Multicast configuration has not changed from ONOS 1.8.
Basically, the multicast routes are maintained in ONOS in the multicast route-table. This table can be programmed using the REST-API or automatically by using an app like the PIM app.
Note that in the former link, the forwarding assumes that ONOS Intent Service is being used. However, in Trellis we do not use ONOS Intents. Instead when changes are made to the Multicast RIB in ONOS, notifications are sent out to all listeners.
The Trellis 'segmentrouting' app which programs the fabric listens to these changes and creates the multicast tree for individual multicast groups.
The segmentrouting app needs to know the vlan-ids to use at ingress (multicast-source) and egress (multicast-sinks). If not configured, both ingressVlan and egressVlan default to None (untagged). We currently do not support ingress/egress vlan configurations for individual multicast groups ie. all trees will be programmed with the same ingress/egress vlans.
line 4: Expected VLAN of the multicast traffic coming from to upstream router or any other multicast source.
line 5: VLAN of the multicast traffic going to downstream multicast sinks.