Tshark: proto_tree not created on first pass - Tap not the answer

[Paul Offord <Paul.Offord () advance7 com>]

Although TRANSUM had a fake tap listener, it didn't include a packet callback pointer it was just set to NULL.  I've 
added a dummy packet callback and discovered that the use of the tap mechanism isn't going to fix the Tshark issue.

When used with Wireshark, the packet callback gets called for every packet on the first pass and every packet on 
subsequent passes.  That sounds good.  When used with Tshark, the packet callback only gets called on the second pass 
(when using the -2 command line option).  

-----Original Message-----
From: wireshark-dev-bounces () wireshark org [mailto:wireshark-dev-bounces () wireshark org] On Behalf Of Guy Harris
Sent: 13 February 2017 03:55
To: Developer support list for Wireshark <wireshark-dev () wireshark org>
Subject: Re: [Wireshark-dev] Tshark: proto_tree not created on first pass with tap defined

The underlying problem here appears to be that the TRANSUM post-dissector is not only adding stuff to the protocol 
tree, which obviously doesn't need to be done if there is no protocol tree, but is also doing *analysis* of the packet 
information.

The latter of those should *not* be done in a dissector - it should be done in a tap.

Unfortunately, *currently*, taps are run after all dissectors, including post-dissectors, are run, which might not work 
for this purpose.  If so, what we probably would need here is to have a mechanism to allow taps to be run "early".  For 
now, we could define "early" as "before the post-dissectors are run".
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