设备驱动程序网络驱动程序的修改

该书中给出的snull例子，由于现在net_devices 中的接口部分改变了，所以有必要对其进行部分修改才能在现在的Linux 系统上运行。

我的系统是Ubuntu ，内核版本为：3.13.0

主要是多出了net_device_ops 和 header_ops结构体：完整程序如下：其中参考了：http://blog.csdn.net/xiebiwei/article/details/6210887#snull_header_ops

/*
 * snull.c --  the Simple Network Utility
 *
 * Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet
 * Copyright (C) 2001 O'Reilly & Associates
 *
 * The source code in this file can be freely used, adapted,
 * and redistributed in source or binary form, so long as an
 * acknowledgment appears in derived source files.  The citation
 * should list that the code comes from the book "Linux Device
 * Drivers" by Alessandro Rubini and Jonathan Corbet, published
 * by O'Reilly & Associates.   No warranty is attached;
 * we cannot take responsibility for errors or fitness for use.
 *
 * $Id: snull.c,v 1.21 2004/11/05 02:36:03 rubini Exp $
 */


//#include <linux/config.h>
#include <linux/skbuff.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/moduleparam.h>


#include <linux/sched.h>
#include <linux/kernel.h> /* printk() */
#include <linux/slab.h> /* kmalloc() */
#include <linux/errno.h>  /* error codes */
#include <linux/types.h>  /* size_t */
#include <linux/interrupt.h> /* mark_bh */


#include <linux/in.h>
#include <linux/netdevice.h>   /* struct device, and other headers */
#include <linux/etherdevice.h> /* eth_type_trans */
#include <linux/ip.h>          /* struct iphdr */
#include <linux/tcp.h>         /* struct tcphdr */


#include "snull.h"


#include <linux/in6.h>
#include <asm/checksum.h>


MODULE_AUTHOR("Alessandro Rubini, Jonathan Corbet");
MODULE_LICENSE("Dual BSD/GPL");




/*
 * Transmitter lockup simulation, normally disabled.
 */
static int lockup = 0;
module_param(lockup, int, 0);


static int timeout = SNULL_TIMEOUT;
module_param(timeout, int, 0);


/*
 * Do we run in NAPI mode?
 */
static int use_napi = 0;
module_param(use_napi, int, 0);




/*
 * A structure representing an in-flight packet.
 */
struct snull_packet {
struct snull_packet *next;
struct net_device *dev;
int datalen;
u8 data[ETH_DATA_LEN];
};


int pool_size = 8;
module_param(pool_size, int, 0);


/*
 * This structure is private to each device. It is used to pass
 * packets in and out, so there is place for a packet
 */


struct snull_priv {
struct net_device_stats stats;
int status;
struct snull_packet *ppool;
struct snull_packet *rx_queue;  /* List of incoming packets */
int rx_int_enabled;
int tx_packetlen;
u8 *tx_packetdata;
struct sk_buff *skb;
spinlock_t lock;
struct napi_struct napi;
struct net_device *dev;
};


static void snull_tx_timeout(struct net_device *dev);
static void (*snull_interrupt)(int, void *, struct pt_regs *);


/*
 * Set up a device's packet pool.
 */
void snull_setup_pool(struct net_device *dev)
{
struct snull_priv *priv = netdev_priv(dev);
int i;
struct snull_packet *pkt;


priv->ppool = NULL;
for (i = 0; i < pool_size; i++) {
pkt = kmalloc (sizeof (struct snull_packet), GFP_KERNEL);
if (pkt == NULL) {
printk (KERN_NOTICE "Ran out of memory allocating packet pool\n");
return;
}
pkt->dev = dev;
pkt->next = priv->ppool;
priv->ppool = pkt;
}
}


void snull_teardown_pool(struct net_device *dev)
{
struct snull_priv *priv = netdev_priv(dev);
struct snull_packet *pkt;
    
while ((pkt = priv->ppool)) {
priv->ppool = pkt->next;
kfree (pkt);
/* FIXME - in-flight packets ? */
}
}    


