Implement Error trait for rotation interval error

2 files changed, 23 insertions, 3 deletions

diff --git a/mullvad-daemon/src/management_interface.rs b/mullvad-daemon/src/management_interface.rs
index a6762e867b..dff318cece 100644
--- a/mullvad-daemon/src/management_interface.rs
+++ b/mullvad-daemon/src/management_interface.rs
@@ -606,9 +606,8 @@ impl ManagementService for ManagementServiceImpl {
         let interval: RotationInterval = Duration::try_from(request.into_inner())
             .map_err(|_| Status::invalid_argument("unexpected negative rotation interval"))?
             .try_into()
-            .map_err(|error| match error {
-                RotationIntervalError::TooSmall => Status::invalid_argument("interval too small"),
-                RotationIntervalError::TooLarge => Status::invalid_argument("interval too large"),
+            .map_err(|error: RotationIntervalError| {
+                Status::invalid_argument(error.display_chain())
             })?;
 
         log::debug!("set_wireguard_rotation_interval({:?})", interval);
diff --git a/mullvad-types/src/wireguard.rs b/mullvad-types/src/wireguard.rs
index 94fc31f29e..cbe05363ec 100644
--- a/mullvad-types/src/wireguard.rs
+++ b/mullvad-types/src/wireguard.rs
@@ -38,6 +38,27 @@ pub enum RotationIntervalError {
     TooLarge,
 }
 
+impl fmt::Display for RotationIntervalError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        use RotationIntervalError::*;
+
+        match *self {
+            TooSmall => write!(
+                f,
+                "Rotation interval must be at least {} hours",
+                MIN_ROTATION_INTERVAL.as_secs() / 60 / 60
+            ),
+            TooLarge => write!(
+                f,
+                "Rotation interval must be at most {} hours",
+                MAX_ROTATION_INTERVAL.as_secs() / 60 / 60
+            ),
+        }
+    }
+}
+
+impl std::error::Error for RotationIntervalError {}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize)]
 pub struct RotationInterval(Duration);