1 /* 2 * Copyright (c) 2016 Laura Garcia <nevola@gmail.com> 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 */ 9 10 #include <linux/kernel.h> 11 #include <linux/init.h> 12 #include <linux/module.h> 13 #include <linux/netlink.h> 14 #include <linux/netfilter.h> 15 #include <linux/netfilter/nf_tables.h> 16 #include <linux/static_key.h> 17 #include <net/netfilter/nf_tables.h> 18 #include <net/netfilter/nf_tables_core.h> 19 20 static DEFINE_PER_CPU(struct rnd_state, nft_numgen_prandom_state); 21 22 struct nft_ng_inc { 23 enum nft_registers dreg:8; 24 u32 modulus; 25 atomic_t counter; 26 u32 offset; 27 }; 28 29 static u32 nft_ng_inc_gen(struct nft_ng_inc *priv) 30 { 31 u32 nval, oval; 32 33 do { 34 oval = atomic_read(&priv->counter); 35 nval = (oval + 1 < priv->modulus) ? oval + 1 : 0; 36 } while (atomic_cmpxchg(&priv->counter, oval, nval) != oval); 37 38 return nval + priv->offset; 39 } 40 41 static void nft_ng_inc_eval(const struct nft_expr *expr, 42 struct nft_regs *regs, 43 const struct nft_pktinfo *pkt) 44 { 45 struct nft_ng_inc *priv = nft_expr_priv(expr); 46 47 regs->data[priv->dreg] = nft_ng_inc_gen(priv); 48 } 49 50 static const struct nla_policy nft_ng_policy[NFTA_NG_MAX + 1] = { 51 [NFTA_NG_DREG] = { .type = NLA_U32 }, 52 [NFTA_NG_MODULUS] = { .type = NLA_U32 }, 53 [NFTA_NG_TYPE] = { .type = NLA_U32 }, 54 [NFTA_NG_OFFSET] = { .type = NLA_U32 }, 55 }; 56 57 static int nft_ng_inc_init(const struct nft_ctx *ctx, 58 const struct nft_expr *expr, 59 const struct nlattr * const tb[]) 60 { 61 struct nft_ng_inc *priv = nft_expr_priv(expr); 62 63 if (tb[NFTA_NG_OFFSET]) 64 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET])); 65 66 priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS])); 67 if (priv->modulus == 0) 68 return -ERANGE; 69 70 if (priv->offset + priv->modulus - 1 < priv->offset) 71 return -EOVERFLOW; 72 73 priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]); 74 atomic_set(&priv->counter, priv->modulus - 1); 75 76 return nft_validate_register_store(ctx, priv->dreg, NULL, 77 NFT_DATA_VALUE, sizeof(u32)); 78 } 79 80 static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg, 81 u32 modulus, enum nft_ng_types type, u32 offset) 82 { 83 if (nft_dump_register(skb, NFTA_NG_DREG, dreg)) 84 goto nla_put_failure; 85 if (nla_put_be32(skb, NFTA_NG_MODULUS, htonl(modulus))) 86 goto nla_put_failure; 87 if (nla_put_be32(skb, NFTA_NG_TYPE, htonl(type))) 88 goto nla_put_failure; 89 if (nla_put_be32(skb, NFTA_NG_OFFSET, htonl(offset))) 90 goto nla_put_failure; 91 92 return 0; 93 94 nla_put_failure: 95 return -1; 96 } 97 98 static int nft_ng_inc_dump(struct sk_buff *skb, const struct nft_expr *expr) 99 { 100 const struct nft_ng_inc *priv = nft_expr_priv(expr); 101 102 return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_INCREMENTAL, 103 priv->offset); 104 } 105 106 struct nft_ng_random { 107 enum nft_registers dreg:8; 108 u32 modulus; 109 u32 offset; 110 }; 111 112 static u32 nft_ng_random_gen(struct nft_ng_random *priv) 113 { 114 struct rnd_state *state = this_cpu_ptr(&nft_numgen_prandom_state); 115 116 return reciprocal_scale(prandom_u32_state(state), priv->modulus) + 117 priv->offset; 118 } 119 120 static void nft_ng_random_eval(const struct nft_expr *expr, 121 struct nft_regs *regs, 122 const struct nft_pktinfo *pkt) 123 { 124 struct nft_ng_random *priv = nft_expr_priv(expr); 125 126 regs->data[priv->dreg] = nft_ng_random_gen(priv); 127 } 128 129 static int nft_ng_random_init(const struct nft_ctx *ctx, 130 const struct nft_expr *expr, 131 const struct nlattr * const tb[]) 132 { 133 struct nft_ng_random *priv = nft_expr_priv(expr); 134 135 if (tb[NFTA_NG_OFFSET]) 136 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET])); 137 138 priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS])); 139 if (priv->modulus == 0) 140 return -ERANGE; 141 142 if (priv->offset + priv->modulus - 1 < priv->offset) 143 return -EOVERFLOW; 144 145 prandom_init_once(&nft_numgen_prandom_state); 146 147 priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]); 148 149 return nft_validate_register_store(ctx, priv->dreg, NULL, 150 NFT_DATA_VALUE, sizeof(u32)); 151 } 152 153 static int nft_ng_random_dump(struct sk_buff *skb, const struct nft_expr *expr) 154 { 155 const struct nft_ng_random *priv = nft_expr_priv(expr); 156 157 return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_RANDOM, 158 priv->offset); 159 } 160 161 static struct nft_expr_type nft_ng_type; 162 static const struct nft_expr_ops nft_ng_inc_ops = { 163 .type = &nft_ng_type, 164 .size = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)), 165 .eval = nft_ng_inc_eval, 166 .init = nft_ng_inc_init, 167 .dump = nft_ng_inc_dump, 168 }; 169 170 static const struct nft_expr_ops nft_ng_random_ops = { 171 .type = &nft_ng_type, 172 .size = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)), 173 .eval = nft_ng_random_eval, 174 .init = nft_ng_random_init, 175 .dump = nft_ng_random_dump, 176 }; 177 178 static const struct nft_expr_ops * 179 nft_ng_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[]) 180 { 181 u32 type; 182 183 if (!tb[NFTA_NG_DREG] || 184 !tb[NFTA_NG_MODULUS] || 185 !tb[NFTA_NG_TYPE]) 186 return ERR_PTR(-EINVAL); 187 188 type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE])); 189 190 switch (type) { 191 case NFT_NG_INCREMENTAL: 192 return &nft_ng_inc_ops; 193 case NFT_NG_RANDOM: 194 return &nft_ng_random_ops; 195 } 196 197 return ERR_PTR(-EINVAL); 198 } 199 200 static struct nft_expr_type nft_ng_type __read_mostly = { 201 .name = "numgen", 202 .select_ops = nft_ng_select_ops, 203 .policy = nft_ng_policy, 204 .maxattr = NFTA_NG_MAX, 205 .owner = THIS_MODULE, 206 }; 207 208 static int __init nft_ng_module_init(void) 209 { 210 return nft_register_expr(&nft_ng_type); 211 } 212 213 static void __exit nft_ng_module_exit(void) 214 { 215 nft_unregister_expr(&nft_ng_type); 216 } 217 218 module_init(nft_ng_module_init); 219 module_exit(nft_ng_module_exit); 220 221 MODULE_LICENSE("GPL"); 222 MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>"); 223 MODULE_ALIAS_NFT_EXPR("numgen"); 224