return unencrypted failure messages with channel update

Author: joostjager

go.mod

@@ -103,7 +103,7 @@ require (
 	github.com/lightningnetwork/lnd/kvdb v1.3.1 // indirect
 	github.com/lightningnetwork/lnd/ticker v1.1.0 // indirect
 	github.com/lightningnetwork/lnd/tlv v1.0.3 // indirect
-	github.com/lightningnetwork/lnd/tor v1.0.1 // indirect
+	github.com/lightningnetwork/lnd/tor v1.1.0 // indirect
 	github.com/ltcsuite/ltcd v0.20.1-beta // indirect
 	github.com/mailru/easyjson v0.7.6 // indirect
 	github.com/matttproud/golang_protobuf_extensions v1.0.1 // indirect
@@ -182,3 +182,5 @@ require (
 )
 
 replace github.com/bottlepay/lnmux/lnmuxrpc => ./lnmuxrpc
+
+replace github.com/lightningnetwork/lnd => /users/Joost.Jager/lightninglabs/lnd

go.sum

@@ -507,8 +507,6 @@ github.com/lightninglabs/neutrino v0.14.2 h1:yrnZUCYMZ5ECtXhgDrzqPq2oX8awoAN2D/c
 github.com/lightninglabs/neutrino v0.14.2/go.mod h1:OICUeTCn+4Tu27YRJIpWvvqySxx4oH4vgdP33Sw9RDc=
 github.com/lightningnetwork/lightning-onion v1.0.2-0.20220211021909-bb84a1ccb0c5 h1:TkKwqFcQTGYoI+VEqyxA8rxpCin8qDaYX0AfVRinT3k=
 github.com/lightningnetwork/lightning-onion v1.0.2-0.20220211021909-bb84a1ccb0c5/go.mod h1:7dDx73ApjEZA0kcknI799m2O5kkpfg4/gr7N092ojNo=
-github.com/lightningnetwork/lnd v0.15.4-beta h1:vO+UZjuA8RqJdDlfwQeS0h2PCocYwwqv5HkX2IXf5/M=
-github.com/lightningnetwork/lnd v0.15.4-beta/go.mod h1:6aoOkifcI9tuk8UV5l2rVZSq0681obuP4zvfK+2ZrT0=
 github.com/lightningnetwork/lnd/clock v1.0.1/go.mod h1:KnQudQ6w0IAMZi1SgvecLZQZ43ra2vpDNj7H/aasemg=
 github.com/lightningnetwork/lnd/clock v1.1.0 h1:/yfVAwtPmdx45aQBoXQImeY7sOIEr7IXlImRMBOZ7GQ=
 github.com/lightningnetwork/lnd/clock v1.1.0/go.mod h1:KnQudQ6w0IAMZi1SgvecLZQZ43ra2vpDNj7H/aasemg=
@@ -527,8 +525,8 @@ github.com/lightningnetwork/lnd/tlv v1.0.2/go.mod h1:fICAfsqk1IOsC1J7G9IdsWX1EqW
 github.com/lightningnetwork/lnd/tlv v1.0.3 h1:0xBZcPuXagP6f7TY/RnLNR4igE21ov6qUdTr5NyvhhI=
 github.com/lightningnetwork/lnd/tlv v1.0.3/go.mod h1:dzR/aZetBri+ZY/fHbwV06fNn/3UID6htQzbHfREFdo=
 github.com/lightningnetwork/lnd/tor v1.0.0/go.mod h1:RDtaAdwfAm+ONuPYwUhNIH1RAvKPv+75lHPOegUcz64=
-github.com/lightningnetwork/lnd/tor v1.0.1 h1:A11FrpU0Y//g+fA827W4VnjOeoIvExONdchlLX8wYkA=
-github.com/lightningnetwork/lnd/tor v1.0.1/go.mod h1:RDtaAdwfAm+ONuPYwUhNIH1RAvKPv+75lHPOegUcz64=
+github.com/lightningnetwork/lnd/tor v1.1.0 h1:iXO7fSzjxTI+p88KmtpbuyuRJeNfgtpl9QeaAliILXE=
+github.com/lightningnetwork/lnd/tor v1.1.0/go.mod h1:RDtaAdwfAm+ONuPYwUhNIH1RAvKPv+75lHPOegUcz64=
 github.com/ltcsuite/ltcd v0.20.1-beta h1:ka9ZwUG7oUPppl+7ptuh5VDxGD7TWEJXu/IOOOz1yfY=
 github.com/ltcsuite/ltcd v0.20.1-beta/go.mod h1:ZFQaYdYULIuTQiWqs7AUiHD2XhDFeeHW1IH+UYMdABU=
 github.com/ltcsuite/ltcutil v0.0.0-20191227053721-6bec450ea6ad/go.mod h1:8Vg/LTOO0KYa/vlHWJ6XZAevPQThGH5sufO0Hrou/lA=