/*
 * Buffer/pool management.
 */
struct snull_packet *snull_get_tx_buffer(struct net_device *dev)
{
struct snull_priv *priv = netdev_priv(dev);
unsigned long flags;
struct snull_packet *pkt;
    
spin_lock_irqsave(&priv->lock, flags);
pkt = priv->ppool;
priv->ppool = pkt->next;
if (priv->ppool == NULL) {
printk (KERN_INFO "Pool empty\n");
netif_stop_queue(dev);
}
spin_unlock_irqrestore(&priv->lock, flags);
return pkt;
}




void snull_release_buffer(struct snull_packet *pkt)
{
unsigned long flags;
struct snull_priv *priv = netdev_priv(pkt->dev);

spin_lock_irqsave(&priv->lock, flags);
pkt->next = priv->ppool;
priv->ppool = pkt;
spin_unlock_irqrestore(&priv->lock, flags);
if (netif_queue_stopped(pkt->dev) && pkt->next == NULL)
netif_wake_queue(pkt->dev);
}


void snull_enqueue_buf(struct net_device *dev, struct snull_packet *pkt)
{
unsigned long flags;
struct snull_priv *priv = netdev_priv(dev);


spin_lock_irqsave(&priv->lock, flags);
pkt->next = priv->rx_queue;  /* FIXME - misorders packets */
priv->rx_queue = pkt;
spin_unlock_irqrestore(&priv->lock, flags);
}


struct snull_packet *snull_dequeue_buf(struct net_device *dev)
{
struct snull_priv *priv = netdev_priv(dev);
struct snull_packet *pkt;
unsigned long flags;


spin_lock_irqsave(&priv->lock, flags);
pkt = priv->rx_queue;
if (pkt != NULL)
priv->rx_queue = pkt->next;
spin_unlock_irqrestore(&priv->lock, flags);
return pkt;
}


/*
 * Enable and disable receive interrupts.
 */
static void snull_rx_ints(struct net_device *dev, int enable)
{
struct snull_priv *priv = netdev_priv(dev);
priv->rx_int_enabled = enable;
}


    
/*
 * Open and close
 */


int snull_open(struct net_device *dev)
{
/* request_region(), request_irq(), ....  (like fops->open) */


/* 
* Assign the hardware address of the board: use "\0SNULx", where
* x is 0 or 1. The first byte is '\0' to avoid being a multicast
* address (the first byte of multicast addrs is odd).
*/
memcpy(dev->dev_addr, "\0SNUL0", ETH_ALEN);
if (dev == snull_devs[1])
dev->dev_addr[ETH_ALEN-1]++; /* \0SNUL1 */
netif_start_queue(dev);
return 0;
}


int snull_release(struct net_device *dev)
{
    /* release ports, irq and such -- like fops->close */


netif_stop_queue(dev); /* can't transmit any more */
return 0;
}


/*
 * Configuration changes (passed on by ifconfig)
 */
int snull_config(struct net_device *dev, struct ifmap *map)
{
if (dev->flags & IFF_UP) /* can't act on a running interface */
return -EBUSY;


/* Don't allow changing the I/O address */
if (map->base_addr != dev->base_addr) {
printk(KERN_WARNING "snull: Can't change I/O address\n");
return -EOPNOTSUPP;
}


/* Allow changing the IRQ */
if (map->irq != dev->irq) {
dev->irq = map->irq;
        /* request_irq() is delayed to open-time */
}


/* ignore other fields */
return 0;
}


/*
 * Receive a packet: retrieve, encapsulate and pass over to upper levels
 */
void snull_rx(struct net_device *dev, struct snull_packet *pkt)
{
struct sk_buff *skb;
struct snull_priv *priv = netdev_priv(dev);


/*
* The packet has been retrieved from the transmission
* medium. Build an skb around it, so upper layers can handle it
*/
skb = dev_alloc_skb(pkt->datalen + 2);
if (!skb) {
if (printk_ratelimit())
printk(KERN_NOTICE "snull rx: low on mem - packet dropped\n");
priv->stats.rx_dropped++;
goto out;
}
skb_reserve(skb, 2); /* align IP on 16B boundary */  
memcpy(skb_put(skb, pkt->datalen), pkt->data, pkt->datalen);


/* Write metadata, and then pass to the receive level */
skb->dev = dev;
skb->protocol = eth_type_trans(skb, dev);
skb->ip_summed = CHECKSUM_UNNECESSARY; /* don't check it */
priv->stats.rx_packets++;
priv->stats.rx_bytes += pkt->datalen;
netif_rx(skb);
  out:
return;
}
    


