[Python-Dev] Counting collisions for the win

[David Malcolm]

On Fri, 2012-01-20 at 16:55 +0100, Frank Sievertsen wrote:
> Hello,
> 
> I still see at least two ways to create a DOS attack even with the
> collison-counting-patch.

[snip description of two types of attack on the collision counting
approach]

> What to do now?
> I think it's not smart to reduce the number of allowed collisions 
> dramatically
> AND count all slot-collisions at the same time.

Frank: did you see the new approach I proposed in:
http://bugs.python.org/issue13703#msg151735
http://bugs.python.org/file24289/amortized-probe-counting-dmalcolm-2012-01-21-003.patch

(repurposes the ma_smalltable region of large dictionaries to add
tracking of each such dict's average iterations taken per modification,
and raise an exception when it exceeds a particular ratio)

I'm interested in hearing how it holds up against your various test
cases, or what flaws there are in it.

Thanks!
Dave