op-node/specs: refactor batch queue, add parent_hash to batches, extend testing

op-node/rollup/derive/attributes_queue.go

@@ -2,6 +2,7 @@ package derive
 
 import (
 	"context"
+	"fmt"
 	"io"
 	"time"
 
@@ -63,9 +64,14 @@ func (aq *AttributesQueue) Step(ctx context.Context, outer Progress) error {
 	}
 	batch := aq.batches[0]
 
+	safeL2Head := aq.next.SafeL2Head()
+	// sanity check parent hash
+	if batch.ParentHash != safeL2Head.Hash {
+		return NewCriticalError(fmt.Errorf("valid batch has bad parent hash %s, expected %s", batch.ParentHash, safeL2Head.Hash))
+	}
 	fetchCtx, cancel := context.WithTimeout(ctx, 20*time.Second)
 	defer cancel()
-	attrs, err := PreparePayloadAttributes(fetchCtx, aq.config, aq.dl, aq.next.SafeL2Head(), batch.Timestamp, batch.Epoch())
+	attrs, err := PreparePayloadAttributes(fetchCtx, aq.config, aq.dl, safeL2Head, batch.Timestamp, batch.Epoch())
 	if err != nil {
 		return err
 	}

op-node/rollup/derive/attributes_queue_test.go

@@ -68,6 +68,7 @@ func TestAttributesQueue_Step(t *testing.T) {
 	out.ExpectSafeL2Head(safeHead)
 
 	batch := &BatchData{BatchV1{
+		ParentHash:   safeHead.Hash,
 		EpochNum:     rollup.Epoch(l1Info.InfoNum),
 		EpochHash:    l1Info.InfoHash,
 		Timestamp:    safeHead.Time + cfg.BlockTime,

op-node/rollup/derive/batch.go

@@ -35,9 +35,10 @@ const (
 )
 
 type BatchV1 struct {
-	EpochNum  rollup.Epoch // aka l1 num
-	EpochHash common.Hash  // block hash
-	Timestamp uint64
+	ParentHash common.Hash  // parent L2 block hash
+	EpochNum   rollup.Epoch // aka l1 num
+	EpochHash  common.Hash  // block hash
+	Timestamp  uint64
 	// no feeRecipient address input, all fees go to a L2 contract
 	Transactions []hexutil.Bytes
 }