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Adds support for returning a custom header from validate_block (#825)
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* Adds support for returning a custom header from `validate_block`

This adds support for returning a custom header from `validate_block`. Before this, we always
returned the header of the block that was validated (and still do it by default). However, after
this pr it is possible to set a custom header or better custom head data that will be returned
instead from `validate_block`. This can be for example when a chain wants to fork.

* FMT
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bkchr authored Dec 3, 2021
1 parent e70f7fd commit d0b5e2b
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Showing 8 changed files with 156 additions and 17 deletions.
34 changes: 31 additions & 3 deletions pallets/parachain-system/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -236,8 +236,9 @@ pub mod pallet {
HrmpWatermark::<T>::kill();
UpwardMessages::<T>::kill();
HrmpOutboundMessages::<T>::kill();
CustomValidationHeadData::<T>::kill();

weight += T::DbWeight::get().writes(5);
weight += T::DbWeight::get().writes(6);

// Here, in `on_initialize` we must report the weight for both `on_initialize` and
// `on_finalize`.
Expand Down Expand Up @@ -567,6 +568,12 @@ pub mod pallet {
#[pallet::storage]
pub(super) type AuthorizedUpgrade<T: Config> = StorageValue<_, T::Hash>;

/// A custom head data that should be returned as result of `validate_block`.
///
/// See [`Pallet::set_custom_validation_head_data`] for more information.
#[pallet::storage]
pub(super) type CustomValidationHeadData<T: Config> = StorageValue<_, Vec<u8>, OptionQuery>;

#[pallet::inherent]
impl<T: Config> ProvideInherent for Pallet<T> {
type Call = Call<T>;
Expand Down Expand Up @@ -692,6 +699,9 @@ impl<T: Config> Pallet<T> {
/// import, this is a no-op.
///
/// # Panics
///
/// Panics while validating the `PoV` on the relay chain if the [`PersistedValidationData`]
/// passed by the block author was incorrect.
fn validate_validation_data(validation_data: &PersistedValidationData) {
validate_block::with_validation_params(|params| {
assert_eq!(
Expand All @@ -714,8 +724,10 @@ impl<T: Config> Pallet<T> {
/// Checks if the sequence of the messages is valid, dispatches them and communicates the
/// number of processed messages to the collator via a storage update.
///
/// **Panics** if it turns out that after processing all messages the Message Queue Chain
/// hash doesn't match the expected.
/// # Panics
///
/// If it turns out that after processing all messages the Message Queue Chain
/// hash doesn't match the expected.
fn process_inbound_downward_messages(
expected_dmq_mqc_head: relay_chain::Hash,
downward_messages: Vec<InboundDownwardMessage>,
Expand Down Expand Up @@ -907,6 +919,22 @@ impl<T: Config> Pallet<T> {
new_validation_code: NewValidationCode::<T>::get().map(Into::into),
}
}

/// Set a custom head data that should be returned as result of `validate_block`.
///
/// This will overwrite the head data that is returned as result of `validate_block` while
/// validating a `PoV` on the relay chain. Normally the head data that is being returned
/// by `validate_block` is the header of the block that is validated, thus it can be
/// enacted as the new best block. However, for features like forking it can be useful
/// to overwrite the head data with a custom header.
///
/// # Attention
///
/// This should only be used when you are sure what you are doing as this can brick
/// your Parachain.
pub fn set_custom_validation_head_data(head_data: Vec<u8>) {
CustomValidationHeadData::<T>::put(head_data);
}
}

pub struct ParachainSetCode<T>(sp_std::marker::PhantomData<T>);
Expand Down
7 changes: 7 additions & 0 deletions pallets/parachain-system/src/validate_block/implementation.rs
Original file line number Diff line number Diff line change
Expand Up @@ -161,6 +161,13 @@ where
let horizontal_messages = crate::HrmpOutboundMessages::<PSC>::get();
let hrmp_watermark = crate::HrmpWatermark::<PSC>::get();

let head_data =
if let Some(custom_head_data) = crate::CustomValidationHeadData::<PSC>::get() {
HeadData(custom_head_data)
} else {
head_data
};

