package mpt import ( "bytes" "encoding/binary" "errors" "fmt" "github.com/nspcc-dev/neo-go/pkg/core/storage" "github.com/nspcc-dev/neo-go/pkg/io" "github.com/nspcc-dev/neo-go/pkg/util" "github.com/nspcc-dev/neo-go/pkg/util/slice" ) var ( // ErrRestoreFailed is returned when replacing HashNode by its "unhashed" // candidate fails. ErrRestoreFailed = errors.New("failed to restore MPT node") errStop = errors.New("stop condition is met") ) // Billet is a part of MPT trie with missing hash nodes that need to be restored. // Billet is based on the following assumptions: // 1. Refcount can only be incremented (we don't change MPT structure during restore, // thus don't need to decrease refcount). // 2. Each time the part of Billet is completely restored, it is collapsed into // HashNode. // 3. Pair (node, path) must be restored only once. It's a duty of MPT pool to manage // MPT paths in order to provide this assumption. type Billet struct { TempStoragePrefix storage.KeyPrefix Store *storage.MemCachedStore root Node mode TrieMode } // NewBillet returns new billet for MPT trie restoring. It accepts a MemCachedStore // to decouple storage errors from logic errors so that all storage errors are // processed during `store.Persist()` at the caller. This also has the benefit, // that every `Put` can be considered an atomic operation. func NewBillet(rootHash util.Uint256, mode TrieMode, prefix storage.KeyPrefix, store *storage.MemCachedStore) *Billet { return &Billet{ TempStoragePrefix: prefix, Store: store, root: NewHashNode(rootHash), mode: mode, } } // RestoreHashNode replaces HashNode located at the provided path by the specified Node // and stores it. It also maintains MPT as small as possible by collapsing those parts // of MPT that have been completely restored. func (b *Billet) RestoreHashNode(path []byte, node Node) error { if _, ok := node.(*HashNode); ok { return fmt.Errorf("%w: unable to restore node into HashNode", ErrRestoreFailed) } if _, ok := node.(EmptyNode); ok { return fmt.Errorf("%w: unable to restore node into EmptyNode", ErrRestoreFailed) } r, err := b.putIntoNode(b.root, path, node) if err != nil { return err } b.root = r // If it's a leaf, then put into temporary contract storage. if leaf, ok := node.(*LeafNode); ok { if b.TempStoragePrefix == 0 { panic("invalid storage prefix") } k := append([]byte{byte(b.TempStoragePrefix)}, fromNibbles(path)...) b.Store.Put(k, leaf.value) } return nil } // putIntoNode puts val with provided path inside curr and returns updated node. // Reference counters are updated for both curr and returned value. func (b *Billet) putIntoNode(curr Node, path []byte, val Node) (Node, error) { switch n := curr.(type) { case *LeafNode: return b.putIntoLeaf(n, path, val) case *BranchNode: return b.putIntoBranch(n, path, val) case *ExtensionNode: return b.putIntoExtension(n, path, val) case *HashNode: return b.putIntoHash(n, path, val) case EmptyNode: return nil, fmt.Errorf("%w: can't modify EmptyNode during restore", ErrRestoreFailed) default: panic("invalid MPT node type") } } func (b *Billet) putIntoLeaf(curr *LeafNode, path []byte, val Node) (Node, error) { if len(path) != 0 { return nil, fmt.Errorf("%w: can't modify LeafNode during restore", ErrRestoreFailed) } if curr.Hash() != val.Hash() { return nil, fmt.Errorf("%w: bad Leaf node hash: expected %s, got %s", ErrRestoreFailed, curr.Hash().StringBE(), val.Hash().StringBE()) } // Once Leaf node is restored, it will be collapsed into HashNode forever, so // there shouldn't be such situation when we try to restore Leaf node. panic("bug: can't restore LeafNode") } func (b *Billet) putIntoBranch(curr *BranchNode, path []byte, val Node) (Node, error) { if len(path) == 0 && curr.Hash().Equals(val.Hash()) { // This node has already been restored, so it's an MPT pool duty to avoid // duplicating restore requests. panic("bug: can't perform restoring of BranchNode twice") } i, path := splitPath(path) r, err := b.putIntoNode(curr.Children[i], path, val) if err != nil { return nil, err } curr.Children[i] = r return b.tryCollapseBranch(curr), nil } func (b *Billet) putIntoExtension(curr *ExtensionNode, path []byte, val Node) (Node, error) { if len(path) == 0 { if curr.Hash() != val.Hash() { return nil, fmt.Errorf("%w: bad Extension node hash: expected %s, got %s", ErrRestoreFailed, curr.Hash().StringBE(), val.Hash().StringBE()) } // This node has already been restored, so it's an MPT pool duty to avoid // duplicating restore requests. panic("bug: can't perform restoring of ExtensionNode twice") } if !bytes.HasPrefix(path, curr.key) { return nil, fmt.Errorf("%w: can't modify ExtensionNode during restore", ErrRestoreFailed) } r, err := b.putIntoNode(curr.next, path[len(curr.key):], val) if err != nil { return nil, err } curr.next = r return b.tryCollapseExtension(curr), nil } func (b *Billet) putIntoHash(curr *HashNode, path []byte, val Node) (Node, error) { // Once a part of MPT Billet is completely restored, it will be collapsed forever, so // it's an MPT pool duty to avoid duplicating restore requests. if len(path) != 0 { return nil, fmt.Errorf("%w: node has already been collapsed", ErrRestoreFailed) } // `curr` hash node can be either of // 1) saved in storage (i.g. if we've already restored node with the same hash from the // other