Feature #7756: Allow server to supply a reason to kicked/banned clients

This commit adds the missing feature of allowing the server owner to
    provide a reason for kicking/banning a client, which the client sees in
    a pop-up window after being kicked. The implementation extends the
    network protocol by adding a new network action called
    NETWORK_ACTION_KICKED that is capable of having an error string, unlike
    the other network error packages.  Additionally, the kick function
    broadcasts a message to all clients about the kicked client and the
    reason for the kick.

src/console_cmds.cpp

@@ -470,7 +470,7 @@ DEF_CONSOLE_CMD(ConClearBuffer)
  * Network Core Console Commands
  **********************************/
 
-static bool ConKickOrBan(const char *argv, bool ban)
+static bool ConKickOrBan(const char *argv, bool ban, const char *reason)
 {
 	uint n;
 
@@ -494,14 +494,14 @@ static bool ConKickOrBan(const char *argv, bool ban)
 
 		if (!ban) {
 			/* Kick only this client, not all clients with that IP */
-			NetworkServerKickClient(client_id);
+			NetworkServerKickClient(client_id, reason);
 			return true;
 		}
 
 		/* When banning, kick+ban all clients with that IP */
-		n = NetworkServerKickOrBanIP(client_id, ban);
+		n = NetworkServerKickOrBanIP(client_id, ban, reason);
 	} else {
-		n = NetworkServerKickOrBanIP(argv, ban);
+		n = NetworkServerKickOrBanIP(argv, ban, reason);
 	}
 
 	if (n == 0) {
@@ -516,28 +516,48 @@ static bool ConKickOrBan(const char *argv, bool ban)
 DEF_CONSOLE_CMD(ConKick)
 {
 	if (argc == 0) {
-		IConsoleHelp("Kick a client from a network game. Usage: 'kick <ip | client-id>'");
+		IConsoleHelp("Kick a client from a network game. Usage: 'kick <ip | client-id> [<kick-reason>]'");
 		IConsoleHelp("For client-id's, see the command 'clients'");
 		return true;
 	}
 
-	if (argc != 2) return false;
+	if (argc != 2 && argc != 3) return false;
+
+	/* No reason supplied for kicking */
+	if (argc == 2) return ConKickOrBan(argv[1], false, nullptr);
 
-	return ConKickOrBan(argv[1], false);
+	/* Reason for kicking supplied */
+	int kick_message_length = strlen(argv[2]);
+	if (kick_message_length >= 255) {
+		IConsolePrintF(CC_ERROR, "ERROR: Maximum kick message length is 254 characters. You entered %d characters.", kick_message_length);
+		return false;
+	} else {
+		return ConKickOrBan(argv[1], false, argv[2]);
+	}
 }
 
 DEF_CONSOLE_CMD(ConBan)
 {
 	if (argc == 0) {
-		IConsoleHelp("Ban a client from a network game. Usage: 'ban <ip | client-id>'");
+		IConsoleHelp("Ban a client from a network game. Usage: 'ban <ip | client-id> [<ban-reason>]'");
 		IConsoleHelp("For client-id's, see the command 'clients'");
 		IConsoleHelp("If the client is no longer online, you can still ban his/her IP");
 		return true;
 	}
 
-	if (argc != 2) return false;
+	if (argc != 2 && argc != 3) return false;
+
+	/* No reason supplied for kicking */
+	if (argc == 2) return ConKickOrBan(argv[1], true, nullptr);
 
-	return ConKickOrBan(argv[1], true);
+	/* Reason for kicking supplied */
+	int kick_message_length = strlen(argv[2]);
+	if (kick_message_length >= 255) {
+		IConsolePrintF(CC_ERROR, "ERROR: Maximum kick message length is 254 characters. You entered %d characters.", kick_message_length);
+		return false;
+	} else {
+		return ConKickOrBan(argv[1], true, argv[2]);
+	}
 }
 
 DEF_CONSOLE_CMD(ConUnBan)

src/lang/english.txt

@@ -2168,6 +2168,7 @@ STR_NETWORK_ERROR_WRONG_PASSWORD                                :{WHITE}Wrong pa
 STR_NETWORK_ERROR_SERVER_FULL                                   :{WHITE}The server is full
 STR_NETWORK_ERROR_SERVER_BANNED                                 :{WHITE}You are banned from this server
 STR_NETWORK_ERROR_KICKED                                        :{WHITE}You were kicked out of the game
+STR_NETWORK_ERROR_KICK_MESSAGE                                  :{WHITE}Reason: {RAW_STRING}
 STR_NETWORK_ERROR_CHEATER                                       :{WHITE}Cheating is not allowed on this server
 STR_NETWORK_ERROR_TOO_MANY_COMMANDS                             :{WHITE}You were sending too many commands to the server
 STR_NETWORK_ERROR_TIMEOUT_PASSWORD                              :{WHITE}You took too long to enter the password
@@ -2227,6 +2228,7 @@ STR_NETWORK_MESSAGE_GIVE_MONEY                                  :*** {RAW_STRING
 STR_NETWORK_MESSAGE_GAVE_MONEY_AWAY                             :*** You gave {1:RAW_STRING} {2:CURRENCY_LONG}
 STR_NETWORK_MESSAGE_SERVER_SHUTDOWN                             :{WHITE}The server closed the session
 STR_NETWORK_MESSAGE_SERVER_REBOOT                               :{WHITE}The server is restarting...{}Please wait...
+STR_NETWORK_MESSAGE_KICKED                                      :*** {RAW_STRING} was kicked. Reason: ({RAW_STRING})
 
