2017-03-31 02:02:16 +02:00
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/*
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* Copyright 2017 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.resolver.dns;
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2017-11-13 13:40:27 +01:00
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import io.netty.util.internal.PlatformDependent;
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2017-03-31 02:02:16 +02:00
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2018-11-16 10:37:29 +01:00
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import java.util.concurrent.TimeUnit;
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import java.util.concurrent.atomic.AtomicLong;
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2017-03-31 02:02:16 +02:00
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/**
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* Utility methods related to {@link DnsServerAddressStreamProvider}.
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*/
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public final class DnsServerAddressStreamProviders {
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2018-11-16 10:37:29 +01:00
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// We use 5 minutes which is the same as what OpenJDK is using in sun.net.dns.ResolverConfigurationImpl.
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private static final long REFRESH_INTERVAL = TimeUnit.MINUTES.toNanos(5);
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2017-03-31 02:02:16 +02:00
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// TODO(scott): how is this done on Windows? This may require a JNI call to GetNetworkParams
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// https://msdn.microsoft.com/en-us/library/aa365968(VS.85).aspx.
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private static final DnsServerAddressStreamProvider DEFAULT_DNS_SERVER_ADDRESS_STREAM_PROVIDER =
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2018-11-16 10:37:29 +01:00
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new DnsServerAddressStreamProvider() {
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private volatile DnsServerAddressStreamProvider currentProvider = provider();
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private final AtomicLong lastRefresh = new AtomicLong(System.nanoTime());
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@Override
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public DnsServerAddressStream nameServerAddressStream(String hostname) {
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long last = lastRefresh.get();
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DnsServerAddressStreamProvider current = currentProvider;
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if (System.nanoTime() - last > REFRESH_INTERVAL) {
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// This is slightly racy which means it will be possible still use the old configuration for a small
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// amount of time, but that's ok.
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if (lastRefresh.compareAndSet(last, System.nanoTime())) {
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current = currentProvider = provider();
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}
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}
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return current.nameServerAddressStream(hostname);
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}
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private DnsServerAddressStreamProvider provider() {
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2017-11-13 13:40:27 +01:00
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// If on windows just use the DefaultDnsServerAddressStreamProvider.INSTANCE as otherwise
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// we will log some error which may be confusing.
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2018-11-16 10:37:29 +01:00
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return PlatformDependent.isWindows() ? DefaultDnsServerAddressStreamProvider.INSTANCE :
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2017-11-13 13:40:27 +01:00
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UnixResolverDnsServerAddressStreamProvider.parseSilently();
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2018-11-16 10:37:29 +01:00
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}
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};
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2017-03-31 02:02:16 +02:00
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private DnsServerAddressStreamProviders() {
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}
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/**
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* A {@link DnsServerAddressStreamProvider} which inherits the DNS servers from your local host's configuration.
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* <p>
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* Note that only macOS and Linux are currently supported.
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* @return A {@link DnsServerAddressStreamProvider} which inherits the DNS servers from your local host's
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* configuration.
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*/
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public static DnsServerAddressStreamProvider platformDefault() {
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return DEFAULT_DNS_SERVER_ADDRESS_STREAM_PROVIDER;
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}
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}
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