routing: add FetchPayment method to ControlTower

This method is used to fetch a payment and all HTLC attempt that have
been made for that payment. It will both be used to resume inflight
attempts, and to fetch the final outcome of previous attempts.

We also update the the mock control tower to mimic the real control
tower, by letting it track multiple HTLC attempts for a given payment
hash, laying the groundwork for later enabling it for MPP.

routing/control_tower.go

@@ -34,6 +34,10 @@ type ControlTower interface {
 	// FailAttempt marks the given payment attempt failed.
 	FailAttempt(lntypes.Hash, uint64, *channeldb.HTLCFailInfo) error
 
+	// FetchPayment fetches the payment corresponding to the given payment
+	// hash.
+	FetchPayment(paymentHash lntypes.Hash) (*channeldb.MPPayment, error)
+
 	// Fail transitions a payment into the Failed state, and records the
 	// ultimate reason the payment failed. Note that this should only be
 	// called when all active active attempts are already failed. After
@@ -132,6 +136,13 @@ func (p *controlTower) FailAttempt(paymentHash lntypes.Hash,
 	return p.db.FailAttempt(paymentHash, attemptID, failInfo)
 }
 
+// FetchPayment fetches the payment corresponding to the given payment hash.
+func (p *controlTower) FetchPayment(paymentHash lntypes.Hash) (
+	*channeldb.MPPayment, error) {
+
+	return p.db.FetchPayment(paymentHash)
+}
+
 // createSuccessResult creates a success result to send to subscribers.
 func createSuccessResult(htlcs []channeldb.HTLCAttempt) *PaymentResult {
 	// Extract any preimage from the list of HTLCs.

routing/mock_test.go

@@ -188,9 +188,15 @@ type failArgs struct {
 	reason channeldb.FailureReason
 }
 
+type testPayment struct {
+	info     channeldb.PaymentCreationInfo
+	attempts []channeldb.HTLCAttempt
+}
+
 type mockControlTower struct {
-	inflights  map[lntypes.Hash]channeldb.InFlightPayment
+	payments   map[lntypes.Hash]*testPayment
 	successful map[lntypes.Hash]struct{}
+	failed     map[lntypes.Hash]channeldb.FailureReason
 
 	init          chan initArgs
 	register      chan registerArgs
@@ -205,8 +211,9 @@ var _ ControlTower = (*mockControlTower)(nil)
 
 func makeMockControlTower() *mockControlTower {
 	return &mockControlTower{
-		inflights:  make(map[lntypes.Hash]channeldb.InFlightPayment),
+		payments:   make(map[lntypes.Hash]*testPayment),
 		successful: make(map[lntypes.Hash]struct{}),
+		failed:     make(map[lntypes.Hash]channeldb.FailureReason),
 	}
 }
 
@@ -220,18 +227,22 @@ func (m *mockControlTower) InitPayment(phash lntypes.Hash,
 		m.init <- initArgs{c}
 	}
 
+	// Don't allow re-init a successful payment.
 	if _, ok := m.successful[phash]; ok {
-		return fmt.Errorf("already successful")
+		return channeldb.ErrAlreadyPaid
 	}
 
-	_, ok := m.inflights[phash]
-	if ok {
-		return fmt.Errorf("in flight")
+	_, failed := m.failed[phash]
+	_, ok := m.payments[phash]
+
+	// If the payment is known, only allow re-init if failed.
+	if ok && !failed {
+		return channeldb.ErrPaymentInFlight
 	}
 
-	m.inflights[phash] = channeldb.InFlightPayment{
-		Info:     c,
-		Attempts: make([]channeldb.HTLCAttemptInfo, 0),
+	delete(m.failed, phash)
+	m.payments[phash] = &testPayment{
+		info: *c,
 	}
 
 	return nil
@@ -247,13 +258,24 @@ func (m *mockControlTower) RegisterAttempt(phash lntypes.Hash,
 		m.register <- registerArgs{a}
 	}
 
-	p, ok := m.inflights[phash]
-	if !ok {
-		return fmt.Errorf("not in flight")
+	// Cannot register attempts for successful or failed payments.
+	if _, ok := m.successful[phash]; ok {
+		return channeldb.ErrPaymentAlreadySucceeded
 	}
 
-	p.Attempts = append(p.Attempts, *a)
-	m.inflights[phash] = p
+	if _, ok := m.failed[phash]; ok {
+		return channeldb.ErrPaymentAlreadyFailed
+	}
+
+	p, ok := m.payments[phash]
+	if !ok {
+		return channeldb.ErrPaymentNotInitiated
+	}
+
+	p.attempts = append(p.attempts, channeldb.HTLCAttempt{
+		HTLCAttemptInfo: *a,
+	})
+	m.payments[phash] = p
 
 	return nil
 }
@@ -268,9 +290,69 @@ func (m *mockControlTower) SettleAttempt(phash lntypes.Hash,
 		m.success <- successArgs{settleInfo.Preimage}
 	}
 
