netdev - [PATCH 02/18] netfilter: nf_nat: use hash random for bysource hash

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Date:	Thu, 24 Nov 2011 17:57:13 +0100
From:	kaber@...sh.net
To:	netfilter-devel@...r.kernel.org
Cc:	netdev@...r.kernel.org, kaber@...sh.net, ulrich.weber@...hos.com
Subject: [PATCH 02/18] netfilter: nf_nat: use hash random for bysource hash

From: Patrick McHardy <kaber@...sh.net>

Use nf_conntrack_hash_rnd in NAT bysource hash to avoid hash chain attacks.

Signed-off-by: Patrick McHardy <kaber@...sh.net>
Acked-by: Eric Dumazet <eric.dumazet@...il.com>
---
 net/ipv4/netfilter/nf_nat_core.c  |    2 +-
 net/netfilter/nf_conntrack_core.c |    1 +
 2 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/net/ipv4/netfilter/nf_nat_core.c b/net/ipv4/netfilter/nf_nat_core.c
index 58ab7a4..76600f8 100644
--- a/net/ipv4/netfilter/nf_nat_core.c
+++ b/net/ipv4/netfilter/nf_nat_core.c
@@ -57,7 +57,7 @@ hash_by_src(const struct net *net, u16 zone,
 	/* Original src, to ensure we map it consistently if poss. */
 	hash = jhash_3words((__force u32)tuple->src.u3.ip,
 			    (__force u32)tuple->src.u.all ^ zone,
-			    tuple->dst.protonum, 0);
+			    tuple->dst.protonum, nf_conntrack_hash_rnd);
 	return ((u64)hash * net->ipv4.nat_htable_size) >> 32;
 }
 
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 7202b06..1d23cc4 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -67,6 +67,7 @@ DEFINE_PER_CPU(struct nf_conn, nf_conntrack_untracked);
 EXPORT_PER_CPU_SYMBOL(nf_conntrack_untracked);
 
 unsigned int nf_conntrack_hash_rnd __read_mostly;
+EXPORT_SYMBOL_GPL(nf_conntrack_hash_rnd);
 
 static u32 hash_conntrack_raw(const struct nf_conntrack_tuple *tuple, u16 zone)
 {
-- 
1.7.1

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