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/random.h> 13 #include <linux/static_key.h> 14 #include <net/netfilter/nf_tables.h> 15 #include <net/netfilter/nf_tables_core.h> 16 17 struct nft_ng_inc { 18 u8 dreg; 19 u32 modulus; 20 atomic_t *counter; 21 u32 offset; 22 }; 23 24 static u32 nft_ng_inc_gen(struct nft_ng_inc *priv) 25 { 26 u32 nval, oval; 27 28 do { 29 oval = atomic_read(priv->counter); 30 nval = (oval + 1 < priv->modulus) ? oval + 1 : 0; 31 } while (atomic_cmpxchg(priv->counter, oval, nval) != oval); 32 33 return nval + priv->offset; 34 } 35 36 static void nft_ng_inc_eval(const struct nft_expr *expr, 37 struct nft_regs *regs, 38 const struct nft_pktinfo *pkt) 39 { 40 struct nft_ng_inc *priv = nft_expr_priv(expr); 41 42 regs->data[priv->dreg] = nft_ng_inc_gen(priv); 43 } 44 45 static const struct nla_policy nft_ng_policy[NFTA_NG_MAX + 1] = { 46 [NFTA_NG_DREG] = { .type = NLA_U32 }, 47 [NFTA_NG_MODULUS] = { .type = NLA_U32 }, 48 [NFTA_NG_TYPE] = { .type = NLA_U32 }, 49 [NFTA_NG_OFFSET] = { .type = NLA_U32 }, 50 }; 51 52 static int nft_ng_inc_init(const struct nft_ctx *ctx, 53 const struct nft_expr *expr, 54 const struct nlattr * const tb[]) 55 { 56 struct nft_ng_inc *priv = nft_expr_priv(expr); 57 int err; 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 priv->counter = kmalloc(sizeof(*priv->counter), GFP_KERNEL); 70 if (!priv->counter) 71 return -ENOMEM; 72 73 atomic_set(priv->counter, priv->modulus - 1); 74 75 err = nft_parse_register_store(ctx, tb[NFTA_NG_DREG], &priv->dreg, 76 NULL, NFT_DATA_VALUE, sizeof(u32)); 77 if (err < 0) 78 goto err; 79 80 return 0; 81 err: 82 kfree(priv->counter); 83 84 return err; 85 } 86 87 static bool nft_ng_inc_reduce(struct nft_regs_track *track, 88 const struct nft_expr *expr) 89 { 90 const struct nft_ng_inc *priv = nft_expr_priv(expr); 91 92 nft_reg_track_cancel(track, priv->dreg, NFT_REG32_SIZE); 93 94 return false; 95 } 96 97 static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg, 98 u32 modulus, enum nft_ng_types type, u32 offset) 99 { 100 if (nft_dump_register(skb, NFTA_NG_DREG, dreg)) 101 goto nla_put_failure; 102 if (nla_put_be32(skb, NFTA_NG_MODULUS, htonl(modulus))) 103 goto nla_put_failure; 104 if (nla_put_be32(skb, NFTA_NG_TYPE, htonl(type))) 105 goto nla_put_failure; 106 if (nla_put_be32(skb, NFTA_NG_OFFSET, htonl(offset))) 107 goto nla_put_failure; 108 109 return 0; 110 111 nla_put_failure: 112 return -1; 113 } 114 115 static int nft_ng_inc_dump(struct sk_buff *skb, 116 const struct nft_expr *expr, bool reset) 117 { 118 const struct nft_ng_inc *priv = nft_expr_priv(expr); 119 120 return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_INCREMENTAL, 121 priv->offset); 122 } 123 124 static void nft_ng_inc_destroy(const struct nft_ctx *ctx, 125 const struct nft_expr *expr) 126 { 127 const struct nft_ng_inc *priv = nft_expr_priv(expr); 128 129 kfree(priv->counter); 130 } 131 132 struct nft_ng_random { 133 u8 dreg; 134 u32 modulus; 135 u32 offset; 136 }; 137 138 static u32 nft_ng_random_gen(const struct nft_ng_random *priv) 139 { 140 return reciprocal_scale(get_random_u32(), priv->modulus) + priv->offset; 141 } 142 143 static void nft_ng_random_eval(const struct