Denis Ovsienko <de...@ovsienko.info> wrote on Sun,  5 Aug 2018
at 17:05:20 +0100 in 
<1650ad5fd29.b5d2798f311917.536858429581803...@ovsienko.info>:

> It works in an interactive session; but as soon as the output makes
> it to the Internet and stays there long enough, people will no
> longer understand what the printed time was in their local time or
> UTC. The value of TZ influences the output, but remains invisible.

I think this is not a real problem; in practice it's rare that long-lived 
non-.pcap tcpdump decodings have significant meaning associates with the time 
zone of time outputs from printers. One could imagine printing the local time 
zone adjacent to the "listening on" output at startup, but it seems unnecessary.

But it's important not to let theoretical issues make the tool worse for actual 
users.

> I understand what you are suggesting, and your description is
> correct, but it does not solve the problem of interpreting tcpdump
> output correctly in a place or time different from the
> original. That said, I can live with print-rx.c using local time and
> being imperfect, it has worked like this many years. Still, I think
> local time should not be the norm for other decoders.

Doesn't this argument apply for other decoders as well? Whatever is done should 
not make the output of decoders harder for the diagnostic users of tcpdump to 
interpret, or unnecessarily change the output format.

One could imagine having all of these printers respect -tt, &c., and 
conceivably adding an option to force decoder time printing to be UTC; but such 
an option would be tantamount to setting TZ=UTC, and generally the Unix Way is 
not to duplicate such OS functionality.

p.s.: Using GMT or GMT0 is deprecated, please use UTC instead.

--jh...@mit.edu
  John Hawkinson
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