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/random.h>
  13 #include <linux/static_key.h>
  14 #include <net/netfilter/nf_tables.h>
  15 #include <net/netfilter/nf_tables_core.h>
  16
  17 struct nft_ng_inc {
  18         u8                      dreg;
  19         u32                     modulus;
  20         atomic_t                *counter;
  21         u32                     offset;
  22 };
  23
  24 static u32 nft_ng_inc_gen(struct nft_ng_inc *priv)
  25 {
  26         u32 nval, oval;
  27
  28         do {
  29                 oval = atomic_read(priv->counter);
  30                 nval = (oval + 1 < priv->modulus) ? oval + 1 : 0;
  31         } while (atomic_cmpxchg(priv->counter, oval, nval) != oval);
  32
  33         return nval + priv->offset;
  34 }
  35
  36 static void nft_ng_inc_eval(const struct nft_expr *expr,
  37                             struct nft_regs *regs,
  38                             const struct nft_pktinfo *pkt)
  39 {
  40         struct nft_ng_inc *priv = nft_expr_priv(expr);
  41
  42         regs->data[priv->dreg] = nft_ng_inc_gen(priv);
  43 }
  44
  45 static const struct nla_policy nft_ng_policy[NFTA_NG_MAX + 1] = {
  46         [NFTA_NG_DREG]          = { .type = NLA_U32 },
  47         [NFTA_NG_MODULUS]       = { .type = NLA_U32 },
  48         [NFTA_NG_TYPE]          = { .type = NLA_U32 },
  49         [NFTA_NG_OFFSET]        = { .type = NLA_U32 },
  50 };
  51
  52 static int nft_ng_inc_init(const struct nft_ctx *ctx,
  53                            const struct nft_expr *expr,
  54                            const struct nlattr * const tb[])
  55 {
  56         struct nft_ng_inc *priv = nft_expr_priv(expr);
  57         int err;
  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->counter = kmalloc(sizeof(*priv->counter), GFP_KERNEL_ACCOUNT);
  70         if (!priv->counter)
  71                 return -ENOMEM;
  72
  73         atomic_set(priv->counter, priv->modulus - 1);
  74
  75         err = nft_parse_register_store(ctx, tb[NFTA_NG_DREG], &priv->dreg,
  76                                        NULL, NFT_DATA_VALUE, sizeof(u32));
  77         if (err < 0)
  78                 goto err;
  79
  80         return 0;
  81 err:
  82         kfree(priv->counter);
  83
  84         return err;
  85 }
  86
  87 static bool nft_ng_inc_reduce(struct nft_regs_track *track,
  88                                  const struct nft_expr *expr)
  89 {
  90         const struct nft_ng_inc *priv = nft_expr_priv(expr);
  91
  92         nft_reg_track_cancel(track, priv->dreg, NFT_REG32_SIZE);
  93
  94         return false;
  95 }
  96
  97 static int nft_ng_dump(struct sk_buff *skb, enum nft_registers dreg,
  98                        u32 modulus, enum nft_ng_types type, u32 offset)
  99 {
 100         if (nft_dump_register(skb, NFTA_NG_DREG, dreg))
 101                 goto nla_put_failure;
 102         if (nla_put_be32(skb, NFTA_NG_MODULUS, htonl(modulus)))
 103                 goto nla_put_failure;
 104         if (nla_put_be32(skb, NFTA_NG_TYPE, htonl(type)))
 105                 goto nla_put_failure;
 106         if (nla_put_be32(skb, NFTA_NG_OFFSET, htonl(offset)))
 107                 goto nla_put_failure;
 108
 109         return 0;
 110
 111 nla_put_failure:
 112         return -1;
 113 }
 114
 115 static int nft_ng_inc_dump(struct sk_buff *skb,
 116                            const struct nft_expr *expr, bool reset)
 117 {
 118         const struct nft_ng_inc *priv = nft_expr_priv(expr);
 119
 120         return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_INCREMENTAL,
 121                            priv->offset);
 122 }
 123
 124 static void nft_ng_inc_destroy(const struct nft_ctx *ctx,
 125                                const struct nft_expr *expr)
 126 {
 127         const struct nft_ng_inc *priv = nft_expr_priv(expr);
 128
 129         kfree(priv->counter);
 130 }
 131
 132 struct nft_ng_random {
 133         u8                      dreg;
 134         u32                     modulus;
 135         u32                     offset;
 136 };
 137
 138 static u32 nft_ng_random_gen(const struct nft_ng_random *priv)
 139 {
 140         return reciprocal_scale(get_random_u32(), priv->modulus) + priv->offset;
