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Date:	Thu, 29 Sep 2005 18:50:53 +0200
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: IP_MULTICAST_IF et. all / Winsock[2] value conflict
Message-ID:	<20050929165053.GU12256@calimero.vinschen.de>
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On Sep 29 11:27, Brian Ford wrote:
> I'm having a problem with IP_MULTICAST_IF not working on Cygwin.  While
> investigating, I came across this MS KB article that might describe my
> problem:
> 
> http://support.microsoft.com/default.aspx?scid=kb;en-us;257460
> 
> IP_MULTICAST_IF can have two values (2 or 9) depending on whether you're
> linking to Winsock 1 or 2.  By preprocessing my source and looking in
> /usr/include/cygwin/socket.h, I see we are using the value 2 which means
> it will only work if we link to Winsock 1?
> 
> IIRC, Cygwin dynamically loads which ever library is present or version 2
> if both are available?  I assume we are loading version 2 on my system
> given it is WinXP?
> 
> I don't understand the Cygwin magic to do this well enough to supply a
> patch.  I also don't understand how including Winsock2.h followed by
> Ws2tcpip.h is supposed to allow you to link against either library.
> 
> Here's hoping that Corinna or someone else is less confused and can supply
> a fix to either Cygwin or my limited understanding.  Thanks.

There's no easy fix right now.  We have to drop all traces of Winsock1
in Cygwin and change the headers accordingly.  Since you didn't say
what problem you had, I assume that IP_MULTICAST_IF just didn't do what
you wanted.  Did you try to use just the value 9 instead of IP_MULTICAST_IF?


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat, Inc.

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