DefaultDnsRecordEncoder Class — netty Architecture

Source Code

codec-dns/src/main/java/io/netty/handler/codec/dns/DefaultDnsRecordEncoder.java lines 26–173

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());
    }

    private static final Class<?>[] SUPPORTED_MESSAGES = new Class<?>[] {
            DnsQuestion.class, DnsPtrRecord.class,
            DnsOptEcsRecord.class, DnsOptPseudoRecord.class, DnsRawRecord.class };

    @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(record, SUPPORTED_MESSAGES);
        }
    }

    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);
        int writerIndex = out.writerIndex();
        // Skip 2 bytes as these will be used to encode the rdataLen after we know how many bytes were written.
        // See https://www.rfc-editor.org/rfc/rfc1035.html#section-3.2.1
        out.writerIndex(writerIndex + 2);
        encodeName(record.hostname(), out);
        int rdLength = out.writerIndex() - (writerIndex + 2);
        out.setShort(writerIndex, rdLength);
    }

    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 https://www.iana.org/assignments/address-family-numbers/address-family-numbers.xhtml
        final short addressNumber = (short) (bytes.length == 4 ? 1 : 2);
        int payloadLength = calculateEcsAddressLength(sourcePrefixLength, lowOrderBitsToPreserve);

        int fullPayloadLength = 2 + // OPTION-CODE
                2 + // OPTION-LENGTH
                2 + // FAMILY
                1 + // SOURCE PREFIX-LENGTH