From: Russell King <rmk@xxxxxxxxxxxxxxxx>
Date: Mon, 28 Apr 2008 11:18:35 +0100
> Further to this, it's looking like there's a nf_conntrack issue. Having
> placed similar printks in the netfilter code, I see the ipv4_confirm()
> hook normally returning 1 (NF_ACCEPT), but then decides to return 0
> (NF_DROP) and no ping replies.
There's already been a report about specific hashing problems with
conntrack on ARM. It has something to do with how structures are
padding on ARM combined with the following patch made by Patrick:
commit 0794935e21a18e7c171b604c31219b60ad9749a9
Author: Patrick McHardy <kaber@xxxxxxxxx>
Date: Thu Jan 31 04:40:52 2008 -0800
[NETFILTER]: nf_conntrack: optimize hash_conntrack()
Avoid calling jhash three times and hash the entire tuple in one go.
__hash_conntrack | -485 # 760 -> 275, # inlines: 3 -> 1, size inlines: 717 -> 252
1 function changed, 485 bytes removed
Signed-off-by: Patrick McHardy <kaber@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index ce4c4ba..4a2cce1 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -73,15 +73,19 @@ static unsigned int nf_conntrack_hash_rnd;
static u_int32_t __hash_conntrack(const struct nf_conntrack_tuple *tuple,
unsigned int size, unsigned int rnd)
{
- unsigned int a, b;
+ unsigned int n;
+ u_int32_t h;
- a = jhash2(tuple->src.u3.all, ARRAY_SIZE(tuple->src.u3.all),
- (tuple->src.l3num << 16) | tuple->dst.protonum);
- b = jhash2(tuple->dst.u3.all, ARRAY_SIZE(tuple->dst.u3.all),
- ((__force __u16)tuple->src.u.all << 16) |
- (__force __u16)tuple->dst.u.all);
+ /* The direction must be ignored, so we hash everything up to the
+ * destination ports (which is a multiple of 4) and treat the last
+ * three bytes manually.
+ */
+ n = (sizeof(tuple->src) + sizeof(tuple->dst.u3)) / sizeof(u32);
+ h = jhash2((u32 *)tuple, n,
+ rnd ^ (((__force __u16)tuple->dst.u.all << 16) |
+ tuple->dst.protonum));
- return ((u64)jhash_2words(a, b, rnd) * size) >> 32;
+ return ((u64)h * size) >> 32;
}
static inline u_int32_t hash_conntrack(const struct nf_conntrack_tuple *tuple)
--
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