fix: gloas block validation

Author: ahshum

beacon_chain/gossip_processing/gossip_validation.nim

@@ -432,20 +432,33 @@ template validateBeaconBlockGloas(
       phase0.SignedBeaconBlock | altair.SignedBeaconBlock |
       bellatrix.SignedBeaconBlock | capella.SignedBeaconBlock |
       deneb.SignedBeaconBlock | electra.SignedBeaconBlock |
-      fulu.SignedBeaconBlock): untyped =
+      fulu.SignedBeaconBlock,
+    _: BlockRef): untyped =
   discard
 
 # https://github.com/ethereum/consensus-specs/blob/v1.6.0-beta.1/specs/gloas/p2p-interface.md#beacon_block
 template validateBeaconBlockGloas(
     dag: ChainDAGRef,
-    signed_beacon_block: gloas.SignedBeaconBlock): untyped =
+    signed_beacon_block: gloas.SignedBeaconBlock,
+    parent: BlockRef): untyped =
   template blck: untyped = signed_beacon_block.message
   template bid: untyped = blck.body.signed_execution_payload_bid.message
 
   # If `execution_payload` verification of block's execution payload parent by
   # an execution node **is complete**
-  debugGloasComment("update is_execution_block")
-  if signed_beacon_block.is_execution_block:
+  debugGloasComment("")
+  let isExecutionEnabled =
+    if signed_beacon_block.message.is_execution_block:
+      true
+    else:
+      # If we don't know whether the parent block had execution enabled,
+      # assume it didn't. This way, we don't reject here if the timestamp
+      # is invalid, and let state transition check the timestamp.
+      # This is an edge case, and may be hit in a pathological scenario with
+      # checkpoint sync, because the checkpoint block may be unavailable
+      # and it could already be the parent of the new block before backfill.
+      not dag.loadExecutionBlockHash(parent).get(ZERO_HASH).isZero
+  if isExecutionEnabled:
     # [REJECT] The block's execution payload parent (defined by
     # `bid.parent_block_hash`) passes all validation.
     withState(dag.headState):
@@ -969,7 +982,7 @@ proc validateBeaconBlock*(
 
   dag.validateBeaconBlockDeneb(signed_beacon_block, wallTime)
 
-  dag.validateBeaconBlockGloas(signed_beacon_block)
+  dag.validateBeaconBlockGloas(signed_beacon_block, parent)
 
   # [REJECT] The block is from a higher slot than its parent.
   if not (signed_beacon_block.message.slot > parent.bid.slot):