net/netfilter/nft_numgen.c

   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         struct nft_set          *map;
  28 };
  29
  30 static u32 nft_ng_inc_gen(struct nft_ng_inc *priv)
  31 {
  32         u32 nval, oval;
  33
  34         do {
  35                 oval = atomic_read(&priv->counter);
  36                 nval = (oval + 1 < priv->modulus) ? oval + 1 : 0;
  37         } while (atomic_cmpxchg(&priv->counter, oval, nval) != oval);
  38
  39         return nval + priv->offset;
  40 }
  41
  42 static void nft_ng_inc_eval(const struct nft_expr *expr,
  43                             struct nft_regs *regs,
  44                             const struct nft_pktinfo *pkt)
  45 {
  46         struct nft_ng_inc *priv = nft_expr_priv(expr);
  47
  48         regs->data[priv->dreg] = nft_ng_inc_gen(priv);
  49 }
  50
  51 static void nft_ng_inc_map_eval(const struct nft_expr *expr,
  52                                 struct nft_regs *regs,
  53                                 const struct nft_pktinfo *pkt)
  54 {
  55         struct nft_ng_inc *priv = nft_expr_priv(expr);
  56         const struct nft_set *map = priv->map;
  57         const struct nft_set_ext *ext;
  58         u32 result;
  59         bool found;
  60
  61         result = nft_ng_inc_gen(priv);
  62         found = map->ops->lookup(nft_net(pkt), map, &result, &ext);
  63
  64         if (!found)
  65                 return;
  66
  67         nft_data_copy(&regs->data[priv->dreg],
  68                       nft_set_ext_data(ext), map->dlen);
  69 }
  70
  71 static const struct nla_policy nft_ng_policy[NFTA_NG_MAX + 1] = {
  72         [NFTA_NG_DREG]          = { .type = NLA_U32 },
  73         [NFTA_NG_MODULUS]       = { .type = NLA_U32 },
  74         [NFTA_NG_TYPE]          = { .type = NLA_U32 },
  75         [NFTA_NG_OFFSET]        = { .type = NLA_U32 },
  76         [NFTA_NG_SET_NAME]      = { .type = NLA_STRING,
  77                                     .len = NFT_SET_MAXNAMELEN - 1 },
  78         [NFTA_NG_SET_ID]        = { .type = NLA_U32 },
  79 };
  80
  81 static int nft_ng_inc_init(const struct nft_ctx *ctx,
  82                            const struct nft_expr *expr,
  83                            const struct nlattr * const tb[])
  84 {
  85         struct nft_ng_inc *priv = nft_expr_priv(expr);
  86
  87         if (tb[NFTA_NG_OFFSET])
  88                 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
  89
  90         priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
  91         if (priv->modulus == 0)
  92                 return -ERANGE;
  93
  94         if (priv->offset + priv->modulus - 1 < priv->offset)
  95                 return -EOVERFLOW;
  96
  97         priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
  98         atomic_set(&priv->counter, priv->modulus - 1);
  99
 100         return nft_validate_register_store(ctx, priv->dreg, NULL,
 101                                            NFT_DATA_VALUE, sizeof(u32));
 102 }
 103
 104 static int nft_ng_inc_map_init(const struct nft_ctx *ctx,
 105                                const struct nft_expr *expr,
 106                                const struct nlattr * const tb[])
 107 {
 108         struct nft_ng_inc *priv = nft_expr_priv(expr);
 109         u8 genmask = nft_genmask_next(ctx->net);
 110
 111         nft_ng_inc_init(ctx, expr, tb);
 112
 113         priv->map = nft_set_lookup_global(ctx->net, ctx->table,
 114                                           tb[NFTA_NG_SET_NAME],
 115                                           tb[NFTA_NG_SET_ID], genmask);
 116
 117         return PTR_ERR_OR_ZERO(priv->map);
 118 }
 119
 120 static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg,
 121                        u32 modulus, enum nft_ng_types type, u32 offset)
 122 {
 123         if (nft_dump_register(skb, NFTA_NG_DREG, dreg))
 124                 goto nla_put_failure;
 125         if (nla_put_be32(skb, NFTA_NG_MODULUS, htonl(modulus)))
 126                 goto nla_put_failure;
 127         if (nla_put_be32(skb, NFTA_NG_TYPE, htonl(type)))
