multi: resend shutdown on reestablish

channeldb/channel.go

@@ -20,6 +20,7 @@ import (
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcwallet/walletdb"
 	"github.com/lightningnetwork/lnd/channeldb/models"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/keychain"
@@ -121,6 +122,12 @@ var (
 	// broadcasted when moving the channel to state CoopBroadcasted.
 	coopCloseTxKey = []byte("coop-closing-tx-key")
 
+	// shutdownInfoKey points to the serialised shutdown info that has been
+	// persisted for a channel. The existence of this info means that we
+	// have sent the Shutdown message before and so should re-initiate the
+	// shutdown on re-establish.
+	shutdownInfoKey = []byte("shutdown-info-key")
+
 	// commitDiffKey stores the current pending commitment state we've
 	// extended to the remote party (if any). Each time we propose a new
 	// state, we store the information necessary to reconstruct this state
@@ -188,6 +195,10 @@ var (
 	// in the state CommitBroadcasted.
 	ErrNoCloseTx = fmt.Errorf("no closing tx found")
 
+	// ErrNoShutdownInfo is returned when no shutdown info has been
+	// persisted for a channel.
+	ErrNoShutdownInfo = errors.New("no shutdown info")
+
 	// ErrNoRestoredChannelMutation is returned when a caller attempts to
 	// mutate a channel that's been recovered.
 	ErrNoRestoredChannelMutation = fmt.Errorf("cannot mutate restored " +
@@ -1575,6 +1586,79 @@ func (c *OpenChannel) ChanSyncMsg() (*lnwire.ChannelReestablish, error) {
 	}, nil
 }
 
+// MarkShutdownSent serialises and persist the given ShutdownInfo for this
+// channel. Persisting this info represents the fact that we have sent the
+// Shutdown message to the remote side and hence that we should re-transmit the
+// same Shutdown message on re-establish.
+func (c *OpenChannel) MarkShutdownSent(info *ShutdownInfo) error {
+	c.Lock()
+	defer c.Unlock()
+
+	return c.storeShutdownInfo(info)
+}
+
+// storeShutdownInfo serialises the ShutdownInfo and persists it under the
+// shutdownInfoKey.
+func (c *OpenChannel) storeShutdownInfo(info *ShutdownInfo) error {
+	var b bytes.Buffer
+	err := info.encode(&b)
+	if err != nil {
+		return err
+	}
+
+	return kvdb.Update(c.Db.backend, func(tx kvdb.RwTx) error {
+		chanBucket, err := fetchChanBucketRw(
+			tx, c.IdentityPub, &c.FundingOutpoint, c.ChainHash,
+		)
+		if err != nil {
+			return err
+		}
+
+		return chanBucket.Put(shutdownInfoKey, b.Bytes())
+	}, func() {})
+}
+
+// ShutdownInfo decodes the shutdown info stored for this channel and returns
+// the result. If no shutdown info has been persisted for this channel then the
+// ErrNoShutdownInfo error is returned.
+func (c *OpenChannel) ShutdownInfo() (fn.Option[ShutdownInfo], error) {
+	c.RLock()
+	defer c.RUnlock()
+
+	var shutdownInfo *ShutdownInfo
+	err := kvdb.View(c.Db.backend, func(tx kvdb.RTx) error {
+		chanBucket, err := fetchChanBucket(
+			tx, c.IdentityPub, &c.FundingOutpoint, c.ChainHash,
+		)
+		switch {
+		case err == nil:
+		case errors.Is(err, ErrNoChanDBExists),
+			errors.Is(err, ErrNoActiveChannels),
+			errors.Is(err, ErrChannelNotFound):
+
+			return ErrNoShutdownInfo
+		default:
+			return err
+		}
+
+		shutdownInfoBytes := chanBucket.Get(shutdownInfoKey)
+		if shutdownInfoBytes == nil {
+			return ErrNoShutdownInfo
+		}
+
+		shutdownInfo, err = decodeShutdownInfo(shutdownInfoBytes)
+
+		return err
+	}, func() {
+		shutdownInfo = nil
+	})
+	if err != nil {
+		return fn.None[ShutdownInfo](), err
+	}
+
+	return fn.Some[ShutdownInfo](*shutdownInfo), nil
+}
+
 // isBorked returns true if the channel has been marked as borked in the
 // database. This requires an existing database transaction to already be
 // active.
@@ -4294,3 +4378,59 @@ func MakeScidRecord(typ tlv.Type, scid *lnwire.ShortChannelID) tlv.Record {
 		typ, scid, 8, lnwire.EShortChannelID, lnwire.DShortChannelID,
 	)
 }
+
+// ShutdownInfo contains various info about the shutdown initiation of a
+// channel.
+type ShutdownInfo struct {
+	// DeliveryScript is the address that we have included in any previous
+	// Shutdown message for a particular channel and so should include in
+	// any future re-sends of the Shutdown message.
+	DeliveryScript tlv.RecordT[tlv.TlvType0, lnwire.DeliveryAddress]
+
+	// LocalInitiator is true if we sent a Shutdown message before ever
+	// receiving a Shutdown message from the remote peer.
+	LocalInitiator tlv.RecordT[tlv.TlvType1, bool]
+}
+
+// NewShutdownInfo constructs a new ShutdownInfo object.
+func NewShutdownInfo(deliveryScript lnwire.DeliveryAddress,
+	locallyInitiated bool) *ShutdownInfo {
+
+	return &ShutdownInfo{
+		DeliveryScript: tlv.NewRecordT[tlv.TlvType0](deliveryScript),
+		LocalInitiator: tlv.NewPrimitiveRecord[tlv.TlvType1](
+			locallyInitiated,
+		),
+	}
+}
+
+// encode serialises the ShutdownInfo to the given io.Writer.
+func (s *ShutdownInfo) encode(w io.Writer) error {
+	records := []tlv.Record{
+		s.DeliveryScript.Record(),
+		s.LocalInitiator.Record(),
+	}
+
+	stream, err := tlv.NewStream(records...)
+	if err != nil {
+		return err
+	}
+
+	return stream.Encode(w)
+}
+
+// decodeShutdownInfo constructs a ShutdownInfo struct by decoding the given
+// byte slice.
+func decodeShutdownInfo(b []byte) (*ShutdownInfo, error) {
+	tlvStream := lnwire.ExtraOpaqueData(b)
+
+	var info ShutdownInfo
+	records := []tlv.RecordProducer{
+		&info.DeliveryScript,
+		&info.LocalInitiator,
+	}
+
+	_, err := tlvStream.ExtractRecords(records...)
+
+	return &info, err
+}

