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netfilter: nf_tables: Support for sets with multiple ranged fields

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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>
This commit is contained in:
Stefano Brivio
2020-01-22 00:17:53 +01:00
committed by Pablo Neira Ayuso
parent 7b225d0b5c
commit f3a2181e16
4 changed files with 115 additions and 1 deletions
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15
include/uapi/linux/netfilter/nf_tables.h
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@@ -48,6 +48,7 @@ enum nft_registers {
#define NFT_REG_SIZE 16
#define NFT_REG32_SIZE 4
#define NFT_REG32_COUNT (NFT_REG32_15 - NFT_REG32_00 + 1)
/**
* enum nft_verdicts - nf_tables internal verdicts
@@ -301,14 +302,28 @@ enum nft_set_policies {
* enum nft_set_desc_attributes - set element description
*
* @NFTA_SET_DESC_SIZE: number of elements in set (NLA_U32)
* @NFTA_SET_DESC_CONCAT: description of field concatenation (NLA_NESTED)
*/
enum nft_set_desc_attributes {
NFTA_SET_DESC_UNSPEC,
NFTA_SET_DESC_SIZE,
NFTA_SET_DESC_CONCAT,
__NFTA_SET_DESC_MAX
};
#define NFTA_SET_DESC_MAX (__NFTA_SET_DESC_MAX - 1)
/**
* enum nft_set_field_attributes - attributes of concatenated fields
*
* @NFTA_SET_FIELD_LEN: length of single field, in bits (NLA_U32)
*/
enum nft_set_field_attributes {
NFTA_SET_FIELD_UNSPEC,
NFTA_SET_FIELD_LEN,
__NFTA_SET_FIELD_MAX
};
#define NFTA_SET_FIELD_MAX (__NFTA_SET_FIELD_MAX - 1)
/**
* enum nft_set_attributes - nf_tables set netlink attributes
*