Merge pull request #5108 from cfromknecht/sendtoroute-amp

channeldb+invoices: add spontaneous AMP receiving + sending via SendToRoute

channeldb/invoice_test.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"github.com/lightningnetwork/lnd/clock"
+	"github.com/lightningnetwork/lnd/feature"
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/record"
@@ -16,7 +17,15 @@ import (
 
 var (
 	emptyFeatures = lnwire.NewFeatureVector(nil, lnwire.Features)
-	testNow       = time.Unix(1, 0)
+	ampFeatures   = lnwire.NewFeatureVector(
+		lnwire.NewRawFeatureVector(
+			lnwire.TLVOnionPayloadOptional,
+			lnwire.PaymentAddrOptional,
+			lnwire.AMPRequired,
+		),
+		lnwire.Features,
+	)
+	testNow = time.Unix(1, 0)
 )
 
 func randInvoice(value lnwire.MilliSatoshi) (*Invoice, error) {
@@ -1208,23 +1217,30 @@ func TestInvoiceRef(t *testing.T) {
 	// An InvoiceRef by hash should return the provided hash and a nil
 	// payment addr.
 	refByHash := InvoiceRefByHash(payHash)
-	require.Equal(t, payHash, refByHash.PayHash())
+	require.Equal(t, &payHash, refByHash.PayHash())
 	require.Equal(t, (*[32]byte)(nil), refByHash.PayAddr())
 	require.Equal(t, (*[32]byte)(nil), refByHash.SetID())
 
 	// An InvoiceRef by hash and addr should return the payment hash and
 	// payment addr passed to the constructor.
 	refByHashAndAddr := InvoiceRefByHashAndAddr(payHash, payAddr)
-	require.Equal(t, payHash, refByHashAndAddr.PayHash())
+	require.Equal(t, &payHash, refByHashAndAddr.PayHash())
 	require.Equal(t, &payAddr, refByHashAndAddr.PayAddr())
 	require.Equal(t, (*[32]byte)(nil), refByHashAndAddr.SetID())
 
 	// An InvoiceRef by set id should return an empty pay hash, a nil pay
 	// addr, and a reference to the given set id.
 	refBySetID := InvoiceRefBySetID(setID)
-	require.Equal(t, lntypes.Hash{}, refBySetID.PayHash())
+	require.Equal(t, (*lntypes.Hash)(nil), refBySetID.PayHash())
 	require.Equal(t, (*[32]byte)(nil), refBySetID.PayAddr())
 	require.Equal(t, &setID, refBySetID.SetID())
+
+	// An InvoiceRef by pay addr should only return a pay addr, but nil for
+	// pay hash and set id.
+	refByAddr := InvoiceRefByAddr(payAddr)
+	require.Equal(t, (*lntypes.Hash)(nil), refByAddr.PayHash())
+	require.Equal(t, &payAddr, refByAddr.PayAddr())
+	require.Equal(t, (*[32]byte)(nil), refByAddr.SetID())
 }
 
 // TestHTLCSet asserts that HTLCSet returns the proper set of accepted HTLCs
@@ -1366,7 +1382,7 @@ func TestSetIDIndex(t *testing.T) {
 	invoice.AmtPaid = amt
 	invoice.SettleDate = dbInvoice.SettleDate
 	invoice.Htlcs = map[CircuitKey]*InvoiceHTLC{
-		{HtlcID: 0}: makeAMPInvoiceHTLC(amt, *setID, preimage),
+		{HtlcID: 0}: makeAMPInvoiceHTLC(amt, *setID, payHash, &preimage),
 	}
 
 	// We should get back the exact same invoice that we just inserted.
@@ -1406,9 +1422,9 @@ func TestSetIDIndex(t *testing.T) {
 	invoice.AmtPaid += 2 * amt
 	invoice.SettleDate = dbInvoice.SettleDate
 	invoice.Htlcs = map[CircuitKey]*InvoiceHTLC{
-		{HtlcID: 0}: makeAMPInvoiceHTLC(amt, *setID, preimage),
-		{HtlcID: 1}: makeAMPInvoiceHTLC(amt, *setID2, preimage),
-		{HtlcID: 2}: makeAMPInvoiceHTLC(amt, *setID2, preimage),
+		{HtlcID: 0}: makeAMPInvoiceHTLC(amt, *setID, payHash, &preimage),
+		{HtlcID: 1}: makeAMPInvoiceHTLC(amt, *setID2, payHash, nil),
+		{HtlcID: 2}: makeAMPInvoiceHTLC(amt, *setID2, payHash, nil),
 	}
 
 	// We should get back the exact same invoice that we just inserted.
@@ -1452,7 +1468,7 @@ func TestSetIDIndex(t *testing.T) {
 }
 
 func makeAMPInvoiceHTLC(amt lnwire.MilliSatoshi, setID [32]byte,
-	preimage lntypes.Preimage) *InvoiceHTLC {
+	hash lntypes.Hash, preimage *lntypes.Preimage) *InvoiceHTLC {
 
 	return &InvoiceHTLC{
 		Amt:           amt,
@@ -1462,8 +1478,8 @@ func makeAMPInvoiceHTLC(amt lnwire.MilliSatoshi, setID [32]byte,
 		CustomRecords: make(record.CustomSet),
 		AMP: &InvoiceHtlcAMPData{
 			Record:   *record.NewAMP([32]byte{}, setID, 0),
-			Hash:     preimage.Hash(),
-			Preimage: &preimage,
+			Hash:     hash,
+			Preimage: preimage,
 		},
 	}
 }
@@ -1480,18 +1496,23 @@ func updateAcceptAMPHtlc(id uint64, amt lnwire.MilliSatoshi,
 
 		noRecords := make(record.CustomSet)
 
-		var state *InvoiceStateUpdateDesc
+		var (
+			state    *InvoiceStateUpdateDesc
+			preimage *lntypes.Preimage
+		)
 		if accept {
 			state = &InvoiceStateUpdateDesc{
 				NewState: ContractAccepted,
 				SetID:    setID,
 			}
+			pre := *invoice.Terms.PaymentPreimage
+			preimage = &pre
 		}
 
 		ampData := &InvoiceHtlcAMPData{
 			Record:   *record.NewAMP([32]byte{}, *setID, 0),
 			Hash:     invoice.Terms.PaymentPreimage.Hash(),
-			Preimage: invoice.Terms.PaymentPreimage,
+			Preimage: preimage,
 		}
 		update := &InvoiceUpdateDesc{
 			State: state,
@@ -1526,6 +1547,792 @@ func getUpdateInvoiceAMPSettle(setID *[32]byte) InvoiceUpdateCallback {
 	}
 }
 
+// TestUnexpectedInvoicePreimage asserts that legacy or MPP invoices cannot be
+// settled when referenced by payment address only. Since regular or MPP
+// payments do not store the payment hash explicitly (it is stored in the
+// index), this enforces that they can only be updated using a InvoiceRefByHash
+// or InvoiceRefByHashOrAddr.
+func TestUnexpectedInvoicePreimage(t *testing.T) {
+	t.Parallel()
+
+	db, cleanup, err := MakeTestDB()
+	defer cleanup()
+	require.NoError(t, err, "unable to make test db")
+
+	invoice, err := randInvoice(lnwire.MilliSatoshi(100))
+	require.NoError(t, err)
+
+	// Add a random invoice indexed by payment hash and payment addr.
+	paymentHash := invoice.Terms.PaymentPreimage.Hash()
+	_, err = db.AddInvoice(invoice, paymentHash)
+	require.NoError(t, err)
+
+	// Attempt to update the invoice by pay addr only. This will fail since,
+	// in order to settle an MPP invoice, the InvoiceRef must present a
+	// payment hash against which to validate the preimage.
+	_, err = db.UpdateInvoice(
+		InvoiceRefByAddr(invoice.Terms.PaymentAddr),
+		getUpdateInvoice(invoice.Terms.Value),
+	)
+
+	//Assert that we get ErrUnexpectedInvoicePreimage.
+	require.Error(t, ErrUnexpectedInvoicePreimage, err)
+}
+
+type updateHTLCPreimageTestCase struct {
+	name               string
+	settleSamePreimage bool
+	expError           error
+}
+
+// TestUpdateHTLCPreimages asserts various properties of setting HTLC-level
+// preimages on invoice state transitions.
+func TestUpdateHTLCPreimages(t *testing.T) {
+	t.Parallel()
+
+	tests := []updateHTLCPreimageTestCase{
+		{
+			name:               "same preimage on settle",
+			settleSamePreimage: true,
+			expError:           nil,
+		},
+		{
+			name:               "diff preimage on settle",
+			settleSamePreimage: false,
+			expError:           ErrHTLCPreimageAlreadyExists,
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			testUpdateHTLCPreimages(t, test)
+		})
+	}
+}
+
+func testUpdateHTLCPreimages(t *testing.T, test updateHTLCPreimageTestCase) {
+	db, cleanup, err := MakeTestDB()
+	defer cleanup()
+	require.NoError(t, err, "unable to make test db")
+
+	// We'll start out by creating an invoice and writing it to the DB.
+	amt := lnwire.NewMSatFromSatoshis(1000)
+	invoice, err := randInvoice(amt)
+	require.Nil(t, err)
+
+	preimage := *invoice.Terms.PaymentPreimage
+	payHash := preimage.Hash()
+
+	// Set AMP-specific features so that we can settle with HTLC-level
+	// preimages.
+	invoice.Terms.Features = ampFeatures
+
+	_, err = db.AddInvoice(invoice, payHash)
+	require.Nil(t, err)
+
+	setID := &[32]byte{1}
+
+	// Update the invoice with an accepted HTLC that also accepts the
+	// invoice.
+	ref := InvoiceRefByAddr(invoice.Terms.PaymentAddr)
+	dbInvoice, err := db.UpdateInvoice(ref, updateAcceptAMPHtlc(0, amt, setID, true))
+	require.Nil(t, err)
+
+	htlcPreimages := make(map[CircuitKey]lntypes.Preimage)
+	for key := range dbInvoice.Htlcs {
+		// Set the either the same preimage used to accept above, or a
+		// blank preimage depending on the test case.
+		var pre lntypes.Preimage
+		if test.settleSamePreimage {
+			pre = preimage
+		}
+		htlcPreimages[key] = pre
+	}
+
+	updateInvoice := func(invoice *Invoice) (*InvoiceUpdateDesc, error) {
+		update := &InvoiceUpdateDesc{
+			State: &InvoiceStateUpdateDesc{
+				Preimage:      nil,
+				NewState:      ContractSettled,
+				HTLCPreimages: htlcPreimages,
+				SetID:         setID,
+			},
+		}
+
+		return update, nil
+	}
+
+	// Now settle the HTLC set and assert the resulting error.
+	_, err = db.UpdateInvoice(ref, updateInvoice)
+	require.Equal(t, test.expError, err)
+}
+
+type updateHTLCTest struct {
+	name     string
+	input    InvoiceHTLC
+	invState ContractState
+	setID    *[32]byte
+	output   InvoiceHTLC
+	expErr   error
+}
+
+// TestUpdateHTLC asserts the behavior of the updateHTLC method in various
+// scenarios for MPP and AMP.
+func TestUpdateHTLC(t *testing.T) {
+	t.Parallel()
+
+	setID := [32]byte{0x01}
+	ampRecord := record.NewAMP([32]byte{0x02}, setID, 3)
+	preimage := lntypes.Preimage{0x04}
+	hash := preimage.Hash()
+
+	diffSetID := [32]byte{0x05}
+	fakePreimage := lntypes.Preimage{0x06}
+	testAlreadyNow := time.Now()
+
+	tests := []updateHTLCTest{
+		{
+			name: "MPP accept",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP:           nil,
+			},
+			invState: ContractAccepted,
+			setID:    nil,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP:           nil,
+			},
+			expErr: nil,
+		},
+		{
+			name: "MPP settle",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP:           nil,
+			},
+			invState: ContractSettled,
+			setID:    nil,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testNow,
+				Expiry:        40,
+				State:         HtlcStateSettled,
+				CustomRecords: make(record.CustomSet),
+				AMP:           nil,
+			},
+			expErr: nil,
+		},
+		{
+			name: "MPP cancel",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP:           nil,
+			},
+			invState: ContractCanceled,
+			setID:    nil,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testNow,
+				Expiry:        40,
+				State:         HtlcStateCanceled,
+				CustomRecords: make(record.CustomSet),
+				AMP:           nil,
+			},
+			expErr: nil,
+		},
+		{
+			name: "AMP accept missing preimage",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: nil,
+				},
+			},
+			invState: ContractAccepted,
+			setID:    &setID,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: nil,
+				},
+			},
+			expErr: ErrHTLCPreimageMissing,
+		},
+		{
+			name: "AMP accept invalid preimage",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &fakePreimage,
+				},
+			},
+			invState: ContractAccepted,
+			setID:    &setID,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &fakePreimage,
+				},
+			},
+			expErr: ErrHTLCPreimageMismatch,
+		},
+		{
+			name: "AMP accept valid preimage",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			invState: ContractAccepted,
+			setID:    &setID,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			expErr: nil,
+		},
+		{
+			name: "AMP accept valid preimage different htlc set",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			invState: ContractAccepted,
+			setID:    &diffSetID,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			expErr: nil,
+		},
+		{
+			name: "AMP settle missing preimage",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: nil,
+				},
+			},
+			invState: ContractSettled,
+			setID:    &setID,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: nil,
+				},
+			},
+			expErr: ErrHTLCPreimageMissing,
+		},
+		{
+			name: "AMP settle invalid preimage",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &fakePreimage,
+				},
+			},
+			invState: ContractSettled,
+			setID:    &setID,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &fakePreimage,
+				},
+			},
+			expErr: ErrHTLCPreimageMismatch,
+		},
+		{
+			name: "AMP settle valid preimage",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			invState: ContractSettled,
+			setID:    &setID,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testNow,
+				Expiry:        40,
+				State:         HtlcStateSettled,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			expErr: nil,
+		},
+		{
+			name: "AMP settle valid preimage different htlc set",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			invState: ContractSettled,
+			setID:    &diffSetID,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testNow,
+				Expiry:        40,
+				State:         HtlcStateCanceled,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			expErr: nil,
+		},
+		{
+			name: "accept invoice htlc already settled",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testAlreadyNow,
+				Expiry:        40,
+				State:         HtlcStateSettled,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			invState: ContractAccepted,
+			setID:    &setID,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testAlreadyNow,
+				Expiry:        40,
+				State:         HtlcStateSettled,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			expErr: ErrHTLCAlreadySettled,
+		},
+		{
+			name: "cancel invoice htlc already settled",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testAlreadyNow,
+				Expiry:        40,
+				State:         HtlcStateSettled,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			invState: ContractCanceled,
+			setID:    &setID,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testAlreadyNow,
+				Expiry:        40,
+				State:         HtlcStateSettled,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			expErr: ErrHTLCAlreadySettled,
+		},
+		{
+			name: "settle invoice htlc already settled",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testAlreadyNow,
+				Expiry:        40,
+				State:         HtlcStateSettled,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			invState: ContractSettled,
+			setID:    &setID,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testAlreadyNow,
+				Expiry:        40,
+				State:         HtlcStateSettled,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			expErr: nil,
+		},
+		{
+			name: "cancel invoice",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   time.Time{},
+				Expiry:        40,
+				State:         HtlcStateAccepted,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			invState: ContractCanceled,
+			setID:    &setID,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testNow,
+				Expiry:        40,
+				State:         HtlcStateCanceled,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			expErr: nil,
+		},
+		{
+			name: "accept invoice htlc already canceled",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testAlreadyNow,
+				Expiry:        40,
+				State:         HtlcStateCanceled,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			invState: ContractAccepted,
+			setID:    &setID,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testAlreadyNow,
+				Expiry:        40,
+				State:         HtlcStateCanceled,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			expErr: nil,
+		},
+		{
+			name: "cancel invoice htlc already canceled",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testAlreadyNow,
+				Expiry:        40,
+				State:         HtlcStateCanceled,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			invState: ContractCanceled,
+			setID:    &setID,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testAlreadyNow,
+				Expiry:        40,
+				State:         HtlcStateCanceled,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			expErr: nil,
+		},
+		{
+			name: "settle invoice htlc already canceled",
+			input: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testAlreadyNow,
+				Expiry:        40,
+				State:         HtlcStateCanceled,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			invState: ContractSettled,
+			setID:    &setID,
+			output: InvoiceHTLC{
+				Amt:           5000,
+				MppTotalAmt:   5000,
+				AcceptHeight:  100,
+				AcceptTime:    testNow,
+				ResolveTime:   testAlreadyNow,
+				Expiry:        40,
+				State:         HtlcStateCanceled,
+				CustomRecords: make(record.CustomSet),
+				AMP: &InvoiceHtlcAMPData{
+					Record:   *ampRecord,
+					Hash:     hash,
+					Preimage: &preimage,
+				},
+			},
+			expErr: nil,
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			testUpdateHTLC(t, test)
+		})
+	}
+}
+
+func testUpdateHTLC(t *testing.T, test updateHTLCTest) {
+	htlc := test.input.Copy()
+	err := updateHtlc(testNow, htlc, test.invState, test.setID)
+	require.Equal(t, test.expErr, err)
+	require.Equal(t, test.output, *htlc)
+}
+
 // TestDeleteInvoices tests that deleting a list of invoices will succeed
 // if all delete references are valid, or will fail otherwise.
 func TestDeleteInvoices(t *testing.T) {
@@ -1619,3 +2426,30 @@ func TestDeleteInvoices(t *testing.T) {
 	assertInvoiceCount(0)
 
