Re: wireshark GUI vs tshark

[Jaap Keuter <jaap.keuter () xs4all nl>]

Hi Brian,

"This is my development code" is not an excuse. Cut away the crap, or
structure it.

"You forget to set initialized to TRUE in your handoff functions." means
the in your handoff routines you have a semaphore, but you never set it to
TRUE, even if the code has already executed. Next time handoff is called
the code runs again. So, at the end set the semaphore.

Accessing tvbuff like this is a problem. You have absolutely NO guarantee
that you can access the data this way. You WILL have array overruns,
problems with composite TVBs, etc, etc.
We have painstakingly provided you with a whole series of safe access
functions to handle everything you want to do in a single statement. Did I
already mention these are safe methods? No buffer overruns? With exception
handling build in? 

"I am a java programmer and just started to dig into this C stuff". I
would say welcome to the bear metal. No more handholding and sandboxing
here..... doc/README.developer is your friend.

Thanks,
Jaap

On Tue, 24 Nov 2009 10:59:28 -0500, Brian Oleksa
<oleksab () darkcornersoftware com> wrote:
> Jaap and Chris
>
> I appreciate your help.
> I apologize for the messy code....this is my development code.
>
> I have changed some of the code based on your suggestions that you made 
> below: Such as...
>
> FT_BYTES, BASE_HEX is now FT_BYTES, BASE_NONE
> I have closed off the value_string helen_vals[] with {0, NULL}
>
> However.. I do have some questions.
>
> What do you mean when you say:  "You forget to set initialized to TRUE
in
> your handoff functions."
>
> Also..why does accessing tvbuff this way pose a problem..??    guint8 *
> ptr = (guint8*) tvb->real_data;
> Accessing tvbuff this way appears to be working fine...but would like
some
> feed back if there is a well-known & correct way to do this.
>
> I have attached a clean version of the code. It is now formatted and all

> the old commented out code is now removed.
>
> I am a java programmer and just started to dig into this C stuff....So I

> apologize for any code that does not make sense.
>
> Again...any help is greatly appreciated.
>
> Thanks,
> Brian
>
>
>
> Jaap Keuter wrote:
> > Hi,
> >
> > Oke, quick review then.
> >
> > First of all the code is a mess. That results in:
> > 1. hard to look through.
> > 2. hard to spot even obvious errors.
> >
> > You forget to set initialized to TRUE in your handoff functions.
> >
> >   FT_BYTES, BASE_HEX should be FT_BYTES, BASE_NONE
> >
> > Many inconsistencies in header blubs and labels.
> >
> > value_string helen_vals[] isn't closed off by {0, NULL}
> >
> >              guint8 * ptr = (guint8*) tvb->real_data;
> > Going about this way of accessing tvbuff data leads guaranteed to
> > failure.
> > For me it's enough to abort furher review of this code.
> >
> > My advice: really read all of doc/README.developer and take the advice
> > to hart.
> >
> > Thanks,
> > Jaap
> >
> > Brian Oleksa wrote:
> >   
> > > Jaap
> > >
> > > Eventually this might get licensed...but just not sure what direction
> > > we
> > > will be going.
> > >
> > > I have tracked down many many problems before when my code crashed 
> > > within the GUI...because I would get some what of
> > > a decent error. But I am having a hard time tracking down this bug as
> > > it
> > > runs fine in the GUI but not in tshark.
> > >
> > > Doesn't tshark run off the same base code as the GUI does..?? If 
> > > so...then you think if it would crash in one that it would crash in
the 
> > > other....wouldn't you think..??
> > >
> > > Attached is my code. Any help is greatly appreciated.
> > >
> > > Thank you
> > > Brian
> > >
> > >
> > >
> > >
> > >
> > > Jaap Keuter wrote:
> > >     
> > > > Hi,
> > > >
> > > > Well, your assumption is probably right, that your dissector has 
> > > > something to do with it.
> > > >
> > > > You can post it, but we prefer to spend our time on GPL'ed code. I 
> > > > don't know what you license will be.
> > > > If you prefer not to publish your code you can probably find enough 
> > > > clues in the documentation in the doc directory.
> > > >
> > > > Thanks,
> > > > Jaap
> > > >
> > > > Brian Oleksa wrote:
> > > >  
> > > >       
> > > > > Chris and Jaap
> > > > >
> > > > > Well.... I guess I can point out the obvious here:
> > > > >
> > > > > I wrote a dissector that works fine with the GUI with no 
> > > > > problem...but it crashes when I use tshark.
> > > > >
> > > > > HOWEVER... if I remove my dissector....then my pcap file loads fine 
> > > > > within tshark.
> > > > >
> > > > > So the problem has to be with my dissector....correct..??
> > > > >
> > > > > Is there anyway I can post my code so you can take a look..??
> > > > >
> > > > > This is hard to track down as again everything works fine in the GUI

