netdev - Re: [PATCH] ipv6: use a stronger hash for tcp

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Date:	Thu, 21 Feb 2013 18:18:22 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org, ncardwell@...gle.com, ycheng@...gle.com
Subject: Re: [PATCH] ipv6: use a stronger hash for tcp

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Thu, 21 Feb 2013 14:18:52 -0800

> From: Eric Dumazet <edumazet@...gle.com>
> 
> It looks like its possible to open thousands of TCP IPv6
> sessions on a server, all landing in a single slot of TCP hash
> table. Incoming packets have to lookup sockets in a very
> long list.
> 
> We should hash all bits from foreign IPv6 addresses, using
> a salt and hash mix, not a simple XOR.
> 
> inet6_ehashfn() can also separately use the ports, instead
> of xoring them.
> 
> Reported-by: Neal Cardwell <ncardwell@...gle.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied, and queued up for -stable, thanks Eric.

I bet we can consolidate this slightly, to make it less
expensive yet not give up much in terms of protection.  Two
jhash3word()'s is quite a lot.
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