Deep Dive into Neutron
Neutron ML2
The Modular Layer2 (ml2) plugin is a framework allowing OpenStack Networking to simultaneusly utilze the variety of layer2 networking technology found in complex real-world data centres.
It currently works with the existing
- openvswitch
- linuxbridge
- hyperv
like:
[ Neutron Server {ML2 Plugin} ]
|_ [ Host A {linuxbridge agent} ]
|_ [ Host B{hyperv agent} ]
|_ [ Host C{openvswitch agent} ]
|_ [ Host D{openvswitch agent} ]
* Exsiting ML2 Plugin works with existing agents
* Separate agents for linuxbridge, openvswitch, and hyperv.
L2 agents, and is intended to
- replace
- deprecate
like:
[ Neutron Server {ML2 Plugin} ]
|_ [ Host A {modular agent} ]
|_ [ Host B {modular agent} ]
|_ [ Host C {modular agent} ]
|_ [ Host D {modular agent} ]
* Combine open source agents
* Have a single agent which can support linuxbridge and openvswitch
* Pluggable drivers for additional vswitches, infiniband, sr-iov, etc
The monolithic plugins associated with those L2 agents. The ml2 framework is also intended to greatly simplify adding support for new L2 networking technologies, requiring much less intial and ongoing effort than would be required to add a new monolithic core plugin. A modular agent may be developed as a follow-on effort.
Architecture
ML2 Plugin {
TypeDriver {
},
MechanismDriver {
OpenvSwitch, Hyper-V, OpenDaylight, Arista, Cisco Nexus
}
ExtensionDriver
}
TypeDriver
Each available network type is managed by an ml2 TypeDriver. TypeDrivers maintain any needed type-specific network state, and perform provider network validation and tenant network allocation.
The ml2 plugin currently includes drivers for:
// ./neutron/plugins/ml2/driver_api.py
38 class TypeDriver(object):
....
56 def get_type(self):
Get driver's network type.
....
64 def initialize(self):
Perform driver initialization
....
74 def is_partial_segment(self, segment):
Return true if segment is a patially specified segment
....
82 def validate_provider_segment(self, segment):
Validate attributes of a provider network segment
....
102 def reserve_provider_segment(self, session, segment):
Reeserve resource associated with a provider network segment
....
117 def allocate_tenant_segment(self, session):
Allocate resource for a new tenant network segment
....
133 def release_segment(self, session, segment):
Release network segment
....
147 def get_mtu(self, physical):
Get driver's network MTU
Mechanism Drivers
Each networking mechanism is managed by an mll2 MechanismDrivers. The MechanismDriver is responsible for taking the information established by the TypeDriver and ensuring that it is properly applied given the specific networking mechanisms that have been enabled.
The MechanismDriver interface currently supports the:
- creatin
- update
- deletion
of network and port resources. For every action that can be taken on a resource, the mechanism driver exposes two methods:
- ACTION_RESOURCE_percommit
- ACTION_RESOURCE_postcommit
The precommit method:
Used by mechanism drivers to validate the action being taken and make any required changes to the mechanism driver's private database.
Should not block, and therefore cannot communicate with anything outside of Neutron.
The postcommit method:
Is responsible for appropriately pushing the change to the resource to the entity responsible for applying that change.
// ./neutron/plugins/ml2/driver_api.py
548 class MechanismDriver(object):
....
570 def initialize(self):
Perform driver initialization
....
579 def create_network_precommit(self, context):
Allocate resources for a new network
....
592 def create_network_postcommit(self, context):
Create a network
....
605 def update_network_precommit(self, context):
Update resources of a network
....
623 def update_network_postcommit(self, context):
Update a network
....
641 def delete_network_precommit(self, context):
Delete resources for a network
....
655 def delete_network_postcommit(self, context):
Delete a network
....
669 def create_subnet_precommit(self, context):
Allocate resources for a new subnet
....
682 def create_subnet_postcommit(self, context):
Create a subnet
....
695 def update_subnet_precommit(self, context):
Update resources of a subnet
....
713 def update_subnet_postcommit(self, context):
Update a subnet
....
731 def delete_subnet_precommit(self, context):
Delete resources for a subnet
....
745 def delete_subnet_postcommit(self, context):
Delete a subnet
....
759 def create_port_precommit(self, context):
Allocate resources for a new port
....
771 def create_port_postcommit(self, context):
Create a port
....
783 def update_port_precommit(self, context):
Update resources of a port
....
800 def update_port_postcommit(self, context):
Update a port
....
818 def delete_port_precommit(self, context):
Delete resources of a port
....
830 def delete_port_postcommit(self, context):
Delete a port
....
844 def bind_port(self, context):
Attempt to bind a port
....
882 def check_vlan_transparency(self, context):
Check if the network supports vlan transparency
ExtensionDriver
An extension driver extends the core resources implemented by the ML2 plugin with additional atributes.
// ./neutron/plugins/ml2/driver_api.py
893 class ExtensionDriver(object):
....
905 def initialize(self):
Perform driver initialization
....
915 def extension_alias(self):
Supported extension alias
....
923 def process_create_network(self, plugin_context, data, result):
Process extended attributes for create network
....
937 def process_create_subnet(self, plugin_context, data, result):
Process extended attributes for create subnet
....
951 def process_create_port(self, plugin_context, data, result):
Process extended attributes for create port
....
965 def process_update_network(self, plugin_context, data, result):
Process extended attributes for update network
....
979 def process_update_subnet(self, plugin_context, data, result):
Process extended attributes for update subnet
....
993 def process_update_port(self, plugin_context, data, result):
Process extended attributes for update port
....
1007 def extend_network_dict(self, session, base_model, result):
Add extended attributes to network dictionary
....
1021 def extend_subnet_dict(self, session, base_model, result):
Add extened attributes to subnet dictionary
....
1035 def extend_port_dict(self, session, base_model, result):
Add extended attributes to subnet dictionary
How Plugin Loaded?
// ./neutron/plugins/ml2/managers.py
In TypeManager class, each function in driver_api.py is called:
39 class TypeManager(stevedore.named.NamedExtensionManager):
53 self._check_tenant_network_types(cfg.CONF.ml2.tenant_network_types)
54 self._check_external_network_type(cfg.CONF.ml2.external_network_type)
58 network_type = ext.obj.get_type()
170 driver.obj.initialize()
204 return driver.obj.is_partial_segment(segment)
213 driver.obj.validate_provider_segment(segment)
221 return driver.obj.reserve_provider_segment(session, segment)
225 return driver.obj.allocate_tenant_segment(session)
249 driver.obj.release_segment(session, segment)
In MechanismManager class, each function in driver_api.py is called:
284 class MechanismManager(stevedore.named.NamedExtensionManager):
318 driver.obj.initialize()
364 def create_network_precommit(self, context):
378 def create_network_postcommit(self, context):
392 def update_network_precommit(self, context):
405 def update_network_postcommit(self, context):
419 def delete_network_precommit(self, context):
490 def update_subnet_postcommit(self, context):
504 def delete_subnet_precommit(self, context):
517 def delete_subnet_postcommit(self, context):
535 def create_port_precommit(self, context):
562 def update_port_precommit(self, context):
589 def delete_port_precommit(self, context):
602 def delete_port_postcommit(self, context):
620 def bind_port(self, context):
Let's focus on TypeManager class.
To be continued...
