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/scanner.l | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'src/scanner.l') diff --git a/src/scanner.l b/src/scanner.l index 53b79aa5..cff375f3 100644 --- a/src/scanner.l +++ b/src/scanner.l @@ -467,6 +467,10 @@ addrstring ({macaddr}|{ip4addr}|{ip6addr}) "proto-dst" { return PROTO_DST; } "label" { return LABEL; } +"numgen" { return NUMGEN; } +"inc" { return INC; } +"mod" { return MOD; } + "dup" { return DUP; } "fwd" { return FWD; } -- cgit v1.2.3