htlcswicth+channel: switch to store onion blobs in payment descriptor

After addition of the retransmission logic in the channel link, we
should make the onion blobs persistant, the proper way to do this is
include the onion blobs in the payment descriptor rather than storing
them in the distinct struct in the channel link.

htlcswitch/link.go

@@ -166,16 +166,6 @@ type channelLink struct {
 	// htlc cancel reasons.
 	cancelReasons map[uint64]lnwire.OpaqueReason
 
-	// clearedOnionBlobs tracks the remote log index of the incoming
-	// htlc's, mapped to the htlc onion blob which encapsulates the next
-	// hop. HTLC's are added to this map once the HTLC has been cleared,
-	// meaning the commitment state reflects the update encoded within this
-	// HTLC.
-	//
-	// TODO(andrew.shvv) remove after payment descriptor start store
-	// htlc onion blobs.
-	clearedOnionBlobs map[uint64][lnwire.OnionPacketSize]byte
-
 	// batchCounter is the number of updates which we received from remote
 	// side, but not include in commitment transaction yet and plus the
 	// current number of settles that have been sent, but not yet committed
@@ -239,12 +229,11 @@ func NewChannelLink(cfg ChannelLinkConfig, channel *lnwallet.LightningChannel,
 	currentHeight uint32) ChannelLink {
 
 	return &channelLink{
-		cfg:               cfg,
+		cfg:         cfg,
-		channel:           channel,
+		channel:     channel,
-		clearedOnionBlobs: make(map[uint64][lnwire.OnionPacketSize]byte),
+		upstream:    make(chan lnwire.Message),
-		upstream:          make(chan lnwire.Message),
+		downstream:  make(chan *htlcPacket),
-		downstream:        make(chan *htlcPacket),
+		linkControl: make(chan interface{}),
-		linkControl:       make(chan interface{}),
 		// TODO(roasbeef): just do reserve here?
 		availableBandwidth: uint64(channel.StateSnapshot().LocalBalance),
 		cancelReasons:      make(map[uint64]lnwire.OpaqueReason),
@@ -747,11 +736,6 @@ func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
 		log.Tracef("Receive upstream htlc with payment hash(%x), "+
 			"assigning index: %v", msg.PaymentHash[:], index)
 
-		// Store the onion blob which encapsulate the htlc route and
-		// use in on stage of HTLC inclusion to retrieve the next hop
-		// and propagate the HTLC along the remaining route.
-		l.clearedOnionBlobs[index] = msg.OnionBlob
-
 	case *lnwire.UpdateFufillHTLC:
 		pre := msg.PaymentPreimage
 		idx := msg.ID
@@ -1144,8 +1128,8 @@ func (l *channelLink) processLockedInHtlcs(
 		case lnwallet.Add:
 			// Fetch the onion blob that was included within this
 			// processed payment descriptor.
-			onionBlob := l.clearedOnionBlobs[pd.HtlcIndex]
+			var onionBlob [lnwire.OnionPacketSize]byte
-			delete(l.clearedOnionBlobs, pd.HtlcIndex)
+			copy(onionBlob[:], pd.OnionBlob)
 
 			// Retrieve onion obfuscator from onion blob in order
 			// to produce initial obfuscation of the onion

lnwallet/channel.go

@@ -208,9 +208,11 @@ type PaymentDescriptor struct {
 	removeCommitHeightRemote uint64
 	removeCommitHeightLocal  uint64
 
-	// Payload is an opaque blob which is used to complete multi-hop
+	// OnionBlob is an opaque blob which is used to complete multi-hop
 	// routing.
-	Payload []byte
+	//
+	// NOTE: Populated only on add payment descriptor entry types.
+	OnionBlob []byte
 
 	// [our|their|]PkScript are the raw public key scripts that encodes the
 	// redemption rules for this particular HTLC. These fields will only be
@@ -534,6 +536,7 @@ func (c *commitment) toChannelDelta(ourCommit bool) (*channeldb.ChannelDelta, er
 			RHash:         htlc.RHash,
 			RefundTimeout: htlc.Timeout,
 			OutputIndex:   outputIndex,
+			OnionBlob:     htlc.OnionBlob,
 		}
 
 		if ourCommit && htlc.sig != nil {
@@ -1688,6 +1691,7 @@ func (lc *LightningChannel) restoreStateLogs() error {
 			EntryType:             Add,
 			addCommitHeightRemote: pastHeight,
 			addCommitHeightLocal:  pastHeight,
+			OnionBlob:             htlc.OnionBlob,
 			ourPkScript:           ourP2WSH,
 			ourWitnessScript:      ourWitnessScript,
 			theirPkScript:         theirP2WSH,
@@ -2487,7 +2491,7 @@ func (lc *LightningChannel) ReceiveReestablish(msg *lnwire.ChannelReestablish) (
 			switch htlc.EntryType {
 			case Add:
 				var onionBlob [lnwire.OnionPacketSize]byte
-				copy(onionBlob[:], htlc.Payload)
+				copy(onionBlob[:], htlc.OnionBlob)
 				updates = append(updates, &lnwire.UpdateAddHTLC{
 					ChanID:      chanID,
 					ID:          htlc.Index,
@@ -3102,6 +3106,7 @@ func (lc *LightningChannel) AddHTLC(htlc *lnwire.UpdateAddHTLC) (uint64, error)
 		Amount:    htlc.Amount,
 		LogIndex:  lc.localUpdateLog.logIndex,
 		HtlcIndex: lc.localUpdateLog.htlcCounter,
+		OnionBlob: htlc.OnionBlob[:],
 	}
 
 	lc.localUpdateLog.appendHtlc(pd)
@@ -3128,6 +3133,7 @@ func (lc *LightningChannel) ReceiveHTLC(htlc *lnwire.UpdateAddHTLC) (uint64, err
 		Amount:    htlc.Amount,
 		LogIndex:  lc.remoteUpdateLog.logIndex,
 		HtlcIndex: lc.remoteUpdateLog.htlcCounter,
+		OnionBlob: htlc.OnionBlob[:],
 	}
 
 	lc.remoteUpdateLog.appendHtlc(pd)