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Commit 3206cade authored by Laura Garcia Liebana's avatar Laura Garcia Liebana Committed by Pablo Neira Ayuso
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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: default avatarLaura Garcia Liebana <laura.garcia@zevenet.com>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 511040ee

include/uapi/linux/netfilter/nf_tables.h

+13 −0
Original line number Diff line number Diff line
@@ -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)

net/netfilter/nft_hash.c

+98 −1
Original line number Diff line number Diff line
@@ -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,