tcpdump mailing list archives
Re: local timestamp recovery of .cap files
From: Guy Harris <guy () alum mit edu>
Date: Fri, 15 May 2009 11:20:11 -0700
On May 15, 2009, at 12:43 AM, Jefferson Ogata wrote:
This has come up before, back when we were talking about the NG format.I guess I got confused by the current context; if pcap files are natively UTC (which I had thought they were until this thread arose, seeming to suggest they weren't), great.
They are.The issue in the thread is how to *display* the time stamps, especially if you want to know what *local* time, at the point of capture, a packet arrived, when you're reading it in a different time zone. *That* requires that some form of time zone information for the point of capture be available, whether in the capture file or, for example, in an email to which the capture file was attached. So there's a use for time zone information in a capture file even when the time stamps in the capture file are in UTC.
I configure all my systems in UTC anyway, so I never have issues, and I wouldn't be able to tell without tweaking $TZ.Frankly, I don't understand why anyone configures a UNIX-like system inanything other than UTC. That's what $TZ is for.
There are two ways I see in which "configure a UNIX-like system for a particular time zone" could be read:
1) set the default time zone used by routines such as localtime() and mktime() to convert UTC to local time;
2) set the time zone of the value returned by time()/gettimeofday()/ etc..
2) makes no sense whatsoever, as time()/gettimeofday()/etc. are *defined* to return UTC-based values.
1) makes perfect sense, unless you want the date command, the time stamps in log files, whatever clock is displayed in the GUI, etc. to show UTC rather than local time. Some people might want that, but that's not *ipso facto* what *everybody* should want.
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Current thread:
- local timestamp recovery of .cap files Andrej van der Zee (May 14)
- Re: local timestamp recovery of .cap files Guy Harris (May 14)
- Re: local timestamp recovery of .cap files Andrej van der Zee (May 14)
- Re: local timestamp recovery of .cap files Guy Harris (May 14)
- Re: local timestamp recovery of .cap files Jefferson Ogata (May 14)
- Re: local timestamp recovery of .cap files Guy Harris (May 14)
- Re: local timestamp recovery of .cap files Andrej van der Zee (May 14)
- Re: local timestamp recovery of .cap files Guy Harris (May 14)
- Re: local timestamp recovery of .cap files Jefferson Ogata (May 15)
- Re: local timestamp recovery of .cap files Guy Harris (May 15)
- Re: local timestamp recovery of .cap files rh (May 15)
- Re: local timestamp recovery of .cap files Jefferson Ogata (May 15)
- Re: local timestamp recovery of .cap files Andrej van der Zee (May 14)
- Re: local timestamp recovery of .cap files Guy Harris (May 14)