Paper/Spigot-Server-Patches/0351-Duplicate-UUID-Resolve-Option.patch

From 0000000000000000000000000000000000000000 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 fbf3ccfb347a5ba6e895339e9576629d940d1aa4..38d25a12c6a52d8a83214e2a0f43a218cf15ceac 100644
--- a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
@@ -401,4 +401,43 @@ public class PaperWorldConfig {
     private void preventMovingIntoUnloadedChunks() {
         preventMovingIntoUnloadedChunks = getBoolean("prevent-moving-into-unloaded-chunks", false);
     }
+
+    public enum DuplicateUUIDMode {
+        SAFE_REGEN, DELETE, NOTHING, WARN
+    }
+    public DuplicateUUIDMode duplicateUUIDMode = DuplicateUUIDMode.SAFE_REGEN;
+    public int duplicateUUIDDeleteRange = 32;
+    private void repairDuplicateUUID() {
+        String desiredMode = getString("duplicate-uuid-resolver", "saferegen").toLowerCase().trim();
+        duplicateUUIDDeleteRange = getInt("duplicate-uuid-saferegen-delete-range", duplicateUUIDDeleteRange);
+        switch (desiredMode.toLowerCase()) {
+            case "regen":
+            case "regenerate":
+            case "saferegen":
+            case "saferegenerate":
+                duplicateUUIDMode = DuplicateUUIDMode.SAFE_REGEN;
+                log("Duplicate UUID Resolve: Regenerate New UUID if distant (Delete likely duplicates within " + duplicateUUIDDeleteRange + " blocks)");
+                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");
+                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: Invalid 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 3cb1ee261724e34a23c4a0f98673da1597786a01..b258d4a85c41c2de55a28c565766f57c3f1604ff 100644
--- a/src/main/java/net/minecraft/server/Chunk.java
+++ b/src/main/java/net/minecraft/server/Chunk.java
@@ -504,6 +504,7 @@ public class Chunk implements IChunkAccess {
         if (i != this.loc.x || j != this.loc.z) {
             Chunk.LOGGER.warn("Wrong location! ({}, {}) should be ({}, {}), {}", i, j, this.loc.x, this.loc.z, entity);
             entity.dead = true;
+            return; // Paper
         }
 
         int k = MathHelper.floor(entity.locY() / 16.0D);
diff --git a/src/main/java/net/minecraft/server/Entity.java b/src/main/java/net/minecraft/server/Entity.java
index 1dbeda9fb385be29b3bb20c33a0487334c6e7c16..595adbeb253529720e72f695667d5bf9584ebaf0 100644
--- a/src/main/java/net/minecraft/server/Entity.java
+++ b/src/main/java/net/minecraft/server/Entity.java
@@ -2711,6 +2711,7 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, Ke
         });
     }
 
+    public final void setUUID(UUID uuid) { a_(uuid); } // Paper - OBFHELPER
     public void a_(UUID uuid) {
         this.uniqueID = uuid;
         this.ae = this.uniqueID.toString();
diff --git a/src/main/java/net/minecraft/server/PlayerChunkMap.java b/src/main/java/net/minecraft/server/PlayerChunkMap.java
index 6d048fbb48444885051efcb83a55d32047ff6517..8370bb32f9ca5c88cea52b90a6f361ad5333bbb2 100644
--- a/src/main/java/net/minecraft/server/PlayerChunkMap.java
+++ b/src/main/java/net/minecraft/server/PlayerChunkMap.java
@@ -1,6 +1,7 @@
 package net.minecraft.server;
 
 import co.aikar.timings.Timing; // Paper
+import com.destroystokyo.paper.PaperWorldConfig; // Paper
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.ComparisonChain; // Paper
@@ -23,14 +24,17 @@ import it.unimi.dsi.fastutil.objects.ObjectIterator;
 import java.io.File;
 import java.io.IOException;
 import java.io.Writer;
+import java.util.HashMap; // Paper
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Map; // Paper
 import java.util.Objects;
 import java.util.Optional;
 import java.util.Queue;
 import java.util.Set;
 import java.util.concurrent.CancellationException;
+import java.util.UUID; // Paper
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionException;
 import java.util.concurrent.Executor;
@@ -652,12 +656,12 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
                             // CraftBukkit start - these are spawned serialized (DefinedStructure) and we don't call an add event below at the moment due to ordering complexities
                             boolean needsRemoval = false;
                             if (chunk.needsDecoration && !this.world.getServer().getServer().getSpawnNPCs() && entity instanceof NPC) {
-                                entity.die();
+                                entity.dead = true; // Paper
                                 needsRemoval = true;
                             }
-
-                            if (!(entity instanceof EntityHuman) && (needsRemoval || !this.world.addEntityChunk(entity))) {
-                                // CraftBukkit end
+                            // CraftBukkit end
+                            checkDupeUUID(entity); // Paper
+                            if (!(entity instanceof EntityHuman) && (entity.dead || !this.world.addEntityChunk(entity))) { // Paper
                                 if (list == null) {
                                     list = Lists.newArrayList(new Entity[]{entity});
                                 } else {
@@ -684,6 +688,44 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
         });
     }
 