part of MPT), so just add it to local in-memory MPT. // 2) missing from the storage. It's OK because we're syncing MPT state, and the purpose // is to store missing hash nodes. // both cases are OK, but we still need to validate `val` against `curr`. if val.Hash() != curr.Hash() { return nil, fmt.Errorf("%w: can't restore HashNode: expected and actual hashes mismatch (%s vs %s)", ErrRestoreFailed, curr.Hash().StringBE(), val.Hash().StringBE()) } if curr.Collapsed { // This node has already been restored and collapsed, so it's an MPT pool duty to avoid // duplicating restore requests. panic("bug: can't perform restoring of collapsed node") } // We also need to increment refcount in both cases. That's the only place where refcount // is changed during restore process. Also flush right now, because sync process can be // interrupted at any time. b.incrementRefAndStore(val.Hash(), val.Bytes()) if val.Type() == LeafT { return b.tryCollapseLeaf(val.(*LeafNode)), nil } return val, nil } func (b *Billet) incrementRefAndStore(h util.Uint256, bs []byte) { key := makeStorageKey(h) if b.mode.RC() { var ( err error data []byte cnt int32 ) // An item may already be in store. data, err = b.Store.Get(key) if err == nil { cnt = int32(binary.LittleEndian.Uint32(data[len(data)-4:])) } cnt++ if len(data) == 0 { data = append(bs, 1, 0, 0, 0, 0) } binary.LittleEndian.PutUint32(data[len(data)-4:], uint32(cnt)) b.Store.Put(key, data) } else { b.Store.Put(key, bs) } } // Traverse traverses MPT nodes (pre-order) starting from the billet root down // to its children calling `process` for each serialised node until true is // returned from `process` function. It also replaces all HashNodes to their // "unhashed" counterparts until the stop condition is satisfied. func (b *Billet) Traverse(process func(pathToNode []byte, node Node, nodeBytes []byte) bool, ignoreStorageErr bool) error { r, err := b.traverse(b.root, []byte{}, []byte{}, process, ignoreStorageErr, false) if err != nil && !errors.Is(err, errStop) { return err } b.root = r return nil } func (b *Billet) traverse(curr Node, path, from []byte, process func(pathToNode []byte, node Node, nodeBytes []byte) bool, ignoreStorageErr bool, backwards bool) (Node, error) { if _, ok := curr.(EmptyNode); ok { // We're not interested in EmptyNodes, and they do not affect the // traversal process, thus remain them untouched. return curr, nil } if hn, ok := curr.(*HashNode); ok { r, err := b.GetFromStore(hn.Hash()) if err != nil { if ignoreStorageErr && errors.Is(err, storage.ErrKeyNotFound) { return hn, nil } return nil, err } return b.traverse(r, path, from, process, ignoreStorageErr, backwards) } if len(from) == 0 { bytes := slice.Copy(curr.Bytes()) if process(fromNibbles(path), curr, bytes) { return curr, errStop } } switch n := curr.(type) { case *LeafNode: return b.tryCollapseLeaf(n), nil case *BranchNode: var ( startIndex byte endIndex byte = childrenCount cmp = func(i int) bool { return i < int(endIndex) } step = 1 ) if backwards { startIndex, endIndex = lastChild, startIndex cmp = func(i int) bool { return i >= int(endIndex) } step = -1 } if len(from) != 0 { endIndex = lastChild if backwards { endIndex = 0 } startIndex, from = splitPath(from) } for i := int(startIndex); cmp(i); i += step { var newPath []byte if i == lastChild { newPath = path } else { newPath = append(path, byte(i)) } if byte(i) != startIndex { from = []byte{} } r, err := b.traverse(n.Children[i], newPath, from, process, ignoreStorageErr, backwards) if err != nil { if !errors.Is(err, errStop) { return nil, err } n.Children[i] = r return b.tryCollapseBranch(n), err } n.Children[i] = r } return b.tryCollapseBranch(n), nil case *ExtensionNode: if len(from) != 0 && bytes.HasPrefix(from, n.key) { from = from[len(n.key):] } else if len(from) == 0 || bytes.Compare(n.key, from) > 0 { from = []byte{} } else { return b.tryCollapseExtension(n), nil } r, err := b.traverse(n.next, append(path, n.key...), from, process, ignoreStorageErr, backwards) if err != nil && !errors.Is(err, errStop) { return nil, err } n.next = r return b.tryCollapseExtension(n), err default: return nil, ErrNotFound } } func (b *Billet) tryCollapseLeaf(curr *LeafNode) Node { // Leaf can always be collapsed. res := NewHashNode(curr.Hash()) res.Collapsed = true return res } func (b *Billet) tryCollapseExtension(curr *ExtensionNode) Node { if !(curr.next.Type() == HashT && curr.next.(*HashNode).Collapsed) { return curr } res := NewHashNode(curr.Hash()) res.Collapsed = true return res } func (b *Billet) tryCollapseBranch(curr *BranchNode) Node { canCollapse := true for i := 0; i < childrenCount; i++ { if curr.Children[i].Type() == EmptyT { continue } if curr.Children[i].Type() == HashT && curr.Children[i].(*HashNode).Collapsed { continue } canCollapse = false break } if !canCollapse { return curr } res := NewHashNode(curr.Hash()) res.Collapsed = true return res } // GetFromStore returns MPT node from the storage. func (b *Billet) GetFromStore(h util.Uint256) (Node, error) { data, err := b.Store.Get(makeStorageKey(h)) if err != nil { return nil, err } var n NodeObject r := io.NewBinReaderFromBuf(data) n.DecodeBinary(r) if r.Err != nil { return nil, r.Err } if b.mode.RC() { data = data[:len(data)-5] } n.Node.(flushedNode).setCache(data, h) return n.Node, nil }