fs2open.github.com/code/network/multi_lua.cpp

#include "multi_lua.h"

#include "network/multimsgs.h"
#include "network/multiutil.h"
#include "scripting/ade.h"
#include "scripting/ade_api.h"

//This will send a byte more per userdata, but catch more faults due to players having different APIs
//Also, it makes the remaining faults safer, since this way we'll only get invalid data, not accessing potentially invalid memory
#define SAFE_MULTI_LUA_USERDATA_SIZES true

static SCP_unordered_map<ushort, scripting::api::rpc_h_ref> rpc_map;

enum class lua_net_data_type : uint8_t { NIL, BOOL, NUMBER, STRING8, STRING16, USERDATA, TABLE };

static bool need_toss_packet(ushort target, short packet_source, ushort packetTime, UI_TIMESTAMP localTime) {
	//Ordering is enforced for packet source and execution targets. Meaning we neither order packets form different sources
	//(due to incomparibility of timestamps) or to different targets (due to semantic insignificance)
	static SCP_map<std::pair<ushort, short>, std::pair<ushort, UI_TIMESTAMP>> received_packets;

	//The idea is, that we reject packets which are in the past, unless the last packet we actually got is so far in the past, we're not sure if it might have overflowed
	//Basically, assume that if packetTime - lastPacketTime < 1000, then it's either delayed over 60 seconds, or not a past packet. If it's larger than that, compare it to
	//the difference of local timestamps. If the local timestamp is over 2^16, it's also safe, otherwise, allow a 10% delay margin.

	auto& channel = received_packets[{target, packet_source}];
	std::pair<ushort, UI_TIMESTAMP> newTimestamp = { std::move(packetTime), std::move(localTime) };

	if (!channel.second.isValid()) {
		//First packet for this channel
		channel = std::move(newTimestamp);
		return false;
	}

	if (newTimestamp.first - channel.first < 1000) {
		//The previous packet is less than a second ago. If this were a delayed packet, as a ushort, it'd have to be >60 seconds late, so effectively impossible.
		channel = std::move(newTimestamp);
		return false;
	}

	if (static_cast<int>(newTimestamp.first - channel.first) * 110 < ui_timestamp_get_delta(channel.second, newTimestamp.second)) {
		//The previous packet is, at most, 10% older than its age when it arrived. We expect that most delayed packets will happen when sent in quick succession,
		//so what needs to be guarded here are underflows, which produce very large values but will have very small timestamps. So as long as local and remote timestamp
		//somewhat agree, the packet's good. In addition, once ui_timestamp_get_delta exceeds 65 seconds, we can't tell anymore due to the remote timestamp being uint16,
		//but at that point we can just accept the packet as likely new.
		channel = std::move(newTimestamp);
		return false;
	}

	//If we're still here, then we've got a packet that has a very high remote time but a very short local time, so likely a packet whose high remote time indicates a
	//negative remote time. Toss is then. Also, since we toss the packet, we DON'T update the received packet index.
	return true;
}


static luacpp::LuaValue process_lua_userdata(ubyte* data, int& offset, lua_State* L) {
	luacpp::LuaValue retVal(L);
	uint16_t adeIdx;
	GET_USHORT(adeIdx);

#if SAFE_MULTI_LUA_USERDATA_SIZES
	uint8_t size;
	GET_DATA(size);
#endif

	const auto& objType = scripting::ade_manager::getInstance()->getEntry(adeIdx);
	if (objType.Type != 'o' || objType.Instanced || objType.Deserializer == nullptr
#if SAFE_MULTI_LUA_USERDATA_SIZES
		|| size != objType.Size
#endif
		) {
		//There is a case to be made for this to be an assert.
		//This happens when the scripting API changes but no multi bump occurs.
		LuaError(L, "Lua Network packet with Userdata has bad adeidx! Make sure every placer is using the same game version as the host.");
		throw lua_net_exception("Lua Network packet with Userdata has bad adeidx.");
	}
	
	//Create new LUA object and get handle
	auto newod = (char*)lua_newuserdata(L, objType.Size);
	//Create or get object metatable
	luaL_getmetatable(L, objType.Name);
	//Set the metatable for the object
	lua_setmetatable(L, -2);

	//Deserialize and fill newod space
	objType.Deserializer(L, objType, newod, data, offset);

	retVal.setReference(luacpp::UniqueLuaReference::create(L));

