Description of problem: There is currently no support for sniffing the network traffic of a virtual nic, from local or remote. In some cases the debugging or monitoring of a guest is therefore not as easy as it could be. Although it's easy to start a network sniffer on the physical host, it requires direct access to a shell and some knowledge of the current configuration of virtual networks. I think it would be a great benefit for libvirt if network sniffing would be possible out of the box.
One idea would be to start a local tshark sniffing on the card and connect this to a local socket. This could then be forwarded by ssh to a wireshark process running on a desktop.
This sounds like an interesting piece of functionality, and I believe it could be implemented with libvirt's support for data streams. It's unlikely that anyone will take up the task for you, but if you are willing to work on it yourself I'd suggest floating the idea on libvir-list. You'll get a rapid response as to whether others think it would be a useful feature, which I imagine they will, as well as advice on the mechanics of implementing it.
I concur with Dave, it's an interesting idea but this RFE sitting here isn't going to generate any results. It would need someone to send patches or start a mailing list discussion to drum up interest. Closing this as DEFERRED