*/
  @Throws(IOException::class)
  internal fun connectTunnel(): ConnectResult {
    val nextTunnelRequest =
      createTunnel()
        ?: return ConnectResult(plan = this) // Success.

    // The proxy decided to close the connection after an auth challenge. Retry with different
    // auth credentials.
    rawSocket?.closeQuietly()

    val nextAttempt = attempt + 1
    return when {