add infrastructure to select fork choice version

To allow testing ethereum/consensus-specs#3466
add support for selecting fork choice version at launch. This means we
can deploy a different logic when `DENEB_FORK_EPOCH != FAR_FUTURE_EPOCH`
that won't be used on Mainnet.

beacon_chain/conf.nim

@@ -29,6 +29,8 @@ import
   ./el/el_conf,
   ./filepath
 
+from fork_choice/fork_choice_types
+  import ForkChoiceVersion
 from consensus_object_pools/block_pools_types_light_client
   import LightClientDataImportMode
 
@@ -632,6 +634,12 @@ type
         desc: "Bandwidth estimate for the node (bits per second)"
         name: "debug-bandwidth-estimate" .}: Option[Natural]
 
+      forkChoiceVersion* {.
+        hidden
+        desc: "Forkchoice version to use. " &
+              "Must be one of: stable"
+        name: "debug-forkchoice-version" .}: Option[ForkChoiceVersion]
+
     of BNStartUpCmd.wallets:
       case walletsCmd* {.command.}: WalletsCmd
       of WalletsCmd.create:

beacon_chain/consensus_object_pools/attestation_pool.nim

@@ -90,14 +90,15 @@ declareGauge attestation_pool_block_attestation_packing_time,
 
 proc init*(T: type AttestationPool, dag: ChainDAGRef,
            quarantine: ref Quarantine,
+           forkChoiceVersion = ForkChoiceVersion.Stable,
            onAttestation: OnAttestationCallback = nil): T =
   ## Initialize an AttestationPool from the dag `headState`
   ## The `finalized_root` works around the finalized_checkpoint of the genesis block
   ## holding a zero_root.
   let finalizedEpochRef = dag.getFinalizedEpochRef()
 
   var forkChoice = ForkChoice.init(
-    finalizedEpochRef, dag.finalizedHead.blck)
+    finalizedEpochRef, dag.finalizedHead.blck, forkChoiceVersion)
 
   # Feed fork choice with unfinalized history - during startup, block pool only
   # keeps track of a single history so we just need to follow it

beacon_chain/fork_choice/fork_choice.nim

@@ -49,11 +49,13 @@ func compute_deltas(
 logScope: topics = "fork_choice"
 
 func init*(
-    T: type ForkChoiceBackend, checkpoints: FinalityCheckpoints): T =
-  T(proto_array: ProtoArray.init(checkpoints))
+    T: type ForkChoiceBackend, checkpoints: FinalityCheckpoints,
+    version: ForkChoiceVersion): T =
+  T(proto_array: ProtoArray.init(checkpoints, version))
 
 proc init*(
-    T: type ForkChoice, epochRef: EpochRef, blck: BlockRef): T =
+    T: type ForkChoice, epochRef: EpochRef, blck: BlockRef,
+    version: ForkChoiceVersion): T =
   ## Initialize a fork choice context for a finalized state - in the finalized
   ## state, the justified and finalized checkpoints are the same, so only one
   ## is used here
@@ -65,8 +67,10 @@ proc init*(
     backend: ForkChoiceBackend.init(
       FinalityCheckpoints(
         justified: checkpoint,
-        finalized: checkpoint)),
+        finalized: checkpoint),
+      version),
     checkpoints: Checkpoints(
+      version: version,
       justified: BalanceCheckpoint(
         checkpoint: checkpoint,
         balances: epochRef.effective_balances),

beacon_chain/fork_choice/fork_choice_types.nim

@@ -29,6 +29,11 @@ import
 # ----------------------------------------------------------------------
 
 type
+  ForkChoiceVersion* {.pure.} = enum
+    ## Controls which version of fork choice to run.
+    Stable = "stable"
+      ## Use current version from stable Ethereum consensus specifications
+
   fcKind* = enum
     ## Fork Choice Error Kinds
     fcFinalizedNodeUnknown
@@ -88,6 +93,7 @@ type
     ## Subtracted from logical index to get the physical index
 
   ProtoArray* = object
+    version*: ForkChoiceVersion
     currentEpoch*: Epoch
     checkpoints*: FinalityCheckpoints
     nodes*: ProtoNodes
@@ -110,6 +116,7 @@ type
     balances*: seq[Gwei]
 
