Re: [chrony-users] Interop with NTP version 1 and 4 clients

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So, my suspicion is that the software is very badly written. It looks for the
ntp V4 in the packet and rejects it if it is not there, even though ntpV4
packets are supposed to be the same as V3 (backward compatible).

a) complain to the phone software writers.

b) have chrony put in a fake V4 flag into the packet so as to fool the broken
phone software.

As written chrony accepts V2-V4 packets. It reports V3 because its analysis is
closest to v3 ( but still pretty far away). It does not deliver Kiss of Death
packets (V4)

On Tue, 19 Feb 2013, Benny Lyne Amorsen wrote:

tir, 19 02 2013 kl. 08:31 -0800, skrev Bill Unruh:

On Tue, 19 Feb 2013, Benny Lyne Amorsen wrote:

Chrony is working very well as an NTP server (not a stratum 1 of

Chrony works perfectly well as a stratum 1-- just use refclock of say a gps
pps source.

I didn't realize that chrony had PPS support. Excellent.

Yes, it is somewhat limited ( although you can get it to simply use the
refclock part of ntpd as well) but certainly works.

What version of chrony are you using?


No idea about this. As far as I know sntp uses exactly the same packets as
does full ntpd. get a better app.

Yes well, getting a better app is an uphill battle. LG phones send SNTP
only. tcpdump shows the packets as NTPv1, and chrony ignores them.

Not at all sure what v1 is, or how its packets differ. SNTP is a V3 and V4
packets AFAIK. (certainly described in their rfcs.)

You could change the NTPD_MIN_VERSION flags defined in ntp_client.c and in
acquire.c to 1 rather than 2 (actually I would probably leave aquire.c alone
as that seems to be primarily for getting time from other machines (acting as
a client) rather then acting as a server. I also suspect that they are actually sending out
version 3 or 4 packets anyway, not version 1 but had no idea what the
"version" field was actually for. Of course this may break things
if it is actually sending out V1 packets. (Note that has nothing to do with
SNTP since SNTP is version 3 or 4 as well.)

I am suprised that anything accepts version 1 anymore.

Here is the tcpdump of a client indicating NTPv4 but receiving an NTPv3
answer. The client then proceeds to ignore that answer and repeats the

What software is being used by the client?

Good question. Aastra phones are the clients. They work with (and are
probably only tested against) ntp 4.2.x.

And probably written by some poor new graduate who had no idea what ntp was
before he was told to write an app. for the phone.

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