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         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");