/*
 * The poll implementation.
 */
static int snull_poll(struct napi_struct *napi, int budget)
{
int npackets = 0/*, quota = min(dev->quota, *budget)*/;
int quota = budget;
struct sk_buff *skb;
//struct snull_priv *priv = netdev_priv(dev);
struct snull_priv *priv = container_of(napi, struct snull_priv, napi);
struct net_device *dev = priv->dev;
struct snull_packet *pkt;
    
while (npackets < quota && priv->rx_queue) {
pkt = snull_dequeue_buf(dev);
skb = dev_alloc_skb(pkt->datalen + 2);
if (! skb) {
if (printk_ratelimit())
printk(KERN_NOTICE "snull: packet dropped\n");
priv->stats.rx_dropped++;
snull_release_buffer(pkt);
continue;
}
skb_reserve(skb, 2); /* align IP on 16B boundary */  
memcpy(skb_put(skb, pkt->datalen), pkt->data, pkt->datalen);
skb->dev = dev;
skb->protocol = eth_type_trans(skb, dev);
skb->ip_summed = CHECKSUM_UNNECESSARY; /* don't check it */
netif_receive_skb(skb);

        /* Maintain stats */
npackets++;
priv->stats.rx_packets++;
priv->stats.rx_bytes += pkt->datalen;
snull_release_buffer(pkt);
}
/* If we processed all packets, we're done; tell the kernel and reenable ints */
//*budget -= npackets;
//dev->quota -= npackets;
if (! priv->rx_queue) {
//netif_rx_complete(dev);
napi_complete(&priv->napi);
snull_rx_ints(dev, 1);
return 0;
}
/* We couldn't process everything. */
return 1;
}
   
        
/*
 * The typical interrupt entry point
 */
static void snull_regular_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
int statusword;
struct snull_priv *priv;
struct snull_packet *pkt = NULL;
/*
* As usual, check the "device" pointer to be sure it is
* really interrupting.
* Then assign "struct device *dev"
*/
struct net_device *dev = (struct net_device *)dev_id;
/* ... and check with hw if it's really ours */


/* paranoid */
if (!dev)
return;


/* Lock the device */
priv = netdev_priv(dev);
spin_lock(&priv->lock);


/* retrieve statusword: real netdevices use I/O instructions */
statusword = priv->status;
priv->status = 0;
if (statusword & SNULL_RX_INTR) {
/* send it to snull_rx for handling */
pkt = priv->rx_queue;
if (pkt) {
priv->rx_queue = pkt->next;
snull_rx(dev, pkt);
}
}
if (statusword & SNULL_TX_INTR) {
/* a transmission is over: free the skb */
priv->stats.tx_packets++;
priv->stats.tx_bytes += priv->tx_packetlen;
dev_kfree_skb(priv->skb);
}


/* Unlock the device and we are done */
spin_unlock(&priv->lock);
if (pkt) snull_release_buffer(pkt); /* Do this outside the lock! */
return;
}


/*
 * A NAPI interrupt handler.
 */
static void snull_napi_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
int statusword;
struct snull_priv *priv;


/*
* As usual, check the "device" pointer for shared handlers.
* Then assign "struct device *dev"
*/
struct net_device *dev = (struct net_device *)dev_id;
/* ... and check with hw if it's really ours */


/* paranoid */
if (!dev)
return;


/* Lock the device */
priv = netdev_priv(dev);
spin_lock(&priv->lock);


/* retrieve statusword: real netdevices use I/O instructions */
statusword = priv->status;
priv->status = 0;
if (statusword & SNULL_RX_INTR) {
snull_rx_ints(dev, 0);  /* Disable further interrupts */
//netif_rx_schedule(dev);
napi_schedule(&priv->napi);
}
if (statusword & SNULL_TX_INTR) {
        /* a transmission is over: free the skb */
priv->stats.tx_packets++;
priv->stats.tx_bytes += priv->tx_packetlen;
dev_kfree_skb(priv->skb);
}


/* Unlock the device and we are done */
spin_unlock(&priv->lock);
return;
}






/*
 * Transmit a packet (low level interface)
 */
static 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 *priv;
u32 *saddr, *daddr;
struct snull_packet *tx_buffer;
    
