sudo_queue_downward_message (#1941)

* Add a sudo wrapper for Dmp::queue_downward_message

* Apply suggestions from code review

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

* Stylistic changes

* Remove trailing whitespaces

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

polkadot/runtime/common/src/paras_sudo_wrapper.rs

@@ -16,22 +16,32 @@
 
 //! A simple wrapper allowing `Sudo` to call into `paras` routines.
 
+use sp_std::prelude::*;
 use frame_support::{
-	decl_error, decl_module,
+	decl_error, decl_module, ensure,
 	dispatch::DispatchResult,
 	weights::DispatchClass,
 };
 use frame_system::ensure_root;
 use runtime_parachains::{
-	dmp, ump, hrmp, paras::{self, ParaGenesisArgs},
+	configuration, dmp, ump, hrmp, paras::{self, ParaGenesisArgs},
 };
 use primitives::v1::Id as ParaId;
 
 /// The module's configuration trait.
-pub trait Trait: paras::Trait + dmp::Trait + ump::Trait + hrmp::Trait { }
+pub trait Trait:
+	configuration::Trait + paras::Trait + dmp::Trait + ump::Trait + hrmp::Trait
+{
+}
 
 decl_error! {
-	pub enum Error for Module<T: Trait> { }
+	pub enum Error for Module<T: Trait> {
+		/// The specified parachain or parathread is not registered.
+		ParaDoesntExist,
+		/// A DMP message couldn't be sent because it exceeds the maximum size allowed for a downward
+		/// message.
+		ExceedsMaxMessageSize,
+	}
 }
 
 decl_module! {
@@ -58,5 +68,21 @@ decl_module! {
 			runtime_parachains::schedule_para_cleanup::<T>(id);
 			Ok(())
 		}
+
+		/// Send a downward message to the given para.
+		///
+		/// The given parachain should exist and the payload should not exceed the preconfigured size
+		/// `config.max_downward_message_size`.
+		#[weight = (1_000, DispatchClass::Operational)]
+		pub fn sudo_queue_downward_message(origin, id: ParaId, payload: Vec<u8>) -> DispatchResult {
+			ensure_root(origin)?;
+			ensure!(<paras::Module<T>>::is_valid_para(id), Error::<T>::ParaDoesntExist);
+			let config = <configuration::Module<T>>::config();
+			<dmp::Module<T>>::queue_downward_message(&config, id, payload)
+				.map_err(|e| match e {
+					dmp::QueueDownwardMessageError::ExceedsMaxMessageSize =>
+						Error::<T>::ExceedsMaxMessageSize.into(),
+				})
+		}
 	}
 }

polkadot/runtime/parachains/src/paras.rs

@@ -542,7 +542,7 @@ impl<T: Trait> Module<T> {
 	}
 
 	/// Returns whether the given ID refers to a valid para.
-	pub(crate) fn is_valid_para(id: ParaId) -> bool {
+	pub fn is_valid_para(id: ParaId) -> bool {
 		Self::parachains().binary_search(&id).is_ok()
 			|| Self::is_parathread(id)
 	}