Implement backups, commit and restoration

src/domain.rs

@@ -211,6 +211,25 @@ impl ClientStates {
         &self.reserved_addresses
     }
 
+    /// Restore conservative reservations from saved metadata without asserting
+    /// that the running interface matches the saved snapshot.
+    pub fn restore_persisted_reservations(
+        &mut self,
+        reservations: impl IntoIterator<Item = IpAddr>,
+    ) -> Result<(), DomainError> {
+        let reservations = reservations.into_iter().collect::<BTreeSet<_>>();
+        if reservations
+            .iter()
+            .any(|address| self.saved.addresses().any(|saved| saved == *address))
+        {
+            return Err(DomainError::ReservationConflictsWithSavedClient);
+        }
+        self.reserved_addresses = reservations;
+        self.applied_snapshot = None;
+        self.applied = RuntimeObservation::Unknown;
+        Ok(())
+    }
+
     pub fn draft_mut(&mut self) -> &mut Snapshot {
         &mut self.draft
     }
@@ -297,6 +316,8 @@ pub enum DomainError {
     AddressUnavailable,
     #[error("verified applied clients do not match the saved snapshot")]
     AppliedSnapshotMismatch,
+    #[error("persisted reservation conflicts with a saved client address")]
+    ReservationConflictsWithSavedClient,
 }
 
 /// Return the lowest available host in `range` without walking the subnet.