diff options
author | Pablo Neira Ayuso <pablo@netfilter.org> | 2016-08-26 18:00:00 +0200 |
---|---|---|
committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2016-08-29 20:30:29 +0200 |
commit | 345236211715ffb7cc28f6ff0b26acb90181e738 (patch) | |
tree | aebfc9aeece1dda1bb1ffab52aa93a9b1114f928 /src/netlink_linearize.c | |
parent | 13eeed6ea6f0a5d1353ee5ad14c4322695b4f59b (diff) |
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 <pablo@netfilter.org>
Diffstat (limited to 'src/netlink_linearize.c')
-rw-r--r-- | src/netlink_linearize.c | 23 |
1 files changed, 23 insertions, 0 deletions
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); } |