RoCEv1 Multicast packets are dropped in the switch

The issue:

I want to run an application that uses Multicast on top of RoCEv1 (version 1) but the packets are dropped in the switch - the cause of the drop is “Multicast egress port list is empty”

I’m using IGMP snooping:

Heron [standalone: master] (config vlan 1) # show ip igmp snooping groups

Vlan ID Group St/Dyn Ports

1 Dyn Eth1/5

Total Num of Dynamic Group Addresses: 1

Total Num of Static Group Addresses : 0

note: multicast is working on RoCEv2 but is not on RoCEv1.

after running show what-just-happened in the switch:

I get that the reason for dropping is: Multicast egress port list is empty

what does this drop reason mean? and what is missing in the switch configuration to make multicast works on top of RoCEv1?

Heron [standalone: master] (config) # show version

Product name: Onyx

Product release: 3.8.2008

Build ID: #1-dev

Build date: 2019-11-19 11:15:58

Target arch: x86_64

Target hw: x86_64

Built by: jenkins@27900d252c67

Version summary: X86_64 3.8.2008 2019-11-19 11:15:58 x86_64

Product model: x86onie

Host ID: 248A07912B0C

System serial num: MT1706X01027

System UUID: fcd6da7c-2e4a-11e7-8000-248a07f36740

Uptime: 11d 19h 23m 50.784s

CPU load averages: 3.02 / 3.05 / 3.04

Number of CPUs: 2

System memory: 2376 MB used / 5413 MB free / 7789 MB total

Swap: 0 MB used / 0 MB free / 0 MB total