 }
+
+// TestAddInvoiceInvalidFeatureDeps asserts that inserting an invoice with
+// invalid transitive feature dependencies fails with the appropriate error.
+func TestAddInvoiceInvalidFeatureDeps(t *testing.T) {
+	t.Parallel()
+
+	db, cleanup, err := MakeTestDB()
+	require.NoError(t, err, "unable to make test db")
+	defer cleanup()
+
+	invoice, err := randInvoice(500)
+	require.NoError(t, err)
+
+	invoice.Terms.Features = lnwire.NewFeatureVector(
+		lnwire.NewRawFeatureVector(
+			lnwire.TLVOnionPayloadOptional,
+			lnwire.MPPOptional,
+		),
+		lnwire.Features,
+	)
+
+	hash := invoice.Terms.PaymentPreimage.Hash()
+	_, err = db.AddInvoice(invoice, hash)
+	require.Error(t, err, feature.NewErrMissingFeatureDep(
+		lnwire.PaymentAddrOptional,
+	))
+}

channeldb/invoices.go

@@ -6,9 +6,11 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"strings"
 	"time"
 
 	"github.com/lightningnetwork/lnd/channeldb/kvdb"
+	"github.com/lightningnetwork/lnd/feature"
 	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwire"
@@ -115,6 +117,19 @@ var (
 	// match the invoice hash.
 	ErrInvoicePreimageMismatch = errors.New("preimage does not match")
 
+	// ErrHTLCPreimageMissing is returned when trying to accept/settle an
+	// AMP HTLC but the HTLC-level preimage has not been set.
+	ErrHTLCPreimageMissing = errors.New("AMP htlc missing preimage")
+
+	// ErrHTLCPreimageMismatch is returned when trying to accept/settle an
+	// AMP HTLC but the HTLC-level preimage does not satisfying the
+	// HTLC-level payment hash.
+	ErrHTLCPreimageMismatch = errors.New("htlc preimage mismatch")
+
+	// ErrHTLCAlreadySettled is returned when trying to settle an invoice
+	// but HTLC already exists in the settled state.
+	ErrHTLCAlreadySettled = errors.New("htlc already settled")
+
 	// ErrInvoiceHasHtlcs is returned when attempting to insert an invoice
 	// that already has HTLCs.
 	ErrInvoiceHasHtlcs = errors.New("cannot add invoice with htlcs")
@@ -122,6 +137,19 @@ var (
 	// ErrEmptyHTLCSet is returned when attempting to accept or settle and
 	// HTLC set that has no HTLCs.
 	ErrEmptyHTLCSet = errors.New("cannot settle/accept empty HTLC set")
+
+	// ErrUnexpectedInvoicePreimage is returned when an invoice-level
+	// preimage is provided when trying to settle an invoice that shouldn't
+	// have one, e.g. an AMP invoice.
+	ErrUnexpectedInvoicePreimage = errors.New(
+		"unexpected invoice preimage provided on settle",
+	)
+
+	// ErrHTLCPreimageAlreadyExists is returned when trying to set an
+	// htlc-level preimage but one is already known.
+	ErrHTLCPreimageAlreadyExists = errors.New(
+		"htlc-level preimage already exists",
+	)
 )
 
 // ErrDuplicateSetID is an error returned when attempting to adding an AMP HTLC
@@ -198,7 +226,7 @@ type InvoiceRef struct {
 	// payHash is the payment hash of the target invoice. All invoices are
 	// currently indexed by payment hash. This value will be used as a
 	// fallback when no payment address is known.
-	payHash lntypes.Hash
+	payHash *lntypes.Hash
 
 	// payAddr is the payment addr of the target invoice. Newer invoices
 	// (0.11 and up) are indexed by payment address in addition to payment
@@ -220,7 +248,7 @@ type InvoiceRef struct {
 // its payment hash.
 func InvoiceRefByHash(payHash lntypes.Hash) InvoiceRef {
 	return InvoiceRef{
-		payHash: payHash,
+		payHash: &payHash,
 	}
 }
 
@@ -231,11 +259,19 @@ func InvoiceRefByHashAndAddr(payHash lntypes.Hash,
 	payAddr [32]byte) InvoiceRef {
 
 	return InvoiceRef{
-		payHash: payHash,
+		payHash: &payHash,
 		payAddr: &payAddr,
 	}
 }
 
+// InvoiceRefByAddr creates an InvoiceRef that queries the payment addr index
+// for an invoice with the provided payment address.
+func InvoiceRefByAddr(addr [32]byte) InvoiceRef {
+	return InvoiceRef{
+		payAddr: &addr,
+	}
+}
+
 // InvoiceRefBySetID creates an InvoiceRef that queries the set id index for an
 // invoice with the provided setID. If the invoice is not found, the query will
 // not fallback to payHash or payAddr.
@@ -245,9 +281,15 @@ func InvoiceRefBySetID(setID [32]byte) InvoiceRef {
 	}
 }
 
-// PayHash returns the target invoice's payment hash.
-func (r InvoiceRef) PayHash() lntypes.Hash {
-	return r.payHash
+// PayHash returns the optional payment hash of the target invoice.
+//
+// NOTE: This value may be nil.
+func (r InvoiceRef) PayHash() *lntypes.Hash {
+	if r.payHash != nil {
+		hash := *r.payHash
+		return &hash
+	}
+	return nil
 }
 
 // PayAddr returns the optional payment address of the target invoice.
@@ -274,10 +316,17 @@ func (r InvoiceRef) SetID() *[32]byte {
 
 // String returns a human-readable representation of an InvoiceRef.
 func (r InvoiceRef) String() string {
-	if r.payAddr != nil {
-		return fmt.Sprintf("(pay_hash=%v, pay_addr=%x)", r.payHash, *r.payAddr)
+	var ids []string
+	if r.payHash != nil {
+		ids = append(ids, fmt.Sprintf("pay_hash=%v", *r.payHash))
 	}
-	return fmt.Sprintf("(pay_hash=%v)", r.payHash)
+	if r.payAddr != nil {
+		ids = append(ids, fmt.Sprintf("pay_addr=%x", *r.payAddr))
+	}
+	if r.setID != nil {
+		ids = append(ids, fmt.Sprintf("set_id=%x", *r.setID))
+	}
+	return fmt.Sprintf("(%s)", strings.Join(ids, ", "))
 }
 
 // ContractState describes the state the invoice is in.
@@ -499,6 +548,21 @@ type InvoiceHTLC struct {
 	AMP *InvoiceHtlcAMPData
 }
 
+// Copy makes a deep copy of the target InvoiceHTLC.
+func (h *InvoiceHTLC) Copy() *InvoiceHTLC {
+	result := *h
+
+	// Make a copy of the CustomSet map.
+	result.CustomRecords = make(record.CustomSet)
+	for k, v := range h.CustomRecords {
+		result.CustomRecords[k] = v
+	}
+
+	result.AMP = h.AMP.Copy()
+
+	return &result
+}
+
 // IsInHTLCSet returns true if this HTLC is part an HTLC set. If nil is passed,
 // this method returns true if this is an MPP HTLC. Otherwise, it only returns
 // true if the AMP HTLC's set id matches the populated setID.
@@ -616,6 +680,11 @@ type InvoiceStateUpdateDesc struct {
 	// Preimage must be set to the preimage when NewState is settled.
 	Preimage *lntypes.Preimage
 
+	// HTLCPreimages set the HTLC-level preimages stored for AMP HTLCs.
+	// These are only learned when settling the invoice as a whole. Must be
+	// set when settling an invoice with non-nil SetID.
+	HTLCPreimages map[CircuitKey]lntypes.Preimage
+
 	// SetID identifies a specific set of HTLCs destined for the same
 	// invoice as part of a larger AMP payment. This value will be nil for
 	// legacy or MPP payments.
@@ -645,7 +714,17 @@ func validateInvoice(i *Invoice, paymentHash lntypes.Hash) error {
 		return errors.New("invoice must have a feature vector")
 	}
 
-	if i.Terms.PaymentPreimage == nil && !i.HodlInvoice {
+	err := feature.ValidateDeps(i.Terms.Features)
+	if err != nil {
+		return err
+	}
+
+	// AMP invoices and hodl invoices are allowed to have no preimage
+	// specified.
+	isAMP := i.Terms.Features.HasFeature(
+		lnwire.AMPOptional,
+	)
+	if i.Terms.PaymentPreimage == nil && !(i.HodlInvoice || isAMP) {
 		return errors.New("non-hodl invoices must have a preimage")
 	}
 
@@ -879,19 +958,27 @@ func fetchInvoiceNumByRef(invoiceIndex, payAddrIndex, setIDIndex kvdb.RBucket,
 	payHash := ref.PayHash()
 	payAddr := ref.PayAddr()
 
-	var (
-		invoiceNumByHash = invoiceIndex.Get(payHash[:])
-		invoiceNumByAddr []byte
-	)
-	if payAddr != nil {
-		// Only allow lookups for payment address if it is not a blank
-		// payment address, which is a special-cased value for legacy
-		// keysend invoices.
-		if *payAddr != BlankPayAddr {
-			invoiceNumByAddr = payAddrIndex.Get(payAddr[:])
+	getInvoiceNumByHash := func() []byte {
+		if payHash != nil {
+			return invoiceIndex.Get(payHash[:])
 		}
+		return nil
 	}
 
+	getInvoiceNumByAddr := func() []byte {
+		if payAddr != nil {
+			// Only allow lookups for payment address if it is not a
+			// blank payment address, which is a special-cased value
+			// for legacy keysend invoices.
+			if *payAddr != BlankPayAddr {
+				return payAddrIndex.Get(payAddr[:])
+			}
+		}
+		return nil
+	}
+
+	invoiceNumByHash := getInvoiceNumByHash()
+	invoiceNumByAddr := getInvoiceNumByAddr()
 	switch {
 
 	// If payment address and payment hash both reference an existing
@@ -903,6 +990,10 @@ func fetchInvoiceNumByRef(invoiceIndex, payAddrIndex, setIDIndex kvdb.RBucket,
 
 		return invoiceNumByAddr, nil
 
+	// Return invoices by payment addr only.
+	case invoiceNumByAddr != nil:
+		return invoiceNumByAddr, nil
+
 	// If we were only able to reference the invoice by hash, return the
 	// corresponding invoice number. This can happen when no payment address
 	// was provided, or if it didn't match anything in our records.
@@ -1684,21 +1775,6 @@ func copySlice(src []byte) []byte {
 	return dest
 }
 
