Ensure relay chain block number strictly increases

pallets/parachain-system/src/lib.rs

@@ -88,6 +88,51 @@ pub use relay_state_snapshot::{MessagingStateSnapshot, RelayChainStateProof};
 
 pub use pallet::*;
 
+/// Something that can check the associated relay block number.
+///
+/// Each Parachain block is build in the context of a relay chain block. This relay chain block
+/// has a block number associated this trait is about. With async backing it is legal to build
+/// multiple Parachain blocks per relay chain parent. With this trait it is possible for the
+/// Parachain to ensure that still only one Parachain block is build per relay chain parent.
+///
+/// By default [`RelayNumberStrictlyIncreases`] and [`AnyRelayNumber`] are provided.
+pub trait CheckAssociatedRelayNumber {
+	/// Check the current relay number versus the previous relay number.
+	///
+	/// The implementation should panic when there is something wrong.
+	fn check_associated_relay_number(
+		current: RelayChainBlockNumber,
+		previous: RelayChainBlockNumber,
+	);
+}
+
+/// Provides an implementation of [`CheckAssociatedRelayNumber`].
+///
+/// It will ensure that the associated relay block number strictly increases between Parachain
+/// blocks. This should be used by production Parachains when in doubt.
+pub struct RelayNumberStrictlyIncreases;
+
+impl CheckAssociatedRelayNumber for RelayNumberStrictlyIncreases {
+	fn check_associated_relay_number(
+		current: RelayChainBlockNumber,
+		previous: RelayChainBlockNumber,
+	) {
+		if current <= previous {
+			panic!("Relay chain block number needs to strictly increase between Parachain blocks!")
+		}
+	}
+}
+
+/// Provides an implementation of [`CheckAssociatedRelayNumber`].
+///
+/// This will accept any relay chain block number combination. This is mainly useful for
+/// test parachains.
+pub struct AnyRelayNumber;
+
+impl CheckAssociatedRelayNumber for AnyRelayNumber {
+	fn check_associated_relay_number(_: RelayChainBlockNumber, _: RelayChainBlockNumber) {}
+}
+
 #[frame_support::pallet]
 pub mod pallet {
 	use super::*;
@@ -128,6 +173,9 @@ pub mod pallet {
 
 		/// The weight we reserve at the beginning of the block for processing XCMP messages.
 		type ReservedXcmpWeight: Get<Weight>;
+
+		/// Something that can check the associated relay parent block number.
+		type CheckAssociatedRelayNumber: CheckAssociatedRelayNumber;
 	}
 
 	#[pallet::hooks]
@@ -232,7 +280,7 @@ pub mod pallet {
 			}
 
 			// Remove the validation from the old block.
-			<ValidationData<T>>::kill();
+			ValidationData::<T>::kill();
 			ProcessedDownwardMessages::<T>::kill();
 			HrmpWatermark::<T>::kill();
 			UpwardMessages::<T>::kill();
@@ -307,6 +355,13 @@ pub mod pallet {
 
 			Self::validate_validation_data(&vfp);
 
+			// Check that the associated relay chain block number is as expected.
+			T::CheckAssociatedRelayNumber::check_associated_relay_number(
+				vfp.relay_parent_number,
+				LastRelayChainBlockNumber::<T>::get(),
+			);
+			LastRelayChainBlockNumber::<T>::put(vfp.relay_parent_number);
+
 			let relay_state_proof = RelayChainStateProof::new(
 				T::SelfParaId::get(),
 				vfp.relay_parent_storage_root,
@@ -474,6 +529,11 @@ pub mod pallet {
 	#[pallet::storage]
 	pub(super) type DidSetValidationCode<T: Config> = StorageValue<_, bool, ValueQuery>;
 
+	/// The relay chain block number associated to the last parachain block.
+	#[pallet::storage]
+	pub(super) type LastRelayChainBlockNumber<T: Config> =
+		StorageValue<_, RelayChainBlockNumber, ValueQuery>;
+
 	/// An option which indicates if the relay-chain restricts signalling a validation code upgrade.
 	/// In other words, if this is `Some` and [`NewValidationCode`] is `Some` then the produced
 	/// candidate will be invalid.

