eth: reset skeleton after chain rewinded

eth/api_backend.go

@@ -63,6 +63,7 @@ func (b *EthAPIBackend) CurrentBlock() *types.Header {
 
 func (b *EthAPIBackend) SetHead(number uint64) {
 	b.eth.handler.downloader.Cancel()
+	b.eth.handler.downloader.ResetSkeleton()
 	b.eth.blockchain.SetHead(number)
 }
 

eth/downloader/downloader.go

@@ -116,6 +116,7 @@ type Downloader struct {
 	// Callbacks
 	dropPeer peerDropFn // Drops a peer for misbehaving
 	badBlock badBlockFn // Reports a block as rejected by the chain
+	success  func()     // Callback to signal successful sync completion
 
 	// Status
 	synchronising atomic.Bool
@@ -237,6 +238,7 @@ func New(stateDb ethdb.Database, mode ethconfig.SyncMode, mux *event.TypeMux, ch
 		chainCutoffNumber: cutoffNumber,
 		chainCutoffHash:   cutoffHash,
 		dropPeer:          dropPeer,
+		success:           success,
 		headerProcCh:      make(chan *headerTask, 1),
 		quitCh:            make(chan struct{}),
 		SnapSyncer:        snap.NewSyncer(stateDb, chain.TrieDB().Scheme()),
@@ -662,6 +664,14 @@ func (d *Downloader) Cancel() {
 	d.blockchain.InterruptInsert(false)
 }
 
+// ResetSkeleton terminates the skeleton syncer and reinitializes it.
+func (d *Downloader) ResetSkeleton() {
+	log.Debug("Resetting skeleton syncer due to chain rewind")
+	d.skeleton.Terminate()
+	rawdb.DeleteSkeletonSyncStatus(d.stateDB)
+	d.skeleton = newSkeleton(d.stateDB, d.peers, d.dropPeer, newBeaconBackfiller(d, d.success))
+}
+
 // Terminate interrupts the downloader, canceling all pending operations.
 // The downloader cannot be reused after calling Terminate.
 func (d *Downloader) Terminate() {

eth/downloader/downloader_test.go

@@ -734,3 +734,46 @@ func testSyncProgress(t *testing.T, protocol uint, mode SyncMode) {
 		t.Fatalf("Failed to sync chain in three seconds")
 	}
 }
+
+// TestSkeletonResetAfterSetHead tests that the skeleton syncer is properly reset
+// when the chain is rewound using SetHead, preventing data inconsistency issues.
+func TestSkeletonResetAfterSetHead(t *testing.T) {
+	tester := newTester(t, ethconfig.SnapSync)
+	defer tester.terminate()
+
+	chain := testChainBase.shorten(800)
+	tester.newPeer("peer", eth.ETH68, chain.blocks[1:])
+
+	if _, err := tester.chain.InsertChain(chain.blocks[1:401]); err != nil {
+		t.Fatalf("Failed to insert chain: %v", err)
+	}
+
+	// Start beacon sync to populate the skeleton
+	header := chain.blocks[400].Header()
+	if err := tester.downloader.BeaconSync(header, header); err != nil {
+		t.Fatalf("Failed to start beacon sync: %v", err)
+	}
+
+	// Wait for the skeleton state
+	time.Sleep(20 * time.Millisecond)
+
+	// Check skeleton sync status exists in database before SetHead
+	if skeleton := rawdb.ReadSkeletonSyncStatus(tester.downloader.stateDB); len(skeleton) == 0 {
+		t.Fatal("Skeleton sync status should exist in database before SetHead")
+	}
+
+	// Simulate chain rewind by calling SetHead
+	tester.downloader.Cancel()
+	tester.downloader.ResetSkeleton()
+	tester.chain.SetHead(200)
+
+	// Verify skeleton sync status was cleared from database
+	if skeleton := rawdb.ReadSkeletonSyncStatus(tester.downloader.stateDB); len(skeleton) != 0 {
+		t.Fatal("Skeleton sync status should be cleared from database after SetHead")
+	}
+
+	// Verify we can start a new sync after reset
+	if err := tester.downloader.BeaconSync(header, header); err != nil {
+		t.Fatalf("Failed to start beacon sync after reset: %v", err)
+	}
+}