Bug 1912431

Summary: [OVS] multicast between VM instances on different compute nodes is broken with IGMP snooping enabled
Product: Red Hat OpenStack Reporter: Roman Safronov <rsafrono>
Component: openstack-neutronAssignee: Slawek Kaplonski <skaplons>
Status: CLOSED ERRATA QA Contact: Roman Safronov <rsafrono>
Severity: high Docs Contact:
Priority: high    
Version: 16.1 (Train)CC: bcafarel, chrisw, scohen, shtiwari, skaplons
Target Milestone: z7Keywords: Triaged
Target Release: 16.1 (Train on RHEL 8.2)   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: openstack-neutron-15.2.1-1.20210629093310.el8ost Doc Type: No Doc Update
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2021-12-09 20:17:29 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description Roman Safronov 2021-01-04 13:13:30 UTC 
Description of problem:
When igmp snooping is enabled and VMs are running on 2 different compute nodes multicast traffic sent by one VM is not reaching second VM (subscribed to the relevant multicast group).     

Version-Release number of selected component (if applicable):
RHOS-16.1-RHEL-8-20201214.n.3

How reproducible:
100%

Steps to Reproduce:
Note, use environment with ML2/OVS mechanism driver.
1. Make sure igmp snooping is enabled in neutron and br-int on compute nodes.
In order to check you can run "sudo podman exec -it neutron_api crudini --get /etc/neutron/neutron.conf   ovs igmp_snooping_enable" on controller nodes. It should return True. And also "sudo ovs-vsctl get  Bridge br-int mcast_snooping_enable" and "sudo ovs-vsctl get  Bridge br-int other_config:mcast-snooping-disable-flood-unregistered" return 'true'

2. Create router, tenant network/subnet, security group allowing icmp, ssh, igmp and udp port 5001 (we will use it). Launch 2 VMs on the network. Make sure both VMs are running on different compute nodes. 
3. Subscribe one VM (receiver) to a multicast group (note: the group should not be from range 224.0.0.X, e.g. 225.0.0.100 is OK)
4. From the second VM (sender) send udp packets to the multicast group (use same port as security group allows, e.g. 5001).

Actual results:
Packets do not reach the receiver VM.

Expected results:
Packets reach the receiver VM

Additional info:
Note, in case both VMs are running on the same compute node multicast traffic from the sender reaches the receiver VM successfully.
Comment 10 Roman Safronov 2021-07-29 15:34:25 UTC 
Verified on RHOS-16.1-RHEL-8-20210727.n.1 with neutron python3-neutron-15.2.1-1.20210712133305.40d217c.el8ost.noarch
Verified that when igmp snooping is enabled multicast is working between VM instances on different compute nodes.
Comment 26 errata-xmlrpc 2021-12-09 20:17:29 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (Red Hat OpenStack Platform 16.1.7 (Train) bug fix and enhancement advisory), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2021:3762