net/netfilter/nft_hash.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 <net/netfilter/nf_tables.h>
  17 #include <net/netfilter/nf_tables_core.h>
  18 #include <linux/jhash.h>
  19
  20 struct nft_jhash {
  21         u8                      sreg;
  22         u8                      dreg;
  23         u8                      len;
  24         bool                    autogen_seed:1;
  25         u32                     modulus;
  26         u32                     seed;
  27         u32                     offset;
  28 };
  29
  30 static void nft_jhash_eval(const struct nft_expr *expr,
  31                            struct nft_regs *regs,
  32                            const struct nft_pktinfo *pkt)
  33 {
  34         struct nft_jhash *priv = nft_expr_priv(expr);
  35         const void *data = &regs->data[priv->sreg];
  36         u32 h;
  37
  38         h = reciprocal_scale(jhash(data, priv->len, priv->seed), priv->modulus);
  39         regs->data[priv->dreg] = h + priv->offset;
  40 }
  41
  42 struct nft_symhash {
  43         u8                      dreg;
  44         u32                     modulus;
  45         u32                     offset;
  46 };
  47
  48 static void nft_symhash_eval(const struct nft_expr *expr,
  49                              struct nft_regs *regs,
  50                              const struct nft_pktinfo *pkt)
  51 {
  52         struct nft_symhash *priv = nft_expr_priv(expr);
  53         struct sk_buff *skb = pkt->skb;
  54         u32 h;
  55
  56         h = reciprocal_scale(__skb_get_hash_symmetric(skb), priv->modulus);
  57
  58         regs->data[priv->dreg] = h + priv->offset;
  59 }
  60
  61 static const struct nla_policy nft_hash_policy[NFTA_HASH_MAX + 1] = {
  62         [NFTA_HASH_SREG]        = { .type = NLA_U32 },
  63         [NFTA_HASH_DREG]        = { .type = NLA_U32 },
  64         [NFTA_HASH_LEN]         = { .type = NLA_U32 },
  65         [NFTA_HASH_MODULUS]     = { .type = NLA_U32 },
  66         [NFTA_HASH_SEED]        = { .type = NLA_U32 },
  67         [NFTA_HASH_OFFSET]      = { .type = NLA_U32 },
  68         [NFTA_HASH_TYPE]        = { .type = NLA_U32 },
  69 };
  70
  71 static int nft_jhash_init(const struct nft_ctx *ctx,
  72                           const struct nft_expr *expr,
  73                           const struct nlattr * const tb[])
  74 {
  75         struct nft_jhash *priv = nft_expr_priv(expr);
  76         u32 len;
  77         int err;
  78
  79         if (!tb[NFTA_HASH_SREG] ||
  80             !tb[NFTA_HASH_DREG] ||
  81             !tb[NFTA_HASH_LEN]  ||
  82             !tb[NFTA_HASH_MODULUS])
  83                 return -EINVAL;
  84
  85         if (tb[NFTA_HASH_OFFSET])
  86                 priv->offset = ntohl(nla_get_be32(tb[NFTA_HASH_OFFSET]));
  87
  88         err = nft_parse_u32_check(tb[NFTA_HASH_LEN], U8_MAX, &len);
  89         if (err < 0)
  90                 return err;
  91         if (len == 0)
  92                 return -ERANGE;
  93
  94         priv->len = len;
  95
  96         err = nft_parse_register_load(tb[NFTA_HASH_SREG], &priv->sreg, len);
  97         if (err < 0)
  98                 return err;
  99
 100         priv->modulus = ntohl(nla_get_be32(tb[NFTA_HASH_MODULUS]));
 101         if (priv->modulus <= 1)
 102                 return -ERANGE;
 103
 104         if (priv->offset + priv->modulus - 1 < priv->offset)
 105                 return -EOVERFLOW;
 106
 107         if (tb[NFTA_HASH_SEED]) {
 108                 priv->seed = ntohl(nla_get_be32(tb[NFTA_HASH_SEED]));
 109         } else {
 110                 priv->autogen_seed = true;
 111                 get_random_bytes(&priv->seed, sizeof(priv->seed));
 112         }
 113
 114         return nft_parse_register_store(ctx, tb[NFTA_HASH_DREG], &priv->dreg,
 115                                         NULL, NFT_DATA_VALUE, sizeof(u32));
 116 }
 117
 118 static int nft_symhash_init(const struct nft_ctx *ctx,
 119                             const struct nft_expr *expr,
 120                             const struct nlattr * const tb[])
 121 {
 122         struct nft_symhash *priv = nft_expr_priv(expr);
 123
 124         if (!tb[NFTA_HASH_DREG]    ||
 125             !tb[NFTA_HASH_MODULUS])
 126                 return -EINVAL;
 127
 128         if (tb[NFTA_HASH_OFFSET])
 129                 priv->offset = ntohl(nla_get_be32(tb[NFTA_HASH_OFFSET]));
 130
 131         priv->modulus = ntohl(nla_get_be32(tb[NFTA_HASH_MODULUS]));