 # Content downloading window
 STR_CONTENT_TITLE                                               :{WHITE}Content downloading

src/network/network.cpp

@@ -248,6 +248,7 @@ void NetworkTextMessage(NetworkAction action, TextColour colour, bool self_send,
 		case NETWORK_ACTION_GIVE_MONEY:     strid = self_send ? STR_NETWORK_MESSAGE_GAVE_MONEY_AWAY : STR_NETWORK_MESSAGE_GIVE_MONEY;   break;
 		case NETWORK_ACTION_CHAT_COMPANY:   strid = self_send ? STR_NETWORK_CHAT_TO_COMPANY : STR_NETWORK_CHAT_COMPANY; break;
 		case NETWORK_ACTION_CHAT_CLIENT:    strid = self_send ? STR_NETWORK_CHAT_TO_CLIENT  : STR_NETWORK_CHAT_CLIENT;  break;
+		case NETWORK_ACTION_KICKED:         strid = STR_NETWORK_MESSAGE_KICKED; break;
 		default:                            strid = STR_NETWORK_CHAT_ALL; break;
 	}
 

src/network/network_client.cpp

@@ -687,8 +687,15 @@ NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_ERROR(Packet *p
 
 	StringID err = STR_NETWORK_ERROR_LOSTCONNECTION;
 	if (error < (ptrdiff_t)lengthof(network_error_strings)) err = network_error_strings[error];
-
-	ShowErrorMessage(err, INVALID_STRING_ID, WL_CRITICAL);
+	/* In case of kicking a client, we assume there is a kick message in the packet if we can read one byte */
+	if (error == NETWORK_ERROR_KICKED && p->CanReadFromPacket(1)) {
+		char kick_msg[255];
+		p->Recv_string(kick_msg, sizeof(kick_msg));
+		SetDParamStr(0, kick_msg);
+		ShowErrorMessage(err, STR_NETWORK_ERROR_KICK_MESSAGE, WL_CRITICAL);
+	} else {
+		ShowErrorMessage(err, INVALID_STRING_ID, WL_CRITICAL);
+	}
 
 	/* Perform an emergency save if we had already entered the game */
 	if (this->status == STATUS_ACTIVE) ClientNetworkEmergencySave();

src/network/network_func.h

@@ -75,9 +75,9 @@ void NetworkServerDoMove(ClientID client_id, CompanyID company_id);
 void NetworkServerSendRcon(ClientID client_id, TextColour colour_code, const char *string);
 void NetworkServerSendChat(NetworkAction action, DestType type, int dest, const char *msg, ClientID from_id, int64 data = 0, bool from_admin = false);
 
-void NetworkServerKickClient(ClientID client_id);
-uint NetworkServerKickOrBanIP(ClientID client_id, bool ban);
-uint NetworkServerKickOrBanIP(const char *ip, bool ban);
+void NetworkServerKickClient(ClientID client_id, const char *reason);
+uint NetworkServerKickOrBanIP(ClientID client_id, bool ban, const char *reason);
+uint NetworkServerKickOrBanIP(const char *ip, bool ban, const char *reason);
 
 void NetworkInitChatMessage();
 void CDECL NetworkAddChatMessage(TextColour colour, uint duration, const char *message, ...) WARN_FORMAT(3, 4);

src/network/network_gui.cpp

@@ -1687,12 +1687,12 @@ static WindowDesc _client_list_popup_desc(
 /* Here we start to define the options out of the menu */
 static void ClientList_Kick(const NetworkClientInfo *ci)
 {
-	NetworkServerKickClient(ci->client_id);
+	NetworkServerKickClient(ci->client_id, nullptr);
 }
 
 static void ClientList_Ban(const NetworkClientInfo *ci)
 {
-	NetworkServerKickOrBanIP(ci->client_id, true);
+	NetworkServerKickOrBanIP(ci->client_id, true, nullptr);
 }
 
 static void ClientList_GiveMoney(const NetworkClientInfo *ci)

src/network/network_server.cpp

@@ -407,13 +407,15 @@ NetworkRecvStatus ServerNetworkGameSocketHandler::SendCompanyInfo()
 /**
  * Send an error to the client, and close its connection.
  * @param error The error to disconnect for.
+ * @param reason In case of kicking a client, specifies the reason for kicking the client.
  */
-NetworkRecvStatus ServerNetworkGameSocketHandler::SendError(NetworkErrorCode error)
+NetworkRecvStatus ServerNetworkGameSocketHandler::SendError(NetworkErrorCode error, const char *reason)
 {
 	char str[100];
 	Packet *p = new Packet(PACKET_SERVER_ERROR);
 
 	p->Send_uint8(error);
+	if (reason != nullptr) p->Send_string(reason);
 	this->SendPacket(p);
 
