- EmptyDir memory backed volumes are sized as the minimum of pod allocatable memory on a host and an optional explicit user provided value. ([#100319](https://github.com/kubernetes/kubernetes/pull/100319), [@derekwaynecarr](https://github.com/derekwaynecarr)) [SIG Node]

- Mark Job onPodConditions as optional in pod failure policy ([#120209](https://github.com/kubernetes/kubernetes/pull/120209), [@mimowo](https://github.com/mimowo)) [SIG API Machinery and Apps]

### Feature

* OpenStack cloud provider supports Cinder v3 API. ([#52910](https://github.com/kubernetes/kubernetes/pull/52910), [@FengyunPan](https://github.com/FengyunPan))
* kube-up: Add optional addon CoreDNS.  ([#55728](https://github.com/kubernetes/kubernetes/pull/55728), [@rajansandeep](https://github.com/rajansandeep))
    * Install CoreDNS instead of kube-dns by setting CLUSTER_DNS_CORE_DNS value to 'true'.

### Network

* Fixed kube-proxy to work correctly with iptables 1.6.2 and later. ([#60978](https://github.com/kubernetes/kubernetes/pull/60978), [@danwinship](https://github.com/danwinship))

* Makes the kube-dns addon optional so that users can deploy their own DNS solution. ([#57113](https://github.com/kubernetes/kubernetes/pull/57113), [@wwwtyro](https://github.com/wwwtyro))

- The kube-apiserver's healthz now takes in an optional query parameter which allows you to disable health checks from causing healthz failures.  ([#70676](https://github.com/kubernetes/kubernetes/pull/70676), [@logicalhan](https://github.com/logicalhan))

* Fix a potential bug that scheduler preempts unnecessary pods. ([#70898](https://github.com/kubernetes/kubernetes/pull/70898), [@Huang-Wei](https://github.com/Huang-Wei))
* The kube-apiserver's healthz now takes in an optional query parameter which allows you to disable health checks from causing healthz failures.  ([#70676](https://github.com/kubernetes/kubernetes/pull/70676), [@logicalhan](https://github.com/logicalhan))

- Mark Job onPodConditions as optional in pod failure policy ([#120208](https://github.com/kubernetes/kubernetes/pull/120208), [@mimowo](https://github.com/mimowo)) [SIG API Machinery and Apps]

### Feature

- Added optional `--detect-local-mode` flag to kube-proxy. Valid values are "ClusterCIDR" (default matching previous behavior) and "NodeCIDR" ([#87748](https://github.com/kubernetes/kubernetes/pull/87748), [@satyasm](https://github.com/satyasm)) [SIG Cluster Lifecycle,...

* Mark the LBaaS v1 of OpenStack cloud provider deprecated. ([#52821](https://github.com/kubernetes/kubernetes/pull/52821), [@FengyunPan](https://github.com/FengyunPan))
* Mark image as deliberately optional in v1 Container struct.  Many objects in the Kubernetes API inherit the container struct and only Pods require the field to be set. ([#48406](https://github.com/kubernetes/kubernetes/pull/48406), [@gyliu513](https://github.com/gyliu513))

* The `serverAddressByClientCIDRs` property in `metav1.APIGroup`(discovery API) is now optional instead of required. ([#61963](https://github.com/kubernetes/kubernetes/pull/61963), [@roycaihw](https://github.com/roycaihw))