Skip balance and gas price checks on non-transactional calls (#57)

* Skip balance and gas price checks on non-transactional calls

(cherry picked from commit b7081b4)

* Update comment

(cherry picked from commit caf6566)

* Ensure account nonce first

(cherry picked from commit 81abadd)

client/rpc/src/eth.rs

@@ -468,6 +468,12 @@ fn fee_details(
 	match (request_gas_price, request_max_fee, request_priority) {
 		(gas_price, None, None) => {
 			// Legacy request, all default to gas price.
+			// A zero-set gas price is None.
+			let gas_price = if gas_price.unwrap_or_default().is_zero() {
+				None
+			} else {
+				gas_price
+			};
 			Ok(FeeDetails {
 				gas_price,
 				max_fee_per_gas: gas_price,
@@ -476,6 +482,12 @@ fn fee_details(
 		}
 		(_, max_fee, max_priority) => {
 			// eip-1559
+			// A zero-set max fee is None.
+			let max_fee = if max_fee.unwrap_or_default().is_zero() {
+				None
+			} else {
+				max_fee
+			};
 			// Ensure `max_priority_fee_per_gas` is less or equal to `max_fee_per_gas`.
 			if let Some(max_priority) = max_priority {
 				let max_fee = max_fee.unwrap_or_default();

frame/ethereum/src/lib.rs

@@ -796,6 +796,7 @@ impl<T: Config> Pallet<T> {
 			}
 		};
 
+		let is_transactional = true;
 		match action {
 			ethereum::TransactionAction::Call(target) => {
 				let res = T::Runner::call(
@@ -808,6 +809,7 @@ impl<T: Config> Pallet<T> {
 					max_priority_fee_per_gas,
 					nonce,
 					access_list,
+					is_transactional,
 					config.as_ref().unwrap_or(T::config()),
 				)
 				.map_err(Into::into)?;
@@ -824,6 +826,7 @@ impl<T: Config> Pallet<T> {
 					max_priority_fee_per_gas,
 					nonce,
 					access_list,
+					is_transactional,
 					config.as_ref().unwrap_or(T::config()),
 				)
 				.map_err(Into::into)?;

frame/evm/src/benchmarking.rs

@@ -76,6 +76,7 @@ benchmarks! {
 
 		let value = U256::default();
 		let gas_limit_create: u64 = 1_250_000 * 1_000_000_000;
+		let is_transactional = true;
 		let create_runner_results = T::Runner::create(
 			caller,
 			contract_bytecode,
@@ -85,6 +86,7 @@ benchmarks! {
 			None,
 			Some(nonce_as_u256),
 			Vec::new(),
+			is_transactional,
 			T::config(),
 		);
 		assert_eq!(create_runner_results.is_ok(), true, "create() failed");
@@ -106,6 +108,7 @@ benchmarks! {
 		nonce = nonce + 1;
 		let nonce_as_u256: U256 = nonce.into();
 
+		let is_transactional = true;
 		let call_runner_results = T::Runner::call(
 			caller,
 			contract_address,
@@ -116,6 +119,7 @@ benchmarks! {
 			None,
 			Some(nonce_as_u256),
 			Vec::new(),
+			is_transactional,
 			T::config(),
 		);
 		assert_eq!(call_runner_results.is_ok(), true, "call() failed");

frame/evm/src/lib.rs

@@ -192,6 +192,7 @@ pub mod pallet {
 		) -> DispatchResultWithPostInfo {
 			T::CallOrigin::ensure_address_origin(&source, origin)?;
 
+			let is_transactional = true;
 			let info = T::Runner::call(
 				source,
 				target,
@@ -202,6 +203,7 @@ pub mod pallet {
 				max_priority_fee_per_gas,
 				nonce,
 				access_list,
+				is_transactional,
 				T::config(),
 			)?;
 
@@ -238,6 +240,7 @@ pub mod pallet {
 		) -> DispatchResultWithPostInfo {
 			T::CallOrigin::ensure_address_origin(&source, origin)?;
 
