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// Copyright (C) Parity Technologies (UK) Ltd.
// This file is part of Polkadot.
// Polkadot is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Polkadot is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Polkadot. If not, see <http://www.gnu.org/licenses/>.
use frame_system::pallet_prelude::BlockNumberFor;
use primitives::Id as ParaId;
use runtime_parachains::{
configuration::{self, HostConfiguration},
use sp_runtime::FixedPointNumber;
use sp_std::{marker::PhantomData, prelude::*};
use xcm::prelude::*;
use SendError::*;
/// Simple value-bearing trait for determining/expressing the assets required to be paid for a
/// messages to be delivered to a parachain.
pub trait PriceForMessageDelivery {
/// Type used for charging different prices to different destinations
type Id;
/// Return the assets required to deliver `message` to the given `para` destination.
fn price_for_delivery(id: Self::Id, message: &Xcm<()>) -> MultiAssets;
impl PriceForMessageDelivery for () {
type Id = ();
fn price_for_delivery(_: Self::Id, _: &Xcm<()>) -> MultiAssets {
MultiAssets::new()
}
}
pub struct NoPriceForMessageDelivery<Id>(PhantomData<Id>);
impl<Id> PriceForMessageDelivery for NoPriceForMessageDelivery<Id> {
type Id = Id;
fn price_for_delivery(_: Self::Id, _: &Xcm<()>) -> MultiAssets {
/// Implementation of [`PriceForMessageDelivery`] which returns a fixed price.
impl<T: Get<MultiAssets>> PriceForMessageDelivery for ConstantPrice<T> {
type Id = ();
fn price_for_delivery(_: Self::Id, _: &Xcm<()>) -> MultiAssets {
/// Implementation of [`PriceForMessageDelivery`] which returns an exponentially increasing price.
/// The formula for the fee is based on the sum of a base fee plus a message length fee, multiplied
/// by a specified factor. In mathematical form:
///
/// `F * (B + encoded_msg_len * M)`
///
/// Thus, if F = 1 and M = 0, this type is equivalent to [`ConstantPrice<B>`].
///
/// The type parameters are understood as follows:
///
/// - `A`: Used to denote the asset ID that will be used for paying the delivery fee.
/// - `B`: The base fee to pay for message delivery.
/// - `M`: The fee to pay for each and every byte of the message after encoding it.
/// - `F`: A fee factor multiplier. It can be understood as the exponent term in the formula.
pub struct ExponentialPrice<A, B, M, F>(sp_std::marker::PhantomData<(A, B, M, F)>);
impl<A: Get<AssetId>, B: Get<u128>, M: Get<u128>, F: FeeTracker> PriceForMessageDelivery
for ExponentialPrice<A, B, M, F>
{
type Id = F::Id;
fn price_for_delivery(id: Self::Id, msg: &Xcm<()>) -> MultiAssets {
let msg_fee = (msg.encoded_size() as u128).saturating_mul(M::get());
let fee_sum = B::get().saturating_add(msg_fee);
let amount = F::get_fee_factor(id).saturating_mul_int(fee_sum);
(A::get(), amount).into()
}
}
/// XCM sender for relay chain. It only sends downward message.
pub struct ChildParachainRouter<T, W, P>(PhantomData<(T, W, P)>);
impl<T: configuration::Config + dmp::Config, W: xcm::WrapVersion, P> SendXcm
for ChildParachainRouter<T, W, P>
where
P: PriceForMessageDelivery<Id = ParaId>,
type Ticket = (HostConfiguration<BlockNumberFor<T>>, ParaId, Vec<u8>);
fn validate(
dest: &mut Option<MultiLocation>,
msg: &mut Option<Xcm<()>>,
) -> SendResult<(HostConfiguration<BlockNumberFor<T>>, ParaId, Vec<u8>)> {
let d = dest.take().ok_or(MissingArgument)?;
let id = if let MultiLocation { parents: 0, interior: X1(Parachain(id)) } = &d {
*id
} else {
*dest = Some(d);
return Err(NotApplicable)
};
// Downward message passing.
let xcm = msg.take().ok_or(MissingArgument)?;
let config = <configuration::Pallet<T>>::config();
let para = id.into();
let price = P::price_for_delivery(para, &xcm);
let blob = W::wrap_version(&d, xcm).map_err(|()| DestinationUnsupported)?.encode();
<dmp::Pallet<T>>::can_queue_downward_message(&config, ¶, &blob)
.map_err(Into::<SendError>::into)?;
Ok(((config, para, blob), price))
}
fn deliver(
(config, para, blob): (HostConfiguration<BlockNumberFor<T>>, ParaId, Vec<u8>),
) -> Result<XcmHash, SendError> {
let hash = sp_io::hashing::blake2_256(&blob[..]);
<dmp::Pallet<T>>::queue_downward_message(&config, para, blob)
.map(|()| hash)
.map_err(|_| SendError::Transport(&"Error placing into DMP queue"))
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/// Implementation of `pallet_xcm_benchmarks::EnsureDelivery` which helps to ensure delivery to the
/// `ParaId` parachain (sibling or child). Deposits existential deposit for origin (if needed).
