babe: make plan_config_change callable by root

frame/babe/src/default_weights.rs

@@ -23,6 +23,10 @@ use frame_support::weights::{
 };
 
 impl crate::WeightInfo for () {
+	fn plan_config_change() -> Weight {
+		DbWeight::get().writes(1)
+	}
+
 	fn report_equivocation(validator_count: u32) -> Weight {
 		// we take the validator set count from the membership proof to
 		// calculate the weight but we set a floor of 100 validators.

frame/babe/src/lib.rs

@@ -29,7 +29,7 @@ use frame_support::{
 	weights::{Pays, Weight},
 	Parameter,
 };
-use frame_system::{ensure_none, ensure_signed};
+use frame_system::{ensure_none, ensure_root, ensure_signed};
 use sp_application_crypto::Public;
 use sp_runtime::{
 	generic::DigestItem,
@@ -108,6 +108,7 @@ pub trait Config: pallet_timestamp::Config {
 }
 
 pub trait WeightInfo {
+	fn plan_config_change() -> Weight;
 	fn report_equivocation(validator_count: u32) -> Weight;
 }
 
@@ -314,6 +315,19 @@ decl_module! {
 				key_owner_proof,
 			)
 		}
+
+		/// Plan an epoch config change. The epoch config change is recorded and will be enacted on
+		/// the next call to `enact_epoch_change`. The config will be activated one epoch after.
+		/// Multiple calls to this method will replace any existing planned config change that had
+		/// not been enacted yet.
+		#[weight = <T as Config>::WeightInfo::plan_config_change()]
+		fn plan_config_change(
+			origin,
+			config: NextConfigDescriptor,
+		) {
+			ensure_root(origin)?;
+			NextEpochConfig::put(config);
+		}
 	}
 }
 
@@ -432,15 +446,6 @@ impl<T: Config> Module<T> {
 			})
 	}
 
-	/// Plan an epoch config change. The epoch config change is recorded and will be enacted on the
-	/// next call to `enact_epoch_change`. The config will be activated one epoch after. Multiple calls to this
-	/// method will replace any existing planned config change that had not been enacted yet.
-	pub fn plan_config_change(
-		config: NextConfigDescriptor,
-	) {
-		NextEpochConfig::put(config);
-	}
-
 	/// DANGEROUS: Enact an epoch change. Should be done on every block where `should_epoch_change` has returned `true`,
 	/// and the caller is the only caller of this function.
 	///

frame/babe/src/tests.rs

@@ -231,10 +231,13 @@ fn can_enact_next_config() {
 		assert_eq!(Babe::epoch_index(), 0);
 		go_to_block(2, 7);
 
-		Babe::plan_config_change(NextConfigDescriptor::V1 {
-			c: (1, 4),
-			allowed_slots: AllowedSlots::PrimarySlots,
-		});
+		Babe::plan_config_change(
+			Origin::root(),
+			NextConfigDescriptor::V1 {
+				c: (1, 4),
+				allowed_slots: AllowedSlots::PrimarySlots,
+			},
+		).unwrap();
 
 		progress_to_block(4);
 		Babe::on_finalize(9);
@@ -252,6 +255,39 @@ fn can_enact_next_config() {
 	});
 }
 
+#[test]
+fn only_root_can_enact_config_change() {
+	use sp_runtime::DispatchError;
+
+	new_test_ext(1).execute_with(|| {
+		let next_config = NextConfigDescriptor::V1 {
+			c: (1, 4),
+			allowed_slots: AllowedSlots::PrimarySlots,
+		};
+
+		let res = Babe::plan_config_change(
+			Origin::none(),
+			next_config.clone(),
+		);
+
+		assert_eq!(res, Err(DispatchError::BadOrigin));
+
+		let res = Babe::plan_config_change(
+			Origin::signed(1),
+			next_config.clone(),
+		);
+
+		assert_eq!(res, Err(DispatchError::BadOrigin));
+
+		let res = Babe::plan_config_change(
+			Origin::root(),
+			next_config,
+		);
+
+		assert!(res.is_ok());
+	});
+}
+
 #[test]
 fn can_fetch_current_and_next_epoch_data() {
 	new_test_ext(5).execute_with(|| {