> On Feb 07, 2017, at 06:01, Miroslav Lichvar <mlich...@redhat.com> wrote: > > 1) new rx_filter for NTP > > Some NICs can't timestamp all received packets and are currently > unusable for NTP with HW timestamping. The new filter would allow > NTP support in new NICs and adding support to existing NICs with > firmware/driver updates. The filter would apply to IPv4 and IPv6 > UDP packets received from or sent to the port number 123. >
I think this is a good idea. Even if the hardware doesn’t support it, the filtering could be done in the kernel. Save a huge number of context switches. > 4) allow sockets to use both SW and HW TX timestamping at the same time > > When using a socket which is not bound to a specific interface, it > would be nice to get transmit SW timestamps when HW timestamps are > missing. I suspect it's difficult to predict if a HW timestamp will > be available. Maybe it would be acceptable to get from the error > queue two messages per transmission if the interface supports both > SW and HW timestamping? > Highly agreed. The current interface pretty much forces a socket per physical interface, which should not be necessary. > 5) new SO_TIMESTAMPING options to get transposed RX timestamps > > PTP uses preamble RX timestamps, but NTP works with trailer RX > timestamps. This means NTP implementations currently need to > transpose HW RX timestamps. The calculation requires the link speed > and the length of the packet at layer 2. It seems this can be > reliably done only using raw sockets. It would be very nice if the > kernel could tranpose the timestamps automatically. > > The existing SOF_TIMESTAMPING_RX_HARDWARE flag could be aliased to > SOF_TIMESTAMPING_RX_HARDWARE_PREAMBLE and the new flag could be > SOF_TIMESTAMPING_RX_HARDWARE_TRAILER. > > PTP has a similar problem with SW RX timestamps, which are closer > to the trailer timestamps rather than preamble timestamps. A new > SOF_TIMESTAMPING_RX_SOFTWARE_PREAMBLE flag could be added for PTP > implementations to get transposed timestamps in order to improve > accuracy. > Also highly agreed. Denny
