From mboxrd@z Thu Jan 1 00:00:00 1970 From: Miroslav Lichvar Date: Tue, 13 Feb 2018 10:56:52 +0100 Subject: [Intel-wired-lan] [RFC v2 net-next 01/10] net: Add a new socket option for a future transmit time. In-Reply-To: References: <20180117230621.26074-1-jesus.sanchez-palencia@intel.com> <20180117230621.26074-2-jesus.sanchez-palencia@intel.com> <20180118084227.GL1175@localhost> Message-ID: <20180213095652.GA11459@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: intel-wired-lan@osuosl.org List-ID: On Mon, Feb 12, 2018 at 02:39:06PM -0800, Jesus Sanchez-Palencia wrote: > On 01/18/2018 12:42 AM, Miroslav Lichvar wrote: > > 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. > > Just to double-check, imagine that I've configured the qdisc for > SW best-effort and with clockid CLOCK_REALTIME. When it receives a > packet with the clockid of a /dev/ptpX, the qdisc should just drop that > packet, right? Yes, I think it should drop it. The kernel does not know the offset between the two clocks (they don't even have to be synchronized), so it cannot convert a PHC-based TX time to the system time. -- Miroslav Lichvar