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From Nick Kew <>
Subject Re: Timeout for requests
Date Tue, 03 May 2005 22:57:44 GMT
Rasmus Lerdorf wrote:
> Nick Kew wrote:
>>> Turn on accept filtering and this problem goes away.  Or at least it
>>> moves to be a kernel-level issue instead of an Apache one.
>> How does that work with large requests?  Doesn't the whole principle
>> leave you the choice of just moving the DOS attack or breaking
>> pipelining?
> You mean the httpready filter?  The accept will trigger once the buffer
> is full, so yes, large requests will defeat it eventually, but you still
> get the benefit of not tying up an Apache process until the buffer has
> been filled.

OK, that makes sense.  Thanks for clarifying.

> I did fix an issue last year where even with accept filtering enabled
> you could DoS any Apache server by simply opening MaxClients connections
> and trickling a carriage return to each connection very slowly.  So for
> people seeing DoS issues like this, I would suggest upgrading to the
> latest version, turning on accept filtering and turning off keepalive.

I have some recollection of that problem, but not the solution.  It's
actually somewhat topical for my client right now.  You and Paul have
told us about FreeBSD and Linux; is there also a Solaris equivalent?
(probably not required as they're gradually upgrading it to Linux,
but would be good to have).

Nick Kew

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