/*
       *	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)
      {
  49  	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);
  57  	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;
  64  		toks -= net_msg_cost;
      		spin_unlock_irqrestore(&ratelimit_lock, flags);
      		if (lost)
      			printk(KERN_WARNING "NET: %d messages suppressed.\n", lost);
      		return 1;
      	}
      	missed++;
  71  	spin_unlock_irqrestore(&ratelimit_lock, flags);
      	return 0;
      }