| 1 | |
| 2 | |
| 3 | * Copyright (c) 2006 Patrick McHardy <[email protected]>
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| 4 | *
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| 5 | * Based on ipt_random and ipt_nth by Fabrice MARIE <[email protected]>.
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| 6 |
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| 7 |
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| 8 | #include <linux/init.h>
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| 9 | #include <linux/spinlock.h>
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| 10 | #include <linux/skbuff.h>
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| 11 | #include <linux/net.h>
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| 12 | #include <linux/slab.h>
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| 13 |
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| 14 | #include <linux/netfilter/xt_statistic.h>
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| 15 | #include <linux/netfilter/x_tables.h>
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| 16 | #include <linux/module.h>
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| 17 |
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| 18 | struct xt_statistic_priv {
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| 19 | atomic_t count;
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| 20 | } ____cacheline_aligned_in_smp;
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| 21 |
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| 22 | MODULE_LICENSE("GPL");
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| 23 | MODULE_AUTHOR("Patrick McHardy <[email protected]>");
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| 24 | MODULE_DESCRIPTION("Xtables: statistics-based matching (\"Nth\", random)");
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| 25 | MODULE_ALIAS("ipt_statistic");
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| 26 | MODULE_ALIAS("ip6t_statistic");
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| 27 |
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| 28 | static bool
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| 29 | statistic_mt(const struct sk_buff *skb, struct xt_action_param *par)
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| 30 | {
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| 31 | const struct xt_statistic_info *info = par->matchinfo;
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| 32 | bool ret = info->flags & XT_STATISTIC_INVERT;
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| 33 | int nval, oval;
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| 34 |
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| 35 | switch (info->mode) {
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| 36 | case XT_STATISTIC_MODE_RANDOM:
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| 37 | if ((get_random_u32() & 0x7FFFFFFF) < info->u.random.probability)
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| 38 | ret = !ret;
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| 39 | break;
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| 40 | case XT_STATISTIC_MODE_NTH:
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| 41 | do {
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| 42 | oval = atomic_read(&info->master->count);
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| 43 | nval = (oval == info->u.nth.every) ? 0 : oval + 1;
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| 44 | } while (atomic_cmpxchg(&info->master->count, oval, nval) != oval);
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| 45 | if (nval == 0)
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| 46 | ret = !ret;
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| 47 | break;
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| 48 | }
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| 49 |
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| 50 | return ret;
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| 51 | }
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| 52 |
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| 53 | static int statistic_mt_check(const struct xt_mtchk_param *par)
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| 54 | {
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| 55 | struct xt_statistic_info *info = par->matchinfo;
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| 56 |
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| 57 | if (info->mode > XT_STATISTIC_MODE_MAX ||
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| 58 | info->flags & ~XT_STATISTIC_MASK)
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| 59 | return -EINVAL;
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| 60 |
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| 61 | info->master = kzalloc_obj(*info->master);
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| 62 | if (info->master == NULL)
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| 63 | return -ENOMEM;
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| 64 | atomic_set(&info->master->count, info->u.nth.count);
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| 65 |
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| 66 | return 0;
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| 67 | }
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| 68 |
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| 69 | static void statistic_mt_destroy(const struct xt_mtdtor_param *par)
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| 70 | {
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| 71 | const struct xt_statistic_info *info = par->matchinfo;
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| 72 |
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| 73 | kfree(info->master);
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| 74 | }
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| 75 |
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| 76 | static struct xt_match xt_statistic_mt_reg __read_mostly = {
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| 77 | .name = "statistic",
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| 78 | .revision = 0,
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| 79 | .family = NFPROTO_UNSPEC,
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| 80 | .match = statistic_mt,
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| 81 | .checkentry = statistic_mt_check,
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| 82 | .destroy = statistic_mt_destroy,
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| 83 | .matchsize = sizeof(struct xt_statistic_info),
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| 84 | .usersize = offsetof(struct xt_statistic_info, master),
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| 85 | .me = THIS_MODULE,
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| 86 | };
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| 87 |
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| 88 | static int __init statistic_mt_init(void)
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| 89 | {
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| 90 | return xt_register_match(&xt_statistic_mt_reg);
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| 91 | }
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| 92 |
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| 93 | static void __exit statistic_mt_exit(void)
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| 94 | {
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| 95 | xt_unregister_match(&xt_statistic_mt_reg);
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| 96 | }
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| 97 |
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| 98 | module_init(statistic_mt_init);
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| 99 | module_exit(statistic_mt_exit);
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