FWaaS Insertion Model on Routers


The blueprint proposes a change to the FWaaS insertion model to associate a Firewall with a specified set of Routers (can be a single Router) as opposed to the current model of association with all Routers in the tenant.

Problem Description

The FWaaS model defines 3 resources: Firewall rules, Firewall policies and Firewalls. The Firewall rules has attributes to specify a filter rule. The Firewall policy is a container for a collection of rules. The Firewall itself is associated with a Firewall policy and thereby indirectly to a set of rules. Currently no insertion point can be defined for a Firewall, and there is no intent to abstract the insertion from the service itself to allow for various types of insertion points(L3, Bump in the wire etc).

The FWaaS reference implementation inserts the Firewall on all ‘qr-’ interfaces on all routers in the tenant. The plan was to allow the insertion point to be driven by the Service Insertion proposals[1][2]. Given that the Service Insertion proposals have not yet been adopted for various reasons, the objective of this effort is to restrict the scope to FWaaS and insertion on a specified set of Routers.

In the current model and implementation we can only support a single Firewall on a tenant as the Firewall is present on all Routers. This does not provide the ability to selectively firewall traffic for a subnet or a set of subnets in the tenant topology. This requires all Rules for a tenant topology to be collected together in the policy associated with the Firewall. This is both inefficient and prone to errors.

Routers are not tracked on the Firewall DB so it is not always straightforward to reflect the Firewall state based on the state transtions on one of potentially many Routers associated with the Firewall. We can handle the case when a new Router is added but it is more involved to handle Router deletions.

Proposed Change

It is being proposed to associate a Firewall with a set of Routers which is specified in the API. Resource validation can be performed and appropriate action can be taken by the Plugin. The insertion point as the Router(s) will be tracked in the Firewall DB.

With some trepidation the additional attribute can be proposed as an extension or this can be added as an attribute to the Firewall extension. With the rework happening in this area, this effort will align with the community direction here.

A minor variation with this same fundamental intent of the Firewall being associated with a set of Routers is more favored based on discussions with members of the FWaaS subteam and associated individuals with interactions with Customers and Deployers. Rather than just associating a set of Routers and implicitly on all their interfaces, an option to selectively apply to a specified set of the Router interfaces across the Routers is also proposed as a phase 2 of the implementation. This can support backends that might need the Firewall association with a list of ports. The default behavior is to apply on all interfaces of the Router(s).

With this variation on the theme, the list of interfaces in addition to the Router will be accomodated as an attribute to the Firewall extension or proposed as an extension.

With this change we can support multiple Firewalls within a tenant with better discrimination based on the Router insertion point rather than have all rules for the entire topology applied every where. The constraint of a port being a member of a single Firewall will be enforced for consistent behavior. So with the default of applying on all interfaces of a Router - the constraint will imply that a Router can only accomodate a single Firewall. With the port list, to apply on a subset of Router interfaces, we can support multiple Firewalls on a Router as well.

Data Model Impact

The proposal is to associate the Firewall with the list of Routers provided in the Create or Update workflows. Appropriate Foreign Key constraints will be applied.

Attribute name









Firewall id





Associated Routers

The port-id list attribute will be added to the above model as Phase 2 of the implementation.

Database Migration: The current implementation installs the Firewall on all Routers in the tenant. The Routers are not tracked in the Firewall Database. On upgrade, as part of the migration it is proposed that each Router in the tenant will be added as a Router associated with the Firewall as in the new Data Model. Downgrade will not be supported.


This would be the addition to the Firewall resource. As mentioned earlier, an approach consistent with the extensions rework will be adopted. Support for Routers is added in Phase 1.

  'firewalls': {
      'router_ids': {'allow_post': True, 'allow_put': True,
                    'validate': {'type:uuid_list': None},
                    'is_visible': True},

And the list of ports as targeted for Phase 2.

  'firewalls': {
      'router_ports': {'allow_post': True, 'allow_put': True,
                         'validate': {'type:uuid_list': None},
                         'convert_to': attr.convert_none_to_empty_list,
                         'default': None, 'is_visible': True},

Security Impact


Notifications Impact

The FWaaS Agent will not need to consume all router_add events as in the current model. No changes to any messaging is planned.

