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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;
}
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