openstack/kuryr-kubernetes
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Add Network Policy devref Spec

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Adds a Network Policy devref Spec with current implementation
details.

Change-Id: I49ea54d8ccc1035b006a042dcece93ca22de64a2
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Maysa Macedo 2019-05-29 07:17:00 -04:00
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@ -45,6 +45,7 @@ Design documents
high_availability
kuryr_kubernetes_versions
port_crd_usage
network_policy
Indices and tables
------------------

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..
This work is licensed under a Creative Commons Attribution 3.0 Unported
License.
http://creativecommons.org/licenses/by/3.0/legalcode
Convention for heading levels in Neutron devref:
======= Heading 0 (reserved for the title in a document)
------- Heading 1
~~~~~~~ Heading 2
+++++++ Heading 3
''''''' Heading 4
(Avoid deeper levels because they do not render well.)
================================
Network Policy
================================
Purpose
--------
The purpose of this document is to present how Network Policy is supported by
Kuryr-Kubernetes.
Overview
--------
Kubernetes supports a Network Policy object to express ingress and egress rules
for pods. Network Policy reacts on labels to qualify multiple pods, and defines
rules based on differents labeling and/or CIDRs. When combined with a
networking plugin, those policy objetcs are enforced and respected.
Proposed Solution
-----------------
Kuryr-Kubernetes relies on Neutron security groups and security group rules to
enforce a Network Policy object, more specifically one security group per policy
with possibly multiple rules. Each object has a namespace scoped Network Policy
CRD that stores all OpenStack related resources on the Kubernetes side, avoiding
many calls to Neutron and helping to differentiate between the current Kubernetes
status of the Network Policy and the last one Kuryr-Kubernetes enforced.
The network policy CRD has the following format:
.. code-block:: yaml
apiVersion: openstack.org/v1
kind: KuryrNetPolicy
metadata:
...
spec:
egressSgRules:
- security_group_rule:
...
ingressSgRules:
- security_group_rule:
...
networkpolicy_spec:
...
podSelector:
...
securityGroupId: ...
securityGroupName: ...
A new handler has been added to react to Network Policy events, and the existing
ones, for instance service/pod handlers, have been modified to account for the
side effects/actions of when a Network Policy is being enforced.
.. note::
Kuryr supports a network policy that contains:
* Ingress and Egress rules
* namespace selector and pod selector, defined with match labels or match
expressions, mix of namespace and pod selector, ip block
* named port
New handlers and drivers
++++++++++++++++++++++++
The Network Policy handler
~~~~~~~~~~~~~~~~~~~~~~~~~~
This handler is responsible for triggering the Network Policy Spec processing,
and the creation or removal of security group with appropriate security group
rules. It also, applies the security group to the pods and services affected
by the policy.
The Pod Label handler
~~~~~~~~~~~~~~~~~~~~~
This new handler is responsible for triggering the update of a security group
rule upon pod labels changes, and its enforcement on the pod port and service.
The Network Policy driver
~~~~~~~~~~~~~~~~~~~~~~~~~~
Is the main driver. It ensures a Network Policy by processing the Spec
and creating or updating the Security group with appropriate
security group rules.
The Network Policy Security Group driver
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It is responsible for creating, deleting, or updating security group rules
for pods, namespaces or services based on different Network Policies.
Modified handlers and drivers
+++++++++++++++++++++++++++++
The VIF handler
~~~~~~~~~~~~~~~
As network policy rules can be defined based on pod labels, this handler
has been enhanced to trigger a security group rule creation or deletion,
depending on the type of pod event, if the pod is affected by the network
policy and if a new security group rule is needed. Also, it triggers the
translation of the pod rules to the affected service.
The Namespace handler
~~~~~~~~~~~~~~~~~~~~~
Just as the pods labels, namespaces labels can also define a rule in a
Network Policy. To account for this, the namespace handler has been
incremented to trigger the creation, deletion or update of a
security group rule, in case the namespace affects a Network Policy rule,
and the translation of the rule to the affected service.
The Namespace Subnet driver
~~~~~~~~~~~~~~~~~~~~~~~~~~~
In case of a namespace event and a Network Policy enforcement based
on the namespace, this driver creates a subnet to this namespace,
and restrict the number of security group rules for the Network Policy
to just one with the subnet CIDR, instead of one for each pod in the namespace.
