SRV resolving / Small Handshake rework (#968)

Handshake now uses the server address directly from the config and no longer the IP from a domain (Some servers use the address that is given during the handshake)

bootstrap/sponge/src/main/java/org/geysermc/platform/sponge/GeyserSpongeConfiguration.java

@@ -195,11 +195,21 @@ public class GeyserSpongeConfiguration implements GeyserConfiguration {
             return node.getNode("address").getString("127.0.0.1");
         }
 
+        @Override
+        public void setAddress(String address) {
+            node.getNode("address").setValue(address);
+        }
+
         @Override
         public int getPort() {
             return node.getNode("port").getInt(25565);
         }
 
+        @Override
+        public void setPort(int port) {
+            node.getNode("port").setValue(port);
+        }
+
         @Override
         public String getAuthType() {
             return node.getNode("auth-type").getString("online");

connector/src/main/java/org/geysermc/connector/GeyserConnector.java

@@ -32,10 +32,10 @@ import com.nukkitx.protocol.bedrock.BedrockServer;
 import com.nukkitx.protocol.bedrock.v407.Bedrock_v407;
 import lombok.Getter;
 import lombok.Setter;
-import org.geysermc.connector.common.AuthType;
-import org.geysermc.connector.common.PlatformType;
 import org.geysermc.connector.bootstrap.GeyserBootstrap;
 import org.geysermc.connector.command.CommandManager;
+import org.geysermc.connector.common.AuthType;
+import org.geysermc.connector.common.PlatformType;
 import org.geysermc.connector.configuration.GeyserConfiguration;
 import org.geysermc.connector.metrics.Metrics;
 import org.geysermc.connector.network.ConnectorServerEventHandler;
@@ -51,17 +51,19 @@ import org.geysermc.connector.network.translators.item.PotionMixRegistry;
 import org.geysermc.connector.network.translators.sound.SoundHandlerRegistry;
 import org.geysermc.connector.network.translators.sound.SoundRegistry;
 import org.geysermc.connector.network.translators.world.WorldManager;
-import org.geysermc.connector.utils.LanguageUtils;
 import org.geysermc.connector.network.translators.world.block.BlockTranslator;
 import org.geysermc.connector.network.translators.world.block.entity.BlockEntityTranslator;
 import org.geysermc.connector.utils.DimensionUtils;
 import org.geysermc.connector.utils.DockerCheck;
+import org.geysermc.connector.utils.LanguageUtils;
 import org.geysermc.connector.utils.LocaleUtils;
 
+import javax.naming.NamingException;
+import javax.naming.directory.Attribute;
+import javax.naming.directory.InitialDirContext;
 import java.net.InetSocketAddress;
 import java.text.DecimalFormat;
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.Executors;
@@ -78,6 +80,8 @@ public class GeyserConnector {
     public static final String NAME = "Geyser";
     public static final String VERSION = "DEV"; // A fallback for running in IDEs
 
+    private static final String IP_REGEX = "\\b\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\b";
+
     private final List<GeyserSession> players = new ArrayList<>();
 
     private static GeyserConnector instance;
@@ -136,8 +140,28 @@ public class GeyserConnector {
         if (platformType != PlatformType.STANDALONE) {
             DockerCheck.check(bootstrap);
         }
+        String remoteAddress = config.getRemote().getAddress();
+        int remotePort = config.getRemote().getPort();
+        // Filters whether it is not an IP address or localhost, because otherwise it is not possible to find out an SRV entry.
+        if ((config.isLegacyPingPassthrough() || platformType == PlatformType.STANDALONE) && !remoteAddress.matches(IP_REGEX) && !remoteAddress.equalsIgnoreCase("localhost")) {
+            try {
+                // Searches for a server address and a port from a SRV record of the specified host name
+                InitialDirContext ctx = new InitialDirContext();
+                Attribute attr = ctx.getAttributes("dns:///_minecraft._tcp." + remoteAddress, new String[]{"SRV"}).get("SRV");
+                // size > 0 = SRV entry found
+                if (attr.size() > 0) {
+                    String[] record = ((String) attr.get(0)).split(" ");
+                    // Overwrites the existing address and port with that from the SRV record.
+                    config.getRemote().setAddress(remoteAddress = record[3]);
+                    config.getRemote().setPort(remotePort = Integer.parseInt(record[2]));
+                    logger.debug("Found SRV record \"" + remoteAddress + ":" + remotePort + "\"");
+                }
+            } catch (NamingException ex) {
+                ex.printStackTrace();
+            }
+        }
 
-        remoteServer = new RemoteServer(config.getRemote().getAddress(), config.getRemote().getPort());
+        remoteServer = new RemoteServer(config.getRemote().getAddress(), remotePort);
         authType = AuthType.getByName(config.getRemote().getAuthType());
 
         if (config.isAboveBedrockNetherBuilding())

connector/src/main/java/org/geysermc/connector/configuration/GeyserConfiguration.java

@@ -92,6 +92,10 @@ public interface GeyserConfiguration {
         String getAddress();
 
         int getPort();
+        
+        void setAddress(String address);
+
+        void setPort(int port);
 
         String getAuthType();
     }

connector/src/main/java/org/geysermc/connector/ping/GeyserLegacyPingPassthrough.java

@@ -79,15 +79,17 @@ public class GeyserLegacyPingPassthrough implements IGeyserPingPassthrough, Runn
     public void run() {
         try {
             Socket socket = new Socket();
-            socket.connect(new InetSocketAddress(connector.getConfig().getRemote().getAddress(), connector.getConfig().getRemote().getPort()), 5000);
+            String address = connector.getConfig().getRemote().getAddress();
+            int port = connector.getConfig().getRemote().getPort();
+            socket.connect(new InetSocketAddress(address, port), 5000);
 
             ByteArrayOutputStream byteArrayStream = new ByteArrayOutputStream();
             DataOutputStream handshake = new DataOutputStream(byteArrayStream);
             handshake.write(0x0);
             VarInts.writeUnsignedInt(handshake, MinecraftConstants.PROTOCOL_VERSION);
-            VarInts.writeUnsignedInt(handshake, socket.getInetAddress().getHostAddress().length());
+            VarInts.writeUnsignedInt(handshake, address.length());
-            handshake.writeBytes(socket.getInetAddress().getHostAddress());
+            handshake.writeBytes(address);
-            handshake.writeShort(socket.getPort());
+            handshake.writeShort(port);
             VarInts.writeUnsignedInt(handshake, 1);
 
             DataOutputStream dataOutputStream = new DataOutputStream(socket.getOutputStream());