multi: update channel db HTLC OnionBlob to array

We know that onion blobs in lightning are _exactly_ 1366 bytes in
lightning, but they are currently expressed as a byte slice in
channeldb's HTLC struct. Blobs are currently serialized as var bytes,
so we can take advantage of this known length and variable length
to add additional data to the inline serialization of our HTLCs, which
are otherwise not easily extensible (without creating a new bucket).

channeldb/channel.go

@@ -2001,15 +2001,15 @@ func (c *OpenChannel) ActiveHtlcs() []HTLC {
 	// which ones are present on their commitment.
 	remoteHtlcs := make(map[[32]byte]struct{})
 	for _, htlc := range c.RemoteCommitment.Htlcs {
-		onionHash := sha256.Sum256(htlc.OnionBlob)
+		onionHash := sha256.Sum256(htlc.OnionBlob[:])
 		remoteHtlcs[onionHash] = struct{}{}
 	}
 
 	// Now that we know which HTLC's they have, we'll only mark the HTLC's
 	// as active if *we* know them as well.
 	activeHtlcs := make([]HTLC, 0, len(remoteHtlcs))
 	for _, htlc := range c.LocalCommitment.Htlcs {
-		onionHash := sha256.Sum256(htlc.OnionBlob)
+		onionHash := sha256.Sum256(htlc.OnionBlob[:])
 		if _, ok := remoteHtlcs[onionHash]; !ok {
 			continue
 		}
@@ -2056,7 +2056,7 @@ type HTLC struct {
 
 	// OnionBlob is an opaque blob which is used to complete multi-hop
 	// routing.
-	OnionBlob []byte
+	OnionBlob [lnwire.OnionPacketSize]byte
 
 	// HtlcIndex is the HTLC counter index of this active, outstanding
 	// HTLC. This differs from the LogIndex, as the HtlcIndex is only
@@ -2113,14 +2113,17 @@ func DeserializeHtlcs(r io.Reader) ([]HTLC, error) {
 
 	htlcs = make([]HTLC, numHtlcs)
 	for i := uint16(0); i < numHtlcs; i++ {
+		var onionBlob []byte
 		if err := ReadElements(r,
 			&htlcs[i].Signature, &htlcs[i].RHash, &htlcs[i].Amt,
 			&htlcs[i].RefundTimeout, &htlcs[i].OutputIndex,
-			&htlcs[i].Incoming, &htlcs[i].OnionBlob,
+			&htlcs[i].Incoming, &onionBlob,
 			&htlcs[i].HtlcIndex, &htlcs[i].LogIndex,
 		); err != nil {
 			return htlcs, err
 		}
+
+		copy(htlcs[i].OnionBlob[:], onionBlob)
 	}
 
 	return htlcs, nil

channeldb/channel_test.go

@@ -19,6 +19,7 @@ import (
 	"github.com/lightningnetwork/lnd/clock"
 	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/kvdb"
+	"github.com/lightningnetwork/lnd/lnmock"
 	"github.com/lightningnetwork/lnd/lntest/channels"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/shachain"
@@ -366,12 +367,13 @@ func TestOpenChannelPutGetDelete(t *testing.T) {
 	// Create the test channel state, with additional htlcs on the local
 	// and remote commitment.
 	localHtlcs := []HTLC{
-		{Signature: testSig.Serialize(),
+		{
+			Signature:     testSig.Serialize(),
 			Incoming:      true,
 			Amt:           10,
 			RHash:         key,
 			RefundTimeout: 1,
-			OnionBlob:     []byte("onionblob"),
+			OnionBlob:     lnmock.MockOnion(),
 		},
 	}
 
@@ -382,7 +384,7 @@ func TestOpenChannelPutGetDelete(t *testing.T) {
 			Amt:           10,
 			RHash:         key,
 			RefundTimeout: 1,
-			OnionBlob:     []byte("onionblob"),
+			OnionBlob:     lnmock.MockOnion(),
 		},
 	}
 
@@ -612,8 +614,10 @@ func TestChannelStateTransition(t *testing.T) {
 			LogIndex:      uint64(i * 2),
 			HtlcIndex:     uint64(i),
 		}
-		htlc.OnionBlob = make([]byte, 10)
-		copy(htlc.OnionBlob[:], bytes.Repeat([]byte{2}, 10))
+		copy(
+			htlc.OnionBlob[:],
+			bytes.Repeat([]byte{2}, lnwire.OnionPacketSize),
+		)
 		htlcs = append(htlcs, htlc)
 		htlcAmt += htlc.Amt
 	}

contractcourt/briefcase_test.go

@@ -16,6 +16,7 @@ import (
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/kvdb"
+	"github.com/lightningnetwork/lnd/lnmock"
 	"github.com/lightningnetwork/lnd/lntest/channels"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/stretchr/testify/require"
@@ -745,7 +746,7 @@ func TestCommitSetStorage(t *testing.T) {
 	activeHTLCs := []channeldb.HTLC{
 		{
 			Amt:       1000,
-			OnionBlob: make([]byte, 0),
+			OnionBlob: lnmock.MockOnion(),
 			Signature: make([]byte, 0),
 		},
 	}

contractcourt/htlc_incoming_contest_resolver.go

@@ -487,7 +487,7 @@ func (h *htlcIncomingContestResolver) Supplement(htlc channeldb.HTLC) {
 func (h *htlcIncomingContestResolver) decodePayload() (*hop.Payload,
 	[]byte, error) {
 
