[vbox-dev] Control IP multicast reception via API?

Klaus Espenlaub klaus.espenlaub at oracle.com
Thu Jul 10 11:34:39 GMT 2014


On 10.07.2014 07:49, Karoline Haus wrote:
> Do the host-only network interfaces in any way behave differently to the
> typical tun/tap Ethernet devices Linux offers? I mean in terms of
> multicast reception. So if I bridge from the physical device to the
> host-only interface then it should be able to process multicast pakets
> as well right?

It should - but why would one want to touch the linux bridging support? 
The reason why we dumped it years ago was that it was extremely 
unreliable. Caused random connectivity problems, and there were setups 
where for unexplainable reasons no data would ever pass through br0 to 
the tap device used by VirtualBox. Of course it might be all fixed by 
now, but using linux bridging to connect to a host only network sounds 
like a very complicated way to replace VirtualBox bridging straight to 
the desired interface.

There is no intentional multicast blocking done anywhere in VirtualBox.


> Klaus Espenlaub <klaus.espenlaub at oracle.com> schrieb am 18:20 Dienstag,
> 8.Juli 2014:
> Karoline,
> On 08.07.2014 17:42, Karoline Haus wrote:
>  > Hi there, I was just wondering, if it was possible to control multicast
>  > reception for VMs via host-only interfaces via the VBOX API? I could not
>  > find anything but not sure I searched in the right place. Thanks for any
>  > pointers!
> There's nothing in the API controlling this, and the reason is that the
> emulation itself deals with ethernet frames. It couldn't care less what
> they mean. Of course the actual behavior heavily depends on the
> networking mode (NAT definitely doesn't handle multicast in a sensible
> way), and bridged/host only/internal network should be able to handle
> them. Theoretically. Not aware of this getting tested :)
> Klaus

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