Fixed https://github.com/ViaVersion/ViaVersion/issues/4308

Co-authored-by: FlorianMichael <florian.michael07@gmail.com>

src/main/java/net/raphimc/viaproxy/injection/mixins/MixinConfigurationState.java

@@ -0,0 +1,46 @@
+/*
+ * This file is part of ViaProxy - https://github.com/RaphiMC/ViaProxy
+ * Copyright (C) 2021-2025 RK_01/RaphiMC and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package net.raphimc.viaproxy.injection.mixins;
+
+import com.viaversion.viaversion.api.protocol.packet.PacketWrapper;
+import com.viaversion.viaversion.protocols.v1_19_3to1_19_4.packet.ClientboundPackets1_19_4;
+import com.viaversion.viaversion.protocols.v1_20to1_20_2.storage.ConfigurationState;
+import net.raphimc.viaproxy.ViaProxy;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Mixin(value = ConfigurationState.class, remap = false)
+public abstract class MixinConfigurationState {
+
+    @Inject(method = "addPacketToQueue", at = @At("HEAD"), cancellable = true)
+    private void cancelQueuedPackets(PacketWrapper wrapper, boolean clientbound, CallbackInfo ci) {
+        // Dirty workaround for https://github.com/ViaVersion/ViaVersion/issues/4308 where queued packets
+        // without set packet type cause a disconnect after sent in play state, even when delayed until the client
+        // has transitioned to the play state as well. This is *very* bad as in worst will cause data loss and other
+        // issues but /shrug for now.
+        if (ViaProxy.getConfig().shouldWorkAroundConfigStatePacketQueue() && clientbound && wrapper.getPacketType() == null) {
+            final int unmappedId = wrapper.getId();
+            if (unmappedId == ClientboundPackets1_19_4.CONTAINER_CLOSE.getId() || unmappedId == ClientboundPackets1_19_4.CHUNKS_BIOMES.getId() || unmappedId == ClientboundPackets1_19_4.SET_ENTITY_MOTION.getId()) {
+                ci.cancel();
+            }
+        }
+    }
+
+}

src/main/java/net/raphimc/viaproxy/protocoltranslator/viaproxy/ViaProxyConfig.java

@@ -183,6 +183,13 @@ public class ViaProxyConfig {
     })
     private boolean fakeAcceptResourcePacks = false;
 
+    @Option("workaround-config-state-packet-queue")
+    @Description({
+            "Fixes https://github.com/ViaVersion/ViaVersion/issues/4308 where the config state packet queue causes a disconnect sometimes.",
+            "It's recommended to only enable this if you are experiencing issues with the config state packet queue (See above issue)."
+    })
+    private boolean workAroundConfigStatePacketQueue = false;
+
     public static ViaProxyConfig create(final File configFile) {
         final ConfigLoader<ViaProxyConfig> configLoader = new ConfigLoader<>(ViaProxyConfig.class);
         configLoader.getConfigOptions().setResetInvalidOptions(true).setRewriteConfig(true).setCommentSpacing(1);
@@ -478,6 +485,15 @@ public class ViaProxyConfig {
         this.save();
     }
 
+    public boolean shouldWorkAroundConfigStatePacketQueue() {
+        return this.workAroundConfigStatePacketQueue;
+    }
+
+    public void setWorkAroundConfigStatePacketQueue(final boolean workAroundConfigStatePacketQueue) {
+        this.workAroundConfigStatePacketQueue = workAroundConfigStatePacketQueue;
+        this.save();
+    }
+
     @Validator("target-version")
     private ProtocolVersion validateTargetVersion(final ProtocolVersion targetVersion) {
         if (targetVersion == null) {