-// copyInvoiceHTLC makes a deep copy of the supplied invoice HTLC.
-func copyInvoiceHTLC(src *InvoiceHTLC) *InvoiceHTLC {
-	result := *src
-
-	// Make a copy of the CustomSet map.
-	result.CustomRecords = make(record.CustomSet)
-	for k, v := range src.CustomRecords {
-		result.CustomRecords[k] = v
-	}
-
-	result.AMP = src.AMP.Copy()
-
-	return &result
-}
-
 // copyInvoice makes a deep copy of the supplied invoice.
 func copyInvoice(src *Invoice) *Invoice {
 	dest := Invoice{
@@ -1725,7 +1801,7 @@ func copyInvoice(src *Invoice) *Invoice {
 	}
 
 	for k, v := range src.Htlcs {
-		dest.Htlcs[k] = copyInvoiceHTLC(v)
+		dest.Htlcs[k] = v.Copy()
 	}
 
 	return &dest
@@ -1733,7 +1809,7 @@ func copyInvoice(src *Invoice) *Invoice {
 
 // updateInvoice fetches the invoice, obtains the update descriptor from the
 // callback and applies the updates in a single db transaction.
-func (d *DB) updateInvoice(hash lntypes.Hash, invoices,
+func (d *DB) updateInvoice(hash *lntypes.Hash, invoices,
 	settleIndex, setIDIndex kvdb.RwBucket, invoiceNum []byte,
 	callback InvoiceUpdateCallback) (*Invoice, error) {
 
@@ -1867,7 +1943,25 @@ func (d *DB) updateInvoice(hash lntypes.Hash, invoices,
 	// the process by updating the state transitions for individual HTLCs
 	// and recalculate the total amount paid to the invoice.
 	var amtPaid lnwire.MilliSatoshi
-	for _, htlc := range invoice.Htlcs {
+	for key, htlc := range invoice.Htlcs {
+		// Set the HTLC preimage for any AMP HTLCs.
+		if setID != nil {
+			preimage, ok := update.State.HTLCPreimages[key]
+			switch {
+
+			// If we don't already have a preiamge for this HTLC, we
+			// can set it now.
+			case ok && htlc.AMP.Preimage == nil:
+				htlc.AMP.Preimage = &preimage
+
+			// Otherwise, prevent over-writing an existing preimage.
+			// Ignore the case where the preimage is identical.
+			case ok && *htlc.AMP.Preimage != preimage:
+				return nil, ErrHTLCPreimageAlreadyExists
+
+			}
+		}
+
 		// The invoice state may have changed and this could have
 		// implications for the states of the individual htlcs. Align
 		// the htlc state with the current invoice state.
@@ -1901,7 +1995,7 @@ func (d *DB) updateInvoice(hash lntypes.Hash, invoices,
 }
 
 // updateInvoiceState validates and processes an invoice state update.
-func updateInvoiceState(invoice *Invoice, hash lntypes.Hash,
+func updateInvoiceState(invoice *Invoice, hash *lntypes.Hash,
 	update InvoiceStateUpdateDesc) error {
 
 	// Returning to open is never allowed from any state.
@@ -1950,9 +2044,14 @@ func updateInvoiceState(invoice *Invoice, hash lntypes.Hash,
 
 		switch {
 
+		// If an invoice-level preimage was supplied, but the InvoiceRef
+		// doesn't specify a hash (e.g. AMP invoices) we fail.
+		case update.Preimage != nil && hash == nil:
+			return ErrUnexpectedInvoicePreimage
+
 		// Validate the supplied preimage for non-AMP invoices.
 		case update.Preimage != nil:
-			if update.Preimage.Hash() != hash {
+			if update.Preimage.Hash() != *hash {
 				return ErrInvoicePreimageMismatch
 			}
 			invoice.Terms.PaymentPreimage = update.Preimage
@@ -2027,10 +2126,25 @@ func updateHtlc(resolveTime time.Time, htlc *InvoiceHTLC,
 			// already know the preimage is valid due to checks at
 			// the invoice level. For AMP HTLCs, verify that the
 			// per-HTLC preimage-hash pair is valid.
-			if setID != nil && !htlc.AMP.Preimage.Matches(htlc.AMP.Hash) {
-				return fmt.Errorf("AMP preimage mismatch, "+
-					"preimage=%v hash=%v", *htlc.AMP.Preimage,
-					htlc.AMP.Hash)
+			switch {
+
+			// Non-AMP HTLCs can be settle immediately since we
+			// already know the preimage is valid due to checks at
+			// the invoice level.
+			case setID == nil:
+
+			// At this popint, the setID is non-nil, meaning this is
+			// an AMP HTLC. We know that htlc.AMP cannot be nil,
+			// otherwise IsInHTLCSet would have returned false.
+			//
+			// Fail if an accepted AMP HTLC has no preimage.
+			case htlc.AMP.Preimage == nil:
+				return ErrHTLCPreimageMissing
+
+			// Fail if the accepted AMP HTLC has an invalid
+			// preimage.
+			case !htlc.AMP.Preimage.Matches(htlc.AMP.Hash):
+				return ErrHTLCPreimageMismatch
 			}
 
 			htlcState = HtlcStateSettled
@@ -2059,8 +2173,7 @@ func updateHtlc(resolveTime time.Time, htlc *InvoiceHTLC,
 	// We should never find a settled HTLC on an invoice that isn't in
 	// ContractSettled.
 	if htlc.State == HtlcStateSettled {
-		return fmt.Errorf("cannot have a settled htlc with "+
-			"invoice in state %v", invState)
+		return ErrHTLCAlreadySettled
 	}
 
 	switch invState {

feature/default_sets.go

@@ -51,4 +51,9 @@ var defaultSetDesc = setDesc{
 		SetInit:    {}, // I
 		SetNodeAnn: {}, // N
 	},
+	lnwire.AMPOptional: {
+		SetInit:    {}, // I
+		SetNodeAnn: {}, // N
+		SetInvoice: {}, // 9
+	},
 }

feature/deps.go

@@ -58,6 +58,9 @@ var deps = depDesc{
 	lnwire.AnchorsOptional: {
 		lnwire.StaticRemoteKeyOptional: {},
 	},
+	lnwire.AMPOptional: {
+		lnwire.PaymentAddrOptional: {},
+	},
 }
 
 // ValidateDeps asserts that a feature vector sets all features and their

feature/manager.go

@@ -77,6 +77,8 @@ func newManager(cfg Config, desc setDesc) (*Manager, error) {
 			raw.Unset(lnwire.PaymentAddrRequired)
 			raw.Unset(lnwire.MPPOptional)
 			raw.Unset(lnwire.MPPRequired)
+			raw.Unset(lnwire.AMPOptional)
+			raw.Unset(lnwire.AMPRequired)
 		}
 		if cfg.NoStaticRemoteKey {
 			raw.Unset(lnwire.StaticRemoteKeyOptional)

htlcswitch/hop/payload.go

@@ -119,6 +119,7 @@ func NewPayloadFromReader(r io.Reader) (*Payload, error) {
 		amt  uint64
 		cltv uint32
 		mpp  = &record.MPP{}
+		amp  = &record.AMP{}
 	)
 
 	tlvStream, err := tlv.NewStream(
@@ -126,6 +127,7 @@ func NewPayloadFromReader(r io.Reader) (*Payload, error) {
 		record.NewLockTimeRecord(&cltv),
 		record.NewNextHopIDRecord(&cid),
 		mpp.Record(),
+		amp.Record(),
 	)
 	if err != nil {
 		return nil, err
@@ -160,6 +162,12 @@ func NewPayloadFromReader(r io.Reader) (*Payload, error) {
 		mpp = nil
 	}
 
+	// If no AMP field was parsed, set the MPP field on the resulting
+	// payload to nil.
+	if _, ok := parsedTypes[record.AMPOnionType]; !ok {
+		amp = nil
+	}
+
 	// Filter out the custom records.
 	customRecords := NewCustomRecords(parsedTypes)
 
@@ -171,6 +179,7 @@ func NewPayloadFromReader(r io.Reader) (*Payload, error) {
 			OutgoingCTLV:    cltv,
 		},
 		MPP:           mpp,
+		AMP:           amp,
 		customRecords: customRecords,
 	}, nil
 }
@@ -207,6 +216,7 @@ func ValidateParsedPayloadTypes(parsedTypes tlv.TypeMap,
 	_, hasLockTime := parsedTypes[record.LockTimeOnionType]
 	_, hasNextHop := parsedTypes[record.NextHopOnionType]
 	_, hasMPP := parsedTypes[record.MPPOnionType]
+	_, hasAMP := parsedTypes[record.AMPOnionType]
 
 	switch {
 
@@ -243,6 +253,14 @@ func ValidateParsedPayloadTypes(parsedTypes tlv.TypeMap,
 			Violation: IncludedViolation,
 			FinalHop:  isFinalHop,
 		}
+
+	// Intermediate nodes should never receive AMP fields.
+	case !isFinalHop && hasAMP:
+		return ErrInvalidPayload{
+			Type:      record.AMPOnionType,
+			Violation: IncludedViolation,
+			FinalHop:  isFinalHop,
+		}
 	}
 
 	return nil

htlcswitch/hop/payload_test.go

@@ -8,14 +8,18 @@ import (
 	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/record"
+	"github.com/stretchr/testify/require"
 )
 
+const testUnknownRequiredType = 0x10
+
 type decodePayloadTest struct {
 	name             string
 	payload          []byte
 	expErr           error
 	expCustomRecords map[uint64][]byte
 	shouldHaveMPP    bool
+	shouldHaveAMP    bool
 }
 
 var decodePayloadTests = []decodePayloadTest{
@@ -81,21 +85,26 @@ var decodePayloadTests = []decodePayloadTest{
 		},
 	},
 	{
-		name:    "required type after omitted hop id",
-		payload: []byte{0x02, 0x00, 0x04, 0x00, 0x0a, 0x00},
+		name: "required type after omitted hop id",
+		payload: []byte{
+			0x02, 0x00, 0x04, 0x00,
+			testUnknownRequiredType, 0x00,
+		},
 		expErr: hop.ErrInvalidPayload{
-			Type:      10,
+			Type:      testUnknownRequiredType,
 			Violation: hop.RequiredViolation,
 			FinalHop:  true,
 		},
 	},
 	{
 		name: "required type after included hop id",
-		payload: []byte{0x02, 0x00, 0x04, 0x00, 0x06, 0x08, 0x01, 0x00,
-			0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0a, 0x00,
+		payload: []byte{
+			0x02, 0x00, 0x04, 0x00, 0x06, 0x08, 0x01, 0x00, 0x00,
+			0x00, 0x00, 0x00, 0x00, 0x00,
+			testUnknownRequiredType, 0x00,
 		},
 		expErr: hop.ErrInvalidPayload{
-			Type:      10,
+			Type:      testUnknownRequiredType,
 			Violation: hop.RequiredViolation,
 			FinalHop:  false,
 		},
@@ -176,6 +185,37 @@ var decodePayloadTests = []decodePayloadTest{
 			FinalHop:  false,
 		},
 	},
+	{
+		name: "intermediate hop with amp",
+		payload: []byte{
+			// amount
+			0x02, 0x00,
+			// cltv
+			0x04, 0x00,
+			// next hop id
+			0x06, 0x08,
+			0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			// amp
+			0x0e, 0x41,
+			// amp.root_share
+			0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12,
+			0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12,
+			0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12,
+			0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12,
+			// amp.set_id
+			0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13,
+			0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13,
+			0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13,
+			0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13,
+			// amp.child_index
+			0x09,
+		},
+		expErr: hop.ErrInvalidPayload{
+			Type:      record.AMPOnionType,
+			Violation: hop.IncludedViolation,
+			FinalHop:  false,
+		},
+	},
 	{
 		name: "final hop with mpp",
 		payload: []byte{
@@ -194,6 +234,30 @@ var decodePayloadTests = []decodePayloadTest{
 		expErr:        nil,
 		shouldHaveMPP: true,
 	},
+	{
+		name: "final hop with amp",
+		payload: []byte{
+			// amount
+			0x02, 0x00,
+			// cltv
+			0x04, 0x00,
+			// amp
+			0x0e, 0x41,
+			// amp.root_share
+			0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12,
+			0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12,
+			0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12,
+			0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12,
+			// amp.set_id
+			0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13,
+			0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13,
+			0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13,
+			0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13,
+			// amp.child_index
+			0x09,
+		},
+		shouldHaveAMP: true,
+	},
 }
 
 // TestDecodeHopPayloadRecordValidation asserts that parsing the payloads in the
@@ -216,6 +280,20 @@ func testDecodeHopPayloadValidation(t *testing.T, test decodePayloadTest) {
 			0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11,
 			0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11,
 		}
+
+		testRootShare = [32]byte{
+			0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12,
+			0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12,
+			0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12,
+			0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12, 0x12,
+		}
+		testSetID = [32]byte{
+			0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13,
+			0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13,
+			0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13,
+			0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13, 0x13,
+		}
+		testChildIndex = uint32(9)
 	)
 
 	p, err := hop.NewPayloadFromReader(bytes.NewReader(test.payload))
@@ -242,6 +320,17 @@ func testDecodeHopPayloadValidation(t *testing.T, test decodePayloadTest) {
 		t.Fatalf("unexpected MPP payload")
 	}
 
+	if test.shouldHaveAMP {
+		if p.AMP == nil {
+			t.Fatalf("payload should have AMP record")
+		}
+		require.Equal(t, testRootShare, p.AMP.RootShare())
+		require.Equal(t, testSetID, p.AMP.SetID())
+		require.Equal(t, testChildIndex, p.AMP.ChildIndex())
+	} else if p.AMP != nil {
+		t.Fatalf("unexpected AMP payload")
+	}
+
 	// Convert expected nil map to empty map, because we always expect an
 	// initiated map from the payload.
 	expCustomRecords := make(record.CustomSet)

invoices/invoiceregistry.go

@@ -377,7 +377,8 @@ func (i *InvoiceRegistry) invoiceEventLoop() {
 func (i *InvoiceRegistry) dispatchToSingleClients(event *invoiceEvent) {
 	// Dispatch to single invoice subscribers.
 	for _, client := range i.singleNotificationClients {
-		if client.invoiceRef.PayHash() != event.hash {
+		payHash := client.invoiceRef.PayHash()
+		if payHash == nil || *payHash != event.hash {
 			continue
 		}
 
@@ -524,8 +525,13 @@ func (i *InvoiceRegistry) deliverSingleBacklogEvents(
 		return err
 	}
 
