cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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ebt_limit.c (3393B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 *  ebt_limit
      4 *
      5 *	Authors:
      6 *	Tom Marshall <tommy@home.tig-grr.com>
      7 *
      8 *	Mostly copied from netfilter's ipt_limit.c, see that file for
      9 *	more explanation
     10 *
     11 *  September, 2003
     12 *
     13 */
     14#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
     15#include <linux/module.h>
     16#include <linux/netdevice.h>
     17#include <linux/spinlock.h>
     18#include <linux/netfilter/x_tables.h>
     19#include <linux/netfilter_bridge/ebtables.h>
     20#include <linux/netfilter_bridge/ebt_limit.h>
     21
     22static DEFINE_SPINLOCK(limit_lock);
     23
     24#define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))
     25
     26#define _POW2_BELOW2(x) ((x)|((x)>>1))
     27#define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2))
     28#define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4))
     29#define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8))
     30#define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16))
     31#define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1)
     32
     33#define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ)
     34
     35static bool
     36ebt_limit_mt(const struct sk_buff *skb, struct xt_action_param *par)
     37{
     38	struct ebt_limit_info *info = (void *)par->matchinfo;
     39	unsigned long now = jiffies;
     40
     41	spin_lock_bh(&limit_lock);
     42	info->credit += (now - xchg(&info->prev, now)) * CREDITS_PER_JIFFY;
     43	if (info->credit > info->credit_cap)
     44		info->credit = info->credit_cap;
     45
     46	if (info->credit >= info->cost) {
     47		/* We're not limited. */
     48		info->credit -= info->cost;
     49		spin_unlock_bh(&limit_lock);
     50		return true;
     51	}
     52
     53	spin_unlock_bh(&limit_lock);
     54	return false;
     55}
     56
     57/* Precision saver. */
     58static u_int32_t
     59user2credits(u_int32_t user)
     60{
     61	/* If multiplying would overflow... */
     62	if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
     63		/* Divide first. */
     64		return (user / EBT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;
     65
     66	return (user * HZ * CREDITS_PER_JIFFY) / EBT_LIMIT_SCALE;
     67}
     68
     69static int ebt_limit_mt_check(const struct xt_mtchk_param *par)
     70{
     71	struct ebt_limit_info *info = par->matchinfo;
     72
     73	/* Check for overflow. */
     74	if (info->burst == 0 ||
     75	    user2credits(info->avg * info->burst) < user2credits(info->avg)) {
     76		pr_info_ratelimited("overflow, try lower: %u/%u\n",
     77				    info->avg, info->burst);
     78		return -EINVAL;
     79	}
     80
     81	/* User avg in seconds * EBT_LIMIT_SCALE: convert to jiffies * 128. */
     82	info->prev = jiffies;
     83	info->credit = user2credits(info->avg * info->burst);
     84	info->credit_cap = user2credits(info->avg * info->burst);
     85	info->cost = user2credits(info->avg);
     86	return 0;
     87}
     88
     89
     90#ifdef CONFIG_NETFILTER_XTABLES_COMPAT
     91/*
     92 * no conversion function needed --
     93 * only avg/burst have meaningful values in userspace.
     94 */
     95struct ebt_compat_limit_info {
     96	compat_uint_t avg, burst;
     97	compat_ulong_t prev;
     98	compat_uint_t credit, credit_cap, cost;
     99};
    100#endif
    101
    102static struct xt_match ebt_limit_mt_reg __read_mostly = {
    103	.name		= "limit",
    104	.revision	= 0,
    105	.family		= NFPROTO_BRIDGE,
    106	.match		= ebt_limit_mt,
    107	.checkentry	= ebt_limit_mt_check,
    108	.matchsize	= sizeof(struct ebt_limit_info),
    109	.usersize	= offsetof(struct ebt_limit_info, prev),
    110#ifdef CONFIG_NETFILTER_XTABLES_COMPAT
    111	.compatsize	= sizeof(struct ebt_compat_limit_info),
    112#endif
    113	.me		= THIS_MODULE,
    114};
    115
    116static int __init ebt_limit_init(void)
    117{
    118	return xt_register_match(&ebt_limit_mt_reg);
    119}
    120
    121static void __exit ebt_limit_fini(void)
    122{
    123	xt_unregister_match(&ebt_limit_mt_reg);
    124}
    125
    126module_init(ebt_limit_init);
    127module_exit(ebt_limit_fini);
    128MODULE_DESCRIPTION("Ebtables: Rate-limit match");
    129MODULE_LICENSE("GPL");