eth2.0-specs/specs/_features/eipxxxx/fork.md

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# ePBS -- Fork Logic
**Notice**: This document is a work-in-progress for researchers and implementers.
## Table of contents
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- [Introduction](#introduction)
- [Configuration](#configuration)
- [Helper functions](#helper-functions)
- [Misc](#misc)
- [Modified `compute_fork_version`](#modified-compute_fork_version)
- [Fork to EIP-XXXX](#fork-to-eip-xxxx)
- [Fork trigger](#fork-trigger)
- [Upgrading the state](#upgrading-the-state)
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## Introduction
This document describes the process of the EIP-XXXX upgrade.
## Configuration
Warning: this configuration is not definitive.
| Name | Value |
|---------------------| - |
| `EPBS_FORK_VERSION` | `Version('0x06000000')` |
| `EPBS_FORK_EPOCH` | `Epoch(18446744073709551615)` **TBD** |
## Helper functions
### Misc
#### Modified `compute_fork_version`
```python
def compute_fork_version(epoch: Epoch) -> Version:
"""
Return the fork version at the given ``epoch``.
"""
if epoch >= EPBS_FORK_EPOCH:
return EPBS_FORK_VERSION
if epoch >= ELECTRA_FORK_EPOCH:
return ELECTRA_FORK_VERSION
if epoch >= DENEB_FORK_EPOCH:
return DENEB_FORK_VERSION
if epoch >= CAPELLA_FORK_EPOCH:
return CAPELLA_FORK_VERSION
if epoch >= BELLATRIX_FORK_EPOCH:
return BELLATRIX_FORK_VERSION
if epoch >= ALTAIR_FORK_EPOCH:
return ALTAIR_FORK_VERSION
return GENESIS_FORK_VERSION
```
## Fork to EIP-XXXX
### Fork trigger
TBD. This fork is defined for testing purposes, the EIP may be combined with other
consensus-layer upgrade.
For now, we assume the condition will be triggered at epoch `EPBS_FORK_EPOCH`.
### Upgrading the state
If `state.slot % SLOTS_PER_EPOCH == 0` and `compute_epoch_at_slot(state.slot) == EPBS_FORK_EPOCH`,
an irregular state change is made to upgrade to ePBS.
```python
def upgrade_to_epbs(pre: deneb.BeaconState) -> BeaconState:
epoch = deneb.get_current_epoch(pre)
post = BeaconState(
# Versioning
genesis_time=pre.genesis_time,
genesis_validators_root=pre.genesis_validators_root,
slot=pre.slot,
fork=Fork(
previous_version=pre.fork.current_version,
current_version=EPBS_FORK_EPOCH, # [Modified in ePBS]
epoch=epoch,
),
# History
latest_block_header=pre.latest_block_header,
block_roots=pre.block_roots,
state_roots=pre.state_roots,
historical_roots=pre.historical_roots,
# Eth1
eth1_data=pre.eth1_data,
eth1_data_votes=pre.eth1_data_votes,
eth1_deposit_index=pre.eth1_deposit_index,
# Registry
validators=pre.validators,
balances=pre.balances,
# Randomness
randao_mixes=pre.randao_mixes,
# Slashings
slashings=pre.slashings,
# Participation
previous_epoch_participation=pre.previous_epoch_participation,
current_epoch_participation=pre.current_epoch_participation,
# Finality
justification_bits=pre.justification_bits,
previous_justified_checkpoint=pre.previous_justified_checkpoint,
current_justified_checkpoint=pre.current_justified_checkpoint,
finalized_checkpoint=pre.finalized_checkpoint,
# Inactivity
inactivity_scores=pre.inactivity_scores,
# Sync
current_sync_committee=pre.current_sync_committee,
next_sync_committee=pre.next_sync_committee,
# Execution-layer
latest_execution_payload_header=ExecutionPayloadHeader(), # [Modified in EIP-XXXX]
# Withdrawals
next_withdrawal_index=pre.next_withdrawal_index,
next_withdrawal_validator_index=pre.next_withdrawal_validator_index,
# Deep history valid from Capella onwards
historical_summaries=pre.historical_summaries,
# ePBS
latest_block_hash=pre.latest_execution_payload_header.block_hash, # [New in EIP-XXXX]
latest_full_slot=pre.slot, # [New in EIP-XXXX]
last_withdrawals_root=Root(), # [New in EIP-XXXX]
)
return post
```