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_hash {
  21         enum nft_registers      sreg:8;
  22         enum nft_registers      dreg:8;
  23         u8                      len;
  24         u32                     modulus;
  25         u32                     seed;
  26 };
  27
  28 static void nft_hash_eval(const struct nft_expr *expr,
  29                           struct nft_regs *regs,
  30                           const struct nft_pktinfo *pkt)
  31 {
  32         struct nft_hash *priv = nft_expr_priv(expr);
  33         const void *data = &regs->data[priv->sreg];
  34
  35         regs->data[priv->dreg] =
  36                 reciprocal_scale(jhash(data, priv->len, priv->seed),
  37                                  priv->modulus);
  38 }
  39
  40 const struct nla_policy nft_hash_policy[NFTA_HASH_MAX + 1] = {
  41         [NFTA_HASH_SREG]        = { .type = NLA_U32 },
  42         [NFTA_HASH_DREG]        = { .type = NLA_U32 },
  43         [NFTA_HASH_LEN]         = { .type = NLA_U32 },
  44         [NFTA_HASH_MODULUS]     = { .type = NLA_U32 },
  45         [NFTA_HASH_SEED]        = { .type = NLA_U32 },
  46 };
  47
  48 static int nft_hash_init(const struct nft_ctx *ctx,
  49                          const struct nft_expr *expr,
  50                          const struct nlattr * const tb[])
  51 {
  52         struct nft_hash *priv = nft_expr_priv(expr);
  53         u32 len;
  54
  55         if (!tb[NFTA_HASH_SREG] ||
  56             !tb[NFTA_HASH_DREG] ||
  57             !tb[NFTA_HASH_LEN]  ||
  58             !tb[NFTA_HASH_SEED] ||
  59             !tb[NFTA_HASH_MODULUS])
  60                 return -EINVAL;
  61
  62         priv->sreg = nft_parse_register(tb[NFTA_HASH_SREG]);
  63         priv->dreg = nft_parse_register(tb[NFTA_HASH_DREG]);
  64
  65         len = ntohl(nla_get_be32(tb[NFTA_HASH_LEN]));
  66         if (len == 0 || len > U8_MAX)
  67                 return -ERANGE;
  68
  69         priv->len = len;
  70
  71         priv->modulus = ntohl(nla_get_be32(tb[NFTA_HASH_MODULUS]));
  72         if (priv->modulus <= 1)
  73                 return -ERANGE;
  74
  75         priv->seed = ntohl(nla_get_be32(tb[NFTA_HASH_SEED]));
  76
  77         return nft_validate_register_load(priv->sreg, len) &&
  78                nft_validate_register_store(ctx, priv->dreg, NULL,
  79                                            NFT_DATA_VALUE, sizeof(u32));
  80 }
  81
  82 static int nft_hash_dump(struct sk_buff *skb,
  83                          const struct nft_expr *expr)
  84 {
  85         const struct nft_hash *priv = nft_expr_priv(expr);
  86
  87         if (nft_dump_register(skb, NFTA_HASH_SREG, priv->sreg))
  88                 goto nla_put_failure;
  89         if (nft_dump_register(skb, NFTA_HASH_DREG, priv->dreg))
  90                 goto nla_put_failure;
  91         if (nft_dump_register(skb, NFTA_HASH_LEN, priv->len))
  92                 goto nla_put_failure;
  93         if (nft_dump_register(skb, NFTA_HASH_MODULUS, priv->modulus))
  94                 goto nla_put_failure;
  95         if (nft_dump_register(skb, NFTA_HASH_SEED, priv->seed))
  96                 goto nla_put_failure;
  97
  98         return 0;
  99
 100 nla_put_failure:
 101         return -1;
 102 }
 103
 104 static struct nft_expr_type nft_hash_type;
 105 static const struct nft_expr_ops nft_hash_ops = {
 106         .type           = &nft_hash_type,
 107         .size           = NFT_EXPR_SIZE(sizeof(struct nft_hash)),
 108         .eval           = nft_hash_eval,
 109         .init           = nft_hash_init,
 110         .dump           = nft_hash_dump,
 111 };
 112
 113 static struct nft_expr_type nft_hash_type __read_mostly = {
 114         .name           = "hash",
 115         .ops            = &nft_hash_ops,
 116         .policy         = nft_hash_policy,
 117         .maxattr        = NFTA_HASH_MAX,
 118         .owner          = THIS_MODULE,
 119 };
 120
 121 static int __init nft_hash_module_init(void)
 122 {
 123         return nft_register_expr(&nft_hash_type);
 124 }
 125
 126 static void __exit nft_hash_module_exit(void)
 127 {
 128         nft_unregister_expr(&nft_hash_type);
 129 }
 130
 131 module_init(nft_hash_module_init);
 132 module_exit(nft_hash_module_exit);
 133
 134 MODULE_LICENSE("GPL");
 135 MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
 136 MODULE_ALIAS_NFT_EXPR("hash");