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 --- include/numgen.h | 7 +++++++ 1 file changed, 7 insertions(+) create mode 100644 include/numgen.h (limited to 'include/numgen.h') diff --git a/include/numgen.h b/include/numgen.h new file mode 100644 index 00000000..bec18e5a --- /dev/null +++ b/include/numgen.h @@ -0,0 +1,7 @@ +#ifndef NFTABLES_NUMGEN_H +#define NFTABLES_NUMGEN_H + +extern struct expr *numgen_expr_alloc(const struct location *loc, + enum nft_ng_types type, uint32_t until); + +#endif /* NFTABLES_NUMGEN_H */ -- cgit v1.2.3