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关于netty:Java-Netty框架自建DNS代理服务器教程

jiezi

前言

DNS 协定作为着互联网客户端 - 服务器通信模式得第一关，在当下每天都有成千上亿上网记录产生得当今社会，其重要性天然不可言喻。在国内比拟有名得 DNS 服务器有电信得 114.114.114.114、阿里云得 223.5.5.5，DNSPod 得 119.29.29.29，配置一个好的 DNS 服务器能够缩短申请响应工夫、升高 DNS 劫持概率，晋升上网体验。

下面这些都是互联网专用 DNS 服务器，本文博主教大家应用 Java Netty 自建 DNS 代理服务器，目前网上对于应用 Netty 自建 DNS 服务器得教程参差不齐，大多没有代理步骤，达不到博主想要得代理成果，因此创立此文。

一、自建 DNS 代理服务器有哪些劣势

  1. 域名管制：对于特定域名能够自在管制拜访权限（屏蔽对特定网站拜访）
  2. 域名记录：记录局域网内各个主机得域名拜访（记录员工上网记录）
  3. 配置内网域名：通过自建 DNS 服务器能够配置内网域名，节约老本
  4. DNS 负载平衡：通过自建 DNS 服务器能够轻松实现对于拜访域名得负载平衡配置
  5. …

二、自建 DNS 代理服务器代码

  1. 增加域名黑名单文件，resources 文件夹下增加 black_list.txt 文件 
google.com.
facebook.com.

初始化 BLACK_LIST_DOMAIN

private static final List<String> BLACK_LIST_DOMAIN = new ArrayList<>();
    static {
        String s;
        try (InputStream is = DnsServer.class.getClassLoader().getResourceAsStream("black_list.txt");
             BufferedReader br = new BufferedReader(new InputStreamReader(is))) {while (StrUtil.isNotBlank(s = br.readLine())) {BLACK_LIST_DOMAIN.add(s);
            }
        } catch (Exception e) {log.error(e.getMessage(), e);
        }
    }
  1. 应用 UDP 协定绑定本机 53 端口，并初始化 ProxyUdp DNS 申请代理对象 
@Slf4j
public final class DnsServer {private static final List<String> BLACK_LIST_DOMAIN = new ArrayList<>();
    static {...}

    public static void main(String[] args) throws Exception {ProxyUdp proxyUdp = new ProxyUdp();
        proxyUdp.init();
        final int[] num = {0};
        final NioEventLoopGroup group = new NioEventLoopGroup();
        Bootstrap bootstrap = new Bootstrap();
        bootstrap.group(group).channel(NioDatagramChannel.class)
                .handler(new ChannelInitializer<NioDatagramChannel>() {
                    @Override
                    protected void initChannel(NioDatagramChannel nioDatagramChannel) {nioDatagramChannel.pipeline().addLast(...);
                    }
                }).option(ChannelOption.SO_BROADCAST, true);

        int port = 53;
        ChannelFuture future = bootstrap.bind(port).addListener(future1 -> {log.info("server listening port:{}", port);
        });

        future.channel().closeFuture().addListener(future1 -> {if (future.isSuccess()) {log.info(future.channel().toString());
            }
        });
    }
}
  1. 给 nioDatagramChannel.pipeline() 增加 ChannelHandler
nioDatagramChannel.pipeline().addLast(new DatagramDnsQueryDecoder());
                        nioDatagramChannel.pipeline().addLast(new SimpleChannelInboundHandler<DatagramDnsQuery>() {
                            @Override
                            protected void channelRead0(ChannelHandlerContext ctx, DatagramDnsQuery msg) {
                                try {DefaultDnsQuestion dnsQuestion = msg.recordAt(DnsSection.QUESTION);
                                    String name = dnsQuestion.name();
                                    log.info(name + ++num[0]);
                                    Channel channel = ctx.channel();
                                    int id = msg.id();
                                    channel.attr(AttributeKey.<DatagramDnsQuery>valueOf(String.valueOf(id))).set(msg);
                                    if (BLACK_LIST_DOMAIN.contains(name)) {DnsQuestion question = msg.recordAt(DnsSection.QUESTION);
                                        DatagramDnsResponse dnsResponse = getDatagramDnsResponse(msg, id, question);
                                        channel.writeAndFlush(dnsResponse);
                                        return;
                                    }
                                    proxyUdp.send(name, msg.id(), channel);
                                } catch (Exception e) {log.error(e.getMessage(), e);
                                }
                            }

