X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Futil%2Ftime.rs;h=a6e6f4d1fda6b6e58a102a0baeb97cbed102159f;hb=3eb61f7e9b55531626936cf84c57cd7530a878a4;hp=d3768aa7ca6441d2943c5ac080e57113ab9d957d;hpb=b20aea1cb0fb9f19c646e96518ef9845e6593264;p=rust-lightning

diff --git a/lightning/src/util/time.rs b/lightning/src/util/time.rs
index d3768aa7..a6e6f4d1 100644
--- a/lightning/src/util/time.rs
+++ b/lightning/src/util/time.rs
@@ -58,22 +58,48 @@ impl Sub<Duration> for Eternity {
 	}
 }
 
-#[cfg(not(feature = "no-std"))]
-impl Time for std::time::Instant {
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+#[cfg(feature = "std")]
+pub struct MonotonicTime(std::time::Instant);
+
+/// The amount of time to shift `Instant` forward to prevent overflow when subtracting a `Duration`
+/// from `Instant::now` on some operating systems (e.g., iOS representing `Instance` as `u64`).
+#[cfg(feature = "std")]
+const SHIFT: Duration = Duration::from_secs(10 * 365 * 24 * 60 * 60); // 10 years.
+
+#[cfg(feature = "std")]
+impl Time for MonotonicTime {
 	fn now() -> Self {
-		std::time::Instant::now()
+		let instant = std::time::Instant::now().checked_add(SHIFT).expect("Overflow on MonotonicTime instantiation");
+		Self(instant)
 	}
 
 	fn duration_since(&self, earlier: Self) -> Duration {
-		self.duration_since(earlier)
+		// On rust prior to 1.60 `Instant::duration_since` will panic if time goes backwards.
+		// However, we support rust versions prior to 1.60 and some users appear to have "monotonic
+		// clocks" that go backwards in practice (likely relatively ancient kernels/etc). Thus, we
+		// manually check for time going backwards here and return a duration of zero in that case.
+		let now = Self::now();
+		if now.0 > earlier.0 { now.0 - earlier.0 } else { Duration::from_secs(0) }
 	}
 
 	fn duration_since_epoch() -> Duration {
 		use std::time::SystemTime;
 		SystemTime::now().duration_since(SystemTime::UNIX_EPOCH).unwrap()
 	}
+
 	fn elapsed(&self) -> Duration {
-		std::time::Instant::elapsed(self)
+		Self::now().0 - self.0
+	}
+}
+
+#[cfg(feature = "std")]
+impl Sub<Duration> for MonotonicTime {
+	type Output = Self;
+
+	fn sub(self, other: Duration) -> Self {
+		let instant = self.0.checked_sub(other).expect("MonotonicTime is not supposed to go backward futher than 10 years");
+		Self(instant)
 	}
 }
 
@@ -149,4 +175,15 @@ pub mod tests {
 		assert_eq!(now.elapsed(), Duration::from_secs(0));
 		assert_eq!(later - elapsed, now);
 	}
+
+	#[test]
+	#[cfg(feature = "std")]
+	fn monotonic_time_subtracts() {
+		let now = super::MonotonicTime::now();
+		assert!(now.elapsed() < Duration::from_secs(10));
+
+		let ten_years = Duration::from_secs(10 * 365 * 24 * 60 * 60);
+		let past = now - ten_years;
+		assert!(past.elapsed() >= ten_years);
+	}
 }