patch-2.1.79 linux/net/core/utils.c

• Lines: 60
• Date: Mon Jan 12 15:28:25 1998
• Orig file: v2.1.78/linux/net/core/utils.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.1.78/linux/net/core/utils.c linux/net/core/utils.c
@@ -0,0 +1,59 @@
+/*
+ *	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();
+}
+
+
+/* 
+ * 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 unsigned long last_msg; 
+	static int missed;
+	
+	if ((jiffies - last_msg) >= 5*HZ) {
+		if (missed)	
+			printk(KERN_WARNING "ipv4: (%d messages suppressed. Flood?)\n", missed);
+		missed = 0; 
+		last_msg = jiffies;
+		return 1;
+	}
+	missed++; 
+	return 0; 
+}