[libvirt] Using Libvirt to change the bridge a virtual network card of a running vm is connected to

Hi there, we are using libvirt to manage our VMs. We have several VMs connected to different bridges on the same physical KVM host. We need to change the bridge a virtual machine is connected to once in a while. Currently we are just using brctl to do that. Since this needs to be done over the network we would like to use the Libvirtd. Currently this does not seem possible. We have not found any interface or function within the libvirt library to implement this in a live VM. Only shutdown VMs may be changed via editing the XML representation. Is there any reason for that? Could such a function be easily implemented? Everything but the source bridge would stay the same. It works fine manually via brctl. Any thoughts? Ralf Spenneberg