net.core.netdev_max_backlog=250000
net.core.somaxconn=16384
net.ipv4.tcp_syncookies=0
net.ipv4.tcp_max_syn_backlog=16384
net.core.wmem_max=4194304
net.core.rmem_max=4194304
net.core.rmem_default=4194304
net.core.wmem_default=4194304
net.ipv4.tcp_rmem="4096 87380 4194304"
net.ipv4.tcp_wmem="4096 65536 4194304"

# Reduce CPU utilization
net.ipv4.tcp_timestamps=0

# Increase throughput
net.ipv4.tcp_sack=1

# Low latency mode for TCP

  // and host bits. For example an IPv4 address of 192.168.0.0/24, splits the
  // address into 24 bits for the network portion and 8 bits for the host portion.
  // To allocate 256 IPs, set this field to 8 (a /24 mask for IPv4 or a /120 for IPv6).
  // Minimum value is 4 (16 IPs).
  // This field is immutable.
  // +required
  optional int32 perNodeHostBits = 2;

  // ipv4 defines an IPv4 IP block in CIDR notation(e.g. "10.0.0.0/8").

fun reorderForHappyEyeballs(addresses: List<InetAddress>): List<InetAddress> {
  if (addresses.size < 2) {
    return addresses
  }

  val (ipv6, ipv4) = addresses.partition { it is Inet6Address }

  return if (ipv6.isEmpty() || ipv4.isEmpty()) {
    addresses
  } else {
    interleave(ipv6, ipv4)
  }

    val allAddresses = mutableListOf<InetAddress>()
    var exception: Exception? = null
    val latch = CountDownLatch(1)

    // assumes an IPv4 address
    AndroidAsyncDns.IPv4.query(
      hostname,
      object : AsyncDns.Callback {
        override fun onResponse(
          hostname: String,
          addresses: List<InetAddress>,
        ) {

class FakeDns : Dns {
  private val hostAddresses: MutableMap<String, List<InetAddress>> = mutableMapOf()
  private val requestedHosts: MutableList<String> = mutableListOf()
  private var nextAddress = 0xff000064L // 255.0.0.100 in IPv4; ::ff00:64 in IPv6.

  /** Sets the results for `hostname`.  */
  operator fun set(
    hostname: String,
    addresses: List<InetAddress>,
  ): FakeDns {
    hostAddresses[hostname] = addresses
    return this

  )

  /**
   * Callback to receive results from the DNS Queries.
   */
  @ExperimentalOkHttpApi
  interface Callback {
    /**
     * Return addresses for a dns query for a single class of IPv4 (A) or IPv6 (AAAA).
     * May be an empty list indicating that the host is unreachable.
     */
    fun onResponse(
      hostname: String,
      addresses: List<InetAddress>,
    )

    /**

				// Number of probes.
				// ~ cat /proc/sys/net/ipv4/tcp_keepalive_probes (defaults to 9, we reduce it to 5)
				_ = syscall.SetsockoptInt(fd, syscall.IPPROTO_TCP, syscall.TCP_KEEPCNT, 5)

				// Wait time after successful probe in seconds.
				// ~ cat /proc/sys/net/ipv4/tcp_keepalive_intvl (defaults to 75 secs, we reduce it to 15 secs)

      ),
    ).isEqualTo("255.255.255.255")
  }

  private fun decodeIpv6(input: String): ByteArray? = decodeIpv6(input, 0, input.length)

  @Test
  fun testToCanonicalHost() {
    // IPv4
    assertThat("127.0.0.1".toCanonicalHost()).isEqualTo("127.0.0.1")
    assertThat("1.2.3.4".toCanonicalHost()).isEqualTo("1.2.3.4")

    // IPv6
    assertThat("::1".toCanonicalHost()).isEqualTo("::1")

          initCause(e)
        },
      )
    }
  }

  @ExperimentalOkHttpApi
  companion object {
    @RequiresApi(Build.VERSION_CODES.Q)
    val IPv4 = AndroidAsyncDns(dnsClass = AsyncDns.DnsClass.IPV4)

    @RequiresApi(Build.VERSION_CODES.Q)
    val IPv6 = AndroidAsyncDns(dnsClass = AsyncDns.DnsClass.IPV6)
  }

@Config(shadows = [ShadowDnsResolver::class], sdk = [34])
@RunWith(RobolectricTestRunner::class)
class AndroidAsyncDnsTest {
  @Test
  fun testDnsRequestInvalid() {
    val asyncDns = AndroidAsyncDns.IPv4
    val shadowDns: ShadowDnsResolver = Shadow.extract(asyncDns.resolver)

    shadowDns.responder = {
      throw IllegalArgumentException("Network.fromNetworkHandle refusing to instantiate NETID_UNSET Network.")
    }