Another option, remove optimistic sync assumption

beacon-chain/sync/pending_blocks_queue.go

@@ -153,15 +153,13 @@ func (s *Service) processPendingBlocks(ctx context.Context) error {
 			}
 
 			if err := s.validateBeaconBlock(ctx, b, blkRoot); err != nil {
-				if !errors.Is(ErrOptimisticParent, err) {
-					log.Debugf("Could not validate block from slot %d: %v", b.Block().Slot(), err)
-					s.setBadBlock(ctx, blkRoot)
-					tracing.AnnotateError(span, err)
-					// In the next iteration of the queue, this block will be removed from
-					// the pending queue as it has been marked as a 'bad' block.
-					span.End()
-					continue
-				}
+				log.Debugf("Could not validate block from slot %d: %v", b.Block().Slot(), err)
+				s.setBadBlock(ctx, blkRoot)
+				tracing.AnnotateError(span, err)
+				// In the next iteration of the queue, this block will be removed from
+				// the pending queue as it has been marked as a 'bad' block.
+				span.End()
+				continue
 			}
 
 			if err := s.cfg.chain.ReceiveBlock(ctx, b, blkRoot); err != nil {

beacon-chain/sync/validate_beacon_blocks.go

@@ -26,10 +26,6 @@ import (
 	"go.opencensus.io/trace"
 )
 
-var (
-	ErrOptimisticParent = errors.New("parent of the block is optimistic")
-)
-
 // validateBeaconBlockPubSub checks that the incoming block has a valid BLS signature.
 // Blocks that have already been seen are ignored. If the BLS signature is any valid signature,
 // this method rebroadcasts the message.
@@ -166,11 +162,7 @@ func (s *Service) validateBeaconBlockPubSub(ctx context.Context, pid peer.ID, ms
 
 	err = s.validateBeaconBlock(ctx, blk, blockRoot)
 	if err != nil {
-		// If the parent is optimistic, process the block as usual
-		// This also does not penalize a peer which sends optimistic blocks
-		if !errors.Is(ErrOptimisticParent, err) {
-			return pubsub.ValidationReject, err
-		}
+		return pubsub.ValidationReject, err
 	}
 
 	// Record attribute of valid block.
@@ -230,10 +222,6 @@ func (s *Service) validateBeaconBlock(ctx context.Context, blk block.SignedBeaco
 	}
 
 	if err = s.validateBellatrixBeaconBlock(ctx, parentState, blk.Block()); err != nil {
-		if errors.Is(err, ErrOptimisticParent) {
-			return err
-		}
-		// for other kinds of errors, set this block as a bad block.
 		s.setBadBlock(ctx, blockRoot)
 		return err
 	}
@@ -282,14 +270,6 @@ func (s *Service) validateBellatrixBeaconBlock(ctx context.Context, parentState
 		return errors.New("incorrect timestamp")
 	}
 
-	parentRoot := bytesutil.ToBytes32(blk.ParentRoot())
-	isParentOptimistic, err := s.cfg.chain.IsOptimisticForRoot(ctx, parentRoot)
-	if err != nil {
-		return err
-	}
-	if isParentOptimistic {
-		return ErrOptimisticParent
-	}
 	return nil
 }