1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (c) 2016 Laura Garcia <nevola@gmail.com> 4 */ 5 6 #include <linux/kernel.h> 7 #include <linux/init.h> 8 #include <linux/module.h> 9 #include <linux/netlink.h> 10 #include <linux/netfilter.h> 11 #include <linux/netfilter/nf_tables.h> 12 #include <linux/static_key.h> 13 #include <net/netfilter/nf_tables.h> 14 #include <net/netfilter/nf_tables_core.h> 15 16 static DEFINE_PER_CPU(struct rnd_state, nft_numgen_prandom_state); 17 18 struct nft_ng_inc { 19 u8 dreg; 20 u32 modulus; 21 atomic_t counter; 22 u32 offset; 23 }; 24 25 static u32 nft_ng_inc_gen(struct nft_ng_inc *priv) 26 { 27 u32 nval, oval; 28 29 do { 30 oval = atomic_read(&priv->counter); 31 nval = (oval + 1 < priv->modulus) ? oval + 1 : 0; 32 } while (atomic_cmpxchg(&priv->counter, oval, nval) != oval); 33 34 return nval + priv->offset; 35 } 36 37 static void nft_ng_inc_eval(const struct nft_expr *expr, 38 struct nft_regs *regs, 39 const struct nft_pktinfo *pkt) 40 { 41 struct nft_ng_inc *priv = nft_expr_priv(expr); 42 43 regs->data[priv->dreg] = nft_ng_inc_gen(priv); 44 } 45 46 static const struct nla_policy nft_ng_policy[NFTA_NG_MAX + 1] = { 47 [NFTA_NG_DREG] = { .type = NLA_U32 }, 48 [NFTA_NG_MODULUS] = { .type = NLA_U32 }, 49 [NFTA_NG_TYPE] = { .type = NLA_U32 }, 50 [NFTA_NG_OFFSET] = { .type = NLA_U32 }, 51 }; 52 53 static int nft_ng_inc_init(const struct nft_ctx *ctx, 54 const struct nft_expr *expr, 55 const struct nlattr * const tb[]) 56 { 57 struct nft_ng_inc *priv = nft_expr_priv(expr); 58 59 if (tb[NFTA_NG_OFFSET]) 60 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET])); 61 62 priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS])); 63 if (priv->modulus == 0) 64 return -ERANGE; 65 66 if (priv->offset + priv->modulus - 1 < priv->offset) 67 return -EOVERFLOW; 68 69 atomic_set(&priv->counter, priv->modulus - 1); 70 71 return nft_parse_register_store(ctx, tb[NFTA_NG_DREG], &priv->dreg, 72 NULL, NFT_DATA_VALUE, sizeof(u32)); 73 } 74 75 static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg, 76 u32 modulus, enum nft_ng_types type, u32 offset) 77 { 78 if (nft_dump_register(skb, NFTA_NG_DREG, dreg)) 79 goto nla_put_failure; 80 if (nla_put_be32(skb, NFTA_NG_MODULUS, htonl(modulus))) 81 goto nla_put_failure; 82 if (nla_put_be32(skb, NFTA_NG_TYPE, htonl(type))) 83 goto nla_put_failure; 84 if (nla_put_be32(skb, NFTA_NG_OFFSET, htonl(offset))) 85 goto nla_put_failure; 86 87 return 0; 88 89 nla_put_failure: 90 return -1; 91 } 92 93 static int nft_ng_inc_dump(struct sk_buff *skb, const struct nft_expr *expr) 94 { 95 const struct nft_ng_inc *priv = nft_expr_priv(expr); 96 97 return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_INCREMENTAL, 98 priv->offset); 99 } 100 101 struct nft_ng_random { 102 u8 dreg; 103 u32 modulus; 104 u32 offset; 105 }; 106 107 static u32 nft_ng_random_gen(struct nft_ng_random *priv) 108 { 109 struct rnd_state *state = this_cpu_ptr(&nft_numgen_prandom_state); 110 111 return reciprocal_scale(prandom_u32_state(state), priv->modulus) + 112 priv->offset; 113 } 114 115 static void nft_ng_random_eval(const struct nft_expr *expr, 116 struct nft_regs *regs, 117 const struct nft_pktinfo *pkt) 118 { 119 struct nft_ng_random *priv = nft_expr_priv(expr); 120 121 regs->data[priv->dreg] = nft_ng_random_gen(priv); 122 } 123 124 static int nft_ng_random_init(const struct nft_ctx *ctx, 125 const struct nft_expr *expr, 126 const struct nlattr * const tb[]) 127 { 128 struct nft_ng_random *priv = nft_expr_priv(expr); 129 130 if (tb[NFTA_NG_OFFSET]) 131 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET])); 132 133 priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS])); 134 if (priv->modulus == 0) 135 return -ERANGE; 136 137 if (priv->offset + priv->modulus - 1 < priv->offset) 138 return -EOVERFLOW; 139 140 prandom_init_once(&nft_numgen_prandom_state); 141 142 return nft_parse_register_store(ctx, tb[NFTA_NG_DREG], &priv->dreg, 143 NULL, NFT_DATA_VALUE, sizeof(u32)); 144 } 145 146 static int nft_ng_random_dump(struct sk_buff *skb, const struct nft_expr *expr) 147 { 148 const struct nft_ng_random *priv = nft_expr_priv(expr); 149 150 return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_RANDOM, 151 priv->offset); 152 } 153 154 static struct nft_expr_type nft_ng_type; 155 static const struct nft_expr_ops nft_ng_inc_ops = { 156 .type = &nft_ng_type, 157 .size = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)), 158 .eval = nft_ng_inc_eval, 159 .init = nft_ng_inc_init, 160 .dump = nft_ng_inc_dump, 161 }; 162 163 static const struct nft_expr_ops nft_ng_random_ops = { 164 .type = &nft_ng_type, 165 .size = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)), 166 .eval = nft_ng_random_eval, 167 .init = nft_ng_random_init, 168 .dump = nft_ng_random_dump, 169 }; 170 171 static const struct nft_expr_ops * 172 nft_ng_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[]) 173 { 174 u32 type; 175 176 if (!tb[NFTA_NG_DREG] || 177 !tb[NFTA_NG_MODULUS] || 178 !tb[NFTA_NG_TYPE]) 179 return ERR_PTR(-EINVAL); 180 181 type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE])); 182 183 switch (type) { 184 case NFT_NG_INCREMENTAL: 185 return &nft_ng_inc_ops; 186 case NFT_NG_RANDOM: 187 return &nft_ng_random_ops; 188 } 189 190 return ERR_PTR(-EINVAL); 191 } 192 193 static struct nft_expr_type nft_ng_type __read_mostly = { 194 .name = "numgen", 195 .select_ops = nft_ng_select_ops, 196 .policy = nft_ng_policy, 197 .maxattr = NFTA_NG_MAX, 198 .owner = THIS_MODULE, 199 }; 200 201 static int __init nft_ng_module_init(void) 202 { 203 return nft_register_expr(&nft_ng_type); 204 } 205 206 static void __exit nft_ng_module_exit(void) 207 { 208 nft_unregister_expr(&nft_ng_type); 209 } 210 211 module_init(nft_ng_module_init); 212 module_exit(nft_ng_module_exit); 213 214 MODULE_LICENSE("GPL"); 215 MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>"); 216 MODULE_ALIAS_NFT_EXPR("numgen"); 217 MODULE_DESCRIPTION("nftables number generator module"); 218