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
Signed-off-by: Laura Garcia Liebana <laura.garcia@xxxxxxxxxxx>
---
include/uapi/linux/netfilter/nf_tables.h | 13 +++++
net/netfilter/nft_hash.c | 98 +++++++++++++++++++++++++++++++-
2 files changed, 110 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index 7b730cab99bd..a444a63a9eee 100644
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -793,6 +793,17 @@ enum nft_rt_keys {
};
/**
+ * 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
*
* @NFTA_HASH_SREG: source register (NLA_U32)
@@ -801,6 +812,7 @@ 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,
@@ -810,6 +822,7 @@ 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)
diff --git a/net/netfilter/nft_hash.c b/net/netfilter/nft_hash.c
index ccb834ef049b..da0171908f92 100644
--- a/net/netfilter/nft_hash.c
+++ b/net/netfilter/nft_hash.c
@@ -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);
+ const 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 +193,37 @@ 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 ERR_PTR(-EINVAL);
+
+ type = ntohl(nla_get_be32(tb[NFTA_HASH_TYPE]));
+
+ switch (type) {
+ case NFT_HASH_SYM:
+ return &nft_symhash_ops;
+ case NFT_HASH_JENKINS:
+ default:
+ return &nft_jhash_ops;
+ }
+}
+
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,
--
2.11.0
--
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