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1   /*
2    * Copyright 2017 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package io.netty.resolver.dns;
17  
18  import io.netty.util.internal.PlatformDependent;
19  import io.netty.util.internal.UnstableApi;
20  
21  /**
22   * Utility methods related to {@link DnsServerAddressStreamProvider}.
23   */
24  @UnstableApi
25  public final class DnsServerAddressStreamProviders {
26      // TODO(scott): how is this done on Windows? This may require a JNI call to GetNetworkParams
27      // https://msdn.microsoft.com/en-us/library/aa365968(VS.85).aspx.
28      private static final DnsServerAddressStreamProvider DEFAULT_DNS_SERVER_ADDRESS_STREAM_PROVIDER =
29              // If on windows just use the DefaultDnsServerAddressStreamProvider.INSTANCE as otherwise
30              // we will log some error which may be confusing.
31              PlatformDependent.isWindows() ? DefaultDnsServerAddressStreamProvider.INSTANCE :
32                      UnixResolverDnsServerAddressStreamProvider.parseSilently();
33  
34      private DnsServerAddressStreamProviders() {
35      }
36  
37      /**
38       * A {@link DnsServerAddressStreamProvider} which inherits the DNS servers from your local host's configuration.
39       * <p>
40       * Note that only macOS and Linux are currently supported.
41       * @return A {@link DnsServerAddressStreamProvider} which inherits the DNS servers from your local host's
42       * configuration.
43       */
44      public static DnsServerAddressStreamProvider platformDefault() {
45          return DEFAULT_DNS_SERVER_ADDRESS_STREAM_PROVIDER;
46      }
47  }