Prefer checkpoint cache and NSC over head

beacon-chain/blockchain/process_attestation_helpers.go

@@ -92,10 +92,6 @@ func (s *Service) getRecentPreState(ctx context.Context, c *ethpb.Checkpoint) st
 // getAttPreState retrieves the att pre state by either from the cache or the DB.
 // The caller of this function must have a lock on forkchoice.
 func (s *Service) getAttPreState(ctx context.Context, c *ethpb.Checkpoint) (state.ReadOnlyBeaconState, error) {
-	// If the attestation is recent and canonical we can use the head state to compute the shuffling.
-	if st := s.getRecentPreState(ctx, c); st != nil {
-		return st, nil
-	}
 	// Use a multilock to allow scoped holding of a mutex by a checkpoint root + epoch
 	// allowing us to behave smarter in terms of how this function is used concurrently.
 	epochKey := strconv.FormatUint(uint64(c.Epoch), 10 /* base 10 */)
@@ -128,6 +124,10 @@ func (s *Service) getAttPreState(ctx context.Context, c *ethpb.Checkpoint) (stat
 		}
 		return cachedState, nil
 	}
+	// If the attestation is recent and canonical we can use the head state to compute the shuffling.
+	if st := s.getRecentPreState(ctx, c); st != nil {
+		return st, nil
+	}
 
 	// Do not process attestations for old non viable checkpoints otherwise
 	ok, err := s.cfg.ForkChoiceStore.IsViableForCheckpoint(&forkchoicetypes.Checkpoint{Root: [32]byte(c.Root), Epoch: c.Epoch})

changelog/potuz_prefer_cached_over_head.md

@@ -0,0 +1,2 @@
+### Changed
+- Prefer the cached epoch transition states and the NSC ones over head state for attestation verification.