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From Greg Ames <ames.g...@gmail.com>
Subject Re: Mitigation Range header
Date Wed, 24 Aug 2011 16:19:59 GMT
On Wed, Aug 24, 2011 at 10:33 AM, "Plüm, Rüdiger, VF-Group" <
ruediger.pluem@vodafone.com> wrote:

> **
>
>
> I think mod_deflate is just the tool to convert an O(N^2) data size problem
> into an O(N^2) CPU usage problem, where N is some function of
> LimitRequestLine.  If the file size is smaller than the largest range end
> used in the attack, it may reduce the amount of data actually going down the
> filter chain.
>
> Greg
>
>
>
> I don't think so. The compression happens before the byterange filter and
> the byterange filter just hacks the already compressed brigade into more
> buckets and rearranges them.
> mod_deflate does not do more work if it is a range request. It does the
> same amount of work as for the non range request.
>
> OK, thanks for the clarification, Rüdiger.  Then I don't understand why
mod_deflate seems to be an important factor in killing the server.

If the DEFLATE filter runs first, can you do anything useful with a subrange
of its output?  i.e., could a client decompress a subrange that starts in
the middle of the compressed version and get a subrange of the original
uncompressed data?

Greg

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