+    // Paper start
+    private void checkDupeUUID(Entity entity) {
+        PaperWorldConfig.DuplicateUUIDMode mode = world.paperConfig.duplicateUUIDMode;
+        if (mode != PaperWorldConfig.DuplicateUUIDMode.WARN
+            && mode != PaperWorldConfig.DuplicateUUIDMode.DELETE
+            && mode != PaperWorldConfig.DuplicateUUIDMode.SAFE_REGEN) {
+            return;
+        }
+        Entity other = world.getEntity(entity.uniqueID);
+
+        if (mode == PaperWorldConfig.DuplicateUUIDMode.SAFE_REGEN && other != null && !other.dead
+                && Objects.equals(other.getSaveID(), entity.getSaveID())
+                && entity.getBukkitEntity().getLocation().distance(other.getBukkitEntity().getLocation()) < world.paperConfig.duplicateUUIDDeleteRange
+        ) {
+            if (World.DEBUG_ENTITIES) LOGGER.warn("[DUPE-UUID] Duplicate UUID found used by " + other + ", deleted entity " + entity + " because it was near the duplicate and likely an actual duplicate. See https://github.com/PaperMC/Paper/issues/1223 for discussion on what this is about.");
+            entity.dead = true;
+            return;
+        }
+        if (other != null && !other.dead) {
+            switch (mode) {
+                case SAFE_REGEN: {
+                    entity.setUUID(UUID.randomUUID());
+                    if (World.DEBUG_ENTITIES) LOGGER.warn("[DUPE-UUID] Duplicate UUID found used by " + other + ", regenerated UUID for " + entity + ". See https://github.com/PaperMC/Paper/issues/1223 for discussion on what this is about.");
+                    break;
+                }
+                case DELETE: {
+                    if (World.DEBUG_ENTITIES) LOGGER.warn("[DUPE-UUID] Duplicate UUID found used by " + other + ", deleted entity " + entity + ". See https://github.com/PaperMC/Paper/issues/1223 for discussion on what this is about.");
+                    entity.dead = true;
+                    break;
+                }
+                default:
+                    if (World.DEBUG_ENTITIES) LOGGER.warn("[DUPE-UUID] Duplicate UUID found used by " + other + ", doing nothing to " + entity + ". See https://github.com/PaperMC/Paper/issues/1223 for discussion on what this is about.");
+                    break;
+            }
+        }
+    }
+    // Paper end
+
     public CompletableFuture<Either<Chunk, PlayerChunk.Failure>> a(PlayerChunk playerchunk) {
         ChunkCoordIntPair chunkcoordintpair = playerchunk.i();
         CompletableFuture<Either<List<IChunkAccess>, PlayerChunk.Failure>> completablefuture = this.a(chunkcoordintpair, 1, (i) -> {
diff --git a/src/main/java/net/minecraft/server/WorldServer.java b/src/main/java/net/minecraft/server/WorldServer.java
index 676d160fe5132177a7d91cbf514a386607826964..628d1a5555ec70571c0467900c884cc419cbab37 100644
--- a/src/main/java/net/minecraft/server/WorldServer.java
+++ b/src/main/java/net/minecraft/server/WorldServer.java
@@ -4,6 +4,8 @@ import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.Iterables;
 import co.aikar.timings.TimingHistory; // Paper
 import co.aikar.timings.Timings; // Paper
+
+import com.destroystokyo.paper.PaperWorldConfig; // Paper
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
 import com.google.common.collect.Queues;
@@ -997,7 +999,22 @@ public class WorldServer extends World implements GeneratorAccessSeed {
         if (entity1 == null) {
             return false;
         } else {
+            // Paper start
+            if (entity1.dead) {
+                unregisterEntity(entity1); // remove the existing entity
+                return false;
+            }
+            // Paper end
             WorldServer.LOGGER.warn("Trying to add entity with duplicated UUID {}. Existing {}#{}, new: {}#{}", uuid, EntityTypes.getName(entity1.getEntityType()), entity1.getId(), EntityTypes.getName(entity.getEntityType()), entity.getId()); // CraftBukkit // Paper
+            // Paper start
+            if (DEBUG_ENTITIES && entity.world.paperConfig.duplicateUUIDMode != PaperWorldConfig.DuplicateUUIDMode.NOTHING) {
+                if (entity1.addedToWorldStack != null) {
+                    entity1.addedToWorldStack.printStackTrace();
+                }
+
+                getAddToWorldStackTrace(entity).printStackTrace();
+            }
+            // Paper end
             return true;
         }
     }