	// Remove the value again
	lua_pop(L, 1);

	return retVal;
}

static luacpp::LuaValue process_lua_data(ubyte* data, int& offset, lua_State* L) {
	uint8_t dataType = static_cast<uint8_t>(lua_net_data_type::NIL);
	GET_DATA(dataType);

	switch (static_cast<lua_net_data_type>(dataType)) {
	case lua_net_data_type::NIL:
		return luacpp::LuaValue::createNil(L);
	case lua_net_data_type::BOOL: {
		uint8_t value;
		GET_DATA(value);
		return luacpp::LuaValue::createValue(L, value != 0);
	}
	case lua_net_data_type::NUMBER: {
		float value;
		GET_FLOAT(value);
		return luacpp::LuaValue::createValue(L, value);
	}
	case lua_net_data_type::STRING8: {
		char text[0xff];
		GET_STRING(text);
		return luacpp::LuaValue::createValue(L, text);
	}
	case lua_net_data_type::STRING16: {
		char text[MAX_PACKET_SIZE];
		GET_STRING_16(text);
		return luacpp::LuaValue::createValue(L, text);
	}
	case lua_net_data_type::USERDATA:
		return process_lua_userdata(data, offset, L);
	case lua_net_data_type::TABLE: {
		luacpp::LuaTable table = luacpp::LuaTable::create(L);
		uint8_t entries = 0;
		GET_DATA(entries);
		for (uint8_t i = 0; i < entries; i++) {
			luacpp::LuaValue index = process_lua_data(data, offset, L);
			luacpp::LuaValue value = process_lua_data(data, offset, L);
			table.addValue(std::move(index), std::move(value));
		}
		return table;
	}
	default:
		UNREACHABLE("Got invalid lua multi packet data type %d!", dataType);
		return luacpp::LuaValue::createNil(L);
	}
}

static void send_lua_userdata(ubyte* data, int& packet_size, const luacpp::LuaValue& value) {
	lua_State* L = value.getLuaState();

	value.pushValue(L);
	lua_getmetatable(L, -1);

	int mtb_ldx = lua_gettop(L);
	lua_pushstring(L, "__adeid");
	lua_rawget(L, mtb_ldx);
	ushort adeIdx = static_cast<ushort>(lua_tonumber(L, -1));
	const auto& objType = scripting::ade_manager::getInstance()->getEntry(adeIdx);

	lua_pop(L, 3);

	ADD_USHORT(adeIdx);

#if SAFE_MULTI_LUA_USERDATA_SIZES
	uint8_t size = static_cast<uint8_t>(objType.Size);
	ADD_DATA(size);
#endif

	//Serialize
	objType.Serializer(L, objType, value, data, packet_size);
}


#define SEND_LUA_DATA_CHECK_SPACE(requiredSpace) \
if(MAX_PACKET_SIZE - packet_size < (requiredSpace)) { \
	LuaError(value.getLuaState(), "Tried to add too much data to a lua packet. Please reduce the amount of data to send. Maximum %d bytes supported!", MAX_PACKET_SIZE); \
	throw lua_net_exception("Tried to add too much data to a lua packet."); \
}

//17 Bytes is likely the largest userdata object (orientation matrices) we might need to send, so we want to make sure it will fit into the buffer if we try to add one.
#if SAFE_MULTI_LUA_USERDATA_SIZES
#define MAX_USERDATA_REQUIRED_ESTIMATE 17 + 2
#else
#define MAX_USERDATA_REQUIRED_ESTIMATE 17 + 1
#endif

