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Date:	Mon, 06 Aug 2001 13:09:34 +0100
From:	Bill Petheram <bilpet AT hplb DOT hpl DOT hp DOT com>
Organization:	TESL, HP Labs Bristol
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To:	Corinna Vinschen <cygwin AT cygwin DOT com>, Lapo Luchini <lapo AT lapo DOT it>
Subject:	Re: Rsync: found the problem
References:	<610A1F4808E9D411888F0001023F6361A2EC AT MUCX> <3B46E116 DOT 20508 DOT C8E5ACB AT localhost> <20010707095422 DOT C7298 AT redhat DOT com> <3B499BF7 DOT 6D8FCABC AT hplb DOT hpl DOT hp DOT com> <20010709222226 DOT A16128 AT cygbert DOT vinschen DOT de> <3B6960FA DOT 8099DD72 AT hplb DOT hpl DOT hp DOT com> <3B6A943A DOT 10E925C8 AT hplb DOT hpl DOT hp DOT com> <20010803190741 DOT Z23782 AT cygbert DOT vinschen DOT de>

Is it a bug or a feature?

Internally cygwin uses a flag OLD_O_NDELAY with the value 0x0004. This
is used for backward compatibility (according to the comment). There is
code to check that if either the OLD_O_NDELAY flag is set or if O_NDELAY
(0x4000) is set they both get set.

So when rsync does a GETFL it does the 'normal':- val &= ~NONBLOCK_FLAG
to set to blocking. Unfortunately the OLD_O_NDELAY bit is still set so
the when the SETFL is called is sets the O_FNDELAY bit as well.
Obviously this means that once a socket is set to non-blocking mode it
cannot be reset using this method. Note that the OLD_O_NDELAY is not
defined in the installed header files, only internally to cygwin.

I think that it is not possible to run old executables with newer DLLs,
so may be the OLD_O_NDELAY flag can be removed.

I added this patch to rsync.h

470a471,474
> #ifdef __CYGWIN32__
> #define OLD_O_NDELAY 0x0004
> #define NONBLOCK_FLAG (O_NONBLOCK | OLD_O_NDELAY)
> #else
476a481
> #endif

This fixes the problem for rsync.

bill

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