 141 }
 142
 143 static void nft_ng_random_eval(const struct nft_expr *expr,
 144                                struct nft_regs *regs,
 145                                const struct nft_pktinfo *pkt)
 146 {
 147         struct nft_ng_random *priv = nft_expr_priv(expr);
 148
 149         regs->data[priv->dreg] = nft_ng_random_gen(priv);
 150 }
 151
 152 static int nft_ng_random_init(const struct nft_ctx *ctx,
 153                               const struct nft_expr *expr,
 154                               const struct nlattr * const tb[])
 155 {
 156         struct nft_ng_random *priv = nft_expr_priv(expr);
 157
 158         if (tb[NFTA_NG_OFFSET])
 159                 priv->offset = ntohl(nla_get_be32(tb[NFTA_NG_OFFSET]));
 160
 161         priv->modulus = ntohl(nla_get_be32(tb[NFTA_NG_MODULUS]));
 162         if (priv->modulus == 0)
 163                 return -ERANGE;
 164
 165         if (priv->offset + priv->modulus - 1 < priv->offset)
 166                 return -EOVERFLOW;
 167
 168         return nft_parse_register_store(ctx, tb[NFTA_NG_DREG], &priv->dreg,
 169                                         NULL, NFT_DATA_VALUE, sizeof(u32));
 170 }
 171
 172 static int nft_ng_random_dump(struct sk_buff *skb,
 173                               const struct nft_expr *expr, bool reset)
 174 {
 175         const struct nft_ng_random *priv = nft_expr_priv(expr);
 176
 177         return nft_ng_dump(skb, priv->dreg, priv->modulus, NFT_NG_RANDOM,
 178                            priv->offset);
 179 }
 180
 181 static bool nft_ng_random_reduce(struct nft_regs_track *track,
 182                                  const struct nft_expr *expr)
 183 {
 184         const struct nft_ng_random *priv = nft_expr_priv(expr);
 185
 186         nft_reg_track_cancel(track, priv->dreg, NFT_REG32_SIZE);
 187
 188         return false;
 189 }
 190
 191 static struct nft_expr_type nft_ng_type;
 192 static const struct nft_expr_ops nft_ng_inc_ops = {
 193         .type           = &nft_ng_type,
 194         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_inc)),
 195         .eval           = nft_ng_inc_eval,
 196         .init           = nft_ng_inc_init,
 197         .destroy        = nft_ng_inc_destroy,
 198         .dump           = nft_ng_inc_dump,
 199         .reduce         = nft_ng_inc_reduce,
 200 };
 201
 202 static const struct nft_expr_ops nft_ng_random_ops = {
 203         .type           = &nft_ng_type,
 204         .size           = NFT_EXPR_SIZE(sizeof(struct nft_ng_random)),
 205         .eval           = nft_ng_random_eval,
 206         .init           = nft_ng_random_init,
 207         .dump           = nft_ng_random_dump,
 208         .reduce         = nft_ng_random_reduce,
 209 };
 210
 211 static const struct nft_expr_ops *
 212 nft_ng_select_ops(const struct nft_ctx *ctx, const struct nlattr * const tb[])
 213 {
 214         u32 type;
 215
 216         if (!tb[NFTA_NG_DREG]    ||
 217             !tb[NFTA_NG_MODULUS] ||
 218             !tb[NFTA_NG_TYPE])
 219                 return ERR_PTR(-EINVAL);
 220
 221         type = ntohl(nla_get_be32(tb[NFTA_NG_TYPE]));
 222
 223         switch (type) {
 224         case NFT_NG_INCREMENTAL:
 225                 return &nft_ng_inc_ops;
 226         case NFT_NG_RANDOM:
 227                 return &nft_ng_random_ops;
 228         }
 229
 230         return ERR_PTR(-EINVAL);
 231 }
 232
 233 static struct nft_expr_type nft_ng_type __read_mostly = {
 234         .name           = "numgen",
 235         .select_ops     = nft_ng_select_ops,
 236         .policy         = nft_ng_policy,
 237         .maxattr        = NFTA_NG_MAX,
 238         .owner          = THIS_MODULE,
 239 };
 240
 241 static int __init nft_ng_module_init(void)
 242 {
 243         return nft_register_expr(&nft_ng_type);
 244 }
 245
 246 static void __exit nft_ng_module_exit(void)
 247 {
 248         nft_unregister_expr(&nft_ng_type);
 249 }
 250
 251 module_init(nft_ng_module_init);
 252 module_exit(nft_ng_module_exit);
 253
 254 MODULE_LICENSE("GPL");
 255 MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
 256 MODULE_ALIAS_NFT_EXPR("numgen");
 257 MODULE_DESCRIPTION("nftables number generator module");