From 26bb8f45a6d7b397ecb8294bc1ce5b9ccbc5605a Mon Sep 17 00:00:00 2001
From: Myst1cS04p <myst1cs04p@gmail.com>
Date: Mon, 17 Nov 2025 07:53:39 +0300
Subject: [PATCH] Fix setVelocity infinite regress crash

Added a guard flag to BukkitPlayer.setVelocity and PlayerKnockbackListener.onPlayerVelocity.
Hopefully ts guard flag will stop ts plugin from looping endlessly and crashing the server
---
 .../knockbacksync/player/BukkitPlayer.java    | 20 ++++++++++++++++++-
 .../listener/PlayerKnockbackListener.java     |  5 +++++
 .../knockbacksync/player/PlayerData.java      |  2 ++
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/bukkit/src/main/java/me/caseload/knockbacksync/player/BukkitPlayer.java b/bukkit/src/main/java/me/caseload/knockbacksync/player/BukkitPlayer.java
index f928fc1c..02db0525 100644
--- a/bukkit/src/main/java/me/caseload/knockbacksync/player/BukkitPlayer.java
+++ b/bukkit/src/main/java/me/caseload/knockbacksync/player/BukkitPlayer.java
@@ -8,6 +8,7 @@
 import com.google.common.base.Preconditions;
 import me.caseload.knockbacksync.BukkitBase;
 import me.caseload.knockbacksync.Platform;
+import me.caseload.knockbacksync.manager.PlayerDataManager;
 import me.caseload.knockbacksync.world.FoliaWorld;
 import me.caseload.knockbacksync.world.PlatformWorld;
 import me.caseload.knockbacksync.world.SpigotWorld;
@@ -190,7 +191,24 @@ public int getMainHandKnockbackLevel() {
 
     @Override
     public void setVelocity(Vector3d adjustedVelocity) {
-        bukkitPlayer.setVelocity(new Vector(adjustedVelocity.x, adjustedVelocity.y, adjustedVelocity.z));
+        PlayerData data = PlayerDataManager.getPlayerData(this.getUser());
+
+        if(data == null){
+            // Fallback to normal behavior in the absence of a guard
+            bukkitPlayer.setVelocity(new Vector(adjustedVelocity.x, adjustedVelocity.y, adjustedVelocity.z));
+            return;
+        }
+
+        if(data.isVelocityGuard()){
+            return; // Already applying velocity
+        }
+
+        data.setVelocityGuard(true);
+        try {
+            this.bukkitPlayer.setVelocity(new Vector(adjustedVelocity.x, adjustedVelocity.y, adjustedVelocity.z));
+        } finally {
+            data.setVelocityGuard(false);
+        }
     }
 
     @Override
diff --git a/common/src/main/java/me/caseload/knockbacksync/listener/PlayerKnockbackListener.java b/common/src/main/java/me/caseload/knockbacksync/listener/PlayerKnockbackListener.java
index 0878ac17..fe39346a 100644
--- a/common/src/main/java/me/caseload/knockbacksync/listener/PlayerKnockbackListener.java
+++ b/common/src/main/java/me/caseload/knockbacksync/listener/PlayerKnockbackListener.java
@@ -21,6 +21,9 @@ public void onPlayerVelocity(PlatformPlayer victim, Vector3d velocity) {
         PlayerData victimPlayerData = PlayerDataManager.getPlayerData(user);
         if (victimPlayerData == null)
             return;
+        if (victimPlayerData.isVelocityGuard()) { // Prevent velocity setter from looping infinitely
+            return;
+        }
 
         if (victimPlayerData.getNotNullPing() < PlayerData.PING_OFFSET)
             return;
@@ -50,6 +53,8 @@ else if (victimPlayerData.isOffGroundSyncEnabled())
         else
             return;
 
+        victimPlayerData.setVelocityGuard(true);;
         victim.setVelocity(adjustedVelocity);
+        victimPlayerData.setVelocityGuard(false);
     }
 }
\ No newline at end of file
diff --git a/common/src/main/java/me/caseload/knockbacksync/player/PlayerData.java b/common/src/main/java/me/caseload/knockbacksync/player/PlayerData.java
index dbad8279..b8efa0bd 100644
--- a/common/src/main/java/me/caseload/knockbacksync/player/PlayerData.java
+++ b/common/src/main/java/me/caseload/knockbacksync/player/PlayerData.java
@@ -47,6 +47,8 @@ public class PlayerData {
     public static final long PING_OFFSET = 25;
 
     private static Field playerField;
+    @Getter @Setter
+    private boolean velocityGuard = false; // Used to prevent infinite recursion while setting velocity
 
     public final Queue<Pair<Integer, Long>> transactionsSent = new ConcurrentLinkedQueue<>();
     public final Queue<Pair<Long, Long>> keepaliveMap = new ConcurrentLinkedQueue<>();