Wireshark · Ethereal-dev: Re: [Ethereal-dev] Exception in pdml

[Guy Harris <gharris@xxxxxxxxx>]

Wesley Shields wrote:

> Agreed.  I have a jpeg that when viewed through a browser the resulting 
> capture will throw the exception when outputting to pdml.  I can provide 
> that jpeg, or the capture, if necessary (it's just a generic green ball 
> used as a bullet in webpages).

I'd like to see the capture.

> This idea is much better than my patch of checking for negative values 
> when printing the pdml.  If a dissector is setting a negative value what 
> should be an appropriate fix?

Don't set a negative value. :-)

The reasons why a dissector might be doing that - i.e., the reasons why 
it's incorrectly computing a field length - would differ, so the fixes 
to make it stop would also differ.

> I'd like to know so that the patch I will 
> be writing for this particular dissector will match what you are doing 
> with the rest.  Is there any problem with setting the length to 0?

If the length of the field in the packet isn't 0, yes, there'd be a 
problem with setting the length to 0, as it'd be setting it to an 
incorrect value.  (The fix isn't to just work around a bad length 
calculation by using 0, the fix is to stop calculating the length 
incorrectly.)