grumbles: err when max_time & max_threshold fails

ethcore/src/verification/verification.rs

@@ -304,21 +304,27 @@ pub fn verify_header_params(header: &Header, engine: &EthEngine, is_full: bool,
 
 	if is_full {
 		const ACCEPTABLE_DRIFT: Duration = Duration::from_secs(15);
-		// this will resist overflow until `year 2037`
 		let now = SystemTime::now();
 		let now = now.duration_since(UNIX_EPOCH).expect("now is after UNIX_EPOCH; qed");
-		let max_time = now.checked_add(ACCEPTABLE_DRIFT)
-			.unwrap_or(Duration::from_secs(u64::max_value()));
-		let invalid_threshold = max_time.checked_add(ACCEPTABLE_DRIFT * 9)
-			.unwrap_or(Duration::from_secs(u64::max_value()));
+		let max_time = now.checked_add(ACCEPTABLE_DRIFT);
+		let invalid_threshold = max_time.and_then(|t| t.checked_add(ACCEPTABLE_DRIFT * 9));
 		let timestamp = Duration::from_secs(header.timestamp());
 
-		if timestamp > invalid_threshold {
-			return Err(From::from(BlockError::InvalidTimestamp(OutOfBounds { max: Some(max_time), min: None, found: timestamp }.into())))
+		// System clock is unreliable or `year 2037` or later has been reached
+		if invalid_threshold.is_none() && max_time.is_none() {
+			return Err(From::from(BlockError::TimestampOverflow))
+		}
+
+		if let Some(invalid) = invalid_threshold {
+			if timestamp > invalid {
+				return Err(From::from(BlockError::InvalidTimestamp(OutOfBounds { max: max_time, min: None, found: timestamp }.into())))
+			}
 		}
 
-		if timestamp > max_time {
-			return Err(From::from(BlockError::TemporarilyInvalid(OutOfBounds { max: Some(max_time), min: None, found: timestamp }.into())))
+		if let Some(max) = max_time {
+			if timestamp > max {
+				return Err(From::from(BlockError::TemporarilyInvalid(OutOfBounds { max: max_time, min: None, found: timestamp }.into())))
+			}
 		}
 	}