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 u32 nft_ng_inc_gen(struct nft_ng_inc *priv)
  30 {
  31         u32 nval, oval;
  32
  33         do {
  34                 oval = atomic_read(&priv->counter);
  35                 nval = (oval + 1 < priv->modulus) ? oval + 1 : 0;
  36         } while (atomic_cmpxchg(&priv->counter, oval, nval) != oval);
  37
  38         return nval + priv->offset;
  39 }
  40
  41 static void nft_ng_inc_eval(const struct nft_expr *expr,
  42                             struct nft_regs *regs,
  43                             const struct nft_pktinfo *pkt)
  44 {
  45         struct nft_ng_inc *priv = nft_expr_priv(expr);
  46
  47         regs->data[priv->dreg] = nft_ng_inc_gen(priv);
  48 }
  49
  50 static const struct nla_policy nft_ng_policy[NFTA_NG_MAX + 1] = {
  51         [NFTA_NG_DREG]          = { .type = NLA_U32 },
  52         [NFTA_NG_MODULUS]       = { .type = NLA_U32 },
  53         [NFTA_NG_TYPE]          = { .type = NLA_U32 },
  54         [NFTA_NG_OFFSET]        = { .type = NLA_U32 },
  55 };
  56
  57 static int nft_ng_inc_init(const struct nft_ctx *ctx,
  58                            const struct nft_expr *expr,
  59                            const struct nlattr * const tb[])
  60 {
  61         struct nft_ng_inc *priv = nft_expr_priv(expr);
  62
  63         if (tb[NFTA_NG_OFFSET])
  64                 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
  65
  66         priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
  67         if (priv->modulus == 0)
  68                 return -ERANGE;
  69
  70         if (priv->offset + priv->modulus - 1 < priv->offset)
  71                 return -EOVERFLOW;
  72
  73         priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
  74         atomic_set(&priv->counter, priv->modulus - 1);
  75
  76         return nft_validate_register_store(ctx, priv->dreg, NULL,
  77                                            NFT_DATA_VALUE, sizeof(u32));
  78 }
  79
  80 static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg,
  81                        u32 modulus, enum nft_ng_types type, u32 offset)
  82 {
  83         if (nft_dump_register(skb, NFTA_NG_DREG, dreg))
  84                 goto nla_put_failure;
  85         if (nla_put_be32(skb, NFTA_NG_MODULUS, htonl(modulus)))
  86                 goto nla_put_failure;
  87         if (nla_put_be32(skb, NFTA_NG_TYPE, htonl(type)))
  88                 goto nla_put_failure;
  89         if (nla_put_be32(skb, NFTA_NG_OFFSET, htonl(offset)))
  90                 goto nla_put_failure;
  91
  92         return 0;
  93
  94 nla_put_failure:
  95         return -1;
  96 }
  97
  98 static int nft_ng_inc_dump(struct sk_buff *skb, const struct nft_expr *expr)
  99 {
 100         const struct nft_ng_inc *priv = nft_expr_priv(expr);
 101
 102         return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_INCREMENTAL,
 103                            priv->offset);
 104 }
 105
 106 struct nft_ng_random {
 107         enum nft_registers      dreg:8;
 108         u32                     modulus;
 109         u32                     offset;
 110 };
 111
 112 static u32 nft_ng_random_gen(struct nft_ng_random *priv)
 113 {
 114         struct rnd_state *state = this_cpu_ptr(&nft_numgen_prandom_state);
 115
 116         return reciprocal_scale(prandom_u32_state(state), priv->modulus) +
 117                priv->offset;
 118 }
 119
 120 static void nft_ng_random_eval(const struct nft_expr *expr,
 121                                struct nft_regs *regs,
 122                                const struct nft_pktinfo *pkt)
 123 {
 124         struct nft_ng_random *priv = nft_expr_priv(expr);
 125
 126         regs->data[priv->dreg] = nft_ng_random_gen(priv);
 127 }
 128
 129 static int nft_ng_random_init(const struct nft_ctx *ctx,
 130                               const struct nft_expr *expr,
 131                               const struct nlattr * const tb[])
 132 {
 133         struct nft_ng_random *priv = nft_expr_priv(expr);
 134
 135         if (tb[NFTA_NG_OFFSET])
 136                 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
 137
 138         priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
 139         if (priv->modulus == 0)
 140                 return -ERANGE;
 141
 142         if (priv->offset + priv->modulus - 1 < priv->offset)
 143                 return -EOVERFLOW;
 144
 145         prandom_init_once(&nft_numgen_prandom_state);
 146
 147         priv->dreg = nft_parse_register(tb[NFTA_NG_DREG]);
 148
 149         return nft_validate_register_store(ctx, priv->dreg, NULL,
 150                                            NFT_DATA_VALUE, sizeof(u32));
 151 }
 152
 153 static int nft_ng_random_dump(struct sk_buff *skb, const struct nft_expr *expr)
 154 {
 155         const struct nft_ng_random *priv = nft_expr_priv(expr);
 156
 157         return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_RANDOM,
 158                            priv->offset);
 159 }
 160
 161 static struct nft_expr_type nft_ng_type;
 162 static const struct nft_expr_ops nft_ng_inc_ops = {
 163         .type           = &nft_ng_type,
 164         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)),
 165         .eval           = nft_ng_inc_eval,
 166         .init           = nft_ng_inc_init,
 167         .dump           = nft_ng_inc_dump,
 168 };
 169
 170 static const struct nft_expr_ops nft_ng_random_ops = {
 171         .type           = &nft_ng_type,
 172         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)),
 173         .eval           = nft_ng_random_eval,
 174         .init           = nft_ng_random_init,
 175         .dump           = nft_ng_random_dump,
 176 };
 177
 178 static const struct nft_expr_ops *
 179 nft_ng_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[])
 180 {
 181         u32 type;
 182
 183         if (!tb[NFTA_NG_DREG]    ||
 184             !tb[NFTA_NG_MODULUS] ||
 185             !tb[NFTA_NG_TYPE])
 186                 return ERR_PTR(-EINVAL);
 187
 188         type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE]));
 189
 190         switch (type) {
 191         case NFT_NG_INCREMENTAL:
 192                 return &nft_ng_inc_ops;
 193         case NFT_NG_RANDOM:
 194                 return &nft_ng_random_ops;
 195         }
 196
 197         return ERR_PTR(-EINVAL);
 198 }
 199
 200 static struct nft_expr_type nft_ng_type __read_mostly = {
 201         .name           = "numgen",
 202         .select_ops     = nft_ng_select_ops,
 203         .policy         = nft_ng_policy,
 204         .maxattr        = NFTA_NG_MAX,
 205         .owner          = THIS_MODULE,
 206 };
 207
 208 static int __init nft_ng_module_init(void)
 209 {
 210         return nft_register_expr(&nft_ng_type);
 211 }
 212
 213 static void __exit nft_ng_module_exit(void)
 214 {
 215         nft_unregister_expr(&nft_ng_type);
 216 }
 217
 218 module_init(nft_ng_module_init);
 219 module_exit(nft_ng_module_exit);
 220
 221 MODULE_LICENSE("GPL");
 222 MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
 223 MODULE_ALIAS_NFT_EXPR("numgen");