[NOD-250] Calculate UTXOCommitment when loading DAG + add UTXOCommitment to getBlockDagInfo (#347)

blockdag/dag.go

@@ -1333,6 +1333,11 @@ func (dag *BlockDAG) BlockConfirmationsByHashNoLock(hash *daghash.Hash) (uint64,
 	return dag.blockConfirmations(node)
 }
 
+// UTXOCommitment returns a commitment to the dag's current UTXOSet
+func (dag *BlockDAG) UTXOCommitment() string {
+	return dag.UTXOSet().UTXOMultiset.Hash().String()
+}
+
 // blockConfirmations returns the current confirmations number of the given node
 // The confirmations number is defined as follows:
 // * If the node is red -> 0

blockdag/dagio.go

@@ -538,7 +538,10 @@ func (dag *BlockDAG) initDAGState() error {
 		}
 
 		// Apply the loaded utxoCollection to the virtual block.
-		dag.virtual.utxoSet.utxoCollection = fullUTXOCollection
+		dag.virtual.utxoSet, err = newFullUTXOSetFromUTXOCollection(fullUTXOCollection)
+		if err != nil {
+			return AssertError(fmt.Sprintf("Error loading UTXOSet: %s", err))
+		}
 
 		// Apply the stored tips to the virtual block.
 		tips := newSet()

blockdag/utxoset.go

@@ -524,6 +524,21 @@ func NewFullUTXOSet() *FullUTXOSet {
 	}
 }
 
+func newFullUTXOSetFromUTXOCollection(collection utxoCollection) (*FullUTXOSet, error) {
+	var err error
+	multiset := btcec.NewMultiset(btcec.S256())
+	for outpoint, utxoEntry := range collection {
+		multiset, err = addUTXOToMultiset(multiset, utxoEntry, &outpoint)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return &FullUTXOSet{
+		utxoCollection: collection,
+		UTXOMultiset:   multiset,
+	}, nil
+}
+
 // diffFrom returns the difference between this utxoSet and another
 // diffFrom can only work when other is a diffUTXOSet, and its base utxoSet is this.
 func (fus *FullUTXOSet) diffFrom(other UTXOSet) (*UTXODiff, error) {

btcjson/dagsvrresults.go

@@ -106,6 +106,7 @@ type GetBlockDAGInfoResult struct {
 	TipHashes            []string                            `json:"tipHashes"`
 	Difficulty           float64                             `json:"difficulty"`
 	MedianTime           int64                               `json:"medianTime"`
+	UTXOCommitment       string                              `json:"utxoCommitment"`
 	VerificationProgress float64                             `json:"verificationProgress,omitempty"`
 	Pruned               bool                                `json:"pruned"`
 	PruneHeight          uint64                              `json:"pruneHeight,omitempty"`

server/rpc/rpcserver.go

@@ -1257,14 +1257,15 @@ func handleGetBlockDAGInfo(s *Server, cmd interface{}, closeChan <-chan struct{}
 	dag := s.cfg.DAG
 
 	dagInfo := &btcjson.GetBlockDAGInfoResult{
-		DAG:           params.Name,
-		Blocks:        dag.BlockCount(),
-		Headers:       dag.BlockCount(),
-		TipHashes:     daghash.Strings(dag.TipHashes()),
-		Difficulty:    getDifficultyRatio(dag.CurrentBits(), params),
-		MedianTime:    dag.CalcPastMedianTime().Unix(),
-		Pruned:        false,
-		Bip9SoftForks: make(map[string]*btcjson.Bip9SoftForkDescription),
+		DAG:            params.Name,
+		Blocks:         dag.BlockCount(),
+		Headers:        dag.BlockCount(),
+		TipHashes:      daghash.Strings(dag.TipHashes()),
+		Difficulty:     getDifficultyRatio(dag.CurrentBits(), params),
+		MedianTime:     dag.CalcPastMedianTime().Unix(),
+		UTXOCommitment: dag.UTXOCommitment(),
+		Pruned:         false,
+		Bip9SoftForks:  make(map[string]*btcjson.Bip9SoftForkDescription),
 	}
 
 	// Finally, query the BIP0009 version bits state for all currently

server/rpc/rpcserverhelp.go

@@ -176,6 +176,7 @@ var helpDescsEnUS = map[string]string{
 	"getBlockDagInfoResult-tipHashes":            "The block hashes for the tips in the DAG",
 	"getBlockDagInfoResult-difficulty":           "The current chain difficulty",
 	"getBlockDagInfoResult-medianTime":           "The median time from the PoV of the best block in the chain",
+	"getBlockDagInfoResult-utxoCommitment":       "Commitment to the dag's UTXOSet",
 	"getBlockDagInfoResult-verificationProgress": "An estimate for how much of the best chain we've verified",
 	"getBlockDagInfoResult-pruned":               "A bool that indicates if the node is pruned or not",
 	"getBlockDagInfoResult-pruneHeight":          "The lowest block retained in the current pruned chain",