-	delete(m.inflights, phash)
-	m.successful[phash] = struct{}{}
-	return nil
+	// Only allow setting attempts for payments not yet succeeded or
+	// failed.
+	if _, ok := m.successful[phash]; ok {
+		return channeldb.ErrPaymentAlreadySucceeded
+	}
+
+	if _, ok := m.failed[phash]; ok {
+		return channeldb.ErrPaymentAlreadyFailed
+	}
+
+	p, ok := m.payments[phash]
+	if !ok {
+		return channeldb.ErrPaymentNotInitiated
+	}
+
+	// Find the attempt with this pid, and set the settle info.
+	for i, a := range p.attempts {
+		if a.AttemptID != pid {
+			continue
+		}
+
+		p.attempts[i].Settle = settleInfo
+
+		// Mark the payment successful on first settled attempt.
+		m.successful[phash] = struct{}{}
+		return nil
+	}
+
+	return fmt.Errorf("pid not found")
+}
+
+func (m *mockControlTower) FailAttempt(phash lntypes.Hash, pid uint64,
+	failInfo *channeldb.HTLCFailInfo) error {
+
+	m.Lock()
+	defer m.Unlock()
+
+	// Only allow failing attempts for payments not yet succeeded or
+	// failed.
+	if _, ok := m.successful[phash]; ok {
+		return channeldb.ErrPaymentAlreadySucceeded
+	}
+
+	if _, ok := m.failed[phash]; ok {
+		return channeldb.ErrPaymentAlreadyFailed
+	}
+
+	p, ok := m.payments[phash]
+	if !ok {
+		return channeldb.ErrPaymentNotInitiated
+	}
+
+	// Find the attempt with this pid, and set the failure info.
+	for i, a := range p.attempts {
+		if a.AttemptID != pid {
+			continue
+		}
+
+		p.attempts[i].Failure = failInfo
+		return nil
+	}
+
+	return fmt.Errorf("pid not found")
 }
 
 func (m *mockControlTower) Fail(phash lntypes.Hash,
@@ -283,10 +365,50 @@ func (m *mockControlTower) Fail(phash lntypes.Hash,
 		m.fail <- failArgs{reason}
 	}
 
-	delete(m.inflights, phash)
+	// Cannot fail already successful or failed payments.
+	if _, ok := m.successful[phash]; ok {
+		return channeldb.ErrPaymentAlreadySucceeded
+	}
+
+	if _, ok := m.failed[phash]; ok {
+		return channeldb.ErrPaymentAlreadyFailed
+	}
+
+	if _, ok := m.payments[phash]; !ok {
+		return channeldb.ErrPaymentNotInitiated
+	}
+
+	m.failed[phash] = reason
+
 	return nil
 }
 
+func (m *mockControlTower) FetchPayment(phash lntypes.Hash) (
+	*channeldb.MPPayment, error) {
+
+	m.Lock()
+	defer m.Unlock()
+
+	p, ok := m.payments[phash]
+	if !ok {
+		return nil, channeldb.ErrPaymentNotInitiated
+	}
+
+	mp := &channeldb.MPPayment{
+		Info: &p.info,
+	}
+
+	reason, ok := m.failed[phash]
+	if ok {
+		mp.FailureReason = &reason
+	}
+
+	// Return a copy of the current attempts.
+	mp.HTLCs = append(mp.HTLCs, p.attempts...)
+
+	return mp, nil
+}
+
 func (m *mockControlTower) FetchInFlightPayments() (
 	[]*channeldb.InFlightPayment, error) {
 
@@ -297,8 +419,25 @@ func (m *mockControlTower) FetchInFlightPayments() (
 		m.fetchInFlight <- struct{}{}
 	}
 
+	// In flight are all payments not successful or failed.
 	var fl []*channeldb.InFlightPayment
-	for _, ifl := range m.inflights {
+	for hash, p := range m.payments {
+		if _, ok := m.successful[hash]; ok {
+			continue
+		}
+		if _, ok := m.failed[hash]; ok {
+			continue
+		}
+
+		var attempts []channeldb.HTLCAttemptInfo
+		for _, a := range p.attempts {
+			attempts = append(attempts, a.HTLCAttemptInfo)
+		}
+		ifl := channeldb.InFlightPayment{
+			Info:     &p.info,
+			Attempts: attempts,
+		}
+
 		fl = append(fl, &ifl)
 	}
 
@@ -310,9 +449,3 @@ func (m *mockControlTower) SubscribePayment(paymentHash lntypes.Hash) (
 
 	return false, nil, errors.New("not implemented")
 }
-
-func (m *mockControlTower) FailAttempt(hash lntypes.Hash, pid uint64,
-	failInfo *channeldb.HTLCFailInfo) error {
-
-	return nil
-}