diff options
author | Pablo Neira Ayuso <pablo@netfilter.org> | 2016-08-26 14:41:41 +0200 |
---|---|---|
committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2016-08-29 20:30:28 +0200 |
commit | 13eeed6ea6f0a5d1353ee5ad14c4322695b4f59b (patch) | |
tree | dee935f0f40bb41399b8d5d0c8ab4f23e53fd7d3 /src/evaluate.c | |
parent | 1ed9a3726c01fda218f37b7f4555c8b7106521ef (diff) |
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 <pablo@netfilter.org>
Diffstat (limited to 'src/evaluate.c')
-rw-r--r-- | src/evaluate.c | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/src/evaluate.c b/src/evaluate.c index d669b85b..ed722df9 100644 --- a/src/evaluate.c +++ b/src/evaluate.c @@ -1158,6 +1158,31 @@ static int expr_evaluate_mapping(struct eval_ctx *ctx, struct expr **expr) return 0; } +/* We got datatype context via statement. If the basetype is compatible, set + * this expression datatype to the one of the statement to make it datatype + * compatible. This is a more conservative approach than enabling datatype + * compatibility between two different datatypes whose basetype is the same, + * let's revisit this later once users come with valid usecases to generalize + * this. + */ +static void expr_dtype_integer_compatible(struct eval_ctx *ctx, + struct expr *expr) +{ + if (ctx->ectx.dtype && + ctx->ectx.dtype->basetype == &integer_type && + ctx->ectx.len == 4 * BITS_PER_BYTE) { + expr->dtype = ctx->ectx.dtype; + expr->len = ctx->ectx.len; + } +} + +static int expr_evaluate_numgen(struct eval_ctx *ctx, struct expr **exprp) +{ + expr_dtype_integer_compatible(ctx, *exprp); + + return expr_evaluate_primary(ctx, exprp); +} + /* * Transfer the invertible binops to the constant side of an equality * expression. A left shift is only invertible if the low n bits are @@ -1560,6 +1585,8 @@ static int expr_evaluate(struct eval_ctx *ctx, struct expr **expr) return expr_evaluate_mapping(ctx, expr); case EXPR_RELATIONAL: return expr_evaluate_relational(ctx, expr); + case EXPR_NUMGEN: + return expr_evaluate_numgen(ctx, expr); default: BUG("unknown expression type %s\n", (*expr)->ops->name); } |