funcs/func_cdr: Correctly report high precision values for duration and billsec

When CDRs were refactored, func_cdr's ability to report high precision values
for duration and billsec (the 'f' option) was broken. This was due to func_cdr
incorrectly interpreting the duration/billsec values provided by the CDR engine
in milliseconds, as opposed to seconds. Since the CDR engine only provides
duration and billsec in seconds, and does not expose either attribute with
sufficient precision to merely pass back the underlying value, this patch fixes
the bug by re-calculating duration and billsec with microsecond precision based
on the start/answer/end times on the CDR.

ASTERISK-25179 #close

Change-Id: I8bc63822b496537a5bf80baf6102c06206bee841

funcs/func_cdr.c

@@ -221,6 +221,26 @@ STASIS_MESSAGE_TYPE_DEFN_LOCAL(cdr_read_message_type);
 STASIS_MESSAGE_TYPE_DEFN_LOCAL(cdr_write_message_type);
 STASIS_MESSAGE_TYPE_DEFN_LOCAL(cdr_prop_write_message_type);
 
+static struct timeval cdr_retrieve_time(struct ast_channel *chan, const char *time_name)
+{
+	struct timeval time;
+	char *value = NULL;
+	char tempbuf[128];
+
+	if (ast_strlen_zero(ast_channel_name(chan))) {
+		/* Format request on a dummy channel */
+		ast_cdr_format_var(ast_channel_cdr(chan), time_name, &value, tempbuf, sizeof(tempbuf), 1);
+	} else {
+		ast_cdr_getvar(ast_channel_name(chan), time_name, tempbuf, sizeof(tempbuf));
+	}
+
+	if (sscanf(tempbuf, "%ld.%ld", &time.tv_sec, &time.tv_usec) != 2) {
+		ast_log(AST_LOG_WARNING, "Failed to fully extract '%s' from CDR\n", time_name);
+	}
+
+	return time;
+}
+
 static void cdr_read_callback(void *data, struct stasis_subscription *sub, struct stasis_message *message)
 {
 	struct cdr_func_payload *payload = stasis_message_data(message);
@@ -268,16 +288,21 @@ static void cdr_read_callback(void *data, struct stasis_subscription *sub, struc
 
 	if (ast_test_flag(&flags, OPT_FLOAT)
 		&& (!strcasecmp("billsec", args.variable) || !strcasecmp("duration", args.variable))) {
-		long ms;
-		double dtime;
+		struct timeval start = cdr_retrieve_time(payload->chan, !strcasecmp("billsec", args.variable) ? "answer" : "start");
+		struct timeval finish = cdr_retrieve_time(payload->chan, "end");
+		double delta;
 
-		if (sscanf(tempbuf, "%30ld", &ms) != 1) {
-			ast_log(AST_LOG_WARNING, "Unable to parse %s (%s) from the CDR for channel %s\n",
-				args.variable, tempbuf, ast_channel_name(payload->chan));
-			return;
+		if (ast_tvzero(finish)) {
+			finish = ast_tvnow();
 		}
-		dtime = (double)(ms / 1000.0);
-		snprintf(tempbuf, sizeof(tempbuf), "%lf", dtime);
+
+		if (ast_tvzero(start)) {
+			delta = 0.0;
+		} else {
+			delta = (double)(ast_tvdiff_us(finish, start) / 1000000.0);
+		}
+		snprintf(tempbuf, sizeof(tempbuf), "%lf", delta);
+
 	} else if (!ast_test_flag(&flags, OPT_UNPARSED)) {
 		if (!strcasecmp("start", args.variable)
 			|| !strcasecmp("end", args.variable)