static void send_lua_data(ubyte* data, int& packet_size, const luacpp::LuaValue& value) {
	switch (value.getValueType()) {
	case luacpp::ValueType::NIL:
	case luacpp::ValueType::NONE: {
		SEND_LUA_DATA_CHECK_SPACE(1);
		uint8_t type = static_cast<uint8_t>(lua_net_data_type::NIL);
		ADD_DATA(type);
		break;
	}
	case luacpp::ValueType::BOOLEAN: {
		SEND_LUA_DATA_CHECK_SPACE(2);
		uint8_t valuedata = value.getValue<bool>() ? 1 : 0;
		uint8_t type = static_cast<uint8_t>(lua_net_data_type::BOOL);
		ADD_DATA(type);
		ADD_DATA(valuedata);
		break;
	}
	case luacpp::ValueType::NUMBER: {
		SEND_LUA_DATA_CHECK_SPACE(1 + static_cast<int>(sizeof(float)));
		float valuedata = value.getValue<float>();
		uint8_t type = static_cast<uint8_t>(lua_net_data_type::NUMBER);
		ADD_DATA(type);
		ADD_FLOAT(valuedata);
		break;
	}
	case luacpp::ValueType::STRING: {
		SCP_string valuedata = value.getValue<SCP_string>();
		SEND_LUA_DATA_CHECK_SPACE(1 + static_cast<int>(valuedata.size()) + 2);
		bool isLongString = valuedata.size() > 0xff;
		uint8_t type = static_cast<uint8_t>(isLongString ? lua_net_data_type::STRING16 : lua_net_data_type::STRING8);
		ADD_DATA(type);
		if (isLongString)
			ADD_STRING_16(valuedata.c_str());
		else
			ADD_STRING(valuedata.c_str());
		break;
	}
	case luacpp::ValueType::USERDATA: {
		SEND_LUA_DATA_CHECK_SPACE(1 + MAX_USERDATA_REQUIRED_ESTIMATE);
		uint8_t type = static_cast<uint8_t>(lua_net_data_type::USERDATA);
		ADD_DATA(type);
		send_lua_userdata(data, packet_size, value);
		break;
	}
	case luacpp::ValueType::TABLE: {
		SEND_LUA_DATA_CHECK_SPACE(2);
		uint8_t type = static_cast<uint8_t>(lua_net_data_type::TABLE);
		luacpp::LuaTable table;
		table.setReference(value.getReference());
		uint8_t size = 0;
		SCP_vector<std::pair<luacpp::LuaValue, luacpp::LuaValue>> dataPairs;
		for (const auto& value_pair : table) {
			//Since we can't rely on getLength / # to get a non-numeric-key length of a table, we need to count what we can actually emplace
			if (++size == 0xff) {
				LuaError(value.getLuaState(), "Tried to send a table with too many keys over the network. Maximum %d supported!", 0xff);
				throw lua_net_exception("Tried to send a table with too many keys over the network.");
			}
			SCP_UNUSED(value_pair);
		}
		ADD_DATA(type);
		ADD_DATA(size);
		for (const auto& value_pair : table) {
			send_lua_data(data, packet_size, value_pair.first);
			send_lua_data(data, packet_size, value_pair.second);
		}
		break;
	}
	default:
		LuaError(value.getLuaState(), "Tried to send an invalid type of lua data over the network. Support are only nil, boolean, number, string, tables and certain FSO userdata!");
		throw lua_net_exception("Tried to send an invalid type of lua data over the network.");
	}
}

#undef SEND_LUA_DATA_CHECK_SPACE
#undef MAX_USERDATA_REQUIRED_ESTIMATE

void process_lua_packet(ubyte* data, header* hinfo, bool reliable) {
	int offset; 
	lua_State* L = Script_system.GetLuaSession();

	offset = HEADER_LENGTH;

	ushort packet_header;
	ushort packet_size;
	
	GET_USHORT(packet_header);
	GET_USHORT(packet_size);
	if ((packet_header & lua_net_bitmask_ordered) != 0) {
		ushort packetTime;
		UI_TIMESTAMP packetLocalTime = ui_timestamp();

		const int timeOffset = offset;
		GET_USHORT(packetTime);

		if (need_toss_packet(packet_header & lua_net_bitmask_rpchash, hinfo->id, packetTime, packetLocalTime)) {
			//If this packet has elapsed, toss it. Don't send it on either.
			hinfo->bytes_processed = packet_size;
			return;
		}

		if (MULTIPLAYER_MASTER) {
			//We MUST replace the time data here, since clients would recieve timestamps from different clients, which aren't comparable
			ushort swap = INTEL_SHORT(static_cast<ushort>(packetLocalTime.value()));
			memcpy(data + timeOffset, &swap, sizeof(swap));
		}
	}

	//Before we keep ourselves busy with any sort of deserialization, check who this packet is for and potentially forward it first.
	//Clients don't need to worry though. Neither will they have to forward, not will they recieve packets not meant for them.
	if (MULTIPLAYER_MASTER) {
		if ((packet_header & lua_net_bitmask_client) != 0) {
			//Need to send to all clients, except the one we got it from.
			if (reliable)
				multi_io_send_to_all_reliable(data, packet_size, &Net_players[find_player_index(hinfo->id)]);
			else
				multi_io_send_to_all(data, packet_size, &Net_players[find_player_index(hinfo->id)]);
		}
		if ((packet_header & lua_net_bitmask_server) == 0) {
			//And it wasn't even meant for the server. Very sad.
			hinfo->bytes_processed = packet_size;
			return; 
		}
	}

	try {
		luacpp::LuaValue value = process_lua_data(data, offset, L);
		