interceptor.go

@@ -156,10 +156,11 @@ func (i *interceptor) start(ctx context.Context) error {
 					ChanId: item.incomingKey.ChanID,
 					HtlcId: item.incomingKey.HtlcID,
 				},
-				Action:         item.resp.action,
-				Preimage:       item.resp.preimage[:],
-				FailureMessage: item.resp.failureMessage,
-				FailureCode:    item.resp.failureCode,
+				Action:                    item.resp.action,
+				Preimage:                  item.resp.preimage[:],
+				FailureMessage:            item.resp.failureMessage,
+				FailureCode:               item.resp.failureCode,
+				FailureMessageUnencrypted: item.resp.failureMessageUnencrypted,
 			}
 
 			if err := send(rpcResp); err != nil {

mux.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"fmt"
 	"sync"
+	"time"
 
 	"github.com/bottlepay/lnmux/lnd"
 	"github.com/bottlepay/lnmux/types"
@@ -105,10 +106,11 @@ type interceptedHtlc struct {
 }
 
 type interceptedHtlcResponse struct {
-	action         routerrpc.ResolveHoldForwardAction
-	preimage       lntypes.Preimage
-	failureMessage []byte
-	failureCode    lnrpc.Failure_FailureCode
+	action                    routerrpc.ResolveHoldForwardAction
+	preimage                  lntypes.Preimage
+	failureMessage            []byte
+	failureCode               lnrpc.Failure_FailureCode
+	failureMessageUnencrypted bool
 }
 
 func (p *Mux) Run(mainCtx context.Context) error {
@@ -221,6 +223,31 @@ func (p *Mux) ProcessHtlc(
 	fail := func(code lnwire.FailCode) error {
 		logger.Debugw("Failing htlc", "code", code)
 
+		if code == lnwire.CodeFeeInsufficient {
+			wireMsg := lnwire.NewFeeInsufficient(0, lnwire.ChannelUpdate{
+				ChainHash:      *p.lnd.Network().GenesisHash,
+				ShortChannelID: lnwire.NewShortChanIDFromInt(p.virtualChannel),
+				Timestamp:      uint32(time.Now().Unix()),
+				// TODO: Set direction!
+				// MessageFlags: ,
+				// ChannelFlags: ,
+				TimeLockDelta: uint16(p.routingPolicy.CltvDelta),
+				BaseFee:       uint32(p.routingPolicy.FeeBaseMsat),
+				FeeRate:       uint32(p.routingPolicy.FeeRatePpm),
+			})
+			var w bytes.Buffer
+			err := lnwire.EncodeFailureMessage(&w, wireMsg, 0)
+			if err != nil {
+				return err
+			}
+
+			return htlc.reply(&interceptedHtlcResponse{
+				action:                    routerrpc.ResolveHoldForwardAction_FAIL,
+				failureMessage:            w.Bytes(),
+				failureMessageUnencrypted: true,
+			})
+		}
+
 		rpcCode, err := marshallFailureCode(code)
 		if err != nil {
 			return err