Wireshark-dev: Re: [Wireshark-dev] Conversation tracking
From: Stephen Fisher <[email protected]>
Date: Fri, 11 May 2012 09:46:45 -0600
---- On Fri, 11 May 2012 08:30:03 -0600 Tobias Weiss  wrote ---- 

>
>Right now I'm puzzled: I wanted to use conversation tracking in order to save information about the state of the communication across packet dissection. 
> 
>The dissector is called completely out of order (which is reasonable) but I get always the same conversation, even when dissecting an older packet than the last one. So saving the state of the communication is completely pointless if the same conversation is used for dissecting random packets. Here is an example just in case you don't understand my possibly weird English ;-) 
> 
>I have a stream of 10 packets and something interesting was send in packet number 3. Now I want to save this information in the conversations data in order to reuse it when dissecting future packets. But the dissector is called randomly (which is ok) but always with the same conversation (which is absolutely not ok in this case). 
> 
>I simply cannot rely on the saved information. So how am I supposed to use conversation tracking in a sane way (as far as I can see I can't _track_ anything)??? 

Are you trying to keep track of where the current packet belongs in the whole conversation?  The exec dissector I previously mentioned (packet-exec.c) does this.  Look at the exec_hash_entry_t struct up toward the top.  A more advanced (overly complex) version of this is in the VNC dissector (packet-vnc.c).  In the VNC dissector, we use both per conversation data (such as conversation_add_proto_data) and per packet info (such as p_get_proto_data).