LXR linux/net/bridge/netfilter/ebt

   1/*
   2 *  ebt_limit
   3 *
   4 *      Authors:
   5 *      Tom Marshall <tommy@home.tig-grr.com>
   6 *
   7 *      Mostly copied from netfilter's ipt_limit.c, see that file for
   8 *      more explanation
   9 *
  10 *  September, 2003
  11 *
  12 */
  13#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  14#include <linux/module.h>
  15#include <linux/netdevice.h>
  16#include <linux/spinlock.h>
  17#include <linux/netfilter/x_tables.h>
  18#include <linux/netfilter_bridge/ebtables.h>
  19#include <linux/netfilter_bridge/ebt_limit.h>
  20
  21static DEFINE_SPINLOCK(limit_lock);
  22
  23#define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))
  24
  25#define _POW2_BELOW2(x) ((x)|((x)>>1))
  26#define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2))
  27#define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4))
  28#define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8))
  29#define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16))
  30#define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1)
  31
  32#define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ)
  33
  34static bool
  35ebt_limit_mt(const struct sk_buff *skb, struct xt_action_param *par)
  36{
  37        struct ebt_limit_info *info = (void *)par->matchinfo;
  38        unsigned long now = jiffies;
  39
  40        spin_lock_bh(&limit_lock);
  41        info->credit += (now - xchg(&info->prev, now)) * CREDITS_PER_JIFFY;
  42        if (info->credit > info->credit_cap)
  43                info->credit = info->credit_cap;
  44
  45        if (info->credit >= info->cost) {
  46                /* We're not limited. */
  47                info->credit -= info->cost;
  48                spin_unlock_bh(&limit_lock);
  49                return true;
  50        }
  51
  52        spin_unlock_bh(&limit_lock);
  53        return false;
  54}
  55
  56/* Precision saver. */
  57static u_int32_t
  58user2credits(u_int32_t user)
  59{
  60        /* If multiplying would overflow... */
  61        if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
  62                /* Divide first. */
  63                return (user / EBT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;
  64
  65        return (user * HZ * CREDITS_PER_JIFFY) / EBT_LIMIT_SCALE;
  66}
  67
  68static int ebt_limit_mt_check(const struct xt_mtchk_param *par)
  69{
  70        struct ebt_limit_info *info = par->matchinfo;
  71
  72        /* Check for overflow. */
  73        if (info->burst == 0 ||
  74            user2credits(info->avg * info->burst) < user2credits(info->avg)) {
  75                pr_info_ratelimited("overflow, try lower: %u/%u\n",
  76                                    info->avg, info->burst);
  77                return -EINVAL;
  78        }
  79
  80        /* User avg in seconds * EBT_LIMIT_SCALE: convert to jiffies * 128. */
  81        info->prev = jiffies;
  82        info->credit = user2credits(info->avg * info->burst);
  83        info->credit_cap = user2credits(info->avg * info->burst);
  84        info->cost = user2credits(info->avg);
  85        return 0;
  86}
  87
  88
  89#ifdef CONFIG_COMPAT
  90/*
  91 * no conversion function needed --
  92 * only avg/burst have meaningful values in userspace.
  93 */
  94struct ebt_compat_limit_info {
  95        compat_uint_t avg, burst;
  96        compat_ulong_t prev;
  97        compat_uint_t credit, credit_cap, cost;
  98};
  99#endif
 100
 101static struct xt_match ebt_limit_mt_reg __read_mostly = {
 102        .name           = "limit",
 103        .revision       = 0,
 104        .family         = NFPROTO_BRIDGE,
 105        .match          = ebt_limit_mt,
 106        .checkentry     = ebt_limit_mt_check,
 107        .matchsize      = sizeof(struct ebt_limit_info),
 108        .usersize       = offsetof(struct ebt_limit_info, prev),
 109#ifdef CONFIG_COMPAT
 110        .compatsize     = sizeof(struct ebt_compat_limit_info),
 111#endif
 112        .me             = THIS_MODULE,
 113};
 114
 115static int __init ebt_limit_init(void)
 116{
 117        return xt_register_match(&ebt_limit_mt_reg);
 118}
 119
 120static void __exit ebt_limit_fini(void)
 121{
 122        xt_unregister_match(&ebt_limit_mt_reg);
 123}
 124
 125module_init(ebt_limit_init);
 126module_exit(ebt_limit_fini);
 127MODULE_DESCRIPTION("Ebtables: Rate-limit match");
 128MODULE_LICENSE("GPL");
 129