SimpleDnsServer added

redisson/src/test/java/org/redisson/SimpleDnsServer.java

@@ -0,0 +1,67 @@
+package org.redisson;
+
+import io.netty.bootstrap.Bootstrap;
+import io.netty.buffer.Unpooled;
+import io.netty.channel.*;
+import io.netty.channel.nio.NioEventLoopGroup;
+import io.netty.channel.socket.nio.NioDatagramChannel;
+import io.netty.handler.codec.dns.*;
+
+import java.net.InetAddress;
+
+public class SimpleDnsServer {
+
+    EventLoopGroup group = new NioEventLoopGroup();
+    private Channel channel;
+    private String ip = "127.0.0.1";
+
+    public SimpleDnsServer() throws InterruptedException {
+            Bootstrap bootstrap = new Bootstrap();
+            bootstrap.group(group)
+                    .channel(NioDatagramChannel.class)
+                    .handler(new ChannelInitializer<>() {
+                        @Override
+                        protected void initChannel(Channel ch) throws Exception {
+                            ch.pipeline().addLast(new DatagramDnsQueryDecoder());
+                            ch.pipeline().addLast(new DatagramDnsResponseEncoder());
+                            ch.pipeline().addLast(new DnsMessageHandler());
+                        }
+                    });
+
+            ChannelFuture future = bootstrap.bind(55).sync(); // Bind to port 53 for DNS
+            channel = future.channel();
+    }
+
+    public void stop() {
+        channel.close();
+        group.shutdownGracefully();
+    }
+
+    public void updateIP(String ip) {
+        this.ip = ip;
+    }
+
+    private class DnsMessageHandler extends SimpleChannelInboundHandler<DatagramDnsQuery> {
+        @Override
+        protected void channelRead0(ChannelHandlerContext ctx, DatagramDnsQuery query) throws Exception {
+            DefaultDnsQuestion question = query.recordAt(DnsSection.QUESTION);
+            String requestedDomain = question.name();
+
+//            System.out.println("Received DNS query for: " + requestedDomain + " " + query);
+
+            // Create a response with a dummy IP address
+            DatagramDnsResponse response = new DatagramDnsResponse(query.recipient(), query.sender(), query.id());
+            response.addRecord(DnsSection.QUESTION, question);
+            response.addRecord(DnsSection.ANSWER, new DefaultDnsRawRecord(question.name(), DnsRecordType.A, 0,
+                    Unpooled.wrappedBuffer(InetAddress.getByName(ip).getAddress()))); // Example IP
+
+            ctx.writeAndFlush(response);
+        }
+
+        @Override
+        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
+            cause.printStackTrace();
+            ctx.close();
+        }
+    }
+}