Let mosquitto_ctrl load external modules.

Also provide an example.

apps/mosquitto_ctrl/Makefile

@@ -22,16 +22,21 @@ OBJS=	mosquitto_ctrl.o \
 		options.o \
 		password_mosq.o
 
+EXAMPLE_OBJS= example.o
+
 ifeq ($(WITH_TLS),yes)
 ifeq ($(WITH_CJSON),yes)
-TARGET:=mosquitto_ctrl
+TARGET:=mosquitto_ctrl mosquitto_ctrl_example.so
 endif
 endif
 
 all : $(TARGET)
 
 mosquitto_ctrl : ${OBJS}
-	${CROSS_COMPILE}${CC} ${APP_LDFLAGS} $^ -o $@ $(PASSWD_LDADD) $(LIBMOSQ) -lcjson
+	${CROSS_COMPILE}${CC} ${APP_LDFLAGS} $^ -o $@ $(PASSWD_LDADD) $(LIBMOSQ) -lcjson -ldl
+
+mosquitto_ctrl_example.so : ${EXAMPLE_OBJS}
+	$(CROSS_COMPILE)$(CC) $(PLUGIN_CPPFLAGS) $(PLUGIN_CFLAGS) $(PLUGIN_LDFLAGS) -fPIC -shared $< -o $@
 
 mosquitto_ctrl.o : mosquitto_ctrl.c mosquitto_ctrl.h
 	${CROSS_COMPILE}${CC} $(LOCAL_CPPFLAGS) $(APP_CPPFLAGS) $(APP_CFLAGS) -c $< -o $@
@@ -51,6 +56,9 @@ dynsec_group.o : dynsec_group.c mosquitto_ctrl.h
 dynsec_role.o : dynsec_role.c mosquitto_ctrl.h
 	${CROSS_COMPILE}${CC} $(LOCAL_CPPFLAGS) $(APP_CPPFLAGS) $(APP_CFLAGS) -c $< -o $@
 
+example.o : example.c mosquitto_ctrl.h
+	${CROSS_COMPILE}${CC} $(LOCAL_CPPFLAGS) $(APP_CPPFLAGS) $(APP_CFLAGS) -c $< -o $@
+
 get_password.o : ../mosquitto_passwd/get_password.c ../mosquitto_passwd/get_password.h
 	${CROSS_COMPILE}${CC} $(LOCAL_CPPFLAGS) $(APP_CPPFLAGS) $(APP_CFLAGS) -c $< -o $@
 
@@ -77,7 +85,7 @@ uninstall :
 	-rm -f "${DESTDIR}${prefix}/bin/mosquitto_ctrl"
 
 clean :
-	-rm -f *.o mosquitto_ctrl *.gcda *.gcno
+	-rm -f *.o mosquitto_ctrl *.gcda *.gcno *.so
 
 reallyclean : clean
 	-rm -rf *.orig *.db

apps/mosquitto_ctrl/example.c

@@ -0,0 +1,38 @@
+/*
+Copyright (c) 2020 Roger Light <roger@atchoo.org>
+
+All rights reserved. This program and the accompanying materials
+are made available under the terms of the Eclipse Public License v1.0
+and Eclipse Distribution License v1.0 which accompany this distribution.
+
+The Eclipse Public License is available at
+   http://www.eclipse.org/legal/epl-v10.html
+and the Eclipse Distribution License is available at
+  http://www.eclipse.org/org/documents/edl-v10.php.
+
+Contributors:
+   Roger Light - initial implementation and documentation.
+*/
+#include <cJSON.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "mosquitto_ctrl.h"
+
+void ctrl_help(void)
+{
+	printf("\nExample module\n");
+	printf("==============\n");
+	printf("    mosquitto_ctrl example help\n");
+}
+
+int ctrl_main(int argc, char *argv[], struct mosq_ctrl *ctrl)
+{
+	if(!strcasecmp(argv[0], "help")){
+		ctrl_help();
+		return -1;
+	}else{
+		return MOSQ_ERR_INVAL;
+	}
+}

apps/mosquitto_ctrl/mosquitto_ctrl.c

@@ -22,6 +22,7 @@ Contributors:
 #include <stdlib.h>
 #include <string.h>
 
+#include "lib_load.h"
 #include "mosquitto.h"
 #include "mosquitto_ctrl.h"
 
@@ -47,7 +48,10 @@ void print_usage(void)
 int main(int argc, char *argv[])
 {
 	struct mosq_ctrl ctrl;
-	int rc;
+	int rc = MOSQ_ERR_SUCCESS;
+	FUNC_ctrl_main ctrl_main = NULL;
+	void *lib = NULL;
+	char lib_name[200];
 
 	if(argc == 1){
 		print_usage();
@@ -67,9 +71,25 @@ int main(int argc, char *argv[])
 		print_usage();
 		return 1;
 	}
-
+ 
+	/* In built modules */
 	if(!strcasecmp(argv[0], "dynsec")){
-		rc = dynsec__main(argc-1, &argv[1], &ctrl);
+		ctrl_main = dynsec__main;
+	}else{
+		/* Attempt external module */
+		snprintf(lib_name, sizeof(lib_name), "mosquitto_ctrl_%s.so", argv[0]);
+		lib = LIB_LOAD(lib_name);
+		if(lib){
+			ctrl_main = (FUNC_ctrl_main)LIB_SYM(lib, "ctrl_main");
+			if(ctrl_main == NULL){
+				fprintf(stderr, "Error: Module '%s' not supported.\n", argv[0]);
+				rc = MOSQ_ERR_NOT_SUPPORTED;
+			}
+		}
+	}
+
+	if(ctrl_main){
+		rc = ctrl_main(argc-1, &argv[1], &ctrl);
 		if(rc < 0){
 			/* Usage print */
 			rc = 0;
@@ -80,9 +100,6 @@ int main(int argc, char *argv[])
 		}else{
 			fprintf(stderr, "Error: %s\n", mosquitto_strerror(rc));
 		}
-	}else{
-		fprintf(stderr, "Error: Module '%s' not supported.\n", argv[0]);
-		rc = MOSQ_ERR_NOT_SUPPORTED;
 	}
 
 	client_config_cleanup(&ctrl.cfg);

apps/mosquitto_ctrl/mosquitto_ctrl.h

@@ -73,6 +73,8 @@ struct mosq_ctrl {
 	void *userdata;
 };
 
+typedef int (*FUNC_ctrl_main)(int argc, char *argv[], struct mosq_ctrl *ctrl);
+
 void init_config(struct mosq_config *cfg);
 int ctrl_config_parse(struct mosq_config *cfg, int *argc, char **argv[]);
 int client_config_load(struct mosq_config *cfg);
@@ -109,4 +111,8 @@ int dynsec_role__list_all(int argc, char *argv[], cJSON *j_command);
 int dynsec_role__add_acl(int argc, char *argv[], cJSON *j_command);
 int dynsec_role__remove_acl(int argc, char *argv[], cJSON *j_command);
 
+/* Functions to implement as an external module: */
+void ctrl_help(void);
+int ctrl_main(int argc, char *argv[], struct mosq_ctrl *ctrl);
+
 #endif