### **Network**

#### **IPv6**

*   [alpha] IPv6 support has been added. Notable IPv6 support details include:
    *   Support for IPv6-only Kubernetes cluster deployments. **<span style="text-decoration:underline;">Note:</span>** This feature does not provide dual-stack support.
    *   Support for IPv6 Kubernetes control and data planes.
    *   Support for Kubernetes IPv6 cluster deployments using kubeadm.

 * authentication.
 *
 * ### Host
 *
 * The host identifies the webserver that serves the URL's resource. It is either a hostname like
 * `square.com` or `localhost`, an IPv4 address like `192.168.0.1`, or an IPv6 address like `::1`.
 *
 * Usually a webserver is reachable with multiple identifiers: its IP addresses, registered

OkHttp perseveres when the network is troublesome: it will silently recover from common connection
problems. If your service has multiple IP addresses, OkHttp will attempt alternate addresses if the
first connect fails. This is necessary for IPv4+IPv6 and services hosted in redundant data
centers. OkHttp supports modern TLS features (TLS 1.3, ALPN, certificate pinning). It can be
configured to fall back for broad connectivity.

    * DualStack:
    * => IPv4 BackendPool name == clusterName
    * => IPv6 BackendPool name == <clusterName>-IPv6
    * This result into:
    * - clusters moving from IPv4 to duakstack will require no changes

- File content check for IPV4 is now enabled by default, and the check of IPV4 or IPV6 is done for `kubeadm init` or `kubeadm join` only in case the user intends to create a cluster to support that kind of IP address family ([#115420](https://github.com/kubernetes/kubernetes/pull/115420), [@chendave](http...

- On single-stack configured (IPv4 or IPv6, but not both) clusters, Services which are both headless (no clusterIP) and selectorless (empty or undefined selector) will report `ipFamilyPolicy RequireDualStack` and will have entries in `ipFamilies[]` for both IPv4 and IPv6.  This is a change from alpha, but does not have any impact on the manually-specified Endpoints and EndpointSlices for the Service....

### IPv4/IPv6 run

http://%zz%66%a.com

# If we get an invalid character that has been escaped.
http://%25
http://hello%00

# Escaped numbers should be treated like IP addresses if they are.
# No special handling for IPv4 or IPv4-like URLs
http://%30%78%63%30%2e%30%32%35%30.01  s:http p:/ h:192.168.0.1
http://%30%78%63%30%2e%30%32%35%30.01%2e  s:http p:/ h:0xc0.0250.01.
http://192.168.0.257

    assertThat(localVerifier.verify("\uD83D\uDCA9.com", session)).isFalse()
  }

  @Test fun verifyAsIpAddress() {
    // IPv4
    assertThat("127.0.0.1".canParseAsIpAddress()).isTrue()
    assertThat("1.2.3.4".canParseAsIpAddress()).isTrue()

    // IPv6
    assertThat("::1".canParseAsIpAddress()).isTrue()
    assertThat("2001:db8::1".canParseAsIpAddress()).isTrue()

 *  Fix: Recover gracefully when a coalesced connection immediately goes unhealthy.
 *  Fix: Defer the `SecurityException` when looking up the default proxy selector.
 *  Fix: Don't use brackets formatting IPv6 host names in MockWebServer.
 *  Fix: Don't permit cache iterators to remove entries that are being written.


## Version 4.0.1

_2019-07-10_