Fix packet interception error with ViaVersion (#724)

Thanks to @kennytv and @MedicOP for their help in tracking this bug down. Essentially the decode method we were using could be different depending on when the player logged in, which clashed with PL's static handling of it.

Fixes #724
Fixes #791
Fixes #803
Fixes #811
Fixes #813
Fixes #819
...and probably some others...

Author: dmulloy2

src/main/java/com/comphenix/protocol/injector/netty/ChannelInjector.java

@@ -79,23 +79,23 @@ public class ChannelInjector extends ByteToMessageDecoder implements Injector {
 	// Versioning
 	private static Class<?> PACKET_SET_PROTOCOL = null;
 
-	private static AtomicInteger keyId = new AtomicInteger();
-	private static AttributeKey<Integer> PROTOCOL_KEY;
+	private static final AtomicInteger keyId = new AtomicInteger();
+	private static final AttributeKey<Integer> PROTOCOL_KEY;
 
 	static {
 		PROTOCOL_KEY = AttributeKey.valueOf("PROTOCOL-" + keyId.getAndIncrement());
 	}
 
 	// Saved accessors
-	private static Method DECODE_BUFFER;
-	private static Method ENCODE_BUFFER;
+	private Method decodeBuffer;
+	private Method encodeBuffer;
 	private static FieldAccessor ENCODER_TYPE_MATCHER;
 
 	// For retrieving the protocol
 	private static FieldAccessor PROTOCOL_ACCESSOR;
 
 	// The factory that created this injector
-	private InjectionFactory factory;
+	private final InjectionFactory factory;
 
 	// The player, or temporary player
 	private Player player;
@@ -108,10 +108,10 @@ public class ChannelInjector extends ByteToMessageDecoder implements Injector {
 	// The current network manager and channel
 	private final Object networkManager;
 	private final Channel originalChannel;
-	private VolatileField channelField;
+	private final VolatileField channelField;
 
 	// Known network markers
-	private Map<Object, NetworkMarker> packetMarker = new WeakHashMap<>();
+	private final Map<Object, NetworkMarker> packetMarker = new WeakHashMap<>();
 
 	/**
 	 * Indicate that this packet has been processed by event listeners.
@@ -134,13 +134,13 @@ public class ChannelInjector extends ByteToMessageDecoder implements Injector {
 	private ByteToMessageDecoder vanillaDecoder;
 	private MessageToByteEncoder<Object> vanillaEncoder;
 
-	private Deque<PacketEvent> finishQueue = new ArrayDeque<>();
+	private final Deque<PacketEvent> finishQueue = new ArrayDeque<>();
 
 	// The channel listener
-	private ChannelListener channelListener;
+	private final ChannelListener channelListener;
 
 	// Processing network markers
-	private NetworkProcessor processor;
+	private final NetworkProcessor processor;
 
 	// Closed
 	private boolean injected;
@@ -178,6 +178,24 @@ public int getProtocolVersion() {
 		return value != null ? value : MinecraftProtocolVersion.getCurrentVersion();
 	}
 
+	private void updateBufferMethods() {
+		try {
+			decodeBuffer = vanillaDecoder.getClass().getDeclaredMethod("decode",
+					ChannelHandlerContext.class, ByteBuf.class, List.class);
+			decodeBuffer.setAccessible(true);
+		} catch (NoSuchMethodException ex) {
+			throw new IllegalArgumentException("Unable to find decode method in " + vanillaDecoder.getClass());
+		}
+
+		try {
+			encodeBuffer = vanillaEncoder.getClass().getDeclaredMethod("encode",
+					ChannelHandlerContext.class, Object.class, ByteBuf.class);
+			encodeBuffer.setAccessible(true);
+		} catch (NoSuchMethodException ex) {
+			throw new IllegalArgumentException("Unable to find encode method in " + vanillaEncoder.getClass());
+		}
+	}
+
 	@Override
 	@SuppressWarnings("unchecked")
 	public boolean inject() {
@@ -212,25 +230,7 @@ public boolean inject() {
 				throw new IllegalArgumentException("Unable to find vanilla encoder in " + originalChannel.pipeline());
 			patchEncoder(vanillaEncoder);
 
-			if (DECODE_BUFFER == null) {
-				try {
-					DECODE_BUFFER = vanillaDecoder.getClass().getDeclaredMethod("decode",
-							ChannelHandlerContext.class, ByteBuf.class, List.class);
-					DECODE_BUFFER.setAccessible(true);
-				} catch (NoSuchMethodException ex) {
-					throw new IllegalArgumentException("Unable to find decode method in " + vanillaDecoder.getClass());
-				}
-			}
-
-			if (ENCODE_BUFFER == null) {
-				try {
-					ENCODE_BUFFER = vanillaEncoder.getClass().getDeclaredMethod("encode",
-							ChannelHandlerContext.class, Object.class, ByteBuf.class);
-					ENCODE_BUFFER.setAccessible(true);
-				} catch (NoSuchMethodException ex) {
-					throw new IllegalArgumentException("Unable to find encode method in " + vanillaEncoder.getClass());
-				}
-			}
+			updateBufferMethods();
 
 			// Intercept sent packets
 			MessageToByteEncoder<Object> protocolEncoder = new MessageToByteEncoder<Object>() {
@@ -447,7 +447,7 @@ private void encode(ChannelHandlerContext ctx, Object packet, ByteBuf output) th
 			// Process output handler
 			if (packet != null && event != null && NetworkMarker.hasOutputHandlers(marker)) {
 				ByteBuf packetBuffer = ctx.alloc().buffer();
-				ENCODE_BUFFER.invoke(vanillaEncoder, ctx, packet, packetBuffer);
+				encodeBuffer.invoke(vanillaEncoder, ctx, packet, packetBuffer);
 
 				// Let each handler prepare the actual output
 				byte[] data = processor.processOutput(event, marker, getBytes(packetBuffer));
@@ -470,7 +470,7 @@ private void encode(ChannelHandlerContext ctx, Object packet, ByteBuf output) th
 			// Attempt to handle the packet nevertheless
 			if (packet != null) {
 				try {
-					ENCODE_BUFFER.invoke(vanillaEncoder, ctx, packet, output);
+					encodeBuffer.invoke(vanillaEncoder, ctx, packet, output);
 				} catch (InvocationTargetException ex) {
 					if (ex.getCause() instanceof Exception) {
 						//noinspection ThrowFromFinallyBlock
@@ -510,7 +510,12 @@ private void scheduleMainThread(final Object packetCopy) {
 	@Override
 	protected void decode(ChannelHandlerContext ctx, ByteBuf byteBuffer, List<Object> packets) throws Exception {
 		try {
-			DECODE_BUFFER.invoke(vanillaDecoder, ctx, byteBuffer, packets);
+			try {
+				decodeBuffer.invoke(vanillaDecoder, ctx, byteBuffer, packets);
+			} catch (IllegalArgumentException ex) {
+				updateBufferMethods();
+				decodeBuffer.invoke(vanillaDecoder, ctx, byteBuffer, packets);
+			}
 
 			// Reset queue
 			finishQueue.clear();