companion object {
    /**
     * A DNS that uses [InetAddress.getAllByName] to ask the underlying operating system to
     * lookup IP addresses. Most custom [Dns] implementations should delegate to this instance.
     */
    @JvmField
    val SYSTEM: Dns = DnsSystem()

    private class DnsSystem : Dns {
      override fun lookup(hostname: String): List<InetAddress> {
        try {

    .url("https://dns.google/dns-query".toHttpUrl())
    .bootstrapDnsHosts(InetAddress.getByName("8.8.4.4"), InetAddress.getByName("8.8.8.8"))
    .build()

  val client = bootstrapClient.newBuilder().dns(dns).build()
```

    server.useHttps(handshakeCertificates.sslSocketFactory())

    val dns =
      Dns {
        Dns.SYSTEM.lookup(server.hostName)
      }

    val client =
      clientTestRule.newClientBuilder()
        .sslSocketFactory(
          handshakeCertificates.sslSocketFactory(),
          handshakeCertificates.trustManager,
        )
        .dns(dns)
        .build()

    server.enqueue(MockResponse())

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])
  }

 */
package okhttp3

import assertk.assertThat
import assertk.assertions.containsExactly
import java.net.InetAddress
import java.net.UnknownHostException
import okio.Buffer

class FakeDns : Dns {
  private val hostAddresses: MutableMap<String, List<InetAddress>> = mutableMapOf()
  private val requestedHosts: MutableList<String> = mutableListOf()

connections.** Stale or canceled connections were incorrectly attempted when they shouldn't have
been, leading to rare cases of infinite retries. Please upgrade to this release!

 *  Fix: don't return stale DNS entries in `DnsOverHttps`. We were caching DNS results indefinitely
    rather than the duration specified in the response's cache-control header.
 *  Fix: Verify certificate IP addresses in canonical form. When a server presents a TLS certificate

  private const val INITIAL_N = 0x80

  /**
   * Returns null if any label is oversized so much that the encoder cannot encode it without
   * integer overflow. This will not return null for labels that fit within the DNS size
   * limits.
   */
  fun encode(string: String): String? {
    var pos = 0
    val limit = string.length
    val result = Buffer()

    while (pos < limit) {

/** Returns true if this string is not a host name and might be an IP address. */
fun String.canParseAsIpAddress(): Boolean = VERIFY_AS_IP_ADDRESS.matches(this)

/**
 * Returns true if the length is not valid for DNS (empty or greater than 253 characters), or if any
 * label is longer than 63 characters. Trailing dots are okay.
 */
internal fun String.containsInvalidLabelLengths(): Boolean {
  if (length !in 1..253) return true

    return true // The caller's address can be carried by this connection.
  }

  /**
   * Returns true if this connection's route has the same address as any of [candidates]. This
   * requires us to have a DNS address for both hosts, which only happens after route planning. We
   * can't coalesce connections that use a proxy, since proxies don't tell us the origin server's IP
   * address.
   */

      .isEqualTo(generalNameIpAddress to localhost)
    assertThat(CertificateAdapters.generalName.toDer(generalNameIpAddress to localhost))
      .isEqualTo(bytes)
  }

  @Test fun `choice dns`() {
    val bytes = "820b6578616d706c652e636f6d".decodeHex()
    assertThat(CertificateAdapters.generalName.fromDer(bytes))
      .isEqualTo(generalNameDnsName to "example.com")