pallets/parachain-system/src/tests.rs

@@ -107,6 +107,7 @@ impl Config for Test {
 	type ReservedDmpWeight = ReservedDmpWeight;
 	type XcmpMessageHandler = SaveIntoThreadLocal;
 	type ReservedXcmpWeight = ReservedXcmpWeight;
+	type CheckAssociatedRelayNumber = AnyRelayNumber;
 }
 
 pub struct FromThreadLocal;
@@ -226,8 +227,7 @@ struct BlockTests {
 	ran: bool,
 	relay_sproof_builder_hook:
 		Option<Box<dyn Fn(&BlockTests, RelayChainBlockNumber, &mut RelayStateSproofBuilder)>>,
-	persisted_validation_data_hook:
-		Option<Box<dyn Fn(&BlockTests, RelayChainBlockNumber, &mut PersistedValidationData)>>,
+	persisted_validation_data_hook: Option<Box<dyn Fn(&BlockTests, &mut PersistedValidationData)>>,
 	inherent_data_hook:
 		Option<Box<dyn Fn(&BlockTests, RelayChainBlockNumber, &mut ParachainInherentData)>>,
 }
@@ -274,10 +274,9 @@ impl BlockTests {
 		self
 	}
 
-	#[allow(dead_code)] // might come in handy in future. If now is future and it still hasn't - feel free.
 	fn with_validation_data<F>(mut self, f: F) -> Self
 	where
-		F: 'static + Fn(&BlockTests, RelayChainBlockNumber, &mut PersistedValidationData),
+		F: 'static + Fn(&BlockTests, &mut PersistedValidationData),
 	{
 		self.persisted_validation_data_hook = Some(Box::new(f));
 		self
@@ -319,7 +318,7 @@ impl BlockTests {
 					..Default::default()
 				};
 				if let Some(ref hook) = self.persisted_validation_data_hook {
-					hook(self, *n as RelayChainBlockNumber, &mut vfp);
+					hook(self, &mut vfp);
 				}
 
 				<ValidationData<Test>>::put(&vfp);
@@ -964,3 +963,14 @@ fn receive_hrmp_after_pause() {
 			});
 		});
 }
+
+#[test]
+#[should_panic = "Relay chain block number needs to strictly increase between Parachain blocks!"]
+fn test() {
+	BlockTests::new()
+		.with_validation_data(|_, data| {
+			data.relay_parent_number = 1;
+		})
+		.add(1, || {})
+		.add(2, || {});
+}

pallets/parachain-system/src/validate_block/implementation.rs

@@ -67,8 +67,8 @@ where
 	assert!(parent_head.hash() == *block.header().parent_hash(), "Invalid parent hash",);
 
 	// Create the db
-	let (db, root) = match storage_proof.to_memory_db(Some(parent_head.state_root())) {
-		Ok((db, root)) => (db, root),
+	let db = match storage_proof.to_memory_db(Some(parent_head.state_root())) {
+		Ok((db, _)) => db,
 		Err(_) => panic!("Compact proof decoding failure."),
 	};
 

pallets/xcmp-queue/src/mock.rs

@@ -16,6 +16,7 @@
 use super::*;
 use crate as xcmp_queue;
 use core::marker::PhantomData;
+use cumulus_pallet_parachain_system::AnyRelayNumber;
 use cumulus_primitives_core::{IsSystem, ParaId};
 use frame_support::{parameter_types, traits::OriginTrait};
 use frame_system::EnsureRoot;
@@ -109,6 +110,7 @@ impl cumulus_pallet_parachain_system::Config for Test {
 	type ReservedDmpWeight = ();
 	type XcmpMessageHandler = XcmpQueue;
 	type ReservedXcmpWeight = ();
+	type CheckAssociatedRelayNumber = AnyRelayNumber;
 }
 
 parameter_types! {

parachain-template/runtime/src/lib.rs

@@ -9,6 +9,7 @@ include!(concat!(env!("OUT_DIR"), "/wasm_binary.rs"));
 mod weights;
 pub mod xcm_config;
 
