Wireshark · Wireshark-dev: Re: [Wireshark-dev] Dissector global variable

[Jeff Morriss <jeff.morriss.ws@xxxxxxxxx>]

Hans Glück wrote:
> Hello, 
>
> I´m writing a dissector and I want to implement "error recovery mode"/"flow control", therefor I need two gloabl variables where I can store some values (-> "next_expected_frame_to_be_recieved" and "next_expected_frame_to_be_send"). 
> I declared them at the beginning of my c-file: 
> static guint8 next_expected_frame_to_be_recieved = 0; 
> static guint8 next_expected_frame_to_be_send = 0; 
>
> And I set value of this variables in my dissector code: 
> static void dissect_mux27010(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree){ 
>     ... 
>     if (received_successful()) { 
>         next_expected_frame_to_be_recieved++; 
>     } 
>     ... 
> } 
>
> My problem is: Every time I click in Wireshark at packet the value is increased e.g. 
> click first packet -> next_expected_frame_to_be_recieved == 1 
> click second packet -> next_expected_frame_to_be_recieved == 2 
> click first packet -> next_expected_frame_to_be_recieved == 3 
> click second packet -> next_expected_frame_to_be_recieved == 4 
>
> But what I want is that the variables are increased step-by-step/ ordered (if packet n is an ACK -> increase; if packet n+1 is an ACK -> increase...) 
> How can I realize this? 

You might want to look at the variable pinfo->fd->flags.visited .  My 
(limited) understanding is it is set to 0 only the first time a 
particular frame is given to your dissector (after a file load/reload).