Sending Multicast Packets from Docker Container (to multicast group)
Docker network drivers have no IGMP/PIM support, so you should really establish a direct Layer 2 connection from the container to the physical switch/router.
As you have found out yourself, docker's default bridge network will not help you here.
I haven't tested it with multicast, but you should be able to achieve that with Pipework.
macvlan driver should help you with your problem, but is currently experimental as of Docker Engine 1.11