Re: [Qemu-devel] Connecting vde and LAN

[Jim C. Brown]

On Thu, Aug 04, 2005 at 12:14:53PM +0200, Henrik Nordstrom wrote:
> For host->guest packets the RAW sockets demonstrated earlier is fine if 
> you accept that the guest packets is also duplicated on the local lan. I 
> do not know of a method to have host->guest packets sent cleanly without 
> duplication on the Ethernet without setting up a TUN/TAP or PPP interface.
> 
> Regards
> Henrik
> 

I was thinking that perhaps vde_packet could be modified to use a tap device
(for example tap0). Since the guests can't communicate to the address thats on
tap0, it doesn't matter what address it gets - the host address of tap0 and the
ip addresses of the guests don't even have to be on the same subnet.

So, the modified vde_packet would listen on the vde network and set packets
meant for the host (or other workstations on the LAN) to tap0. A route would be
set up so that the packets would be routed from tap0 to eth0, which would allow
the host to see them. On the other side, vde_packet would listen to eth0, and
intercept any packets meant for the guests and inject those into the vde
network.

Of course, I realize that this isn't as good as being able to get vde_pcap to
work right, as it still requires host OS support (for the tap device). However,
it sounds easier than playing with ARP and IP packets and still gives the same
benefit - we get to bridge the vde network with the LAN onto eth0 instead of
br0.

I'm still learning how to create and manipulate tuntap devices so I haven't
been able to code this up yet. Are there any obvious problems that I missed
which would prevent this from working?

-- 
Infinite complexity begets infinite beauty.
Infinite precision begets infinite perfection.