1672b6d12c
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.
61 lines
2.2 KiB
Java
61 lines
2.2 KiB
Java
/*
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* Copyright 2015 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.handler.codec.dns;
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import io.netty.channel.ChannelHandler;
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import io.netty.channel.ChannelHandlerContext;
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import io.netty.channel.socket.DatagramPacket;
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import io.netty.handler.codec.MessageToMessageDecoder;
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import io.netty.util.internal.UnstableApi;
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import java.net.InetSocketAddress;
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import java.util.List;
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/**
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* Decodes a {@link DatagramPacket} into a {@link DatagramDnsResponse}.
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*/
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@UnstableApi
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@ChannelHandler.Sharable
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public class DatagramDnsResponseDecoder extends MessageToMessageDecoder<DatagramPacket> {
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private final DnsResponseDecoder<InetSocketAddress> responseDecoder;
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/**
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* Creates a new decoder with {@linkplain DnsRecordDecoder#DEFAULT the default record decoder}.
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*/
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public DatagramDnsResponseDecoder() {
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this(DnsRecordDecoder.DEFAULT);
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}
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/**
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* Creates a new decoder with the specified {@code recordDecoder}.
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*/
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public DatagramDnsResponseDecoder(DnsRecordDecoder recordDecoder) {
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this.responseDecoder = new DnsResponseDecoder<InetSocketAddress>(recordDecoder) {
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@Override
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protected DnsResponse newResponse(InetSocketAddress sender, InetSocketAddress recipient,
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int id, DnsOpCode opCode, DnsResponseCode responseCode) {
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return new DatagramDnsResponse(sender, recipient, id, opCode, responseCode);
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}
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};
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}
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@Override
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protected void decode(ChannelHandlerContext ctx, DatagramPacket packet, List<Object> out) throws Exception {
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out.add(responseDecoder.decode(packet.sender(), packet.recipient(), packet.content()));
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}
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}
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