 	StringID strid = GetNetworkErrorMsg(error);
@@ -427,7 +429,11 @@ NetworkRecvStatus ServerNetworkGameSocketHandler::SendError(NetworkErrorCode err
 
 		DEBUG(net, 1, "'%s' made an error and has been disconnected. Reason: '%s'", client_name, str);
 
-		NetworkTextMessage(NETWORK_ACTION_LEAVE, CC_DEFAULT, false, client_name, nullptr, strid);
+		if (error == NETWORK_ERROR_KICKED && reason != nullptr) {
+			NetworkTextMessage(NETWORK_ACTION_KICKED, CC_DEFAULT, false, client_name, reason, strid);
+		} else {
+			NetworkTextMessage(NETWORK_ACTION_LEAVE, CC_DEFAULT, false, client_name, nullptr, strid);
+		}
 
 		for (NetworkClientSocket *new_cs : NetworkClientSocket::Iterate()) {
 			if (new_cs->status > STATUS_AUTHORIZED && new_cs != this) {
@@ -2039,29 +2045,32 @@ void NetworkServerSendRcon(ClientID client_id, TextColour colour_code, const cha
 /**
  * Kick a single client.
  * @param client_id The client to kick.
+ * @param reason In case of kicking a client, specifies the reason for kicking the client.
  */
-void NetworkServerKickClient(ClientID client_id)
+void NetworkServerKickClient(ClientID client_id, const char *reason)
 {
 	if (client_id == CLIENT_ID_SERVER) return;
-	NetworkClientSocket::GetByClientID(client_id)->SendError(NETWORK_ERROR_KICKED);
+	NetworkClientSocket::GetByClientID(client_id)->SendError(NETWORK_ERROR_KICKED, reason);
 }
 
 /**
  * Ban, or kick, everyone joined from the given client's IP.
  * @param client_id The client to check for.
  * @param ban Whether to ban or kick.
+ * @param reason In case of kicking a client, specifies the reason for kicking the client.
  */
-uint NetworkServerKickOrBanIP(ClientID client_id, bool ban)
+uint NetworkServerKickOrBanIP(ClientID client_id, bool ban, const char *reason)
 {
-	return NetworkServerKickOrBanIP(NetworkClientSocket::GetByClientID(client_id)->GetClientIP(), ban);
+	return NetworkServerKickOrBanIP(NetworkClientSocket::GetByClientID(client_id)->GetClientIP(), ban, reason);
 }
 
 /**
  * Kick or ban someone based on an IP address.
  * @param ip The IP address/range to ban/kick.
  * @param ban Whether to ban or just kick.
+ * @param reason In case of kicking a client, specifies the reason for kicking the client.
  */
-uint NetworkServerKickOrBanIP(const char *ip, bool ban)
+uint NetworkServerKickOrBanIP(const char *ip, bool ban, const char *reason)
 {
 	/* Add address to ban-list */
 	if (ban) {
@@ -2081,7 +2090,7 @@ uint NetworkServerKickOrBanIP(const char *ip, bool ban)
 	for (NetworkClientSocket *cs : NetworkClientSocket::Iterate()) {
 		if (cs->client_id == CLIENT_ID_SERVER) continue;
 		if (cs->client_address.IsInNetmask(ip)) {
-			NetworkServerKickClient(cs->client_id);
+			NetworkServerKickClient(cs->client_id, reason);
 			n++;
 		}
 	}

src/network/network_server.h

@@ -89,7 +89,7 @@ public:
 	NetworkRecvStatus SendMove(ClientID client_id, CompanyID company_id);
 
 	NetworkRecvStatus SendClientInfo(NetworkClientInfo *ci);
-	NetworkRecvStatus SendError(NetworkErrorCode error);
+	NetworkRecvStatus SendError(NetworkErrorCode error, const char *reason = nullptr);
 	NetworkRecvStatus SendChat(NetworkAction action, ClientID client_id, bool self_send, const char *msg, int64 data);
 	NetworkRecvStatus SendJoin(ClientID client_id);
 	NetworkRecvStatus SendFrame();

src/network/network_type.h

@@ -85,6 +85,7 @@ enum DestType {
 enum NetworkAction {
 	NETWORK_ACTION_JOIN,
 	NETWORK_ACTION_LEAVE,
+	NETWORK_ACTION_KICKED,
 	NETWORK_ACTION_SERVER_MESSAGE,
 	NETWORK_ACTION_CHAT,
 	NETWORK_ACTION_CHAT_COMPANY,