Sudo utility for establishing an HRMP channel (#2067)

* Clean up of visibility of helper fns

* Document HRMP channel dispatchables

* Provide the sudo_establish_hrmp_channel dispatchable function

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

runtime/common/src/paras_sudo_wrapper.rs

@@ -88,5 +88,29 @@ decl_module! {
 						Error::<T>::ExceedsMaxMessageSize.into(),
 				})
 		}
+
+		/// Forcefully establish a channel from the sender to the recipient.
+		///
+		/// This is equivalent to sending an `Hrmp::hrmp_init_open_channel` extrinsic followed by
+		/// `Hrmp::hrmp_accept_open_channel`.
+		#[weight = (1_000, DispatchClass::Operational)]
+		pub fn sudo_establish_hrmp_channel(
+			origin,
+			sender: ParaId,
+			recipient: ParaId,
+			max_capacity: u32,
+			max_message_size: u32,
+		) -> DispatchResult {
+			ensure_root(origin)?;
+
+			<hrmp::Module<T>>::init_open_channel(
+				sender,
+				recipient,
+				max_capacity,
+				max_message_size,
+			)?;
+			<hrmp::Module<T>>::accept_open_channel(recipient, sender)?;
+			Ok(())
+		}
 	}
 }

runtime/parachains/src/hrmp.rs

@@ -325,8 +325,18 @@ decl_module! {
 	pub struct Module<T: Config> for enum Call where origin: <T as frame_system::Config>::Origin {
 		type Error = Error<T>;
 
+		/// Initiate opening a channel from a parachain to a given recipient with given channel
+		/// parameters.
+		///
+		/// - `proposed_max_capacity` - specifies how many messages can be in the channel at once.
+		/// - `proposed_max_message_size` - specifies the maximum size of any of the messages.
+		///
+		/// These numbers are a subject to the relay-chain configuration limits.
+		///
+		/// The channel can be opened only after the recipient confirms it and only on a session
+		/// change.
 		#[weight = 0]
-		fn hrmp_init_open_channel(
+		pub fn hrmp_init_open_channel(
 			origin,
 			recipient: ParaId,
 			proposed_max_capacity: u32,
@@ -342,15 +352,22 @@ decl_module! {
 			Ok(())
 		}
 
+		/// Accept a pending open channel request from the given sender.
+		///
+		/// The channel will be opened only on the next session boundary.
 		#[weight = 0]
-		fn hrmp_accept_open_channel(origin, sender: ParaId) -> DispatchResult {
+		pub fn hrmp_accept_open_channel(origin, sender: ParaId) -> DispatchResult {
 			let origin = ensure_parachain(<T as Config>::Origin::from(origin))?;
 			Self::accept_open_channel(origin, sender)?;
 			Ok(())
 		}
 
+		/// Initiate unilateral closing of a channel. The origin must be either the sender or the
+		/// recipient in the channel being closed.
+		///
+		/// The closure can only happen on a session change.
 		#[weight = 0]
-		fn hrmp_close_channel(origin, channel_id: HrmpChannelId) -> DispatchResult {
+		pub fn hrmp_close_channel(origin, channel_id: HrmpChannelId) -> DispatchResult {
 			let origin = ensure_parachain(<T as Config>::Origin::from(origin))?;
 			Self::close_channel(origin, channel_id)?;
 			Ok(())
@@ -808,7 +825,12 @@ impl<T: Config> Module<T> {
 		weight
 	}
 
-	pub(super) fn init_open_channel(
+	/// Initiate opening a channel from a parachain to a given recipient with given channel
+	/// parameters.
+	///
+	/// Basically the same as [`hrmp_init_open_channel`](Module::hrmp_init_open_channel) but intendend for calling directly from
+	/// other pallets rather than dispatched.
+	pub fn init_open_channel(
 		origin: ParaId,
 		recipient: ParaId,
 		proposed_max_capacity: u32,
@@ -902,7 +924,11 @@ impl<T: Config> Module<T> {
 		Ok(())
 	}
 
-	pub(super) fn accept_open_channel(origin: ParaId, sender: ParaId) -> Result<(), Error<T>> {
+	/// Accept a pending open channel request from the given sender.
+	///
+	/// Basically the same as [`hrmp_accept_open_channel`](Module::hrmp_accept_open_channel) but intendend for calling directly from
+	/// other pallets rather than dispatched.
+	pub fn accept_open_channel(origin: ParaId, sender: ParaId) -> Result<(), Error<T>> {
 		let channel_id = HrmpChannelId {
 			sender,
 			recipient: origin,
@@ -958,7 +984,7 @@ impl<T: Config> Module<T> {
 		Ok(())
 	}
 
-	pub(super) fn close_channel(origin: ParaId, channel_id: HrmpChannelId) -> Result<(), Error<T>> {
+	fn close_channel(origin: ParaId, channel_id: HrmpChannelId) -> Result<(), Error<T>> {
 		// check if the origin is allowed to close the channel.
 		ensure!(
 			origin == channel_id.sender || origin == channel_id.recipient,