multi: fix loopvar and enhance logging around channel reestablishment

channeldb/channel.go

@@ -849,6 +849,30 @@ type OpenChannel struct {
 	sync.RWMutex
 }
 
+// String returns a string representation of the channel.
+func (c *OpenChannel) String() string {
+	indexStr := "height=%v, local_htlc_index=%v, local_log_index=%v, " +
+		"remote_htlc_index=%v, remote_log_index=%v"
+
+	commit := c.LocalCommitment
+	local := fmt.Sprintf(indexStr, commit.CommitHeight,
+		commit.LocalHtlcIndex, commit.LocalLogIndex,
+		commit.RemoteHtlcIndex, commit.RemoteLogIndex,
+	)
+
+	commit = c.RemoteCommitment
+	remote := fmt.Sprintf(indexStr, commit.CommitHeight,
+		commit.LocalHtlcIndex, commit.LocalLogIndex,
+		commit.RemoteHtlcIndex, commit.RemoteLogIndex,
+	)
+
+	return fmt.Sprintf("SCID=%v, status=%v, initiator=%v, pending=%v, "+
+		"local commitment has %s, remote commitment has %s",
+		c.ShortChannelID, c.chanStatus, c.IsInitiator, c.IsPending,
+		local, remote,
+	)
+}
+
 // ShortChanID returns the current ShortChannelID of this channel.
 func (c *OpenChannel) ShortChanID() lnwire.ShortChannelID {
 	c.RLock()
@@ -2100,6 +2124,10 @@ func (c *OpenChannel) ActiveHtlcs() []HTLC {
 	// which ones are present on their commitment.
 	remoteHtlcs := make(map[[32]byte]struct{})
 	for _, htlc := range c.RemoteCommitment.Htlcs {
+		log.Tracef("RemoteCommitment has htlc: id=%v, update=%v "+
+			"incoming=%v", htlc.HtlcIndex, htlc.LogIndex,
+			htlc.Incoming)
+
 		onionHash := sha256.Sum256(htlc.OnionBlob[:])
 		remoteHtlcs[onionHash] = struct{}{}
 	}
@@ -2108,8 +2136,16 @@ func (c *OpenChannel) ActiveHtlcs() []HTLC {
 	// as active if *we* know them as well.
 	activeHtlcs := make([]HTLC, 0, len(remoteHtlcs))
 	for _, htlc := range c.LocalCommitment.Htlcs {
+		log.Tracef("LocalCommitment has htlc: id=%v, update=%v "+
+			"incoming=%v", htlc.HtlcIndex, htlc.LogIndex,
+			htlc.Incoming)
+
 		onionHash := sha256.Sum256(htlc.OnionBlob[:])
 		if _, ok := remoteHtlcs[onionHash]; !ok {
+			log.Tracef("Skipped htlc due to onion mismatched: "+
+				"id=%v, update=%v incoming=%v",
+				htlc.HtlcIndex, htlc.LogIndex, htlc.Incoming)
+
 			continue
 		}
 

docs/release-notes/release-notes-0.17.3.md

@@ -23,6 +23,9 @@
   `musig2Sessions` with a `SyncMap` used in `input` package to avoid concurrent
   write to this map.
 
+* [Fixed](https://github.com/lightningnetwork/lnd/pull/8220) a loop variable
+  issue which may affect programs built using go `v1.20` and below. 
+
 # New Features
 ## Functional Enhancements
 ## RPC Additions

htlcswitch/link.go

@@ -649,12 +649,13 @@ func (l *channelLink) createFailureWithUpdate(incoming bool,
 // flow. We'll compare out commitment chains with the remote party, and re-send
 // either a danging commit signature, a revocation, or both.
 func (l *channelLink) syncChanStates() error {
-	l.log.Info("attempting to re-synchronize")
+	chanState := l.channel.State()
+
+	l.log.Infof("Attempting to re-synchronize channel: %v", chanState)
 
 	// First, we'll generate our ChanSync message to send to the other
 	// side. Based on this message, the remote party will decide if they
 	// need to retransmit any data or not.
-	chanState := l.channel.State()
 	localChanSyncMsg, err := chanState.ChanSyncMsg()
 	if err != nil {
 		return fmt.Errorf("unable to generate chan sync message for "+

lnwallet/channel.go

@@ -904,6 +904,8 @@ func (lc *LightningChannel) extractPayDescs(commitHeight uint64,
 		// persist state w.r.t to if forwarded or not, or can
 		// inadvertently trigger replays
 
