wire: add flag bits to PR message

Two new flag fields are introduced to the pair request message, both of which
are application specific and have no meaning to the wire package.  The first
is a Flags field which will be used to describe capabilities that do not
affect the pairing type.  This will be used in the initial release to allow
wallets to advertise support for solving and publishing the factored
polynomial.  While here, a second flags field which affects the pairing
compatibility is also added, as this will aid in any future incompatibility in
the client behavior without disturbing clients who have not upgraded.

wire/message_test.go

@@ -80,7 +80,7 @@ func TestMessage(t *testing.T) {
 	msgReject := NewMsgReject("block", RejectDuplicate, "duplicate block")
 	msgGetInitState := NewMsgGetInitState()
 	msgInitState := NewMsgInitState()
-	msgMixPR, err := NewMsgMixPairReq([33]byte{}, 1, 1, "", 1, 1, 1, 1, []MixPairReqUTXO{}, NewTxOut(0, []byte{}))
+	msgMixPR, err := NewMsgMixPairReq([33]byte{}, 1, 1, "", 1, 1, 1, 1, []MixPairReqUTXO{}, NewTxOut(0, []byte{}), 1, 1)
 	if err != nil {
 		t.Errorf("NewMsgMixPairReq: %v", err)
 	}
@@ -122,7 +122,7 @@ func TestMessage(t *testing.T) {
 		{msgCFTypes, msgCFTypes, pver, MainNet, 26},
 		{msgGetInitState, msgGetInitState, pver, MainNet, 25},
 		{msgInitState, msgInitState, pver, MainNet, 27},
-		{msgMixPR, msgMixPR, pver, MainNet, 165},
+		{msgMixPR, msgMixPR, pver, MainNet, 167},
 		{msgMixKE, msgMixKE, pver, MainNet, 1449},
 		{msgMixCT, msgMixCT, pver, MainNet, 158},
 		{msgMixSR, msgMixSR, pver, MainNet, 161},

wire/msgmixpairreq.go

@@ -68,6 +68,8 @@ type MsgMixPairReq struct {
 	InputValue   int64
 	UTXOs        []MixPairReqUTXO
 	Change       *TxOut
+	Flags        byte
+	PairingFlags byte
 
 	// hash records the hash of the message.  It is a member of the
 	// message for convenience and performance, but is never automatically
@@ -83,7 +85,8 @@ func (msg *MsgMixPairReq) Pairing() ([]byte, error) {
 		VarIntSerializeSize(uint64(len(msg.ScriptClass))) + // Script class
 		len(msg.ScriptClass) +
 		2 + // Tx version
-		4 // Locktime
+		4 + // Locktime
+		1 // Pairing flags
 	w := bytes.NewBuffer(make([]byte, 0, bufLen))
 
 	err := writeElement(w, msg.MixAmount)
@@ -96,7 +99,7 @@ func (msg *MsgMixPairReq) Pairing() ([]byte, error) {
 		return nil, err
 	}
 
-	err = writeElements(w, msg.TxVersion, msg.LockTime)
+	err = writeElements(w, msg.TxVersion, msg.LockTime, msg.PairingFlags)
 	if err != nil {
 		return nil, err
 	}
@@ -209,7 +212,7 @@ func (msg *MsgMixPairReq) BtcDecode(r io.Reader, pver uint32) error {
 		return messageError(op, ErrInvalidMsg, msg)
 	}
 
-	return nil
+	return readElements(r, &msg.Flags, &msg.PairingFlags)
 }
 
 // BtcEncode encodes the receiver to w using the Decred protocol encoding.
@@ -370,6 +373,11 @@ func (msg *MsgMixPairReq) writeMessageNoSignature(op string, w io.Writer, pver u
 		}
 	}
 
+	err = writeElements(w, msg.Flags, msg.PairingFlags)
+	if err != nil {
+		return err
+	}
+
 	return nil
 }
 
@@ -433,7 +441,8 @@ func (msg *MsgMixPairReq) GetRun() uint32 {
 // remaining fields.
 func NewMsgMixPairReq(identity [33]byte, expiry uint32, mixAmount int64,
 	scriptClass string, txVersion uint16, lockTime, messageCount uint32,
-	inputValue int64, utxos []MixPairReqUTXO, change *TxOut) (*MsgMixPairReq, error) {
+	inputValue int64, utxos []MixPairReqUTXO, change *TxOut,
+	flags, pairingFlags byte) (*MsgMixPairReq, error) {
 
 	const op = "NewMsgMixPairReq"
 	lenScriptClass := len(scriptClass)
@@ -466,6 +475,8 @@ func NewMsgMixPairReq(identity [33]byte, expiry uint32, mixAmount int64,
 		InputValue:   inputValue,
 		UTXOs:        utxos,
 		Change:       change,
+		Flags:        flags,
+		PairingFlags: pairingFlags,
 	}
 	return msg, nil
 }

wire/msgmixpairreq_test.go

@@ -25,11 +25,14 @@ type mixPairReqArgs struct {
 	inputValue             int64
 	utxos                  []MixPairReqUTXO
 	change                 *TxOut
+	flags                  byte
+	pairingFlags           byte
 }
 
 func (a *mixPairReqArgs) msg() (*MsgMixPairReq, error) {
 	return NewMsgMixPairReq(a.identity, a.expiry, a.mixAmount, a.scriptClass,
-		a.txVersion, a.lockTime, a.messageCount, a.inputValue, a.utxos, a.change)
+		a.txVersion, a.lockTime, a.messageCount, a.inputValue, a.utxos,
+		a.change, a.flags, a.pairingFlags)
 }
 
 func newMixPairReqArgs() *mixPairReqArgs {
@@ -74,6 +77,8 @@ func newMixPairReqArgs() *mixPairReqArgs {
 	const changeValue = int64(0x1393939393939393)
 	pkScript := repeat(0x94, 25)
 	change := NewTxOut(changeValue, pkScript)
+	flags := byte(0x95)
+	pairingFlags := byte(0x96)
 
 	return &mixPairReqArgs{
 		identity:     id,
@@ -87,6 +92,8 @@ func newMixPairReqArgs() *mixPairReqArgs {
 		inputValue:   inputValue,
 		utxos:        utxos,
 		change:       change,
+		flags:        flags,
+		pairingFlags: pairingFlags,
 	}
 }
 
@@ -154,6 +161,8 @@ func TestMsgMixPairReqWire(t *testing.T) {
 		0x94, 0x94, 0x94, 0x94, 0x94, 0x94, 0x94, 0x94,
 		0x94,
 	}...)
+	expected = append(expected, 0x95) // Flags
+	expected = append(expected, 0x96) // Pairing flags
 
 	expectedSerializationEqual(t, buf.Bytes(), expected)