From 7fe2fc71e928e5980ae143acf51bda3bd21b394c Mon Sep 17 00:00:00 2001
From: Andrew Steinborn <git@steinborn.me>
Date: Fri, 25 Dec 2020 17:03:01 -0500
Subject: [PATCH] Add some small debug for refcount issues with plugin
 messages.

---
 .../proxy/protocol/packet/PluginMessage.java                | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/PluginMessage.java b/proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/PluginMessage.java
index 5b9b3f136..ecd610629 100644
--- a/proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/PluginMessage.java
+++ b/proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/PluginMessage.java
@@ -63,6 +63,12 @@ public class PluginMessage extends DeferredByteBufHolder implements MinecraftPac
     if (channel == null) {
       throw new IllegalStateException("Channel is not specified.");
     }
+
+    if (refCnt() == 0) {
+      throw new IllegalStateException("Plugin message contents for " + this.channel
+          + " freed too many times.");
+    }
+
     if (version.compareTo(ProtocolVersion.MINECRAFT_1_13) >= 0) {
       ProtocolUtils.writeString(buf, transformLegacyToModernChannel(this.channel));
     } else {