1 files changed, 46 insertions, 8 deletions

diff --git a/modules/multiplayer/scene_replication_interface.cpp b/modules/multiplayer/scene_replication_interface.cpp
index e1b7b0c346..68b6bc4a24 100644
--- a/modules/multiplayer/scene_replication_interface.cpp
+++ b/modules/multiplayer/scene_replication_interface.cpp
@@ -125,6 +125,20 @@ void SceneReplicationInterface::on_reset() {
 }
 
 void SceneReplicationInterface::on_network_process() {
+	// Prevent endless stalling in case of unforeseen spawn errors.
+	if (spawn_queue.size()) {
+		ERR_PRINT("An error happened during last spawn, this usually means the 'ready' signal was not emitted by the spawned node.");
+		for (const ObjectID &oid : spawn_queue) {
+			Node *node = get_id_as<Node>(oid);
+			ERR_CONTINUE(!node);
+			if (node->is_connected(SceneStringNames::get_singleton()->ready, callable_mp(this, &SceneReplicationInterface::_node_ready))) {
+				node->disconnect(SceneStringNames::get_singleton()->ready, callable_mp(this, &SceneReplicationInterface::_node_ready));
+			}
+		}
+		spawn_queue.clear();
+	}
+
+	// Process timed syncs.
 	uint64_t msec = OS::get_singleton()->get_ticks_msec();
 	for (KeyValue<int, PeerInfo> &E : peers_info) {
 		const HashSet<ObjectID> to_sync = E.value.sync_nodes;
@@ -144,17 +158,39 @@ Error SceneReplicationInterface::on_spawn(Object *p_obj, Variant p_config) {
 	// Track node.
 	const ObjectID oid = node->get_instance_id();
 	TrackedNode &tobj = _track(oid);
+
+	// Spawn state needs to be callected after "ready", but the spawn order follows "enter_tree".
 	ERR_FAIL_COND_V(tobj.spawner != ObjectID(), ERR_ALREADY_IN_USE);
 	tobj.spawner = spawner->get_instance_id();
-	spawned_nodes.insert(oid);
+	spawn_queue.insert(oid);
+	node->connect(SceneStringNames::get_singleton()->ready, callable_mp(this, &SceneReplicationInterface::_node_ready).bind(oid), Node::CONNECT_ONE_SHOT);
+	return OK;
+}
+
+void SceneReplicationInterface::_node_ready(const ObjectID &p_oid) {
+	ERR_FAIL_COND(!spawn_queue.has(p_oid)); // Bug.
 
-	if (multiplayer->has_multiplayer_peer() && spawner->is_multiplayer_authority()) {
-		if (tobj.net_id == 0) {
-			tobj.net_id = ++last_net_id;
+	// If we are a nested spawn, we need to wait until the parent is ready.
+	if (p_oid != *(spawn_queue.begin())) {
+		return;
+	}
+
+	for (const ObjectID &oid : spawn_queue) {
+		ERR_CONTINUE(!tracked_nodes.has(oid));
+
+		TrackedNode &tobj = tracked_nodes[oid];
+		MultiplayerSpawner *spawner = get_id_as<MultiplayerSpawner>(tobj.spawner);
+		ERR_CONTINUE(!spawner);
+
+		spawned_nodes.insert(oid);
+		if (multiplayer->has_multiplayer_peer() && spawner->is_multiplayer_authority()) {
+			if (tobj.net_id == 0) {
+				tobj.net_id = ++last_net_id;
+			}
+			_update_spawn_visibility(0, oid);
 		}
-		_update_spawn_visibility(0, oid);
 	}
-	return OK;
+	spawn_queue.clear();
 }
 
 Error SceneReplicationInterface::on_despawn(Object *p_obj, Variant p_config) {
@@ -706,6 +742,7 @@ Error SceneReplicationInterface::on_sync_receive(int p_from, const uint8_t *p_bu
 		ofs += 4;
 		uint32_t size = decode_uint32(&p_buffer[ofs]);
 		ofs += 4;
+		ERR_FAIL_COND_V(size > uint32_t(p_buffer_len - ofs), ERR_INVALID_DATA);
 		MultiplayerSynchronizer *sync = nullptr;
 		if (net_id & 0x80000000) {
 			sync = Object::cast_to<MultiplayerSynchronizer>(multiplayer->get_path_cache()->get_cached_object(p_from, net_id & 0x7FFFFFFF));
@@ -720,14 +757,15 @@ Error SceneReplicationInterface::on_sync_receive(int p_from, const uint8_t *p_bu
 		}
 		Node *node = sync->get_root_node();
 		if (sync->get_multiplayer_authority() != p_from || !node) {
-			ERR_CONTINUE(true);
+			// Not valid for me.
+			ofs += size;
+			ERR_CONTINUE_MSG(true, "Ignoring sync data from non-authority or for missing node.");
 		}
 		if (!sync->update_inbound_sync_time(time)) {
 			// State is too old.
 			ofs += size;
 			continue;
 		}
-		ERR_FAIL_COND_V(size > uint32_t(p_buffer_len - ofs), ERR_BUG);
 		const List<NodePath> props = sync->get_replication_config()->get_sync_properties();
 		Vector<Variant> vars;
 		vars.resize(props.size());