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From Torsten Foertsch <torsten.foert...@gmx.net>
Subject Re: modperl and the TCP_DEFER_ACCEPT-patch for linux
Date Sat, 07 May 2005 17:14:26 GMT
On Saturday 07 May 2005 08:30, Stas Bekman wrote:
> Torsten Foertsch wrote:
> > Hi,
> >
> > yesterday I have patched my apache with this patch and now I have noticed
> > that testing mod_perl hangs in t/protocol/pseudo_http. The reason is
> > simple and to be expected. t/protocol/pseudo_http tests a protocol module
> > that is greeting the client with "HELO" before receiving any data. Since
> > the patch prevents accept(2) from returning before data has been received
> > from the client the connection is not accepted. Hence no piece of code
> > gets chance to send "HELO".
> >
> > Maybe it is worth to change the test so that the client must send
> > someting at first?
> >
> > I could provide a patch.
>
> What's that patch you are talking about, Torsten?

Sorry for not providing a link. Here it is:
http://marc.theaimsgroup.com/?l=apache-httpd-dev&m=111523765005281&w=2

The whole thing came from a discussion about the Timeout configuration 
directive, see
http://marc.theaimsgroup.com/?l=apache-httpd-dev&m=111513459203781&w=2

One proposed solution was to enable BSD accept-filtering. Thus, accept(2) will 
return only if a complete HTTP-request is ready to be read. For Linux a 
similar mechanism exists with the TCP_DEFER_ACCEPT socket option. According 
to the thread Apache 2.1 uses this option. Then a backport was suggested 
resulting in the patch.

> This workaround doesn't sound right. A protocol handler (server) must be
> able to start the conversation first. If not, many protocols relying on
> the server's greeing (e.g. SMTP) won't work. e.g., see:
> http://www.samlogic.net/articles/smtp.htm

I know that it would break some protocols. It can be accepted to httpd-2.0 
only if it is configurable. I was asking whether testing mod_perl should rely 
on the server's ability to send data first.

If not, the attached patch changes slightly the protocol initialization. Now 
the client should send "HELO". The server replies "Nice to meet you".

Torsten

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