Wireshark mailing list archives
Re: Display more digits for NTP packet's root dispersion
From: Martin Burnicki <martin.burnicki () meinberg de>
Date: Wed, 8 Aug 2018 09:38:14 +0200
Guy Harris wrote:
On Aug 6, 2018, at 2:19 PM, Guy Harris <guy () alum mit edu> wrote:On Aug 6, 2018, at 4:20 AM, Martin Burnicki <martin.burnicki () meinberg de> wrote:As far as I have seen, proto_tree_add_double() seems to add a double value to the output tree,*All* doubles use the same format string. The part of the format string for the number is
This doesn't seem to be quite correct. At least the peer clock precision, which is an 8 bit integer in the packet is displayed with a fixed floating point format with 6 fractional digits, e.g. (from different packets): Peer Clock Precision: 0.000977 sec Peer Clock Precision: 0.000004 sec This is very clear, IMO.
"%." G_STRINGIFY(DBL_DIG) "g" DBL_DIG is 15 with macOS/Xcode, so that should be %.15g, which should show more than 4 digits.At least on macOS, a root delay the octets of which are 0x00 0x00 0x00 0x01 displays, in the dissected NTP packet, as Root Delay: 1.52587890625e-05 seconds Does it not do that on your machine?
I've investigated a little bit more, and in fact it turned out that I've been using an old version of Wireshark which displayed the root dispersion in a fixed format 0.0000 s. Same seems to be the case for a customer with whom I've discussed a root dispersion issue, and who told me the root dispersion he saw was 0 in the Wireshark capture, even though it was not really 0, but just very small. After I've updated Wireshark to the current version I can confirm that both the root delay and the root dispersion are now shown in an "automatic" floating point format, e.g. (from different packets): Root Delay: 0 seconds Root Delay: 0.0009765625 seconds Root Delay: 0.0035552978515625 seconds Root Dispersion: 7.62939453125e-005 seconds Root Dispersion: 0.0001983642578125 seconds Root Dispersion: 0.944107055664063 seconds Root Dispersion: 0.0693359375 seconds This avoids displaying a value as 0 when in fact it is very small, but not 0. However, on the other hand - it's harder to compare values when you quickly inspect different packets - it may pretend a much higher resolution (10 or even more fractional digits of a second) even if the resolution in the protocol is limited. E.g. 1 LSB of the root dispersion is ~15 microseconds, so it doesn't make much sense to display femtoseconds with random numbers from the scaling. So IMO it would make more sense to display such values with a fixed floating point format similar to the Peer Clock Precision field, e.g. 0.000000 instead of 0 0.944107 instead of 0.944107055664063 0.000076 instead of 7.62939453125e-005 Just my thoughts, though. Martin -- Martin Burnicki Senior Software Engineer MEINBERG Funkuhren GmbH & Co. KG Email: martin.burnicki () meinberg de Phone: +49 5281 9309-414 Linkedin: https://www.linkedin.com/in/martinburnicki/ Lange Wand 9, 31812 Bad Pyrmont, Germany Amtsgericht Hannover 17HRA 100322 Geschäftsführer/Managing Directors: Günter Meinberg, Werner Meinberg, Andre Hartmann, Heiko Gerstung Websites: https://www.meinberg.de https://www.meinbergglobal.com Training: https://www.meinberg.academy ___________________________________________________________________________ Sent via: Wireshark-dev mailing list <wireshark-dev () wireshark org> Archives: https://www.wireshark.org/lists/wireshark-dev Unsubscribe: https://www.wireshark.org/mailman/options/wireshark-dev mailto:wireshark-dev-request () wireshark org?subject=unsubscribe
Current thread:
- Display more digits for NTP packet's root dispersion Martin Burnicki (Aug 06)
- Re: Display more digits for NTP packet's root dispersion Dario Lombardo (Aug 06)
- Re: Display more digits for NTP packet's root dispersion Martin Burnicki (Aug 06)
- Re: Display more digits for NTP packet's root dispersion Dario Lombardo (Aug 06)
- Re: Display more digits for NTP packet's root dispersion Martin Burnicki (Aug 08)
- Re: Display more digits for NTP packet's root dispersion Peter Wu (Aug 08)
- Re: Display more digits for NTP packet's root dispersion Martin Burnicki (Aug 06)
- Re: Display more digits for NTP packet's root dispersion Guy Harris (Aug 06)
- Re: Display more digits for NTP packet's root dispersion Guy Harris (Aug 07)
- Re: Display more digits for NTP packet's root dispersion Martin Burnicki (Aug 08)
- Re: Display more digits for NTP packet's root dispersion Dario Lombardo (Aug 08)
- Re: Display more digits for NTP packet's root dispersion Martin Burnicki (Aug 09)
- Re: Display more digits for NTP packet's root dispersion Dario Lombardo (Aug 06)