More protocol sanity.

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/ServerConnection.java

@@ -93,11 +93,13 @@ public class ServerConnection implements MinecraftConnectionAssociation {
     }
 
     private void startHandshake() {
+        PlayerInfoForwarding forwardingMode =  VelocityServer.getServer().getConfiguration().getPlayerInfoForwardingMode();
+
         // Initiate a handshake.
         Handshake handshake = new Handshake();
         handshake.setNextStatus(StateRegistry.LOGIN_ID);
         handshake.setProtocolVersion(proxyPlayer.getConnection().getProtocolVersion());
-        if (VelocityServer.getServer().getConfiguration().getPlayerInfoForwardingMode() == PlayerInfoForwarding.LEGACY) {
+        if (forwardingMode == PlayerInfoForwarding.LEGACY) {
             handshake.setServerAddress(createBungeeForwardingAddress());
         } else {
             handshake.setServerAddress(serverInfo.getAddress().getHostString());
@@ -110,8 +112,7 @@ public class ServerConnection implements MinecraftConnectionAssociation {
         minecraftConnection.setState(StateRegistry.LOGIN);
 
         // Send the server login packet for <=1.12.2 and for 1.13+ servers not using "modern" forwarding.
-        if (protocolVersion <= ProtocolConstants.MINECRAFT_1_12_2 ||
+        if (protocolVersion <= ProtocolConstants.MINECRAFT_1_12_2 || forwardingMode != PlayerInfoForwarding.MODERN) {
-                VelocityServer.getServer().getConfiguration().getPlayerInfoForwardingMode() != PlayerInfoForwarding.MODERN) {
             ServerLogin login = new ServerLogin();
             login.setUsername(proxyPlayer.getUsername());
             minecraftConnection.write(login);

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftDecoder.java

@@ -40,6 +40,10 @@ public class MinecraftDecoder extends MessageToMessageDecoder<ByteBuf> {
                 throw new CorruptedFrameException("Error decoding " + packet.getClass() + " Direction " + direction
                         + " Protocol " + protocolVersion + " State " + state + " ID " + Integer.toHexString(packetId), e);
             }
+            if (msg.isReadable()) {
+                throw new CorruptedFrameException("Did not read full packet for " + packet.getClass() + " Direction " + direction
+                        + " Protocol " + protocolVersion + " State " + state + " ID " + Integer.toHexString(packetId));
+            }
             out.add(packet);
         }
     }