Investigate support for multicast replication + CPU cloning for ARP requests

[ccascone]

To enable host discovery, ONOS apps will install two entries:

1. L2 broadcast table: match on eth dst (FF:FF:FF:FF:FF:FF) and set multicast group ID (to replicate the ARP request to all host-facing ports)
2. ACL table: match on eth type (ARP) and generate packet-in to ONOS (clone to CPU) (for host discovery in ONOS)

The current P4 implementation for FPM maps both tables to the same stage in the BCM pipeline (ACL). Is there a way to support this behavior without modifying the ONOS apps?

Ideas:

• Map L2 broadcast table somewhere else other than the ACL table
• Handle multicast replication + packet-in generation in the switch CPU
• Anything else?

[pudelkoM]

There is another way to get ARP/NDP/DHCP packets to the CPU. With the PORT_PKT_CONTROL table this can be configured for individual ports or VLANs, but only for exactly these protocols.

This option actually is configured at startup by stratum, but not configurable. I'm not sure how to model this in P4.