+			let is_transactional = true;
 			let info = T::Runner::create(
 				source,
 				init,
@@ -247,6 +250,7 @@ pub mod pallet {
 				max_priority_fee_per_gas,
 				nonce,
 				access_list,
+				is_transactional,
 				T::config(),
 			)?;
 
@@ -291,6 +295,7 @@ pub mod pallet {
 		) -> DispatchResultWithPostInfo {
 			T::CallOrigin::ensure_address_origin(&source, origin)?;
 
+			let is_transactional = true;
 			let info = T::Runner::create2(
 				source,
 				init,
@@ -301,6 +306,7 @@ pub mod pallet {
 				max_priority_fee_per_gas,
 				nonce,
 				access_list,
+				is_transactional,
 				T::config(),
 			)?;
 
@@ -734,6 +740,9 @@ where
 	type LiquidityInfo = Option<NegativeImbalanceOf<C, T>>;
 
 	fn withdraw_fee(who: &H160, fee: U256) -> Result<Self::LiquidityInfo, Error<T>> {
+		if fee.is_zero() {
+			return Ok(None);
+		}
 		let account_id = T::AddressMapping::into_account_id(*who);
 		let imbalance = C::withdraw(
 			&account_id,

frame/evm/src/runner/mod.rs

@@ -35,6 +35,7 @@ pub trait Runner<T: Config> {
 		max_priority_fee_per_gas: Option<U256>,
 		nonce: Option<U256>,
 		access_list: Vec<(H160, Vec<H256>)>,
+		is_transactional: bool,
 		config: &evm::Config,
 	) -> Result<CallInfo, Self::Error>;
 
@@ -47,6 +48,7 @@ pub trait Runner<T: Config> {
 		max_priority_fee_per_gas: Option<U256>,
 		nonce: Option<U256>,
 		access_list: Vec<(H160, Vec<H256>)>,
+		is_transactional: bool,
 		config: &evm::Config,
 	) -> Result<CreateInfo, Self::Error>;
 
@@ -60,6 +62,7 @@ pub trait Runner<T: Config> {
 		max_priority_fee_per_gas: Option<U256>,
 		nonce: Option<U256>,
 		access_list: Vec<(H160, Vec<H256>)>,
+		is_transactional: bool,
 		config: &evm::Config,
 	) -> Result<CreateInfo, Self::Error>;
 }

frame/evm/src/runner/stack.rs

@@ -52,6 +52,7 @@ impl<T: Config> Runner<T> {
 		nonce: Option<U256>,
 		config: &'config evm::Config,
 		precompiles: &'precompiles T::PrecompilesType,
+		is_transactional: bool,
 		f: F,
 	) -> Result<ExecutionInfo<R>, Error<T>>
 	where
@@ -65,21 +66,24 @@ impl<T: Config> Runner<T> {
 		) -> (ExitReason, R),
 	{
 		let base_fee = T::FeeCalculator::min_gas_price();
-
-		let max_fee_per_gas = match (max_fee_per_gas, max_priority_fee_per_gas) {
-			(Some(max_fee_per_gas), Some(max_priority_fee_per_gas)) => {
-				ensure!(max_fee_per_gas >= base_fee, Error::<T>::GasPriceTooLow);
-				ensure!(max_fee_per_gas >= max_priority_fee_per_gas, Error::<T>::GasPriceTooLow);
-				max_fee_per_gas
-			},
-			(Some(max_fee_per_gas), None) => {
+		let max_fee_per_gas = match (max_fee_per_gas, is_transactional) {
+			(Some(max_fee_per_gas), _) => {
 				ensure!(max_fee_per_gas >= base_fee, Error::<T>::GasPriceTooLow);
 				max_fee_per_gas
-			},
-			// Gas price check is skipped when performing a gas estimation.
-			_ => Default::default()
+			}
+			// Gas price check is skipped for non-transactional calls that don't
+			// define a `max_fee_per_gas` input.
+			(None, false) => Default::default(),
+			_ => return Err(Error::<T>::GasPriceTooLow),
 		};
 
