e074df2ae6
Motivation: Recently DnsServerAddressStreamProvider was introduced to allow control for each query as to which DNS server should be used for resolution to respect the local host's default DNS server configuration. However resolver-dns also accepts a stream of DNS servers to use by default, but this stream is not host name aware. This creates an ambiguity as to which method is used to determine the DNS server to user during resolution, and in which order. We can remove this ambiguity and provide a more general API by just supporting DnsServerAddressStreamProvider. Modifications: - Remove the fixed DnsServerAddresses and instead only accept a DnsServerAddressStreamProvider. - Add utility methods to help use DnsServerAddressStreamProvider for a single entry, a list of entries, and get the default for the current machine. Result: Fixes https://github.com/netty/netty/issues/6573.
57 lines
2.0 KiB
Java
57 lines
2.0 KiB
Java
/*
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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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import io.netty.util.internal.UnstableApi;
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import java.util.List;
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/**
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* A {@link DnsServerAddressStreamProvider} which iterates through a collection of
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* {@link DnsServerAddressStreamProvider} until the first non-{@code null} result is found.
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*/
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@UnstableApi
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public final class MultiDnsServerAddressStreamProvider implements DnsServerAddressStreamProvider {
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private final DnsServerAddressStreamProvider[] providers;
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/**
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* Create a new instance.
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* @param providers The providers to use for DNS resolution. They will be queried in order.
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*/
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public MultiDnsServerAddressStreamProvider(List<DnsServerAddressStreamProvider> providers) {
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this.providers = providers.toArray(new DnsServerAddressStreamProvider[0]);
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}
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/**
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* Create a new instance.
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* @param providers The providers to use for DNS resolution. They will be queried in order.
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*/
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public MultiDnsServerAddressStreamProvider(DnsServerAddressStreamProvider... providers) {
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this.providers = providers.clone();
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}
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@Override
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public DnsServerAddressStream nameServerAddressStream(String hostname) {
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for (DnsServerAddressStreamProvider provider : providers) {
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DnsServerAddressStream stream = provider.nameServerAddressStream(hostname);
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if (stream != null) {
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return stream;
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}
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}
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return null;
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}
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}
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