fix #3532 : oos error in mp campaigns.

previously it would cause oos when a player that has not yet advanced to
the currrent scenario sends random seed requests.

(cherry-picked from commit d0c0f406f2)

src/server/game.cpp

@@ -117,6 +117,7 @@ game::game(player_connections& player_connections,
 	, num_turns_(0)
 	, all_observers_muted_(false)
 	, bans_()
+	, players_not_advanced_()
 	, termination_()
 	, save_replays_(save_replays)
 	, replay_save_path_(replay_save_path)
@@ -1228,16 +1229,24 @@ void game::handle_controller_choice(const simple_wml::node& req)
 
 void game::handle_choice(const simple_wml::node& data, const socket_ptr& user)
 {
+
+	if(!started_) {
+		return;
+	}
+
 	// note, that during end turn events, it's side=1 for the server but side= side_count() on the clients.
 
 	// Otherwise we allow observers to cause OOS for the playing clients by sending
 	// server choice requests based on incompatible local changes. To solve this we block
 	// server choice requests from observers.
-	if(!started_) {
+	if(user != owner_ && !is_player(user)) {
 		return;
 	}
 
-	if(user != owner_ && !is_player(user)) {
+	// since we reset the last_choice_request_id_ when a new scenario is loaded,
+	// the code would otherwise wrongly accept these requests from client in old
+	// scenarios. which would result on oos.
+	if(players_not_advanced_.find(user) != players_not_advanced_.end()) {
 		return;
 	}
 
@@ -1465,6 +1474,7 @@ bool game::remove_player(const socket_ptr& player, const bool disconnect, const
 
 	players_.erase(std::remove(players_.begin(), players_.end(), player), players_.end());
 	observers_.erase(std::remove(observers_.begin(), observers_.end(), player), observers_.end());
+	players_not_advanced_.erase(player);
 
 	const bool game_ended = players_.empty() || (host && !started_);
 
@@ -1590,6 +1600,17 @@ void game::send_user_list(const socket_ptr& exclude) const
 	send_data(cfg, exclude);
 }
 
+void game::new_scenario(const socket_ptr& sender)
+{
+	assert(sender == owner_);
+	players_not_advanced_.clear();
+	for(const socket_ptr& user_ptr : all_game_users()) {
+		if(user_ptr != sender) {
+			players_not_advanced_.insert(user_ptr);
+		}
+	}
+}
+
 void game::load_next_scenario(const socket_ptr& user)
 {
 	send_server_message_to_all(player_connections_.find(user)->info().name() + " advances to the next scenario", user);
@@ -1633,6 +1654,8 @@ void game::load_next_scenario(const socket_ptr& user)
 	send_to_player(user, cfg_scenario);
 	send_to_player(user, doc_controllers);
 
+	players_not_advanced_.erase(user);
+
 	// Send the player the history of the game to-date.
 	send_history(user);
 

src/server/game.hpp

@@ -77,6 +77,9 @@ public:
 	/** Checks whether the connection's ip address is banned. */
 	bool player_is_banned(const socket_ptr& player) const;
 
+	/** when the host sends the new scenario of a mp campaign */
+	void new_scenario(const socket_ptr& player);
+
 	bool level_init() const
 	{
 		return level_.child("snapshot") || level_.child("scenario");
@@ -500,6 +503,10 @@ private:
 	bool all_observers_muted_;
 
 	std::vector<std::string> bans_;
+	/// in multiplayer campaigns it can happen that some players are still in the previousl scenario
+	/// keep track of those players because processing certain
+	/// input from those side wil lead to error (oos)
+	std::set<socket_ptr> players_not_advanced_;
 
 	std::string termination_;
 

src/server/server.cpp

@@ -1629,6 +1629,7 @@ void server::handle_player_in_game(socket_ptr socket, std::shared_ptr<simple_wml
 			return;
 		}
 
+		g.new_scenario(socket);
 		g.save_replay();
 		g.reset_last_synced_context_id();