Add ENet option to disable server relaying.

It's useless when building fully authoritative servers, and prevents
various kinds of abuse.

1 files changed, 47 insertions, 23 deletions

diff --git a/modules/enet/networked_multiplayer_enet.cpp b/modules/enet/networked_multiplayer_enet.cpp
index 2f6ed5efc0..2f5307d041 100644
--- a/modules/enet/networked_multiplayer_enet.cpp
+++ b/modules/enet/networked_multiplayer_enet.cpp
@@ -255,6 +255,10 @@ void NetworkedMultiplayerENet::poll() {
 				emit_signal("peer_connected", *new_id);
 
 				if (server) {
+					// Do not notify other peers when server_relay is disabled.
+					if (!server_relay)
+						break;
+
 					// Someone connected, notify all the peers available
 					for (Map<int, ENetPeer *>::Element *E = peer_map.front(); E; E = E->next()) {
 
@@ -287,31 +291,34 @@ void NetworkedMultiplayerENet::poll() {
 					if (!server) {
 						emit_signal("connection_failed");
 					}
-				} else {
+					// Never fully connected.
+					break;
+				}
 
-					if (server) {
-						// Someone disconnected, notify everyone else
-						for (Map<int, ENetPeer *>::Element *E = peer_map.front(); E; E = E->next()) {
+				if (!server) {
 
-							if (E->key() == *id)
-								continue;
+					// Client just disconnected from server.
+					emit_signal("server_disconnected");
+					close_connection();
+					return;
+				} else if (server_relay) {
 
-							ENetPacket *packet = enet_packet_create(NULL, 8, ENET_PACKET_FLAG_RELIABLE);
-							encode_uint32(SYSMSG_REMOVE_PEER, &packet->data[0]);
-							encode_uint32(*id, &packet->data[4]);
-							enet_peer_send(E->get(), SYSCH_CONFIG, packet);
-						}
-					} else {
-						emit_signal("server_disconnected");
-						close_connection();
-						return;
-					}
+					// Server just received a client disconnect and is in relay mode, notify everyone else.
+					for (Map<int, ENetPeer *>::Element *E = peer_map.front(); E; E = E->next()) {
+
+						if (E->key() == *id)
+							continue;
 
-					emit_signal("peer_disconnected", *id);
-					peer_map.erase(*id);
-					memdelete(id);
+						ENetPacket *packet = enet_packet_create(NULL, 8, ENET_PACKET_FLAG_RELIABLE);
+						encode_uint32(SYSMSG_REMOVE_PEER, &packet->data[0]);
+						encode_uint32(*id, &packet->data[4]);
+						enet_peer_send(E->get(), SYSCH_CONFIG, packet);
+					}
 				}
 
+				emit_signal("peer_disconnected", *id);
+				peer_map.erase(*id);
+				memdelete(id);
 			} break;
 			case ENET_EVENT_TYPE_RECEIVE: {
 
@@ -361,7 +368,13 @@ void NetworkedMultiplayerENet::poll() {
 
 						packet.from = *id;
 
-						if (target == 0) {
+						if (target == 1) {
+							// To myself and only myself
+							incoming_packets.push_back(packet);
+						} else if (!server_relay) {
+							// No other destination is allowed when server is not relaying
+							continue;
+						} else if (target == 0) {
 							// Re-send to everyone but sender :|
 
 							incoming_packets.push_back(packet);
@@ -398,9 +411,6 @@ void NetworkedMultiplayerENet::poll() {
 								enet_packet_destroy(packet.packet);
 							}
 
-						} else if (target == 1) {
-							// To myself and only myself
-							incoming_packets.push_back(packet);
 						} else {
 							// To someone else, specifically
 							ERR_CONTINUE(!peer_map.has(target));
@@ -827,6 +837,16 @@ bool NetworkedMultiplayerENet::is_always_ordered() const {
 	return always_ordered;
 }
 
+void NetworkedMultiplayerENet::set_server_relay_enabled(bool p_enabled) {
+	ERR_FAIL_COND(active);
+
+	server_relay = p_enabled;
+}
+
+bool NetworkedMultiplayerENet::is_server_relay_enabled() const {
+	return server_relay;
+}
+
 void NetworkedMultiplayerENet::_bind_methods() {
 
 	ClassDB::bind_method(D_METHOD("create_server", "port", "max_clients", "in_bandwidth", "out_bandwidth"), &NetworkedMultiplayerENet::create_server, DEFVAL(32), DEFVAL(0), DEFVAL(0));
@@ -847,11 +867,14 @@ void NetworkedMultiplayerENet::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("get_channel_count"), &NetworkedMultiplayerENet::get_channel_count);
 	ClassDB::bind_method(D_METHOD("set_always_ordered", "ordered"), &NetworkedMultiplayerENet::set_always_ordered);
 	ClassDB::bind_method(D_METHOD("is_always_ordered"), &NetworkedMultiplayerENet::is_always_ordered);
+	ClassDB::bind_method(D_METHOD("set_server_relay_enabled", "enabled"), &NetworkedMultiplayerENet::set_server_relay_enabled);
+	ClassDB::bind_method(D_METHOD("is_server_relay_enabled"), &NetworkedMultiplayerENet::is_server_relay_enabled);
 
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "compression_mode", PROPERTY_HINT_ENUM, "None,Range Coder,FastLZ,ZLib,ZStd"), "set_compression_mode", "get_compression_mode");
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "transfer_channel"), "set_transfer_channel", "get_transfer_channel");
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "channel_count"), "set_channel_count", "get_channel_count");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "always_ordered"), "set_always_ordered", "is_always_ordered");
+	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "server_relay"), "set_server_relay_enabled", "is_server_relay_enabled");
 
 	BIND_ENUM_CONSTANT(COMPRESS_NONE);
 	BIND_ENUM_CONSTANT(COMPRESS_RANGE_CODER);
@@ -865,6 +888,7 @@ NetworkedMultiplayerENet::NetworkedMultiplayerENet() {
 	active = false;
 	server = false;
 	refuse_connections = false;
+	server_relay = true;
 	unique_id = 0;
 	target_peer = 0;
 	current_packet.packet = NULL;