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/evaluate.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/evaluate.c')
-rw-r--r-- | src/evaluate.c | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/src/evaluate.c b/src/evaluate.c index ed722df9..8f7824b5 100644 --- a/src/evaluate.c +++ b/src/evaluate.c @@ -1183,6 +1183,25 @@ static int expr_evaluate_numgen(struct eval_ctx *ctx, struct expr **exprp) return expr_evaluate_primary(ctx, exprp); } +static int expr_evaluate_hash(struct eval_ctx *ctx, struct expr **exprp) +{ + struct expr *expr = *exprp; + + expr_dtype_integer_compatible(ctx, expr); + + expr_set_context(&ctx->ectx, NULL, 0); + if (expr_evaluate(ctx, &expr->hash.expr) < 0) + return -1; + + /* expr_evaluate_primary() sets the context to what to the input + * expression to be hashed. Since this input is transformed to a 4 bytes + * integer, restore context to the datatype that results from hashing. + */ + expr_set_context(&ctx->ectx, expr->dtype, expr->len); + + return 0; +} + /* * Transfer the invertible binops to the constant side of an equality * expression. A left shift is only invertible if the low n bits are @@ -1587,6 +1606,8 @@ static int expr_evaluate(struct eval_ctx *ctx, struct expr **expr) return expr_evaluate_relational(ctx, expr); case EXPR_NUMGEN: return expr_evaluate_numgen(ctx, expr); + case EXPR_HASH: + return expr_evaluate_hash(ctx, expr); default: BUG("unknown expression type %s\n", (*expr)->ops->name); } |