eth/protocols/snap: fix the flaws in the snap sync

eth/protocols/snap/sync.go

@@ -1553,6 +1553,12 @@ func (s *Syncer) processAccountResponse(res *accountResponse) {
 	// Ensure that the response doesn't overflow into the subsequent task
 	last := res.task.Last.Big()
 	for i, hash := range res.hashes {
+		// Mark the range complete if the last is already included.
+		// Keep iteration to delete the extra states if exists.
+		if hash.Big().Cmp(last) == 0 {
+			res.cont = false
+			continue
+		}
 		if hash.Big().Cmp(last) > 0 {
 			// Chunk overflown, cut off excess, but also update the boundary nodes
 			for j := i; j < len(res.hashes); j++ {
@@ -1761,6 +1767,12 @@ func (s *Syncer) processStorageResponse(res *storageResponse) {
 				// Ensure the response doesn't overflow into the subsequent task
 				last := res.subTask.Last.Big()
 				for k, hash := range res.hashes[i] {
+					// Mark the range complete if the last is already included.
+					// Keep iteration to delete the extra states if exists.
+					if hash.Big().Cmp(last) == 0 {
+						res.cont = false
+						continue
+					}
 					if hash.Big().Cmp(last) > 0 {
 						// Chunk overflown, cut off excess, but also update the boundary
 						for l := k; l < len(res.hashes[i]); l++ {
@@ -1793,6 +1805,10 @@ func (s *Syncer) processStorageResponse(res *storageResponse) {
 					skipped++
 					continue
 				}
+				if _, err := res.overflow.Get(it.Key()); err == nil {
+					skipped++
+					continue
+				}
 			}
 			// Node is not a boundary, persist to disk
 			batch.Put(it.Key(), it.Value())