Wireshark-dev: Re: [Wireshark-dev] Packet Size limited during capture message
From: Martin Visser <[email protected]>
Date: Wed, 24 Mar 2010 08:21:50 +1100
Any dissector needs to be validate it's input and make sure it doesn't make errant conclusions on what is presented.

For example many protocols have fields that indicate lengths of data within the frame. However any dissector needs to make sure that it doesn't just believe those fields as being correct. A bad [email protected] might change those fields beyond what the protocol intended either to crash the real application or even wireshark. 

Also packets might get unintentionally corrupted or truncated with similar consequences. (Broken links, routers, VPNs can all do this). Wireshark dissectors need to be resilient to this.

Finally Wireshark (and tcpdump) have always had the ability to only capture a truncated packet (mainly to limit resources required during packet capture). A dissector also needs to cope with this. 

Regards, Martin

[email protected]


On Wed, Mar 24, 2010 at 2:42 AM, Brian Oleksa <[email protected]> wrote:
Chris

I will have to look into why my dissector is crashing when I get the Packet Size Limited during capture message.

I am an employee of Dark Corner Software. I am writing the dissector for our clients that use our software.

I have fixed the license issue. Attached is the latest updated file that I am still working on.

We have open source software and closed source software. I am trying to get the open source dissector submitted through wireshark so it can become a part of the wireshark distribution (this is the attached copy).

Our closed source software is for our customers only. I have written a dissector for our closed source software for the client. This is where I am getting the "Packet Size limited during capture " message from.


Thanks,
Brian



Maynard, Chris wrote:
As Jakub pointed out, regardless of the snaplen, if Wireshark is crashing, then the bug is in the dissector, although IMO the biggest bug in the dissector is still the incompatible license.

Brian, please carefully read http://www.gnu.org/licenses/gpl-faq.html#GPLModuleLicense

Gerald et al, consider this e-mail as a report of a violation of the GPL per http://www.gnu.org/licenses/gpl-faq.html#ReportingViolation

So until the dissector is properly licensed, I suggest contacting these folks for support on this dissector: http://www.darkcornersoftware.com/contact.html

- Chris

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Mike Morrin
Sent: Tuesday, March 23, 2010 9:02 AM
To: Developer support list for Wireshark
Subject: Re: [Wireshark-dev] Packet Size limited during capture message


-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Brian Oleksa
Sent: 23 March 2010 12:23
To: Developer support list for Wireshark
Subject: Re: [Wireshark-dev] Packet Size limited during capture message

Chris

I just found out that this was captured using tshark.....but nobody knows what the snaplen was.

So my questions is....   My code is working correctly then....And that this was just a bad judgment of the wrong snaplen......correct..??

Thanks,
Brian

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It is possible for a dissector bug to throw this exception even with a
perfectly captured packet, see Bug 2855 for example.







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