		//Let's find the actual function to call.
		const auto it = rpc_map.find(packet_header & lua_net_bitmask_rpchash);
		if (it == rpc_map.end() || it->second.expired()) {
			//No RPC available. Since, in very rare case, this can be intentional, just log this.
			nprintf(("Network", "Failed to find an RPC handler for packet with hash %#06X.\n", packet_header & lua_net_bitmask_rpchash));
		}
		else {
			const scripting::api::rpc_h rpc_ptr = it->second.lock();
			if (rpc_ptr == nullptr || !rpc_ptr->func.isValid())
				LuaError(L, "Tried to invoke RPC handler %s but the function was not valid.", rpc_ptr->name.c_str());
			else {
				rpc_ptr->func.call(L, luacpp::LuaValueList{ std::move(value) });
				rpc_ptr->lastCalled = ui_timestamp();
			}
		}
	}
	catch (const lua_net_exception& e) {
		offset = packet_size;
		nprintf(("Network", "Failed to decode multi packet.\nReason: %s\nPotentially tossing following packets...\n", e.what()));
	}
	
	Assertion(offset == packet_size, "Lua network packet had bad size! Decoded %d bytes, but was advertised %d bytes!", offset, packet_size);
	PACKET_SET_SIZE();
}

bool send_lua_packet(const luacpp::LuaValue& value, ushort target, lua_net_mode mode, lua_net_reciever reciever) {
	//Sanity check
	if (reciever == lua_net_reciever::SERVER && MULTIPLAYER_MASTER)
		return false;

	int packet_size;
	ubyte data[MAX_PACKET_SIZE];

	BUILD_HEADER(LUA_DATA_PACKET);

	bool isOrdered = mode == lua_net_mode::ORDERED;

	ushort packet_header = 0U;
	packet_header |= target & lua_net_bitmask_rpchash; // : 13
	packet_header |= isOrdered ? lua_net_bitmask_ordered : 0U;
	packet_header |= reciever != lua_net_reciever::SERVER ? lua_net_bitmask_client : 0U;
	packet_header |= reciever != lua_net_reciever::CLIENTS ? lua_net_bitmask_server : 0U;
	ADD_USHORT(packet_header);

	const int size_loc = packet_size;
	ADD_USHORT(static_cast<ushort>(0U));

	if (isOrdered) {
		ushort time = static_cast<ushort>(ui_timestamp().value() & 0xffffU);
		ADD_USHORT(time);
	}

	try {
		send_lua_data(data, packet_size, value);

		ushort swap = INTEL_SHORT(static_cast<ushort>(packet_size));
		memcpy(data + size_loc, &swap, sizeof(swap));

		if (MULTIPLAYER_MASTER) {
			//Due to the sanity check, we're already guaranteed that this must go to all clients
			if (mode == lua_net_mode::RELIABLE)
				multi_io_send_to_all_reliable(data, packet_size);
			else
				multi_io_send_to_all(data, packet_size);
		}
		else {
			//Even if this is just for other clients, it has to be transferred through the server
			if (mode == lua_net_mode::RELIABLE)
				multi_io_send_reliable(Net_player, data, packet_size);
			else
				multi_io_send(Net_player, data, packet_size);
		}

		return true;
	}
	catch (const lua_net_exception& e) {
		nprintf(("Network", "Failed to send multi packet.\nReason: %s..\n", e.what()));
		return false;
	}
}


bool add_rpc(scripting::api::rpc_h_ref ref) {
	//Make sure we don't have an errant RPC hash lying around
	clean_rpc_refs();

	const ushort hash = ref.lock()->hash;

	if (rpc_map.find(hash) != rpc_map.end()) {
		//Something with this hash already exists, bail
		return false;
	}

	rpc_map.emplace(hash, ref);
	return true;
}

void clean_rpc_refs() {
	for (auto it = rpc_map.begin(); it != rpc_map.end();) {
		if (it->second.expired())
			it = rpc_map.erase(it);
		else
			it++;
	}
}