Import changeset

1 files changed, 73 insertions, 0 deletions

diff --git a/net/core/utils.c b/net/core/utils.c
new file mode 100644
index 000000000000..310393453181
--- /dev/null
+++ b/net/core/utils.c
@@ -0,0 +1,73 @@
+/*
+ *	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;
+}