/// Deposits estimated fee to the origin account (if needed).
/// Allows to trigger additional logic for specific `ParaId` (e.g. open HRMP channel) (if neeeded).
#[cfg(feature = "runtime-benchmarks")]
pub struct ToParachainDeliveryHelper<
XcmConfig,
ExistentialDeposit,
PriceForDelivery,
ParaId,
ToParaIdHelper,
>(
sp_std::marker::PhantomData<(
XcmConfig,
ExistentialDeposit,
PriceForDelivery,
ParaId,
ToParaIdHelper,
)>,
);
#[cfg(feature = "runtime-benchmarks")]
impl<
XcmConfig: xcm_executor::Config,
ExistentialDeposit: Get<Option<MultiAsset>>,
PriceForDelivery: PriceForMessageDelivery<Id = ParaId>,
Parachain: Get<ParaId>,
ToParachainHelper: EnsureForParachain,
> pallet_xcm_benchmarks::EnsureDelivery
for ToParachainDeliveryHelper<
XcmConfig,
ExistentialDeposit,
PriceForDelivery,
Parachain,
ToParachainHelper,
>
{
fn ensure_successful_delivery(
origin_ref: &MultiLocation,
_dest: &MultiLocation,
fee_reason: xcm_executor::traits::FeeReason,
) -> (Option<xcm_executor::FeesMode>, Option<MultiAssets>) {
use xcm_executor::{
traits::{FeeManager, TransactAsset},
FeesMode,
};
let mut fees_mode = None;
if !XcmConfig::FeeManager::is_waived(Some(origin_ref), fee_reason) {
// if not waived, we need to set up accounts for paying and receiving fees
// mint ED to origin if needed
if let Some(ed) = ExistentialDeposit::get() {
XcmConfig::AssetTransactor::deposit_asset(&ed, &origin_ref, None).unwrap();
}
// overestimate delivery fee
let overestimated_xcm = vec![ClearOrigin; 128].into();
let overestimated_fees =
PriceForDelivery::price_for_delivery(Parachain::get(), &overestimated_xcm);
// mint overestimated fee to origin
for fee in overestimated_fees.inner() {
XcmConfig::AssetTransactor::deposit_asset(&fee, &origin_ref, None).unwrap();
}
// allow more initialization for target parachain
ToParachainHelper::ensure(Parachain::get());
// expected worst case - direct withdraw
fees_mode = Some(FeesMode { jit_withdraw: true });
}
(fees_mode, None)
}
}
/// Ensure more initialization for `ParaId`. (e.g. open HRMP channels, ...)
#[cfg(feature = "runtime-benchmarks")]
pub trait EnsureForParachain {
fn ensure(para_id: ParaId);
}
#[cfg(feature = "runtime-benchmarks")]
impl EnsureForParachain for () {
fn ensure(_: ParaId) {
// doing nothing
}
}
#[cfg(test)]
mod tests {
use super::*;
use frame_support::parameter_types;
use runtime_parachains::FeeTracker;
use sp_runtime::FixedU128;
parameter_types! {
pub const BaseDeliveryFee: u128 = 300_000_000;
pub const TransactionByteFee: u128 = 1_000_000;
pub FeeAssetId: AssetId = Concrete(Here.into());
}
struct TestFeeTracker;
impl FeeTracker for TestFeeTracker {
type Id = ParaId;
fn get_fee_factor(_: Self::Id) -> FixedU128 {
FixedU128::from_rational(101, 100)
}
fn increase_fee_factor(_: Self::Id, _: FixedU128) -> FixedU128 {
FixedU128::from_rational(101, 100)
}
fn decrease_fee_factor(_: Self::Id) -> FixedU128 {
FixedU128::from_rational(101, 100)
}
}
type TestExponentialPrice =
ExponentialPrice<FeeAssetId, BaseDeliveryFee, TransactionByteFee, TestFeeTracker>;
#[test]
fn exponential_price_correct_price_calculation() {
let id: ParaId = 123.into();
let b: u128 = BaseDeliveryFee::get();
let m: u128 = TransactionByteFee::get();
// F * (B + msg_length * M)
// message_length = 1
let result: u128 = TestFeeTracker::get_fee_factor(id).saturating_mul_int(b + m);
TestExponentialPrice::price_for_delivery(id, &Xcm(vec![])),
(FeeAssetId::get(), result).into()
);
// message size = 2
let result: u128 = TestFeeTracker::get_fee_factor(id).saturating_mul_int(b + (2 * m));
TestExponentialPrice::price_for_delivery(id, &Xcm(vec![ClearOrigin])),
(FeeAssetId::get(), result).into()
);
// message size = 4
let result: u128 = TestFeeTracker::get_fee_factor(id).saturating_mul_int(b + (4 * m));
TestExponentialPrice::price_for_delivery(
&Xcm(vec![SetAppendix(Xcm(vec![ClearOrigin]))])
),
(FeeAssetId::get(), result).into()
);
}
}