From c1c0cd040c37f247a2d294ba59e3810ad5043cf5 Mon Sep 17 00:00:00 2001
From: Nishant Das <nishdas93@gmail.com>
Date: Thu, 5 Oct 2023 23:18:53 +0800
Subject: [PATCH] Fix Initial Sync PreProcessing (#13007)

Co-authored-by: prylabs-bulldozer[bot] <58059840+prylabs-bulldozer[bot]@users.noreply.github.com>
---
 beacon-chain/sync/initial-sync/round_robin.go |  6 ++--
 .../sync/initial-sync/round_robin_test.go     | 35 +++++++++++++++++++
 2 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/beacon-chain/sync/initial-sync/round_robin.go b/beacon-chain/sync/initial-sync/round_robin.go
index 8a48e6c0adcd..b77c105f2c6a 100644
--- a/beacon-chain/sync/initial-sync/round_robin.go
+++ b/beacon-chain/sync/initial-sync/round_robin.go
@@ -276,7 +276,8 @@ func validUnprocessed(ctx context.Context, bwb []blocks.BlockWithVerifiedBlobs,
 	for i := range bwb {
 		b := bwb[i].Block
 		if headSlot >= b.Block().Slot() && isProc(ctx, b) {
-			processed = &i
+			val := i
+			processed = &val
 			continue
 		}
 		if i > 0 {
@@ -295,7 +296,8 @@ func validUnprocessed(ctx context.Context, bwb []blocks.BlockWithVerifiedBlobs,
 		maxRoot := maxIncoming.Root()
 		return nil, fmt.Errorf("headSlot:%d, blockSlot:%d , root %#x:%w", headSlot, maxIncoming.Block().Slot(), maxRoot, errBlockAlreadyProcessed)
 	}
-	return bwb[*processed:], nil
+	nonProcessedIdx := *processed + 1
+	return bwb[nonProcessedIdx:], nil
 }
 
 func (s *Service) processBatchedBlocks(ctx context.Context, genesis time.Time,
diff --git a/beacon-chain/sync/initial-sync/round_robin_test.go b/beacon-chain/sync/initial-sync/round_robin_test.go
index f5c7a04548a7..dab0f3a42a4a 100644
--- a/beacon-chain/sync/initial-sync/round_robin_test.go
+++ b/beacon-chain/sync/initial-sync/round_robin_test.go
@@ -667,3 +667,38 @@ func TestService_syncToFinalizedEpoch(t *testing.T) {
 	assert.NoError(t, s.syncToFinalizedEpoch(context.Background(), genesis))
 	assert.LogsContain(t, hook, "Already synced to finalized epoch")
 }
+
+func TestService_ValidUnprocessed(t *testing.T) {
+	beaconDB := dbtest.SetupDB(t)
+	genesisBlk := util.NewBeaconBlock()
+	genesisBlkRoot, err := genesisBlk.Block.HashTreeRoot()
+	require.NoError(t, err)
+	util.SaveBlock(t, context.Background(), beaconDB, genesisBlk)
+
+	var batch []blocks.BlockWithVerifiedBlobs
+	currBlockRoot := genesisBlkRoot
+	for i := primitives.Slot(1); i < 10; i++ {
+		parentRoot := currBlockRoot
+		blk1 := util.NewBeaconBlock()
+		blk1.Block.Slot = i
+		blk1.Block.ParentRoot = parentRoot[:]
+		blk1Root, err := blk1.Block.HashTreeRoot()
+		require.NoError(t, err)
+		util.SaveBlock(t, context.Background(), beaconDB, blk1)
+		wsb, err := blocks.NewSignedBeaconBlock(blk1)
+		require.NoError(t, err)
+		rowsb, err := blocks.NewROBlock(wsb)
+		require.NoError(t, err)
+		batch = append(batch, blocks.BlockWithVerifiedBlobs{Block: rowsb})
+		currBlockRoot = blk1Root
+	}
+
+	retBlocks, err := validUnprocessed(context.Background(), batch, 2, func(ctx context.Context, block blocks.ROBlock) bool {
+		// Ignore first 2 blocks in the batch.
+		return block.Block().Slot() <= 2
+	})
+	require.NoError(t, err)
+
+	// Ensure that the unprocessed batch is returned correctly.
+	assert.Equal(t, len(retBlocks), len(batch)-2)
+}