blockchain: more tests for sidechain import, fixes #19105

core/blockchain.go

@@ -588,6 +588,13 @@ func (bc *BlockChain) HasState(hash common.Hash) bool {
 	return err == nil
 }
 
+// IsCanon returns whether the given hash/number is part of the canon chain,
+// irrespective of whether the state has been pruned or not
+func (bc *BlockChain) IsCanon(hash common.Hash, number uint64) bool {
+	canonHash := rawdb.ReadCanonicalHash(bc.db, number)
+	return canonHash != (common.Hash{}) && canonHash == hash
+}
+
 // HasBlockAndState checks if a block and associated state trie is fully present
 // in the database or not, caching it if present.
 func (bc *BlockChain) HasBlockAndState(hash common.Hash, number uint64) bool {
@@ -1084,21 +1091,33 @@ func (bc *BlockChain) InsertChain(chain types.Blocks) (int, error) {
 	if len(chain) == 0 {
 		return 0, nil
 	}
+	// Remove already known canon-blocks
+	var (
+		start       = 0
+		block, prev *types.Block
+	)
+	for start, block = range chain {
+		if !bc.IsCanon(block.Hash(), block.NumberU64()) {
+			break
+		}
+	}
 	// Do a sanity check that the provided chain is actually ordered and linked
-	for i := 1; i < len(chain); i++ {
-		if chain[i].NumberU64() != chain[i-1].NumberU64()+1 || chain[i].ParentHash() != chain[i-1].Hash() {
+	for i := start + 1; i < len(chain); i++ {
+		block = chain[i]
+		prev = chain[i-1]
+		if block.NumberU64() != prev.NumberU64()+1 || block.ParentHash() != prev.Hash() {
 			// Chain broke ancestry, log a message (programming error) and skip insertion
-			log.Error("Non contiguous block insert", "number", chain[i].Number(), "hash", chain[i].Hash(),
-				"parent", chain[i].ParentHash(), "prevnumber", chain[i-1].Number(), "prevhash", chain[i-1].Hash())
+			log.Error("Non contiguous block insert", "number", block.Number(), "hash", block.Hash(),
+				"parent", block.ParentHash(), "prevnumber", prev.Number(), "prevhash", prev.Hash())
 
-			return 0, fmt.Errorf("non contiguous insert: item %d is #%d [%x…], item %d is #%d [%x…] (parent [%x…])", i-1, chain[i-1].NumberU64(),
-				chain[i-1].Hash().Bytes()[:4], i, chain[i].NumberU64(), chain[i].Hash().Bytes()[:4], chain[i].ParentHash().Bytes()[:4])
+			return 0, fmt.Errorf("non contiguous insert: item %d is #%d [%x…], item %d is #%d [%x…] (parent [%x…])", i-1, prev.NumberU64(),
+				prev.Hash().Bytes()[:4], i, block.NumberU64(), block.Hash().Bytes()[:4], block.ParentHash().Bytes()[:4])
 		}
 	}
 	// Pre-checks passed, start the full block imports
 	bc.wg.Add(1)
 	bc.chainmu.Lock()
-	n, events, logs, err := bc.insertChain(chain, true)
+	n, events, logs, err := bc.insertChain(chain[start:], true)
 	bc.chainmu.Unlock()
 	bc.wg.Done()
 

core/blockchain_test.go

@@ -1538,3 +1538,81 @@ func TestLowDiffLongChain(t *testing.T) {
 		header = chain.GetHeader(header.ParentHash, number-1)
 	}
 }
+
+// Tests that importing a sidechain (S), where
+// - S is sidechain, containing blocks [Sn...Sm]
+// - C is canon chain, containing blocks [G..Cn..Cm]
+// - A common ancestor is placed at prune-point + blocksBetweenCommonAncestorAndPruneblock
+// - The sidechain S is prepended with numCanonBlocksInSidechain blocks from the canon chain
+func testSideImport(t *testing.T, numCanonBlocksInSidechain, blocksBetweenCommonAncestorAndPruneblock int) {
+
+	// Generate a canonical chain to act as the main dataset
+	engine := ethash.NewFaker()
+	db := ethdb.NewMemDatabase()
+	genesis := new(Genesis).MustCommit(db)
+
+	// Generate and import the canonical chain
+	blocks, _ := GenerateChain(params.TestChainConfig, genesis, engine, db, 2*triesInMemory, nil)
+	diskdb := ethdb.NewMemDatabase()
+	new(Genesis).MustCommit(diskdb)
+	chain, err := NewBlockChain(diskdb, nil, params.TestChainConfig, engine, vm.Config{}, nil)
+	if err != nil {
+		t.Fatalf("failed to create tester chain: %v", err)
+	}
+	if n, err := chain.InsertChain(blocks); err != nil {
+		t.Fatalf("block %d: failed to insert into chain: %v", n, err)
+	}
+
+	lastPrunedIndex := len(blocks) - triesInMemory - 1
+	lastPrunedBlock := blocks[lastPrunedIndex]
+	firstNonPrunedBlock := blocks[len(blocks)-triesInMemory]
+
+	// Verify pruning of lastPrunedBlock
+	if chain.HasBlockAndState(lastPrunedBlock.Hash(), lastPrunedBlock.NumberU64()) {
+		t.Errorf("Block %d not pruned", lastPrunedBlock.NumberU64())
+	}
+	// Verify firstNonPrunedBlock is not pruned
+	if !chain.HasBlockAndState(firstNonPrunedBlock.Hash(), firstNonPrunedBlock.NumberU64()) {
+		t.Errorf("Block %d pruned", firstNonPrunedBlock.NumberU64())
+	}
+	// Generate the sidechain
+	// First block should be a known block, block after should be a pruned block. So
+	// canon(pruned), side, side...
+
+	// Generate fork chain, make it longer than canon
+	parent := blocks[lastPrunedIndex+blocksBetweenCommonAncestorAndPruneblock]
+	fork, _ := GenerateChain(params.TestChainConfig, parent, engine, db, 2*triesInMemory, func(i int, b *BlockGen) {
+		b.SetCoinbase(common.Address{2})
+	})
+	// Prepend the parent(s)
+	var sidechain []*types.Block
+	for i := numCanonBlocksInSidechain; i > 0; i-- {
+		sidechain = append(sidechain, blocks[len(blocks)-i])
+	}
+	sidechain = append(sidechain, fork...)
+	_, err = chain.InsertChain(sidechain)
+	if err != nil {
+		t.Errorf("Got error, %v", err)
+	}
+	head := chain.CurrentBlock()
+	if got := fork[len(fork)-1].Hash(); got != head.Hash() {
+		t.Fatalf("head wrong, expected %x got %x", head.Hash(), got)
+	}
+}
+
+// Tests that importing a sidechain (S), where
+// - S is sidechain, containing blocks [Sn...Sm]
+// - C is canon chain, containing blocks [G..Cn..Cm]
+// - The common ancestor Cc is pruned
+// - The first block in S: Sn, is == Cn
+// That is: the sidechain for import contains some blocks already present in canon chain.
+// So the blocks are
+// [ Cn, Cn+1, Cc, Sn+3 ... Sm]
+//   ^    ^    ^  pruned
+func TestPrunedImportSide(t *testing.T) {
+	testSideImport(t, 3, 3)
+	testSideImport(t, 3, -3)
+	testSideImport(t, 10, 0)
+	testSideImport(t, 1, 10)
+	testSideImport(t, 1, -10)
+}