Wireshark-dev: Re: [Wireshark-dev] Calling dissector with proto_tree==NULL
From: Jaap Keuter <[email protected]>
Date: Thu, 24 Jan 2008 23:37:13 +0100
Hi Fabrizio,

The proto_tree pointer will be != NULL when the entire tree is needed.
That is not only the case when the packet is selected and the details are displayed, but also when filters are in effect. These filter expressions can only be evaluated when the dissection details are known. Even if you don't have a display filter set the coloring rules are based on display filters and have the same effect.
So, clear out the display filters and disable packet coloring. Then you 
will get proto_tree == NULL and hopefully faster load times.

Fabrizio Bertocci wrote:
I am working on a newer version of the RTPS packet dissector (real- time publisher/subscriber). I have noticed that my packet dissector gets called every time with the proto_tree parameter not NULL, including when the packets are loaded in memory. Unfortunately there are some complex packets that require some heavy computation that should not be necessary unless the packet is selected. As result of this, loading a file (with those packets) takes quite a long time...
The documentation said that wireshark calls the packet dissector with  
proto_tree != NULL only when the entire tree is needed.
Any idea why? Is it something that has changed over the time? Is it  
something I'm doing wrong?
I'm registering the protocol on top of UDP with a simple call to:
heur_dissector_add("udp", dissect_rtps, proto_rtps);

Thanks for any help provided!