netdev - Re: [PATCH net-next] ipv6: add ipv6_addr

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Date:	Wed, 18 Jul 2012 06:57:59 -0700
From:	Joe Perches <joe@...ches.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Andrew McGregor <andrewmcgr@...il.com>,
	Dave Taht <dave.taht@...il.com>,
	Tom Herbert <therbert@...gle.com>
Subject: Re: [PATCH net-next] ipv6: add ipv6_addr_hash() helper

On Wed, 2012-07-18 at 14:08 +0200, Eric Dumazet wrote:
> Introduce ipv6_addr_hash() helper doing a XOR on all bits
> of an IPv6 address, with an optimized x86_64 version.
[]
> diff --git a/include/net/ipv6.h b/include/net/ipv6.h
[]
> @@ -419,6 +419,19 @@ static inline bool ipv6_addr_any(const struct in6_addr *a)
>  #endif
>  }
>  
> +static inline u32 ipv6_addr_hash(const struct in6_addr *a)
> +{
> +#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
> +	const unsigned long *ul = (const unsigned long *)a;
> +	unsigned long x = ul[0] ^ ul[1];
> +
> +	return x ^ (x >> 32);

Thanks Eric.

Perhaps this would be better with an explicit rather
than implicit cast.


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