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 #include <linux/module.h> 20 21 struct xt_statistic_priv { 22 atomic_t count; 23 } ____cacheline_aligned_in_smp; 24 25 MODULE_LICENSE("GPL"); 26 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>"); 27 MODULE_DESCRIPTION("Xtables: statistics-based matching (\"Nth\", random)"); 28 MODULE_ALIAS("ipt_statistic"); 29 MODULE_ALIAS("ip6t_statistic"); 30 31 static bool 32 statistic_mt(const struct sk_buff *skb, struct xt_action_param *par) 33 { 34 const struct xt_statistic_info *info = par->matchinfo; 35 bool ret = info->flags & XT_STATISTIC_INVERT; 36 int nval, oval; 37 38 switch (info->mode) { 39 case XT_STATISTIC_MODE_RANDOM: 40 if ((prandom_u32() & 0x7FFFFFFF) < info->u.random.probability) 41 ret = !ret; 42 break; 43 case XT_STATISTIC_MODE_NTH: 44 do { 45 oval = atomic_read(&info->master->count); 46 nval = (oval == info->u.nth.every) ? 0 : oval + 1; 47 } while (atomic_cmpxchg(&info->master->count, oval, nval) != oval); 48 if (nval == 0) 49 ret = !ret; 50 break; 51 } 52 53 return ret; 54 } 55 56 static int statistic_mt_check(const struct xt_mtchk_param *par) 57 { 58 struct xt_statistic_info *info = par->matchinfo; 59 60 if (info->mode > XT_STATISTIC_MODE_MAX || 61 info->flags & ~XT_STATISTIC_MASK) 62 return -EINVAL; 63 64 info->master = kzalloc(sizeof(*info->master), GFP_KERNEL); 65 if (info->master == NULL) 66 return -ENOMEM; 67 atomic_set(&info->master->count, info->u.nth.count); 68 69 return 0; 70 } 71 72 static void statistic_mt_destroy(const struct xt_mtdtor_param *par) 73 { 74 const struct xt_statistic_info *info = par->matchinfo; 75 76 kfree(info->master); 77 } 78 79 static struct xt_match xt_statistic_mt_reg __read_mostly = { 80 .name = "statistic", 81 .revision = 0, 82 .family = NFPROTO_UNSPEC, 83 .match = statistic_mt, 84 .checkentry = statistic_mt_check, 85 .destroy = statistic_mt_destroy, 86 .matchsize = sizeof(struct xt_statistic_info), 87 .me = THIS_MODULE, 88 }; 89 90 static int __init statistic_mt_init(void) 91 { 92 return xt_register_match(&xt_statistic_mt_reg); 93 } 94 95 static void __exit statistic_mt_exit(void) 96 { 97 xt_unregister_match(&xt_statistic_mt_reg); 98 } 99 100 module_init(statistic_mt_init); 101 module_exit(statistic_mt_exit); 102