The LBaaS driver
~~~~~~~~~~~~~~~~
To restrict the incoming traffic to the backend pods, the LBaaS driver
has been enhanced to translate pods rules to the listener port, and react
to Service ports updates. E.g., when the target port is not allowed by the
policy enforced in the pod, the rule should not be added.
The VIF Pool driver
~~~~~~~~~~~~~~~~~~~
The VIF Pool driver is responsible for updating the Security group applied
to the pods ports. It has been modified to embrace the fact that with Network
Policies pods' ports changes their security group while being used, meaning the
original pool does not fit them anymore, resulting in useless pools and ports
reapplying the original security group. To avoid it, the security group id
is removed from the pool merging all pools with same network, project
and host id. Thus if there is no ports on the pool with the needed
security group id(s), one of the existing ports in the pool is updated
to match the requested sg Id.
Use cases examples
++++++++++++++++++
This section describes some scenarios with a Network Policy being enforced,
what Kuryr componenets gets triggered and what resources are created.
Deny all incoming traffic
~~~~~~~~~~~~~~~~~~~~~~~~~
By default, Kubernetes clusters do not restrict traffic. Only once a network
policy is enforced to a namespace, all traffic not explicitly allowed in the
policy becomes denied. As specified in the following policy:
.. code-block:: yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
name: default-deny
spec:
podSelector: {}
policyTypes:
- Ingress
The following CRD is the translation of policy rules to security group rules.
No ingress rule was created, which means traffic is blocked, and since
there is no restriction for egress traffic, it is allowed to everywhere. Note
that the same happens when no ``policyType`` is defined, since all policies
are assumed to assumed to affect Ingress.
.. code-block:: yaml
apiVersion: openstack.org/v1
kind: KuryrNetPolicy
metadata:
name: np-default-deny
namespace: default
...
spec:
egressSgRules:
- security_group_rule:
description: Kuryr-Kubernetes NetPolicy SG rule
direction: egress
ethertype: IPv4
id: 60a0d59c-2102-43e0-b025-75c98b7d9315
security_group_id: 20d9b623-f1e0-449d-95c1-01624cb3e315
ingressSgRules: []
networkpolicy_spec:
...
podSelector:
...
securityGroupId: 20d9b623-f1e0-449d-95c1-01624cb3e315
securityGroupName: sg-default-deny
Allow traffic from pod
~~~~~~~~~~~~~~~~~~~~~~
The following Network Policy specification has a single rule allowing traffic
on a single port from the group of pods that have the label ``role=monitoring``.
.. code-block:: yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
name: allow-monitoring-via-pod-selector
spec:
podSelector:
matchLabels:
app: server
policyTypes:
- Ingress
ingress:
- from:
- podSelector:
matchLabels:
role: monitoring
ports:
- protocol: TCP
port: 8080
Create the following pod with label ``role=monitoring``::
$ kubectl run monitor --image=busybox --restart=Never --labels=role=monitoring
The generated CRD contains an ingress rule allowing traffic on port 8080 from
the created pod, and an egress rule allowing traffic to everywhere, since no
restriction was enforced.
.. code-block:: yaml
apiVersion: openstack.org/v1
kind: KuryrNetPolicy
metadata:
name: np-allow-monitoring-via-pod-selector
namespace: default
...
spec:
egressSgRules:
- security_group_rule:
description: Kuryr-Kubernetes NetPolicy SG rule
direction: egress
ethertype: IPv4
id: 203a14fe-1059-4eff-93ed-a42bd957145d
security_group_id: 7f0ef8c2-4846-4d8c-952f-94a9098fff17
ingressSgRules:
- namespace: default
security_group_rule:
description: Kuryr-Kubernetes NetPolicy SG rule
direction: ingress
ethertype: IPv4
id: 7987c382-f2a9-47f7-b6e8-1a3a1bcb7d95
port_range_max: 8080
port_range_min: 8080
protocol: tcp
remote_ip_prefix: 10.0.1.143
security_group_id: 7f0ef8c2-4846-4d8c-952f-94a9098fff17
networkpolicy_spec:
...
podSelector:
...
