netdev - Re: [RFC] tcp: randomize TCP source ports

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Message-ID: <1383923478.9412.240.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Fri, 08 Nov 2013 07:11:18 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>
Subject: Re: [RFC] tcp: randomize TCP source ports

On Fri, 2013-11-08 at 15:28 +0100, Hannes Frederic Sowa wrote:

> What do you think about using a timer to keep the reseed out of fast-path
> and switch to the non-arch get_random_bytes instead?

Well, the initial seed value is get_random_bytes(). I felt that using a
xor with the _arch() version would be safe enough.

For the timer, I do not think its worth the pain : Do you want a per cpu
timer, or a global one ?

The unlikely() clause makes the test very small and test is well
predicted.

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