+	payHash := client.invoiceRef.PayHash()
+	if payHash == nil {
+		return nil
+	}
+
 	err = client.notify(&invoiceEvent{
-		hash:    client.invoiceRef.PayHash(),
+		hash:    *payHash,
 		invoice: &invoice,
 	})
 	if err != nil {
@@ -775,6 +781,67 @@ func (i *InvoiceRegistry) processKeySend(ctx invoiceUpdateCtx) error {
 	return nil
 }
 
+// processAMP just-in-time inserts an invoice if this htlc is a keysend
+// htlc.
+func (i *InvoiceRegistry) processAMP(ctx invoiceUpdateCtx) error {
+	// AMP payments MUST also include an MPP record.
+	if ctx.mpp == nil {
+		return errors.New("no MPP record for AMP")
+	}
+
+	// Create an invoice for the total amount expected, provided in the MPP
+	// record.
+	amt := ctx.mpp.TotalMsat()
+
+	// Set the TLV and MPP optional features on the invoice. We'll also make
+	// the AMP features required so that it can't be paid by legacy or MPP
+	// htlcs.
+	rawFeatures := lnwire.NewRawFeatureVector(
+		lnwire.TLVOnionPayloadOptional,
+		lnwire.PaymentAddrOptional,
+		lnwire.AMPRequired,
+	)
+	features := lnwire.NewFeatureVector(rawFeatures, lnwire.Features)
+
+	// Use the minimum block delta that we require for settling htlcs.
+	finalCltvDelta := i.cfg.FinalCltvRejectDelta
+
+	// Pre-check expiry here to prevent inserting an invoice that will not
+	// be settled.
+	if ctx.expiry < uint32(ctx.currentHeight+finalCltvDelta) {
+		return errors.New("final expiry too soon")
+	}
+
+	// We'll use the sender-generated payment address provided in the HTLC
+	// to create our AMP invoice.
+	payAddr := ctx.mpp.PaymentAddr()
+
+	// Create placeholder invoice.
+	invoice := &channeldb.Invoice{
+		CreationDate: i.cfg.Clock.Now(),
+		Terms: channeldb.ContractTerm{
+			FinalCltvDelta:  finalCltvDelta,
+			Value:           amt,
+			PaymentPreimage: nil,
+			PaymentAddr:     payAddr,
+			Features:        features,
+		},
+	}
+
+	// Insert invoice into database. Ignore duplicates payment hashes and
+	// payment addrs, this may be a replay or a different HTLC for the AMP
+	// invoice.
+	_, err := i.AddInvoice(invoice, ctx.hash)
+	switch {
+	case err == channeldb.ErrDuplicateInvoice:
+		return nil
+	case err == channeldb.ErrDuplicatePayAddr:
+		return nil
+	default:
+		return err
+	}
+}
+
 // NotifyExitHopHtlc attempts to mark an invoice as settled. The return value
 // describes how the htlc should be resolved.
 //
@@ -813,13 +880,24 @@ func (i *InvoiceRegistry) NotifyExitHopHtlc(rHash lntypes.Hash,
 	// AddInvoice obtains its own lock. This is no problem, because the
 	// operation is idempotent.
 	if i.cfg.AcceptKeySend {
-		err := i.processKeySend(ctx)
-		if err != nil {
-			ctx.log(fmt.Sprintf("keysend error: %v", err))
+		if ctx.amp != nil {
+			err := i.processAMP(ctx)
+			if err != nil {
+				ctx.log(fmt.Sprintf("amp error: %v", err))
 
-			return NewFailResolution(
-				circuitKey, currentHeight, ResultKeySendError,
-			), nil
+				return NewFailResolution(
+					circuitKey, currentHeight, ResultAmpError,
+				), nil
+			}
+		} else {
+			err := i.processKeySend(ctx)
+			if err != nil {
+				ctx.log(fmt.Sprintf("keysend error: %v", err))
+
+				return NewFailResolution(
+					circuitKey, currentHeight, ResultKeySendError,
+				), nil
+			}
 		}
 	}
 
@@ -926,6 +1004,31 @@ func (i *InvoiceRegistry) notifyExitHopHtlcLocked(
 			"outcome: %v, at accept height: %v",
 			res.Outcome, res.AcceptHeight))
 
+		// Some failures apply to the entire HTLC set. Break here if
+		// this isn't one of them.
+		if !res.Outcome.IsSetFailure() {
+			break
+		}
+
+		// Also cancel any HTLCs in the HTLC set that are also in the
+		// canceled state with the same failure result.
+		setID := ctx.setID()
+		for key, htlc := range invoice.Htlcs {
+			if htlc.State != channeldb.HtlcStateCanceled {
+				continue
+			}
+
+			if !htlc.IsInHTLCSet(setID) {
+				continue
+			}
+
+			htlcFailResolution := NewFailResolution(
+				key, int32(htlc.AcceptHeight), res.Outcome,
+			)
+
+			i.notifyHodlSubscribers(htlcFailResolution)
+		}
+
 	// If the htlc was settled, we will settle any previously accepted
 	// htlcs and notify our peer to settle them.
 	case *HtlcSettleResolution:
@@ -941,13 +1044,18 @@ func (i *InvoiceRegistry) notifyExitHopHtlcLocked(
 				continue
 			}
 
+			preimage := res.Preimage
+			if htlc.AMP != nil && htlc.AMP.Preimage != nil {
+				preimage = *htlc.AMP.Preimage
+			}
+
 			// Notify subscribers that the htlcs should be settled
 			// with our peer. Note that the outcome of the
 			// resolution is set based on the outcome of the single
 			// htlc that we just settled, so may not be accurate
 			// for all htlcs.
 			htlcSettleResolution := NewSettleResolution(
-				res.Preimage, key,
+				preimage, key,
 				int32(htlc.AcceptHeight), res.Outcome,
 			)
 

invoices/invoiceregistry_test.go

@@ -1,10 +1,12 @@
 package invoices
 
 import (
+	"crypto/rand"
 	"math"
 	"testing"
 	"time"
 
+	"github.com/lightningnetwork/lnd/amp"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/clock"
 	"github.com/lightningnetwork/lnd/lntypes"
@@ -29,9 +31,7 @@ func TestSettleInvoice(t *testing.T) {
 	}
 	defer subscription.Cancel()
 
-	if subscription.invoiceRef.PayHash() != testInvoicePaymentHash {
-		t.Fatalf("expected subscription for provided hash")
-	}
+	require.Equal(t, subscription.invoiceRef.PayHash(), &testInvoicePaymentHash)
 
 	// Add the invoice.
 	addIdx, err := ctx.registry.AddInvoice(testInvoice, testInvoicePaymentHash)
@@ -77,19 +77,11 @@ func TestSettleInvoice(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	failResolution, ok := resolution.(*HtlcFailResolution)
-	if !ok {
-		t.Fatalf("expected fail resolution, got: %T",
-			resolution)
-	}
-	if failResolution.AcceptHeight != testCurrentHeight {
-		t.Fatalf("expected acceptHeight %v, but got %v",
-			testCurrentHeight, failResolution.AcceptHeight)
-	}
-	if failResolution.Outcome != ResultExpiryTooSoon {
-		t.Fatalf("expected expiry too soon, got: %v",
-			failResolution.Outcome)
-	}
+	require.NotNil(t, resolution)
+	failResolution := checkFailResolution(
+		t, resolution, ResultExpiryTooSoon,
+	)
+	require.Equal(t, testCurrentHeight, failResolution.AcceptHeight)
 
 	// Settle invoice with a slightly higher amount.
 	amtPaid := lnwire.MilliSatoshi(100500)
@@ -101,15 +93,11 @@ func TestSettleInvoice(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	settleResolution, ok := resolution.(*HtlcSettleResolution)
-	if !ok {
-		t.Fatalf("expected settle resolution, got: %T",
-			resolution)
-	}
-	if settleResolution.Outcome != ResultSettled {
-		t.Fatalf("expected settled, got: %v",
-			settleResolution.Outcome)
-	}
+	require.NotNil(t, resolution)
+	settleResolution := checkSettleResolution(
+		t, resolution, testInvoicePreimage,
+	)
+	require.Equal(t, ResultSettled, settleResolution.Outcome)
 
 	// We expect the settled state to be sent to the single invoice
 	// subscriber.
@@ -146,15 +134,11 @@ func TestSettleInvoice(t *testing.T) {
 	if err != nil {
 		t.Fatalf("unexpected NotifyExitHopHtlc error: %v", err)
 	}
-	settleResolution, ok = resolution.(*HtlcSettleResolution)
-	if !ok {
-		t.Fatalf("expected settle resolution, got: %T",
-			resolution)
-	}
-	if settleResolution.Outcome != ResultReplayToSettled {
-		t.Fatalf("expected replay settled, got: %v",
-			settleResolution.Outcome)
-	}
+	require.NotNil(t, resolution)
+	settleResolution = checkSettleResolution(
+		t, resolution, testInvoicePreimage,
+	)
+	require.Equal(t, ResultReplayToSettled, settleResolution.Outcome)
 
 	// Try to settle again with a new higher-valued htlc. This payment
 	// should also be accepted, to prevent any change in behaviour for a
@@ -166,15 +150,11 @@ func TestSettleInvoice(t *testing.T) {
 	if err != nil {
 		t.Fatalf("unexpected NotifyExitHopHtlc error: %v", err)
 	}
-	settleResolution, ok = resolution.(*HtlcSettleResolution)
-	if !ok {
-		t.Fatalf("expected settle resolution, got: %T",
-			resolution)
-	}
-	if settleResolution.Outcome != ResultDuplicateToSettled {
-		t.Fatalf("expected duplicate settled, got: %v",
-			settleResolution.Outcome)
-	}
+	require.NotNil(t, resolution)
+	settleResolution = checkSettleResolution(
+		t, resolution, testInvoicePreimage,
+	)
+	require.Equal(t, ResultDuplicateToSettled, settleResolution.Outcome)
 
 	// Try to settle again with a lower amount. This should fail just as it
 	// would have failed if it were the first payment.
@@ -185,15 +165,8 @@ func TestSettleInvoice(t *testing.T) {
 	if err != nil {
 		t.Fatalf("unexpected NotifyExitHopHtlc error: %v", err)
 	}
-	failResolution, ok = resolution.(*HtlcFailResolution)
-	if !ok {
-		t.Fatalf("expected fail resolution, got: %T",
-			resolution)
-	}
-	if failResolution.Outcome != ResultAmountTooLow {
-		t.Fatalf("expected amount too low, got: %v",
-			failResolution.Outcome)
-	}
+	require.NotNil(t, resolution)
+	checkFailResolution(t, resolution, ResultAmountTooLow)
 
 	// Check that settled amount is equal to the sum of values of the htlcs
 	// 0 and 1.
@@ -244,9 +217,7 @@ func testCancelInvoice(t *testing.T, gc bool) {
 	}
 	defer subscription.Cancel()
 
-	if subscription.invoiceRef.PayHash() != testInvoicePaymentHash {
-		t.Fatalf("expected subscription for provided hash")
-	}
+	require.Equal(t, subscription.invoiceRef.PayHash(), &testInvoicePaymentHash)
 
 	// Add the invoice.
 	amt := lnwire.MilliSatoshi(100000)
@@ -333,27 +304,23 @@ func testCancelInvoice(t *testing.T, gc bool) {
 	if err != nil {
 		t.Fatal("expected settlement of a canceled invoice to succeed")
 	}
-	failResolution, ok := resolution.(*HtlcFailResolution)
-	if !ok {
-		t.Fatalf("expected fail resolution, got: %T",
-			resolution)
-	}
-	if failResolution.AcceptHeight != testCurrentHeight {
-		t.Fatalf("expected acceptHeight %v, but got %v",
-			testCurrentHeight, failResolution.AcceptHeight)
-	}
+	require.NotNil(t, resolution)
 
 	// If the invoice has been deleted (or not present) then we expect the
 	// outcome to be ResultInvoiceNotFound instead of when the invoice is
 	// in our database in which case we expect ResultInvoiceAlreadyCanceled.
+	var failResolution *HtlcFailResolution
 	if gc {
-		require.Equal(t, failResolution.Outcome, ResultInvoiceNotFound)
+		failResolution = checkFailResolution(
+			t, resolution, ResultInvoiceNotFound,
+		)
 	} else {
-		require.Equal(t,
-			failResolution.Outcome,
-			ResultInvoiceAlreadyCanceled,
+		failResolution = checkFailResolution(
+			t, resolution, ResultInvoiceAlreadyCanceled,
 		)
 	}
+
+	require.Equal(t, testCurrentHeight, failResolution.AcceptHeight)
 }
 
 // TestCancelInvoice tests cancelation of an invoice and related notifications.
@@ -404,9 +371,7 @@ func TestSettleHoldInvoice(t *testing.T) {
 	}
 	defer subscription.Cancel()
 
-	if subscription.invoiceRef.PayHash() != testInvoicePaymentHash {
-		t.Fatalf("expected subscription for provided hash")
-	}
+	require.Equal(t, subscription.invoiceRef.PayHash(), &testInvoicePaymentHash)
 
 	// Add the invoice.
 	_, err = registry.AddInvoice(testHodlInvoice, testInvoicePaymentHash)
@@ -480,15 +445,8 @@ func TestSettleHoldInvoice(t *testing.T) {
 	if err != nil {
 		t.Fatalf("expected settle to succeed but got %v", err)
 	}
-	failResolution, ok := resolution.(*HtlcFailResolution)
-	if !ok {
-		t.Fatalf("expected fail resolution, got: %T",
-			resolution)
-	}
-	if failResolution.Outcome != ResultExpiryTooSoon {
-		t.Fatalf("expected expiry too soon, got: %v",
-			failResolution.Outcome)
-	}
+	require.NotNil(t, resolution)
+	checkFailResolution(t, resolution, ResultExpiryTooSoon)
 
