1 files changed, 129 insertions, 0 deletions
diff --git a/net/bridge/netfilter/ebt_limit.c b/net/bridge/netfilter/ebt_limit.c
new file mode 100644
index 000000000..e16183bd1
--- /dev/null
+++ b/net/bridge/netfilter/ebt_limit.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  ebt_limit
+ *
+ *	Authors:
+ *	Tom Marshall <tommy@home.tig-grr.com>
+ *
+ *	Mostly copied from netfilter's ipt_limit.c, see that file for
+ *	more explanation
+ *
+ *  September, 2003
+ *
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/spinlock.h>
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter_bridge/ebtables.h>
+#include <linux/netfilter_bridge/ebt_limit.h>
+
+static DEFINE_SPINLOCK(limit_lock);
+
+#define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))
+
+#define _POW2_BELOW2(x) ((x)|((x)>>1))
+#define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2))
+#define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4))
+#define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8))
+#define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16))
+#define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1)
+
+#define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ)
+
+static bool
+ebt_limit_mt(const struct sk_buff *skb, struct xt_action_param *par)
+{
+	struct ebt_limit_info *info = (void *)par->matchinfo;
+	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 true;
+	}
+
+	spin_unlock_bh(&limit_lock);
+	return false;
+}
+
+/* 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_mt_check(const struct xt_mtchk_param *par)
+{
+	struct ebt_limit_info *info = par->matchinfo;
+
+	/* Check for overflow. */
+	if (info->burst == 0 ||
+	    user2credits(info->avg * info->burst) < user2credits(info->avg)) {
+		pr_info_ratelimited("overflow, try lower: %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;
+}
+
+
+#ifdef CONFIG_NETFILTER_XTABLES_COMPAT
+/*
+ * no conversion function needed --
+ * only avg/burst have meaningful values in userspace.
+ */
+struct ebt_compat_limit_info {
+	compat_uint_t avg, burst;
+	compat_ulong_t prev;
+	compat_uint_t credit, credit_cap, cost;
+};
+#endif
+
+static struct xt_match ebt_limit_mt_reg __read_mostly = {
+	.name		= "limit",
+	.revision	= 0,
+	.family		= NFPROTO_BRIDGE,
+	.match		= ebt_limit_mt,
+	.checkentry	= ebt_limit_mt_check,
+	.matchsize	= sizeof(struct ebt_limit_info),
+	.usersize	= offsetof(struct ebt_limit_info, prev),
+#ifdef CONFIG_NETFILTER_XTABLES_COMPAT
+	.compatsize	= sizeof(struct ebt_compat_limit_info),
+#endif
+	.me		= THIS_MODULE,
+};
+
+static int __init ebt_limit_init(void)
+{
+	return xt_register_match(&ebt_limit_mt_reg);
+}
+
+static void __exit ebt_limit_fini(void)
+{
+	xt_unregister_match(&ebt_limit_mt_reg);
+}
+
+module_init(ebt_limit_init);
+module_exit(ebt_limit_fini);
+MODULE_DESCRIPTION("Ebtables: Rate-limit match");
+MODULE_LICENSE("GPL");