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From Dirk-Willem van Gulik <Dirk-Willem.van.Gu...@bbc.co.uk>
Subject Re: Fixing Ranges
Date Thu, 25 Aug 2011 11:47:32 GMT

On 25 Aug 2011, at 12:40, Jim Jagielski wrote:

> Tested and this does appear to both address the DoS as well as
> reduce memory usage for "excessive" range requests…
> 
> +1 for adding this no matter what.

Yup - same here. Makes PDF serving a heck of a lot better too.

Dw.

> 
> On Aug 24, 2011, at 7:38 PM, Stefan Fritsch wrote:
> 
> > On Thursday 25 August 2011, Greg Ames wrote:
> >> On Wed, Aug 24, 2011 at 5:16 PM, Stefan Fritsch <sf@sfritsch.de>
> > wrote:
> >>> I have another idea: Instead of using apr_brigade_partition write
> >>> a new function ap_brigade_copy_part that leaves the original
> >>> brigade untouched. It would copy the necessary buckets to a new
> >>> brigade and then split the first and last of those copied
> >>> buckets as necessary and destroy the excess buckets. AFAICS,
> >>> this would reduce the quadratic growth into linear. Do you think
> >>> that would solve our problems?
> >>
> >> How does apr_brigade_partition contribute to quadratic growth?
> >> Does the original brigade end up with a lot of one byte buckets?
> >
> > Yes, it splits the buckets in the original brigade, creating up to two
> > new buckets for every range. These split one-byte buckets are then
> > copied again for each of the subsequent ranges.
> >
> > The attached PoC patch does not change the original brigade and seems
> > to fix the DoS for me. It needs some more work and some review for
> > integer overflows, though. (apr_brigade_partition does some
> > interesting things there).
> > <range-linear.diff>
> 
> 


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