                            private DatagramDnsResponse getDatagramDnsResponse(DatagramDnsQuery msg, int id, DnsQuestion question) {DatagramDnsResponse dnsResponse = new DatagramDnsResponse(msg.recipient(), msg.sender(), id);
                                dnsResponse.addRecord(DnsSection.QUESTION, question);
                                DefaultDnsRawRecord queryAnswer = new DefaultDnsRawRecord(question.name(),
                                        DnsRecordType.A, 600, Unpooled.wrappedBuffer(new byte[]{(byte) 192, (byte) 168, 1, 1}));
                                dnsResponse.addRecord(DnsSection.ANSWER, queryAnswer);
                                return dnsResponse;
                            }

                            @Override
                            public void exceptionCaught(ChannelHandlerContext ctx, Throwable e) {log.error(e.getMessage(), e);
                            }
                        });
                        nioDatagramChannel.pipeline().addLast(new DatagramDnsResponseEncoder());

在 new SimpleChannelInboundHandler<DatagramDnsQuery>() 中 解析客户端 DNS 查问报文, 获取拜访域名信息，如果拜访域名在黑名单中，则通过 getDatagramDnsResponse() 间接返回 192.168.1.1 的 DNS 响应报文，反之则通过 proxyUdp 对象转发 DNS 查问。

  1. ProxyUdp 作为 DNS 查问代理类会通过 send(String domain, int id, Channel serverChannel) 办法传入 DnsServer 类收到的拜访域名、DNS 事务 ID、serverChannel。随后包装拜访域名申请 DNS 服务器 114.114.114.114，最初通过 new SimpleChannelInboundHandler<DatagramDnsResponse>() 将收到的 DNS 响应报文通过上一步传入得 serverChannel 输入到客户端。
@Slf4j
class ProxyUdp {
    private Channel serverChannel;
    private Channel proxyChannel;

    public void init() throws InterruptedException {EventLoopGroup proxyGroup = new NioEventLoopGroup();
        Bootstrap b = new Bootstrap();
        b.group(proxyGroup)
                .channel(NioDatagramChannel.class)
                .handler(new ChannelInitializer<DatagramChannel>() {
                    @Override
                    protected void initChannel(DatagramChannel ch) {ChannelPipeline p = ch.pipeline();
                        p.addLast(new DatagramDnsQueryEncoder())
                                .addLast(new DatagramDnsResponseDecoder())
                                .addLast(new SimpleChannelInboundHandler<DatagramDnsResponse>() {
                                    @Override
                                    public void channelActive(ChannelHandlerContext ctx) {log.info(ctx.channel().toString());
                                    }

                                    @Override
                                    protected void channelRead0(ChannelHandlerContext ctx, DatagramDnsResponse msg) {DatagramDnsQuery dnsQuery = localChannel.attr(AttributeKey.<DatagramDnsQuery>valueOf(String.valueOf(msg.id()))).get();
                                        DnsQuestion question = msg.recordAt(DnsSection.QUESTION);
                                        DatagramDnsResponse dnsResponse = new DatagramDnsResponse(dnsQuery.recipient(), dnsQuery.sender(), msg.id());
                                        dnsResponse.addRecord(DnsSection.QUESTION, question);

