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 };
  28
  29 static void nft_ng_inc_eval(const struct nft_expr *expr,
  30                             struct nft_regs *regs,
  31                             const struct nft_pktinfo *pkt)
  32 {
  33         struct nft_ng_inc *priv = nft_expr_priv(expr);
  34         u32 nval, oval;
  35
  36         do {
  37                 oval = atomic_read(&priv->counter);
  38                 nval = (oval + 1 < priv->modulus) ? oval + 1 : 0;
  39         } while (atomic_cmpxchg(&priv->counter, oval, nval) != oval);
  40
  41         regs->data[priv->dreg] = nval + priv->offset;
  42 }
  43
  44 static const struct nla_policy nft_ng_policy[NFTA_NG_MAX + 1] = {
  45         [NFTA_NG_DREG]          = { .type = NLA_U32 },
  46         [NFTA_NG_MODULUS]       = { .type = NLA_U32 },
  47         [NFTA_NG_TYPE]          = { .type = NLA_U32 },
  48         [NFTA_NG_OFFSET]        = { .type = NLA_U32 },
  49 };
  50
  51 static int nft_ng_inc_init(const struct nft_ctx *ctx,
  52                            const struct nft_expr *expr,
  53                            const struct nlattr * const tb[])
  54 {
  55         struct nft_ng_inc *priv = nft_expr_priv(expr);
  56
  57         if (tb[NFTA_NG_OFFSET])
  58                 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
  59
  60         priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
  61         if (priv->modulus == 0)
  62                 return -ERANGE;
  63
  64         if (priv->offset + priv->modulus - 1 < priv->offset)
  65                 return -EOVERFLOW;
  66
  67         priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
  68         atomic_set(&priv->counter, priv->modulus - 1);
  69
  70         return nft_validate_register_store(ctx, priv->dreg, NULL,
  71                                            NFT_DATA_VALUE, sizeof(u32));
  72 }
  73
  74 static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg,
  75                        u32 modulus, enum nft_ng_types type, u32 offset)
  76 {
  77         if (nft_dump_register(skb, NFTA_NG_DREG, dreg))
  78                 goto nla_put_failure;
  79         if (nla_put_be32(skb, NFTA_NG_MODULUS, htonl(modulus)))
  80                 goto nla_put_failure;
  81         if (nla_put_be32(skb, NFTA_NG_TYPE, htonl(type)))
  82                 goto nla_put_failure;
  83         if (nla_put_be32(skb, NFTA_NG_OFFSET, htonl(offset)))
  84                 goto nla_put_failure;
  85
  86         return 0;
  87
  88 nla_put_failure:
  89         return -1;
  90 }
  91
  92 static int nft_ng_inc_dump(struct sk_buff *skb, const struct nft_expr *expr)
  93 {
  94         const struct nft_ng_inc *priv = nft_expr_priv(expr);
  95
  96         return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_INCREMENTAL,
  97                            priv->offset);
  98 }
  99
 100 struct nft_ng_random {
 101         enum nft_registers      dreg:8;
 102         u32                     modulus;
 103         u32                     offset;
 104 };
 105
 106 static void nft_ng_random_eval(const struct nft_expr *expr,
 107                                struct nft_regs *regs,
 108                                const struct nft_pktinfo *pkt)
 109 {
 110         struct nft_ng_random *priv = nft_expr_priv(expr);
 111         struct rnd_state *state = this_cpu_ptr(&nft_numgen_prandom_state);
 112         u32 val;
 113
 114         val = reciprocal_scale(prandom_u32_state(state), priv->modulus);
 115         regs->data[priv->dreg] = val + priv->offset;
 116 }
 117
 118 static int nft_ng_random_init(const struct nft_ctx *ctx,
 119                               const struct nft_expr *expr,
 120                               const struct nlattr * const tb[])
 121 {
 122         struct nft_ng_random *priv = nft_expr_priv(expr);
 123
 124         if (tb[NFTA_NG_OFFSET])
 125                 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
 126
 127         priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
 128         if (priv->modulus == 0)
 129                 return -ERANGE;
 130
 131         if (priv->offset + priv->modulus - 1 < priv->offset)
 132                 return -EOVERFLOW;
 133
 134         prandom_init_once(&nft_numgen_prandom_state);
 135
 136         priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
 137
 138         return nft_validate_register_store(ctx, priv->dreg, NULL,
 139                                            NFT_DATA_VALUE, sizeof(u32));
 140 }
 141
 142 static int nft_ng_random_dump(struct sk_buff *skb, const struct nft_expr *expr)
 143 {
 144         const struct nft_ng_random *priv = nft_expr_priv(expr);
 145
 146         return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_RANDOM,
 147                            priv->offset);
 148 }
 149
 150 static struct nft_expr_type nft_ng_type;
 151 static const struct nft_expr_ops nft_ng_inc_ops = {
 152         .type           = &nft_ng_type,
 153         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)),
 154         .eval           = nft_ng_inc_eval,
 155         .init           = nft_ng_inc_init,
 156         .dump           = nft_ng_inc_dump,
 157 };
 158
 159 static const struct nft_expr_ops nft_ng_random_ops = {
 160         .type           = &nft_ng_type,
 161         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)),
 162         .eval           = nft_ng_random_eval,
 163         .init           = nft_ng_random_init,
 164         .dump           = nft_ng_random_dump,
 165 };
 166
 167 static const struct nft_expr_ops *
 168 nft_ng_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[])
 169 {
 170         u32 type;
 171
 172         if (!tb[NFTA_NG_DREG]    ||
 173             !tb[NFTA_NG_MODULUS] ||
 174             !tb[NFTA_NG_TYPE])
 175                 return ERR_PTR(-EINVAL);
 176
 177         type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE]));
 178
 179         switch (type) {
 180         case NFT_NG_INCREMENTAL:
 181                 return &nft_ng_inc_ops;
 182         case NFT_NG_RANDOM:
 183                 return &nft_ng_random_ops;
 184         }
 185
 186         return ERR_PTR(-EINVAL);
 187 }
 188
 189 static struct nft_expr_type nft_ng_type __read_mostly = {
 190         .name           = "numgen",
 191         .select_ops     = &nft_ng_select_ops,
 192         .policy         = nft_ng_policy,
 193         .maxattr        = NFTA_NG_MAX,
 194         .owner          = THIS_MODULE,
 195 };
 196
 197 static int __init nft_ng_module_init(void)
 198 {
 199         return nft_register_expr(&nft_ng_type);
 200 }
 201
 202 static void __exit nft_ng_module_exit(void)
 203 {
 204         nft_unregister_expr(&nft_ng_type);
 205 }
 206
 207 module_init(nft_ng_module_init);
 208 module_exit(nft_ng_module_exit);
 209
 210 MODULE_LICENSE("GPL");
 211 MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
 212 MODULE_ALIAS_NFT_EXPR("numgen");