netdev - Re: arp

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Message-ID: <20150322232242.GA9105@gondor.apana.org.au>
Date:	Mon, 23 Mar 2015 10:22:42 +1100
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Roland Dreier <roland@...estorage.com>
Subject: Re: arp_hash

On Mon, Mar 23, 2015 at 09:51:04AM +1100, Herbert Xu wrote:
> 
> OK I'm wrong because net/core/neighbour.c uses only the high-order
> bits of the hash.

Unfortunately even the high-order bits are too predictable:

10.0.0.128	0xbd78b1f2
10.0.0.64	0xfd78b1f2
10.0.0.192	0x7d78b1f2
10.0.0.32	0x9d78b1f2
...
10.0.0.63	0xd078b1f2
10.0.0.191	0x5078b1f2
10.0.0.127	0x9078b1f2
10.0.0.255	0x1078b1f2
10.0.1.0	0x60bdb1f2

As you can see there is a bit-to-bit correspondence.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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