/*
* Copyright 2015 The Netty Project
*
* The Netty Project licenses this file to you under the Apache License,
* version 2.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
package io.netty.handler.codec.dns;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufUtil;
import io.netty.channel.socket.InternetProtocolFamily;
import io.netty.handler.codec.UnsupportedMessageTypeException;
import io.netty.util.internal.StringUtil;
import io.netty.util.internal.UnstableApi;
import static io.netty.handler.codec.dns.DefaultDnsRecordDecoder.ROOT;
/**
* The default {@link DnsRecordEncoder} implementation.
*
* @see DefaultDnsRecordDecoder
*/
@UnstableApi
public class DefaultDnsRecordEncoder implements DnsRecordEncoder {
private static final int PREFIX_MASK = Byte.SIZE - 1;
/**
* Creates a new instance.
*/
protected DefaultDnsRecordEncoder() { }
@Override
public final void encodeQuestion(DnsQuestion question, ByteBuf out) throws Exception {
encodeName(question.name(), out);
out.writeShort(question.type().intValue());
out.writeShort(question.dnsClass());
}
@Override
public void encodeRecord(DnsRecord record, ByteBuf out) throws Exception {
if (record instanceof DnsQuestion) {
encodeQuestion((DnsQuestion) record, out);
} else if (record instanceof DnsPtrRecord) {
encodePtrRecord((DnsPtrRecord) record, out);
} else if (record instanceof DnsOptEcsRecord) {
encodeOptEcsRecord((DnsOptEcsRecord) record, out);
} else if (record instanceof DnsOptPseudoRecord) {
encodeOptPseudoRecord((DnsOptPseudoRecord) record, out);
} else if (record instanceof DnsRawRecord) {
encodeRawRecord((DnsRawRecord) record, out);
} else {
throw new UnsupportedMessageTypeException(StringUtil.simpleClassName(record));
}
}
private void encodeRecord0(DnsRecord record, ByteBuf out) throws Exception {
encodeName(record.name(), out);
out.writeShort(record.type().intValue());
out.writeShort(record.dnsClass());
out.writeInt((int) record.timeToLive());
}
private void encodePtrRecord(DnsPtrRecord record, ByteBuf out) throws Exception {
encodeRecord0(record, out);
encodeName(record.hostname(), out);
}
private void encodeOptPseudoRecord(DnsOptPseudoRecord record, ByteBuf out) throws Exception {
encodeRecord0(record, out);
out.writeShort(0);
}
private void encodeOptEcsRecord(DnsOptEcsRecord record, ByteBuf out) throws Exception {
encodeRecord0(record, out);
int sourcePrefixLength = record.sourcePrefixLength();
int scopePrefixLength = record.scopePrefixLength();
int lowOrderBitsToPreserve = sourcePrefixLength & PREFIX_MASK;
byte[] bytes = record.address();
int addressBits = bytes.length << 3;
if (addressBits < sourcePrefixLength || sourcePrefixLength < 0) {
throw new IllegalArgumentException(sourcePrefixLength + ": " +
sourcePrefixLength + " (expected: 0 >= " + addressBits + ')');
}
// See http://www.iana.org/assignments/address-family-numbers/address-family-numbers.xhtml
final short addressNumber = (short) (bytes.length == 4 ?
InternetProtocolFamily.IPv4.addressNumber() : InternetProtocolFamily.IPv6.addressNumber());
int payloadLength = calculateEcsAddressLength(sourcePrefixLength, lowOrderBitsToPreserve);
int fullPayloadLength = 2 + // OPTION-CODE
2 + // OPTION-LENGTH
2 + // FAMILY
1 + // SOURCE PREFIX-LENGTH
1 + // SCOPE PREFIX-LENGTH
payloadLength; // ADDRESS...
out.writeShort(fullPayloadLength);
out.writeShort(8); // This is the defined type for ECS.
out.writeShort(fullPayloadLength - 4); // Not include OPTION-CODE and OPTION-LENGTH
out.writeShort(addressNumber);
out.writeByte(sourcePrefixLength);
out.writeByte(scopePrefixLength); // Must be 0 in queries.
if (lowOrderBitsToPreserve > 0) {
int bytesLength = payloadLength - 1;
out.writeBytes(bytes, 0, bytesLength);
// Pad the leftover of the last byte with zeros.
out.writeByte(padWithZeros(bytes[bytesLength], lowOrderBitsToPreserve));
} else {
// The sourcePrefixLength align with Byte so just copy in the bytes directly.
out.writeBytes(bytes, 0, payloadLength);
}
}
// Package-Private for testing
static int calculateEcsAddressLength(int sourcePrefixLength, int lowOrderBitsToPreserve) {
return (sourcePrefixLength >>> 3) + (lowOrderBitsToPreserve != 0 ? 1 : 0);
}
private void encodeRawRecord(DnsRawRecord record, ByteBuf out) throws Exception {
encodeRecord0(record, out);
ByteBuf content = record.content();
int contentLen = content.readableBytes();
out.writeShort(contentLen);
out.writeBytes(content, content.readerIndex(), contentLen);
}
protected void encodeName(String name, ByteBuf buf) throws Exception {
if (ROOT.equals(name)) {
// Root domain
buf.writeByte(0);
return;
}
final String[] labels = name.split("\\.");
for (String label : labels) {
final int labelLen = label.length();
if (labelLen == 0) {
// zero-length label means the end of the name.
break;
}
buf.writeByte(labelLen);
ByteBufUtil.writeAscii(buf, label);
}
buf.writeByte(0); // marks end of name field
}
// Package private so it can be reused in the test.
static byte padWithZeros(byte b, int lowOrderBitsToPreserve) {
switch (lowOrderBitsToPreserve) {
case 0:
return 0;
case 1:
return (byte) (0x01 & b);
case 2:
return (byte) (0x03 & b);
case 3:
return (byte) (0x07 & b);
case 4:
return (byte) (0x0F & b);
case 5:
return (byte) (0x1F & b);
case 6:
return (byte) (0x3F & b);
case 7:
return (byte) (0x7F & b);
case 8:
return b;
default:
throw new IllegalArgumentException("lowOrderBitsToPreserve: " + lowOrderBitsToPreserve);
}
}
}