 	// We expect the accepted state to be sent to the single invoice
 	// subscriber. For all invoice subscribers, we don't expect an update.
@@ -509,22 +467,12 @@ func TestSettleHoldInvoice(t *testing.T) {
 	}
 
 	htlcResolution := (<-hodlChan).(HtlcResolution)
-	settleResolution, ok := htlcResolution.(*HtlcSettleResolution)
-	if !ok {
-		t.Fatalf("expected settle resolution, got: %T",
-			htlcResolution)
-	}
-	if settleResolution.Preimage != testInvoicePreimage {
-		t.Fatal("unexpected preimage in hodl resolution")
-	}
-	if settleResolution.AcceptHeight != testCurrentHeight {
-		t.Fatalf("expected acceptHeight %v, but got %v",
-			testCurrentHeight, settleResolution.AcceptHeight)
-	}
-	if settleResolution.Outcome != ResultSettled {
-		t.Fatalf("expected result settled, got: %v",
-			settleResolution.Outcome)
-	}
+	require.NotNil(t, htlcResolution)
+	settleResolution := checkSettleResolution(
+		t, htlcResolution, testInvoicePreimage,
+	)
+	require.Equal(t, testCurrentHeight, settleResolution.AcceptHeight)
+	require.Equal(t, ResultSettled, settleResolution.Outcome)
 
 	// We expect a settled notification to be sent out for both all and
 	// single invoice subscribers.
@@ -610,11 +558,8 @@ func TestCancelHoldInvoice(t *testing.T) {
 	}
 
 	htlcResolution := (<-hodlChan).(HtlcResolution)
-	_, ok := htlcResolution.(*HtlcFailResolution)
-	if !ok {
-		t.Fatalf("expected fail resolution, got: %T",
-			htlcResolution)
-	}
+	require.NotNil(t, htlcResolution)
+	checkFailResolution(t, htlcResolution, ResultCanceled)
 
 	// Offering the same htlc again at a higher height should still result
 	// in a rejection. The accept height is expected to be the original
@@ -626,19 +571,11 @@ func TestCancelHoldInvoice(t *testing.T) {
 	if err != nil {
 		t.Fatalf("expected settle to succeed but got %v", err)
 	}
-	failResolution, ok := resolution.(*HtlcFailResolution)
-	if !ok {
-		t.Fatalf("expected fail resolution, got: %T",
-			resolution)
-	}
-	if failResolution.AcceptHeight != testCurrentHeight {
-		t.Fatalf("expected acceptHeight %v, but got %v",
-			testCurrentHeight, failResolution.AcceptHeight)
-	}
-	if failResolution.Outcome != ResultReplayToCanceled {
-		t.Fatalf("expected replay to canceled, got %v",
-			failResolution.Outcome)
-	}
+	require.NotNil(t, resolution)
+	failResolution := checkFailResolution(
+		t, resolution, ResultReplayToCanceled,
+	)
+	require.Equal(t, testCurrentHeight, failResolution.AcceptHeight)
 }
 
 // TestUnknownInvoice tests that invoice registry returns an error when the
@@ -661,15 +598,8 @@ func TestUnknownInvoice(t *testing.T) {
 	if err != nil {
 		t.Fatal("unexpected error")
 	}
-	failResolution, ok := resolution.(*HtlcFailResolution)
-	if !ok {
-		t.Fatalf("expected fail resolution, got: %T",
-			resolution)
-	}
-	if failResolution.Outcome != ResultInvoiceNotFound {
-		t.Fatalf("expected ResultInvoiceNotFound, got: %v",
-			failResolution.Outcome)
-	}
+	require.NotNil(t, resolution)
+	checkFailResolution(t, resolution, ResultInvoiceNotFound)
 }
 
 // TestKeySend tests receiving a spontaneous payment with and without keysend
@@ -721,18 +651,12 @@ func testKeySend(t *testing.T, keySendEnabled bool) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	failResolution, ok := resolution.(*HtlcFailResolution)
-	if !ok {
-		t.Fatalf("expected fail resolution, got: %T",
-			resolution)
-	}
+	require.NotNil(t, resolution)
 
-	switch {
-	case !keySendEnabled && failResolution.Outcome != ResultInvoiceNotFound:
-		t.Fatal("expected invoice not found outcome")
-
-	case keySendEnabled && failResolution.Outcome != ResultKeySendError:
-		t.Fatal("expected keysend error")
+	if !keySendEnabled {
+		checkFailResolution(t, resolution, ResultInvoiceNotFound)
+	} else {
+		checkFailResolution(t, resolution, ResultKeySendError)
 	}
 
 	// Try to settle invoice with a valid keysend htlc.
@@ -752,23 +676,10 @@ func testKeySend(t *testing.T, keySendEnabled bool) {
 
 	// Expect a cancel resolution if keysend is disabled.
 	if !keySendEnabled {
-		failResolution, ok = resolution.(*HtlcFailResolution)
-		if !ok {
-			t.Fatalf("expected fail resolution, got: %T",
-				resolution)
-		}
-		if failResolution.Outcome != ResultInvoiceNotFound {
-			t.Fatal("expected keysend payment not to be accepted")
-		}
+		checkFailResolution(t, resolution, ResultInvoiceNotFound)
 		return
 	}
 
-	checkResolution := func(res HtlcResolution, pimg lntypes.Preimage) {
-		// Otherwise we expect no error and a settle res for the htlc.
-		settleResolution, ok := res.(*HtlcSettleResolution)
-		require.True(t, ok)
-		require.Equal(t, settleResolution.Preimage, pimg)
-	}
 	checkSubscription := func() {
 		// We expect a new invoice notification to be sent out.
 		newInvoice := <-allSubscriptions.NewInvoices
@@ -779,7 +690,7 @@ func testKeySend(t *testing.T, keySendEnabled bool) {
 		require.Equal(t, settledInvoice.State, channeldb.ContractSettled)
 	}
 
-	checkResolution(resolution, preimage)
+	checkSettleResolution(t, resolution, preimage)
 	checkSubscription()
 
 	// Replay the same keysend payment. We expect an identical resolution,
@@ -789,7 +700,7 @@ func testKeySend(t *testing.T, keySendEnabled bool) {
 		testCurrentHeight, getCircuitKey(10), hodlChan, keySendPayload,
 	)
 	require.Nil(t, err)
-	checkResolution(resolution, preimage)
+	checkSettleResolution(t, resolution, preimage)
 
 	select {
 	case <-allSubscriptions.NewInvoices:
@@ -814,7 +725,7 @@ func testKeySend(t *testing.T, keySendEnabled bool) {
 	)
 	require.Nil(t, err)
 
-	checkResolution(resolution, preimage2)
+	checkSettleResolution(t, resolution, preimage2)
 	checkSubscription()
 }
 
@@ -1211,7 +1122,7 @@ func TestSettleInvoicePaymentAddrRequired(t *testing.T) {
 	defer subscription.Cancel()
 
 	require.Equal(
-		t, subscription.invoiceRef.PayHash(), testInvoicePaymentHash,
+		t, subscription.invoiceRef.PayHash(), &testInvoicePaymentHash,
 	)
 
 	// Add the invoice, which requires the MPP payload to always be
@@ -1287,7 +1198,7 @@ func TestSettleInvoicePaymentAddrRequiredOptionalGrace(t *testing.T) {
 	defer subscription.Cancel()
 
 	require.Equal(
-		t, subscription.invoiceRef.PayHash(), testInvoicePaymentHash,
+		t, subscription.invoiceRef.PayHash(), &testInvoicePaymentHash,
 	)
 
 	// Add the invoice, which requires the MPP payload to always be
@@ -1364,3 +1275,254 @@ func TestSettleInvoicePaymentAddrRequiredOptionalGrace(t *testing.T) {
 		t.Fatal("no update received")
 	}
 }
+
+// TestAMPWithoutMPPPayload asserts that we correctly reject an AMP HTLC that
+// does not include an MPP record.
+func TestAMPWithoutMPPPayload(t *testing.T) {
+	defer timeout()()
+
+	ctx := newTestContext(t)
+	defer ctx.cleanup()
+
+	ctx.registry.cfg.AcceptKeySend = true
+
+	const (
+		shardAmt = lnwire.MilliSatoshi(10)
+		expiry   = uint32(testCurrentHeight + 20)
+	)
+
+	// Create payload with missing MPP field.
+	payload := &mockPayload{
+		amp: record.NewAMP([32]byte{}, [32]byte{}, 0),
+	}
+
+	hodlChan := make(chan interface{}, 1)
+	resolution, err := ctx.registry.NotifyExitHopHtlc(
+		lntypes.Hash{}, shardAmt, expiry,
+		testCurrentHeight, getCircuitKey(uint64(10)), hodlChan,
+		payload,
+	)
+	require.NoError(t, err)
+
+	// We should receive the ResultAmpError failure.
+	require.NotNil(t, resolution)
+	checkFailResolution(t, resolution, ResultAmpError)
+}
+
+// TestSpontaneousAmpPayment tests receiving a spontaneous AMP payment with both
+// valid and invalid reconstructions.
+func TestSpontaneousAmpPayment(t *testing.T) {
+	tests := []struct {
+		name               string
+		keySendEnabled     bool
+		failReconstruction bool
+		numShards          int
+	}{
+		{
+			name:               "enabled valid one shard",
+			keySendEnabled:     true,
+			failReconstruction: false,
+			numShards:          1,
+		},
+		{
+			name:               "enabled valid multiple shards",
+			keySendEnabled:     true,
+			failReconstruction: false,
+			numShards:          3,
+		},
+		{
+			name:               "enabled invalid one shard",
+			keySendEnabled:     true,
+			failReconstruction: true,
+			numShards:          1,
+		},
+		{
+			name:               "enabled invalid multiple shards",
+			keySendEnabled:     true,
+			failReconstruction: true,
+			numShards:          3,
+		},
+		{
+			name:               "disabled valid multiple shards",
+			keySendEnabled:     false,
+			failReconstruction: false,
+			numShards:          3,
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			testSpontaneousAmpPayment(
+				t, test.keySendEnabled, test.failReconstruction,
+				test.numShards,
+			)
+		})
+	}
+}
+
+// testSpontaneousAmpPayment runs a specific spontaneous AMP test case.
+func testSpontaneousAmpPayment(
+	t *testing.T, keySendEnabled, failReconstruction bool, numShards int) {
+
+	defer timeout()()
+
+	ctx := newTestContext(t)
+	defer ctx.cleanup()
+
+	ctx.registry.cfg.AcceptKeySend = keySendEnabled
+
+	allSubscriptions, err := ctx.registry.SubscribeNotifications(0, 0)
+	require.Nil(t, err)
+	defer allSubscriptions.Cancel()
+
+	const (
+		totalAmt = lnwire.MilliSatoshi(360)
+		expiry   = uint32(testCurrentHeight + 20)
+	)
+
+	var (
+		shardAmt = totalAmt / lnwire.MilliSatoshi(numShards)
+		payAddr  [32]byte
+		setID    [32]byte
+	)
+	_, err = rand.Read(payAddr[:])
+	require.NoError(t, err)
+	_, err = rand.Read(setID[:])
+	require.NoError(t, err)
+
+	var sharer amp.Sharer
+	sharer, err = amp.NewSeedSharer()
+	require.NoError(t, err)
+
+	// Asserts that a new invoice is published on the NewInvoices channel.
+	checkOpenSubscription := func() {
+		t.Helper()
+		newInvoice := <-allSubscriptions.NewInvoices
+		require.Equal(t, newInvoice.State, channeldb.ContractOpen)
+	}
+
+	// Asserts that a settled invoice is published on the SettledInvoices
+	// channel.
+	checkSettleSubscription := func() {
+		t.Helper()
+		settledInvoice := <-allSubscriptions.SettledInvoices
+		require.Equal(t, settledInvoice.State, channeldb.ContractSettled)
+	}
+
+	// Asserts that no invoice is published on the SettledInvoices channel
+	// w/in two seconds.
+	checkNoSettleSubscription := func() {
+		t.Helper()
+		select {
+		case <-allSubscriptions.SettledInvoices:
+			t.Fatal("no settle ntfn expected")
+		case <-time.After(2 * time.Second):
+		}
+	}
+
+	// Record the hodl channels of all HTLCs but the last one, which
+	// received its resolution directly from NotifyExistHopHtlc.
+	hodlChans := make(map[lntypes.Preimage]chan interface{})
+	for i := 0; i < numShards; i++ {
+		isFinalShard := i == numShards-1
+
+		hodlChan := make(chan interface{}, 1)
+
+		var child *amp.Child
+		if !isFinalShard {
+			var left amp.Sharer
+			left, sharer, err = sharer.Split()
+			require.NoError(t, err)
+
+			child = left.Child(uint32(i))
+
+			// Only store the first numShards-1 hodlChans.
+			hodlChans[child.Preimage] = hodlChan
+		} else {
+			child = sharer.Child(uint32(i))
+		}
+
+		// Send a blank share when the set should fail reconstruction,
+		// otherwise send the derived share.
+		var share [32]byte
+		if !failReconstruction {
+			share = child.Share
+		}
+
+		payload := &mockPayload{
+			mpp: record.NewMPP(totalAmt, payAddr),
+			amp: record.NewAMP(share, setID, uint32(i)),
+		}
+
+		resolution, err := ctx.registry.NotifyExitHopHtlc(
+			child.Hash, shardAmt, expiry,
+			testCurrentHeight, getCircuitKey(uint64(i)), hodlChan,
+			payload,
+		)
+		require.NoError(t, err)
+
+		// When keysend is disabled all HTLC should fail with invoice
+		// not found, since one is not inserted before executing
+		// UpdateInvoice.
+		if !keySendEnabled {
+			require.NotNil(t, resolution)
+			checkFailResolution(t, resolution, ResultInvoiceNotFound)
+			continue
+		}
+
+		// Check that resolutions are properly formed.
+		if !isFinalShard {
+			// Non-final shares should always return a nil
+			// resolution, theirs will be delivered via the
+			// hodlChan.
+			require.Nil(t, resolution)
+		} else {
+			// The final share should receive a non-nil resolution.
+			// Also assert that it is the proper type based on the
+			// test case.
+			require.NotNil(t, resolution)
+			if failReconstruction {
+				checkFailResolution(t, resolution, ResultAmpReconstruction)
+			} else {
+				checkSettleResolution(t, resolution, child.Preimage)
+			}
+		}
+
+		// Assert the behavior of the Open and Settle notifications.
+		// There should always be an open (keysend is enabled) followed
+		// by settle for valid AMP payments.
+		//
+		// NOTE: The cases are split in separate if conditions, rather
+		// than else-if, to properly handle the case when there is only
+		// one shard.
+		if i == 0 {
+			checkOpenSubscription()
+		}
+		if isFinalShard {
+			if failReconstruction {
+				checkNoSettleSubscription()
+			} else {
+				checkSettleSubscription()
+			}
+		}
+	}
+
+	// No need to check the hodl chans when keysend is not enabled.
+	if !keySendEnabled {
+		return
+	}
+
+	// For the non-final hodl chans, assert that they receive the expected
+	// failure or preimage.
+	for preimage, hodlChan := range hodlChans {
+		resolution, ok := (<-hodlChan).(HtlcResolution)
+		require.True(t, ok)
+		require.NotNil(t, resolution)
+		if failReconstruction {
+			checkFailResolution(t, resolution, ResultAmpReconstruction)
+		} else {
+			checkSettleResolution(t, resolution, preimage)
+		}
+	}
+}

invoices/resolution_result.go

@@ -105,6 +105,13 @@ const (
 	// ResultMppInProgress is returned when we are busy receiving a mpp
 	// payment.
 	ResultMppInProgress
+
+	// ResultAmpError is returned when we receive invalid AMP parameters.
+	ResultAmpError
+
+	// ResultAmpReconstruction is returned when the derived child
+	// hash/preimage pairs were invalid for at least one HTLC in the set.
+	ResultAmpReconstruction
 )
 
