[Ntp] Antw: [EXT] Re: RFC 8633 (NTP BCP), Appendix A: "restrict source ..."

Ulrich Windl <Ulrich.Windl@rz.uni-regensburg.de> Tue, 06 July 2021 12:09 UTC

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Date: Tue, 06 Jul 2021 14:09:08 +0200
From: "Ulrich Windl" <Ulrich.Windl@rz.uni-regensburg.de>
To: <martin.burnicki@meinberg.de>
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Subject: [Ntp] Antw: [EXT] Re: RFC 8633 (NTP BCP), Appendix A: "restrict source ..."
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>>> Martin Burnicki <martin.burnicki@meinberg.de> schrieb am 06.07.2021 um
10:55 in
Nachricht <db655230-f6dd-322c-6837-606280cddceb@meinberg.de>de>:
> Hi Ulrich,
> 
> Ulrich Windl wrote:
>> Hi!
>> 
>> Reading RFC 8633, Appendix A, specifically A.2, I was confused a bit:
>> The last line says "restrict source..." (and the preceding lines had 
> "restrict default...").
>> The point is that "default" is a literal keyword, but "source" is not 
> (AFAIK).
> 
> Yes, "restrict source ..." it valid syntax, which has been introduced 
> int ntpd 4.2.8, if I remember correctly.

Sorry for that. I looked up "man ntpd.conf" for ntp-4.2.8p15-94.2.x86_64 of
SLES 12 and there "source" is not explained.


> 
> The HTML docs of the current ntpd distribution says (in access.html):
> 
> "restrict source" configures a template restriction automatically added 
> at runtime for each association, whether configured, ephemeral, or 
> preemptable, and removed when the association is demobilized.
> 
> If I remember correctly, this was introduced to fix a problem e.g. with 
> pool server entries. If you had a restrict line like
> 
> restrict default ... nopeer
> 
> then automatic associations e.g. due to the "pool" directive wasn't 
> possible.
> 
> restrict source ...
> 
> now adds the specified permissions to such associations that are created 
> automatically.

OK, but still an explaining sentence wouldn't have been that wrong ;-)

Regards,
Ulrich

> 
> 
> Martin
> -- 
> Martin Burnicki
> 
> Senior Software Engineer
> 
> MEINBERG Funkuhren GmbH & Co. KG
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