+use cumulus_pallet_parachain_system::RelayNumberStrictlyIncreases;
 use smallvec::smallvec;
 use sp_api::impl_runtime_apis;
 use sp_core::{crypto::KeyTypeId, OpaqueMetadata};
@@ -369,11 +370,12 @@ impl cumulus_pallet_parachain_system::Config for Runtime {
 	type Event = Event;
 	type OnSystemEvent = ();
 	type SelfParaId = parachain_info::Pallet<Runtime>;
+	type OutboundXcmpMessageSource = XcmpQueue;
 	type DmpMessageHandler = DmpQueue;
 	type ReservedDmpWeight = ReservedDmpWeight;
-	type OutboundXcmpMessageSource = XcmpQueue;
 	type XcmpMessageHandler = XcmpQueue;
 	type ReservedXcmpWeight = ReservedXcmpWeight;
+	type CheckAssociatedRelayNumber = RelayNumberStrictlyIncreases;
 }
 
 impl parachain_info::Config for Runtime {}

parachains/runtimes/assets/statemine/src/lib.rs

@@ -28,6 +28,7 @@ pub mod constants;
 mod weights;
 pub mod xcm_config;
 
+use cumulus_pallet_parachain_system::RelayNumberStrictlyIncreases;
 use sp_api::impl_runtime_apis;
 use sp_core::{crypto::KeyTypeId, OpaqueMetadata};
 use sp_runtime::{
@@ -416,6 +417,7 @@ impl cumulus_pallet_parachain_system::Config for Runtime {
 	type OutboundXcmpMessageSource = XcmpQueue;
 	type XcmpMessageHandler = XcmpQueue;
 	type ReservedXcmpWeight = ReservedXcmpWeight;
+	type CheckAssociatedRelayNumber = RelayNumberStrictlyIncreases;
 }
 
 impl parachain_info::Config for Runtime {}

parachains/runtimes/assets/statemint/src/lib.rs

@@ -57,6 +57,7 @@ pub mod constants;
 mod weights;
 pub mod xcm_config;
 
+use cumulus_pallet_parachain_system::RelayNumberStrictlyIncreases;
 use sp_api::impl_runtime_apis;
 use sp_core::{crypto::KeyTypeId, OpaqueMetadata};
 use sp_runtime::{
@@ -446,6 +447,7 @@ impl cumulus_pallet_parachain_system::Config for Runtime {
 	type OutboundXcmpMessageSource = XcmpQueue;
 	type XcmpMessageHandler = XcmpQueue;
 	type ReservedXcmpWeight = ReservedXcmpWeight;
+	type CheckAssociatedRelayNumber = RelayNumberStrictlyIncreases;
 }
 
 impl parachain_info::Config for Runtime {}

parachains/runtimes/assets/westmint/src/lib.rs

@@ -28,6 +28,7 @@ pub mod constants;
 mod weights;
 pub mod xcm_config;
 
+use cumulus_pallet_parachain_system::RelayNumberStrictlyIncreases;
 use sp_api::impl_runtime_apis;
 use sp_core::{crypto::KeyTypeId, OpaqueMetadata};
 use sp_runtime::{
@@ -406,11 +407,12 @@ impl cumulus_pallet_parachain_system::Config for Runtime {
 	type Event = Event;
 	type OnSystemEvent = ();
 	type SelfParaId = parachain_info::Pallet<Runtime>;
+	type OutboundXcmpMessageSource = XcmpQueue;
 	type DmpMessageHandler = DmpQueue;
 	type ReservedDmpWeight = ReservedDmpWeight;
-	type OutboundXcmpMessageSource = XcmpQueue;
 	type XcmpMessageHandler = XcmpQueue;
 	type ReservedXcmpWeight = ReservedXcmpWeight;
+	type CheckAssociatedRelayNumber = RelayNumberStrictlyIncreases;
 }
 
 impl parachain_info::Config for Runtime {}

parachains/runtimes/contracts/contracts-rococo/src/lib.rs

@@ -30,6 +30,7 @@ mod contracts;
 mod weights;
 mod xcm_config;
 