+		htlc := htlc
+
 		payDesc, err := lc.diskHtlcToPayDesc(
 			feeRate, commitHeight, &htlc,
 			localCommitKeys, remoteCommitKeys,

lnwallet/channel_test.go

@@ -10111,3 +10111,101 @@ func testNewBreachRetribution(t *testing.T, chanType channeldb.ChannelType) {
 	)
 	require.ErrorIs(t, err, channeldb.ErrLogEntryNotFound)
 }
+
+// TestExtractPayDescs asserts that `extractPayDescs` can correctly turn a
+// slice of htlcs into two slices of PaymentDescriptors.
+func TestExtractPayDescs(t *testing.T) {
+	t.Parallel()
+
+	// Create a testing LightningChannel.
+	lnChan, _, err := CreateTestChannels(
+		t, channeldb.SingleFunderTweaklessBit,
+	)
+	require.NoError(t, err)
+
+	// Create two incoming HTLCs.
+	incomings := []channeldb.HTLC{
+		createRandomHTLC(t, true),
+		createRandomHTLC(t, true),
+	}
+
+	// Create two outgoing HTLCs.
+	outgoings := []channeldb.HTLC{
+		createRandomHTLC(t, false),
+		createRandomHTLC(t, false),
+	}
+
+	// Concatenate incomings and outgoings into a single slice.
+	htlcs := []channeldb.HTLC{}
+	htlcs = append(htlcs, incomings...)
+	htlcs = append(htlcs, outgoings...)
+
+	// Run the method under test.
+	//
+	// NOTE: we use nil commitment key rings to avoid checking the htlc
+	// scripts(`genHtlcScript`) as it should be tested independently.
+	incomingPDs, outgoingPDs, err := lnChan.extractPayDescs(
+		0, 0, htlcs, nil, nil, true,
+	)
+	require.NoError(t, err)
+
+	// Assert the incoming PaymentDescriptors are matched.
+	for i, pd := range incomingPDs {
+		htlc := incomings[i]
+		assertPayDescMatchHTLC(t, pd, htlc)
+	}
+
+	// Assert the outgoing PaymentDescriptors are matched.
+	for i, pd := range outgoingPDs {
+		htlc := outgoings[i]
+		assertPayDescMatchHTLC(t, pd, htlc)
+	}
+}
+
+// assertPayDescMatchHTLC compares a PaymentDescriptor to a channeldb.HTLC and
+// asserts that the fields are matched.
+func assertPayDescMatchHTLC(t *testing.T, pd PaymentDescriptor,
+	htlc channeldb.HTLC) {
+
+	require := require.New(t)
+
+	require.EqualValues(htlc.RHash, pd.RHash, "RHash")
+	require.Equal(htlc.RefundTimeout, pd.Timeout, "Timeout")
+	require.Equal(htlc.Amt, pd.Amount, "Amount")
+	require.Equal(htlc.HtlcIndex, pd.HtlcIndex, "HtlcIndex")
+	require.Equal(htlc.LogIndex, pd.LogIndex, "LogIndex")
+	require.EqualValues(htlc.OnionBlob[:], pd.OnionBlob, "OnionBlob")
+}
+
+// createRandomHTLC creates an HTLC that has random value in every field except
+// the `Incoming`.
+func createRandomHTLC(t *testing.T, incoming bool) channeldb.HTLC {
+	var onionBlob [lnwire.OnionPacketSize]byte
+	_, err := rand.Read(onionBlob[:])
+	require.NoError(t, err)
+
+	var rHash [lntypes.HashSize]byte
+	_, err = rand.Read(rHash[:])
+	require.NoError(t, err)
+
+	sig := make([]byte, 64)
+	_, err = rand.Read(sig)
+	require.NoError(t, err)
+
+	extra := make([]byte, 1000)
+	_, err = rand.Read(extra)
+	require.NoError(t, err)
+
+	return channeldb.HTLC{
+		Signature:     sig,
+		RHash:         rHash,
+		Amt:           lnwire.MilliSatoshi(rand.Uint64()),
+		RefundTimeout: rand.Uint32(),
+		OutputIndex:   rand.Int31n(1000),
+		Incoming:      incoming,
+		OnionBlob:     onionBlob,
+		HtlcIndex:     rand.Uint64(),
+		LogIndex:      rand.Uint64(),
+		ExtraData:     extra,
+	}
+}

peer/brontide.go

@@ -2009,7 +2009,8 @@ func messageSummary(msg lnwire.Message) string {
 			msg.ChanID, int64(msg.FeePerKw))
 
 	case *lnwire.ChannelReestablish:
-		return fmt.Sprintf("next_local_height=%v, remote_tail_height=%v",
+		return fmt.Sprintf("chan_id=%v, next_local_height=%v, "+
+			"remote_tail_height=%v", msg.ChanID,
 			msg.NextLocalCommitHeight, msg.RemoteCommitTailHeight)
 
 	case *lnwire.ReplyShortChanIDsEnd: