snull.c

Linux 设备驱动 Edition 3,书中的例题

/*
 * 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/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 <linux/skbuff.h>

#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;
};

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 net_device *dev, int *budget)
{
	int npackets = 0, quota = min(dev->quota, *budget);
	struct sk_buff *skb;
	struct snull_priv *priv = netdev_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);
		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);