static String decodeDomainName(ByteBuf in) {
    in.markReaderIndex();
    try {
        return DefaultDnsRecordDecoder.decodeName(in);
    } catch (CorruptedFrameException e) {
        // In this case we just return null.
        return null;
    } finally {
        in.resetReaderIndex();
    }
}
 

List<TransportAddress> parseRecords(List<DnsRecord> records) {
    List<TransportAddress> addresses = new ArrayList<>(records.size());
    for (DnsRecord record : records) {
        if (record instanceof DefaultDnsRawRecord) {
            DefaultDnsRawRecord rawRecord = (DefaultDnsRawRecord) record;
            ByteBuf content = rawRecord.content();
            // first is "priority", we don't use it
            content.readUnsignedShort();
            // second is "weight", we don't use it
            content.readUnsignedShort();
            int port = content.readUnsignedShort();
            String hostname = DefaultDnsRecordDecoder.decodeName(content).replaceFirst("\\.$", "");
            String address = hostname + ":" + port;
            try {
                for (TransportAddress transportAddress : transportService.addressesFromString(address)) {
                    if (LOGGER.isTraceEnabled()) {
                        LOGGER.trace("adding {}, transport_address {}", address, transportAddress);
                    }
                    addresses.add(transportAddress);
                }
            } catch (Exception e) {
                LOGGER.warn("failed to add " + address, e);
            }
        }
    }
    return addresses;
}
 

@Override
ImmutableSortedSet<Endpoint> onDnsRecords(List<DnsRecord> records, int ttl) throws Exception {
    final ImmutableSortedSet.Builder<Endpoint> builder = ImmutableSortedSet.naturalOrder();
    for (DnsRecord r : records) {
        if (!(r instanceof DnsRawRecord) || r.type() != DnsRecordType.SRV) {
            continue;
        }

        final ByteBuf content = ((ByteBufHolder) r).content();
        if (content.readableBytes() <= 6) { // Too few bytes
            warnInvalidRecord(DnsRecordType.SRV, content);
            continue;
        }

        content.markReaderIndex();
        content.skipBytes(2);  // priority unused
        final int weight = content.readUnsignedShort();
        final int port = content.readUnsignedShort();

        final Endpoint endpoint;
        try {
            final String target = stripTrailingDot(DefaultDnsRecordDecoder.decodeName(content));
            endpoint = port > 0 ? Endpoint.of(target, port) : Endpoint.of(target);
        } catch (Exception e) {
            content.resetReaderIndex();
            warnInvalidRecord(DnsRecordType.SRV, content);
            continue;
        }

        builder.add(endpoint.withWeight(weight));
    }

    final ImmutableSortedSet<Endpoint> endpoints = builder.build();
    if (logger().isDebugEnabled()) {
        logger().debug("{} Resolved: {} (TTL: {})",
                       logPrefix(),
                       endpoints.stream()
                                .map(e -> e.authority() + '/' + e.weight())
                                .collect(Collectors.joining(", ")),
                       ttl);
    }

    return endpoints;
}
 

private void resolveAddress() {
    boolean debug = getFlag(BuiltinFlags.PRINT_DEBUG, false);

    String name = this.getPacketProtocol().getSRVRecordPrefix() + "._tcp." + this.getHost();
    if(debug) {
        System.out.println("[PacketLib] Attempting SRV lookup for \"" + name + "\".");
    }

    AddressedEnvelope<DnsResponse, InetSocketAddress> envelope = null;
    try(DnsNameResolver resolver = new DnsNameResolverBuilder(this.group.next())
            .channelType(NioDatagramChannel.class)
            .build()) {
        envelope = resolver.query(new DefaultDnsQuestion(name, DnsRecordType.SRV)).get();
        DnsResponse response = envelope.content();
        if(response.count(DnsSection.ANSWER) > 0) {
            DefaultDnsRawRecord record = response.recordAt(DnsSection.ANSWER, 0);
            if(record.type() == DnsRecordType.SRV) {
                ByteBuf buf = record.content();
                buf.skipBytes(4); // Skip priority and weight.

                int port = buf.readUnsignedShort();
                String host = DefaultDnsRecordDecoder.decodeName(buf);
                if(host.endsWith(".")) {
                    host = host.substring(0, host.length() - 1);
                }

                if(debug) {
                    System.out.println("[PacketLib] Found SRV record containing \"" + host + ":" + port + "\".");
                }

                this.host = host;
                this.port = port;
            } else if(debug) {
                System.out.println("[PacketLib] Received non-SRV record in response.");
            }
        } else if(debug) {
            System.out.println("[PacketLib] No SRV record found.");
        }
    } catch(Exception e) {
        if(debug) {
            System.out.println("[PacketLib] Failed to resolve SRV record.");
            e.printStackTrace();
        }
    } finally {
        if(envelope != null) {
            envelope.release();
        }
    }
}