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 };
  27
  28 static void nft_ng_inc_eval(const struct nft_expr *expr,
  29                             struct nft_regs *regs,
  30                             const struct nft_pktinfo *pkt)
  31 {
  32         struct nft_ng_inc *priv = nft_expr_priv(expr);
  33         u32 nval, oval;
  34
  35         do {
  36                 oval = atomic_read(&priv->counter);
  37                 nval = (oval + 1 < priv->modulus) ? oval + 1 : 0;
  38         } while (atomic_cmpxchg(&priv->counter, oval, nval) != oval);
  39
  40         regs->data[priv->dreg] = nval;
  41 }
  42
  43 static const struct nla_policy nft_ng_policy[NFTA_NG_MAX + 1] = {
  44         [NFTA_NG_DREG]          = { .type = NLA_U32 },
  45         [NFTA_NG_MODULUS]       = { .type = NLA_U32 },
  46         [NFTA_NG_TYPE]          = { .type = NLA_U32 },
  47 };
  48
  49 static int nft_ng_inc_init(const struct nft_ctx *ctx,
  50                            const struct nft_expr *expr,
  51                            const struct nlattr * const tb[])
  52 {
  53         struct nft_ng_inc *priv = nft_expr_priv(expr);
  54
  55         priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
  56         if (priv->modulus == 0)
  57                 return -ERANGE;
  58
  59         priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
  60         atomic_set(&priv->counter, 0);
  61
  62         return nft_validate_register_store(ctx, priv->dreg, NULL,
  63                                            NFT_DATA_VALUE, sizeof(u32));
  64 }
  65
  66 static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg,
  67                        u32 modulus, enum nft_ng_types type)
  68 {
  69         if (nft_dump_register(skb, NFTA_NG_DREG, dreg))
  70                 goto nla_put_failure;
  71         if (nla_put_be32(skb, NFTA_NG_MODULUS, htonl(modulus)))
  72                 goto nla_put_failure;
  73         if (nla_put_be32(skb, NFTA_NG_TYPE, htonl(type)))
  74                 goto nla_put_failure;
  75
  76         return 0;
  77
  78 nla_put_failure:
  79         return -1;
  80 }
  81
  82 static int nft_ng_inc_dump(struct sk_buff *skb, const struct nft_expr *expr)
  83 {
  84         const struct nft_ng_inc *priv = nft_expr_priv(expr);
  85
  86         return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_INCREMENTAL);
  87 }
  88
  89 struct nft_ng_random {
  90         enum nft_registers      dreg:8;
  91         u32                     modulus;
  92 };
  93
  94 static void nft_ng_random_eval(const struct nft_expr *expr,
  95                                struct nft_regs *regs,
  96                                const struct nft_pktinfo *pkt)
  97 {
  98         struct nft_ng_random *priv = nft_expr_priv(expr);
  99         struct rnd_state *state = this_cpu_ptr(&nft_numgen_prandom_state);
 100
 101         regs->data[priv->dreg] = reciprocal_scale(prandom_u32_state(state),
 102                                                   priv->modulus);
 103 }
 104
 105 static int nft_ng_random_init(const struct nft_ctx *ctx,
 106                               const struct nft_expr *expr,
 107                               const struct nlattr * const tb[])
 108 {
 109         struct nft_ng_random *priv = nft_expr_priv(expr);
 110
 111         priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
 112         if (priv->modulus == 0)
 113                 return -ERANGE;
 114
 115         prandom_init_once(&nft_numgen_prandom_state);
 116
 117         priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
 118
 119         return nft_validate_register_store(ctx, priv->dreg, NULL,
 120                                            NFT_DATA_VALUE, sizeof(u32));
 121 }
 122
 123 static int nft_ng_random_dump(struct sk_buff *skb, const struct nft_expr *expr)
 124 {
 125         const struct nft_ng_random *priv = nft_expr_priv(expr);
 126
 127         return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_RANDOM);
 128 }
 129
 130 static struct nft_expr_type nft_ng_type;
 131 static const struct nft_expr_ops nft_ng_inc_ops = {
 132         .type           = &nft_ng_type,
 133         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)),
 134         .eval           = nft_ng_inc_eval,
 135         .init           = nft_ng_inc_init,
 136         .dump           = nft_ng_inc_dump,
 137 };
 138
 139 static const struct nft_expr_ops nft_ng_random_ops = {
 140         .type           = &nft_ng_type,
 141         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)),
 142         .eval           = nft_ng_random_eval,
 143         .init           = nft_ng_random_init,
 144         .dump           = nft_ng_random_dump,
 145 };
 146
 147 static const struct nft_expr_ops *
 148 nft_ng_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[])
 149 {
 150         u32 type;
 151
 152         if (!tb[NFTA_NG_DREG]    ||
 153             !tb[NFTA_NG_MODULUS] ||
 154             !tb[NFTA_NG_TYPE])
 155                 return ERR_PTR(-EINVAL);
 156
 157         type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE]));
 158
 159         switch (type) {
 160         case NFT_NG_INCREMENTAL:
 161                 return &nft_ng_inc_ops;
 162         case NFT_NG_RANDOM:
 163                 return &nft_ng_random_ops;
 164         }
 165
 166         return ERR_PTR(-EINVAL);
 167 }
 168
 169 static struct nft_expr_type nft_ng_type __read_mostly = {
 170         .name           = "numgen",
 171         .select_ops     = &nft_ng_select_ops,
 172         .policy         = nft_ng_policy,
 173         .maxattr        = NFTA_NG_MAX,
 174         .owner          = THIS_MODULE,
 175 };
 176
 177 static int __init nft_ng_module_init(void)
 178 {
 179         return nft_register_expr(&nft_ng_type);
 180 }
 181
 182 static void __exit nft_ng_module_exit(void)
 183 {
 184         nft_unregister_expr(&nft_ng_type);
 185 }
 186
 187 module_init(nft_ng_module_init);
 188 module_exit(nft_ng_module_exit);
 189
 190 MODULE_LICENSE("GPL");
 191 MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
 192 MODULE_ALIAS_NFT_EXPR("numgen");