[libvirt] Dumping network traffic

I'm currently working on a feature that dumps the network traffic of a virtual interface over the streaming api of libvirt. The goal is to offer the possiblity to debug network related problems of guests without the need to have access to a shell on the host. E.g. "virsh iface-dumptraffic virbr0 icmp | tcpdump -n -r -" prints all icmp traffic on virbr0 to stdout. The code below is only a proof of concept, but it should be possible to recognize what I have in mind and how I want to implement it. So I would appreciate any comments on that!