netfilter: nf_tables: Support for sets with multiple ranged fields

Introduce a new nested netlink attribute, NFTA_SET_DESC_CONCAT, used
to specify the length of each field in a set concatenation.

This allows set implementations to support concatenation of multiple
ranged items, as they can divide the input key into matching data for
every single field. Such set implementations would be selected as
they specify support for NFT_SET_INTERVAL and allow desc->field_count
to be greater than one. Explicitly disallow this for nft_set_rbtree.

In order to specify the interval for a set entry, userspace would
include in NFTA_SET_DESC_CONCAT attributes field lengths, and pass
range endpoints as two separate keys, represented by attributes
NFTA_SET_ELEM_KEY and NFTA_SET_ELEM_KEY_END.

While at it, export the number of 32-bit registers available for
packet matching, as nftables will need this to know the maximum
number of field lengths that can be specified.

For example, "packets with an IPv4 address between 192.0.2.0 and
192.0.2.42, with destination port between 22 and 25", can be
expressed as two concatenated elements:

  NFTA_SET_ELEM_KEY:            192.0.2.0 . 22
  NFTA_SET_ELEM_KEY_END:        192.0.2.42 . 25

and NFTA_SET_DESC_CONCAT attribute would contain:

  NFTA_LIST_ELEM
    NFTA_SET_FIELD_LEN:		4
  NFTA_LIST_ELEM
    NFTA_SET_FIELD_LEN:		2

v4: No changes
v3: Complete rework, NFTA_SET_DESC_CONCAT instead of NFTA_SET_SUBKEY
v2: No changes

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index 504c0aa93805..4170c033d461 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -264,11 +264,15 @@ struct nft_set_iter {
  *	@klen: key length
  *	@dlen: data length
  *	@size: number of set elements
+ *	@field_len: length of each field in concatenation, bytes
+ *	@field_count: number of concatenated fields in element
  */
 struct nft_set_desc {
 	unsigned int		klen;
 	unsigned int		dlen;
 	unsigned int		size;
+	u8			field_len[NFT_REG32_COUNT];
+	u8			field_count;
 };
 
 /**
@@ -409,6 +413,8 @@ void nft_unregister_set(struct nft_set_type *type);
  * 	@dtype: data type (verdict or numeric type defined by userspace)
  * 	@objtype: object type (see NFT_OBJECT_* definitions)
  * 	@size: maximum set size
+ *	@field_len: length of each field in concatenation, bytes
+ *	@field_count: number of concatenated fields in element
  *	@use: number of rules references to this set
  * 	@nelems: number of elements
  * 	@ndeact: number of deactivated elements queued for removal
@@ -435,6 +441,8 @@ struct nft_set {
 	u32				dtype;
 	u32				objtype;
 	u32				size;
+	u8				field_len[NFT_REG32_COUNT];
+	u8				field_count;
 	u32				use;
 	atomic_t			nelems;
 	u32				ndeact;