netdev - Re: [PATCH 2/2] rps: changes to bnx2x to get device hash

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Date:	Wed, 11 Nov 2009 18:42:09 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	mcarlson@...adcom.com
Cc:	therbert@...gle.com, netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] rps: changes to bnx2x to get device hash

From: "Matt Carlson" <mcarlson@...adcom.com>
Date: Wed, 11 Nov 2009 15:21:03 -0800

> Is a random hash key really better than arbitrary static values?  
> Setting the hash key to random values means, from chip reset to chip
> reset, you could get different performance results.  Unless we
> we understood how the key affects performance, I would think that
> reproducable performance numbers would be more desirable, no?

Security.

If someone knows the key and the hash function, they can purposely
pick address and port combinations that always hash to the same queue,
decresing your horsepower to handle traffic by orders of magnitude.
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