ValidationResult {
head_data,
new_validation_code: new_validation_code.map(Into::into),
Expand Down
55 changes: 51 additions & 4 deletions pallets/parachain-system/src/validate_block/tests.rs
Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,8 @@
use codec::{Decode, Encode};
use cumulus_primitives_core::{ParachainBlockData, PersistedValidationData};
use cumulus_test_client::{
runtime::{Block, Hash, Header, UncheckedExtrinsic, WASM_BINARY},
generate_extrinsic,
runtime::{Block, Hash, Header, TestPalletCall, UncheckedExtrinsic, WASM_BINARY},
transfer, BlockData, BuildParachainBlockData, Client, DefaultTestClientBuilderExt, HeadData,
InitBlockBuilder, TestClientBuilder, TestClientBuilderExt, ValidationParams,
};
Expand All @@ -26,11 +27,11 @@ use sp_keyring::AccountKeyring::*;
use sp_runtime::{generic::BlockId, traits::Header as HeaderT};
use std::{env, process::Command};

fn call_validate_block(
fn call_validate_block_encoded_header(
parent_head: Header,
block_data: ParachainBlockData<Block>,
relay_parent_storage_root: Hash,
) -> cumulus_test_client::ExecutorResult<Header> {
) -> cumulus_test_client::ExecutorResult<Vec<u8>> {
cumulus_test_client::validate_block(
ValidationParams {
block_data: BlockData(block_data.encode()),
Expand All @@ -40,7 +41,16 @@ fn call_validate_block(
},
&WASM_BINARY.expect("You need to build the WASM binaries to run the tests!"),
)
.map(|v| Header::decode(&mut &v.head_data.0[..]).expect("Decodes `Header`."))
.map(|v| v.head_data.0)
}

fn call_validate_block(
parent_head: Header,
block_data: ParachainBlockData<Block>,
relay_parent_storage_root: Hash,
) -> cumulus_test_client::ExecutorResult<Header> {
call_validate_block_encoded_header(parent_head, block_data, relay_parent_storage_root)
.map(|v| Header::decode(&mut &v[..]).expect("Decodes `Header`."))
}

fn create_test_client() -> (Client, Header) {
Expand Down Expand Up @@ -126,6 +136,43 @@ fn validate_block_with_extra_extrinsics() {
assert_eq!(header, res_header);
}

#[test]
fn validate_block_returns_custom_head_data() {
sp_tracing::try_init_simple();

let expected_header = vec![1, 3, 3, 7, 4, 5, 6];

let (client, parent_head) = create_test_client();
let extra_extrinsics = vec![
transfer(&client, Alice, Bob, 69),
generate_extrinsic(
&client,
Charlie,
TestPalletCall::set_custom_validation_head_data {
custom_header: expected_header.clone(),
},
),
transfer(&client, Bob, Charlie, 100),
];

let TestBlockData { block, validation_data } = build_block_with_witness(
&client,
extra_extrinsics,
parent_head.clone(),
Default::default(),
);
let header = block.header().clone();
assert_ne!(expected_header, header.encode());

let res_header = call_validate_block_encoded_header(
parent_head,
block,
validation_data.relay_parent_storage_root,
)
.expect("Calls `validate_block`");
assert_eq!(expected_header, res_header);
}

#[test]
fn validate_block_invalid_parent_hash() {
sp_tracing::try_init_simple();
Expand Down
5 changes: 4 additions & 1 deletion test/client/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -122,7 +122,7 @@ fn genesis_config() -> GenesisConfig {
pub fn generate_extrinsic(
client: &Client,
origin: sp_keyring::AccountKeyring,
function: Call,
function: impl Into<Call>,
) -> UncheckedExtrinsic {
let current_block_hash = client.info().best_hash;
let current_block = client.info().best_number.saturated_into();
Expand All @@ -139,6 +139,9 @@ pub fn generate_extrinsic(
frame_system::CheckWeight::<Runtime>::new(),
pallet_transaction_payment::ChargeTransactionPayment::<Runtime>::from(tip),
);

let function = function.into();

let raw_payload = SignedPayload::from_raw(
function.clone(),
extra.clone(),
Expand Down
20 changes: 12 additions & 8 deletions test/runtime/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,8 @@ pub mod wasm_spec_version_incremented {
include!(concat!(env!("OUT_DIR"), "/wasm_binary_spec_version_incremented.rs"));
}

