Re: Inconsistent availability of proto_tree values during the first of two passes

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

OK - So just to summarize, we need to:



  1.  Short Term - Add a flag somewhere that can be set by a dissector, post-dissector or tap to request that a 
proto_tree is produced on the first pass
  2.  Long Term - Add a facility that allows a dissector, post-dissector or tap to request a list of specific protocol 
field values values during the first pass



Is that right?



-----Original Message-----
From: wireshark-dev-bounces () wireshark org [mailto:wireshark-dev-bounces () wireshark org] On Behalf Of Guy Harris
Sent: 11 April 2017 04:25
To: Developer support list for Wireshark <wireshark-dev () wireshark org>
Subject: Re: [Wireshark-dev] Inconsistent availability of proto_tree values during the first of two passes



On Apr 10, 2017, at 3:04 PM, Paul Offord <Paul.Offord () advance7 com<mailto:Paul.Offord () advance7 com>> wrote:



> > If a tree isn't being generated, because it isn't necessary (e.g., if the code calling the dissectors is only trying 
> > to get the column contents) there's presumably no need for TRANSUM - or any other dissector or post-dissector - to 
> > add anything to the non-existent tree.

>

> Agreed, except in the case of TRANSUM the user will probably want to add a TRANSUM-computed value as a column.  For 
> example, if you use tshark to just output the Packet List entries (summary lines) it's likely that TRANSUM-computed 
> values would be included in that listing.



That's not a TRANSUM-specific issue.  If the user wants to use *any* custom columns, from *any* dissector or 
post-dissector field, the protocol tree currently has to be generated - and, given that custom columns work, we 
*already* arrange to construct the protocol tree whenever we're asking for columns and at least one column is a custom 
column (see various calls to have_custom_cols()), so if the code calling the dissectors is only trying to get the 
column contents *but* at least one column is a custom column, the tree will be constructed.



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