mempool: add policy config option for transaction version

This commit adds a new option to the mempool’s policy configuration
which determines which transaction versions should be accepted as
standard.

The default version set by the policy within the server is 2; this
allows accepting transactions which have version 2 enabled in order to
utilize the new sequence locks feature.

mempool/mempool.go

@@ -84,6 +84,11 @@ type Config struct {
 // Policy houses the policy (configuration parameters) which is used to
 // control the mempool.
 type Policy struct {
+	// MaxTxVersion is the transaction version that the mempool should
+	// accept.  All transactions above this version are rejected as
+	// non-standard.
+	MaxTxVersion int32
+
 	// DisableRelayPriority defines whether to relay free or low-fee
 	// transactions that do not have enough priority to be relayed.
 	DisableRelayPriority bool
@@ -625,7 +630,8 @@ func (mp *TxPool) maybeAcceptTransaction(tx *btcutil.Tx, isNew, rateLimit, rejec
 	// forbid their acceptance.
 	if !mp.cfg.Policy.AcceptNonStd {
 		err = checkTransactionStandard(tx, nextBlockHeight,
-			medianTimePast, mp.cfg.Policy.MinRelayTxFee)
+			medianTimePast, mp.cfg.Policy.MinRelayTxFee,
+			mp.cfg.Policy.MaxTxVersion)
 		if err != nil {
 			// Attempt to extract a reject code from the error so
 			// it can be retained.  When not possible, fall back to

mempool/mempool_test.go

@@ -312,6 +312,7 @@ func newPoolHarness(chainParams *chaincfg.Params) (*poolHarness, []spendableOutp
 				MaxOrphanTxSize:      1000,
 				MaxSigOpsPerTx:       blockchain.MaxSigOpsPerBlock / 5,
 				MinRelayTxFee:        1000, // 1 Satoshi per byte
+				MaxTxVersion:         1,
 			},
 			ChainParams:      chainParams,
 			FetchUtxoView:    chain.FetchUtxoView,

mempool/policy.go

@@ -252,14 +252,15 @@ func isDust(txOut *wire.TxOut, minRelayTxFee btcutil.Amount) bool {
 // of recognized forms, and not containing "dust" outputs (those that are
 // so small it costs more to process them than they are worth).
 func checkTransactionStandard(tx *btcutil.Tx, height int32,
-	medianTimePast time.Time, minRelayTxFee btcutil.Amount) error {
+	medianTimePast time.Time, minRelayTxFee btcutil.Amount,
+	maxTxVersion int32) error {
 
 	// The transaction must be a currently supported version.
 	msgTx := tx.MsgTx()
-	if msgTx.Version > wire.TxVersion || msgTx.Version < 1 {
+	if msgTx.Version > maxTxVersion || msgTx.Version < 1 {
 		str := fmt.Sprintf("transaction version %d is not in the "+
 			"valid range of %d-%d", msgTx.Version, 1,
-			wire.TxVersion)
+			maxTxVersion)
 		return txRuleError(wire.RejectNonstandard, str)
 	}
 

mempool/policy_test.go

@@ -470,7 +470,7 @@ func TestCheckTransactionStandard(t *testing.T) {
 	for _, test := range tests {
 		// Ensure standardness is as expected.
 		err := checkTransactionStandard(btcutil.NewTx(&test.tx),
-			test.height, pastMedianTime, DefaultMinRelayTxFee)
+			test.height, pastMedianTime, DefaultMinRelayTxFee, 1)
 		if err == nil && test.isStandard {
 			// Test passes since function returned standard for a
 			// transaction which is intended to be standard.

server.go

@@ -2355,6 +2355,7 @@ func newServer(listenAddrs []string, db database.DB, chainParams *chaincfg.Param
 			MaxOrphanTxSize:      defaultMaxOrphanTxSize,
 			MaxSigOpsPerTx:       blockchain.MaxSigOpsPerBlock / 5,
 			MinRelayTxFee:        cfg.minRelayTxFee,
+			MaxTxVersion:         2,
 		},
 		ChainParams:    chainParams,
 		FetchUtxoView:  s.blockManager.chain.FetchUtxoView,