netfilter: nf_tables: add hash expression

This patch adds a new hash expression, this provides jhash support but
this can be extended to support for other hash functions. The modulus
and seed already comes embedded into this new expression.

Use case example:

	... meta mark set hash ip saddr mod 10

Signed-off-by: Laura Garcia Liebana <nevola@gmail.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 01751faccaf87661adb96e63cba35a2df653bceb..6ce0a6dd088987765a8d0a7b70122d7bda485134 100644 (file)
--- a/include/uapi/linux/netfilter/nf_tables.h
+++ b/include/uapi/linux/netfilter/nf_tables.h
@@ -723,6 +723,26 @@ enum nft_meta_keys {
        NFT_META_PRANDOM,
 };
 
+/**
+ * enum nft_hash_attributes - nf_tables hash expression netlink attributes
+ *
+ * @NFTA_HASH_SREG: source register (NLA_U32)
+ * @NFTA_HASH_DREG: destination register (NLA_U32)
+ * @NFTA_HASH_LEN: source data length (NLA_U32)
+ * @NFTA_HASH_MODULUS: modulus value (NLA_U32)
+ * @NFTA_HASH_SEED: seed value (NLA_U32)
+ */
+enum nft_hash_attributes {
+       NFTA_HASH_UNSPEC,
+       NFTA_HASH_SREG,
+       NFTA_HASH_DREG,
+       NFTA_HASH_LEN,
+       NFTA_HASH_MODULUS,
+       NFTA_HASH_SEED,
+       __NFTA_HASH_MAX,
+};
+#define NFTA_HASH_MAX  (__NFTA_HASH_MAX - 1)
+
 /**
  * enum nft_meta_attributes - nf_tables meta expression netlink attributes
  *

diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index e5740e108a0b2547f575f078c927835b8c58b222..9cfaa00c79b2464808f7733425bc9fb295663656 100644 (file)
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -563,6 +563,12 @@ config NFT_COMPAT
          x_tables match/target extensions over the nf_tables
          framework.
 
+config NFT_HASH
+       tristate "Netfilter nf_tables hash module"
+       help
+         This option adds the "hash" expression that you can use to perform
+         a hash operation on registers.
+
 if NF_TABLES_NETDEV
 
 config NF_DUP_NETDEV

diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 101fb859203c065e5cdb6d30872ba187f2b6e6a9..1106ccde215c31dd06c6951f25cf93dfd2f0a4c6 100644 (file)
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -92,6 +92,7 @@ obj-$(CONFIG_NFT_COUNTER)     += nft_counter.o
 obj-$(CONFIG_NFT_LOG)          += nft_log.o
 obj-$(CONFIG_NFT_MASQ)         += nft_masq.o
 obj-$(CONFIG_NFT_REDIR)                += nft_redir.o
+obj-$(CONFIG_NFT_HASH)         += nft_hash.o
 