-	onionReader := bytes.NewReader(h.htlc.OnionBlob)
+	onionReader := bytes.NewReader(h.htlc.OnionBlob[:])
 	iterator, err := h.OnionProcessor.ReconstructHopIterator(
 		onionReader, h.htlc.RHash[:],
 	)

contractcourt/htlc_incoming_resolver_test.go

@@ -13,6 +13,7 @@ import (
 	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/invoices"
 	"github.com/lightningnetwork/lnd/kvdb"
+	"github.com/lightningnetwork/lnd/lnmock"
 	"github.com/lightningnetwork/lnd/lntest/mock"
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwallet"
@@ -29,7 +30,6 @@ var (
 	testResPreimage         = lntypes.Preimage{1, 2, 3}
 	testResHash             = testResPreimage.Hash()
 	testResCircuitKey       = models.CircuitKey{}
-	testOnionBlob           = []byte{4, 5, 6}
 	testAcceptHeight  int32 = 1234
 	testHtlcAmount          = 2300
 )
@@ -139,8 +139,9 @@ func TestHtlcIncomingResolverExitSettle(t *testing.T) {
 
 	ctx.waitForResult(true)
 
+	expetedOnion := lnmock.MockOnion()
 	if !bytes.Equal(
-		ctx.onionProcessor.offeredOnionBlob, testOnionBlob,
+		ctx.onionProcessor.offeredOnionBlob, expetedOnion[:],
 	) {
 
 		t.Fatal("unexpected onion blob")
@@ -375,7 +376,7 @@ func newIncomingResolverTestContext(t *testing.T, isExit bool) *incomingResolver
 			htlc: channeldb.HTLC{
 				Amt:       lnwire.MilliSatoshi(testHtlcAmount),
 				RHash:     testResHash,
-				OnionBlob: testOnionBlob,
+				OnionBlob: lnmock.MockOnion(),
 			},
 		},
 		htlcExpiry: testHtlcExpiry,

contractcourt/htlc_outgoing_contest_resolver_test.go

@@ -9,6 +9,7 @@ import (
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/kvdb"
+	"github.com/lightningnetwork/lnd/lnmock"
 	"github.com/lightningnetwork/lnd/lntest/mock"
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwallet"
@@ -183,7 +184,7 @@ func newOutgoingResolverTestContext(t *testing.T) *outgoingResolverTestContext {
 			htlc: channeldb.HTLC{
 				Amt:       lnwire.MilliSatoshi(testHtlcAmount),
 				RHash:     testResHash,
-				OnionBlob: testOnionBlob,
+				OnionBlob: lnmock.MockOnion(),
 			},
 		},
 	}

contractcourt/htlc_success_resolver_test.go

@@ -14,6 +14,7 @@ import (
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/kvdb"
+	"github.com/lightningnetwork/lnd/lnmock"
 	"github.com/lightningnetwork/lnd/lntest/mock"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwire"
@@ -110,7 +111,7 @@ func newHtlcResolverTestContext(t *testing.T,
 
 	htlc := channeldb.HTLC{
 		RHash:     testResHash,
-		OnionBlob: testOnionBlob,
+		OnionBlob: lnmock.MockOnion(),
 		Amt:       testHtlcAmt,
 	}
 

lnmock/routing.go

@@ -0,0 +1,16 @@
+package lnmock
+
+import (
+	"bytes"
+
+	"github.com/lightningnetwork/lnd/lnwire"
+)
+
+// MockOnion returns a mock onion payload.
+func MockOnion() [lnwire.OnionPacketSize]byte {
+	var onion [lnwire.OnionPacketSize]byte
+	onionBlob := bytes.Repeat([]byte{1}, lnwire.OnionPacketSize)
+	copy(onion[:], onionBlob)
+
+	return onion
+}

lnwallet/channel.go

@@ -745,7 +745,6 @@ func (c *commitment) toDiskCommit(ourCommit bool) *channeldb.ChannelCommitment {
 			LogIndex:      htlc.LogIndex,
 			Incoming:      false,
 		}
-		h.OnionBlob = make([]byte, len(htlc.OnionBlob))
 		copy(h.OnionBlob[:], htlc.OnionBlob)
 
 		if ourCommit && htlc.sig != nil {
@@ -770,7 +769,6 @@ func (c *commitment) toDiskCommit(ourCommit bool) *channeldb.ChannelCommitment {
 			LogIndex:      htlc.LogIndex,
 			Incoming:      true,
 		}
-		h.OnionBlob = make([]byte, len(htlc.OnionBlob))
 		copy(h.OnionBlob[:], htlc.OnionBlob)
 
 		if ourCommit && htlc.sig != nil {
@@ -859,7 +857,7 @@ func (lc *LightningChannel) diskHtlcToPayDesc(feeRate chainfee.SatPerKWeight,
 		EntryType:          Add,
 		HtlcIndex:          htlc.HtlcIndex,
 		LogIndex:           htlc.LogIndex,
-		OnionBlob:          htlc.OnionBlob,
+		OnionBlob:          htlc.OnionBlob[:],
 		localOutputIndex:   localOutputIndex,
 		remoteOutputIndex:  remoteOutputIndex,
 		ourPkScript:        ourP2WSH,