Stop hanging when banned

When a banned or connection-limited client attempts to log in, it hangs.

This is because the client does not understand that the server did not finish the handshake. This moves the check to a point just after the handshake has completed (when the server would normally ask for a version number). The client never checked for errors, so added a check.

src/game_initialization/multiplayer.cpp

@@ -158,6 +158,13 @@ std::pair<wesnothd_connection_ptr, config> open_connection(std::string host)
 			std::swap(initial_lobby_config, data);
 		}
 
+		if(data.has_child("error")) {
+			std::string error_message;
+			config* error = &data.child("error");
+			error_message = (*error)["message"].str();
+			throw wesnothd_rejected_client_error(error_message);
+		}
+
 		// Continue if we did not get a direction to login
 		if(!data.has_child("mustlogin")) {
 			continue;

src/game_launcher.cpp

@@ -853,6 +853,8 @@ bool game_launcher::play_multiplayer(mp_selection res)
 			multiplayer_server_.clear();
 		}
 
+	} catch(wesnothd_rejected_client_error& e) {
+		gui2::show_error_message(e.message);
 	} catch(game::mp_server_error& e) {
 		gui2::show_error_message(_("Error while starting server: ") + e.message);
 	} catch(game::load_game_failed& e) {

src/server/server_base.cpp

@@ -78,23 +78,8 @@ void server_base::accept_connection(const boost::system::error_code& error, sock
 		return;
 	}
 
-	const std::string ip = client_address(socket);
-
-	const std::string reason = is_ip_banned(ip);
-	if (!reason.empty()) {
-		LOG_SERVER << ip << "\trejected banned user. Reason: " << reason << "\n";
-		async_send_error(socket, "You are banned. Reason: " + reason);
-		return;
-	} else if (ip_exceeds_connection_limit(ip)) {
-		LOG_SERVER << ip << "\trejected ip due to excessive connections\n";
-		async_send_error(socket, "Too many connections from your IP.");
-		return;
-	} else {
-
-		DBG_SERVER << ip << "\tnew connection accepted\n";
-		serverside_handshake(socket);
-	}
-
+	DBG_SERVER << client_address(socket) << "\tnew connection tentatively accepted\n";
+	serverside_handshake(socket);
 }
 
 void server_base::serverside_handshake(socket_ptr socket)
@@ -118,7 +103,25 @@ void server_base::handle_handshake(const boost::system::error_code& error, socke
 	async_write(
 				*socket, boost::asio::buffer(handshake_response_.buf, 4),
 				[=](const boost::system::error_code& error, size_t)
-					{ if(!check_error(error, socket)) this->handle_new_client(socket); }
+					{
+						if(!check_error(error, socket)) {
+							const std::string ip = client_address(socket);
+
+							const std::string reason = is_ip_banned(ip);
+							if (!reason.empty()) {
+								LOG_SERVER << ip << "\trejected banned user. Reason: " << reason << "\n";
+								async_send_error(socket, "You are banned. Reason: " + reason);
+								return;
+							} else if (ip_exceeds_connection_limit(ip)) {
+								LOG_SERVER << ip << "\trejected ip due to excessive connections\n";
+								async_send_error(socket, "Too many connections from your IP.");
+								return;
+							} else {
+								DBG_SERVER << ip << "\tnew connection fully accepted\n";
+								this->handle_new_client(socket);
+							}
+						}
+					}
 	);
 }
 

src/wesnothd_connection_error.hpp

@@ -23,6 +23,15 @@ struct wesnothd_error : public game::error
 	wesnothd_error(const std::string& error) : game::error(error) {}
 };
 
+/**
+ * Error used when the client is rejected by the MP server.
+ * Technically, this is not an error but the only way to handle the condition is as if it were an error.
+ */
+struct wesnothd_rejected_client_error : public game::error
+{
+    wesnothd_rejected_client_error (const std::string& msg) : game::error (msg) {}
+};
+
 ///We received invalid data from wesnothd during a game
 ///This means we cannot continue with the game but we can stay connected to wesnothd and start a new game
 ///TODO: find a short name