   Checkpoints* = object
+    version*: ForkChoiceVersion
     time*: BeaconTime
     justified*: BalanceCheckpoint
     finalized*: Checkpoint

beacon_chain/fork_choice/proto_array.nim

@@ -90,7 +90,8 @@ func nodeLeadsToViableHead(
 # ----------------------------------------------------------------------
 
 func init*(
-    T: type ProtoArray, checkpoints: FinalityCheckpoints): T =
+    T: type ProtoArray, checkpoints: FinalityCheckpoints,
+    version: ForkChoiceVersion): T =
   let node = ProtoNode(
     bid: BlockId(
       slot: checkpoints.finalized.epoch.start_slot,
@@ -102,7 +103,8 @@ func init*(
     bestChild: none(int),
     bestDescendant: none(int))
 
-  T(checkpoints: checkpoints,
+  T(version: version,
+    checkpoints: checkpoints,
     nodes: ProtoNodes(buf: @[node], offset: 0),
     indices: {node.bid.root: 0}.toTable())
 
@@ -541,7 +543,7 @@ func nodeIsViableForHead(
     correctJustified =
       unrealized.justified.epoch >= self.checkpoints.justified.epoch and
       node.checkpoints.justified.epoch + 2 >= self.currentEpoch
-      
+
   return
     if not correctJustified:
       false

beacon_chain/nimbus_beacon_node.nim

@@ -313,8 +313,8 @@ proc initFullNode(
   let
     quarantine = newClone(
       Quarantine.init())
-    attestationPool = newClone(
-      AttestationPool.init(dag, quarantine, onAttestationReceived))
+    attestationPool = newClone(AttestationPool.init(
+      dag, quarantine, config.forkChoiceVersion.get, onAttestationReceived))
     syncCommitteeMsgPool = newClone(
       SyncCommitteeMsgPool.init(rng, dag.cfg, onSyncContribution))
     lightClientPool = newClone(
@@ -1860,6 +1860,8 @@ proc doRunBeaconNode(config: var BeaconNodeConf, rng: ref HmacDrbgContext) {.rai
   # works
   for node in metadata.bootstrapNodes:
     config.bootstrapNodes.add node
+  if config.forkChoiceVersion.isNone:
+    config.forkChoiceVersion = some(ForkChoiceVersion.Stable)
 
   ## Ctrl+C handling
   proc controlCHandler() {.noconv.} =

beacon_chain/rpc/rest_debug_api.nim

@@ -87,7 +87,9 @@ proc installDebugApiHandlers*(router: var RestRouter, node: BeaconNode) =
 
     var response = GetForkChoiceResponse(
       justified_checkpoint: forkChoice.checkpoints.justified.checkpoint,
-      finalized_checkpoint: forkChoice.checkpoints.finalized)
+      finalized_checkpoint: forkChoice.checkpoints.finalized,
+      extra_data: RestExtraData(
+        version: some($forkChoice.backend.proto_array.version)))
 
     for item in forkChoice.backend.proto_array:
       let

beacon_chain/spec/eth2_apis/rest_types.nim

@@ -712,7 +712,7 @@ type
     extra_data*: Option[RestNodeExtraData]
 
   RestExtraData* = object
-    discard
+    version*: Option[string]
 
   GetForkChoiceResponse* = object
     justified_checkpoint*: Checkpoint

tests/consensus_spec/test_fixture_fork_choice.nim

@@ -123,7 +123,8 @@ proc initialLoad(
     dag = ChainDAGRef.init(
       forkedState[].kind.genesisTestRuntimeConfig, db, validatorMonitor, {})
     fkChoice = newClone(ForkChoice.init(
-      dag.getFinalizedEpochRef(), dag.finalizedHead.blck))
+      dag.getFinalizedEpochRef(), dag.finalizedHead.blck,
+      ForkChoiceVersion.Stable))
 
   (dag, fkChoice)
 

tests/test_keymanager_api.nim

@@ -295,7 +295,8 @@ proc startBeaconNode(basePort: int) {.raises: [CatchableError].} =
     "--keymanager-port=" & $(basePort + PortKind.KeymanagerBN.ord),
     "--keymanager-token-file=" & tokenFilePath,
     "--suggested-fee-recipient=" & $defaultFeeRecipient,
-    "--doppelganger-detection=off"], it))
+    "--doppelganger-detection=off",
+    "--debug-forkchoice-version=stable"], it))
   except Exception as exc: # TODO fix confutils exceptions
     raiseAssert exc.msg