1 files changed, 123 insertions, 0 deletions
diff --git a/kernel/linux/net/bridge/netfilter/ebt_limit.c b/kernel/linux/net/bridge/netfilter/ebt_limit.c
new file mode 100644
index 0000000..5947e56
--- /dev/null
+++ b/kernel/linux/net/bridge/netfilter/ebt_limit.c
@@ -0,0 +1,123 @@
+/*
+ *  ebt_limit
+ *
+ *	Authors:
+ *	Tom Marshall <tommy@home.tig-grr.com>
+ *
+ *	Mostly copied from netfilter's ipt_limit.c
+ *
+ *  September, 2003
+ *
+ */
+
+#include <linux/netfilter_bridge/ebtables.h>
+#include <linux/netfilter_bridge/ebt_limit.h>
+#include <linux/module.h>
+
+#include <linux/netdevice.h>
+#include <linux/spinlock.h>
+
+/* The algorithm used is the Simple Token Bucket Filter (TBF)
+ * see net/sched/sch_tbf.c in the linux source tree
+ */
+
+static spinlock_t limit_lock = SPIN_LOCK_UNLOCKED;
+
+/* Rusty: This is my (non-mathematically-inclined) understanding of
+   this algorithm.  The `average rate' in jiffies becomes your initial
+   amount of credit `credit' and the most credit you can ever have
+   `credit_cap'.  The `peak rate' becomes the cost of passing the
+   test, `cost'.
+
+   `prev' tracks the last packet hit: you gain one credit per jiffy.
+   If you get credit balance more than this, the extra credit is
+   discarded.  Every time the match passes, you lose `cost' credits;
+   if you don't have that many, the test fails.
+
+   See Alexey's formal explanation in net/sched/sch_tbf.c.
+
+   To avoid underflow, we multiply by 128 (ie. you get 128 credits per
+   jiffy).  Hence a cost of 2^32-1, means one pass per 32768 seconds
+   at 1024HZ (or one every 9 hours).  A cost of 1 means 12800 passes
+   per second at 100HZ.  */
+
+#define CREDITS_PER_JIFFY 128
+
+static int ebt_limit_match(const struct sk_buff *skb, const struct net_device *in,
+   const struct net_device *out, const void *data, unsigned int datalen)
+{
+	struct ebt_limit_info *info = (struct ebt_limit_info *)data;
+	unsigned long now = jiffies;
+
+	spin_lock_bh(&limit_lock);
+	info->credit += (now - xchg(&info->prev, now)) * CREDITS_PER_JIFFY;
+	if (info->credit > info->credit_cap)
+		info->credit = info->credit_cap;
+
+	if (info->credit >= info->cost) {
+		/* We're not limited. */
+		info->credit -= info->cost;
+		spin_unlock_bh(&limit_lock);
+		return EBT_MATCH;
+	}
+
+	spin_unlock_bh(&limit_lock);
+	return EBT_NOMATCH;
+}
+
+/* Precision saver. */
+static u_int32_t
+user2credits(u_int32_t user)
+{
+	/* If multiplying would overflow... */
+	if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
+		/* Divide first. */
+		return (user / EBT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;
+
+	return (user * HZ * CREDITS_PER_JIFFY) / EBT_LIMIT_SCALE;
+}
+
+static int ebt_limit_check(const char *tablename, unsigned int hookmask,
+   const struct ebt_entry *e, void *data, unsigned int datalen)
+{
+	struct ebt_limit_info *info = (struct ebt_limit_info *)data;
+
+	if (datalen != EBT_ALIGN(sizeof(struct ebt_limit_info)))
+		return -EINVAL;
+
+	/* Check for overflow. */
+	if (info->burst == 0
+	    || user2credits(info->avg * info->burst) < user2credits(info->avg)) {
+		printk("Overflow in ebt_limit: %u/%u\n",
+			info->avg, info->burst);
+		return -EINVAL;
+	}
+
+	/* User avg in seconds * EBT_LIMIT_SCALE: convert to jiffies * 128. */
+	info->prev = jiffies;
+	info->credit = user2credits(info->avg * info->burst);
+	info->credit_cap = user2credits(info->avg * info->burst);
+	info->cost = user2credits(info->avg);
+	return 0;
+}
+
+static struct ebt_match ebt_limit_reg =
+{
+	{NULL, NULL}, EBT_LIMIT_MATCH, ebt_limit_match, ebt_limit_check, NULL,
+	THIS_MODULE
+};
+
+static int __init init(void)
+{
+	return ebt_register_match(&ebt_limit_reg);
+}
+
+static void __exit fini(void)
+{
+	ebt_unregister_match(&ebt_limit_reg);
+}
+
+module_init(init);
+module_exit(fini);
+EXPORT_NO_SYMBOLS;
+MODULE_LICENSE("GPL");