nft_expr *expr, 144 struct nft_regs *regs, 145 const struct nft_pktinfo *pkt) 146 { 147 struct nft_ng_random *priv = nft_expr_priv(expr); 148 149 regs->data[priv->dreg] = nft_ng_random_gen(priv); 150 } 151 152 static int nft_ng_random_init(const struct nft_ctx *ctx, 153 const struct nft_expr *expr, 154 const struct nlattr * const tb[]) 155 { 156 struct nft_ng_random *priv = nft_expr_priv(expr); 157 158 if (tb[NFTA_NG_OFFSET]) 159 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET])); 160 161 priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS])); 162 if (priv->modulus == 0) 163 return -ERANGE; 164 165 if (priv->offset + priv->modulus - 1 < priv->offset) 166 return -EOVERFLOW; 167 168 return nft_parse_register_store(ctx, tb[NFTA_NG_DREG], &priv->dreg, 169 NULL, NFT_DATA_VALUE, sizeof(u32)); 170 } 171 172 static int nft_ng_random_dump(struct sk_buff *skb, 173 const struct nft_expr *expr, bool reset) 174 { 175 const struct nft_ng_random *priv = nft_expr_priv(expr); 176 177 return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_RANDOM, 178 priv->offset); 179 } 180 181 static bool nft_ng_random_reduce(struct nft_regs_track *track, 182 const struct nft_expr *expr) 183 { 184 const struct nft_ng_random *priv = nft_expr_priv(expr); 185 186 nft_reg_track_cancel(track, priv->dreg, NFT_REG32_SIZE); 187 188 return false; 189 } 190 191 static struct nft_expr_type nft_ng_type; 192 static const struct nft_expr_ops nft_ng_inc_ops = { 193 .type = &nft_ng_type, 194 .size = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)), 195 .eval = nft_ng_inc_eval, 196 .init = nft_ng_inc_init, 197 .destroy = nft_ng_inc_destroy, 198 .dump = nft_ng_inc_dump, 199 .reduce = nft_ng_inc_reduce, 200 }; 201 202 static const struct nft_expr_ops nft_ng_random_ops = { 203 .type = &nft_ng_type, 204 .size = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)), 205 .eval = nft_ng_random_eval, 206 .init = nft_ng_random_init, 207 .dump = nft_ng_random_dump, 208 .reduce = nft_ng_random_reduce, 209 }; 210 211 static const struct nft_expr_ops * 212 nft_ng_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[]) 213 { 214 u32 type; 215 216 if (!tb[NFTA_NG_DREG] || 217 !tb[NFTA_NG_MODULUS] || 218 !tb[NFTA_NG_TYPE]) 219 return ERR_PTR(-EINVAL); 220 221 type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE])); 222 223 switch (type) { 224 case NFT_NG_INCREMENTAL: 225 return &nft_ng_inc_ops; 226 case NFT_NG_RANDOM: 227 return &nft_ng_random_ops; 228 } 229 230 return ERR_PTR(-EINVAL); 231 } 232 233 static struct nft_expr_type nft_ng_type __read_mostly = { 234 .name = "numgen", 235 .select_ops = nft_ng_select_ops, 236 .policy = nft_ng_policy, 237 .maxattr = NFTA_NG_MAX, 238 .owner = THIS_MODULE, 239 }; 240 241 static int __init nft_ng_module_init(void) 242 { 243 return nft_register_expr(&nft_ng_type); 244 } 245 246 static void __exit nft_ng_module_exit(void) 247 { 248 nft_unregister_expr(&nft_ng_type); 249 } 250 251 module_init(nft_ng_module_init); 252 module_exit(nft_ng_module_exit); 253 254 MODULE_LICENSE("GPL"); 255 MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>"); 256 MODULE_ALIAS_NFT_EXPR("numgen"); 257 MODULE_DESCRIPTION("nftables number generator module"); 258