rawtx.c.1

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/errno.h>
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/ip.h>
#include <linux/unistd.h>
#include <net/route.h>
#include <net/dst.h>
#include <asm/uaccess.h>
#include "rawtx.h"

#define MODNAME		"rawtx"

#define __NR_invalid	0

#define PACKET_MAX_SIZE	1600

extern void *sys_call_table[];


static int do_raw_tx(u32 saddr, u32 daddr, void *buf, size_t len)
{
	struct rtable *rt;
	struct sk_buff *skb;
	int hh_len, err;

	/* TODO: Check permissions */

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

	/* Lookup routing table */
	err = ip_route_output(&rt, daddr, saddr, 0, 0);
	if (err)
		goto out;

	printk(KERN_NOTICE "done ip_route_output\n");

	/* Allocate sk_buff */
	hh_len = (rt->u.dst.dev->hard_header_len + 15) & ~15;
	skb = alloc_skb(len+hh_len+15, GFP_KERNEL);
	if (skb == NULL) {
		err = -ENOBUFS;
		goto out;
	}

	printk(KERN_NOTICE "have skb\n");

	skb->sk = NULL;		/* allowed ? */
	skb->destructor = NULL;
	skb_reserve(skb, hh_len);

	skb->priority = 0;
	skb->dst = dst_clone(&rt->u.dst);

	/* 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");

	/* Send packet */
	err = skb->dst->output(skb);
	if (err)
		err = net_xmit_errno(err);

	printk(KERN_NOTICE "packet sent\n");

out:
	ip_rt_put(rt);

	return err;
}


static asmlinkage int sys_rawtx(u32 saddr, u32 daddr, void *buf, size_t len)
{
	printk(KERN_NOTICE MODNAME ": sys_rawtx(%x, %x, %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;
	}

	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 */