net/netfilter/nft_numgen.c

   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         enum nft_registers      dreg:8;
  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         priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
  70         atomic_set(&priv->counter, priv->modulus - 1);
  71
  72         return nft_validate_register_store(ctx, priv->dreg, NULL,
  73                                            NFT_DATA_VALUE, sizeof(u32));
  74 }
  75
  76 static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg,
  77                        u32 modulus, enum nft_ng_types type, u32 offset)
  78 {
  79         if (nft_dump_register(skb, NFTA_NG_DREG, dreg))
  80                 goto nla_put_failure;
  81         if (nla_put_be32(skb, NFTA_NG_MODULUS, htonl(modulus)))
  82                 goto nla_put_failure;
  83         if (nla_put_be32(skb, NFTA_NG_TYPE, htonl(type)))
  84                 goto nla_put_failure;
  85         if (nla_put_be32(skb, NFTA_NG_OFFSET, htonl(offset)))
  86                 goto nla_put_failure;
  87
  88         return 0;
  89
  90 nla_put_failure:
  91         return -1;
  92 }
  93
  94 static int nft_ng_inc_dump(struct sk_buff *skb, const struct nft_expr *expr)
  95 {
  96         const struct nft_ng_inc *priv = nft_expr_priv(expr);
  97
  98         return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_INCREMENTAL,
  99                            priv->offset);
 100 }
 101
 102 struct nft_ng_random {
 103         enum nft_registers      dreg:8;
 104         u32                     modulus;
 105         u32                     offset;
 106 };
 107
 108 static u32 nft_ng_random_gen(struct nft_ng_random *priv)
 109 {
 110         struct rnd_state *state = this_cpu_ptr(&nft_numgen_prandom_state);
 111
 112         return reciprocal_scale(prandom_u32_state(state), priv->modulus) +
 113                priv->offset;
 114 }
 115
 116 static void nft_ng_random_eval(const struct nft_expr *expr,
 117                                struct nft_regs *regs,
 118                                const struct nft_pktinfo *pkt)
 119 {
 120         struct nft_ng_random *priv = nft_expr_priv(expr);
 121
 122         regs->data[priv->dreg] = nft_ng_random_gen(priv);
 123 }
 124
 125 static int nft_ng_random_init(const struct nft_ctx *ctx,
 126                               const struct nft_expr *expr,
 127                               const struct nlattr * const tb[])
 128 {
 129         struct nft_ng_random *priv = nft_expr_priv(expr);
 130
 131         if (tb[NFTA_NG_OFFSET])
 132                 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
 133
 134         priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
 135         if (priv->modulus == 0)
 136                 return -ERANGE;
 137
 138         if (priv->offset + priv->modulus - 1 < priv->offset)
 139                 return -EOVERFLOW;
 140
 141         prandom_init_once(&nft_numgen_prandom_state);
 142
 143         priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
 144
 145         return nft_validate_register_store(ctx, priv->dreg, NULL,
 146                                            NFT_DATA_VALUE, sizeof(u32));
 147 }
 148
 149 static int nft_ng_random_dump(struct sk_buff *skb, const struct nft_expr *expr)
 150 {
 151         const struct nft_ng_random *priv = nft_expr_priv(expr);
 152
 153         return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_RANDOM,
 154                            priv->offset);
 155 }
 156
 157 static struct nft_expr_type nft_ng_type;
 158 static const struct nft_expr_ops nft_ng_inc_ops = {
 159         .type           = &nft_ng_type,
 160         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)),
 161         .eval           = nft_ng_inc_eval,
 162         .init           = nft_ng_inc_init,
 163         .dump           = nft_ng_inc_dump,
 164 };
 165
 166 static const struct nft_expr_ops nft_ng_random_ops = {
 167         .type           = &nft_ng_type,
 168         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)),
 169         .eval           = nft_ng_random_eval,
 170         .init           = nft_ng_random_init,
 171         .dump           = nft_ng_random_dump,
 172 };
 173
 174 static const struct nft_expr_ops *
 175 nft_ng_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[])
 176 {
 177         u32 type;
 178
 179         if (!tb[NFTA_NG_DREG]    ||
 180             !tb[NFTA_NG_MODULUS] ||
 181             !tb[NFTA_NG_TYPE])
 182                 return ERR_PTR(-EINVAL);
 183
 184         type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE]));
 185
 186         switch (type) {
 187         case NFT_NG_INCREMENTAL:
 188                 return &nft_ng_inc_ops;
 189         case NFT_NG_RANDOM:
 190                 return &nft_ng_random_ops;
 191         }
 192
 193         return ERR_PTR(-EINVAL);
 194 }
 195
 196 static struct nft_expr_type nft_ng_type __read_mostly = {
 197         .name           = "numgen",
 198         .select_ops     = nft_ng_select_ops,
 199         .policy         = nft_ng_policy,
 200         .maxattr        = NFTA_NG_MAX,
 201         .owner          = THIS_MODULE,
 202 };
 203
 204 static int __init nft_ng_module_init(void)
 205 {
 206         return nft_register_expr(&nft_ng_type);
 207 }
 208
 209 static void __exit nft_ng_module_exit(void)
 210 {
 211         nft_unregister_expr(&nft_ng_type);
 212 }
 213
 214 module_init(nft_ng_module_init);
 215 module_exit(nft_ng_module_exit);
 216
 217 MODULE_LICENSE("GPL");
 218 MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
 219 MODULE_ALIAS_NFT_EXPR("numgen");
 220 MODULE_DESCRIPTION("nftables number generator module");