canplayer: ensure 6 decimal places in timestamp for first frame

The check has only been applied after the first CAN frame has been read
and evaluated. This lead to an unintended sending of a single handcrafted
frame with a following (intended) failure at the second frame.

Apply the check also for the very first CAN frame that is processed.

Fixes: ee0233505b ("canplayer: ensure 6 decimal places in timestamp")
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>

canplayer.c

@@ -425,6 +425,15 @@ int main(int argc, char **argv)
 			return 1;
 		}
 
+		/*
+		 * ensure the fractions of seconds are 6 decimal places long to catch
+		 * 3rd party or handcrafted logfiles that treat the timestamp as float
+		 */
+		if (strchr(buf, ')') - strchr(buf, '.') != 7) {
+			fprintf(stderr, "timestamp format in logfile requires 6 decimal places\n");
+			return 1;
+		}
+
 		if (use_timestamps) { /* throttle sending due to logfile timestamps */
 
 			gettimeofday(&today_tv, NULL);