mod test_pallet;

use frame_support::traits::OnRuntimeUpgrade;
use sp_api::{decl_runtime_apis, impl_runtime_apis};
use sp_core::OpaqueMetadata;
Expand Down Expand Up @@ -58,6 +60,7 @@ pub use pallet_timestamp::Call as TimestampCall;
#[cfg(any(feature = "std", test))]
pub use sp_runtime::BuildStorage;
pub use sp_runtime::{Perbill, Permill};
pub use test_pallet::Call as TestPalletCall;

pub type SessionHandlers = ();

Expand Down Expand Up @@ -265,20 +268,21 @@ parameter_types! {
pub storage ParachainId: cumulus_primitives_core::ParaId = 100.into();
}

impl test_pallet::Config for Runtime {}

construct_runtime! {
pub enum Runtime where
Block = Block,
NodeBlock = NodeBlock,
UncheckedExtrinsic = UncheckedExtrinsic,
{
System: frame_system::{Pallet, Call, Storage, Config, Event<T>},
ParachainSystem: cumulus_pallet_parachain_system::{
Pallet, Call, Config, Storage, Inherent, Event<T>, ValidateUnsigned,
},
Timestamp: pallet_timestamp::{Pallet, Call, Storage, Inherent},
Balances: pallet_balances::{Pallet, Call, Storage, Config<T>, Event<T>},
Sudo: pallet_sudo::{Pallet, Call, Storage, Config<T>, Event<T>},
TransactionPayment: pallet_transaction_payment::{Pallet, Storage},
System: frame_system,
ParachainSystem: cumulus_pallet_parachain_system,
Timestamp: pallet_timestamp,
Balances: pallet_balances,
Sudo: pallet_sudo,
TransactionPayment: pallet_transaction_payment,
TestPallet: test_pallet,
}
}

Expand Down
49 changes: 49 additions & 0 deletions test/runtime/src/test_pallet.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,49 @@
// Copyright 2021 Parity Technologies (UK) Ltd.
// This file is part of Cumulus.

// Cumulus 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.

// Cumulus 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 Cumulus. If not, see <http://www.gnu.org/licenses/>.

/// A special pallet that exposes dispatchables that are only useful for testing.
pub use pallet::*;

#[frame_support::pallet]
pub mod pallet {
use frame_support::pallet_prelude::*;
use frame_system::pallet_prelude::*;

#[pallet::pallet]
#[pallet::generate_store(pub(super) trait Store)]
pub struct Pallet<T>(_);

#[pallet::config]
pub trait Config: frame_system::Config + cumulus_pallet_parachain_system::Config {}

#[pallet::hooks]
impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {}

#[pallet::call]
impl<T: Config> Pallet<T> {
/// A test dispatchable for setting a custom head data in `validate_block`.
#[pallet::weight(0)]
pub fn set_custom_validation_head_data(
_: OriginFor<T>,
custom_header: sp_std::vec::Vec<u8>,
) -> DispatchResult {
cumulus_pallet_parachain_system::Pallet::<T>::set_custom_validation_head_data(
custom_header,
);
Ok(())
}
}
}
2 changes: 1 addition & 1 deletion test/service/benches/transaction_throughput.rs
Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@

use criterion::{criterion_group, criterion_main, BatchSize, Criterion, Throughput};
use cumulus_test_runtime::{AccountId, BalancesCall, SudoCall};
use futures::{future, join, StreamExt};
use futures::{future, StreamExt};
use polkadot_service::polkadot_runtime::constants::currency::DOLLARS;
use sc_transaction_pool_api::{TransactionPool as _, TransactionSource, TransactionStatus};
use sp_core::{crypto::Pair, sr25519};
Expand Down
1 change: 1 addition & 0 deletions test/service/src/chain_spec.rs
Original file line number Diff line number Diff line change
Expand Up @@ -128,5 +128,6 @@ fn testnet_genesis(
balances: endowed_accounts.iter().cloned().map(|k| (k, 1 << 60)).collect(),
},
sudo: cumulus_test_runtime::SudoConfig { key: root_key },
transaction_payment: Default::default(),
}
}

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