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>

diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
index 05215d30fe5c9853b7871e799ccdce4878a04ef1..4f7d75682c5917cf9b26e70d9ac09b2e02d8ed7c 100644 (file)
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -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)

diff --git a/net/netfilter/nft_hash.c b/net/netfilter/nft_hash.c
index ccb834ef049ba75a0bcd4b83e5afea8cc87b36e9..a6a4633725bb4cba848112bc3ea9978fe34d6ea4 100644 (file)
--- 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);
+       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,