Wireshark mailing list archives
Re: Time Zone effect in Timestamps of Pcap
From: Guy Harris <guy () alum mit edu>
Date: Sun, 30 Oct 2011 13:07:37 -0700
On Oct 30, 2011, at 12:48 PM, Dale McCoy wrote:
Unless I miss my guess, the pcap has timestamps stored in UTC.
Correct: $ man pcap-savefile PCAP-SAVEFILE(5) PCAP-SAVEFILE(5) NAME pcap-savefile - libpcap savefile format DESCRIPTION NOTE: applications and libraries should, if possible, use libpcap to read savefiles, rather than having their own code to read savefiles. If, in the future, a new file format is supported by libpcap, applica- tions and libraries using libpcap to read savefiles will be able to read the new format of savefiles, but applications and libraries using their own code to read savefiles will have to be changed to support the new file format. ... Following the per-file header are zero or more packets; each packet begins with a per-packet header, which is immediately followed by the raw packet data. The format of the per-packet header is: +---------------------------------------+ | Time stamp, seconds value | +---------------------------------------+ | Time stamp, microseconds value | +---------------------------------------+ | Length of captured packet data | +---------------------------------------+ |Un-truncated length of the packet data | +---------------------------------------+ All fields in the per-packet header are in the byte order of the host writing the file. The per-packet header begins with a time stamp giv- ing the approximate time the packet was captured; the time stamp con- sists of a 4-byte value, giving the time in seconds since January 1, 1970, 00:00:00 UTC, followed by a 4-byte value, giving the time in microseconds since that second. Following that are a 4-byte value giv- ing the number of bytes of captured data that follow the per-packet header and a 4-byte value giving the number of bytes that would have been present had the packet not been truncated by the snapshot length. The two lengths will be equal if the number of bytes of packet data are less than or equal to the snapshot length.
You can set Wireshark to display UTC timestamps, regardless of the local timezone, but I'm not aware of any way to force Wireshark to display any particular (other, i.e. non-zero) timezone offset.
On UN*X systems, you can run Wireshark with the TZ environment variable set to refer to the other time zone - note that a time zone may have more than just an offset, it may have an offset that changes over time, due to daylight savings time/summer time or due to the region changing its offset for other reasons. ___________________________________________________________________________ Sent via: Wireshark-users mailing list <wireshark-users () wireshark org> Archives: http://www.wireshark.org/lists/wireshark-users Unsubscribe: https://wireshark.org/mailman/options/wireshark-users mailto:wireshark-users-request () wireshark org?subject=unsubscribe
Current thread:
- Time Zone effect in Timestamps of Pcap NITIN GOYAL (Oct 30)
- Re: Time Zone effect in Timestamps of Pcap Dale McCoy (Oct 30)
- Re: Time Zone effect in Timestamps of Pcap Guy Harris (Oct 30)
- Re: Time Zone effect in Timestamps of Pcap Jeff Morriss (Oct 31)
- Re: Time Zone effect in Timestamps of Pcap Guy Harris (Oct 30)
- Re: Time Zone effect in Timestamps of Pcap Dale McCoy (Oct 30)