search for: xen_netif_extra_type_mcast_

...imon, I'm afraid the Xen PV drivers (on Linux at least) do not support multicast. There has historically been some support for multicast, IIRC the old Solaris front and backends did support it so there is some support defined but not implemented. e.g. see xen/include/public/io/netif.h and the XEN_NETIF_EXTRA_TYPE_MCAST_{ADD,DEL} message types but these are not implemented in the Linux front/backends. If you want this fixed I think your best bet would be to engage with the upstream project on xen-devel at lists.xen.org (and perhaps netdev at vger.kernel.org too). I'm afraid this is more than likely going to me...