/* 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 (1) { /* 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[0])
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[0] ? 1 : 0];
priv = netdev_priv(dest);
tx_buffer = snull_get_tx_buffer(dev);
tx_buffer->datalen = len;
memcpy(tx_buffer->data, buf, len);
snull_enqueue_buf(dest, tx_buffer);
if (priv->rx_int_enabled) {
priv->status |= SNULL_RX_INTR;
snull_interrupt(0, dest, NULL);
}


priv = netdev_priv(dev);
priv->tx_packetlen = len;
priv->tx_packetdata = buf;
priv->status |= SNULL_TX_INTR;
if (lockup && ((priv->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) priv->stats.tx_packets);
}
else
snull_interrupt(0, dev, NULL);
}


/*
 * Transmit a packet (called by the kernel)
 */
int snull_tx(struct sk_buff *skb, struct net_device *dev)
{
int len;
char *data, shortpkt[ETH_ZLEN];
struct snull_priv *priv = netdev_priv(dev);

data = skb->data;
len = skb->len;
if (len < ETH_ZLEN) {
memset(shortpkt, 0, ETH_ZLEN);
memcpy(shortpkt, skb->data, skb->len);
len = ETH_ZLEN;
data = shortpkt;
}
dev->trans_start = jiffies; /* save the timestamp */


/* Remember the skb, so we can free it at interrupt time */
priv->skb = skb;


/* actual deliver of data is device-specific, and not shown here */
snull_hw_tx(data, len, dev);


return 0; /* Our simple device can not fail */
}


/*
 * Deal with a transmit timeout.
 */
void snull_tx_timeout (struct net_device *dev)
{
struct snull_priv *priv = netdev_priv(dev);


PDEBUG("Transmit timeout at %ld, latency %ld\n", jiffies,
jiffies - dev->trans_start);
        /* Simulate a transmission interrupt to get things moving */
priv->status = SNULL_TX_INTR;
snull_interrupt(0, dev, NULL);
priv->stats.tx_errors++;
netif_wake_queue(dev);
return;
}






/*
 * Ioctl commands 
 */
int snull_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
{
PDEBUG("ioctl\n");
return 0;
}


/*
 * Return statistics to the caller
 */
struct net_device_stats *snull_stats(struct net_device *dev)
{
struct snull_priv *priv = netdev_priv(dev);
return &priv->stats;
}


/*
 * This function is called to fill up an eth header, since arp is not
 * available on the interface
 */
int snull_rebuild_header(struct sk_buff *skb)
{
struct ethhdr *eth = (struct ethhdr *) skb->data;
struct net_device *dev = skb->dev;
    
memcpy(eth->h_source, dev->dev_addr, dev->addr_len);
memcpy(eth->h_dest, dev->dev_addr, dev->addr_len);
eth->h_dest[ETH_ALEN-1]   ^= 0x01;   /* dest is us xor 1 */
return 0;
}




int snull_header(struct sk_buff *skb, struct net_device *dev,
                unsigned short type, /*void *daddr, void *saddr,
                unsigned int len*/const void *daddr, const void *saddr, unsigned len)
{
struct ethhdr *eth = (struct ethhdr *)skb_push(skb,ETH_HLEN);


eth->h_proto = htons(type);
memcpy(eth->h_source, saddr ? saddr : dev->dev_addr, dev->addr_len);
memcpy(eth->h_dest,   daddr ? daddr : dev->dev_addr, dev->addr_len);
eth->h_dest[ETH_ALEN-1]   ^= 0x01;   /* dest is us xor 1 */
return (dev->hard_header_len);
}










/*
 * The "change_mtu" method is usually not needed.
 * If you need it, it must be like this.
 */
int snull_change_mtu(struct net_device *dev, int new_mtu)
{
unsigned long flags;
struct snull_priv *priv = netdev_priv(dev);
spinlock_t *lock = &priv->lock;
    
/* check ranges */
if ((new_mtu < 68) || (new_mtu > 1500))
return -EINVAL;
/*
* Do anything you need, and the accept the value
*/
spin_lock_irqsave(lock, flags);
dev->mtu = new_mtu;
spin_unlock_irqrestore(lock, flags);
return 0; /* success */
}


