Feature: allow the use of TURN to connect client and server together

TURN is a last resort, used only if all other methods failed.
TURN is a relay approach to connect client and server together, where
openttd.org (by default) is the middleman.

It is very unlikely either the client or server cannot connect to
the STUN server, as they are both already connected to the Game
Coordinator. But in the odd case it does fail, estabilishing the
connection fails without any further possibility to recover.

1 files changed, 135 insertions, 0 deletions

diff --git a/src/network/network_turn.cpp b/src/network/network_turn.cpp
new file mode 100644
index 000000000..e04bec47c
--- /dev/null
+++ b/src/network/network_turn.cpp
@@ -0,0 +1,135 @@
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
+ * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file network_turn.cpp TURN sending/receiving part of the network protocol. */
+
+#include "../stdafx.h"
+#include "../debug.h"
+#include "../error.h"
+#include "../strings_func.h"
+#include "network_coordinator.h"
+#include "network_turn.h"
+
+#include "table/strings.h"
+
+#include "../safeguards.h"
+
+/** Connect to the TURN server. */
+class NetworkTurnConnecter : public TCPConnecter {
+private:
+	ClientNetworkTurnSocketHandler *handler;
+
+public:
+	/**
+	 * Initiate the connecting.
+	 * @param connection_string The address of the TURN server.
+	 */
+	NetworkTurnConnecter(ClientNetworkTurnSocketHandler *handler, const std::string &connection_string) : TCPConnecter(connection_string, NETWORK_TURN_SERVER_PORT), handler(handler) {}
+
+	void OnFailure() override
+	{
+		this->handler->connecter = nullptr;
+
+		this->handler->ConnectFailure();
+	}
+
+	void OnConnect(SOCKET s) override
+	{
+		this->handler->connecter = nullptr;
+
+		handler->sock = s;
+	}
+};
+
+bool ClientNetworkTurnSocketHandler::Receive_TURN_ERROR(Packet *p)
+{
+	this->ConnectFailure();
+
+	return false;
+}
+
+bool ClientNetworkTurnSocketHandler::Receive_TURN_CONNECTED(Packet *p)
+{
+	std::string hostname = p->Recv_string(NETWORK_HOSTNAME_LENGTH);
+
+	/* Act like we no longer have a socket, as we are handing it over to the
+	 * game handler. */
+	SOCKET game_sock = this->sock;
+	this->sock = INVALID_SOCKET;
+
+	NetworkAddress address = NetworkAddress(hostname, NETWORK_DEFAULT_PORT);
+	_network_coordinator_client.ConnectSuccess(this->token, game_sock, address);
+
+	return false;
+}
+
+/**
+ * Connect to the TURN server.
+ */
+void ClientNetworkTurnSocketHandler::Connect()
+{
+	this->connect_started = true;
+	this->connecter = new NetworkTurnConnecter(this, this->connection_string);
+}
+
+/**
+ * Prepare a TURN connection.
+ * Not until you run Connect() on the resulting instance will it start setting
+ * up the TURN connection.
+ * @param token The token as received from the Game Coordinator.
+ * @param tracking_number The tracking number as recieved from the Game Coordinator.
+ * @param ticket The ticket as received from the Game Coordinator.
+ * @param connection_string Connection string of the TURN server.
+ * @return The handler for this TURN connection.
+ */
+/* static */ std::unique_ptr<ClientNetworkTurnSocketHandler> ClientNetworkTurnSocketHandler::Turn(const std::string &token, uint8 tracking_number, const std::string &ticket, const std::string &connection_string)
+{
+	auto turn_handler = std::make_unique<ClientNetworkTurnSocketHandler>(token, tracking_number, connection_string);
+
+	Packet *p = new Packet(PACKET_TURN_SERCLI_CONNECT);
+	p->Send_uint8(NETWORK_COORDINATOR_VERSION);
+	p->Send_string(ticket);
+
+	turn_handler->SendPacket(p);
+
+	return turn_handler;
+}
+
+void ClientNetworkTurnSocketHandler::ConnectFailure()
+{
+	_network_coordinator_client.ConnectFailure(this->token, this->tracking_number);
+}
+
+NetworkRecvStatus ClientNetworkTurnSocketHandler::CloseConnection(bool error)
+{
+	NetworkTurnSocketHandler::CloseConnection(error);
+
+	/* If our connecter is still pending, shut it down too. Otherwise the
+	 * callback of the connecter can call into us, and our object is most
+	 * likely about to be destroyed. */
+	if (this->connecter != nullptr) {
+		this->connecter->Kill();
+		this->connecter = nullptr;
+	}
+
+	return NETWORK_RECV_STATUS_OKAY;
+}
+
+/**
+ * Check whether we received/can send some data from/to the TURN server and
+ * when that's the case handle it appropriately
+ */
+void ClientNetworkTurnSocketHandler::SendReceive()
+{
+	if (this->sock == INVALID_SOCKET) return;
+
+	if (this->CanSendReceive()) {
+		this->ReceivePackets();
+	}
+
+	this->SendPackets();
+}