* kubectl built for darwin from darwin now enables cgo to use the system-native C libraries for DNS resolution. Cross-compiled kubectl (e.g. from an official kubernetes release) still uses the go-native netgo DNS implementation.  ([#64219](https://github.com/kubernetes/kubernetes/pull/64219), [@ixdy](https://github.com/ixdy))

* Controller-manager --service-sync-period flag has been removed. (It was never used in the code and should have no user impact.) ([#59359](https://github.com/kubernetes/kubernetes/pull/59359), [@khenidak](https://github.com/khenidak))

- kube-apiserver:

- Kubernetes API Go types removed runtime use of the `github.com/gogo/protobuf` library, and are no longer registered into the global gogo type registry. Kubernetes API Go types were not suitable for use with the `google.golang.org/protobuf` library, and no longer implement `ProtoMessage()` by default to avoid accidental incompatible use. If removal of these marker methods impacts your use, it can be re-enabled for one more release with a `kubernetes_protomessage_one_more_release`...

kustomize, so there are a few backwards-incompatible changes, most of which are rare use cases, bug fixes with side effects, or things that have been deprecated for multiple releases already:
  
  - https://github.com/kubernetes-sigs/kustomize/pull/4911: Drop support for a very old, legacy style of patches. patches used to be allowed to be used as an alias for patchesStrategicMerge in kustomize v3. You now have to use patchesStrategicMerge explicitly, or update to the new syntax supported by patches....

<a href="#Assignment_statements">assignment</a> or
explicit <a href="#Conversions">conversion</a>.
</p>

<pre>
chan T          // can be used to send and receive values of type T
chan&lt;- float64  // can only be used to send float64s
&lt;-chan int      // can only be used to receive ints
</pre>

<p>
The <code>&lt;-</code> operator associates with the leftmost <code>chan</code>
possible:
</p>

  - All resources under `apps/v1beta1` and `apps/v1beta2` - use `apps/v1` instead
  - `daemonsets`, `deployments`, `replicasets` resources under `extensions/v1beta1` - use `apps/v1` instead
  - `networkpolicies` resources under `extensions/v1beta1` - use `networking.k8s.io/v1` instead

* Nodes can now report two additional address types in their status: InternalDNS and ExternalDNS. The apiserver can use `--kubelet-preferred-address-types` to give priority to the type of address it uses to reach nodes. ([#34259](https://github.com/kubernetes/kubernetes/pull/34259), [@liggitt](https://github.com/liggitt))

### Quality of Service for memory resources

    - All resources under `apps/v1beta1` and `apps/v1beta2` - use `apps/v1` instead
    - `daemonsets`, `deployments`, `replicasets` resources under `extensions/v1beta1` - use `apps/v1` instead
    - `networkpolicies` resources under `extensions/v1beta1` - use `networking.k8s.io/v1` instead
    - `podsecuritypolicies` resources under `extensions/v1beta1` - use `policy/v1beta1` instead