From mboxrd@z Thu Jan 1 00:00:00 1970 From: Miroslav Lichvar Subject: Re: [Intel-wired-lan] [RFC v2 net-next 01/10] net: Add a new socket option for a future transmit time. Date: Thu, 18 Jan 2018 09:42:27 +0100 Message-ID: <20180118084227.GL1175@localhost> References: <20180117230621.26074-1-jesus.sanchez-palencia@intel.com> <20180117230621.26074-2-jesus.sanchez-palencia@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, john.stultz@linaro.org, Richard Cochran , jiri@resnulli.us, ivan.briano@intel.com, richardcochran@gmail.com, henrik@austad.us, jhs@mojatatu.com, levi.pearson@harman.com, intel-wired-lan@lists.osuosl.org, xiyou.wangcong@gmail.com, tglx@linutronix.de, anna-maria@linutronix.de To: Jesus Sanchez-Palencia Return-path: Received: from mx1.redhat.com ([209.132.183.28]:43052 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753505AbeARImy (ORCPT ); Thu, 18 Jan 2018 03:42:54 -0500 Content-Disposition: inline In-Reply-To: <20180117230621.26074-2-jesus.sanchez-palencia@intel.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Jan 17, 2018 at 03:06:12PM -0800, Jesus Sanchez-Palencia wrote: > From: Richard Cochran > > This patch introduces SO_TXTIME. User space enables this option in > order to pass a desired future transmit time in a CMSG when calling > sendmsg(2). > > A new field is added to struct sockcm_cookie, and the tstamp from > skbuffs will be used later on. In the discussion about the v1 patchset, there was a question if the cmsg should include a clockid_t. Without that, how can an application prevent the packet from being sent using an incorrect clock, e.g. the system clock when it expects it to be a PHC, or a different PHC when the socket is not bound to a specific interface? At least in some applications it would be preferred to not sent a packet at all instead of sending it at a wrong time. Please keep in mind that the PHCs and the system clock don't have to be synchronized to each other. If I understand the rest of the series correctly, there is an assumption that the PHCs are keeping time in TAI and CLOCK_TAI can be used as a fallback. -- Miroslav Lichvar