 128                 goto nla_put_failure;
 129         if (nla_put_be32(skb, NFTA_NG_OFFSET, htonl(offset)))
 130                 goto nla_put_failure;
 131
 132         return 0;
 133
 134 nla_put_failure:
 135         return -1;
 136 }
 137
 138 static int nft_ng_inc_dump(struct sk_buff *skb, const struct nft_expr *expr)
 139 {
 140         const struct nft_ng_inc *priv = nft_expr_priv(expr);
 141
 142         return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_INCREMENTAL,
 143                            priv->offset);
 144 }
 145
 146 static int nft_ng_inc_map_dump(struct sk_buff *skb,
 147                                const struct nft_expr *expr)
 148 {
 149         const struct nft_ng_inc *priv = nft_expr_priv(expr);
 150
 151         if (nft_ng_dump(skb, priv->dreg, priv->modulus,
 152                         NFT_NG_INCREMENTAL, priv->offset) ||
 153             nla_put_string(skb, NFTA_NG_SET_NAME, priv->map->name))
 154                 goto nla_put_failure;
 155
 156         return 0;
 157
 158 nla_put_failure:
 159         return -1;
 160 }
 161
 162 struct nft_ng_random {
 163         enum nft_registers      dreg:8;
 164         u32                     modulus;
 165         u32                     offset;
 166         struct nft_set          *map;
 167 };
 168
 169 static u32 nft_ng_random_gen(struct nft_ng_random *priv)
 170 {
 171         struct rnd_state *state = this_cpu_ptr(&nft_numgen_prandom_state);
 172
 173         return reciprocal_scale(prandom_u32_state(state), priv->modulus) +
 174                priv->offset;
 175 }
 176
 177 static void nft_ng_random_eval(const struct nft_expr *expr,
 178                                struct nft_regs *regs,
 179                                const struct nft_pktinfo *pkt)
 180 {
 181         struct nft_ng_random *priv = nft_expr_priv(expr);
 182
 183         regs->data[priv->dreg] = nft_ng_random_gen(priv);
 184 }
 185
 186 static void nft_ng_random_map_eval(const struct nft_expr *expr,
 187                                    struct nft_regs *regs,
 188                                    const struct nft_pktinfo *pkt)
 189 {
 190         struct nft_ng_random *priv = nft_expr_priv(expr);
 191         const struct nft_set *map = priv->map;
 192         const struct nft_set_ext *ext;
 193         u32 result;
 194         bool found;
 195
 196         result = nft_ng_random_gen(priv);
 197         found = map->ops->lookup(nft_net(pkt), map, &result, &ext);
 198         if (!found)
 199                 return;
 200
 201         nft_data_copy(&regs->data[priv->dreg],
 202                       nft_set_ext_data(ext), map->dlen);
 203 }
 204
 205 static int nft_ng_random_init(const struct nft_ctx *ctx,
 206                               const struct nft_expr *expr,
 207                               const struct nlattr * const tb[])
 208 {
 209         struct nft_ng_random *priv = nft_expr_priv(expr);
 210
 211         if (tb[NFTA_NG_OFFSET])
 212                 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
 213
 214         priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
 215         if (priv->modulus == 0)
 216                 return -ERANGE;
 217
 218         if (priv->offset + priv->modulus - 1 < priv->offset)
 219                 return -EOVERFLOW;
 220
 221         prandom_init_once(&nft_numgen_prandom_state);
 222
 223         priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
 224
 225         return nft_validate_register_store(ctx, priv->dreg, NULL,
 226                                            NFT_DATA_VALUE, sizeof(u32));
 227 }
 228
 229 static int nft_ng_random_map_init(const struct nft_ctx *ctx,
 230                                   const struct nft_expr *expr,
 231                                   const struct nlattr * const tb[])
 232 {
 233         struct nft_ng_random *priv = nft_expr_priv(expr);
 234         u8 genmask = nft_genmask_next(ctx->net);
 235
 236         nft_ng_random_init(ctx, expr, tb);
 237         priv->map = nft_set_lookup_global(ctx->net, ctx->table,