+		if let Some(max_priority_fee) = max_priority_fee_per_gas {
+			ensure!(
+				max_fee_per_gas >= max_priority_fee,
+				Error::<T>::GasPriceTooLow
+			);
+		}
+
 		// After eip-1559 we make sure the account can pay both the evm execution and priority fees.
 		let total_fee = max_fee_per_gas
 			.checked_mul(U256::from(gas_limit))
@@ -89,15 +93,22 @@ impl<T: Config> Runner<T> {
 			.checked_add(total_fee)
 			.ok_or(Error::<T>::PaymentOverflow)?;
 		let source_account = Pallet::<T>::account_basic(&source);
-		ensure!(
-			source_account.balance >= total_payment,
-			Error::<T>::BalanceLow
-		);
+		// Account balance check is skipped if fee is Zero.
+		// This case is previously verified to only happen on either:
+		// 	- Non-transactional calls.
+		//	- BaseFee is configured to be Zero.
+		if total_fee > U256::zero() {
+			ensure!(
+				source_account.balance >= total_payment,
+				Error::<T>::BalanceLow
+			);
+		}
 
 		if let Some(nonce) = nonce {
 			ensure!(source_account.nonce == nonce, Error::<T>::InvalidNonce);
 		}
-		// Deduct fee from the `source` account.
+
+		// Deduct fee from the `source` account. Returns `None` if `total_fee` is Zero.
 		let fee = T::OnChargeTransaction::withdraw_fee(&source, total_fee)?;
 
 		// Execute the EVM call.
@@ -131,12 +142,13 @@ impl<T: Config> Runner<T> {
 			};
 		log::debug!(
 			target: "evm",
-			"Execution {:?} [source: {:?}, value: {}, gas_limit: {}, actual_fee: {}]",
+			"Execution {:?} [source: {:?}, value: {}, gas_limit: {}, actual_fee: {}, is_transactional: {}]",
 			reason,
 			source,
 			value,
 			gas_limit,
-			actual_fee
+			actual_fee,
+			is_transactional
 		);
 		// The difference between initially withdrawn and the actual cost is refunded.
 		//
@@ -214,6 +226,7 @@ impl<T: Config> RunnerT<T> for Runner<T> {
 		max_priority_fee_per_gas: Option<U256>,
 		nonce: Option<U256>,
 		access_list: Vec<(H160, Vec<H256>)>,
+		is_transactional: bool,
 		config: &evm::Config,
 	) -> Result<CallInfo, Self::Error> {
 		let precompiles = T::PrecompilesValue::get();
@@ -226,6 +239,7 @@ impl<T: Config> RunnerT<T> for Runner<T> {
 			nonce,
 			config,
 			&precompiles,
+			is_transactional,
 			|executor| executor.transact_call(source, target, value, input, gas_limit, access_list),
 		)
 	}
@@ -239,6 +253,7 @@ impl<T: Config> RunnerT<T> for Runner<T> {
 		max_priority_fee_per_gas: Option<U256>,
 		nonce: Option<U256>,
 		access_list: Vec<(H160, Vec<H256>)>,
+		is_transactional: bool,
 		config: &evm::Config,
 	) -> Result<CreateInfo, Self::Error> {
 		let precompiles = T::PrecompilesValue::get();
@@ -251,6 +266,7 @@ impl<T: Config> RunnerT<T> for Runner<T> {
 			nonce,
 			config,
 			&precompiles,
+			is_transactional,
 			|executor| {
 				let address = executor.create_address(evm::CreateScheme::Legacy { caller: source });
 				(
@@ -271,6 +287,7 @@ impl<T: Config> RunnerT<T> for Runner<T> {
 		max_priority_fee_per_gas: Option<U256>,
 		nonce: Option<U256>,
 		access_list: Vec<(H160, Vec<H256>)>,
+		is_transactional: bool,
 		config: &evm::Config,
 	) -> Result<CreateInfo, Self::Error> {
 		let precompiles = T::PrecompilesValue::get();
@@ -284,6 +301,7 @@ impl<T: Config> RunnerT<T> for Runner<T> {
 			nonce,
 			config,
 			&precompiles,
+			is_transactional,
 			|executor| {
 				let address = executor.create_address(evm::CreateScheme::Create2 {
 					caller: source,