out;
dev_net_set(dev, net);
err = register_netdev(dev);
if (err)
goto out_free_netdev;
net->loopback_dev = dev;
return 0;
out_free_netdev:
free_netdev(dev);
out:
if (net_eq(net, &init_net))
panic("loopback: Failed to register netdevice: %d\n", err);
return err;
}
/* Registered in net/core/dev.c */
struct pernet_operations __net_initdata loopback_net_ops = {
.init = loopback_net_init,
};
自己將兩份原始碼對照著看了,暫時還沒找出原因,這裡先上一張錯誤的截圖以及我認為出錯的原因