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xism4 wants to merge 5 commits into from
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Use Velocity VarIntFrameDecoder #783

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5b3ddf0
Use Velocity VarIntFrameDecoder
xism4 Nov 17, 2022
b9b8309
Replace GPL license with same as 0056 patch.
xism4 Nov 21, 2022
6f7929a
Remove unused objects due trace-less catch
xism4 Nov 22, 2022
532158a
Re-implement TOO_BIG result
xism4 Nov 22, 2022
2fbb6b4
Merge branch 'PaperMC:master' into master
xism4 Dec 13, 2022
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188 changes: 188 additions & 0 deletions BungeeCord-Patches/0066-Use-Velocity-VarintFrameDecoder.patch
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Original file line number Diff line number Diff line change
@@ -0,0 +1,188 @@
From dcbe861c2c63b09edc88ca7f3e42d9f9687f63af Mon Sep 17 00:00:00 2001
From: xIsm4 <minelatinsoporte@gmail.com>
Date: Thu, 17 Nov 2022 10:52:42 +0100
Subject: [PATCH] Use Velocity VarintFrameDecoder


diff --git a/protocol/src/main/java/net/md_5/bungee/protocol/Varint21FrameDecoder.java b/protocol/src/main/java/net/md_5/bungee/protocol/Varint21FrameDecoder.java
index c0d37142..bdeab0dc 100644
--- a/protocol/src/main/java/net/md_5/bungee/protocol/Varint21FrameDecoder.java
+++ b/protocol/src/main/java/net/md_5/bungee/protocol/Varint21FrameDecoder.java
@@ -1,65 +1,78 @@
+/*
+ * Courtesy of Velocity
+ * See https://github.com/VelocityPowered/Velocity/commit/5ceac16a821ea35572ff11412ace8929fd06e278
+ */
+
package net.md_5.bungee.protocol;

+import net.md_5.bungee.protocol.VarintByteDecoder.DecodeResult;
import io.netty.buffer.ByteBuf;
-import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
-import io.netty.handler.codec.CorruptedFrameException;
+
import java.util.List;

-public class Varint21FrameDecoder extends ByteToMessageDecoder
-{
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+public class Varint21FrameDecoder extends ByteToMessageDecoder {

- private static boolean DIRECT_WARNING;
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@Janmm14 Janmm14 Dec 8, 2022

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The patch 0044-Don-t-use-a-bytebuf-for-packet-decoding.patch should be edited if you want to remove this line.

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@xism4 xism4 Dec 15, 2022

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Got it

+ private static final FastDecoderException BAD_LENGTH_CACHED =
+ new FastDecoderException("Bad packet length");
+ private static final FastDecoderException VARINT_BIG_CACHED =
+ new FastDecoderException("VarInt too big");

@Override
- protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception
- {
- // If we decode an invalid packet and an exception is thrown (thus triggering a close of the connection),
- // the Netty ByteToMessageDecoder will continue to frame more packets and potentially call fireChannelRead()
- // on them, likely with more invalid packets. Therefore, check if the connection is no longer active and if so
- // sliently discard the packet.
- if ( !ctx.channel().isActive() )
- {
- in.skipBytes( in.readableBytes() );
+ protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) {
+ if (!ctx.channel().isActive()) {
+ in.clear();
return;
}

- in.markReaderIndex();
+ final VarintByteDecoder reader = new VarintByteDecoder();
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- for ( int i = 0; i < 3; i++ ) // Waterfall
- {
- if ( !in.isReadable() )
- {
- in.resetReaderIndex();
- return;
+ int varintEnd = in.forEachByte(reader);
+ if (varintEnd == -1) {
+ // We tried to go beyond the end of the buffer. This is probably a good sign that the
+ // buffer was too short to hold a proper varint.
+ if (reader.getResult() == DecodeResult.RUN_OF_ZEROES) {
+ // Special case where the entire packet is just a run of zeroes. We ignore them all.
+ in.clear();
}
+ return;
+ }

- // Waterfall start
- byte read = in.readByte();
- if ( read >= 0 )
- {
- in.resetReaderIndex();
- int length = DefinedPacket.readVarInt( in );
- // Waterfall end
- if ( false && length == 0) // Waterfall - ignore
- {
- throw new CorruptedFrameException( "Empty Packet!" );
- }
-
- if ( in.readableBytes() < length )
- {
- in.resetReaderIndex();
- return;
- // Waterfall start
- } else {
- out.add(in.readRetainedSlice(length));
- return;
- // Waterfall end
+ if (reader.getResult() == DecodeResult.RUN_OF_ZEROES) {
+ // this will return to the point where the next varint starts
+ in.readerIndex(varintEnd);
+ } else if (reader.getResult() == DecodeResult.SUCCESS) {
+ int readVarint = reader.getReadVarint();
+ int bytesRead = reader.getBytesRead();
+ if (readVarint < 0) {
+ in.clear();
+ throw BAD_LENGTH_CACHED;
+ } else if (readVarint == 0) {
+ // skip over the empty packet(s) and ignore it
+ in.readerIndex(varintEnd + 1);
+ } else {
+ int minimumRead = bytesRead + readVarint;
+ if (in.isReadable(minimumRead)) {
+ out.add(in.retainedSlice(varintEnd + 1, readVarint));
+ in.skipBytes(minimumRead);
}
}
+ } else if (reader.getResult() == DecodeResult.TOO_BIG) {
+ in.clear();
+ throw VARINT_BIG_CACHED;
}
-
- throw new CorruptedFrameException( "length wider than 21-bit" );
}
-}
+}
\ No newline at end of file
diff --git a/protocol/src/main/java/net/md_5/bungee/protocol/VarintByteDecoder.java b/protocol/src/main/java/net/md_5/bungee/protocol/VarintByteDecoder.java
new file mode 100644
index 00000000..2e4ccf05
--- /dev/null
+++ b/protocol/src/main/java/net/md_5/bungee/protocol/VarintByteDecoder.java
@@ -0,0 +1,68 @@
+/*
+ * Courtesy of Velocity
+ * See https://github.com/VelocityPowered/Velocity/commit/5ceac16a821ea35572ff11412ace8929fd06e278
+ */
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+
+package net.md_5.bungee.protocol;
+
+import io.netty.util.ByteProcessor;
+
+class VarintByteDecoder implements ByteProcessor {
+
+ private int readVarint;
+ private int bytesRead;
+ private DecodeResult result = DecodeResult.TOO_SHORT;
+
+ @Override
+ public boolean process(byte k) {
+ if (k == 0 && bytesRead == 0) {
+ // tentatively say it's invalid, but there's a possibility of redemption
+ result = DecodeResult.RUN_OF_ZEROES;
+ return true;
+ }
+ if (result == DecodeResult.RUN_OF_ZEROES) {
+ return false;
+ }
+ readVarint |= (k & 0x7F) << bytesRead++ * 7;
+ if (bytesRead > 3) {
+ result = DecodeResult.TOO_BIG;
+ return false;
+ }
+ if ((k & 0x80) != 128) {
+ result = DecodeResult.SUCCESS;
+ return false;
+ }
+ return true;
+ }
+
+ public int getReadVarint() {
+ return readVarint;
+ }
+
+ public int getBytesRead() {
+ return bytesRead;
+ }
+
+ public DecodeResult getResult() {
+ return result;
+ }
+
+ public enum DecodeResult {
+ SUCCESS,
+ TOO_BIG,
+ RUN_OF_ZEROES,
+ }
+}
\ No newline at end of file
--
2.38.1.windows.1