invoking qemu-bridge-helper manually

[daggs]

Greetings,

I have two vms, one is a router and another is a utility vm running using 
libvirt+qemu.
they are connected via a virtual switch which works great e.g. the util vm asks 
for an ip, gets one and interacts with the vm and the outside world.
now I want to connect the host to that virt switch, I'm able to create a tap 
and assign it to the virt switch, but the tap remains in no carrier state as 
there is no userspace program to manage the data transfer.
the virt switch has two tap devices (for each vm connected to the virt switch) 
which I assume are created using the util stated above.
so I was wondering if there is a way to invoke this util manually so qemu will 
handle the data transfer as it does so already and save me the need to reinvent 
the wheel.
from what I can see, the only issue is the unixfd value passed from the invoker.

Thanks,

Dagg