Make the max bytes of extra_data configurable

eth/abc.py

@@ -5,6 +5,7 @@
 from typing import (
     Any,
     Callable,
+    ClassVar,
     ContextManager,
     Dict,
     Iterable,
@@ -1358,6 +1359,7 @@ def get_transaction_context(cls,
 class VirtualMachineAPI(ConfigurableAPI):
     fork: str  # noqa: E701  # flake8 bug that's fixed in 3.6.0+
     chaindb: ChainDatabaseAPI
+    extra_data_max_bytes: ClassVar[int]
 
     @abstractmethod
     def __init__(self, header: BlockHeaderAPI, chaindb: ChainDatabaseAPI) -> None:

eth/vm/base.py

@@ -3,6 +3,7 @@
 import logging
 from typing import (
     Any,
+    ClassVar,
     Iterable,
     Iterator,
     Optional,
@@ -90,6 +91,7 @@ class VM(Configurable, VirtualMachineAPI):
         - ``_state_class``: The :class:`~eth.abc.StateAPI` class used by this VM for execution.
     """
     block_class: Type[BlockAPI] = None
+    extra_data_max_bytes: ClassVar[int] = 32
     fork: str = None  # noqa: E701  # flake8 bug that's fixed in 3.6.0+
     chaindb: ChainDatabaseAPI = None
     _state_class: Type[StateAPI] = None
@@ -549,7 +551,11 @@ def validate_block(self, block: BlockAPI) -> None:
             )
 
         if block.is_genesis:
-            validate_length_lte(block.header.extra_data, 32, title="BlockHeader.extra_data")
+            validate_length_lte(
+                block.header.extra_data,
+                self.extra_data_max_bytes,
+                title="BlockHeader.extra_data"
+            )
         else:
             parent_header = get_parent_header(block.header, self.chaindb)
             self.validate_header(block.header, parent_header)
@@ -593,7 +599,8 @@ def validate_header(cls,
             # to validate genesis header, check if it equals canonical header at block number 0
             raise ValidationError("Must have access to parent header to validate current header")
         else:
-            validate_length_lte(header.extra_data, 32, title="BlockHeader.extra_data")
+            validate_length_lte(
+                header.extra_data, cls.extra_data_max_bytes, title="BlockHeader.extra_data")
 
             validate_gas_limit(header.gas_limit, parent_header.gas_limit)
 

newsfragments/1864.feature.rst

@@ -0,0 +1,2 @@
+Make the *max length validation* of the `extra_data` field configurable. The reason for that is that
+different consensus engines such as Clique repurpose this field using different max length limits.