netdev - [PATCH 3/7] netfilter: xt_HMARK: modulus is expensive for hash calculation

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Date:	Thu, 17 May 2012 01:06:40 +0200
From:	pablo@...filter.org
To:	netfilter-devel@...r.kernel.org
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH 3/7] netfilter: xt_HMARK: modulus is expensive for hash calculation

From: Pablo Neira Ayuso <pablo@...filter.org>

Use:

((u64)(HASH_VAL * HASH_SIZE)) >> 32

as suggested by David S. Miller.

Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/xt_HMARK.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/xt_HMARK.c b/net/netfilter/xt_HMARK.c
index 5817d03..0a96a43 100644
--- a/net/netfilter/xt_HMARK.c
+++ b/net/netfilter/xt_HMARK.c
@@ -109,7 +109,7 @@ hmark_hash(struct hmark_tuple *t, const struct xt_hmark_info *info)
 	hash = jhash_3words(t->src, t->dst, t->uports.v32, info->hashrnd);
 	hash = hash ^ (t->proto & info->proto_mask);
 
-	return (hash % info->hmodulus) + info->hoffset;
+	return (((u64)hash * info->hmodulus) >> 32) + info->hoffset;
 }
 
 static void
-- 
1.7.10

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