PaperMC/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/level/PlayerChunkMap.java b/src/main/java/net/minecraft/server/level/PlayerChunkMap.java
index f0347a71b5937f9b68a4024fd0595a2d3e98eef5..90a3ca4e92fefc1f20b2878686030e9123238384 100644
--- a/src/main/java/net/minecraft/server/level/PlayerChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/PlayerChunkMap.java
@@ -1,6 +1,7 @@
 package net.minecraft.server.level;
 
 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;
@@ -696,12 +700,12 @@ 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 net.minecraft.world.entity.npc.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 {
@@ -728,6 +732,44 @@ 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/level/WorldServer.java b/src/main/java/net/minecraft/server/level/WorldServer.java
index b8f0ea863b89bf9ddeef8104d09fe7f00b91f711..a6f3f773a2fbbf98f9ef1eb03a6b392fb9082d25 100644
--- a/src/main/java/net/minecraft/server/level/WorldServer.java
+++ b/src/main/java/net/minecraft/server/level/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;
@@ -1106,7 +1108,22 @@ 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;
         }
     }
diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index f024db3fe2a9fb9af536fe144b9e871712ae327a..abfda88ab1d0353bbb14ae99dea212941ab2e899 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -2796,6 +2796,7 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, ne
         });
     }
 
+    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/world/level/chunk/Chunk.java b/src/main/java/net/minecraft/world/level/chunk/Chunk.java
index 246a4b69e1b4ee6affa9564d50f261fac2f269d0..5539ee8552c4bcfa718a63dbd4c25bd232048bff 100644
--- a/src/main/java/net/minecraft/world/level/chunk/Chunk.java
+++ b/src/main/java/net/minecraft/world/level/chunk/Chunk.java
@@ -538,6 +538,7 @@ 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);