core, eth/downloader: fix validation flaw, fix downloader printout flaw (#17974)

core/block_validator.go

@@ -53,12 +53,6 @@ func (v *BlockValidator) ValidateBody(block *types.Block) error {
 	if v.bc.HasBlockAndState(block.Hash(), block.NumberU64()) {
 		return ErrKnownBlock
 	}
-	if !v.bc.HasBlockAndState(block.ParentHash(), block.NumberU64()-1) {
-		if !v.bc.HasBlock(block.ParentHash(), block.NumberU64()-1) {
-			return consensus.ErrUnknownAncestor
-		}
-		return consensus.ErrPrunedAncestor
-	}
 	// Header validity is known at this point, check the uncles and transactions
 	header := block.Header()
 	if err := v.engine.VerifyUncles(v.bc, block); err != nil {
@@ -70,6 +64,12 @@ func (v *BlockValidator) ValidateBody(block *types.Block) error {
 	if hash := types.DeriveSha(block.Transactions()); hash != header.TxHash {
 		return fmt.Errorf("transaction root hash mismatch: have %x, want %x", hash, header.TxHash)
 	}
+	if !v.bc.HasBlockAndState(block.ParentHash(), block.NumberU64()-1) {
+		if !v.bc.HasBlock(block.ParentHash(), block.NumberU64()-1) {
+			return consensus.ErrUnknownAncestor
+		}
+		return consensus.ErrPrunedAncestor
+	}
 	return nil
 }
 

eth/downloader/downloader.go

@@ -740,6 +740,7 @@ func (d *Downloader) findAncestor(p *peerConnection, height uint64) (uint64, err
 					return 0, errBadPeer
 				}
 				start = check
+				hash = h
 
 			case <-timeout:
 				p.log.Debug("Waiting for search header timed out", "elapsed", ttl)