netfilter: nf_tables: add flag to indicate set contains expressions

Add a set flag to indicate that the set is used as a state table and
contains expressions for evaluation. This operation is mutually
exclusive with the mapping operation, so sets specifying both are
rejected. The lookup expression also rejects binding to state tables
since it only deals with loopup and map operations.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/uapi/linux/netfilter/nf_tables.h

@@ -238,6 +238,7 @@ enum nft_rule_compat_attributes {
  * @NFT_SET_INTERVAL: set contains intervals
  * @NFT_SET_MAP: set is used as a dictionary
  * @NFT_SET_TIMEOUT: set uses timeouts
+ * @NFT_SET_EVAL: set contains expressions for evaluation
  */
 enum nft_set_flags {
 	NFT_SET_ANONYMOUS		= 0x1,
@@ -245,6 +246,7 @@ enum nft_set_flags {
 	NFT_SET_INTERVAL		= 0x4,
 	NFT_SET_MAP			= 0x8,
 	NFT_SET_TIMEOUT			= 0x10,
+	NFT_SET_EVAL			= 0x20,
 };
 
 /**

net/netfilter/nf_tables_api.c

@@ -2661,9 +2661,13 @@ static int nf_tables_newset(struct sock *nlsk, struct sk_buff *skb,
 	if (nla[NFTA_SET_FLAGS] != NULL) {
 		flags = ntohl(nla_get_be32(nla[NFTA_SET_FLAGS]));
 		if (flags & ~(NFT_SET_ANONYMOUS | NFT_SET_CONSTANT |
-			      NFT_SET_INTERVAL | NFT_SET_MAP |
-			      NFT_SET_TIMEOUT))
+			      NFT_SET_INTERVAL | NFT_SET_TIMEOUT |
+			      NFT_SET_MAP | NFT_SET_EVAL))
 			return -EINVAL;
+		/* Only one of both operations is supported */
+		if ((flags & (NFT_SET_MAP | NFT_SET_EVAL)) ==
+			     (NFT_SET_MAP | NFT_SET_EVAL))
+			return -EOPNOTSUPP;
 	}
 
 	dtype = 0;

net/netfilter/nft_lookup.c

@@ -71,6 +71,9 @@ static int nft_lookup_init(const struct nft_ctx *ctx,
 			return PTR_ERR(set);
 	}
 
+	if (set->flags & NFT_SET_EVAL)
+		return -EOPNOTSUPP;
+
 	priv->sreg = nft_parse_register(tb[NFTA_LOOKUP_SREG]);
 	err = nft_validate_register_load(priv->sreg, set->klen);
 	if (err < 0)