On Wed, Jan 17, 2018 at 03:06:12PM -0800, Jesus Sanchez-Palencia wrote: > From: Richard Cochran <rcoch...@linutronix.de> > > 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
