211dde4e08
Motivation: Sometimes DNS responses can be very large which mean they will not fit in a UDP packet. When this is happening the DNS server will set the TC flag (truncated flag) to tell the resolver that the response was truncated. When a truncated response was received we should allow to retry via TCP and use the received response (if possible) as a replacement for the truncated one. See https://tools.ietf.org/html/rfc7766. Modifications: - Add support for TCP fallback by allow to specify a socketChannelFactory / socketChannelType on the DnsNameResolverBuilder. If this is set to something different then null we will try to fallback to TCP. - Add decoder / encoder for TCP - Add unit tests Result: Support for TCP fallback as defined by https://tools.ietf.org/html/rfc7766 when using DnsNameResolver.
52 lines
1.7 KiB
Java
52 lines
1.7 KiB
Java
/*
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* Copyright 2019 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.channel.AddressedEnvelope;
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import io.netty.channel.Channel;
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import io.netty.handler.codec.dns.DatagramDnsQuery;
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import io.netty.handler.codec.dns.DnsQuery;
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import io.netty.handler.codec.dns.DnsQuestion;
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import io.netty.handler.codec.dns.DnsRecord;
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import io.netty.handler.codec.dns.DnsResponse;
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import io.netty.util.concurrent.Promise;
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import java.net.InetSocketAddress;
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final class DatagramDnsQueryContext extends DnsQueryContext {
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DatagramDnsQueryContext(DnsNameResolver parent, InetSocketAddress nameServerAddr, DnsQuestion question,
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DnsRecord[] additionals,
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Promise<AddressedEnvelope<DnsResponse, InetSocketAddress>> promise) {
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super(parent, nameServerAddr, question, additionals, promise);
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}
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@Override
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protected DnsQuery newQuery(int id) {
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return new DatagramDnsQuery(null, nameServerAddr(), id);
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}
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@Override
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protected Channel channel() {
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return parent().ch;
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}
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@Override
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protected String protocol() {
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return "UDP";
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}
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}
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