| | 1 | /* |
| | 2 | * Copyright (c) 2006 Patrick McHardy <kaber@trash.net> |
| | 3 | * |
| | 4 | * This program is free software; you can redistribute it and/or modify |
| | 5 | * it under the terms of the GNU General Public License version 2 as |
| | 6 | * published by the Free Software Foundation. |
| | 7 | * |
| | 8 | * Based on ipt_random and ipt_nth by Fabrice MARIE <fabrice@netfilter.org>. |
| | 9 | */ |
| | 10 | |
| | 11 | #include <linux/init.h> |
| | 12 | #include <linux/spinlock.h> |
| | 13 | #include <linux/skbuff.h> |
| | 14 | #include <linux/net.h> |
| | 15 | #include <linux/slab.h> |
| | 16 | |
| | 17 | #include <linux/netfilter/xt_statistic.h> |
| | 18 | #include <linux/netfilter/x_tables.h> |
| | 19 | |
| | 20 | struct xt_statistic_priv { |
| | 21 | atomic_t count; |
| | 22 | } ____cacheline_aligned_in_smp; |
| | 23 | |
| | 24 | MODULE_LICENSE("GPL"); |
| | 25 | MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>"); |
| | 26 | MODULE_DESCRIPTION("Xtables: statistics-based matching (\"Nth\", random)"); |
| | 27 | MODULE_ALIAS("ipt_statistic"); |
| | 28 | MODULE_ALIAS("ip6t_statistic"); |
| | 29 | |
| | 30 | static bool |
| | 31 | statistic_mt(const struct sk_buff *skb, struct xt_action_param *par) |
| | 32 | { |
| | 33 | const struct xt_statistic_info *info = par->matchinfo; |
| | 34 | bool ret = info->flags & XT_STATISTIC_INVERT; |
| | 35 | int nval, oval; |
| | 36 | |
| | 37 | switch (info->mode) { |
| | 38 | case XT_STATISTIC_MODE_RANDOM: |
| | 39 | if ((net_random() & 0x7FFFFFFF) < info->u.random.probability) |
| | 40 | ret = !ret; |
| | 41 | break; |
| | 42 | case XT_STATISTIC_MODE_NTH: |
| | 43 | do { |
| | 44 | oval = atomic_read(&info->master->count); |
| | 45 | nval = (oval == info->u.nth.every) ? 0 : oval + 1; |
| | 46 | } while (atomic_cmpxchg(&info->master->count, oval, nval) != oval); |
| | 47 | if (nval == 0) |
| | 48 | ret = !ret; |
| | 49 | break; |
| | 50 | } |
| | 51 | |
| | 52 | return ret; |
| | 53 | } |
| | 54 | |
| | 55 | static int statistic_mt_check(const struct xt_mtchk_param *par) |
| | 56 | { |
| | 57 | struct xt_statistic_info *info = par->matchinfo; |
| | 58 | |
| | 59 | if (info->mode > XT_STATISTIC_MODE_MAX || |
| | 60 | info->flags & ~XT_STATISTIC_MASK) |
| | 61 | return -EINVAL; |
| | 62 | |
| | 63 | info->master = kzalloc(sizeof(*info->master), GFP_KERNEL); |
| | 64 | if (info->master == NULL) |
| | 65 | return -ENOMEM; |
| | 66 | atomic_set(&info->master->count, info->u.nth.count); |
| | 67 | |
| | 68 | return 0; |
| | 69 | } |
| | 70 | |
| | 71 | static void statistic_mt_destroy(const struct xt_mtdtor_param *par) |
| | 72 | { |
| | 73 | const struct xt_statistic_info *info = par->matchinfo; |
| | 74 | |
| | 75 | kfree(info->master); |
| | 76 | } |
| | 77 | |
| | 78 | static struct xt_match xt_statistic_mt_reg __read_mostly = { |
| | 79 | .name = "statistic", |
| | 80 | .revision = 0, |
| | 81 | .family = NFPROTO_UNSPEC, |
| | 82 | .match = statistic_mt, |
| | 83 | .checkentry = statistic_mt_check, |
| | 84 | .destroy = statistic_mt_destroy, |
| | 85 | .matchsize = sizeof(struct xt_statistic_info), |
| | 86 | .me = THIS_MODULE, |
| | 87 | }; |
| | 88 | |
| | 89 | static int __init statistic_mt_init(void) |
| | 90 | { |
| | 91 | return xt_register_match(&xt_statistic_mt_reg); |
| | 92 | } |
| | 93 | |
| | 94 | static void __exit statistic_mt_exit(void) |
| | 95 | { |
| | 96 | xt_unregister_match(&xt_statistic_mt_reg); |
| | 97 | } |
| | 98 | |
| | 99 | module_init(statistic_mt_init); |
| | 100 | module_exit(statistic_mt_exit); |
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