Wireshark-dev: Re: [Wireshark-dev] pcap-ng support
From: Ulf Lamping <[email protected]>
Date: Tue, 22 Jan 2008 11:00:25 +0100
Gianluca Varenni schrieb:
I just uploaded a new version of the spec here

http://www.winpcap.org/ntar/draft/PCAP-DumpFileFormat_ts.html

I tried to spedify the timestamps better and renamed if_tsaccur into if_tsresol.
Let me know if you think it makes more sense.
Yes it does, however still can be improved IMHO :-)

I would refer to "Unix time" only if it really represents the *seconds* til 1/1/1970 - and this isn't the case here. I wouldn't repeat the whole if_tsresol description here (to avoid duplication and the field description is already pretty long).

"Timestamp (High) and Timestamp (Low): high and low 32-bits of a 64-bit quantity representing the timestamp. The timestamp is a single 64-bit unsigned integer representing the number of units since 1/1/1970. The unit of this field is specified by the 'if_tsresol' option (see Figure 9 (Interface Description Block format.) <http://www.winpcap.org/ntar/draft/PCAP-DumpFileFormat_ts.html#formatidb>) of the Interface Description block referenced by this packet. E.g. if the value of 'if_tsresol' is 9, the unit is 10^-9 nanoseconds, so the 64-bit timestamp is simply the number of nanoseconds since 1/1/1970. Please note that differently from the libpcap file format, timestamps are not saved as two 32-bit values accounting for the seconds since 1/1/1970 and microseconds of the day. They are a single 64-bit quantity saved as two 32-bit words."

I guess in future we will need a new field in IDB, something like "if_tsformat" (or so) to specify libpcap like or completely different timestamp formats - I guess that's the same conclusion Stephen Donelly may have. But we can do this later when the problem really arises ;-)
Regards, ULFL