*   <dt>An IPv6 "IPv4 mapped" address, {@code "::ffff:192.168.0.1"}.
 *   <dd>{@code 00 00 00 00 00 00 00 00 00 00 ff ff c0 a8 00 01}
 * </dl>
 *
 * <p>A few notes about IPv6 "IPv4 mapped" addresses and their observed use in Java.
 *
 * <p>"IPv4 mapped" addresses were originally a representation of IPv4 addresses for use on an IPv6
 * socket that could receive both IPv4 and IPv6 connections (by disabling the {@code IPV6_V6ONLY}

        .testEquals();
  }

  public void testRequireBracketsForIPv6() {
    // Bracketed IPv6 works fine.
    assertThat(HostAndPort.fromString("[::1]").requireBracketsForIPv6().getHost()).isEqualTo("::1");
    assertThat(HostAndPort.fromString("[::1]:80").requireBracketsForIPv6().getHost())
        .isEqualTo("::1");
    // Non-bracketed non-IPv6 works fine.

        .testEquals();
  }

  public void testRequireBracketsForIPv6() {
    // Bracketed IPv6 works fine.
    assertThat(HostAndPort.fromString("[::1]").requireBracketsForIPv6().getHost()).isEqualTo("::1");
    assertThat(HostAndPort.fromString("[::1]:80").requireBracketsForIPv6().getHost())
        .isEqualTo("::1");
    // Non-bracketed non-IPv6 works fine.

 * Prefer to alternate IP addresses from different address families, (IPv6 / IPv4), starting with IPv6.
 * Don't start a new attempt until 250 ms after the most recent attempt was started.
 * Keep whichever TCP connection succeeds first and cancel all the others.

    InetAddress ipv4 = InetAddresses.forString("1.2.3.4");
    assertThat(InetAddresses.getEmbeddedIPv4ClientAddress(testIp)).isEqualTo(ipv4);

    // Test 6to4 address.
    testIp = (Inet6Address) InetAddresses.forString("2002:0102:0304::1");
    assertTrue(InetAddresses.hasEmbeddedIPv4ClientAddress(testIp));
    ipv4 = InetAddresses.forString("1.2.3.4");

Go 1.26 added a new `urlstrictcolons` setting that controls whether `net/url.Parse`
allows malformed hostnames containing colons outside of a bracketed IPv6 address.
The default `urlstrictcolons=1` rejects URLs such as `http://localhost:1:2` or `http://::1/`.
Colons are permitted as part of a bracketed IPv6 address, such as `http://[::1]/`.

Go 1.26 enabled two additional post-quantum key exchange mechanisms:

domain.title = Fess

# Search Engine

# The type of search engine backend (e.g., default, opensearch).
search_engine.type=default
# The URL of the search engine HTTP endpoint.
# For IPv6 environments, use brackets around the IPv6 address (e.g., http://[::1]:9201)
search_engine.http.url=http://localhost:9201
# Path to SSL certificate authorities for secure HTTP connections.
search_engine.http.ssl.certificate_authorities=

- 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....

    assertThat(get.headers["Host"]).isNull()
    assertThat(get.headers[":authority"]).isEqualTo("any-host-name:$port")
    assertThat(get.url).isEqualTo(url)
  }

  /** Use a proxy to fake IPv6 connectivity, even if localhost doesn't have IPv6.  */
  private fun configureClientAndServerProxies(http2: Boolean) {
    server.useHttps(handshakeCertificates.sslSocketFactory())
    server.protocols =
      when {

  slightly stricter about what values will be accepted as IP addresses and network
  address ranges (“CIDR blocks”).
  
  In particular, octets within IPv4 addresses are not allowed to have any leading
  `0`s, and IPv4-mapped IPv6 values (e.g. `::ffff:192.168.0.1`) are forbidden.
  These sorts of values can potentially cause security problems when different