+use cumulus_pallet_parachain_system::RelayNumberStrictlyIncreases;
 use sp_api::impl_runtime_apis;
 use sp_core::{crypto::KeyTypeId, OpaqueMetadata};
 use sp_runtime::{
@@ -252,6 +253,7 @@ impl cumulus_pallet_parachain_system::Config for Runtime {
 	type OutboundXcmpMessageSource = XcmpQueue;
 	type XcmpMessageHandler = XcmpQueue;
 	type ReservedXcmpWeight = ConstU64<{ MAXIMUM_BLOCK_WEIGHT / 4 }>;
+	type CheckAssociatedRelayNumber = RelayNumberStrictlyIncreases;
 }
 
 impl pallet_randomness_collective_flip::Config for Runtime {}

parachains/runtimes/starters/seedling/src/lib.rs

@@ -27,6 +27,7 @@
 #[cfg(feature = "std")]
 include!(concat!(env!("OUT_DIR"), "/wasm_binary.rs"));
 
+use cumulus_pallet_parachain_system::RelayNumberStrictlyIncreases;
 use sp_api::impl_runtime_apis;
 use sp_core::OpaqueMetadata;
 use sp_runtime::{
@@ -166,6 +167,7 @@ impl cumulus_pallet_parachain_system::Config for Runtime {
 	type ReservedDmpWeight = ();
 	type XcmpMessageHandler = ();
 	type ReservedXcmpWeight = ();
+	type CheckAssociatedRelayNumber = RelayNumberStrictlyIncreases;
 }
 
 impl parachain_info::Config for Runtime {}

parachains/runtimes/starters/shell/src/lib.rs

@@ -32,6 +32,7 @@ include!(concat!(env!("OUT_DIR"), "/wasm_binary.rs"));
 pub mod xcm_config;
 
 use codec::{Decode, Encode};
+use cumulus_pallet_parachain_system::RelayNumberStrictlyIncreases;
 use frame_support::unsigned::TransactionValidityError;
 use scale_info::TypeInfo;
 use sp_api::impl_runtime_apis;
@@ -170,6 +171,7 @@ impl cumulus_pallet_parachain_system::Config for Runtime {
 	type ReservedDmpWeight = ReservedDmpWeight;
 	type XcmpMessageHandler = ();
 	type ReservedXcmpWeight = ();
+	type CheckAssociatedRelayNumber = RelayNumberStrictlyIncreases;
 }
 
 impl parachain_info::Config for Runtime {}

parachains/runtimes/testing/rococo-parachain/src/lib.rs

@@ -22,6 +22,7 @@
 #[cfg(feature = "std")]
 include!(concat!(env!("OUT_DIR"), "/wasm_binary.rs"));
 
+use cumulus_pallet_parachain_system::RelayNumberStrictlyIncreases;
 use sp_api::impl_runtime_apis;
 use sp_core::OpaqueMetadata;
 use sp_runtime::{
@@ -265,6 +266,7 @@ impl cumulus_pallet_parachain_system::Config for Runtime {
 	type ReservedDmpWeight = ReservedDmpWeight;
 	type XcmpMessageHandler = XcmpQueue;
 	type ReservedXcmpWeight = ReservedXcmpWeight;
+	type CheckAssociatedRelayNumber = RelayNumberStrictlyIncreases;
 }
 
 impl parachain_info::Config for Runtime {}

test/runtime/src/lib.rs

@@ -265,6 +265,7 @@ impl cumulus_pallet_parachain_system::Config for Runtime {
 	type ReservedDmpWeight = ();
 	type XcmpMessageHandler = ();
 	type ReservedXcmpWeight = ();
+	type CheckAssociatedRelayNumber = cumulus_pallet_parachain_system::AnyRelayNumber;
 }
 
 parameter_types! {