Return-path: Received: from mail.eperm.de ([89.247.134.16]:34302 "EHLO mail.eperm.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752360AbcHIJho (ORCPT ); Tue, 9 Aug 2016 05:37:44 -0400 From: Stephan Mueller To: Herbert Xu Cc: "Pan, Miaoqing" , Matt Mackall , "miaoqing@codeaurora.org" , "Valo, Kalle" , "linux-wireless@vger.kernel.org" , ath9k-devel , "linux-crypto@vger.kernel.org" , "jason@lakedaemon.net" , "Sepehrdad, Pouyan" Subject: Re: [PATCH 2/2] ath9k: disable RNG by default Date: Tue, 09 Aug 2016 11:37:39 +0200 Message-ID: <1645997.7cVzaEi3NG@tauon.atsec.com> (sfid-20160809_113747_784363_DCADA41B) In-Reply-To: <20160809091755.GA6370@gondor.apana.org.au> References: <1470726147-30095-1-git-send-email-miaoqing@codeaurora.org> <2569442.q63FVBJjUH@tauon.atsec.com> <20160809091755.GA6370@gondor.apana.org.au> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Sender: linux-wireless-owner@vger.kernel.org List-ID: Am Dienstag, 9. August 2016, 17:17:55 CEST schrieb Herbert Xu: Hi Herbert, > On Tue, Aug 09, 2016 at 11:02:58AM +0200, Stephan Mueller wrote: > > But shouldn't the default of the rngd then be adjusted a bit? > > Please elaborate. in rngd_linux.c:random_add_entropy(void *buf, size_t size): entropy.ent_count = size * 8; entropy.size = size; memcpy(entropy.data, buf, size); if (ioctl(random_fd, RNDADDENTROPY, &entropy) != 0) { ... in rngd.c:do_loop(): retval = iter->xread(buf, sizeof buf, iter); ... rc = update_kernel_random(random_step, buf, iter->fipsctx); where update_kernel_random simply invokes random_add_entropy in chunks. Hence, the rngd reads some bytes from /dev/hwrand and injects it into /dev/ random with an entropy estimate that is equal to the read bytes. With less than perfect noise sources, entropy.ent_count should be much smaller. > > Thanks, Ciao Stephan