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netfilter: nft_hash: support of symmetric hash 

This patch provides symmetric hash support according to source
ip address and port, and destination ip address and port.

For this purpose, the __skb_get_hash_symmetric() is used to
identify the flow as it uses FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL
flag by default.

The new attribute NFTA_HASH_TYPE has been included to support
different types of hashing functions. Currently supported
NFT_HASH_JENKINS through jhash and NFT_HASH_SYM through symhash.

The main difference between both types are:
 - jhash requires an expression with sreg, symhash doesn't.
 - symhash supports modulus and offset, but not seed.

Examples:

 nft add rule ip nat prerouting ct mark set jhash ip saddr mod 2
 nft add rule ip nat prerouting ct mark set symhash mod 2

By default, jenkins hash will be used if no hash type is
provided for compatibility reasons.

Signed-off-by: Laura Garcia Liebana <laura.garcia@zevenet.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Laura Garcia Liebana 2017-03-02 17:00:14 +01:00 committed by Pablo Neira Ayuso
parent 511040eea2
commit 3206caded8
2 changed files with 111 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
include/uapi/linux/netfilter/nf_tables.h
View File

@ -815,6 +815,17 @@ enum nft_rt_keys {
NFT_RT_NEXTHOP6,
};
/**
* enum nft_hash_types - nf_tables hash expression types
*
* @NFT_HASH_JENKINS: Jenkins Hash
* @NFT_HASH_SYM: Symmetric Hash
*/
enum nft_hash_types {
NFT_HASH_JENKINS,
NFT_HASH_SYM,
};
/**
* enum nft_hash_attributes - nf_tables hash expression netlink attributes
*
@ -824,6 +835,7 @@ enum nft_rt_keys {
* @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)
* @NFTA_HASH_TYPE: hash operation (NLA_U32: nft_hash_types)
*/
enum nft_hash_attributes {
NFTA_HASH_UNSPEC,
@ -833,6 +845,7 @@ enum nft_hash_attributes {
NFTA_HASH_MODULUS,
NFTA_HASH_SEED,
NFTA_HASH_OFFSET,
NFTA_HASH_TYPE,
__NFTA_HASH_MAX,
};
#define NFTA_HASH_MAX (__NFTA_HASH_MAX - 1)

99
net/netfilter/nft_hash.c
View File

@ -38,6 +38,25 @@ static void nft_jhash_eval(const struct nft_expr *expr,
regs->data[priv->dreg] = h + priv->offset;
}
struct nft_symhash {
enum nft_registers dreg:8;
u32 modulus;
u32 offset;
};
static void nft_symhash_eval(const struct nft_expr *expr,
struct nft_regs *regs,
const struct nft_pktinfo *pkt)
{
struct nft_symhash *priv = nft_expr_priv(expr);
struct sk_buff *skb = pkt->skb;
u32 h;
h = reciprocal_scale(__skb_get_hash_symmetric(skb), priv->modulus);
regs->data[priv->dreg] = h + priv->offset;
}
static const struct nla_policy nft_hash_policy[NFTA_HASH_MAX + 1] = {
[NFTA_HASH_SREG] = { .type = NLA_U32 },
[NFTA_HASH_DREG] = { .type = NLA_U32 },
@ -45,6 +64,7 @@ static const struct nla_policy nft_hash_policy[NFTA_HASH_MAX + 1] = {
[NFTA_HASH_MODULUS] = { .type = NLA_U32 },
[NFTA_HASH_SEED] = { .type = NLA_U32 },
[NFTA_HASH_OFFSET] = { .type = NLA_U32 },
[NFTA_HASH_TYPE] = { .type = NLA_U32 },
};
static int nft_jhash_init(const struct nft_ctx *ctx,
@ -92,6 +112,32 @@ static int nft_jhash_init(const struct nft_ctx *ctx,
NFT_DATA_VALUE, sizeof(u32));
}
static int nft_symhash_init(const struct nft_ctx *ctx,
const struct nft_expr *expr,
const struct nlattr * const tb[])
{
struct nft_symhash *priv = nft_expr_priv(expr);
if (!tb[NFTA_HASH_DREG] ||
!tb[NFTA_HASH_MODULUS])
return -EINVAL;
if (tb[NFTA_HASH_OFFSET])
priv->offset = ntohl(nla_get_be32(tb[NFTA_HASH_OFFSET]));
priv->dreg = nft_parse_register(tb[NFTA_HASH_DREG]);
priv->modulus = ntohl(nla_get_be32(tb[NFTA_HASH_MODULUS]));
if (priv->modulus <= 1)
return -ERANGE;
if (priv->offset + priv->modulus - 1 < priv->offset)
return -EOVERFLOW;
return nft_validate_register_store(ctx, priv->dreg, NULL,
NFT_DATA_VALUE, sizeof(u32));
}
static int nft_jhash_dump(struct sk_buff *skb,
const struct nft_expr *expr)
{
@ -110,6 +156,28 @@ static int nft_jhash_dump(struct sk_buff *skb,
if (priv->offset != 0)
if (nla_put_be32(skb, NFTA_HASH_OFFSET, htonl(priv->offset)))
goto nla_put_failure;
if (nla_put_be32(skb, NFTA_HASH_TYPE, htonl(NFT_HASH_JENKINS)))
goto nla_put_failure;
return 0;
nla_put_failure:
return -1;
}
static int nft_symhash_dump(struct sk_buff *skb,
const struct nft_expr *expr)
{
const struct nft_symhash *priv = nft_expr_priv(expr);
if (nft_dump_register(skb, NFTA_HASH_DREG, priv->dreg))
goto nla_put_failure;
if (nla_put_be32(skb, NFTA_HASH_MODULUS, htonl(priv->modulus)))
goto nla_put_failure;
if (priv->offset != 0)
if (nla_put_be32(skb, NFTA_HASH_OFFSET, htonl(priv->offset)))
goto nla_put_failure;
if (nla_put_be32(skb, NFTA_HASH_TYPE, htonl(NFT_HASH_SYM)))
goto nla_put_failure;
return 0;
nla_put_failure:
@ -125,9 +193,38 @@ static const struct nft_expr_ops nft_jhash_ops = {
.dump = nft_jhash_dump,
};
static const struct nft_expr_ops nft_symhash_ops = {
.type = &nft_hash_type,
.size = NFT_EXPR_SIZE(sizeof(struct nft_symhash)),
.eval = nft_symhash_eval,
.init = nft_symhash_init,
.dump = nft_symhash_dump,
};
static const struct nft_expr_ops *
nft_hash_select_ops(const struct nft_ctx *ctx,
const struct nlattr * const tb[])
{
u32 type;
if (!tb[NFTA_HASH_TYPE])
return &nft_jhash_ops;
type = ntohl(nla_get_be32(tb[NFTA_HASH_TYPE]));
switch (type) {
case NFT_HASH_SYM:
return &nft_symhash_ops;
case NFT_HASH_JENKINS:
return &nft_jhash_ops;
default:
break;
}
return ERR_PTR(-EOPNOTSUPP);
}
static struct nft_expr_type nft_hash_type __read_mostly = {
.name = "hash",
.ops = &nft_jhash_ops,
.select_ops = &nft_hash_select_ops,
.policy = nft_hash_policy,
.maxattr = NFTA_HASH_MAX,
.owner = THIS_MODULE,