Bellatrix

Author: MegaRedHand

spec/fork.md

@@ -28,6 +28,8 @@ Warning: this configuration is not definitive.
 | - | - |
 | `ALTAIR_FORK_VERSION` | `Version('0x01000000')` |
 | `ALTAIR_FORK_EPOCH` | `Epoch(74240)` (Oct 27, 2021, 10:56:23am UTC) |
+| `BELLATRIX_FORK_VERSION` | `Version('0x02000000')` |
+| `BELLATRIX_FORK_EPOCH` | `Epoch(144896)` (Sept 6, 2022, 11:34:47am UTC) |
 
 ## Helper functions
 
@@ -40,6 +42,8 @@ def compute_fork_version(epoch: Epoch) -> Version:
     """
     Return the fork version at the given ``epoch``.
     """
+    if epoch >= BELLATRIX_FORK_EPOCH:
+        return BELLATRIX_FORK_VERSION
     if epoch >= ALTAIR_FORK_EPOCH:
         return ALTAIR_FORK_VERSION
     return GENESIS_FORK_VERSION
@@ -124,3 +128,71 @@ def upgrade_to_altair(pre: phase0.BeaconState) -> BeaconState:
     post.next_sync_committee = get_next_sync_committee(post)
     return post
 ```
+
+## Fork to Bellatrix
+
+### Fork trigger
+
+TBD. Social consensus, along with state conditions such as epoch boundary, finality, deposits, active validator count, etc. may be part of the decision process to trigger the fork. For now we assume the condition will be triggered at epoch `BELLATRIX_FORK_EPOCH`.
+
+Note that for the pure Bellatrix networks, we don't apply `upgrade_to_bellatrix` since it starts with Bellatrix version logic.
+
+### Upgrading the state
+
+As with the Phase0-to-Altair upgrade, the `state_transition` is modified to upgrade the `BeaconState`.
+The `BeaconState` upgrade runs as part of `process_slots`, slots with missing block proposals do not affect the upgrade time.
+
+If `state.slot % SLOTS_PER_EPOCH == 0` and `compute_epoch_at_slot(state.slot) == BELLATRIX_FORK_EPOCH`, an irregular state change is made to upgrade to Bellatrix.
+The upgrade occurs after the completion of the inner loop of `process_slots` that sets `state.slot` equal to `BELLATRIX_FORK_EPOCH * SLOTS_PER_EPOCH`.
+
+When multiple upgrades are scheduled for the same epoch (common for test-networks),
+all the upgrades run in sequence before resuming the regular state transition.
+
+```python
+def upgrade_to_bellatrix(pre: altair.BeaconState) -> BeaconState:
+    epoch = altair.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=BELLATRIX_FORK_VERSION,
+            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(),
+    )
+
+    return post
+```