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.

7 files changed, 34 insertions, 16 deletions

diff --git a/src/network/network.cpp b/src/network/network.cpp
index fe7e6a855..e8c99c89b 100644
--- a/src/network/network.cpp
+++ b/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;
 	}
 
diff --git a/src/network/network_client.cpp b/src/network/network_client.cpp
index 08ec7823e..74b802f91 100644
--- a/src/network/network_client.cpp
+++ b/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();
diff --git a/src/network/network_func.h b/src/network/network_func.h
index d4a62ddd3..cbb89820c 100644
--- a/src/network/network_func.h
+++ b/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);
diff --git a/src/network/network_gui.cpp b/src/network/network_gui.cpp
index 2faf5a395..c4488f35d 100644
--- a/src/network/network_gui.cpp
+++ b/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)
diff --git a/src/network/network_server.cpp b/src/network/network_server.cpp
index f68cfd05c..dd88042a1 100644
--- a/src/network/network_server.cpp
+++ b/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++;
 		}
 	}
diff --git a/src/network/network_server.h b/src/network/network_server.h
index 9a1873520..3dfcf5594 100644
--- a/src/network/network_server.h
+++ b/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();
diff --git a/src/network/network_type.h b/src/network/network_type.h
index 595eaad0f..5f796b83d 100644
--- a/src/network/network_type.h
+++ b/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,