/*
 * The init function (sometimes called probe).
 * It is invoked by register_netdev()
 */
 static const struct net_device_ops snull_init_netdev_ops0 = {
    .ndo_open       = snull_open,
    .ndo_stop     = snull_release,
    .ndo_set_config = snull_config,
    .ndo_start_xmit = snull_tx,
    .ndo_do_ioctl = snull_ioctl,
    .ndo_get_stats = snull_stats,
    .ndo_change_mtu = snull_change_mtu,
    .ndo_tx_timeout = snull_tx_timeout,
    
};
static const struct header_ops snull_init_header_ops0 = {
.create = snull_header,
.rebuild = snull_rebuild_header,
.cache = NULL,
};
 static const struct net_device_ops snull_init_netdev_ops1 = {
    .ndo_open       = snull_open,
    .ndo_stop     = snull_release,
    .ndo_set_config = snull_config,
    .ndo_start_xmit = snull_tx,
    .ndo_do_ioctl = snull_ioctl,
    .ndo_get_stats = snull_stats,
    .ndo_change_mtu = snull_change_mtu,
    .ndo_tx_timeout = snull_tx_timeout,
    
};
static const struct header_ops snull_init_header_ops1 = {
.create = snull_header,
.rebuild = snull_rebuild_header,
.cache = NULL,
};


void snull_init(struct net_device *dev)
{
struct snull_priv *priv;
#if 0
    /*
* Make the usual checks: check_region(), probe irq, ...  -ENODEV
* should be returned if no device found.  No resource should be
* grabbed: this is done on open(). 
*/
#endif


    /* 
* Then, assign other fields in dev, using ether_setup() and some
* hand assignments
*/


dev->watchdog_timeo = timeout;
/*if (use_napi) {
dev->poll        = snull_poll;
dev->weight      = 2;
}*/
/* keep the default flags, just add NOARP */
dev->flags           |= IFF_NOARP;
dev->features        |= NETIF_F_RXALL;
//dev->hard_header_cache = NULL;      /* Disable caching */


/*
* Then, initialize the priv field. This encloses the statistics
* and a few private fields.
*/
priv = netdev_priv(dev);
memset(priv, 0, sizeof(struct snull_priv));
priv->dev = dev;
spin_lock_init(&priv->lock);
snull_rx_ints(dev, 1);/* enable receive interrupts */
snull_setup_pool(dev);
if (use_napi) {
  netif_napi_add(dev,&priv->napi,snull_poll,2);
}
}


/*
 * The devices
 */


struct net_device *snull_devs[2];






/*
 * Finally, the module stuff
 */


void snull_cleanup(void)
{
int i;
    
for (i = 0; i < 2;  i++) {
if (snull_devs[i]) {
unregister_netdev(snull_devs[i]);
snull_teardown_pool(snull_devs[i]);
free_netdev(snull_devs[i]);
}
}
return;
}








int snull_init_module(void)
{
int result, i, ret = -ENOMEM;


snull_interrupt = use_napi ? snull_napi_interrupt : snull_regular_interrupt;


/* Allocate the devices */
//snull_devs[0] = alloc_netdev(sizeof(struct snull_priv), "sn%d",
// snull_init);
snull_devs[0] =  alloc_netdev(sizeof(struct snull_priv), "sn%d", ether_setup);


snull_devs[1] = alloc_netdev(sizeof(struct snull_priv), "sn%d",ether_setup);
//snull_init);
if (snull_devs[0] == NULL || snull_devs[1] == NULL)
goto out;

snull_devs[0]->netdev_ops = &snull_init_netdev_ops0;
snull_devs[0]->header_ops = &snull_init_header_ops0;
snull_init(snull_devs[0]);
snull_devs[1]->netdev_ops = &snull_init_netdev_ops1;
   snull_devs[1]->header_ops = &snull_init_header_ops1;
snull_init(snull_devs[1]);

ret = -ENODEV;
for (i = 0; i < 2;  i++)
if ((result = register_netdev(snull_devs[i])))
printk("snull: error %i registering device \"%s\"\n",
result, snull_devs[i]->name);
else
ret = 0;
   out:
if (ret) 
snull_cleanup();
return ret;
}




module_init(snull_init_module);
module_exit(snull_cleanup);