multi: remove debug invoices

Debug invoices are rarely used nowadays, but keep asking for maintenance
every time refactoring in primarily the invoice registry occurs. We have
passed the cost/benefit tipping point, so therefore the debug invoice
concept is removed in this commit.

Previously the debughtlc flag also controlled whether hodl masks were
active. It is safe to remove that additional condition because the hodl
masks are still guarded by the dev build tag.

htlcswitch/link.go

@@ -191,16 +191,10 @@ type ChannelLinkConfig struct {
 	// transaction to ensure timely confirmation.
 	FeeEstimator lnwallet.FeeEstimator
 
-	// DebugHTLC should be turned on if you want all HTLCs sent to a node
-	// with the debug htlc R-Hash are immediately settled in the next
-	// available state transition.
-	DebugHTLC bool
-
 	// hodl.Mask is a bitvector composed of hodl.Flags, specifying breakpoints
 	// for HTLC forwarding internal to the switch.
 	//
-	// NOTE: This should only be used for testing, and should only be used
-	// simultaneously with DebugHTLC.
+	// NOTE: This should only be used for testing.
 	HodlMask hodl.Mask
 
 	// SyncStates is used to indicate that we need send the channel
@@ -1256,7 +1250,7 @@ func (l *channelLink) handleDownStreamPkt(pkt *htlcPacket, isReProcess bool) {
 		// If hodl.AddOutgoing mode is active, we exit early to simulate
 		// arbitrary delays between the switch adding an ADD to the
 		// mailbox, and the HTLC being added to the commitment state.
-		if l.cfg.DebugHTLC && l.cfg.HodlMask.Active(hodl.AddOutgoing) {
+		if l.cfg.HodlMask.Active(hodl.AddOutgoing) {
 			l.warnf(hodl.AddOutgoing.Warning())
 			l.mailBox.AckPacket(pkt.inKey())
 			return
@@ -1378,7 +1372,7 @@ func (l *channelLink) handleDownStreamPkt(pkt *htlcPacket, isReProcess bool) {
 		// simulate arbitrary delays between the switch adding the
 		// SETTLE to the mailbox, and the HTLC being added to the
 		// commitment state.
-		if l.cfg.DebugHTLC && l.cfg.HodlMask.Active(hodl.SettleOutgoing) {
+		if l.cfg.HodlMask.Active(hodl.SettleOutgoing) {
 			l.warnf(hodl.SettleOutgoing.Warning())
 			l.mailBox.AckPacket(pkt.inKey())
 			return
@@ -1436,7 +1430,7 @@ func (l *channelLink) handleDownStreamPkt(pkt *htlcPacket, isReProcess bool) {
 		// simulate arbitrary delays between the switch adding a FAIL to
 		// the mailbox, and the HTLC being added to the commitment
 		// state.
-		if l.cfg.DebugHTLC && l.cfg.HodlMask.Active(hodl.FailOutgoing) {
+		if l.cfg.HodlMask.Active(hodl.FailOutgoing) {
 			l.warnf(hodl.FailOutgoing.Warning())
 			l.mailBox.AckPacket(pkt.inKey())
 			return
@@ -1948,7 +1942,7 @@ func (l *channelLink) updateCommitTx() error {
 	// commit any in-memory modifications to the channel state. Exiting here
 	// permits testing of either the switch or link's ability to trim
 	// circuits that have been opened, but unsuccessfully committed.
-	if l.cfg.DebugHTLC && l.cfg.HodlMask.Active(hodl.Commit) {
+	if l.cfg.HodlMask.Active(hodl.Commit) {
 		l.warnf(hodl.Commit.Warning())
 		return nil
 	}
@@ -2445,7 +2439,7 @@ func (l *channelLink) processRemoteSettleFails(fwdPkg *channeldb.FwdPkg,
 			// If hodl.SettleIncoming is requested, we will not
 			// forward the SETTLE to the switch and will not signal
 			// a free slot on the commitment transaction.
-			if l.cfg.DebugHTLC && l.cfg.HodlMask.Active(hodl.SettleIncoming) {
+			if l.cfg.HodlMask.Active(hodl.SettleIncoming) {
 				l.warnf(hodl.SettleIncoming.Warning())
 				continue
 			}
@@ -2473,7 +2467,7 @@ func (l *channelLink) processRemoteSettleFails(fwdPkg *channeldb.FwdPkg,
 			// If hodl.SettleIncoming is requested, we will not
 			// forward the FAIL to the switch and will not signal a
 			// free slot on the commitment transaction.
-			if l.cfg.DebugHTLC && l.cfg.HodlMask.Active(hodl.FailIncoming) {
+			if l.cfg.HodlMask.Active(hodl.FailIncoming) {
 				l.warnf(hodl.FailIncoming.Warning())
 				continue
 			}
@@ -2654,8 +2648,7 @@ func (l *channelLink) processRemoteAdds(fwdPkg *channeldb.FwdPkg,
 			// If hodl.AddIncoming is requested, we will not
 			// validate the forwarded ADD, nor will we send the
 			// packet to the htlc switch.
-			if l.cfg.DebugHTLC &&
-				l.cfg.HodlMask.Active(hodl.AddIncoming) {
+			if l.cfg.HodlMask.Active(hodl.AddIncoming) {
 				l.warnf(hodl.AddIncoming.Warning())
 				continue
 			}
@@ -2814,7 +2807,7 @@ func (l *channelLink) processExitHop(pd *lnwallet.PaymentDescriptor,
 	// If hodl.ExitSettle is requested, we will not validate the final hop's
 	// ADD, nor will we settle the corresponding invoice or respond with the
 	// preimage.
-	if l.cfg.DebugHTLC && l.cfg.HodlMask.Active(hodl.ExitSettle) {
+	if l.cfg.HodlMask.Active(hodl.ExitSettle) {
 		l.warnf(hodl.ExitSettle.Warning())
 
