src: hash: support of symmetric hash

This patch provides symmetric hash support according to source
ip address and port, and destination ip address and port.

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

Signed-off-by: Laura Garcia Liebana <laura.garcia@zevenet.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/expression.h b/include/expression.h
index 83ecf111..4f2948cc 100644
--- a/include/expression.h
+++ b/include/expression.h
@@ -309,6 +309,7 @@ struct expr {
 			uint32_t		mod;
 			uint32_t		seed;
 			uint32_t		offset;
+			enum nft_hash_types	type;
 		} hash;
 		struct {
 			/* EXPR_FIB */