--- /dev/null
+/* (C) 1999 Jérôme de Vivie <devivie@info.enserb.u-bordeaux.fr>
+ * (C) 1999 Hervé Eychenne <eychenne@info.enserb.u-bordeaux.fr>
+ * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/spinlock.h>
+#include <linux/interrupt.h>
+
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter/xt_limit.h>
+
+struct xt_limit_priv {
+ unsigned long prev;
+ uint32_t credit;
+};
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Herve Eychenne <rv@wallfire.org>");
+MODULE_DESCRIPTION("Xtables: rate-limit match");
+MODULE_ALIAS("ipt_limit");
+MODULE_ALIAS("ip6t_limit");
+
+/* The algorithm used is the Simple Token Bucket Filter (TBF)
+ * see net/sched/sch_tbf.c in the linux source tree
+ */
+
+static DEFINE_SPINLOCK(limit_lock);
+
+/* 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 get the maxmum range, we multiply by this factor (ie. you get N
+ credits per jiffy). We want to allow a rate as low as 1 per day
+ (slowest userspace tool allows), which means
+ CREDITS_PER_JIFFY*HZ*60*60*24 < 2^32. ie. */
+#define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))
+
+/* Repeated shift and or gives us all 1s, final shift and add 1 gives
+ * us the power of 2 below the theoretical max, so GCC simply does a
+ * shift. */
+#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
+limit_mt(const struct sk_buff *skb, struct xt_action_param *par)
+{
+ const struct xt_rateinfo *r = par->matchinfo;
+ struct xt_limit_priv *priv = r->master;
+ unsigned long now = jiffies;
+
+ spin_lock_bh(&limit_lock);
+ priv->credit += (now - xchg(&priv->prev, now)) * CREDITS_PER_JIFFY;
+ if (priv->credit > r->credit_cap)
+ priv->credit = r->credit_cap;
+
+ if (priv->credit >= r->cost) {
+ /* We're not limited. */
+ priv->credit -= r->cost;
+ spin_unlock_bh(&limit_lock);
+ return true;
+ }
+
+ spin_unlock_bh(&limit_lock);
+ return false;
+}
+
+/* Precision saver. */
+static u32 user2credits(u32 user)
+{
+ /* If multiplying would overflow... */
+ if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
+ /* Divide first. */
+ return (user / XT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;
+
+ return (user * HZ * CREDITS_PER_JIFFY) / XT_LIMIT_SCALE;
+}
+
+static int limit_mt_check(const struct xt_mtchk_param *par)
+{
+ struct xt_rateinfo *r = par->matchinfo;
+ struct xt_limit_priv *priv;
+
+ /* Check for overflow. */
+ if (r->burst == 0
+ || user2credits(r->avg * r->burst) < user2credits(r->avg)) {
+ pr_info("Overflow, try lower: %u/%u\n",
+ r->avg, r->burst);
+ return -ERANGE;
+ }
+
+ priv = kmalloc(sizeof(*priv), GFP_KERNEL);
+ if (priv == NULL)
+ return -ENOMEM;
+
+ /* For SMP, we only want to use one set of state. */
+ r->master = priv;
+ /* User avg in seconds * XT_LIMIT_SCALE: convert to jiffies *
+ 128. */
+ priv->prev = jiffies;
+ priv->credit = user2credits(r->avg * r->burst); /* Credits full. */
+ if (r->cost == 0) {
+ r->credit_cap = priv->credit; /* Credits full. */
+ r->cost = user2credits(r->avg);
+ }
+ return 0;
+}
+
+static void limit_mt_destroy(const struct xt_mtdtor_param *par)
+{
+ const struct xt_rateinfo *info = par->matchinfo;
+
+ kfree(info->master);
+}
+
+#ifdef CONFIG_COMPAT
+struct compat_xt_rateinfo {
+ u_int32_t avg;
+ u_int32_t burst;
+
+ compat_ulong_t prev;
+ u_int32_t credit;
+ u_int32_t credit_cap, cost;
+
+ u_int32_t master;
+};
+
+/* To keep the full "prev" timestamp, the upper 32 bits are stored in the
+ * master pointer, which does not need to be preserved. */
+static void limit_mt_compat_from_user(void *dst, const void *src)
+{
+ const struct compat_xt_rateinfo *cm = src;
+ struct xt_rateinfo m = {
+ .avg = cm->avg,
+ .burst = cm->burst,
+ .prev = cm->prev | (unsigned long)cm->master << 32,
+ .credit = cm->credit,
+ .credit_cap = cm->credit_cap,
+ .cost = cm->cost,
+ };
+ memcpy(dst, &m, sizeof(m));
+}
+
+static int limit_mt_compat_to_user(void __user *dst, const void *src)
+{
+ const struct xt_rateinfo *m = src;
+ struct compat_xt_rateinfo cm = {
+ .avg = m->avg,
+ .burst = m->burst,
+ .prev = m->prev,
+ .credit = m->credit,
+ .credit_cap = m->credit_cap,
+ .cost = m->cost,
+ .master = m->prev >> 32,
+ };
+ return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
+}
+#endif /* CONFIG_COMPAT */
+
+static struct xt_match limit_mt_reg __read_mostly = {
+ .name = "limit",
+ .revision = 0,
+ .family = NFPROTO_UNSPEC,
+ .match = limit_mt,
+ .checkentry = limit_mt_check,
+ .destroy = limit_mt_destroy,
+ .matchsize = sizeof(struct xt_rateinfo),
+#ifdef CONFIG_COMPAT
+ .compatsize = sizeof(struct compat_xt_rateinfo),
+ .compat_from_user = limit_mt_compat_from_user,
+ .compat_to_user = limit_mt_compat_to_user,
+#endif
+ .me = THIS_MODULE,
+};
+
+static int __init limit_mt_init(void)
+{
+ return xt_register_match(&limit_mt_reg);
+}
+
+static void __exit limit_mt_exit(void)
+{
+ xt_unregister_match(&limit_mt_reg);
+}
+
+module_init(limit_mt_init);
+module_exit(limit_mt_exit);
Code Review / kvmfornfv.git / blobdiff