Test and fix miner tip calculation for EIP-1559

Author: carver

eth/abc.py

@@ -2686,6 +2686,18 @@ def get_gas_price(self, transaction: SignedTransactionAPI) -> int:
         """
         ...
 
+    @abstractmethod
+    def get_tip(self, transaction: SignedTransactionAPI) -> int:
+        """
+        Return the gas price that gets allocated to the miner/validator.
+
+        Pre-EIP-1559 that would be the full transaction gas price. After, it
+        would be the tip price (potentially reduced, if the base fee is so high
+        that it surpasses the transaction's maximum gas price after adding the
+        tip).
+        """
+        ...
+
     #
     # Access to account db
     #

eth/vm/forks/london/state.py

@@ -119,8 +119,8 @@ def finalize_computation(
             self.vm_state.delta_balance(computation.msg.sender, gas_refund_amount)
 
         # Miner Fees
-        transaction_fee = \
-            (transaction.gas - gas_remaining - gas_refund) * transaction.max_priority_fee_per_gas
+        gas_used = transaction.gas - gas_remaining - gas_refund
+        transaction_fee = gas_used * self.vm_state.get_tip(transaction)
         self.vm_state.logger.debug2(
             'TRANSACTION FEE: %s -> %s',
             transaction_fee,

eth/vm/state.py

@@ -88,18 +88,27 @@ def difficulty(self) -> int:
     def gas_limit(self) -> int:
         return self.execution_context.gas_limit
 
-    def get_gas_price(self, transaction: SignedTransactionAPI) -> int:
+    def _get_burn_price(self) -> int:
+        """
+        How much of the gas price will be burned?
+        """
         execution_context = self.execution_context
         try:
-            base_gas_price = execution_context.base_fee_per_gas
+            return execution_context.base_fee_per_gas
         except AttributeError:
-            return transaction.gas_price
-        else:
-            effective_price = min(
-                transaction.max_fee_per_gas,
-                transaction.max_priority_fee_per_gas + base_gas_price,
-            )
-            return effective_price
+            return 0
+
+    def get_tip(self, transaction: SignedTransactionAPI) -> int:
+        return min(
+            transaction.max_fee_per_gas - self._get_burn_price(),
+            transaction.max_priority_fee_per_gas,
+        )
+
+    def get_gas_price(self, transaction: SignedTransactionAPI) -> int:
+        return min(
+            transaction.max_fee_per_gas,
+            transaction.max_priority_fee_per_gas + self._get_burn_price(),
+        )
 
     #
     # Access to account db

tests/core/vm/test_rewards.py

@@ -21,8 +21,11 @@
     tangerine_whistle_at,
     constantinople_at,
     petersburg_at,
+    berlin_at,
+    london_at,
     genesis,
 )
+from eth.tools.factories.transaction import new_fee_burn_transaction
 
 
 @pytest.mark.parametrize(
@@ -311,3 +314,53 @@ def test_rewards_nephew_uncle_different_vm(
     # But we also ensure the balance matches the numbers that we calculated on paper
     assert coinbase_balance == to_wei(miner_1_balance, 'ether')
     assert other_miner_balance == to_wei(miner_2_balance, 'ether')
+
+
+@pytest.mark.parametrize(
+    'max_total_price, max_priority_price, expected_miner_tips',
+    (
+        # none of the tip makes it to the miner when the base price matches the txn max price
+        (10 ** 9, 1, 0),
+        # half of this tip makes it to the miner because the base price squeezes the tip
+        (10 ** 9 + 1, 2, 21000),
+        # the full tip makes it to the miner because the txn max price is exactly big enough
+        (10 ** 9 + 1, 1, 21000),
+        # the full tip makes it to the miner, and no more, because the txn max
+        #   price is larger than the sum of the base burn fee and the max tip
+        (10 ** 9 + 2, 1, 21000),
+    ),
+)
+def test_eip1559_txn_rewards(
+        max_total_price,
+        max_priority_price,
+        expected_miner_tips,
+        funded_address,
+        funded_address_private_key):
+
+    chain = build(
+        MiningChain,
+        berlin_at(0),
+        london_at(1),  # Start London at block one to get easy 1gwei base fee
+        disable_pow_check(),
+        genesis(
+            params=dict(gas_limit=10**7),
+            state={funded_address: dict(balance=10**20)},
+        ),
+    )
+    vm = chain.get_vm()
+    txn = new_fee_burn_transaction(
+        vm,
+        from_=funded_address,
+        to=funded_address,
+        private_key=funded_address_private_key,
+        max_priority_fee_per_gas=max_priority_price,
+        max_fee_per_gas=max_total_price,
+    )
+
+    MINER = b'\x0f' * 20
+    original_balance = vm.state.get_balance(MINER)
+    chain.mine_all([txn], coinbase=MINER)
+    new_balance = chain.get_vm().state.get_balance(MINER)
+
+    BLOCK_REWARD = 2 * (10 ** 18)
+    assert original_balance + BLOCK_REWARD + expected_miner_tips == new_balance