Ethereal-dev: Re: [Ethereal-dev] v0.9.5 hangs on bad IP protocol field.

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From: Guy Harris <gharris@xxxxxxxxx>
Date: Wed, 31 Jul 2002 03:08:39 -0700
On Tue, Jul 30, 2002 at 05:20:37PM +1000, ALEX LAM wrote:
> Hmmm... yes, that make sense... perhaps ethereal should have the option 
> for allowing
> the user to decide whether parsing should or should not stop once error 
> is encountered...

In this particular case:

	1) the IP dissector has no reason to think that 0x2e is
	   "erroneous" - RSVP is a perfectly good protocol to run atop
	   IP;

	2) the bug is in the *RSVP* dissector, and could happen with a
	   *completely valid* IP header and a bad RSVP packet, and the
	   problem is that it *wasn't even checking* whether the length
	   of an object was 0, not that it *wasn't stopping the parsing
	   of the packet* if the length of the object was 0.

(I've checked in a fix for that bug.)

What reason is there to add the option you describe?  The only reason to
stop parsing is if you can't continue parsing, in which you have to stop.