securityGroupId: 7f0ef8c2-4846-4d8c-952f-94a9098fff17
securityGroupName: sg-allow-monitoring-via-pod-selector
Allow traffic from namespace
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The following network policy only allows allowing ingress traffic
from namespace with the label ``purpose=test``:
.. code-block:: yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
name: allow-test-via-ns-selector
spec:
podSelector:
matchLabels:
app: server
policyTypes:
- Ingress
ingress:
- from:
- namespaceSelector:
matchLabels:
purpose: test
ports:
- protocol: TCP
port: 8080
Create a namespace and label it with ``purpose=test``::
$ kubectl create namespace dev
$ kubectl label namespace dev purpose=test
The resulting CRD has an ingress rule allowing traffic
from the namespace CIDR on the specified port, and an
egress rule allowing traffic to everywhere.
.. code-block:: yaml
apiVersion: openstack.org/v1
kind: KuryrNetPolicy
name: np-allow-test-via-ns-selector
namespace: default
...
spec:
egressSgRules:
- security_group_rule:
description: Kuryr-Kubernetes NetPolicy SG rule
direction: egress
ethertype: IPv4
id: 8c21bf42-c8b9-4628-b0a1-bd0dbb192e6b
security_group_id: c480327c-2db4-4eb6-af1e-eeb0ce9b46c9
ingressSgRules:
- namespace: dev
security_group_rule:
description: Kuryr-Kubernetes NetPolicy SG rule
direction: ingress
ethertype: IPv4
id: 2a33b802-56ad-430a-801d-690f653198ef
port_range_max: 8080
port_range_min: 8080
protocol: tcp
remote_ip_prefix: 10.0.1.192/26
security_group_id: c480327c-2db4-4eb6-af1e-eeb0ce9b46c9
networkpolicy_spec:
...
podSelector:
...
securityGroupId: c480327c-2db4-4eb6-af1e-eeb0ce9b46c9
securityGroupName: sg-allow-test-via-ns-selector
.. note::
The Service security groups need to be rechecked when a network policy
that affects ingress traffic is created, and also everytime
a pod or namespace is created.
Create network policy flow
~~~~~~~~~~~~~~~~~~~~~~~~~~
.. image:: ../../images/create_network_policy_flow.svg
:alt: Network Policy creation flow
:align: center
:width: 100%
Create pod flow
~~~~~~~~~~~~~~~
The following diagram only covers the implementation part that affects
network policy.
.. image:: ../../images/update_network_policy_on_pod_creation.svg
:alt: Pod creation flow
:align: center
:width: 100%
Network policy rule definition
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
======================== ======================= ==============================================
NamespaceSelector podSelector Expected result
======================== ======================= ==============================================
namespaceSelector: ns1 podSelector: pod1 Allow traffic from pod1 at ns1
namespaceSelector: ns1 podSelector: {} Allow traffic from all pods at ns1
namespaceSelector: ns1 none Allow traffic from all pods at ns1
namespaceSelector: {} podSelector: pod1 Allow traffic from pod1 from all namespaces
namespaceSelector: {} podSelector: {} Allow traffic from all namespaces
namespaceSelector: {} none Allow traffic from all namespaces
none podSelector: pod1 Allow traffic from pod1 from NP namespace
none podSelector: {} Allow traffic from all pods from NP namespace
======================== ======================= ==============================================
======================== ================================================
Rules definition Expected result
======================== ================================================
No FROM (or from: []) Allow traffic from all pods from all namespaces
Ingress: {} Allow traffic from all namespaces
ingress: [] Deny all traffic
No ingress Blocks all traffic
======================== ================================================
Policy types definition
~~~~~~~~~~~~~~~~~~~~~~~
=============== ===================== ======================= ======================
PolicyType Spec Ingress/Egress Ingress generated rules Egress generated rules
=============== ===================== ======================= ======================
none none BLOCK ALLOW
none ingress Specific rules ALLOW
none egress Block Specific rules
none ingress, egress Specific rules Specific rules
ingress none Block ALLOW
ingress ingress Specific rules ALLOW
egress none ALLOW BLOCK
egress egress ALLOW Specific rules
Ingress, egress none BLOCK BLOCK
Ingress, egress ingress Specific rules BLOCK
Ingress, egress egress BLOCK Specific rules
Ingress, egress ingress,egress Specific rules Specific rules
=============== ===================== ======================= ======================