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netfilter: nft_hash: Add hash offset value

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Add support to pass through an offset to the hash value. With this
feature, the sysadmin is able to generate a hash with a given
offset value.

Example:

	meta mark set jhash ip saddr mod 2 seed 0xabcd offset 100

This option generates marks according to the source address from 100 to
101.

Signed-off-by: Laura Garcia Liebana <nevola@gmail.com>
This commit is contained in:
Laura Garcia Liebana 2016-09-06 08:44:19 +02:00 committed by Pablo Neira Ayuso
parent 3c15b8e112
commit 70ca767ea1
2 changed files with 15 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/uapi/linux/netfilter/nf_tables.h
View File

@ -731,6 +731,7 @@ enum nft_meta_keys {
* @NFTA_HASH_LEN: source data length (NLA_U32)
* @NFTA_HASH_MODULUS: modulus value (NLA_U32)
* @NFTA_HASH_SEED: seed value (NLA_U32)
* @NFTA_HASH_OFFSET: add this offset value to hash result (NLA_U32)
*/
enum nft_hash_attributes {
NFTA_HASH_UNSPEC,
@ -739,6 +740,7 @@ enum nft_hash_attributes {
NFTA_HASH_LEN,
NFTA_HASH_MODULUS,
NFTA_HASH_SEED,
NFTA_HASH_OFFSET,
__NFTA_HASH_MAX,
};
#define NFTA_HASH_MAX (__NFTA_HASH_MAX - 1)

17
net/netfilter/nft_hash.c
View File

@ -23,6 +23,7 @@ struct nft_hash {
u8 len;
u32 modulus;
u32 seed;
u32 offset;
};
static void nft_hash_eval(const struct nft_expr *expr,
@ -31,10 +32,10 @@ static void nft_hash_eval(const struct nft_expr *expr,
{
struct nft_hash *priv = nft_expr_priv(expr);
const void *data = &regs->data[priv->sreg];
u32 h;
regs->data[priv->dreg] =
reciprocal_scale(jhash(data, priv->len, priv->seed),
priv->modulus);
h = reciprocal_scale(jhash(data, priv->len, priv->seed), priv->modulus);
regs->data[priv->dreg] = h + priv->offset;
}
static const struct nla_policy nft_hash_policy[NFTA_HASH_MAX + 1] = {
@ -59,6 +60,9 @@ static int nft_hash_init(const struct nft_ctx *ctx,
!tb[NFTA_HASH_MODULUS])
return -EINVAL;
if (tb[NFTA_HASH_OFFSET])
priv->offset = ntohl(nla_get_be32(tb[NFTA_HASH_OFFSET]));
priv->sreg = nft_parse_register(tb[NFTA_HASH_SREG]);
priv->dreg = nft_parse_register(tb[NFTA_HASH_DREG]);
@ -72,6 +76,9 @@ static int nft_hash_init(const struct nft_ctx *ctx,
if (priv->modulus <= 1)
return -ERANGE;
if (priv->offset + priv->modulus - 1 < U32_MAX)
return -EOVERFLOW;
priv->seed = ntohl(nla_get_be32(tb[NFTA_HASH_SEED]));
return nft_validate_register_load(priv->sreg, len) &&
@ -94,7 +101,9 @@ static int nft_hash_dump(struct sk_buff *skb,
goto nla_put_failure;
if (nla_put_be32(skb, NFTA_HASH_SEED, htonl(priv->seed)))
goto nla_put_failure;
if (priv->offset != 0)
if (nla_put_be32(skb, NFTA_HASH_OFFSET, htonl(priv->offset)))
goto nla_put_failure;
return 0;
nla_put_failure: