rawtx.c.2

实现一个网卡到内存空间的零拷贝程序

/*
 *  rawtx.c
 *  Joris van Rantwijk, May 2001.
 *
 *  Desperate attempt to implement a quick-and-dirty zero-copy
 *  networking interface in the Linux kernel.
 */

#define __KERNEL__
#define MODULE

#include <linux/stddef.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/ip.h>
#include <linux/unistd.h>
#include <linux/if_ether.h>
#include <linux/etherdevice.h>
#include <asm/uaccess.h>
#include "rawtx.h"

#define MODNAME		"rawtx"

#define __NR_invalid	0

#define DEVICE_NAME	"eth0"

extern void *sys_call_table[];
struct net_device *dev;


static void rawtx_skb_destructor(struct sk_buff *skb)
{
	printk(KERN_NOTICE "releasing skb %p\n", skb);
}

static int do_raw_tx(unsigned char *usaddr, unsigned char *udaddr,
                     void *buf, size_t len)
{
	struct sk_buff *skb;
	unsigned char saddr[6], daddr[6];
	int err;

	/* TODO: Check permissions */

	/* Copy source and dest addresses */
	if ( copy_from_user(saddr, usaddr, sizeof(saddr)) ||
	     copy_from_user(daddr, udaddr, sizeof(daddr)) )
		return -EFAULT;

	/* Check packet length */
	if (len >= dev->mtu)
		return -EMSGSIZE;

	/* Allocate sk_buff */
	skb = alloc_skb(len + dev->hard_header_len + 15, GFP_KERNEL);
	if (skb == NULL)
		return -ENOBUFS;

	printk(KERN_NOTICE "have skb\n");

	skb->sk = NULL;		/* allowed ? */
	skb->destructor = rawtx_skb_destructor;
	skb_reserve(skb, dev->hard_header_len);
	skb->priority = 0;
	skb->dst = NULL;	/* allowed ? */
	skb->dev = dev;
	skb->protocol = htons(ETH_P_IP);
	skb->ip_summed = CHECKSUM_NONE;

	/* Copy user data */
	skb->h.raw = skb_put(skb, len);
	if (copy_from_user(skb->h.raw, buf, len)) {
		kfree_skb(skb);
		return -EFAULT;
	}

	printk(KERN_NOTICE "data copied\n");

	/* Add ethernet header */
	err = dev->hard_header(skb, dev, ntohs(skb->protocol), daddr, saddr, len);
	if (err < 0) {
		kfree_skb(skb);
		return err;
	}

	/* Send packet */
	err = dev_queue_xmit(skb);
	printk(KERN_NOTICE "packet sent\n");

	return err;
}


static asmlinkage int sys_rawtx(unsigned char * saddr, unsigned char * daddr, void *buf, size_t len)
{
	printk(KERN_NOTICE MODNAME ": sys_rawtx(%p, %p, %p, %u)\n", saddr, daddr, buf, len);
	return do_raw_tx(saddr, daddr, buf, len);
}


int rawtx_init(void)
{
	printk(KERN_INFO MODNAME ": Initializing module.\n");

	if (sys_call_table[__NR_rawtx] != sys_call_table[__NR_invalid]) {
		printk(KERN_ERR ": ERROR: systemcall %d already used.\n", __NR_rawtx);
		return -EBUSY;
	}

	dev = dev_get_by_name(DEVICE_NAME);
	if (dev == NULL) {
		printk(KERN_ERR ": ERROR: Cannot find device '%s'.\n", DEVICE_NAME);
		return -EBUSY;
	}

	sys_call_table[__NR_rawtx] = sys_rawtx;

	return 0;
}


void rawtx_cleanup(void)
{
	printk(KERN_INFO MODNAME ": Removing module.\n");

	if (sys_call_table[__NR_rawtx] == sys_rawtx)
		sys_call_table[__NR_rawtx] = sys_call_table[__NR_invalid];
}

module_init(rawtx_init);
module_exit(rawtx_cleanup);

/* end */