Other End User Impact

In the current model, FWaaS does not specify any insertion point. The API in the proposed model will accomodate a set of Routers as an additional attribute . As in the current model, the Firewall state will start in PENDING_CREATE (or CREATED in DVR mode) and will go to ACTIVE with successful completion of messaging with the FWaaS Agent and the iptables backend. The CLI representations below are some possible suggestions.

neutron firewall-create FW-POLICY –router <r1> –router <r2>

neutron firewall-create FW-POLICY –routers “<r1> <r2> … <rm>”

And this implicitly installs the Firewall on all internal interfaces of each router specified.

If this new attribute is not specified on firewall-create, the firewall logical resource will be created and be in PENDING_CREATE (or CREATED in DVR mode) state. This enables decoupling the Firewall Resource creation from Router creation. This can support a scenario where Firewalls can be pre-provisioned and can later be bound to specific Routers which can get created at a later point on a tenant network.

This is similar to the current model when there are no routers present in the tenant. With this proposal, the Firewall state will change to ACTIVE on a firewall-update with the insertion point details. The CLI representation below is one possible suggestion.

neutron firewall-update FIREWALL –router <r1> –router <r2>

In Phase 2, with the additional attribute of port list, the Create would be something of the form:

neutron firewall-create

FW-POLICY –router <r1> –router <r2> –port-id <p1> –port-id <p2> …

neutron firewall-create

FW-POLICY –routers “<r1> <r2> … <rm>” –port-ids “<p1> <p2> … <pn>”

The port list is again optional in the update workflow. If it is not provided, the Firewall is applied to all the internal interfaces of the Routers. And when the list of ports is provided, it is applied on those internal interfaces mapped to the corresponding Routers. This is identical to the create workflow.

The update workflow will also support updating the routers and/or the list of ports on a ACTIVE Firewall. All updates are effected with proper validation of ports, routers and port ownership with the Routers. This can be represented as below.

neutron firewall-update FIREWALL

–router <r1> –router <r2> –port-id <p1> –port-id <p2> …

Performance Impact


IPv6 Impact

No impacts.

Other Deployer Impact

With support for migration, upgrades will be handled with a move to the new Data model.

Developer Impact

Any Plugins that rely on the Firewall being installed on all Routers in the tenant and are based directly off the reference implementation will need to be changed. This model has been brought up in the FWaaS IRC and by reaching out to the FWaaS developers. No significant impact has been noted. This spec also serves to address any concerns.

Community Impact

This change has been discussed in the past and attempts were made to address this through the Service Insertion blueprints. The need to address this issue has been discussed within the FWaaS subteam. And this has been brought up at the recent summit by Mark and discussed with other cores. Some of the details on the approach has been discussed amongst the FWaaS subteam at the summit and continued over at the FWaaS IRC.


  • Look again at one of the earlier Service Insertion proposals.[1][2]


The first phase will target applying on the specified routers. The addition of the option to specify a list of ports will be phased after this.



Work Items

Phase 1 * Refactor Plugin for new routers attribute. * DB changes to associate the routers for the firewall. * Migration changes on upgrade. * Agent interaction changes to the messaging dict to include the routers. * Refactor FW Agent, to deal with specified routers and remove handling for new routers.

Phase 2 (Low Priority) * Refactoring for additional port list attribute as above. * Validation logic on ports on Routers and multiple Firewalls on Router. * Agent changes to messaging for interface attributes. * Refactor iptables driver to support specific interface in filter rules.


No direct dependency but with the services spinout, L3 Agent refactor this can cause some pain. But it is seen that some of this can be complementary.


Tempest Tests

Existing tempest test will be modified to add additional attributes.

Functional Tests

Basic functionality is not being changed so the changes to functional tests will just involve the addition of specifying new insertion point attributes.

API Tests

Changes to add the new attributes.

Documentation Impact

User Documentation

User Documentation will be updated to include the new attributes and minor change to the workflow wherein now the insertion points will need to be specified.

Developer Documentation

API changes will be documented.


[1]https://blueprints.launchpad.net/neutron/+spec/neutron-services-insertion-chaining-steering [2]https://blueprints.launchpad.net/neutron/+spec/service-base-class-and-insertion