Paper/Spigot-Server-Patches/0338-Duplicate-UUID-Resolve-Option.patch

From 2a6d7b5cf9db036928914e854416039d7c8a14af Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sat, 21 Jul 2018 14:27:34 -0400
Subject: [PATCH] Duplicate UUID Resolve Option

Due to a bug in https://github.com/PaperMC/Paper/commit/2e29af3df05ec0a383f48be549d1c03200756d24
which was added all the way back in March of 2016, it was unknown (potentially not at the time)
that an entity might actually change the seed of the random object.

At some point, EntitySquid did start setting the seed. Due to this shared random, this caused
every entity to use a Random object with a predictable seed.

This has caused entities to potentially generate with the same UUID....

Over the years, servers have had entities disappear, but no sign of trouble
because CraftBukkit removed the log lines indicating that something was wrong.

We have fixed the root issue causing duplicate UUID's, however we now have chunk
files full of entities that have the same UUID as another entity!

When these chunks load, the 2nd entity will not be added to the world correctly.

If that chunk loads in a different order in the future, then it will reverse and the
missing one is now the one added to the world and not the other. This results in very
inconsistent entity behavior.

This change allows you to recover any duplicate entity by generating a new UUID for it.
This also lets you delete them instead if you don't want to risk having new entities added to
the world that you previously did not see.

But for those who are ok with leaving this inconsistent behavior, you may use WARN or NOTHING options.

It is recommended you regenerate the entities, as these were legit entities, and deserve your love.

diff --git a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
index 14c8edeff..e3f6557e1 100644
--- a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
@@ -541,4 +541,40 @@ public class PaperWorldConfig {
             log("Bed Search Radius: " + bedSearchRadius);
         }
     }
+
+    public enum DuplicateUUIDMode {
+        REGEN, DELETE, NOTHING, WARN
+    }
+    public DuplicateUUIDMode duplicateUUIDMode = DuplicateUUIDMode.REGEN;
+    public void repairDuplicateUUID() {
+        String desiredMode = getString("duplicate-uuid-resolver", "regenerate").toLowerCase().trim();
+        switch (desiredMode.toLowerCase()) {
+            case "regen":
+            case "regenerate":
+                duplicateUUIDMode = DuplicateUUIDMode.REGEN;
+                log("Duplicate UUID Resolve: Regenerate New UUID");
+                break;
+            case "remove":
+            case "delete":
+                duplicateUUIDMode = DuplicateUUIDMode.DELETE;
+                log("Duplicate UUID Resolve: Delete Entity");
+                break;
+            case "silent":
+            case "nothing":
+                duplicateUUIDMode = DuplicateUUIDMode.NOTHING;
+                logError("Duplicate UUID Resolve: Do Nothing (no logs) - Warning, may lose indication of bad things happening");
+                logError("PaperMC Strongly discourages use of this setting! Triggering these messages means SOMETHING IS WRONG!");
+                break;
+            case "log":
+            case "warn":
+                duplicateUUIDMode = DuplicateUUIDMode.WARN;
+                log("Duplicate UUID Resolve: Warn (do nothing but log it happened, may be spammy)");
+                break;
+            default:
+                duplicateUUIDMode = DuplicateUUIDMode.WARN;
+                logError("Warning: Invalidate duplicate-uuid-resolver config " + desiredMode + " - must be one of: regen, delete, nothing, warn");
+                log("Duplicate UUID Resolve: Warn (do nothing but log it happened, may be spammy)");
+                break;
+        }
+    }
 }
diff --git a/src/main/java/net/minecraft/server/Chunk.java b/src/main/java/net/minecraft/server/Chunk.java
index 04adf4e3c..ea9559583 100644
--- a/src/main/java/net/minecraft/server/Chunk.java
+++ b/src/main/java/net/minecraft/server/Chunk.java
@@ -1,5 +1,10 @@
 package net.minecraft.server;
 
+// Paper start
+import com.destroystokyo.paper.PaperWorldConfig.DuplicateUUIDMode;
+import java.util.HashMap;
+import java.util.UUID;
+// Paper end
 import com.destroystokyo.paper.exception.ServerInternalException;
 import com.google.common.base.Predicate;
 import com.google.common.collect.Maps;
@@ -31,6 +36,7 @@ public class Chunk {
     public final World world;
     public final int[] heightMap;
     public Long scheduledForUnload; // Paper - delay chunk unloads
+    private static final Logger logger = LogManager.getLogger(); // Paper
     public final int locX;
     public final int locZ;
     private boolean m;
@@ -658,6 +664,7 @@ public class Chunk {
         if (i != this.locX || j != this.locZ) {
             Chunk.e.warn("Wrong location! ({}, {}) should be ({}, {}), {}", Integer.valueOf(i), Integer.valueOf(j), Integer.valueOf(this.locX), Integer.valueOf(this.locZ), entity);
             entity.die();
+            return; // Paper
         }
 
         int k = MathHelper.floor(entity.locY / 16.0D);
@@ -851,6 +858,37 @@ public class Chunk {
 
