From 345236211715ffb7cc28f6ff0b26acb90181e738 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Fri, 26 Aug 2016 18:00:00 +0200 Subject: 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 --- src/netlink_delinearize.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) (limited to 'src/netlink_delinearize.c') 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; -- cgit v1.2.3