netdev - Re: [PATCH net] Revert "tcp: switch tcp_fastopen key generation to net_get_random

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Message-id: <20150618154529.GG33243@Chimay.local>
Date:	Thu, 18 Jun 2015 08:45:29 -0700
From:	Christoph Paasch <cpaasch@...le.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	netdev@...r.kernel.org, David Miller <davem@...emloft.net>
Subject: Re: [PATCH net] Revert
 "tcp: switch tcp_fastopen key generation to net_get_random_once"

On 18/06/15 - 04:14:13, Eric Dumazet wrote:
> On Thu, 2015-06-18 at 11:32 +0200, Hannes Frederic Sowa wrote:
> > > There does not seem to be a better way to handle this. We could try
> > > to make the call to kmalloc and crypto_alloc_cipher during bootup, and
> > > then generate the random value only on-the-fly (when the first TFO-SYN
> > > comes in) with net_get_random_once in order to have the better entropy
> > > that comes with doing the late initialisation of the random value. But
> > > that's probably net-next material.
> > 
> > can't we simply move the net_get_random_once to the TCP_FASTOPEN setsockopt and
> > sendmsg(MSG_FASTOPEN) path, so those allocations still happen in process context
> > but we still defer the extraction of entropy as long as posible?
> 
> Yes, I do not think this would be hard. This bug is old (3.13) and does
> not seem very urgent to expedite a revert.

True, it would be simpler to call tcp_fastopen_init_key_once to the
setsocketopt() and inet_listen().

I will resubmit.


Christoph

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