 // String returns a string representation of the result.
@@ -162,11 +169,34 @@ func (f FailResolutionResult) FailureString() string {
 	case ResultMppInProgress:
 		return "mpp reception in progress"
 
+	case ResultAmpError:
+		return "invalid amp parameters"
+
+	case ResultAmpReconstruction:
+		return "amp reconstruction failed"
+
 	default:
 		return "unknown failure resolution result"
 	}
 }
 
+// IsSetFailure returns true if this failure should result in the entire HTLC
+// set being failed with the same result.
+func (f FailResolutionResult) IsSetFailure() bool {
+	switch f {
+	case
+		ResultAmpReconstruction,
+		ResultHtlcSetTotalTooLow,
+		ResultHtlcSetTotalMismatch,
+		ResultHtlcSetOverpayment:
+
+		return true
+
+	default:
+		return false
+	}
+}
+
 // SettleResolutionResult provides metadata which about a htlc that was failed
 // by the registry. It can be used to take custom actions on resolution of the
 // htlc.

invoices/test_utils_test.go

@@ -19,6 +19,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/record"
 	"github.com/lightningnetwork/lnd/zpay32"
+	"github.com/stretchr/testify/require"
 )
 
 type mockPayload struct {
@@ -45,6 +46,16 @@ func (p *mockPayload) CustomRecords() record.CustomSet {
 	return p.customRecords
 }
 
+const (
+	testHtlcExpiry = uint32(5)
+
+	testInvoiceCltvDelta = uint32(4)
+
+	testFinalCltvRejectDelta = int32(4)
+
+	testCurrentHeight = int32(1)
+)
+
 var (
 	testTimeout = 5 * time.Second
 
@@ -54,14 +65,6 @@ var (
 
 	testInvoicePaymentHash = testInvoicePreimage.Hash()
 
-	testHtlcExpiry = uint32(5)
-
-	testInvoiceCltvDelta = uint32(4)
-
-	testFinalCltvRejectDelta = int32(4)
-
-	testCurrentHeight = int32(1)
-
 	testPrivKeyBytes, _ = hex.DecodeString(
 		"e126f68f7eafcc8b74f54d269fe206be715000f94dac067d1c04a8ca3b2db734")
 
@@ -111,7 +114,10 @@ var (
 			Value:           testInvoiceAmt,
 			Expiry:          time.Hour,
 			Features: lnwire.NewFeatureVector(
-				lnwire.NewRawFeatureVector(lnwire.PaymentAddrRequired),
+				lnwire.NewRawFeatureVector(
+					lnwire.TLVOnionPayloadOptional,
+					lnwire.PaymentAddrRequired,
+				),
 				lnwire.Features,
 			),
 		},
@@ -124,7 +130,10 @@ var (
 			Value:           testInvoiceAmt,
 			Expiry:          time.Hour,
 			Features: lnwire.NewFeatureVector(
-				lnwire.NewRawFeatureVector(lnwire.PaymentAddrOptional),
+				lnwire.NewRawFeatureVector(
+					lnwire.TLVOnionPayloadOptional,
+					lnwire.PaymentAddrOptional,
+				),
 				lnwire.Features,
 			),
 		},
@@ -325,3 +334,32 @@ func generateInvoiceExpiryTestData(
 
 	return testData
 }
+
+// checkSettleResolution asserts the resolution is a settle with the correct
+// preimage. If successful, the HtlcSettleResolution is returned in case further
+// checks are desired.
+func checkSettleResolution(t *testing.T, res HtlcResolution,
+	expPreimage lntypes.Preimage) *HtlcSettleResolution {
+
+	t.Helper()
+
+	settleResolution, ok := res.(*HtlcSettleResolution)
+	require.True(t, ok)
+	require.Equal(t, expPreimage, settleResolution.Preimage)
+
+	return settleResolution
+}
+
+// checkFailResolution asserts the resolution is a fail with the correct reason.
+// If successful, the HtlcFailResolutionis returned in case further checks are
+// desired.
+func checkFailResolution(t *testing.T, res HtlcResolution,
+	expOutcome FailResolutionResult) *HtlcFailResolution {
+
+	t.Helper()
+	failResolution, ok := res.(*HtlcFailResolution)
+	require.True(t, ok)
+	require.Equal(t, expOutcome, failResolution.Outcome)
+
+	return failResolution
+}

invoices/update.go

@@ -3,6 +3,7 @@ package invoices
 import (
 	"errors"
 
+	"github.com/lightningnetwork/lnd/amp"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwire"
@@ -26,11 +27,16 @@ type invoiceUpdateCtx struct {
 // invoiceRef returns an identifier that can be used to lookup or update the
 // invoice this HTLC is targeting.
 func (i *invoiceUpdateCtx) invoiceRef() channeldb.InvoiceRef {
-	if i.mpp != nil {
+	switch {
+	case i.amp != nil && i.mpp != nil:
+		payAddr := i.mpp.PaymentAddr()
+		return channeldb.InvoiceRefByAddr(payAddr)
+	case i.mpp != nil:
 		payAddr := i.mpp.PaymentAddr()
 		return channeldb.InvoiceRefByHashAndAddr(i.hash, payAddr)
+	default:
+		return channeldb.InvoiceRefByHash(i.hash)
 	}
-	return channeldb.InvoiceRefByHash(i.hash)
 }
 
 // setID returns an identifier that identifies other possible HTLCs that this
@@ -47,7 +53,7 @@ func (i invoiceUpdateCtx) setID() *[32]byte {
 // log logs a message specific to this update context.
 func (i *invoiceUpdateCtx) log(s string) {
 	log.Debugf("Invoice%v: %v, amt=%v, expiry=%v, circuit=%v, mpp=%v, "+
-		"amp=%v", i.hash[:], s, i.amtPaid, i.expiry, i.circuitKey,
+		"amp=%v", i.invoiceRef(), s, i.amtPaid, i.expiry, i.circuitKey,
 		i.mpp, i.amp)
 }
 
@@ -130,6 +136,14 @@ func updateMpp(ctx *invoiceUpdateCtx,
 		CustomRecords: ctx.customRecords,
 	}
 
+	if ctx.amp != nil {
+		acceptDesc.AMP = &channeldb.InvoiceHtlcAMPData{
+			Record:   *ctx.amp,
+			Hash:     ctx.hash,
+			Preimage: nil,
+		}
+	}
+
 	// Only accept payments to open invoices. This behaviour differs from
 	// non-mpp payments that are accepted even after the invoice is settled.
 	// Because non-mpp payments don't have a payment address, this is needed
@@ -154,9 +168,18 @@ func updateMpp(ctx *invoiceUpdateCtx,
 		return nil, ctx.failRes(ResultHtlcSetTotalTooLow), nil
 	}
 
+	htlcSet := inv.HTLCSet(setID)
+
 	// Check whether total amt matches other htlcs in the set.
 	var newSetTotal lnwire.MilliSatoshi
-	for _, htlc := range inv.HTLCSet(setID) {
+	for _, htlc := range htlcSet {
+		// Only consider accepted mpp htlcs. It is possible that there
+		// are htlcs registered in the invoice database that previously
+		// timed out and are in the canceled state now.
+		if htlc.State != channeldb.HtlcStateAccepted {
+			continue
+		}
+
 		if ctx.mpp.TotalMsat() != htlc.MppTotalAmt {
 			return nil, ctx.failRes(ResultHtlcSetTotalMismatch), nil
 		}
@@ -206,15 +229,107 @@ func updateMpp(ctx *invoiceUpdateCtx,
 		return &update, ctx.acceptRes(resultAccepted), nil
 	}
 
-	update.State = &channeldb.InvoiceStateUpdateDesc{
-		NewState: channeldb.ContractSettled,
-		Preimage: inv.Terms.PaymentPreimage,
-		SetID:    setID,
+	var (
+		htlcPreimages map[channeldb.CircuitKey]lntypes.Preimage
+		htlcPreimage  lntypes.Preimage
+	)
+	if ctx.amp != nil {
+		var failRes *HtlcFailResolution
+		htlcPreimages, failRes = reconstructAMPPreimages(ctx, htlcSet)
+		if failRes != nil {
+			update.State = &channeldb.InvoiceStateUpdateDesc{
+				NewState: channeldb.ContractCanceled,
+				SetID:    setID,
+			}
+			return &update, failRes, nil
+		}
+
+		// The preimage for _this_ HTLC will be the one with context's
+		// circuit key.
+		htlcPreimage = htlcPreimages[ctx.circuitKey]
+	} else {
+		htlcPreimage = *inv.Terms.PaymentPreimage
 	}
 
-	return &update, ctx.settleRes(
-		*inv.Terms.PaymentPreimage, ResultSettled,
-	), nil
+	update.State = &channeldb.InvoiceStateUpdateDesc{
+		NewState:      channeldb.ContractSettled,
+		Preimage:      inv.Terms.PaymentPreimage,
+		HTLCPreimages: htlcPreimages,
+		SetID:         setID,
+	}
+
+	return &update, ctx.settleRes(htlcPreimage, ResultSettled), nil
+}
+
+// HTLCSet is a map of CircuitKey to InvoiceHTLC.
+type HTLCSet = map[channeldb.CircuitKey]*channeldb.InvoiceHTLC
+
+// HTLCPreimages is a map of CircuitKey to preimage.
+type HTLCPreimages = map[channeldb.CircuitKey]lntypes.Preimage
+
+// reconstructAMPPreimages reconstructs the root seed for an AMP HTLC set and
+// verifies that all derived child hashes match the payment hashes of the HTLCs
+// in the set. This method is meant to be called after receiving the full amount
+// committed to via mpp_total_msat. This method will return a fail resolution if
+// any of the child hashes fail to matche theire corresponding HTLCs.
+func reconstructAMPPreimages(ctx *invoiceUpdateCtx,
+	htlcSet HTLCSet) (HTLCPreimages, *HtlcFailResolution) {
+
+	// Create a slice containing all the child descriptors to be used for
+	// reconstruction. This should include all HTLCs currently in the HTLC
+	// set, plus the incoming HTLC.
+	childDescs := make([]amp.ChildDesc, 0, 1+len(htlcSet))
+
+	// Add the new HTLC's child descriptor at index 0.
+	childDescs = append(childDescs, amp.ChildDesc{
+		Share: ctx.amp.RootShare(),
+		Index: ctx.amp.ChildIndex(),
+	})
+
+	// Next, construct an index mapping the position in childDescs to a
+	// circuit key for all preexisting HTLCs.
+	indexToCircuitKey := make(map[int]channeldb.CircuitKey)
+
+	// Add the child descriptor for each HTLC in the HTLC set, recording
+	// it's position within the slice.
+	var htlcSetIndex int
+	for circuitKey, htlc := range htlcSet {
+		childDescs = append(childDescs, amp.ChildDesc{
+			Share: htlc.AMP.Record.RootShare(),
+			Index: htlc.AMP.Record.ChildIndex(),
+		})
+		indexToCircuitKey[htlcSetIndex] = circuitKey
+		htlcSetIndex++
+	}
+
+	// Using the child descriptors, reconstruct the root seed and derive the
+	// child hash/preimage pairs for each of the HTLCs.
+	children := amp.ReconstructChildren(childDescs...)
+
+	// Validate that the derived child preimages match the hash of each
+	// HTLC's respective hash.
+	if ctx.hash != children[0].Hash {
+		return nil, ctx.failRes(ResultAmpReconstruction)
+	}
+	for idx, child := range children[1:] {
+		circuitKey := indexToCircuitKey[idx]
+		htlc := htlcSet[circuitKey]
+		if htlc.AMP.Hash != child.Hash {
+			return nil, ctx.failRes(ResultAmpReconstruction)
+		}
+	}
+
+	// Finally, construct the map of learned preimages indexed by circuit
+	// key, so that they can be persisted along with each HTLC when updating
+	// the invoice.
+	htlcPreimages := make(map[channeldb.CircuitKey]lntypes.Preimage)
+	htlcPreimages[ctx.circuitKey] = children[0].Preimage
+	for idx, child := range children[1:] {
+		circuitKey := indexToCircuitKey[idx]
+		htlcPreimages[circuitKey] = child.Preimage
+	}
+
+	return htlcPreimages, nil
 }
 
 // updateLegacy is a callback for DB.UpdateInvoice that contains the invoice

lnrpc/invoicesrpc/utils.go

@@ -2,7 +2,6 @@ package invoicesrpc
 
 import (
 	"encoding/hex"
-	"errors"
 	"fmt"
 
 	"github.com/btcsuite/btcd/btcec"
@@ -24,7 +23,7 @@ func decodePayReq(invoice *channeldb.Invoice,
 	if paymentRequest == "" {
 		preimage := invoice.Terms.PaymentPreimage
 		if preimage == nil {
-			return nil, errors.New("cannot reconstruct pay req")
+			return &zpay32.Invoice{}, nil
 		}
 		hash := [32]byte(preimage.Hash())
 		return &zpay32.Invoice{
@@ -51,6 +50,11 @@ func CreateRPCInvoice(invoice *channeldb.Invoice,
 		return nil, err
 	}
 
