logging: add 'logging timezone (localtime|utc)'

Add ability to print logging timestamps in UTC.

I want to test logging timestamps in vty transcript tests. To get
deterministic timestamps, I can use osmo_gettimeofday_override().
However, so far we log in the server's local time zone: the dates
printed after osmo_gettimeofday_override() still change according to the
locally configured timezone -- not good for regression testing. For UTC,
it is always the same.

The intended use is for regression testing of timestamps, but maybe
logging in UTC may be useful to some user out there, too.

Change-Id: I7f868b47bf8f8dfcf85e735f490ae69b18111af4

configure.ac

@@ -131,6 +131,7 @@ CFLAGS="$saved_CFLAGS"
 AC_SUBST(SYMBOL_VISIBILITY)
 
 AC_CHECK_FUNCS(localtime_r)
+AC_CHECK_FUNCS(gmtime_r)
 
 AC_DEFUN([CHECK_TM_INCLUDES_TM_GMTOFF], [
   AC_CACHE_CHECK(

include/osmocom/core/logging.h

@@ -297,6 +297,11 @@ enum log_filename_pos {
 	LOG_FILENAME_POS_LINE_END,
 };
 
+enum log_timezone {
+	LOG_TIMEZONE_LOCALTIME,
+	LOG_TIMEZONE_UTC,
+};
+
 /*! Format of the timestamp printed */
 enum log_timestamp_format {
 	LOG_TIMESTAMP_NONE,
@@ -411,6 +416,8 @@ struct log_target {
 	/* Where on a log line to put the source file info. */
 	enum log_filename_pos print_filename_pos;
 
+	/* Set timezone for timestamps (if at all enabled) */
+	enum log_timezone timezone;
 	/* Timestamp format */
 	enum log_timestamp_format timestamp_format;
 };
@@ -438,6 +445,7 @@ void log_set_print_extended_timestamp(struct log_target *target, int flag)
 void log_set_print_timestamp(struct log_target *target, int flag)
 	OSMO_DEPRECATED("Use log_set_print_timestamp2(LOG_TIMESTAMP_CTIME) instead");
 void log_set_print_timestamp2(struct log_target *target, enum log_timestamp_format format);
+void log_set_timezone(struct log_target *target, enum log_timezone timezone);
 void log_set_print_tid(struct log_target *target, int);
 void log_set_print_filename(struct log_target *target, int) OSMO_DEPRECATED("Use log_set_print_filename2() instead");
 void log_set_print_filename2(struct log_target *target, enum log_filename_type lft);

src/core/libosmocore.map

@@ -91,6 +91,7 @@ log_set_print_level;
 log_set_print_tid;
 log_set_print_timestamp;
 log_set_use_color;
+log_set_timezone;
 log_target_create;
 log_target_create_file;
 log_target_create_file_stream;

src/core/logging.c

@@ -579,11 +579,20 @@ static const char *const_basename(const char *path)
 static int get_timestamp(struct timeval *tv, struct tm *tm, const struct log_target *target)
 {
 	osmo_gettimeofday(tv, NULL);
+	switch (target->timezone) {
+	case LOG_TIMEZONE_LOCALTIME:
 #ifdef HAVE_LOCALTIME_R
-	return (localtime_r(&tv->tv_sec, tm) != NULL) ? 0 : -1;
-#else
-	return -1;
+		return (localtime_r(&tv->tv_sec, tm) != NULL) ? 0 : -1;
 #endif
+		/* If there is no localtime_r() function, then maybe gmtime_r() is available instead? */
+	case LOG_TIMEZONE_UTC:
+#ifdef HAVE_GMTIME_R
+		return (gmtime_r(&tv->tv_sec, tm) != NULL) ? 0 : -1;
+#endif
+		/* If there is no gmtime_r() function, then print no timestamp. */
+	default:
+		return -1;
+	}
 }
 
 /*! main output formatting function for log lines.
@@ -960,6 +969,15 @@ void log_set_print_timestamp(struct log_target *target, int print_timestamp)
 	log_set_print_timestamp2(target, print_timestamp ? LOG_TIMESTAMP_CTIME : LOG_TIMESTAMP_NONE);
 }
 
