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))

* `kubectl port-forward` now supports specifying a service to port forward to, as in `kubectl port-forward svc/myservice 8443:443`. Additional support has also been added for looking up targetPort for a service, as well as enabling using svc/name to select a pod. ([#59809](https://github.com/kubernetes/kubernetes/pull/59809),...

- Added a path `/header?key=` to `agnhost netexec` allowing one to view what the header value is of the incoming request.

  Ex:
  ```
  $ curl -H "X-Forwarded-For: something" 172.17.0.2:8080/header?key=X-Forwarded-For
  something
  ```
   ([#107796](https://github.com/kubernetes/kubernetes/pull/107796), [@alexanderConstantinescu](https://github.com/alexanderConstantinescu))

## Detailed Bug Fixes And Changes

### API Machinery

- client-go: `PortForwarder.GetPorts()` now contain correct local port if no local port was initially specified when setting up the port forwarder ([#73676](https://github.com/kubernetes/kubernetes/pull/73676), [@martin-helmich](https://github.com/martin-helmich))

## Dependencies

### Added

- Fixed a bug where startupProbe stopped working after a container's first restart ([#101093](https://github.com/kubernetes/kubernetes/pull/101093), [@wzshiming](https://github.com/wzshiming)) [SIG Node]
- Fixed port-forward memory leak for long-running and heavily used connections. ([#99839](https://github.com/kubernetes/kubernetes/pull/99839), [@saschagrunert](https://github.com/saschagrunert)) [SIG API Machinery and Node]

* Use full package path for definition name in OpenAPI spec ([#40124](https://github.com/kubernetes/kubernetes/pull/40124), [@mbohlool](https://github.com/mbohlool))
* Follow redirects for streaming requests (exec/attach/port-forward) in the apiserver by default (alpha -> beta). ([#40039](https://github.com/kubernetes/kubernetes/pull/40039), [@timstclair](https://github.com/timstclair))

* Created a new `dryRun` query parameter for mutating endpoints. If the parameter is set, then the query will be rejected, as the feature is not implemented yet. This will allow forward compatibility with future clients; otherwise, future clients talking with older apiservers might end up modifying a resource even if they include the `dryRun` query parameter. ([#63557](https://github.com/kubernetes/kubernetes/pull/63557), [@apel...

// PodPortForwardOptions is the query options to a Pod's port forward call
// when using WebSockets.
// The `port` query parameter must specify the port or
// ports (comma separated) to forward over.
// Port forwarding over SPDY does not use these options. It requires the port
// to be passed in the `port` header as part of request.
message PodPortForwardOptions {
  // List of ports to forward
  // Required when using WebSockets

### Other (Cleanup or Flake)

### Instrumentation