fix: handle underflow error

src/graphcast_agent/message_typing.rs

@@ -166,17 +166,19 @@ impl<T: RadioPayload> GraphcastMessage<T> {
 
  /// Check timestamp: prevent past message replay
  pub fn valid_time(&self) -> Result<&Self, MessageError> {
- //Can store for measuring overall Graphcast message latency
- let message_age = Utc::now().timestamp() as u64 - self.nonce;
- // 0 allow instant atomic messaging, use 1 to exclude them
- if (0..MSG_REPLAY_LIMIT).contains(&message_age) {
- Ok(self)
- } else {
- Err(MessageError::InvalidFields(anyhow!(
+ let current_time = Utc::now().timestamp();
+ let current_time_u64 = current_time as u64;
+
+ match current_time_u64.checked_sub(self.nonce) {
+ Some(message_age) if (0..MSG_REPLAY_LIMIT).contains(&message_age) => Ok(self),
+ Some(message_age) => Err(MessageError::InvalidFields(anyhow!(
  "Message timestamp {} outside acceptable range {}, drop message",
  message_age,
  MSG_REPLAY_LIMIT
- )))
+ ))),
+ None => Err(MessageError::InvalidFields(anyhow!(
+ "Error calculating message age, possible underflow."
+ ))),
  }
  }