Wireshark mailing list archives

Re: tshark: Difference between -R and -Y


From: Joerg Mayer <jmayer () loplof de>
Date: Wed, 8 Jan 2014 01:22:43 +0100

On Sun, Jan 05, 2014 at 07:30:04PM -0500, Evan Huus wrote:
Live capture with two-pass dissection is effectively undefined
behaviour at this point (I'm surprised you're seeing any packets at
all to be honest).

Ah, OK. As some "invalid" cases (-R without -2) are rejected I expected
that this was a valid combination.

Everything should work as expected when reading from a capture file.

It does.

Thanks!
    Jörg

On Sun, Jan 5, 2014 at 4:21 PM, Joerg Mayer <jmayer () loplof de> wrote:
I just found out that I don't understand what -R does.

If I run
tshark -2 -R "udp.port==53" -i wlan0
then it seems that I see all packets (arp, dns, lldp, ...)
if I instead run
tshark -2 -Y "udp.port==53" -i wlan0
I only see dns.
The manpage is not helpful either to explain what I am seeing
(snv HEAD / r54612)

Can someone please explain what is going on here?

-- 
Joerg Mayer                                           <jmayer () loplof de>
We are stuck with technology when what we really want is just stuff that
works. Some say that should read Microsoft instead of technology.
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