 132         if (priv->modulus < 1)
 133                 return -ERANGE;
 134
 135         if (priv->offset + priv->modulus - 1 < priv->offset)
 136                 return -EOVERFLOW;
 137
 138         return nft_parse_register_store(ctx, tb[NFTA_HASH_DREG],
 139                                         &priv->dreg, NULL, NFT_DATA_VALUE,
 140                                         sizeof(u32));
 141 }
 142
 143 static int nft_jhash_dump(struct sk_buff *skb,
 144                           const struct nft_expr *expr)
 145 {
 146         const struct nft_jhash *priv = nft_expr_priv(expr);
 147
 148         if (nft_dump_register(skb, NFTA_HASH_SREG, priv->sreg))
 149                 goto nla_put_failure;
 150         if (nft_dump_register(skb, NFTA_HASH_DREG, priv->dreg))
 151                 goto nla_put_failure;
 152         if (nla_put_be32(skb, NFTA_HASH_LEN, htonl(priv->len)))
 153                 goto nla_put_failure;
 154         if (nla_put_be32(skb, NFTA_HASH_MODULUS, htonl(priv->modulus)))
 155                 goto nla_put_failure;
 156         if (!priv->autogen_seed &&
 157             nla_put_be32(skb, NFTA_HASH_SEED, htonl(priv->seed)))
 158                 goto nla_put_failure;
 159         if (priv->offset != 0)
 160                 if (nla_put_be32(skb, NFTA_HASH_OFFSET, htonl(priv->offset)))
 161                         goto nla_put_failure;
 162         if (nla_put_be32(skb, NFTA_HASH_TYPE, htonl(NFT_HASH_JENKINS)))
 163                 goto nla_put_failure;
 164         return 0;
 165
 166 nla_put_failure:
 167         return -1;
 168 }
 169
 170 static int nft_symhash_dump(struct sk_buff *skb,
 171                             const struct nft_expr *expr)
 172 {
 173         const struct nft_symhash *priv = nft_expr_priv(expr);
 174
 175         if (nft_dump_register(skb, NFTA_HASH_DREG, priv->dreg))
 176                 goto nla_put_failure;
 177         if (nla_put_be32(skb, NFTA_HASH_MODULUS, htonl(priv->modulus)))
 178                 goto nla_put_failure;
 179         if (priv->offset != 0)
 180                 if (nla_put_be32(skb, NFTA_HASH_OFFSET, htonl(priv->offset)))
 181                         goto nla_put_failure;
 182         if (nla_put_be32(skb, NFTA_HASH_TYPE, htonl(NFT_HASH_SYM)))
 183                 goto nla_put_failure;
 184         return 0;
 185
 186 nla_put_failure:
 187         return -1;
 188 }
 189
 190 static struct nft_expr_type nft_hash_type;
 191 static const struct nft_expr_ops nft_jhash_ops = {
 192         .type           = &nft_hash_type,
 193         .size           = NFT_EXPR_SIZE(sizeof(struct nft_jhash)),
 194         .eval           = nft_jhash_eval,
 195         .init           = nft_jhash_init,
 196         .dump           = nft_jhash_dump,
 197 };
 198
 199 static const struct nft_expr_ops nft_symhash_ops = {
 200         .type           = &nft_hash_type,
 201         .size           = NFT_EXPR_SIZE(sizeof(struct nft_symhash)),
 202         .eval           = nft_symhash_eval,
 203         .init           = nft_symhash_init,
 204         .dump           = nft_symhash_dump,
 205 };
 206
 207 static const struct nft_expr_ops *
 208 nft_hash_select_ops(const struct nft_ctx *ctx,
 209                     const struct nlattr * const tb[])
 210 {
 211         u32 type;
 212
 213         if (!tb[NFTA_HASH_TYPE])
 214                 return &nft_jhash_ops;
 215
 216         type = ntohl(nla_get_be32(tb[NFTA_HASH_TYPE]));
 217         switch (type) {
 218         case NFT_HASH_SYM:
 219                 return &nft_symhash_ops;
 220         case NFT_HASH_JENKINS:
 221                 return &nft_jhash_ops;
 222         default:
 223                 break;
 224         }
 225         return ERR_PTR(-EOPNOTSUPP);
 226 }
 227
 228 static struct nft_expr_type nft_hash_type __read_mostly = {
 229         .name           = "hash",
 230         .select_ops     = nft_hash_select_ops,
 231         .policy         = nft_hash_policy,
 232         .maxattr        = NFTA_HASH_MAX,
 233         .owner          = THIS_MODULE,
 234 };
 235
 236 static int __init nft_hash_module_init(void)
 237 {
 238         return nft_register_expr(&nft_hash_type);
 239 }
 240
 241 static void __exit nft_hash_module_exit(void)
 242 {
 243         nft_unregister_expr(&nft_hash_type);
 244 }
 245
 246 module_init(nft_hash_module_init);
 247 module_exit(nft_hash_module_exit);
 248
 249 MODULE_LICENSE("GPL");
 250 MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
 251 MODULE_ALIAS_NFT_EXPR("hash");