* The pod annotation `security.alpha.kubernetes.io/sysctls` now allows customization of namespaced and well isolated kernel parameters (sysctls), starting with `kernel.shm_rmid_forced`, `net.ipv4.ip_local_port_range` and `net.ipv4.tcp_syncookies` for Kubernetes 1.4. ([#27180](https://github.com/kubernetes/kubernetes/pull/27180), [@sttts](https://github.com/sttts))

- Fixed an issue in the Windows kube-proxy (winkernel) where IPv4 and IPv6 Service load balancers could be incorrectly shared, causing broken dual-stack Service behavior. The kube-proxy now tracks load balancers per IP family, enabling correct support for PreferDualStack and RequireDualStack Services on Windows nodes....

  semantics will probably change before the dual-stack feature goes GA, and users
  should look at ClusterIP or Endpoints, not IPFamily, to figure out if an existing
  Service is IPv4, IPv6, or dual-stack. ([#91527](https://github.com/kubernetes/kubernetes/pull/91527), [@danwinship](https://github.com/danwinship)) [SIG Apps and Network]

* Fixing a bug in OpenStack cloud provider, where dual stack deployments (IPv4 and IPv6) did not work well when using kubenet as the network plugin. ([#59749](https://github.com/kubernetes/kubernetes/pull/59749), [@zioproto](https://github.com/zioproto))

- Fixed an issue in the Windows kube-proxy (winkernel) where IPv4 and IPv6 Service load balancers could be incorrectly shared, causing broken dual-stack Service behavior. The kube-proxy now tracks load balancers per IP family, enabling correct support for PreferDualStack and RequireDualStack Services on Windows nodes....

* kubeadm now checks that IPv4/IPv6 forwarding is enabled ([#63872](https://github.com/kubernetes/kubernetes/pull/63872), [@kad](https://github.com/kad))

- PodLifecycleSleepAction is graduated to GA ([#128046](https://github.com/kubernetes/kubernetes/pull/128046), [@AxeZhan](https://github.com/AxeZhan)) [SIG Architecture, Node and Testing]
- Pods were allowed to use the `net.ipv4.tcp_rmem` and `net.ipv4.tcp_wmem` sysctl by default
  when the kernel version was 4.15 or higher. With the kernel 4.15 the sysctl became namespaced.

### Bug or Regression

- Fix a bug that caused to panic the apiserver when trying to allocate a Service with a dynamic ClusterIP and it has been configured with Service CIDRs with a /28 mask for IPv4 and a /124 mask for IPv6 ([#115334](https://github.com/kubernetes/kubernetes/pull/115334), [@aojea](https://github.com/aojea)) [SIG Network and Testing]

- Make kubectl command headers default for beta. ([#103238](https://github.com/kubernetes/kubernetes/pull/103238), [@seans3](https://github.com/seans3)) [SIG CLI]
- Mark `net.ipv4.ip_unprivileged_port_start` as safe `sysctl`. ([#103326](https://github.com/kubernetes/kubernetes/pull/103326), [@pacoxu](https://github.com/pacoxu))

pkg net, func FileConn(*os.File) (Conn, error)
pkg net, func FileListener(*os.File) (Listener, error)
pkg net, func FilePacketConn(*os.File) (PacketConn, error)
pkg net, func IPv4(uint8, uint8, uint8, uint8) IP
pkg net, func IPv4Mask(uint8, uint8, uint8, uint8) IPMask
pkg net, func InterfaceAddrs() ([]Addr, error)
pkg net, func InterfaceByIndex(int) (*Interface, error)