 		return false, nil
@@ -2823,7 +2816,7 @@ func (l *channelLink) processExitHop(pd *lnwallet.PaymentDescriptor,
 	// As we're the exit hop, we'll double check the hop-payload included in
 	// the HTLC to ensure that it was crafted correctly by the sender and
 	// matches the HTLC we were extended.
-	if !l.cfg.DebugHTLC && pd.Amount != fwdInfo.AmountToForward {
+	if pd.Amount != fwdInfo.AmountToForward {
 
 		log.Errorf("Onion payload of incoming htlc(%x) has incorrect "+
 			"value: expected %v, got %v", pd.RHash,
@@ -2837,7 +2830,7 @@ func (l *channelLink) processExitHop(pd *lnwallet.PaymentDescriptor,
 
 	// We'll also ensure that our time-lock value has been computed
 	// correctly.
-	if !l.cfg.DebugHTLC && pd.Timeout != fwdInfo.OutgoingCTLV {
+	if pd.Timeout != fwdInfo.OutgoingCTLV {
 		log.Errorf("Onion payload of incoming htlc(%x) has incorrect "+
 			"time-lock: expected %v, got %v",
 			pd.RHash[:], pd.Timeout, fwdInfo.OutgoingCTLV)
@@ -2914,7 +2907,7 @@ func (l *channelLink) settleHTLC(preimage lntypes.Preimage, htlcIndex uint64,
 
 	// If the link is in hodl.BogusSettle mode, replace the preimage with a
 	// fake one before sending it to the peer.
-	if l.cfg.DebugHTLC && l.cfg.HodlMask.Active(hodl.BogusSettle) {
+	if l.cfg.HodlMask.Active(hodl.BogusSettle) {
 		l.warnf(hodl.BogusSettle.Warning())
 		preimage = [32]byte{}
 		copy(preimage[:], bytes.Repeat([]byte{2}, 32))

htlcswitch/link_test.go

@@ -1908,7 +1908,6 @@ func TestChannelLinkBandwidthConsistency(t *testing.T) {
 	// We put Alice into hodl.ExitSettle mode, such that she won't settle
 	// incoming HTLCs automatically.
 	coreLink.cfg.HodlMask = hodl.MaskFromFlags(hodl.ExitSettle)
-	coreLink.cfg.DebugHTLC = true
 
 	estimator := lnwallet.NewStaticFeeEstimator(6000, 0)
 	feePerKw, err := estimator.EstimateFeePerKW(1)
@@ -2857,7 +2856,6 @@ func TestChannelLinkTrimCircuitsNoCommit(t *testing.T) {
 	// outgoing ADDs are opened, but the changes are not committed in the
 	// channel state.
 	alice.coreLink.cfg.HodlMask = hodl.Commit.Mask()
-	alice.coreLink.cfg.DebugHTLC = true
 
 	// Compute the static fees that will be used to determine the
 	// correctness of Alice's bandwidth when forwarding HTLCs.
@@ -4233,7 +4231,6 @@ func (h *persistentLinkHarness) restartLink(
 		MaxFeeUpdateTimeout: 40 * time.Minute,
 		// Set any hodl flags requested for the new link.
 		HodlMask:              hodl.MaskFromFlags(hodlFlags...),
-		DebugHTLC:             len(hodlFlags) > 0,
 		MaxOutgoingCltvExpiry: DefaultMaxOutgoingCltvExpiry,
 	}
 
@@ -4934,7 +4931,6 @@ func TestChannelLinkCleanupSpuriousResponses(t *testing.T) {
 	// Settle Alice in hodl ExitSettle mode so that she won't respond
 	// immediately to the htlc's meant for her. This allows us to control
 	// the responses she gives back to Bob.
-	coreLink.cfg.DebugHTLC = true
 	coreLink.cfg.HodlMask = hodl.ExitSettle.Mask()
 
 	// Add two HTLCs to Alice's registry, that Bob can pay.