encodeOptEcsRecord() — netty Function Reference

Source Code

codec-dns/src/main/java/io/netty/handler/codec/dns/DefaultDnsRecordEncoder.java lines 85–128

    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
                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);
        }
    }