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Date: Mon, 15 Nov 2010 22:22:22 +0100
From: Stefan Weil <weil@mail.berlios.de>
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Subject: Re: [Qemu-devel] [PATCH] add a command line option to specify the
	interface to send multicast packets on
References: <20101111014735.GQ2211@zzz.isi.edu>	<20101115185452.GE26869@zzz.isi.edu>	<4CE18BBC.2050706@codemonkey.ws>	<20101115195212.GG26869@zzz.isi.edu>
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Mike Ryan <mikeryan@isi.edu>, qemu-devel@nongnu.org

Am 15.11.2010 22:07, schrieb Anthony Liguori:
> On 11/15/2010 01:52 PM, Mike Ryan wrote:
>> I'll clarify/elaborate a bit:
>>
>> When using a multicast socket, the OS chooses a default physical
>> interface to send packets. The patch I've supplied allows the user to
>> select the interface.
>>
>> Suppose you have a setup like so:
>>
>> BoxA --- BoxB --- BoxC
>>
>> You wish to run virtual machines on BoxB and BoxC and network them using
>> a multicast UDP socket.
>>
>> BoxB has two network interfaces, and the default multicast interface may
>> be the link between BoxA and BoxB. In this situation, BoxC will not
>> receive any multicast packets from BoxB and networking between the boxes
>> is therefore impossible.
>>
>> The utility of a multicast socket is obviously limited in my simplified
>> example. Generalize BoxC to a LAN of physical machines all running
>> virtual machines you wish to network and the use case should become a
>> bit clearer.
>
> Thanks.  Second question is how portable is SIOCGIFADDR?  I suspect 
> that's very Linux-centric..
>
> Regards,
>
> Anthony Liguori


Yes. It is unavailable for mingw32 (windows).

Regards,

Stefan Weil