/***************************************************************************
 *   Copyright (C) 2007 by Intra2net AG                                    *
 *   opensource@intra2net.com                                              *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License                  *
 *   version 2 as published by the Free Software Foundation;               *
 *                                                                         *
 ***************************************************************************/

#include <linux/module.h>
#include <linux/version.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <net/icmp.h>
#include <net/udp.h>
#include <net/tcp.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_CRASH.h>
#include <asm/semaphore.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/spinlock.h>
#include <asm/uaccess.h>

/* Spinlock used during memory allocation */
static DEFINE_SPINLOCK(ipt_crash_lock);

static unsigned int ipt_crash_target(struct sk_buff **pskb,
                                   const struct net_device *in,
                                   const struct net_device *out,
                                   unsigned int hooknum,
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,17)
                                   const struct xt_target *target,
#endif
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,19)
                                   const void *targinfo)
#else
                                   const void *targinfo,
                                   void *userinfo)
#endif
{
    char *data;

    spin_lock_bh(&ipt_crash_lock);

    if ((data = (char *)get_zeroed_page(GFP_ATOMIC)) == NULL) {
        printk("ipt_CRASH: Out of memory!\n");
    } else {
        // Fill memory with pattern
        int i, j = 123;
        for (i = 0; i < PAGE_SIZE; i++) {
            data[i] = j;
            j++;
        }

        free_page((unsigned long)data);
    }

    spin_unlock_bh(&ipt_crash_lock);

    return IPT_CONTINUE;
}

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,21)
static struct xt_target xt_crash_reg = {
#else
static struct ipt_target ipt_crash_reg = {
#endif
    .name = "CRASH",
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,21)
    .family = AF_INET,
#endif
    .target = ipt_crash_target,
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,17)
    .targetsize = sizeof(struct ipt_crash_info),
#endif
    .me = THIS_MODULE
};

static int __init init(void)
{
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,21)
    if (xt_register_target(&xt_crash_reg))
#else
    if (ipt_register_target(&ipt_crash_reg))
#endif
        return -EINVAL;

    return 0;
}

static void __exit fini(void)
{
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,21)
    xt_unregister_target(&xt_crash_reg);
#else
    ipt_unregister_target(&ipt_crash_reg);
#endif
}

module_init(init);
module_exit(fini);
MODULE_LICENSE("GPL");