XCM: Properly set the pricing for the DMP router (#6843)

* Properly set the pricing for the DMP router

* Publicize price types

* Use FixedU128 instead of Percent

* Add sp-arithmetic as a dependency for rococo runtime

* Add sp-arithmetic as a dependency to all runtimes

* Remove duplicate import

* Add missing import

* Fix tests

* Create an appropriate QueueDownwardMessageError variant

* Recalculate delivery fee factor based on past queue sizes

* Remove unused error variant

* Fixes

* Fixes

* Remove unused imports

* Rewrite fee factor update mechanism

* Remove unused imports

* Fixes

* Update runtime/parachains/src/dmp.rs

Co-authored-by: Squirrel <gilescope@gmail.com>

* Make DeliveryFeeFactor be a StorageMap keyed on ParaIds

* Fixes

* introduce limit for fee increase on dmp queue

* add message_size based fee factor to increment_fee_factor

* change message_size fee rate to correct value

* fix div by 0 error

* bind limit to variable

* fix message_size_factor and add DeliveryFeeFactor test

* add test for ExponentialPrice implementation

* make test formula based

* make delivery fee factor test formula based

* add max value test for DeliveryFeeFactor and move limit to config

* change threshold back to dynamic value and fix tests

* fmt

* suggested changes and fmt

* small stylistic change

* fmt

* change to tokenlocation

* small fixes

* fmt

* remove sp_arithmetic dependency

* Update runtime/parachains/src/dmp.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

---------

Co-authored-by: Squirrel <gilescope@gmail.com>
Co-authored-by: Just van Stam <just.van.stam@gmail.com>
Co-authored-by: Just van Stam <vstam1@users.noreply.github.com>
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

polkadot/runtime/kusama/Cargo.toml

@@ -24,7 +24,7 @@ sp-api = { git = "https://github.com/paritytech/substrate", branch = "master", d
 inherents = { package = "sp-inherents", git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
 offchain-primitives = { package = "sp-offchain", git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
 sp-std = { package = "sp-std", git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
-sp-arithmetic = { package = "sp-arithmetic", git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+sp-arithmetic = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
 sp-io = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
 sp-mmr-primitives = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
 sp-runtime = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
@@ -128,6 +128,7 @@ std = [
 	"parity-scale-codec/std",
 	"scale-info/std",
 	"inherents/std",
+	"sp-arithmetic/std",
 	"sp-core/std",
 	"sp-api/std",
 	"tx-pool-api/std",

polkadot/runtime/kusama/src/lib.rs

@@ -1410,7 +1410,7 @@ construct_runtime! {
 		ParaScheduler: parachains_scheduler::{Pallet, Storage} = 55,
 		Paras: parachains_paras::{Pallet, Call, Storage, Event, Config, ValidateUnsigned} = 56,
 		Initializer: parachains_initializer::{Pallet, Call, Storage} = 57,
-		Dmp: parachains_dmp::{Pallet, Call, Storage} = 58,
+		Dmp: parachains_dmp::{Pallet, Storage} = 58,
 		Ump: parachains_ump::{Pallet, Call, Storage, Event} = 59,
 		Hrmp: parachains_hrmp::{Pallet, Call, Storage, Event<T>, Config} = 60,
 		ParaSessionInfo: parachains_session_info::{Pallet, Storage} = 61,

polkadot/runtime/kusama/src/xcm_config.rs

@@ -17,8 +17,9 @@
 //! XCM configurations for the Kusama runtime.
 
 use super::{
-	parachains_origin, AccountId, AllPalletsWithSystem, Balances, Fellows, ParaId, Runtime,
-	RuntimeCall, RuntimeEvent, RuntimeOrigin, StakingAdmin, WeightToFee, XcmPallet,
+	parachains_origin, AccountId, AllPalletsWithSystem, Balances, Dmp, Fellows, ParaId, Runtime,
+	RuntimeCall, RuntimeEvent, RuntimeOrigin, StakingAdmin, TransactionByteFee, WeightToFee,
+	XcmPallet,
 };
 use frame_support::{
 	match_types, parameter_types,
@@ -26,7 +27,12 @@ use frame_support::{
 	weights::Weight,
 };
 use frame_system::EnsureRoot;
-use runtime_common::{crowdloan, paras_registrar, xcm_sender, ToAuthor};
+use kusama_runtime_constants::currency::CENTS;
+use runtime_common::{
+	crowdloan, paras_registrar,
+	xcm_sender::{ChildParachainRouter, ExponentialPrice},
+	ToAuthor,
+};
 use sp_core::ConstU32;
 use xcm::latest::prelude::*;
 use xcm_builder::{
@@ -101,13 +107,21 @@ parameter_types! {
 	/// Maximum number of instructions in a single XCM fragment. A sanity check against weight
 	/// calculations getting too crazy.
 	pub const MaxInstructions: u32 = 100;
+	/// The asset ID for the asset that we use to pay for message delivery fees.
+	pub FeeAssetId: AssetId = Concrete(TokenLocation::get());
+	/// The base fee for the message delivery fees.
+	pub const BaseDeliveryFee: u128 = CENTS.saturating_mul(3);
 }
 
 /// The XCM router. When we want to send an XCM message, we use this type. It amalgamates all of our
 /// individual routers.
 pub type XcmRouter = (
 	// Only one router so far - use DMP to communicate with child parachains.
-	xcm_sender::ChildParachainRouter<Runtime, XcmPallet, ()>,
+	ChildParachainRouter<
+		Runtime,
+		XcmPallet,
+		ExponentialPrice<FeeAssetId, BaseDeliveryFee, TransactionByteFee, Dmp>,
+	>,
 );
 
 parameter_types! {