netdev - Re: Extending socket timestamping API for NTP

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Message-id: <BBA8C11E-44DF-4693-957F-0354BEC75FC3@me.com>
Date:   Tue, 07 Feb 2017 17:52:52 -0800
From:   Denny Page <dennypage@...com>
To:     "Keller, Jacob E" <jacob.e.keller@...el.com>
Cc:     Miroslav Lichvar <mlichvar@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Richard Cochran <richardcochran@...il.com>,
        Jiri Benc <jbenc@...hat.com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: Extending socket timestamping API for NTP

[Resend without rich text]

> On Feb 07, 2017, at 09:45, Keller, Jacob E <jacob.e.keller@...el.com> wrote:
> 
> The main problem here is that most hardware that *can't* timestamp all packets is pretty limited to timestamping only PTP frames.

Most, but not all. The TI DP83630 doesn’t support timestamping for all packets, but it does support either PTP or NTP:

===
2.3.2.3 NTP Packet Timestamp
The DP83630 may be programmed to timestamp NTP packets instead of PTP packets. This operation is enabled by setting the NTP_TS_EN control in the PTP_TXCFG0 register. When configured for NTP timestamps, the DP83630 will timestamp packets with the NTP UDP port number rather than the PTP port number (note that the device cannot be configured to timestamp both PTP and NTP packets). One-Step operation is not supported for NTP timestamps, so transmit timestamps cannot be inserted directly into outgoing NTP packets. Timestamp insertion is available for receive timestamps but must use a single, fixed location. 
===

Right now, there is no API to signal to the driver that NTP timestamping is desired.

Even if the hardware does not directly support filtering, it can be implemented in the driver.

Denny