                                        for (int i = 0, count = msg.count(DnsSection.ANSWER); i < count; i++) {DnsRecord record = msg.recordAt(DnsSection.ANSWER, i);
                                            if (record.type() == DnsRecordType.A) {
                                                // just print the IP after query
                                                DnsRawRecord raw = (DnsRawRecord) record;
                                                DefaultDnsRawRecord queryAnswer = new DefaultDnsRawRecord(question.name(),
                                                        DnsRecordType.A, 600, Unpooled.wrappedBuffer(ByteBufUtil.getBytes(raw.content())));
                                                dnsResponse.addRecord(DnsSection.ANSWER, queryAnswer);
                                            }
                                        }

                                        serverChannel.writeAndFlush(dnsResponse);
                                    }

                                    @Override
                                    public void exceptionCaught(ChannelHandlerContext ctx, Throwable e) {log.error(e.getMessage(), e);
                                    }
                                });

                    }
                });
        proxyChannel = b.bind(0).sync().addListener(future1 -> {log.info("绑定胜利");
        }).channel();}

    public void send(String domain, int id, Channel serverChannel) {
        this.serverChannel = serverChannel;
        DnsQuery query = new DatagramDnsQuery(null, new InetSocketAddress("114.114.114.114", 53), id).setRecord(
                DnsSection.QUESTION,
                new DefaultDnsQuestion(domain, DnsRecordType.A));
        this.proxyChannel.writeAndFlush(query);
    }
}
  1. 自建 DNS 服务器全副代码 
@Slf4j
public final class DnsServer {private static final List<String> BLACK_LIST_DOMAIN = new ArrayList<>();
    static {
        String s;
        try (InputStream is = DnsServer.class.getClassLoader().getResourceAsStream("black_list.txt");
             BufferedReader br = new BufferedReader(new InputStreamReader(is))) {while (StrUtil.isNotBlank(s = br.readLine())) {BLACK_LIST_DOMAIN.add(s);
            }
        } catch (Exception e) {log.error(e.getMessage(), e);
        }
    }

    public static void main(String[] args) throws Exception {ProxyUdp proxyUdp = new ProxyUdp();
        proxyUdp.init();
        final int[] num = {0};
        final NioEventLoopGroup group = new NioEventLoopGroup();
        Bootstrap bootstrap = new Bootstrap();
        bootstrap.group(group).channel(NioDatagramChannel.class)
                .handler(new ChannelInitializer<NioDatagramChannel>() {
                    @Override
                    protected void initChannel(NioDatagramChannel nioDatagramChannel) {nioDatagramChannel.pipeline().addLast(new DatagramDnsQueryDecoder());
                        nioDatagramChannel.pipeline().addLast(new SimpleChannelInboundHandler<DatagramDnsQuery>() {

                            @Override
                            protected void channelRead0(ChannelHandlerContext ctx, DatagramDnsQuery msg) {
                                try {DefaultDnsQuestion dnsQuestion = msg.recordAt(DnsSection.QUESTION);
                                    String name = dnsQuestion.name();
                                    log.info(name + ++num[0]);
                                    Channel channel = ctx.channel();
                                    int id = msg.id();
                                    channel.attr(AttributeKey.<DatagramDnsQuery>valueOf(String.valueOf(id))).set(msg);
                                    if (BLACK_LIST_DOMAIN.contains(name)) {DnsQuestion question = msg.recordAt(DnsSection.QUESTION);
                                        DatagramDnsResponse dnsResponse = getDatagramDnsResponse(msg, id, question);
                                        channel.writeAndFlush(dnsResponse);
                                        return;
                                    }
                                    proxyUdp.send(name, msg.id(), channel);
                                } catch (Exception e) {log.error(e.getMessage(), e);
                                }
                            }

                            private DatagramDnsResponse getDatagramDnsResponse(DatagramDnsQuery msg, int id, DnsQuestion question) {DatagramDnsResponse dnsResponse = new DatagramDnsResponse(msg.recipient(), msg.sender(), id);
                                dnsResponse.addRecord(DnsSection.QUESTION, question);

                                // just print the IP after query
                                DefaultDnsRawRecord queryAnswer = new DefaultDnsRawRecord(question.name(),
                                        DnsRecordType.A, 600, Unpooled.wrappedBuffer(new byte[]{(byte) 192, (byte) 168, 1, 1}));
                                dnsResponse.addRecord(DnsSection.ANSWER, queryAnswer);
                                return dnsResponse;
                            }