         for (int j = 0; j < i; ++j) {
             List entityslice = aentityslice[j]; // Spigot
+            // Paper start
+            DuplicateUUIDMode mode = world.paperConfig.duplicateUUIDMode;
+            if (mode == DuplicateUUIDMode.DELETE || mode == DuplicateUUIDMode.REGEN) {
+                Map<UUID, Entity> thisChunk = new HashMap<>();
+                for (Iterator<Entity> iterator = ((List<Entity>) entityslice).iterator(); iterator.hasNext(); ) {
+                    Entity entity = iterator.next();
+                    Entity other = ((WorldServer) world).entitiesByUUID.get(entity.uniqueID);
+                    if (other == null) {
+                        other = thisChunk.get(entity.uniqueID);
+                    }
+                    if (other != null) {
+                        switch (mode) {
+                            case REGEN: {
+                                entity.setUUID(UUID.randomUUID());
+                                logger.error("Duplicate UUID found used by " + other);
+                                logger.error("Regenerated a new UUID for " + entity);
+                                break;
+                            }
+                            case DELETE: {
+                                logger.error("Duplicate UUID found used by " + other);
+                                logger.error("Deleting duplicate entity " + entity);
+                                entity.die();
+                                iterator.remove();
+                                break;
+                            }
+                        }
+                    }
+                    thisChunk.put(entity.uniqueID, entity);
+                }
+            }
+            // Paper end
 
             this.world.a((Collection) entityslice);
         }
diff --git a/src/main/java/net/minecraft/server/Entity.java b/src/main/java/net/minecraft/server/Entity.java
index 0d3af8cb7..7188d0c99 100644
--- a/src/main/java/net/minecraft/server/Entity.java
+++ b/src/main/java/net/minecraft/server/Entity.java
@@ -2614,6 +2614,7 @@ public abstract class Entity implements ICommandListener, KeyedObject { // Paper
         });
     }
 
+    public void setUUID(UUID uuid) { a(uuid); } // Paper - OBFHELPER
     public void a(UUID uuid) {
         this.uniqueID = uuid;
         this.ar = this.uniqueID.toString();
diff --git a/src/main/java/net/minecraft/server/WorldServer.java b/src/main/java/net/minecraft/server/WorldServer.java
index 994d4bbb8..1244baf45 100644
--- a/src/main/java/net/minecraft/server/WorldServer.java
+++ b/src/main/java/net/minecraft/server/WorldServer.java
@@ -42,7 +42,7 @@ public class WorldServer extends World implements IAsyncTaskHandler {
     private final PlayerChunkMap manager;
     // private final Set<NextTickListEntry> nextTickListHash = Sets.newHashSet();
     private final HashTreeSet<NextTickListEntry> nextTickList = new HashTreeSet<NextTickListEntry>(); // CraftBukkit - HashTreeSet
-    private final Map<UUID, Entity> entitiesByUUID = Maps.newHashMap();
+    public final Map<UUID, Entity> entitiesByUUID = Maps.newHashMap(); // Paper
     public boolean savingDisabled;
     private boolean Q;
     private int emptyTime;
@@ -1177,14 +1177,17 @@ public class WorldServer extends World implements IAsyncTaskHandler {
                     this.f.remove(entity1);
                 } else {
                     if (!(entity instanceof EntityHuman)) {
-                        WorldServer.a.error("Keeping entity {} that already exists with UUID {}", entity1, uuid.toString()); // CraftBukkit // Paper
-                        WorldServer.a.error("Deleting duplicate entity {}", entity); // Paper
-                        if (DEBUG_ENTITIES) {
-                            if (entity1.addedToWorldStack != null) {
-                                entity1.addedToWorldStack.printStackTrace();
+                        if (entity.world.paperConfig.duplicateUUIDMode != com.destroystokyo.paper.PaperWorldConfig.DuplicateUUIDMode.NOTHING) {
+                            WorldServer.a.error("Keeping entity {} that already exists with UUID {}", entity1, uuid.toString()); // CraftBukkit // Paper
+                            WorldServer.a.error("Duplicate entity {} will not be added to the world. See paper.yml duplicate-uuid-resolver and set this to either regen, delete or nothing to get rid of this message", entity); // Paper
+                            if (DEBUG_ENTITIES) {
+                                if (entity1.addedToWorldStack != null) {
+                                    entity1.addedToWorldStack.printStackTrace();
+                                }
+                                getAddToWorldStackTrace(entity).printStackTrace();
                             }
-                            getAddToWorldStackTrace(entity).printStackTrace();
                         }
+
                         return false;
                     }
 
@@ -1206,7 +1209,7 @@ public class WorldServer extends World implements IAsyncTaskHandler {
             entity.addedToWorldStack = getAddToWorldStackTrace(entity);
         }
         Entity old = this.entitiesByUUID.put(entity.getUniqueID(), entity);
-        if (old != null && old.getId() != entity.getId() && old.valid) {
+        if (old != null && old.getId() != entity.getId() && old.valid && entity.world.paperConfig.duplicateUUIDMode != com.destroystokyo.paper.PaperWorldConfig.DuplicateUUIDMode.NOTHING) {
             Logger logger = LogManager.getLogger();
             logger.error("Overwrote an existing entity " + old + " with " + entity);
             if (DEBUG_ENTITIES) {
-- 
2.18.0