 # nf_tables netdev
 obj-$(CONFIG_NFT_DUP_NETDEV)   += nft_dup_netdev.o

diff --git a/net/netfilter/nft_hash.c b/net/netfilter/nft_hash.c
new file mode 100644 (file)
index 0000000..b82ff29
--- /dev/null
+++ b/net/netfilter/nft_hash.c
@@ -0,0 +1,136 @@
+/*
+ * Copyright (c) 2016 Laura Garcia <nevola@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/netlink.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter/nf_tables.h>
+#include <net/netfilter/nf_tables.h>
+#include <net/netfilter/nf_tables_core.h>
+#include <linux/jhash.h>
+
+struct nft_hash {
+       enum nft_registers      sreg:8;
+       enum nft_registers      dreg:8;
+       u8                      len;
+       u32                     modulus;
+       u32                     seed;
+};
+
+static void nft_hash_eval(const struct nft_expr *expr,
+                         struct nft_regs *regs,
+                         const struct nft_pktinfo *pkt)
+{
+       struct nft_hash *priv = nft_expr_priv(expr);
+       const void *data = &regs->data[priv->sreg];
+
+       regs->data[priv->dreg] =
+               reciprocal_scale(jhash(data, priv->len, priv->seed),
+                                priv->modulus);
+}
+
+const struct nla_policy nft_hash_policy[NFTA_HASH_MAX + 1] = {
+       [NFTA_HASH_SREG]        = { .type = NLA_U32 },
+       [NFTA_HASH_DREG]        = { .type = NLA_U32 },
+       [NFTA_HASH_LEN]         = { .type = NLA_U32 },
+       [NFTA_HASH_MODULUS]     = { .type = NLA_U32 },
+       [NFTA_HASH_SEED]        = { .type = NLA_U32 },
+};
+
+static int nft_hash_init(const struct nft_ctx *ctx,
+                        const struct nft_expr *expr,
+                        const struct nlattr * const tb[])
+{
+       struct nft_hash *priv = nft_expr_priv(expr);
+       u32 len;
+
+       if (!tb[NFTA_HASH_SREG] ||
+           !tb[NFTA_HASH_DREG] ||
+           !tb[NFTA_HASH_LEN]  ||
+           !tb[NFTA_HASH_SEED] ||
+           !tb[NFTA_HASH_MODULUS])
+               return -EINVAL;
+
+       priv->sreg = nft_parse_register(tb[NFTA_HASH_SREG]);
+       priv->dreg = nft_parse_register(tb[NFTA_HASH_DREG]);
+
+       len = ntohl(nla_get_be32(tb[NFTA_HASH_LEN]));
+       if (len == 0 || len > U8_MAX)
+               return -ERANGE;
+
+       priv->len = len;
+
+       priv->modulus = ntohl(nla_get_be32(tb[NFTA_HASH_MODULUS]));
+       if (priv->modulus <= 1)
+               return -ERANGE;
+
+       priv->seed = ntohl(nla_get_be32(tb[NFTA_HASH_SEED]));
+
+       return nft_validate_register_load(priv->sreg, len) &&
+              nft_validate_register_store(ctx, priv->dreg, NULL,
+                                          NFT_DATA_VALUE, sizeof(u32));
+}
+
+static int nft_hash_dump(struct sk_buff *skb,
+                        const struct nft_expr *expr)
+{
+       const struct nft_hash *priv = nft_expr_priv(expr);
+
+       if (nft_dump_register(skb, NFTA_HASH_SREG, priv->sreg))
+               goto nla_put_failure;
+       if (nft_dump_register(skb, NFTA_HASH_DREG, priv->dreg))
+               goto nla_put_failure;
+       if (nft_dump_register(skb, NFTA_HASH_LEN, priv->len))
+               goto nla_put_failure;
+       if (nft_dump_register(skb, NFTA_HASH_MODULUS, priv->modulus))
+               goto nla_put_failure;
+       if (nft_dump_register(skb, NFTA_HASH_SEED, priv->seed))
+               goto nla_put_failure;
+
+       return 0;
+
+nla_put_failure:
+       return -1;
+}
+
+static struct nft_expr_type nft_hash_type;
+static const struct nft_expr_ops nft_hash_ops = {
+       .type           = &nft_hash_type,
+       .size           = NFT_EXPR_SIZE(sizeof(struct nft_hash)),
+       .eval           = nft_hash_eval,
+       .init           = nft_hash_init,
+       .dump           = nft_hash_dump,
+};
+
+static struct nft_expr_type nft_hash_type __read_mostly = {
+       .name           = "hash",
+       .ops            = &nft_hash_ops,
+       .policy         = nft_hash_policy,
+       .maxattr        = NFTA_HASH_MAX,
+       .owner          = THIS_MODULE,
+};
+
+static int __init nft_hash_module_init(void)
+{
+       return nft_register_expr(&nft_hash_type);
+}
+
+static void __exit nft_hash_module_exit(void)
+{
+       nft_unregister_expr(&nft_hash_type);
+}
+
+module_init(nft_hash_module_init);
+module_exit(nft_hash_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
+MODULE_ALIAS_NFT_EXPR("hash");