2015-03-16 07:46:14 +01:00
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/*
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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.buffer.ByteBuf;
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2016-04-12 14:22:41 +02:00
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import io.netty.util.internal.UnstableApi;
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2015-03-16 07:46:14 +01:00
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/**
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* The default {@link DnsRecordDecoder} implementation.
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*
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* @see DefaultDnsRecordEncoder
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*/
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2016-04-12 14:22:41 +02:00
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@UnstableApi
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2015-03-16 07:46:14 +01:00
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public class DefaultDnsRecordDecoder implements DnsRecordDecoder {
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2016-04-01 13:47:15 +02:00
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static final String ROOT = ".";
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2015-03-16 07:46:14 +01:00
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/**
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* Creates a new instance.
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*/
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protected DefaultDnsRecordDecoder() { }
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@Override
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public final DnsQuestion decodeQuestion(ByteBuf in) throws Exception {
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String name = decodeName(in);
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DnsRecordType type = DnsRecordType.valueOf(in.readUnsignedShort());
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int qClass = in.readUnsignedShort();
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return new DefaultDnsQuestion(name, type, qClass);
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}
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@Override
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public final <T extends DnsRecord> T decodeRecord(ByteBuf in) throws Exception {
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2015-07-12 12:34:05 +02:00
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final int startOffset = in.readerIndex();
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2015-03-16 07:46:14 +01:00
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final String name = decodeName(in);
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2015-07-12 12:34:05 +02:00
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final int endOffset = in.writerIndex();
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2019-08-17 09:58:22 +02:00
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if (endOffset - in.readerIndex() < 10) {
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2015-07-12 12:34:05 +02:00
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// Not enough data
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in.readerIndex(startOffset);
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return null;
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}
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2015-03-16 07:46:14 +01:00
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final DnsRecordType type = DnsRecordType.valueOf(in.readUnsignedShort());
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final int aClass = in.readUnsignedShort();
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final long ttl = in.readUnsignedInt();
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final int length = in.readUnsignedShort();
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final int offset = in.readerIndex();
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2015-07-12 12:34:05 +02:00
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if (endOffset - offset < length) {
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// Not enough data
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in.readerIndex(startOffset);
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return null;
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}
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2015-03-16 07:46:14 +01:00
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@SuppressWarnings("unchecked")
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T record = (T) decodeRecord(name, type, aClass, ttl, in, offset, length);
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in.readerIndex(offset + length);
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return record;
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}
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/**
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* Decodes a record from the information decoded so far by {@link #decodeRecord(ByteBuf)}.
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*
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* @param name the domain name of the record
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* @param type the type of the record
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* @param dnsClass the class of the record
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* @param timeToLive the TTL of the record
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* @param in the {@link ByteBuf} that contains the RDATA
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* @param offset the start offset of the RDATA in {@code in}
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* @param length the length of the RDATA
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*
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* @return a {@link DnsRawRecord}. Override this method to decode RDATA and return other record implementation.
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*/
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protected DnsRecord decodeRecord(
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String name, DnsRecordType type, int dnsClass, long timeToLive,
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ByteBuf in, int offset, int length) throws Exception {
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2016-10-18 21:51:53 +02:00
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// DNS message compression means that domain names may contain "pointers" to other positions in the packet
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// to build a full message. This means the indexes are meaningful and we need the ability to reference the
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// indexes un-obstructed, and thus we cannot use a slice here.
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// See https://www.ietf.org/rfc/rfc1035 [4.1.4. Message compression]
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2016-02-28 20:33:16 +01:00
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if (type == DnsRecordType.PTR) {
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2016-10-18 21:51:53 +02:00
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return new DefaultDnsPtrRecord(
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name, dnsClass, timeToLive, decodeName0(in.duplicate().setIndex(offset, offset + length)));
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2016-02-28 20:33:16 +01:00
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}
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2019-07-02 19:38:51 +02:00
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if (type == DnsRecordType.CNAME || type == DnsRecordType.NS) {
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return new DefaultDnsRawRecord(name, type, dnsClass, timeToLive,
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DnsCodecUtil.decompressDomainName(
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in.duplicate().setIndex(offset, offset + length)));
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}
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2015-03-16 07:46:14 +01:00
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return new DefaultDnsRawRecord(
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2016-10-18 21:51:53 +02:00
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name, type, dnsClass, timeToLive, in.retainedDuplicate().setIndex(offset, offset + length));
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2015-03-16 07:46:14 +01:00
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}
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/**
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* Retrieves a domain name given a buffer containing a DNS packet. If the
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* name contains a pointer, the position of the buffer will be set to
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* directly after the pointer's index after the name has been read.
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*
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* @param in the byte buffer containing the DNS packet
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* @return the domain name for an entry
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*/
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2016-06-13 21:16:22 +02:00
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protected String decodeName0(ByteBuf in) {
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return decodeName(in);
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}
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/**
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* Retrieves a domain name given a buffer containing a DNS packet. If the
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* name contains a pointer, the position of the buffer will be set to
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* directly after the pointer's index after the name has been read.
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*
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* @param in the byte buffer containing the DNS packet
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* @return the domain name for an entry
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*/
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public static String decodeName(ByteBuf in) {
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2019-07-02 19:38:51 +02:00
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return DnsCodecUtil.decodeDomainName(in);
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2015-03-16 07:46:14 +01:00
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}
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}
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