> > > > > and I get NO real error message within tshark.
> > > > >
> > > > > What do you think..?
> > > > >
> > > > > Thanks,
> > > > > Brian
> > > > >
> > > > >
> > > > >
> > > > > Maynard, Chris wrote:
> > > > >    
> > > > >         
> > > > > > The file may not be corrupt but might contain packet(s) which are
> > > > > > exposing a tshark bug.  If you can post the capture file, that
would
> > > > > > probably help.  If you don't wish to post it on the mailing list,
you
> > > > > > can open a bug report and post it there instead, marking the file
as
> > > > > > private if you so desire so only the core developers have access to
> > > > > > it.
> > > > > >
> > > > > > - Chris
> > > > > >
> > > > > > -----Original Message-----
> > > > > > From: wireshark-dev-bounces () wireshark org
> > > > > > [mailto:wireshark-dev-bounces () wireshark org] On Behalf Of Brian
> > > > > > Oleksa
> > > > > > Sent: Monday, November 23, 2009 12:59 PM
> > > > > > To: Developer support list for Wireshark
> > > > > > Subject: Re: [Wireshark-dev] wireshark GUI vs tshark
> > > > > >
> > > > > > Jaap and Chris
> > > > > >
> > > > > > I am running this on Win XP service pack 2.
> > > > > > I am using wireshark Version 1.2.4 (SVN Rev 30978).
> > > > > >
> > > > > > The test.pcap file has been around for a while...so chances are it 
> > > > > > is not corrupt. It never crashes using the GUI...it just crashes
and 
> > > > > > gives me that pop up when I run it with that tshark command.
> > > > > >
> > > > > > This is about all the information that I can provide....unless you 
> > > > > > can think of something else that you need..??
> > > > > >
> > > > > > Thanks,
> > > > > > Brian
> > > > > >
> > > > > >
> > > > > > Jaap Keuter wrote:
> > > > > >        
> > > > > >           
> > > > > > > Hi Brian,
> > > > > > >
> > > > > > > Thanks for including the error report. It in itself doesn't tell
> > > > > > >             
> > > > > > >             
> > > > > > anything,
> > > > > >        
> > > > > >           
> > > > > > > other than that a problem was detected. That's why Chris asked you
> > > > > > >             
> > > > > > >             
> > > > > > some
> > > > > >        
> > > > > >           
> > > > > > > more questions on the whole situation. Maybe we can help you
further
> > > > > > >             
> > > > > > >             
> > > > > > when
> > > > > >        
> > > > > >           
> > > > > > > you look into them.
> > > > > > >
> > > > > > > Thanks,
> > > > > > > Jaap
> > > > > > >
> > > > > > > On Mon, 23 Nov 2009 12:02:17 -0500, Brian Oleksa
> > > > > > > <oleksab () darkcornersoftware com> wrote:
> > > > > > >              
> > > > > > >             
> > > > > > > > Chris
> > > > > > > >
> > > > > > > > I have attached the error this time....sorry about that. :-)
> > > > > > > >
> > > > > > > > I get this error when I run with tshark using the following
> > > > > > > > command:
> > > > > > > >
> > > > > > > > tshark -nr test.pcap ip.dst==x.x.x.x
> > > > > > > > But when I filter in the GUI ... I have no problems.
> > > > > > > >
> > > > > > > > Thanks,
> > > > > > > > Brian
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > Maynard, Chris wrote:
> > > > > > > >                    
> > > > > > > >               
> > > > > > > > > > Any thoughts..??
> > > > > > > > > >                                     
> > > > > > > > > >                   
