Merge pull request #2550 from mkalinin/base-fee-type-to-bytes32

Change base_fee_per_gas type to Bytes32

specs/merge/beacon-chain.md

@@ -34,7 +34,6 @@
   - [Block processing](#block-processing)
   - [Execution payload processing](#execution-payload-processing)
     - [`is_valid_gas_limit`](#is_valid_gas_limit)
-    - [`compute_base_fee_per_gas`](#compute_base_fee_per_gas)
     - [`process_execution_payload`](#process_execution_payload)
 - [Testing](#testing)
 
@@ -65,8 +64,6 @@ This patch adds transaction execution to the beacon chain as part of the Merge f
 | `BYTES_PER_LOGS_BLOOM` | `uint64(2**8)` (= 256) |
 | `GAS_LIMIT_DENOMINATOR` | `uint64(2**10)` (= 1,024) |
 | `MIN_GAS_LIMIT` | `uint64(5000)` (= 5,000) |
-| `BASE_FEE_MAX_CHANGE_DENOMINATOR` | `uint64(2**3)` (= 8) |
-| `ELASTICITY_MULTIPLIER` | `uint64(2**1)` (= 2) |
 
 ## Configuration
 
@@ -77,7 +74,7 @@ This patch adds transaction execution to the beacon chain as part of the Merge f
 | Name | Value |
 | - | - |
 | `GENESIS_GAS_LIMIT` | `uint64(30000000)` (= 30,000,000) |
-| `GENESIS_BASE_FEE_PER_GAS` | `uint64(1000000000)` (= 1,000,000,000) |
+| `GENESIS_BASE_FEE_PER_GAS` | `Bytes32('0x00ca9a3b00000000000000000000000000000000000000000000000000000000')` (= 1,000,000,000) |
 
 ## Containers
 
@@ -147,6 +144,8 @@ class BeaconState(Container):
 
 #### `ExecutionPayload`
 
+*Note*: The `base_fee_per_gas` field is serialized in little-endian.
+
 ```python
 class ExecutionPayload(Container):
     # Execution block header fields
@@ -160,7 +159,7 @@ class ExecutionPayload(Container):
     gas_limit: uint64
     gas_used: uint64
     timestamp: uint64
-    base_fee_per_gas: uint64  # base fee introduced in EIP-1559
+    base_fee_per_gas: Bytes32  # base fee introduced in EIP-1559, little-endian serialized
     # Extra payload fields
     block_hash: Hash32  # Hash of execution block
     transactions: List[Transaction, MAX_TRANSACTIONS_PER_PAYLOAD]
@@ -181,7 +180,7 @@ class ExecutionPayloadHeader(Container):
     gas_limit: uint64
     gas_used: uint64
     timestamp: uint64
-    base_fee_per_gas: uint64
+    base_fee_per_gas: Bytes32
     # Extra payload fields
     block_hash: Hash32  # Hash of execution block
     transactions_root: Root
@@ -283,31 +282,6 @@ def is_valid_gas_limit(payload: ExecutionPayload, parent: ExecutionPayloadHeader
     return True
 ```
 
-#### `compute_base_fee_per_gas`
-
-```python
-def compute_base_fee_per_gas(payload: ExecutionPayload, parent: ExecutionPayloadHeader) -> uint64:
-    parent_gas_target = parent.gas_limit // ELASTICITY_MULTIPLIER
-    parent_base_fee_per_gas = parent.base_fee_per_gas
-    parent_gas_used = payload.gas_used
-
-    if parent_gas_used == parent_gas_target:
-        return parent_base_fee_per_gas
-    elif parent_gas_used > parent_gas_target:
-        gas_used_delta = parent_gas_used - parent_gas_target
-        base_fee_per_gas_delta = max(
-            parent_base_fee_per_gas * gas_used_delta // parent_gas_target // BASE_FEE_MAX_CHANGE_DENOMINATOR,
-            1,
-        )
-        return parent_base_fee_per_gas + base_fee_per_gas_delta
-    else:
-        gas_used_delta = parent_gas_target - parent_gas_used
-        base_fee_per_gas_delta = (
-            parent_base_fee_per_gas * gas_used_delta // parent_gas_target // BASE_FEE_MAX_CHANGE_DENOMINATOR
-        )
-        return parent_base_fee_per_gas - base_fee_per_gas_delta  # This subtraction can't underflow
-```
-
 #### `process_execution_payload`
 
 *Note:* This function depends on `process_randao` function call as it retrieves the most recent randao mix from the `state`. Implementations that are considering parallel processing of execution payload with respect to beacon chain state transition function should work around this dependency.
@@ -319,7 +293,6 @@ def process_execution_payload(state: BeaconState, payload: ExecutionPayload, exe
         assert payload.parent_hash == state.latest_execution_payload_header.block_hash
         assert payload.block_number == state.latest_execution_payload_header.block_number + uint64(1)
         assert payload.random == get_randao_mix(state, get_current_epoch(state))
-        assert payload.base_fee_per_gas == compute_base_fee_per_gas(payload, state.latest_execution_payload_header)
         assert is_valid_gas_limit(payload, state.latest_execution_payload_header)
     # Verify timestamp
     assert payload.timestamp == compute_timestamp_at_slot(state, state.slot)

tests/core/pyspec/eth2spec/test/helpers/execution_payload.py

@@ -20,11 +20,10 @@ def build_empty_execution_payload(spec, state, randao_mix=None):
         gas_limit=latest.gas_limit,  # retain same limit
         gas_used=0,  # empty block, 0 gas
         timestamp=timestamp,
-        base_fee_per_gas=spec.uint64(0),
+        base_fee_per_gas=latest.base_fee_per_gas,  # retain same base_fee
         block_hash=spec.Hash32(),
         transactions=empty_txs,
     )
-    payload.base_fee_per_gas = spec.compute_base_fee_per_gas(payload, latest)
     # TODO: real RLP + block hash logic would be nice, requires RLP and keccak256 dependency however.
     payload.block_hash = spec.Hash32(spec.hash(payload.hash_tree_root() + b"FAKE RLP HASH"))