netdev - Re: [patch 0/3] ptp: Provide support for auxiliary clocks for PTP_SYS_OFFSET

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87y0tepcyx.ffs@tglx>
Date: Thu, 26 Jun 2025 20:36:06 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Miroslav Lichvar <mlichvar@...hat.com>
Cc: LKML <linux-kernel@...r.kernel.org>, netdev@...r.kernel.org, Richard
 Cochran <richardcochran@...il.com>, Christopher Hall
 <christopher.s.hall@...el.com>, John Stultz <jstultz@...gle.com>, Frederic
 Weisbecker <frederic@...nel.org>, Anna-Maria Behnsen
 <anna-maria@...utronix.de>, Werner Abt <werner.abt@...nberg-usa.com>,
 David Woodhouse <dwmw2@...radead.org>, Stephen Boyd <sboyd@...nel.org>,
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>, Kurt
 Kanzenbach
 <kurt@...utronix.de>, Nam Cao <namcao@...utronix.de>, Antoine Tenart
 <atenart@...nel.org>
Subject: Re: [patch 0/3] ptp: Provide support for auxiliary clocks for
 PTP_SYS_OFFSET_EXTENDED

On Thu, Jun 26 2025 at 16:53, Miroslav Lichvar wrote:
> On Thu, Jun 26, 2025 at 03:27:28PM +0200, Thomas Gleixner wrote:
>> This is obviously incomplete as the user space steering daemon needs to be
>> able to correlate timestamps from these auxiliary clocks with the
>> associated PTP device timestamp. The PTP_SYS_OFFSET_EXTENDED IOCTL command
>> already supports to select clock IDs for pre and post hardware timestamps,
>> so the first step for correlation is to extend that IOCTL to allow
>> selecting auxiliary clocks.
>
>> Miroslav: This branch should enable you to test the actual steering via a
>> 	  PTP device which has PTP_SYS_OFFSET_EXTENDED support in the driver.
>
> Nice! I ran few quick tests and it seems to be working great. The
> observed delay and stability with an AUX clock synchronized to a PHC
> seems to be the same as with CLOCK_REALTIME.

Thank you for taking the time!

> Are there any plans to enable software timestamping of packets by
> AUX clocks?

I'm not aware of any plans or efforts so far, but obviously that'd be
the next logical step.

> That would allow an NTP/PTP instance using SW timestamps
> to be fully isolated from the adjustments of the CLOCK_REALTIME clock,
> e.g. to run an independent NTP/PTP server in a container. This might
> be tricky as the skb would likely need to contain the MONOTONIC_RAW
> timestamp to be converted later when it gets to a socket, so some
> history of adjustments of each clock would need to be saved and
> reapplied to the raw timestamp.

Either that or you could go and implement some BPF magic to take a
timestamp with a particular clock ID based on the packet type. But what
do I know? That's something the network wizards needs to figure out.

Thanks,

        tglx