Kotlin calling OkHttp 3.x:

```kotlin
val client = OkHttpClient.Builder()
    .dns { hostname -> InetAddress.getAllByName(hostname).toList() }
    .build()
```

Kotlin calling OkHttp 4.x:

```kotlin
val client = OkHttpClient.Builder()
    .dns(object : Dns {
      override fun lookup(hostname: String) =
          InetAddress.getAllByName(hostname).toList()
    })

      }

    /**
     * Sets the DNS service used to lookup IP addresses for hostnames.
     *
     * If unset, the [system-wide default][Dns.SYSTEM] DNS will be used.
     */
    fun dns(dns: Dns) =
      apply {
        if (dns != this.dns) {
          this.routeDatabase = null
        }
        this.dns = dns
      }

    /**

        .build(),
    )
    server.enqueue(MockResponse())
    val dns = FakeDns()
    dns["fakeurl"] = client.dns.lookup(server.hostName)
    dns["www.fakeurl"] = client.dns.lookup(server.hostName)
    client =
      client
        .newBuilder()
        .dns(dns)
        .build()
    val call =
      client.newCall(
        Request
          .Builder()

  @AfterEach
  fun tearDown() {
    factory.close()
  }

  @Test @Disabled
  fun address() {
    val address: Address = factory.newAddress()
    val url: HttpUrl = address.url()
    val dns: Dns = address.dns()
    val socketFactory: SocketFactory = address.socketFactory()
    val proxyAuthenticator: Authenticator = address.proxyAuthenticator()
    val protocols: List<Protocol> = address.protocols()

        override fun peek(): MockResponse = TODO()

        override fun shutdown() = TODO()
      }
  }

  @Test
  fun dns() {
    var dns: Dns = Dns { TODO() }

    val system: Dns = Dns.SYSTEM
  }

  @Test
  fun eventListener() {
    val eventListener =
      object : EventListener() {
        override fun callStart(call: Call) = TODO()

  )
  fun url(): HttpUrl = url

  @JvmName("-deprecated_dns")
  @Deprecated(
    message = "moved to val",
    replaceWith = ReplaceWith(expression = "dns"),
    level = DeprecationLevel.ERROR,
  )
  fun dns(): Dns = dns

  @JvmName("-deprecated_socketFactory")
  @Deprecated(
    message = "moved to val",
    replaceWith = ReplaceWith(expression = "socketFactory"),

      ),
    )
    server!!.enqueue(MockResponse())
    val dns = FakeDns()
    dns["fakeurl"] = client.dns.lookup(server!!.hostName)
    dns["www.fakeurl"] = client.dns.lookup(server!!.hostName)
    client =
      client
        .newBuilder()
        .dns(dns)
        .build()
    val call =
      client.newCall(
        Request
          .Builder()

...
01-01 12:53:32.811 10999 11089 D OkHttp  : [49 ms] responseHeadersEnd: Response{protocol=h2, code=200, message=, url=https://1.1.1.1/dns-query?dns=AAABAAABAAAAAAAAA3d3dwhmYWNlYm9vawNjb20AABwAAQ}
01-01 12:53:32.811 10999 11089 D OkHttp  : [49 ms] responseBodyStart
01-01 12:53:32.811 10999 11089 D OkHttp  : [49 ms] responseBodyEnd: byteCount=128

package okhttp3.internal

import java.net.InetAddress
import okhttp3.Dns

/**
 * A network that always resolves two IP addresses per host. Use this when testing route selection
 * fallbacks to guarantee that a fallback address is available.
 */
class DoubleInetAddressDns : Dns {
  override fun lookup(hostname: String): List<InetAddress> {
    val addresses = Dns.SYSTEM.lookup(hostname)
    return listOf(addresses[0], addresses[0])
  }

@Tag("Slowish")
class DnsOverHttpsTest {
  @RegisterExtension
  val platform = PlatformRule()

  @StartStop
  private val server = MockWebServer()

  private lateinit var dns: Dns
  private val cacheFs = FakeFileSystem()
  private val eventListener = RecordingEventListener()
  private val bootstrapClient =
    OkHttpClient
      .Builder()