From 13eeed6ea6f0a5d1353ee5ad14c4322695b4f59b Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Fri, 26 Aug 2016 14:41:41 +0200 Subject: src: add numgen expression This new expression allows us to generate incremental and random numbers bound to a specified modulus value. The following rule sets the conntrack mark of 0 to the first packet seen, then 1 to second packet, then 0 again to the third packet and so on: # nft add rule x y ct mark set numgen inc mod 2 A more useful example is a simple load balancing scenario, where you can also use maps to set the destination NAT address based on this new numgen expression: # nft add rule nat prerouting \ dnat to numgen inc mod 2 map { 0 : 192.168.10.100, 1 : 192.168.20.200 } So this is distributing new connections in a round-robin fashion between 192.168.10.100 and 192.168.20.200. Don't forget the special NAT chain semantics: Only the first packet evaluates the rule, follow up packets rely on conntrack to apply the NAT information. You can also emulate flow distribution with different backend weights using intervals: # nft add rule nat prerouting \ dnat to numgen inc mod 10 map { 0-5 : 192.168.10.100, 6-9 : 192.168.20.200 } So 192.168.10.100 gets 60% of the workload, while 192.168.20.200 gets 40%. We can also be mixed with dynamic sets, thus weight can be updated in runtime. Signed-off-by: Pablo Neira Ayuso --- src/netlink_linearize.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'src/netlink_linearize.c') diff --git a/src/netlink_linearize.c b/src/netlink_linearize.c index a14d0ff9..2c6848c5 100644 --- a/src/netlink_linearize.c +++ b/src/netlink_linearize.c @@ -151,6 +151,19 @@ static void netlink_gen_meta(struct netlink_linearize_ctx *ctx, nftnl_rule_add_expr(ctx->nlr, nle); } +static void netlink_gen_numgen(struct netlink_linearize_ctx *ctx, + const struct expr *expr, + enum nft_registers dreg) +{ + struct nftnl_expr *nle; + + nle = alloc_nft_expr("numgen"); + netlink_put_register(nle, NFTNL_EXPR_NG_DREG, dreg); + netlink_put_register(nle, NFTNL_EXPR_NG_TYPE, expr->numgen.type); + nftnl_expr_set_u32(nle, NFTNL_EXPR_NG_UNTIL, expr->numgen.mod); + nftnl_rule_add_expr(ctx->nlr, nle); +} + static void netlink_gen_ct(struct netlink_linearize_ctx *ctx, const struct expr *expr, enum nft_registers dreg) @@ -614,6 +627,8 @@ static void netlink_gen_expr(struct netlink_linearize_ctx *ctx, return netlink_gen_ct(ctx, expr, dreg); case EXPR_SET_ELEM: return netlink_gen_expr(ctx, expr->key, dreg); + case EXPR_NUMGEN: + return netlink_gen_numgen(ctx, expr, dreg); default: BUG("unknown expression type %s\n", expr->ops->name); } -- cgit v1.2.3