+	var rHash []byte
+	if decoded.PaymentHash != nil {
+		rHash = decoded.PaymentHash[:]
+	}
+
 	var descHash []byte
 	if decoded.DescriptionHash != nil {
 		descHash = decoded.DescriptionHash[:]
@@ -129,7 +133,7 @@ func CreateRPCInvoice(invoice *channeldb.Invoice,
 			rpcHtlc.Amp = &lnrpc.AMP{
 				RootShare:  rootShare[:],
 				SetId:      setID[:],
-				ChildIndex: uint32(htlc.AMP.Record.ChildIndex()),
+				ChildIndex: htlc.AMP.Record.ChildIndex(),
 				Hash:       htlc.AMP.Hash[:],
 				Preimage:   preimage,
 			}
@@ -144,8 +148,8 @@ func CreateRPCInvoice(invoice *channeldb.Invoice,
 	}
 
 	rpcInvoice := &lnrpc.Invoice{
-		Memo:            string(invoice.Memo[:]),
-		RHash:           decoded.PaymentHash[:],
+		Memo:            string(invoice.Memo),
+		RHash:           rHash,
 		Value:           int64(satAmt),
 		ValueMsat:       int64(invoice.Terms.Value),
 		CreationDate:    invoice.CreationDate.Unix(),

lnrpc/routerrpc/router.swagger.json

@@ -441,6 +441,23 @@
       ],
       "default": "IN_FLIGHT"
     },
+    "lnrpcAMPRecord": {
+      "type": "object",
+      "properties": {
+        "root_share": {
+          "type": "string",
+          "format": "byte"
+        },
+        "set_id": {
+          "type": "string",
+          "format": "byte"
+        },
+        "child_index": {
+          "type": "integer",
+          "format": "int64"
+        }
+      }
+    },
     "lnrpcChannelPoint": {
       "type": "object",
       "properties": {
@@ -677,7 +694,11 @@
         },
         "mpp_record": {
           "$ref": "#/definitions/lnrpcMPPRecord",
-          "description": "An optional TLV record that signals the use of an MPP payment. If present,\nthe receiver will enforce that that the same mpp_record is included in the\nfinal hop payload of all non-zero payments in the HTLC set. If empty, a\nregular single-shot payment is or was attempted."
+          "description": "An optional TLV record that signals the use of an MPP payment. If present,\nthe receiver will enforce that the same mpp_record is included in the final\nhop payload of all non-zero payments in the HTLC set. If empty, a regular\nsingle-shot payment is or was attempted."
+        },
+        "amp_record": {
+          "$ref": "#/definitions/lnrpcAMPRecord",
+          "description": "An optional TLV record that signals the use of an AMP payment. If present,\nthe receiver will treat all received payments including the same\n(payment_addr, set_id) pair  as being part of one logical payment. The\npayment will be settled by XORing the root_share's together and deriving the\nchild hashes and preimages according to BOLT XX. Must be used in conjunction\nwith mpp_record."
         },
         "custom_records": {
           "type": "object",

lnrpc/routerrpc/router_backend.go

@@ -455,6 +455,11 @@ func UnmarshallHopWithPubkey(rpcHop *lnrpc.Hop, pubkey route.Vertex) (*route.Hop
 		return nil, err
 	}
 
+	amp, err := UnmarshalAMP(rpcHop.AmpRecord)
+	if err != nil {
+		return nil, err
+	}
+
 	return &route.Hop{
 		OutgoingTimeLock: rpcHop.Expiry,
 		AmtToForward:     lnwire.MilliSatoshi(rpcHop.AmtToForwardMsat),
@@ -463,6 +468,7 @@ func UnmarshallHopWithPubkey(rpcHop *lnrpc.Hop, pubkey route.Vertex) (*route.Hop
 		CustomRecords:    customRecords,
 		LegacyPayload:    !rpcHop.TlvPayload,
 		MPP:              mpp,
+		AMP:              amp,
 	}, nil
 }
 
@@ -895,6 +901,32 @@ func UnmarshalMPP(reqMPP *lnrpc.MPPRecord) (*record.MPP, error) {
 	return record.NewMPP(total, addr), nil
 }
 
+func UnmarshalAMP(reqAMP *lnrpc.AMPRecord) (*record.AMP, error) {
+	if reqAMP == nil {
+		return nil, nil
+	}
+
+	reqRootShare := reqAMP.RootShare
+	reqSetID := reqAMP.SetId
+
+	switch {
+	case len(reqRootShare) != 32:
+		return nil, errors.New("AMP root_share must be 32 bytes")
+
+	case len(reqSetID) != 32:
+		return nil, errors.New("AMP set_id must be 32 bytes")
+	}
+
+	var (
+		rootShare [32]byte
+		setID     [32]byte
+	)
+	copy(rootShare[:], reqRootShare)
+	copy(setID[:], reqSetID)
+
+	return record.NewAMP(rootShare, setID, reqAMP.ChildIndex), nil
+}
+
 // MarshalHTLCAttempt constructs an RPC HTLCAttempt from the db representation.
 func (r *RouterBackend) MarshalHTLCAttempt(
 	htlc channeldb.HTLCAttempt) (*lnrpc.HTLCAttempt, error) {

lnrpc/routerrpc/router_backend_test.go

@@ -12,6 +12,7 @@ import (
 	"github.com/lightningnetwork/lnd/record"
 	"github.com/lightningnetwork/lnd/routing"
 	"github.com/lightningnetwork/lnd/routing/route"
+	"github.com/stretchr/testify/require"
 
 	"github.com/lightningnetwork/lnd/lnrpc"
 )
@@ -239,18 +240,18 @@ func (m *mockMissionControl) GetPairHistorySnapshot(fromNode,
 	return routing.TimedPairResult{}
 }
 
-type mppOutcome byte
+type recordParseOutcome byte
 
 const (
-	valid mppOutcome = iota
+	valid recordParseOutcome = iota
 	invalid
-	nompp
+	norecord
 )
 
 type unmarshalMPPTest struct {
 	name    string
 	mpp     *lnrpc.MPPRecord
-	outcome mppOutcome
+	outcome recordParseOutcome
 }
 
 // TestUnmarshalMPP checks both positive and negative cases of UnmarshalMPP to
@@ -262,7 +263,7 @@ func TestUnmarshalMPP(t *testing.T) {
 		{
 			name:    "nil record",
 			mpp:     nil,
-			outcome: nompp,
+			outcome: norecord,
 		},
 		{
 			name: "invalid total or addr",
@@ -346,7 +347,7 @@ func testUnmarshalMPP(t *testing.T, test unmarshalMPPTest) {
 
 	// Arguments that produce no MPP field should return no error and no MPP
 	// record.
-	case nompp:
+	case norecord:
 		if err != nil {
 			t.Fatalf("failure for args resulting for no-mpp")
 		}
@@ -358,3 +359,95 @@ func testUnmarshalMPP(t *testing.T, test unmarshalMPPTest) {
 		t.Fatalf("test case has non-standard outcome")
 	}
 }
+
+type unmarshalAMPTest struct {
+	name    string
+	amp     *lnrpc.AMPRecord
+	outcome recordParseOutcome
+}
+
+// TestUnmarshalAMP asserts the behavior of decoding an RPC AMPRecord.
+func TestUnmarshalAMP(t *testing.T) {
+	rootShare := bytes.Repeat([]byte{0x01}, 32)
+	setID := bytes.Repeat([]byte{0x02}, 32)
+
+	// All child indexes are valid.
+	childIndex := uint32(3)
+
+	tests := []unmarshalAMPTest{
+		{
+			name:    "nil record",
+			amp:     nil,
+			outcome: norecord,
+		},
+		{
+			name: "invalid root share invalid set id",
+			amp: &lnrpc.AMPRecord{
+				RootShare:  []byte{0x01},
+				SetId:      []byte{0x02},
+				ChildIndex: childIndex,
+			},
+			outcome: invalid,
+		},
+		{
+			name: "valid root share invalid set id",
+			amp: &lnrpc.AMPRecord{
+				RootShare:  rootShare,
+				SetId:      []byte{0x02},
+				ChildIndex: childIndex,
+			},
+			outcome: invalid,
+		},
+		{
+			name: "invalid root share valid set id",
+			amp: &lnrpc.AMPRecord{
+				RootShare:  []byte{0x01},
+				SetId:      setID,
+				ChildIndex: childIndex,
+			},
+			outcome: invalid,
+		},
+		{
+			name: "valid root share valid set id",
+			amp: &lnrpc.AMPRecord{
+				RootShare:  rootShare,
+				SetId:      setID,
+				ChildIndex: childIndex,
+			},
+			outcome: valid,
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			testUnmarshalAMP(t, test)
+		})
+	}
+}
+
+func testUnmarshalAMP(t *testing.T, test unmarshalAMPTest) {
+	amp, err := UnmarshalAMP(test.amp)
+	switch test.outcome {
+	case valid:
+		require.NoError(t, err)
+		require.NotNil(t, amp)
+
+		rootShare := amp.RootShare()
+		setID := amp.SetID()
+		require.Equal(t, test.amp.RootShare, rootShare[:])
+		require.Equal(t, test.amp.SetId, setID[:])
+		require.Equal(t, test.amp.ChildIndex, amp.ChildIndex())
+
+	case invalid:
+		require.Error(t, err)
+		require.Nil(t, amp)
+
+	case norecord:
+		require.NoError(t, err)
+		require.Nil(t, amp)
+
+	default:
+		t.Fatalf("test case has non-standard outcome")
+	}
+}

lnrpc/rpc.proto

@@ -2493,12 +2493,22 @@ message Hop {
 
     /*
     An optional TLV record that signals the use of an MPP payment. If present,
-    the receiver will enforce that that the same mpp_record is included in the
-    final hop payload of all non-zero payments in the HTLC set. If empty, a
-    regular single-shot payment is or was attempted.
+    the receiver will enforce that the same mpp_record is included in the final
+    hop payload of all non-zero payments in the HTLC set. If empty, a regular
+    single-shot payment is or was attempted.
     */
     MPPRecord mpp_record = 10;
 
+    /*
+    An optional TLV record that signals the use of an AMP payment. If present,
+    the receiver will treat all received payments including the same
+    (payment_addr, set_id) pair  as being part of one logical payment. The
+    payment will be settled by XORing the root_share's together and deriving the
+    child hashes and preimages according to BOLT XX. Must be used in conjunction
+    with mpp_record.
+    */
+    AMPRecord amp_record = 12;
+
     /*
     An optional set of key-value TLV records. This is useful within the context
     of the SendToRoute call as it allows callers to specify arbitrary K-V pairs
@@ -2525,6 +2535,14 @@ message MPPRecord {
     int64 total_amt_msat = 10;
 }
 
+message AMPRecord {
+    bytes root_share = 1;
+
+    bytes set_id = 2;
+
+    uint32 child_index = 3;
+}
+
 /*
 A path through the channel graph which runs over one or more channels in
 succession. This struct carries all the information required to craft the

lnrpc/rpc.swagger.json

@@ -2536,6 +2536,23 @@
       },
       "description": "Details specific to AMP HTLCs."
     },
+    "lnrpcAMPRecord": {
+      "type": "object",
+      "properties": {
+        "root_share": {
+          "type": "string",
+          "format": "byte"
+        },
+        "set_id": {
+          "type": "string",
+          "format": "byte"
+        },
+        "child_index": {
+          "type": "integer",
+          "format": "int64"
+        }
+      }
+    },
     "lnrpcAbandonChannelResponse": {
       "type": "object"
     },
@@ -4025,7 +4042,11 @@
         },
         "mpp_record": {
           "$ref": "#/definitions/lnrpcMPPRecord",
-          "description": "An optional TLV record that signals the use of an MPP payment. If present,\nthe receiver will enforce that that the same mpp_record is included in the\nfinal hop payload of all non-zero payments in the HTLC set. If empty, a\nregular single-shot payment is or was attempted."
+          "description": "An optional TLV record that signals the use of an MPP payment. If present,\nthe receiver will enforce that the same mpp_record is included in the final\nhop payload of all non-zero payments in the HTLC set. If empty, a regular\nsingle-shot payment is or was attempted."
+        },
+        "amp_record": {
+          "$ref": "#/definitions/lnrpcAMPRecord",
+          "description": "An optional TLV record that signals the use of an AMP payment. If present,\nthe receiver will treat all received payments including the same\n(payment_addr, set_id) pair  as being part of one logical payment. The\npayment will be settled by XORing the root_share's together and deriving the\nchild hashes and preimages according to BOLT XX. Must be used in conjunction\nwith mpp_record."
         },
         "custom_records": {
           "type": "object",

