and “net.ipv4.tcp_keepalive_probes“ sysctl by default; Pod Security Admission
  allows this sysctl in `v1.29+` versions of the baseline and restricted policies. ([#121240](https://github.com/kubernetes/kubernetes/pull/121240), [@HirazawaUi](https://github.com/HirazawaUi))
- `kubelet` now allows pods to use the `net.ipv4.tcp_keepalive_time` sysctl by default

- Changes behaviour of kube-proxy start; does not attempt to set specific `sysctl` values (which does not work in recent Kernel versions anymore in non-init namespaces), when the current sysctl values are already set higher. ([#103174](https://github.com/kubernetes/kubernetes/pull/103174), [@Napsty](https://github.com/Napsty))

- 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.

* The Sysctls experimental feature has been promoted to beta (enabled by default via the `Sysctls` feature flag). PodSecurityPolicy and Pod objects now have fields for specifying and controlling sysctls. Alpha sysctl annotations will be ignored by 1.11+ kubelets. All alpha sysctl annotations in existing deployments must be converted to API fields to be effective. ([#6371](https://github.com/kubernetes/kubernetes/pull/63717), [@ingvagabund](https://github.com/ingvagabund))

  
  When the feature gate is enabled, kubelet ignores errors that happens during setting the following sysctl values: `vm.overcommit_memory`, `vm.panic_on_oom`, `kernel.panic`, `kernel.panic_on_oops`, `kernel.keys.root_maxkeys`, `kernel.keys.root_maxbytes`. (These sysctl values for the host, not for the containers)
  
  kubelet also ignores an error during opening `/dev/kmsg`.

- Kubelet allows pods to use the `net.ipv4.ip_local_reserved_ports` sysctl by default and the minimal kernel version is 3.16; Pod Security admission allows this sysctl in v1.27+ versions of the baseline and restricted policies. ([#115374](https://github.com/kubernetes/kubernetes/pull/115374), [@pacoxu](https://github.com/pacoxu)) [SIG Auth, Network and Node]

## Urgent Upgrade Notes 

### (No, really, you MUST read this before you upgrade)

pkg syscall (darwin-arm64), func Syscall9(uintptr, uintptr, uintptr, uintptr, uintptr, uintptr, uintptr, uintptr, uintptr, uintptr) (uintptr, uintptr, Errno)
pkg syscall (darwin-arm64), func Sysctl(string) (string, error)
pkg syscall (darwin-arm64), func SysctlUint32(string) (uint32, error)
pkg syscall (darwin-arm64), func TimevalToNsec(Timeval) int64
pkg syscall (darwin-arm64), func Truncate(string, int64) error

- Pod SecurityContext and PodSecurityPolicy supports slash as sysctl separator. ([#106834](https://github.com/kubernetes/kubernetes/pull/106834), [@mengjiao-liu](https://github.com/mengjiao-liu)) [SIG Apps, Architecture, Auth, Node, Security and Testing]

pkg syscall (netbsd-arm64-cgo), func Syscall(uintptr, uintptr, uintptr, uintptr) (uintptr, uintptr, Errno)
pkg syscall (netbsd-arm64-cgo), func Sysctl(string) (string, error)
pkg syscall (netbsd-arm64-cgo), func SysctlUint32(string) (uint32, error)
pkg syscall (netbsd-arm64-cgo), func TimevalToNsec(Timeval) int64