> > > > > > > > > My first thought was, "I guess you forgot to include the error."
> > > > > > > > > :)
> > > > > > > > >
> > > > > > > > > In addition to the error, you might want to include some
Wireshark
> > > > > > > > > version information, what OS you're running on and any other
> > > > > > > > >                           
> > > > > > > > >                 
> > > > > > > information
> > > > > > >              
> > > > > > >             
> > > > > > > > > that you think might be relevant.
> > > > > > > > >
> > > > > > > > > By the way, I tried a similar tshark command using Wireshark
1.2.4
> > > > > > > > >                     
> > > > > > > > >                 
> > > > > > on
> > > > > >        
> > > > > >           
> > > > > > > > > Windows XP SP3 with no problems.  Maybe you are running an older
> > > > > > > > >                           
> > > > > > > > >                 
> > > > > > > version
> > > > > > >              
> > > > > > >             
> > > > > > > > > of Wireshark with a known bug that has been fixed, or maybe your
> > > > > > > > > test.pcap file is corrupt or exposes a Wireshark bug, in which
> > > > > > > > > case
> > > > > > > > >                     
> > > > > > > > >                 
> > > > > > a
> > > > > >        
> > > > > >           
> > > > > > > > > bug report might be in order with the attached test.pcap file
> > > > > > > > >                     
> > > > > > > > >                 
> > > > > > included
> > > > > >        
> > > > > >           
> > > > > > > > > so the core developers can analyze the error and find & fix the
> > > > > > > > > bug.
> > > > > > > > >
> > > > > > > > > - Chris
> > > > > > > > >
> > > > > > > > > -----Original Message-----
> > > > > > > > > From: wireshark-dev-bounces () wireshark org
> > > > > > > > > [mailto:wireshark-dev-bounces () wireshark org] On Behalf Of Brian
> > > > > > > > >                     
> > > > > > > > >                 
> > > > > > Oleksa
> > > > > >        
> > > > > >           
> > > > > > > > > Sent: Sunday, November 22, 2009 10:49 PM
> > > > > > > > > To: Developer support list for Wireshark
> > > > > > > > > Subject: [Wireshark-dev] wireshark GUI vs tshark
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > Wiresharkers
> > > > > > > > >
> > > > > > > > > When I use my dissector with the GUI... everything works fine.
The
> > > > > > > > >                     
> > > > > > > > >                 
> > > > > > pcap
> > > > > >        
> > > > > >           
> > > > > > > > >                           
> > > > > > > > >                 
> > > > > > >              
> > > > > > >             
> > > > > > > > > file that I load comes right up with NO problems. I can filter 
> > > > > > > > > (ip.dst==x.x.x.x) with no problems.
> > > > > > > > >
> > > > > > > > > But if I try to open that same pcap file with tshark using the
> > > > > > > > >                           
> > > > > > > > >                 
> > > > > > > following
> > > > > > >              
> > > > > > >             
> > > > > > > > > command:
> > > > > > > > >
> > > > > > > > > tshark -nr test.pcap ip.dst==x.x.x.x    
> > > > > > > > > The files appears to start loading.. then I get the following
> > > > > > > > > error.
> > > > > > > > >
> > > > > > > > > Any thoughts..??
> > > > > > > > >
> > > > > > > > > Thanks,
> > > > > > > > > Brian
> > > > > > > > >             

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