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 21 static 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 34 static bool 35 ebt_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. */ 57 static u_int32_t 58 user2credits(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 68 static 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("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 */ 94 struct 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 100 101 static 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 #ifdef CONFIG_COMPAT 109 .compatsize = sizeof(struct ebt_compat_limit_info), 110 #endif 111 .me = THIS_MODULE, 112 }; 113 114 static int __init ebt_limit_init(void) 115 { 116 return xt_register_match(&ebt_limit_mt_reg); 117 } 118 119 static void __exit ebt_limit_fini(void) 120 { 121 xt_unregister_match(&ebt_limit_mt_reg); 122 } 123 124 module_init(ebt_limit_init); 125 module_exit(ebt_limit_fini); 126 MODULE_DESCRIPTION("Ebtables: Rate-limit match"); 127 MODULE_LICENSE("GPL"); 128