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

- Pod SecurityContext sysctls name parameter for update requests where the existing object's sysctl contains slashes and kubelet sysctl whitelist support contains slashes. ([#102393](https://github.com/kubernetes/kubernetes/pull/102393), [@mengjiao-liu](https://github.com/mengjiao-liu)) [SIG Apps, Auth, Node, Storage 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.

  
  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)

- 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

- Improved algorithm for selecting `best` non-preferred hint in the TopologyManager ([#108154](https://github.com/kubernetes/kubernetes/pull/108154), [@klueska](https://github.com/klueska))
- Kube-proxy doesn't set the sysctl `net.ipv4.conf.all.route_localnet=1` if no IPv4 loopback address is selected by the `nodePortAddresses` configuration parameter. ([#107684](https://github.com/kubernetes/kubernetes/pull/107684), [@aojea](https://github.com/aojea))

- Introduced the flag `--ipvs-strict-arp` to configure stricter ARP sysctls, defaulting to false to preserve existing behaviors. This was enabled by default in 1.13.0, which impacted a few CNI plugins. ([#75295](https://github.com/kubernetes/kubernetes/pull/75295), [@lbernail](https://github.com/lbernail))