openstack-helm/doc/source/specs/support-linux-bridge-on-neutron.rst

Support linux bridge on neutron helm chart

Blueprint: support-linux-bridge-on-neutron

Problem Description

This specification will address enablement of LinuxBridge network virtualization for OpenStack Helm (OSH). LinuxBridge is second available networking technology in Neutron's reference architecture. The first one is OVS, that is already implemented in OSH.

The LinuxBridge (LB) is Neutron's L2 agent, using linux kernel bridges as network configuration for VMs. Both OVS and LB are part of Neutron's Modular Layer 2 (ML2) framework, allowing to simultaneously utilize the variety of layer 2 networking technologies.

Other services inside Neutron reference stack (L3/DHCP/metadata agents) are dependent on L2 connectivity agent. Thus, replacing OVS with LB would cause changes in mentioned services configuration.

Proposed Change

LinuxBridge installation with neutron chart takes advantaged of decomposable neutron chart in OSH. LinuxBridge agent will be added as daemonset, similarly how OVS is implemented. New value daemonset_lb_agent should be added in neutron/values.yaml in manifests section:

manifests:
  (...)
  daemonset_dhcp_agent: true
  daemonset_l3_agent: true
  daemonset_lb_agent: false
  daemonset_metadata_agent: true
  daemonset_ovs_agent: true
  daemonset_ovs_db: true
  daemonset_ovs_vswitchd: true
  (...)

By default, daemonset_lb_agent will be set to false to remain default behaviour of installing OVS as networking agent.

Installing OVS requires Kubernetes worker node labeling with tag openvswitch=enabled. To mark nodes where LB should be used, new tag will be introduced: linuxbridge=enabled.

LinuxBridge should support external bridge configuration, as well as auto bridge add mechanism implemented for OVS.

As mentioned before, configuration of L3/DHCP/metadata agent should be adjusted to use LinuxBridge, sample configuration override:

conf:
  neutron:
    default:
      agent:
        interface_driver: linuxbridge
  ml2_conf:
    ml2_type_flat:
      neutron:
        ml2:
          mechanism_drivers: linuxbridge, l2population
  dhcp_agent:
    default:
      neutron:
        base:
          agent:
            interface_driver: linuxbridge
  l3_agent:
    default:
      neutron:
        base:
          agent:
            interface_driver: linuxbridge

Having services configured, also the services pod dependencies should be updated to reflect the new kind on L2 agent:

dependencies:
  dhcp:
    daemonset:
      - lb-agent
  metadata:
    daemonset:
      - lb-agent
  l3:
    daemonset:
      - lb-agent

LinuxBridge should be also enabled in manifests section:

manifests:
  daemonset_lb_agent: true
  daemonset_ovs_agent: false
  daemonset_ovs_db: false
  daemonset_ovs_vswitchd: false

In above example OVS and Neutron OVS agent are disabled.

Another place where Neutron L2 agent should be pointed is dependencies list in other OpenStack projects. Currently, nova-compute has dependency for ovs-agent in nova/values.yaml, it should be changed to:

dependencies:
  compute:
    daemonset:
    - lb-agent

Security Impact

No security impact.

Performance Impact

VM networking performance would be dependent on linux bridge implementation.

Alternatives

OVS is an alternative in Neutron reference architecture. It is already in tree.

Implementation

Assignee(s)

Primary assignees:

• korzen (Artur Korzeniewski)

Work Items

1. Add LinuxBridge daemonset
2. Add gate job testing VM network connectivity
3. Add documentation on how to use LinuxBridge

Testing

Gate job testing VM network connectivity.

Documentation Impact

Documentation on how to use LinuxBridge with Neutron chart.

References