From ebb3fa71f1f3ce1334a8dc8581cf6b194b7b47eb Mon Sep 17 00:00:00 2001
From: terence tsao <terence@prysmaticlabs.com>
Date: Fri, 23 Oct 2020 12:02:20 -0700
Subject: [PATCH] VerifyFinalizedConsistency  - return early when canonical
 (#7628)

Co-authored-by: prylabs-bulldozer[bot] <58059840+prylabs-bulldozer[bot]@users.noreply.github.com>
---
 .../blockchain/process_attestation_test.go    | 30 +++++++++++++++++++
 .../blockchain/receive_attestation.go         |  6 ++++
 2 files changed, 36 insertions(+)

diff --git a/beacon-chain/blockchain/process_attestation_test.go b/beacon-chain/blockchain/process_attestation_test.go
index 0f28ca682..adf9da8c9 100644
--- a/beacon-chain/blockchain/process_attestation_test.go
+++ b/beacon-chain/blockchain/process_attestation_test.go
@@ -545,6 +545,36 @@ func TestVerifyFinalizedConsistency_OK(t *testing.T) {
 	require.NoError(t, err)
 }
 
+func TestVerifyFinalizedConsistency_IsCanonical(t *testing.T) {
+	ctx := context.Background()
+	db, _ := testDB.SetupDB(t)
+
+	cfg := &Config{BeaconDB: db, ForkChoiceStore: protoarray.New(0, 0, [32]byte{})}
+	service, err := NewService(ctx, cfg)
+	require.NoError(t, err)
+
+	b32 := testutil.NewBeaconBlock()
+	b32.Block.Slot = 32
+	r32, err := b32.Block.HashTreeRoot()
+	require.NoError(t, err)
+
+	service.finalizedCheckpt = &ethpb.Checkpoint{Epoch: 1, Root: r32[:]}
+
+	b33 := testutil.NewBeaconBlock()
+	b33.Block.Slot = 33
+	b33.Block.ParentRoot = r32[:]
+	r33, err := b33.Block.HashTreeRoot()
+	require.NoError(t, err)
+
+	require.NoError(t, service.forkChoiceStore.ProcessBlock(ctx, b32.Block.Slot, r32, [32]byte{}, [32]byte{}, 0, 0))
+	require.NoError(t, service.forkChoiceStore.ProcessBlock(ctx, b33.Block.Slot, r33, r32, [32]byte{}, 0, 0))
+
+	_, err = service.forkChoiceStore.Head(ctx, 0, r32, []uint64{}, 0)
+	require.NoError(t, err)
+	err = service.VerifyFinalizedConsistency(context.Background(), r33[:])
+	require.NoError(t, err)
+}
+
 func TestGetAttCheckptInfo(t *testing.T) {
 	ctx := context.Background()
 	db, _ := testDB.SetupDB(t)
diff --git a/beacon-chain/blockchain/receive_attestation.go b/beacon-chain/blockchain/receive_attestation.go
index 6d2816973..5d71969dd 100644
--- a/beacon-chain/blockchain/receive_attestation.go
+++ b/beacon-chain/blockchain/receive_attestation.go
@@ -102,6 +102,12 @@ func (s *Service) VerifyLmdFfgConsistency(ctx context.Context, a *ethpb.Attestat
 // When the input root is not be consistent with finalized store then we know it is not
 // on the finalized check point that leads to current canonical chain and should be rejected accordingly.
 func (s *Service) VerifyFinalizedConsistency(ctx context.Context, root []byte) error {
+	// A canonical root implies the root to has an ancestor that aligns with finalized check point.
+	// In this case, we could exit early to save on additional computation.
+	if s.forkChoiceStore.IsCanonical(bytesutil.ToBytes32(root)) {
+		return nil
+	}
+
 	f := s.FinalizedCheckpt()
 	ss, err := helpers.StartSlot(f.Epoch)
 	if err != nil {