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

This method doesn't require port-forwarding to be used, and works for
most common NAT routers in home setups. But, for sure it doesn't work
for all setups, and not everyone will be able to use this.

1 files changed, 13 insertions, 1 deletions

diff --git a/src/network/network_coordinator.h b/src/network/network_coordinator.h
index f846958bf..9dd4c9b39 100644
--- a/src/network/network_coordinator.h
+++ b/src/network/network_coordinator.h
@@ -11,6 +11,7 @@
 #define NETWORK_COORDINATOR_H
 
 #include "core/tcp_coordinator.h"
+#include "network_stun.h"
 #include <map>
 
 /**
@@ -33,6 +34,12 @@
  *        - Send the client a GC_CONNECT with the peer address.
  *        - a) Client connects, client sends CLIENT_CONNECTED to Game Coordinator.
  *        - b) Client connect fails, client sends CLIENT_CONNECT_FAILED to Game Coordinator.
+ *    2) STUN? (see https://en.wikipedia.org/wiki/STUN)
+ *        - Game Coordinator sends GC_STUN_REQUEST to server/client (asking for both IPv4 and IPv6 STUN requests).
+ *        - Game Coordinator collects what combination works and sends GC_STUN_CONNECT to server/client.
+ *        - a) Server/client connect, client sends CLIENT_CONNECTED to Game Coordinator.
+ *        - b) Server/client connect fails, both send SERCLI_CONNECT_FAILED to Game Coordinator.
+ *        - Game Coordinator tries other combination if available.
  *  - If all fails, Game Coordinator sends GC_CONNECT_FAILED to indicate no connection is possible.
  */
 
@@ -42,6 +49,7 @@ private:
 	std::chrono::steady_clock::time_point next_update; ///< When to send the next update (if server and public).
 	std::map<std::string, TCPServerConnecter *> connecter; ///< Based on tokens, the current connecters that are pending.
 	std::map<std::string, TCPServerConnecter *> connecter_pre; ///< Based on invite codes, the current connecters that are pending.
+	std::map<std::string, std::map<int, std::unique_ptr<ClientNetworkStunSocketHandler>>> stun_handlers; ///< All pending STUN handlers, stored by token:family.
 	TCPConnecter *game_connecter = nullptr; ///< Pending connecter to the game server.
 
 protected:
@@ -51,6 +59,8 @@ protected:
 	bool Receive_GC_CONNECTING(Packet *p) override;
 	bool Receive_GC_CONNECT_FAILED(Packet *p) override;
 	bool Receive_GC_DIRECT_CONNECT(Packet *p) override;
+	bool Receive_GC_STUN_REQUEST(Packet *p) override;
+	bool Receive_GC_STUN_CONNECT(Packet *p) override;
 
 public:
 	/** The idle timeout; when to close the connection because it's idle. */
@@ -65,11 +75,13 @@ public:
 	void SendReceive();
 
 	void ConnectFailure(const std::string &token, uint8 tracking_number);
-	void ConnectSuccess(const std::string &token, SOCKET sock);
+	void ConnectSuccess(const std::string &token, SOCKET sock, NetworkAddress &address);
+	void StunResult(const std::string &token, uint8 family, bool result);
 
 	void Connect();
 	void CloseToken(const std::string &token);
 	void CloseAllTokens();
+	void CloseStunHandler(const std::string &token, uint8 family = AF_UNSPEC);
 
 	void Register();
 	void SendServerUpdate();