 238                                           tb[NFTA_NG_SET_NAME],
 239                                           tb[NFTA_NG_SET_ID], genmask);
 240
 241         return PTR_ERR_OR_ZERO(priv->map);
 242 }
 243
 244 static int nft_ng_random_dump(struct sk_buff *skb, const struct nft_expr *expr)
 245 {
 246         const struct nft_ng_random *priv = nft_expr_priv(expr);
 247
 248         return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_RANDOM,
 249                            priv->offset);
 250 }
 251
 252 static int nft_ng_random_map_dump(struct sk_buff *skb,
 253                                   const struct nft_expr *expr)
 254 {
 255         const struct nft_ng_random *priv = nft_expr_priv(expr);
 256
 257         if (nft_ng_dump(skb, priv->dreg, priv->modulus,
 258                         NFT_NG_RANDOM, priv->offset) ||
 259             nla_put_string(skb, NFTA_NG_SET_NAME, priv->map->name))
 260                 goto nla_put_failure;
 261
 262         return 0;
 263
 264 nla_put_failure:
 265         return -1;
 266 }
 267
 268 static struct nft_expr_type nft_ng_type;
 269 static const struct nft_expr_ops nft_ng_inc_ops = {
 270         .type           = &nft_ng_type,
 271         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)),
 272         .eval           = nft_ng_inc_eval,
 273         .init           = nft_ng_inc_init,
 274         .dump           = nft_ng_inc_dump,
 275 };
 276
 277 static const struct nft_expr_ops nft_ng_inc_map_ops = {
 278         .type           = &nft_ng_type,
 279         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)),
 280         .eval           = nft_ng_inc_map_eval,
 281         .init           = nft_ng_inc_map_init,
 282         .dump           = nft_ng_inc_map_dump,
 283 };
 284
 285 static const struct nft_expr_ops nft_ng_random_ops = {
 286         .type           = &nft_ng_type,
 287         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)),
 288         .eval           = nft_ng_random_eval,
 289         .init           = nft_ng_random_init,
 290         .dump           = nft_ng_random_dump,
 291 };
 292
 293 static const struct nft_expr_ops nft_ng_random_map_ops = {
 294         .type           = &nft_ng_type,
 295         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)),
 296         .eval           = nft_ng_random_map_eval,
 297         .init           = nft_ng_random_map_init,
 298         .dump           = nft_ng_random_map_dump,
 299 };
 300
 301 static const struct nft_expr_ops *
 302 nft_ng_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[])
 303 {
 304         u32 type;
 305
 306         if (!tb[NFTA_NG_DREG]    ||
 307             !tb[NFTA_NG_MODULUS] ||
 308             !tb[NFTA_NG_TYPE])
 309                 return ERR_PTR(-EINVAL);
 310
 311         type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE]));
 312
 313         switch (type) {
 314         case NFT_NG_INCREMENTAL:
 315                 if (tb[NFTA_NG_SET_NAME])
 316                         return &nft_ng_inc_map_ops;
 317                 return &nft_ng_inc_ops;
 318         case NFT_NG_RANDOM:
 319                 if (tb[NFTA_NG_SET_NAME])
 320                         return &nft_ng_random_map_ops;
 321                 return &nft_ng_random_ops;
 322         }
 323
 324         return ERR_PTR(-EINVAL);
 325 }
 326
 327 static struct nft_expr_type nft_ng_type __read_mostly = {
 328         .name           = "numgen",
 329         .select_ops     = nft_ng_select_ops,
 330         .policy         = nft_ng_policy,
 331         .maxattr        = NFTA_NG_MAX,
 332         .owner          = THIS_MODULE,
 333 };
 334
 335 static int __init nft_ng_module_init(void)
 336 {
 337         return nft_register_expr(&nft_ng_type);
 338 }
 339
 340 static void __exit nft_ng_module_exit(void)
 341 {
 342         nft_unregister_expr(&nft_ng_type);
 343 }
 344
 345 module_init(nft_ng_module_init);
 346 module_exit(nft_ng_module_exit);
 347
 348 MODULE_LICENSE("GPL");
 349 MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
 350 MODULE_ALIAS_NFT_EXPR("numgen");