Ethereal-dev: Re: [Ethereal-dev] Found a defragmentation "bug" in the DCE RPC dissector

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From: Ulf Lamping <ulf.lamping@xxxxxx>
Date: Thu, 20 Jan 2005 20:17:29 +0100
Todd Sabin wrote:


Ulf Lamping <ulf.lamping@xxxxxx> writes:
You shouldn't rely on the alloc hint, at all.
I've never relied on that, only the implementation did ;-) I don't know the one who's implemented that. 


Not only can it be
zero, it can be a completely bogus value, as well.  It is, as the name
says, just a hint.  Hints can be wrong, and ethereal shouldn't fail if
they are.

Yes, the spec states exactly that.


I'm not that familiar with the defragmentation stuff in ethereal, but
the 'simple' approach you describe sounds right to me.  I don't think
the DCE/RPC layer is the place to worry about packets being out of
order or retransmitted.  If you want to work correctly in those cases,
the TCP dissector should handle them, no?
The implementation I've checked in yesterday will use the alloc_hint field if it unequals zero (like before) and the way I described it, if it's zero.
We might want to remove the alloc_hint "unequal zero path" completely then. However, as I know some things of DCE/RPC, I won't call me an expert on this. 

Any reasons aginst removing it?

Regards, ULFL