                            @Override
                            public void exceptionCaught(ChannelHandlerContext ctx, Throwable e) {log.error(e.getMessage(), e);
                            }
                        });
                        nioDatagramChannel.pipeline().addLast(new DatagramDnsResponseEncoder());

                    }
                }).option(ChannelOption.SO_BROADCAST, true);

        int port = 553;
        ChannelFuture future = bootstrap.bind(port).addListener(future1 -> {log.info("server listening port:{}", port);
        });

        future.channel().closeFuture().addListener(future1 -> {if (future.isSuccess()) {log.info(future.channel().toString());
            }
        });
    }
}

@Slf4j
class ProxyUdp {
    private Channel localChannel;
    private Channel proxyChannel;

    public void init() throws InterruptedException {EventLoopGroup proxyGroup = new NioEventLoopGroup();
        Bootstrap b = new Bootstrap();
        b.group(proxyGroup)
                .channel(NioDatagramChannel.class)
                .handler(new ChannelInitializer<DatagramChannel>() {
                    @Override
                    protected void initChannel(DatagramChannel ch) {ChannelPipeline p = ch.pipeline();
                        p.addLast(new DatagramDnsQueryEncoder())
                                .addLast(new DatagramDnsResponseDecoder())
                                .addLast(new SimpleChannelInboundHandler<DatagramDnsResponse>() {
                                    @Override
                                    public void channelActive(ChannelHandlerContext ctx) {log.info(ctx.channel().toString());
                                    }

                                    @Override
                                    protected void channelRead0(ChannelHandlerContext ctx, DatagramDnsResponse msg) {DatagramDnsQuery dnsQuery = localChannel.attr(AttributeKey.<DatagramDnsQuery>valueOf(String.valueOf(msg.id()))).get();
                                        DnsQuestion question = msg.recordAt(DnsSection.QUESTION);
                                        DatagramDnsResponse dnsResponse = new DatagramDnsResponse(dnsQuery.recipient(), dnsQuery.sender(), msg.id());
                                        dnsResponse.addRecord(DnsSection.QUESTION, question);

                                        for (int i = 0, count = msg.count(DnsSection.ANSWER); i < count; i++) {DnsRecord record = msg.recordAt(DnsSection.ANSWER, i);
                                            if (record.type() == DnsRecordType.A) {
                                                // just print the IP after query
                                                DnsRawRecord raw = (DnsRawRecord) record;
                                                DefaultDnsRawRecord queryAnswer = new DefaultDnsRawRecord(question.name(),
                                                        DnsRecordType.A, 600, Unpooled.wrappedBuffer(ByteBufUtil.getBytes(raw.content())));
                                                dnsResponse.addRecord(DnsSection.ANSWER, queryAnswer);
                                            }
                                        }

                                        localChannel.writeAndFlush(dnsResponse);
                                    }

                                    @Override
                                    public void exceptionCaught(ChannelHandlerContext ctx, Throwable e) {log.error(e.getMessage(), e);
                                    }
                                });

                    }
                });
        proxyChannel = b.bind(0).sync().addListener(future1 -> {log.info("绑定胜利");
        }).channel();}

    public void send(String domain, int id, Channel localChannel) {
        this.localChannel = localChannel;
        DnsQuery query = new DatagramDnsQuery(null, new InetSocketAddress("114.114.114.114", 53), id).setRecord(
                DnsSection.QUESTION,
                new DefaultDnsQuestion(domain, DnsRecordType.A));
        this.proxyChannel.writeAndFlush(query);
    }
}

三、本地测试

  1. 批改本机 DNS 设置 (win11)，批改首选、备选 DNS 地址为 127.0.0.1
  1. 关上命令行工具，执行 DNS 缓存革除命令 ipconfig/flushdns

自此就能够关上浏览器拜访罕用网站，看是否能失常拜访，来验证自建的 DNS 服务器成果了

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