/*
* Transmit a packet (low level interface)
* 真正的处理的发送数据包
*/
void snull_hw_tx(char *buf, int len, struct net_device *dev)
{
printk("snull_hw_tx\n");
struct iphdr *ih;//ip头部
struct snull_priv *priv = netdev_priv(dev);//获取私有数据
u32 *saddr, *daddr;//源设备地址与目标设备地址
//检查数据长度大小
if (len < sizeof(struct ethhdr) + sizeof(struct iphdr))
{
printk("snull: Hmm... packet too short (%i octets)\n",len);
return;
}
/* 开始发送数据(此处获取了ip地址用于打印）*/
ih = (struct iphdr *)(buf + sizeof(struct ethhdr));
saddr = &ih->saddr;
daddr = &ih->daddr;
printk("%pI4->%pI4\n", saddr, daddr);
/* 调用中断模拟发送完毕 */
priv->status = SNULL_TX_INTR;
priv->rx_packetlen = len;
priv->rx_packetdata = buf;
snull_interrupt(0, dev, NULL);
return;
}
/*
* Deal with a transmit timeout.
*/
void snull_tx_timeout (struct net_device *dev)
{
struct snull_priv *priv = (struct snull_priv *)dev->priv;
PDEBUG("Transmit timeout at %ld, latency %ld\n", jiffies,
jiffies - dev->trans_start);
priv->status = SNULL_TX_INTR;
snull_interrupt(0, dev, NULL);
priv->stats.tx_errors++;
netif_wake_queue(dev);
}
/*
* 一旦超出watchdog_timeo就会调用snull_tx_timeout
*/
void snull_tx_timeout (struct net_device *dev)
{
printk("snull_tx_timeout\n");
struct snull_priv *priv = netdev_priv(dev);
printk(KERN_INFO"Transmit timeout at %ld, latency %ld\n", jiffies,jiffies - dev->trans_start);
priv->status = SNULL_TX_INTR;
snull_interrupt(0, dev, NULL);//超时后发生中断
priv->stats.tx_errors++;//发送的错误数
netif_wake_queue(dev);//为了再次发送数据，调用此函数，重新启动发送队列
return;
}
/*
* Transmit a packet (low level interface)
*/
void snull_hw_tx(char *buf, int len, struct net_device *dev)
{
/*
* This function deals with hw details. This interface loops
* back the packet to the other snull interface (if any).
* In other words, this function implements the snull behaviour,
* while all other procedures are rather device-independent
*/
struct iphdr *ih;
struct net_device *dest;
struct snull_priv *privp;
u32 *saddr, *daddr;
/* I am paranoid. Ain't I? */
if (len < sizeof(struct ethhdr) + sizeof(struct iphdr)) {
printk("snull: Hmm... packet too short (%i octets)\n",
len);
return;
}
if (0) { /* enable this conditional to look at the data */
int i;
PDEBUG("len is %i\n" KERN_DEBUG "data:",len);
for (i=14 ; i<len; i++)
printk(" %02x",buf[i]&0xff);
printk("\n");
}
/*
* Ethhdr is 14 bytes, but the kernel arranges for iphdr
* to be aligned (i.e., ethhdr is unaligned)
*/
ih = (struct iphdr *)(buf+sizeof(struct ethhdr));
saddr = &ih->saddr;
daddr = &ih->daddr;
((u8 *)saddr)[2] ^= 1; /* change the third octet (class C) */
((u8 *)daddr)[2] ^= 1;
ih->check = 0; /* and rebuild the checksum (ip needs it) */
ih->check = ip_fast_csum((unsigned char *)ih,ih->ihl);
if (dev == snull_devs)
PDEBUGG("%08x:%05i --> %08x:%05i\n",
ntohl(ih->saddr),ntohs(((struct tcphdr *)(ih+1))->source),
ntohl(ih->daddr),ntohs(((struct tcphdr *)(ih+1))->dest));
else
PDEBUGG("%08x:%05i <-- %08x:%05i\n",
ntohl(ih->daddr),ntohs(((struct tcphdr *)(ih+1))->dest),
ntohl(ih->saddr),ntohs(((struct tcphdr *)(ih+1))->source));
/*
* Ok, now the packet is ready for transmission: first simulate a
* receive interrupt on the twin device, then a
* transmission-done on the transmitting device
*/
dest = snull_devs + (dev==snull_devs ? 1 : 0);
privp = (struct snull_priv *)dest->priv;
privp->status = SNULL_RX_INTR;
privp->rx_packetlen = len;
privp->rx_packetdata = buf;
snull_interrupt(0, dest, NULL);
privp = (struct snull_priv *)dev->priv;
privp->status = SNULL_TX_INTR;
privp->tx_packetlen = len;
privp->tx_packetdata = buf;
if (lockup && ((privp->stats.tx_packets + 1) % lockup) == 0) {
/* Simulate a dropped transmit interrupt */
netif_stop_queue(dev);
PDEBUG("Simulate lockup at %ld, txp %ld\n", jiffies,
(unsigned long) privp->stats.tx_packets);
}
else
snull_interrupt(0, dev, NULL);
}