lntest/itest/lnd_amp_test.go

@@ -0,0 +1,208 @@
+package itest
+
+import (
+	"context"
+	"crypto/rand"
+	"time"
+
+	"github.com/btcsuite/btcutil"
+	"github.com/lightningnetwork/lnd/amp"
+	"github.com/lightningnetwork/lnd/lnrpc"
+	"github.com/lightningnetwork/lnd/lnrpc/routerrpc"
+	"github.com/lightningnetwork/lnd/lntest"
+	"github.com/lightningnetwork/lnd/lntypes"
+	"github.com/stretchr/testify/require"
+)
+
+func testSendToRouteAMP(net *lntest.NetworkHarness, t *harnessTest) {
+	ctxb := context.Background()
+
+	ctx := newMppTestContext(t, net)
+	defer ctx.shutdownNodes()
+
+	const (
+		paymentAmt = btcutil.Amount(300000)
+		numShards  = 3
+		shardAmt   = paymentAmt / numShards
+		chanAmt    = shardAmt * 3 / 2
+	)
+
+	// Set up a network with three different paths Alice <-> Bob.
+	//              _ Eve _
+	//             /       \
+	// Alice -- Carol ---- Bob
+	//      \              /
+	//       \__ Dave ____/
+	//
+	ctx.openChannel(ctx.carol, ctx.bob, chanAmt)
+	ctx.openChannel(ctx.dave, ctx.bob, chanAmt)
+	ctx.openChannel(ctx.alice, ctx.dave, chanAmt)
+	ctx.openChannel(ctx.eve, ctx.bob, chanAmt)
+	ctx.openChannel(ctx.carol, ctx.eve, chanAmt)
+
+	// Since the channel Alice-> Carol will have to carry two
+	// shards, we make it larger.
+	ctx.openChannel(ctx.alice, ctx.carol, chanAmt+shardAmt)
+
+	defer ctx.closeChannels()
+
+	ctx.waitForChannels()
+
+	// We'll send shards along three routes from Alice.
+	sendRoutes := [numShards][]*lntest.HarnessNode{
+		{ctx.carol, ctx.bob},
+		{ctx.dave, ctx.bob},
+		{ctx.carol, ctx.eve, ctx.bob},
+	}
+
+	payAddr := make([]byte, 32)
+	_, err := rand.Read(payAddr)
+	require.NoError(t.t, err)
+
+	setID := make([]byte, 32)
+	_, err = rand.Read(setID)
+	require.NoError(t.t, err)
+
+	var sharer amp.Sharer
+	sharer, err = amp.NewSeedSharer()
+	require.NoError(t.t, err)
+
+	childPreimages := make(map[lntypes.Preimage]uint32)
+	responses := make(chan *lnrpc.HTLCAttempt, len(sendRoutes))
+	for i, hops := range sendRoutes {
+		// Build a route for the specified hops.
+		r, err := ctx.buildRoute(ctxb, shardAmt, net.Alice, hops)
+		if err != nil {
+			t.Fatalf("unable to build route: %v", err)
+		}
+
+		// Set the MPP records to indicate this is a payment shard.
+		hop := r.Hops[len(r.Hops)-1]
+		hop.TlvPayload = true
+		hop.MppRecord = &lnrpc.MPPRecord{
+			PaymentAddr:  payAddr,
+			TotalAmtMsat: int64(paymentAmt * 1000),
+		}
+
+		var child *amp.Child
+		if i < len(sendRoutes)-1 {
+			var left amp.Sharer
+			left, sharer, err = sharer.Split()
+			require.NoError(t.t, err)
+
+			child = left.Child(uint32(i))
+		} else {
+			child = sharer.Child(uint32(i))
+		}
+		childPreimages[child.Preimage] = child.Index
+
+		hop.AmpRecord = &lnrpc.AMPRecord{
+			RootShare:  child.Share[:],
+			SetId:      setID,
+			ChildIndex: child.Index,
+		}
+
+		// Send the shard.
+		sendReq := &routerrpc.SendToRouteRequest{
+			PaymentHash: child.Hash[:],
+			Route:       r,
+		}
+
+		// We'll send all shards in their own goroutine, since SendToRoute will
+		// block as long as the payment is in flight.
+		go func() {
+			ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
+			resp, err := net.Alice.RouterClient.SendToRouteV2(ctxt, sendReq)
+			if err != nil {
+				t.Fatalf("unable to send payment: %v", err)
+			}
+
+			responses <- resp
+		}()
+	}
+
+	// Assert that all of the child preimages are unique.
+	require.Equal(t.t, len(sendRoutes), len(childPreimages))
+
+	// Make a copy of the childPreimages map for validating the resulting
+	// invoice.
+	childPreimagesCopy := make(map[lntypes.Preimage]uint32)
+	for preimage, childIndex := range childPreimages {
+		childPreimagesCopy[preimage] = childIndex
+	}
+
+	// Wait for all responses to be back, and check that they all
+	// succeeded.
+	for range sendRoutes {
+		var resp *lnrpc.HTLCAttempt
+		select {
+		case resp = <-responses:
+		case <-time.After(defaultTimeout):
+			t.Fatalf("response not received")
+		}
+
+		if resp.Failure != nil {
+			t.Fatalf("received payment failure : %v", resp.Failure)
+		}
+
+		preimage, err := lntypes.MakePreimage(resp.Preimage)
+		require.NoError(t.t, err)
+
+		// Assert that the response includes one of our child preimages.
+		_, ok := childPreimages[preimage]
+		require.True(t.t, ok)
+
+		// Remove this preimage from out set so that we ensure all
+		// responses have a unique child preimage.
+		delete(childPreimages, preimage)
+	}
+	childPreimages = childPreimagesCopy
+
+	// Fetch Bob's invoices.
+	invoiceResp, err := net.Bob.ListInvoices(
+		ctxb, &lnrpc.ListInvoiceRequest{},
+	)
+	require.NoError(t.t, err)
+
+	// There should only be one invoice.
+	require.Equal(t.t, 1, len(invoiceResp.Invoices))
+	rpcInvoice := invoiceResp.Invoices[0]
+
+	// Assert that the invoice is settled for the total payment amount and
+	// has the correct payment address.
+	require.True(t.t, rpcInvoice.Settled)
+	require.Equal(t.t, lnrpc.Invoice_SETTLED, rpcInvoice.State)
+	require.Equal(t.t, int64(paymentAmt), rpcInvoice.AmtPaidSat)
+	require.Equal(t.t, int64(paymentAmt*1000), rpcInvoice.AmtPaidMsat)
+	require.Equal(t.t, payAddr, rpcInvoice.PaymentAddr)
+
+	// Finally, assert that the proper set id is recorded for each htlc, and
+	// that the preimage hash pair is valid.
+	require.Equal(t.t, numShards, len(rpcInvoice.Htlcs))
+	for _, htlc := range rpcInvoice.Htlcs {
+		require.NotNil(t.t, htlc.Amp)
+		require.Equal(t.t, setID, htlc.Amp.SetId)
+
+		// Parse the child hash and child preimage, and assert they are
+		// well-formed.
+		childHash, err := lntypes.MakeHash(htlc.Amp.Hash)
+		require.NoError(t.t, err)
+		childPreimage, err := lntypes.MakePreimage(htlc.Amp.Preimage)
+		require.NoError(t.t, err)
+
+		// Assert that the preimage actually matches the hashes.
+		validPreimage := childPreimage.Matches(childHash)
+		require.True(t.t, validPreimage)
+
+		// Assert that the HTLC includes one of our child preimages.
+		childIndex, ok := childPreimages[childPreimage]
+		require.True(t.t, ok)
+
+		// Assert that the correct child index is reflected.
+		require.Equal(t.t, childIndex, htlc.Amp.ChildIndex)
+
+		// Remove this preimage from our set so that we ensure all HTLCs
+		// have a unique child preimage.
+		delete(childPreimages, childPreimage)
+	}
+}

lntest/itest/lnd_mpp_test.go

@@ -74,36 +74,6 @@ func testSendToRouteMultiPath(net *lntest.NetworkHarness, t *harnessTest) {
 
 	payAddr := decodeResp.PaymentAddr
 
-	// Helper function for Alice to build a route from pubkeys.
-	buildRoute := func(amt btcutil.Amount, hops []*lntest.HarnessNode) (
-		*lnrpc.Route, error) {
-
-		rpcHops := make([][]byte, 0, len(hops))
-		for _, hop := range hops {
-			k := hop.PubKeyStr
-			pubkey, err := route.NewVertexFromStr(k)
-			if err != nil {
-				return nil, fmt.Errorf("error parsing %v: %v",
-					k, err)
-			}
-			rpcHops = append(rpcHops, pubkey[:])
-		}
-
-		req := &routerrpc.BuildRouteRequest{
-			AmtMsat:        int64(amt * 1000),
-			FinalCltvDelta: chainreg.DefaultBitcoinTimeLockDelta,
-			HopPubkeys:     rpcHops,
-		}
-
-		ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
-		routeResp, err := net.Alice.RouterClient.BuildRoute(ctxt, req)
-		if err != nil {
-			return nil, err
-		}
-
-		return routeResp.Route, nil
-	}
-
 	// We'll send shards along three routes from Alice.
 	sendRoutes := [][]*lntest.HarnessNode{
 		{ctx.carol, ctx.bob},
@@ -114,7 +84,7 @@ func testSendToRouteMultiPath(net *lntest.NetworkHarness, t *harnessTest) {
 	responses := make(chan *lnrpc.HTLCAttempt, len(sendRoutes))
 	for _, hops := range sendRoutes {
 		// Build a route for the specified hops.
-		r, err := buildRoute(shardAmt, hops)
+		r, err := ctx.buildRoute(ctxb, shardAmt, net.Alice, hops)
 		if err != nil {
 			t.Fatalf("unable to build route: %v", err)
 		}
@@ -394,3 +364,34 @@ func (c *mppTestContext) waitForChannels() {
 		}
 	}
 }
+
+// Helper function for Alice to build a route from pubkeys.
+func (c *mppTestContext) buildRoute(ctxb context.Context, amt btcutil.Amount,
+	sender *lntest.HarnessNode, hops []*lntest.HarnessNode) (*lnrpc.Route,
+	error) {
+
+	rpcHops := make([][]byte, 0, len(hops))
+	for _, hop := range hops {
+		k := hop.PubKeyStr
+		pubkey, err := route.NewVertexFromStr(k)
+		if err != nil {
+			return nil, fmt.Errorf("error parsing %v: %v",
+				k, err)
+		}
+		rpcHops = append(rpcHops, pubkey[:])
+	}
+
+	req := &routerrpc.BuildRouteRequest{
+		AmtMsat:        int64(amt * 1000),
+		FinalCltvDelta: chainreg.DefaultBitcoinTimeLockDelta,
+		HopPubkeys:     rpcHops,
+	}
+
+	ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
+	routeResp, err := sender.RouterClient.BuildRoute(ctxt, req)
+	if err != nil {
+		return nil, err
+	}
+
+	return routeResp.Route, nil
+}

lntest/itest/lnd_test_list_on_test.go

@@ -266,6 +266,10 @@ var allTestCases = []*testCase{
 		name: "sendtoroute multi path payment",
 		test: testSendToRouteMultiPath,
 	},
+	{
+		name: "sendtoroute amp",
+		test: testSendToRouteAMP,
+	},
 	{
 		name: "send multi path payment",
 		test: testSendMultiPathPayment,

lnwire/features.go

@@ -129,6 +129,16 @@ const (
 	// transactions, which also imply anchor commitments.
 	AnchorsZeroFeeHtlcTxOptional FeatureBit = 23
 
+	// AMPRequired is a required feature bit that signals that the receiver
+	// of a payment supports accepts spontaneous payments, i.e.
+	// sender-generated preimages according to BOLT XX.
+	AMPRequired FeatureBit = 30
+
+	// AMPOptional is an optional feature bit that signals that the receiver
+	// of a payment supports accepts spontaneous payments, i.e.
+	// sender-generated preimages according to BOLT XX.
+	AMPOptional FeatureBit = 31
+
 	// maxAllowedSize is a maximum allowed size of feature vector.
 	//
 	// NOTE: Within the protocol, the maximum allowed message size is 65535
@@ -172,6 +182,8 @@ var Features = map[FeatureBit]string{
 	AnchorsZeroFeeHtlcTxOptional:  "anchors-zero-fee-htlc-tx",
 	WumboChannelsRequired:         "wumbo-channels",
 	WumboChannelsOptional:         "wumbo-channels",
+	AMPRequired:                   "amp",
+	AMPOptional:                   "amp",
 }
 
 // RawFeatureVector represents a set of feature bits as defined in BOLT-09.  A

record/amp.go

@@ -9,19 +9,19 @@ import (
 
 // AMPOnionType is the type used in the onion to reference the AMP fields:
 // root_share, set_id, and child_index.
-const AMPOnionType tlv.Type = 10
+const AMPOnionType tlv.Type = 14
 
 // AMP is a record that encodes the fields necessary for atomic multi-path
 // payments.
 type AMP struct {
 	rootShare  [32]byte
 	setID      [32]byte
-	childIndex uint16
+	childIndex uint32
 }
 
 // NewAMP generate a new AMP record with the given root_share, set_id, and
 // child_index.
-func NewAMP(rootShare, setID [32]byte, childIndex uint16) *AMP {
+func NewAMP(rootShare, setID [32]byte, childIndex uint32) *AMP {
 	return &AMP{
 		rootShare:  rootShare,
 		setID:      setID,
@@ -40,7 +40,7 @@ func (a *AMP) SetID() [32]byte {
 }
 
 // ChildIndex returns the child index contained in the AMP record.
-func (a *AMP) ChildIndex() uint16 {
+func (a *AMP) ChildIndex() uint32 {
 	return a.childIndex
 }
 
@@ -55,7 +55,7 @@ func AMPEncoder(w io.Writer, val interface{}, buf *[8]byte) error {
 			return err
 		}
 
-		return tlv.ETUint16T(w, v.childIndex, buf)
+		return tlv.ETUint32T(w, v.childIndex, buf)
 	}
 	return tlv.NewTypeForEncodingErr(val, "AMP")
 }
@@ -69,7 +69,7 @@ const (
 	// maxAMPLength is the maximum legnth of a serialized AMP TLV record,
 	// which occurs when the truncated endoing of a child_index takes 2
 	// bytes.
-	maxAMPLength = 66
+	maxAMPLength = 68
 )
 
 // AMPDecoder reads the AMP record from the provided io.Reader.
@@ -83,7 +83,7 @@ func AMPDecoder(r io.Reader, val interface{}, buf *[8]byte, l uint64) error {
 			return err
 		}
 
-		return tlv.DTUint16(r, &v.childIndex, buf, l-64)
+		return tlv.DTUint32(r, &v.childIndex, buf, l-minAMPLength)
 	}
 	return tlv.NewTypeForDecodingErr(val, "AMP", l, maxAMPLength)
 }
@@ -97,7 +97,7 @@ func (a *AMP) Record() tlv.Record {
 
 // PayloadSize returns the size this record takes up in encoded form.
 func (a *AMP) PayloadSize() uint64 {
-	return 32 + 32 + tlv.SizeTUint16(a.childIndex)
+	return 32 + 32 + tlv.SizeTUint32(a.childIndex)
 }
 
 // String returns a human-readble description of the amp payload fields.

record/record_test.go

@@ -21,7 +21,7 @@ var (
 	testAddr       = [32]byte{0x01, 0x02}
 	testShare      = [32]byte{0x03, 0x04}
 	testSetID      = [32]byte{0x05, 0x06}
-	testChildIndex = uint16(17)
+	testChildIndex = uint32(17)
 )
 
 var recordEncDecTests = []recordEncDecTest{