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Add system property for packet direction validation #1761

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pop4959 wants to merge 2 commits into from
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Add system property for packet direction validation #1761

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6cce036
add system property for packet direction validation
pop4959 Mar 31, 2026
df86ad5
use velocityproperties and default true
pop4959 Apr 1, 2026
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4 changes: 3 additions & 1 deletion proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftDecoder.java
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@
import com.velocitypowered.proxy.protocol.MinecraftPacket;
import com.velocitypowered.proxy.protocol.ProtocolUtils;
import com.velocitypowered.proxy.protocol.StateRegistry;
import com.velocitypowered.proxy.util.VelocityProperties;
import com.velocitypowered.proxy.util.except.QuietRuntimeException;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
Expand All @@ -37,6 +38,7 @@ public class MinecraftDecoder extends ChannelInboundHandlerAdapter {
private static final QuietRuntimeException DECODE_FAILED =
new QuietRuntimeException("A packet did not decode successfully (invalid data). For more "
+ "information, launch Velocity with -Dvelocity.packet-decode-logging=true to see more.");
private static final boolean DIRECTION_VALIDATION = VelocityProperties.readBoolean("velocity.packet-direction-validation", true);

private final ProtocolUtils.Direction direction;
private StateRegistry state;
Expand Down Expand Up @@ -74,7 +76,7 @@ private void tryDecode(ChannelHandlerContext ctx, ByteBuf buf) throws Exception
MinecraftPacket packet = this.registry.createPacket(packetId);
if (packet == null) {
buf.readerIndex(originalReaderIndex);
if (this.direction == ProtocolUtils.Direction.SERVERBOUND && this.state != StateRegistry.PLAY) {
if (DIRECTION_VALIDATION && this.direction == ProtocolUtils.Direction.SERVERBOUND && this.state != StateRegistry.PLAY) {
buf.release();
throw this.handleInvalidPacketId(packetId);
}
Expand Down