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[#5391] DnsNameResolver does not resolve property A+CNAME answer

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Motivation:

The current DnsNameResolver fails to resolve an A+CNAME answer. For example:

dig moose.rmq.cloudamqp.com

...
;; ANSWER SECTION:
moose.rmq.cloudamqp.com. 1800   IN  CNAME   ec2-54-152-221-139.compute-1.amazonaws.com.
ec2-54-152-221-139.compute-1.amazonaws.com. 583612 IN A 54.152.221.139
...

The resolver constructs a map of cnames but forgets the trailing "." in the values which lead to not resolve the A record.

Modifications:

Reuse the code of DefaltDnsRecordDecoder which correctly handles the trailing dot.

Result:

Correctly resolve.
This commit is contained in:
Norman Maurer 2016-06-13 21:16:22 +02:00
parent aa8f7b395b
commit c7a0a0f325
2 changed files with 22 additions and 48 deletions
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16
codec-dns/src/main/java/io/netty/handler/codec/dns/DefaultDnsRecordDecoder.java
View File

@ -92,7 +92,7 @@ public class DefaultDnsRecordDecoder implements DnsRecordDecoder {
if (type == DnsRecordType.PTR) {
in.setIndex(offset, offset + length);
return new DefaultDnsPtrRecord(name, dnsClass, timeToLive, decodeName(in));
return new DefaultDnsPtrRecord(name, dnsClass, timeToLive, decodeName0(in));
}
return new DefaultDnsRawRecord(
name, type, dnsClass, timeToLive, in.retainedDuplicate().setIndex(offset, offset + length));
@ -106,7 +106,19 @@ public class DefaultDnsRecordDecoder implements DnsRecordDecoder {
* @param in the byte buffer containing the DNS packet
* @return the domain name for an entry
*/
protected String decodeName(ByteBuf in) {
protected String decodeName0(ByteBuf in) {
return decodeName(in);
}
/**
* Retrieves a domain name given a buffer containing a DNS packet. If the
* name contains a pointer, the position of the buffer will be set to
* directly after the pointer's index after the name has been read.
*
* @param in the byte buffer containing the DNS packet
* @return the domain name for an entry
*/
public static String decodeName(ByteBuf in) {
int position = -1;
int checked = 0;
final int end = in.writerIndex();

54
resolver-dns/src/main/java/io/netty/resolver/dns/DnsNameResolverContext.java
View File

@ -20,6 +20,7 @@ import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufHolder;
import io.netty.channel.AddressedEnvelope;
import io.netty.channel.socket.InternetProtocolFamily;
import io.netty.handler.codec.CorruptedFrameException;
import io.netty.handler.codec.dns.DefaultDnsQuestion;
import io.netty.handler.codec.dns.DefaultDnsRecordDecoder;
import io.netty.handler.codec.dns.DnsResponseCode;
@ -29,7 +30,6 @@ import io.netty.handler.codec.dns.DnsRawRecord;
import io.netty.handler.codec.dns.DnsRecord;
import io.netty.handler.codec.dns.DnsRecordType;
import io.netty.handler.codec.dns.DnsResponse;
import io.netty.util.CharsetUtil;
import io.netty.util.ReferenceCountUtil;
import io.netty.util.concurrent.Future;
import io.netty.util.concurrent.FutureListener;
@ -438,53 +438,15 @@ abstract class DnsNameResolverContext<T> {
protected abstract boolean finishResolve(
Class<? extends InetAddress> addressType, List<DnsCacheEntry> resolvedEntries);
/**
* Adapted from {@link DefaultDnsRecordDecoder#decodeName(ByteBuf)}.
*/
static String decodeDomainName(ByteBuf buf) {
buf.markReaderIndex();
static String decodeDomainName(ByteBuf in) {
in.markReaderIndex();
try {
int position = -1;
int checked = 0;
final int end = buf.writerIndex();
final StringBuilder name = new StringBuilder(buf.readableBytes() << 1);
for (int len = buf.readUnsignedByte(); buf.isReadable() && len != 0; len = buf.readUnsignedByte()) {
boolean pointer = (len & 0xc0) == 0xc0;
if (pointer) {
if (position == -1) {
position = buf.readerIndex() + 1;
}
final int next = (len & 0x3f) << 8 | buf.readUnsignedByte();
if (next >= end) {
// Should not happen.
return null;
}
buf.readerIndex(next);
// check for loops
checked += 2;
if (checked >= end) {
// Name contains a loop; give up.
return null;
}
} else {
name.append(buf.toString(buf.readerIndex(), len, CharsetUtil.UTF_8)).append('.');
buf.skipBytes(len);
}
}
if (position != -1) {
buf.readerIndex(position);
}
if (name.length() == 0) {
return null;
}
return name.substring(0, name.length() - 1);
return DefaultDnsRecordDecoder.decodeName(in);
} catch (CorruptedFrameException e) {
// In this case we just return null.
return null;
} finally {
buf.resetReaderIndex();
in.resetReaderIndex();
}
}