+/*! Switch logging timezone between UTC or local time.
+ *  \param[in] target Log target to be affected.
+ *  \param[in] timezone Timezone to set.
+ */
+void log_set_timezone(struct log_target *target, enum log_timezone timezone)
+{
+	target->timezone = timezone;
+}
+
 /*! Use log_set_print_timestamp2(LOG_TIMESTAMP_DATE_PACKED) instead.
  * Enable or disable printing of extended timestamps while logging.
  *  \param[in] target Log target to be affected

src/vty/logging_vty.c

@@ -190,6 +190,22 @@ DEFUN(logging_use_clr,
 	RET_WITH_UNLOCK(CMD_SUCCESS);
 }
 
+DEFUN(logging_timezone,
+      logging_timezone_cmd,
+      "logging timezone (localtime|utc)",
+	LOGGING_STR "Configure time zone for log message timestamping\n"
+	"Log timestamps in the system's local time\n"
+	"Log timestamps in Coordinated Universal Time (UTC)\n")
+{
+	struct log_target *tgt;
+	ACQUIRE_VTY_LOG_TGT_WITH_LOCK(vty, tgt);
+	if (strcmp(argv[0], "utc") == 0)
+		log_set_timezone(tgt, LOG_TIMEZONE_UTC);
+	else
+		log_set_timezone(tgt, LOG_TIMEZONE_LOCALTIME);
+	RET_WITH_UNLOCK(CMD_SUCCESS);
+}
+
 DEFUN_DEPRECATED(logging_timestamp,
       logging_timestamp_cmd,
       "logging timestamp (0|1)",
@@ -1099,6 +1115,16 @@ static int config_write_log_single(struct vty *vty, struct log_target *tgt)
 		vty_out(vty, " logging print timestamp %s%s",
 			log_timestamp_format_name(tgt->timestamp_format), VTY_NEWLINE);
 
+	switch (tgt->timezone) {
+	case LOG_TIMEZONE_UTC:
+		vty_out(vty, " logging timezone utc%s", VTY_NEWLINE);
+		break;
+	default:
+	case LOG_TIMEZONE_LOCALTIME:
+		/* write nothing, since LOG_TIMEZONE_LOCALTIME is the default */
+		break;
+	}
+
 	if (tgt->print_level)
 		vty_out(vty, " logging print level 1%s", VTY_NEWLINE);
 	vty_out(vty, " logging print file %s%s%s",
@@ -1243,6 +1269,7 @@ void logging_vty_add_cmds(void)
 	install_lib_element_ve(&logging_timestamp_cmd);
 	install_lib_element_ve(&logging_prnt_timestamp_cmd);
 	install_lib_element_ve(&logging_prnt_ext_timestamp_cmd);
+	install_lib_element_ve(&logging_timezone_cmd);
 	install_lib_element_ve(&logging_prnt_tid_cmd);
 	install_lib_element_ve(&logging_prnt_cat_cmd);
 	install_lib_element_ve(&logging_prnt_cat_hex_cmd);
@@ -1279,6 +1306,7 @@ void logging_vty_add_cmds(void)
 	install_lib_element(CFG_LOG_NODE, &logging_timestamp_cmd);
 	install_lib_element(CFG_LOG_NODE, &logging_prnt_timestamp_cmd);
 	install_lib_element(CFG_LOG_NODE, &logging_prnt_ext_timestamp_cmd);
+	install_lib_element(CFG_LOG_NODE, &logging_timezone_cmd);
 	install_lib_element(CFG_LOG_NODE, &logging_prnt_tid_cmd);
 	install_lib_element(CFG_LOG_NODE, &logging_prnt_cat_cmd);
 	install_lib_element(CFG_LOG_NODE, &logging_prnt_cat_hex_cmd);

tests/logging/logging_vty_test.vty

@@ -47,6 +47,7 @@ logging_vty_test# list
   logging filter all (0|1)
   logging color (0|1)
   logging print timestamp (none|date|date-packed|ctime)
+  logging timezone (localtime|utc)
   logging print thread-id (0|1)
   logging print category (0|1)
   logging print category-hex (0|1)
@@ -65,6 +66,7 @@ logging_vty_test# logging ?
   filter        Filter log messages
   color         Configure color-printing for log messages
   print         Log output settings
+  timezone      Configure time zone for log message timestamping
   set-log-mask  Set the logmask of this logging target
   level         Set the log level for a specified category
 
@@ -72,6 +74,10 @@ logging_vty_test# ### Deprecated command's doc not shown
 logging_vty_test# logging timestamp ?
 % There is no matched command.
 
+logging_vty_test# logging timezone ?
+  localtime  Log timestamps in the system's local time
+  utc        Log timestamps in Coordinated Universal Time (UTC)
+
 logging_vty_test# logging level ?
 ... ! all
   aa         Antropomorphic Armadillos (AA)
@@ -155,6 +161,24 @@ logging_vty_test# logging print file basename ?
 
 logging_vty_test# configure terminal
 logging_vty_test(config)# log stderr
+
+logging_vty_test(config-log)# show running-config
+...
+log stderr
+... !logging timezone
+logging_vty_test(config-log)# logging timezone utc
+logging_vty_test(config-log)# show running-config
+...
+log stderr
+... !logging timezone
+ logging timezone utc
+... !logging timezone
+logging_vty_test(config-log)# logging timezone localtime
+logging_vty_test(config-log)# show running-config
+...
+log stderr
+... !logging timezone
+
 logging_vty_test(config-log)# show running-config
 ...
 log stderr