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/*

 *      Generic address resultion entity

 *

 *      Authors:

 *      net_random Alan Cox

 *      net_ratelimit Andy Kleen

 *

 *      Created by Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>

 *

 *      This program is free software; you can redistribute it and/or

 *      modify it under the terms of the GNU General Public License

 *      as published by the Free Software Foundation; either version

 *      2 of the License, or (at your option) any later version.

 */

#include <asm/uaccess.h>

#include <asm/system.h>

#include <linux/types.h>

#include <linux/kernel.h>

#include <linux/sched.h>

#include <linux/string.h>

#include <linux/mm.h>

static unsigned long net_rand_seed = 152L;

unsigned long net_random(void)

{

        net_rand_seed=net_rand_seed*69069L+1;

        return net_rand_seed^jiffies;

}

void net_srandom(unsigned long entropy)

{

        net_rand_seed ^= entropy;

        net_random();

}

int net_msg_cost = 5*HZ;

int net_msg_burst = 10*5*HZ;

/*

 * This enforces a rate limit: not more than one kernel message

 * every 5secs to make a denial-of-service attack impossible.

 *

 * All warning printk()s should be guarded by this function.

 */

int net_ratelimit(void)

{

        static spinlock_t ratelimit_lock = SPIN_LOCK_UNLOCKED;

        static unsigned long toks = 10*5*HZ;

        static unsigned long last_msg;

        static int missed;

        unsigned long flags;

        unsigned long now = jiffies;

        spin_lock_irqsave(&ratelimit_lock, flags);

        toks += now - last_msg;

        last_msg = now;

        if (toks > net_msg_burst)

                toks = net_msg_burst;

        if (toks >= net_msg_cost) {

                int lost = missed;

                missed = 0;

                toks -= net_msg_cost;

                spin_unlock_irqrestore(&ratelimit_lock, flags);

                if (lost)

                        printk(KERN_WARNING "NET: %d messages suppressed.\n", lost);

                return 1;

        }

        missed++;

        spin_unlock_irqrestore(&ratelimit_lock, flags);

        return 0;

}