5.6 KiB
5.6 KiB
EIP-4844 -- Fork Choice
Table of contents
Introduction
This is the modification of the fork choice accompanying the EIP-4844 upgrade.
Containers
BlobsSidecar
class BlobsSidecar(Container):
beacon_block_root: Root
beacon_block_slot: Slot
blobs: List[Blob, MAX_BLOBS_PER_BLOCK]
kzg_aggregated_proof: KZGProof
Helpers
validate_blobs_sidecar
def validate_blobs_sidecar(slot: Slot,
beacon_block_root: Root,
expected_kzg_commitments: Sequence[KZGCommitment],
blobs_sidecar: BlobsSidecar) -> None:
assert slot == blobs_sidecar.beacon_block_slot
assert beacon_block_root == blobs_sidecar.beacon_block_root
blobs = blobs_sidecar.blobs
kzg_aggregated_proof = blobs_sidecar.kzg_aggregated_proof
assert len(expected_kzg_commitments) == len(blobs)
assert verify_aggregate_kzg_proof(blobs, expected_kzg_commitments, kzg_aggregated_proof)
is_data_available
The implementation of is_data_available will become more sophisticated during later scaling upgrades.
Initially, verification requires every verifying actor to retrieve the matching BlobsSidecar,
and validate the sidecar with validate_blobs_sidecar.
The block MUST NOT be considered valid until a valid BlobsSidecar has been downloaded. Blocks that have been previously validated as available SHOULD be considered available even if the associated BlobsSidecar has subsequently been pruned.
def is_data_available(slot: Slot, beacon_block_root: Root, blob_kzg_commitments: Sequence[KZGCommitment]) -> bool:
# `retrieve_blobs_sidecar` is implementation and context dependent, raises an exception if not available.
# Note: the p2p network does not guarantee sidecar retrieval outside of `MIN_EPOCHS_FOR_BLOBS_SIDECARS_REQUESTS`
sidecar = retrieve_blobs_sidecar(slot, beacon_block_root)
# For testing, `retrieve_blobs_sidecar` returns "TEST".
# TODO: Remove it once we have a way to inject `BlobsSidecar` into tests.
if isinstance(sidecar, str):
return True
validate_blobs_sidecar(slot, beacon_block_root, blob_kzg_commitments, sidecar)
return True
Updated fork-choice handlers
on_block
Note: The only modification is the addition of the verification of transition block conditions.
def on_block(store: Store, signed_block: SignedBeaconBlock) -> None:
"""
Run ``on_block`` upon receiving a new block.
"""
block = signed_block.message
# Parent block must be known
assert block.parent_root in store.block_states
# Make a copy of the state to avoid mutability issues
pre_state = copy(store.block_states[block.parent_root])
# Blocks cannot be in the future. If they are, their consideration must be delayed until they are in the past.
assert get_current_slot(store) >= block.slot
# Check that block is later than the finalized epoch slot (optimization to reduce calls to get_ancestor)
finalized_slot = compute_start_slot_at_epoch(store.finalized_checkpoint.epoch)
assert block.slot > finalized_slot
# Check block is a descendant of the finalized block at the checkpoint finalized slot
assert get_ancestor(store, block.parent_root, finalized_slot) == store.finalized_checkpoint.root
# [New in EIP-4844]
# Check if blob data is available
# If not, this block MAY be queued and subsequently considered when blob data becomes available
assert is_data_available(block.slot, hash_tree_root(block), block.body.blob_kzg_commitments)
# Check the block is valid and compute the post-state
state = pre_state.copy()
state_transition(state, signed_block, True)
# Check the merge transition
if is_merge_transition_block(pre_state, block.body):
validate_merge_block(block)
# Add new block to the store
store.blocks[hash_tree_root(block)] = block
# Add new state for this block to the store
store.block_states[hash_tree_root(block)] = state
# Add proposer score boost if the block is timely
time_into_slot = (store.time - store.genesis_time) % SECONDS_PER_SLOT
is_before_attesting_interval = time_into_slot < SECONDS_PER_SLOT // INTERVALS_PER_SLOT
if get_current_slot(store) == block.slot and is_before_attesting_interval:
store.proposer_boost_root = hash_tree_root(block)
# Update justified checkpoint
if state.current_justified_checkpoint.epoch > store.justified_checkpoint.epoch:
if state.current_justified_checkpoint.epoch > store.best_justified_checkpoint.epoch:
store.best_justified_checkpoint = state.current_justified_checkpoint
if should_update_justified_checkpoint(store, state.current_justified_checkpoint):
store.justified_checkpoint = state.current_justified_checkpoint
# Update finalized checkpoint
if state.finalized_checkpoint.epoch > store.finalized_checkpoint.epoch:
store.finalized_checkpoint = state.finalized_checkpoint
store.justified_checkpoint = state.current_justified_checkpoint