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/netlink_delinearize.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/netlink_delinearize.c')
-rw-r--r-- | src/netlink_delinearize.c | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/src/netlink_delinearize.c b/src/netlink_delinearize.c index adcce67b..1a1cfbde 100644 --- a/src/netlink_delinearize.c +++ b/src/netlink_delinearize.c @@ -463,6 +463,34 @@ static void netlink_parse_exthdr(struct netlink_parse_ctx *ctx, netlink_set_register(ctx, dreg, expr); } +static void netlink_parse_hash(struct netlink_parse_ctx *ctx, + const struct location *loc, + const struct nftnl_expr *nle) +{ + enum nft_registers sreg, dreg; + struct expr *expr, *hexpr; + uint32_t mod, seed, len; + + sreg = netlink_parse_register(nle, NFTNL_EXPR_HASH_SREG); + hexpr = netlink_get_register(ctx, loc, sreg); + + seed = nftnl_expr_get_u32(nle, NFTNL_EXPR_HASH_SEED); + mod = nftnl_expr_get_u32(nle, NFTNL_EXPR_HASH_MODULUS); + len = nftnl_expr_get_u32(nle, NFTNL_EXPR_HASH_LEN) * BITS_PER_BYTE; + + if (hexpr->len < len) { + hexpr = netlink_parse_concat_expr(ctx, loc, sreg, len); + if (hexpr == NULL) + return; + } + + expr = hash_expr_alloc(loc, mod, seed); + expr->hash.expr = hexpr; + + dreg = netlink_parse_register(nle, NFTNL_EXPR_HASH_DREG); + netlink_set_register(ctx, dreg, expr); +} + static void netlink_parse_meta_expr(struct netlink_parse_ctx *ctx, const struct location *loc, const struct nftnl_expr *nle) @@ -1020,6 +1048,7 @@ static const struct { { .name = "match", .parse = netlink_parse_match }, { .name = "quota", .parse = netlink_parse_quota }, { .name = "numgen", .parse = netlink_parse_numgen }, + { .name = "hash", .parse = netlink_parse_hash }, }; static int netlink_parse_expr(const struct nftnl_expr *nle, @@ -1641,6 +1670,9 @@ static void expr_postprocess(struct rule_pp_ctx *ctx, struct expr **exprp) case EXPR_VERDICT: case EXPR_NUMGEN: break; + case EXPR_HASH: + expr_postprocess(ctx, &expr->hash.expr); + break; case EXPR_CT: ct_expr_update_type(&ctx->pctx, expr); break; |