DLT logging is now configurable at runtime with log_dest dlt.

Closes #1735. Thanks to Brian Orpin.

ChangeLog.txt

@@ -10,6 +10,8 @@ Broker:
   being false.
 - Allow MQTT v5.0 outgoing bridges to fall back to MQTT v3.1.1 if connecting
   to a v3.x only broker.
+- DLT logging is now configurable at runtime with `log_dest dlt`.
+  Closes #1735.
 
 Client library:
 - Client no longer generates random client ids for v3.1.1 clients, these are

man/mosquitto.conf.5.xml

@@ -458,7 +458,8 @@ D.conf
 					<para>Send log messages to a particular destination.
 						Possible destinations are: <option>stdout</option>
 						<option>stderr</option> <option>syslog</option>
-						<option>topic</option>.</para>
+						<option>topic</option> <option>file</option> 
+						<option>dlt</option>.</para>
 					<para><option>stdout</option> and
 						<option>stderr</option> log to the console on the
 						named output.</para>
@@ -478,6 +479,10 @@ D.conf
 						will be closed and reopened when the broker receives a
 						HUP signal. Only a single file destination may be
 						configured.</para>
+					<para>The <option>dlt</option> destination is for the
+						automotive `Diagnostic Log and Trace` tool. This
+						requires that Mosquitto has been compiled with DLT
+						support.</para>
 					<para>Use "log_dest none" if you wish to disable logging.
 						Defaults to stderr. This option may be specified
 						multiple times.</para>

mosquitto.conf

@@ -586,7 +586,7 @@
 
 # Places to log to. Use multiple log_dest lines for multiple
 # logging destinations.
-# Possible destinations are: stdout stderr syslog topic file
+# Possible destinations are: stdout stderr syslog topic file dlt
 #
 # stdout and stderr log to the console on the named output.
 #
@@ -604,6 +604,9 @@
 # closed and reopened when the broker receives a HUP signal. Only a single file
 # destination may be configured.
 #
+# The dlt destination is for the automotive `Diagnostic Log and Trace` tool.
+# This requires that Mosquitto has been compiled with DLT support.
+#
 # Note that if the broker is running as a Windows service it will default to
 # "log_dest none" and neither stdout nor stderr logging is available.
 # Use "log_dest none" if you wish to disable logging.

src/conf.c

@@ -177,7 +177,7 @@ static void config__init_reload(struct mosquitto_db *db, struct mosquitto__confi
 	}
 #else
 	config->log_facility = LOG_DAEMON;
-	config->log_dest = MQTT3_LOG_STDERR;
+	config->log_dest = MQTT3_LOG_STDERR | MQTT3_LOG_DLT;
 	if(db->verbose){
 		config->log_type = UINT_MAX;
 	}else{
@@ -1511,6 +1511,8 @@ int config__read_file_core(struct mosquitto__config *config, bool reload, struct
 							cr->log_dest |= MQTT3_LOG_STDERR;
 						}else if(!strcmp(token, "topic")){
 							cr->log_dest |= MQTT3_LOG_TOPIC;
+						}else if(!strcmp(token, "dlt")){
+							cr->log_dest |= MQTT3_LOG_DLT;
 						}else if(!strcmp(token, "file")){
 							cr->log_dest |= MQTT3_LOG_FILE;
 							if(config->log_fptr || config->log_file){

src/logging.c

@@ -119,8 +119,10 @@ int log__init(struct mosquitto__config *config)
 		restore_privileges();
 	}
 #ifdef WITH_DLT
-	DLT_REGISTER_APP("MQTT","mosquitto log");
-	dlt_register_context(&dltContext, "MQTT", "mosquitto DLT context");
+	if(log_destinations & MQTT3_LOG_DLT){
+		DLT_REGISTER_APP("MQTT","mosquitto log");
+		dlt_register_context(&dltContext, "MQTT", "mosquitto DLT context");
+	}
 #endif
 	return rc;
 }
@@ -142,8 +144,10 @@ int log__close(struct mosquitto__config *config)
 	}
 
 #ifdef WITH_DLT
-	dlt_unregister_context(&dltContext);
-	DLT_UNREGISTER_APP();
+	if(log_destinations & MQTT3_LOG_DLT){
+		dlt_unregister_context(&dltContext);
+		DLT_UNREGISTER_APP();
+	}
 #endif
 	/* FIXME - do something for all destinations! */
 	return MOSQ_ERR_SUCCESS;
@@ -347,7 +351,7 @@ int log__vprintf(int priority, const char *fmt, va_list va)
 			}
 		}
 #ifdef WITH_DLT
-		if(priority != MOSQ_LOG_INTERNAL){
+		if(log_destinations & MQTT3_LOG_DLT && priority != MOSQ_LOG_INTERNAL){
 			DLT_LOG_STRING(dltContext, get_dlt_level(priority), s);
 		}
 #endif

src/mosquitto_broker_internal.h

@@ -70,6 +70,7 @@ Contributors:
 #define MQTT3_LOG_STDOUT 0x04
 #define MQTT3_LOG_STDERR 0x08
 #define MQTT3_LOG_TOPIC 0x10
+#define MQTT3_LOG_DLT 0x20
 #define MQTT3_LOG_ALL 0xFF
 
 #define WEBSOCKET_CLIENT -2