From 345236211715ffb7cc28f6ff0b26acb90181e738 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Fri, 26 Aug 2016 18:00:00 +0200 Subject: src: add hash expression This is special expression that transforms an input expression into a 32-bit unsigned integer. This expression takes a modulus parameter to scale the result and the random seed so the hash result becomes harder to predict. You can use it to set the packet mark, eg. # nft add rule x y meta mark set jhash ip saddr . ip daddr mod 2 seed 0xdeadbeef You can combine this with maps too, eg. # nft add rule x y dnat to jhash ip saddr mod 2 seed 0xdeadbeef map { \ 0 : 192.168.20.100, \ 1 : 192.168.30.100 \ } Currently, this expression implements the jenkins hash implementation available in the Linux kernel: http://lxr.free-electrons.com/source/include/linux/jhash.h But it should be possible to extend it to support any other hash function type. Signed-off-by: Pablo Neira Ayuso --- src/netlink_linearize.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) (limited to 'src/netlink_linearize.c') diff --git a/src/netlink_linearize.c b/src/netlink_linearize.c index 2c6848c5..5204154a 100644 --- a/src/netlink_linearize.c +++ b/src/netlink_linearize.c @@ -104,6 +104,27 @@ static void netlink_gen_concat(struct netlink_linearize_ctx *ctx, } } +static void netlink_gen_hash(struct netlink_linearize_ctx *ctx, + const struct expr *expr, + enum nft_registers dreg) +{ + enum nft_registers sreg; + struct nftnl_expr *nle; + + sreg = get_register(ctx, expr->hash.expr); + netlink_gen_expr(ctx, expr->hash.expr, sreg); + release_register(ctx, expr->hash.expr); + + nle = alloc_nft_expr("hash"); + netlink_put_register(nle, NFTNL_EXPR_HASH_SREG, sreg); + netlink_put_register(nle, NFTNL_EXPR_HASH_DREG, dreg); + nftnl_expr_set_u32(nle, NFTNL_EXPR_HASH_LEN, + div_round_up(expr->hash.expr->len, BITS_PER_BYTE)); + nftnl_expr_set_u32(nle, NFTNL_EXPR_HASH_MODULUS, expr->hash.mod); + nftnl_expr_set_u32(nle, NFTNL_EXPR_HASH_SEED, expr->hash.seed); + nftnl_rule_add_expr(ctx->nlr, nle); +} + static void netlink_gen_payload(struct netlink_linearize_ctx *ctx, const struct expr *expr, enum nft_registers dreg) @@ -629,6 +650,8 @@ static void netlink_gen_expr(struct netlink_linearize_ctx *ctx, return netlink_gen_expr(ctx, expr->key, dreg); case EXPR_NUMGEN: return netlink_gen_numgen(ctx, expr, dreg); + case EXPR_HASH: + return netlink_gen_hash(ctx, expr, dreg); default: BUG("unknown expression type %s\n", expr->ops->name); } -- cgit v1.2.3