channeldb/channel_test.go

@@ -1158,6 +1158,70 @@ func TestFetchWaitingCloseChannels(t *testing.T) {
 	}
 }
 
+// TestShutdownInfo tests that a channel's shutdown info can correctly be
+// persisted and retrieved.
+func TestShutdownInfo(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name      string
+		localInit bool
+	}{
+		{
+			name:      "local node initiated",
+			localInit: true,
+		},
+		{
+			name:      "remote node initiated",
+			localInit: false,
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+
+			testShutdownInfo(t, test.localInit)
+		})
+	}
+}
+
+func testShutdownInfo(t *testing.T, locallyInitiated bool) {
+	fullDB, err := MakeTestDB(t)
+	require.NoError(t, err, "unable to make test database")
+
+	cdb := fullDB.ChannelStateDB()
+
+	// First a test channel.
+	channel := createTestChannel(t, cdb)
+
+	// We haven't persisted any shutdown info for this channel yet.
+	_, err = channel.ShutdownInfo()
+	require.Error(t, err, ErrNoShutdownInfo)
+
+	// Construct a new delivery script and create a new ShutdownInfo object.
+	script := []byte{1, 3, 4, 5}
+
+	// Create a ShutdownInfo struct.
+	shutdownInfo := NewShutdownInfo(script, locallyInitiated)
+
+	// Persist the shutdown info.
+	require.NoError(t, channel.MarkShutdownSent(shutdownInfo))
+
+	// We should now be able to retrieve the shutdown info.
+	info, err := channel.ShutdownInfo()
+	require.NoError(t, err)
+	require.True(t, info.IsSome())
+
+	// Assert that the decoded values of the shutdown info are correct.
+	info.WhenSome(func(info ShutdownInfo) {
+		require.EqualValues(t, script, info.DeliveryScript.Val)
+		require.Equal(t, locallyInitiated, info.LocalInitiator.Val)
+	})
+}
+
 // TestRefresh asserts that Refresh updates the in-memory state of another
 // OpenChannel to reflect a preceding call to MarkOpen on a different
 // OpenChannel.

docs/release-notes/release-notes-0.18.0.md

@@ -73,6 +73,11 @@
   a `shutdown` message if there were currently HTLCs on the channel. After this
   change, the shutdown procedure should be compliant with BOLT2 requirements.
 
+* If HTLCs are in-flight at the same time that a `shutdown` is sent and then 
+  a re-connect happens before the coop-close is completed we now [ensure that 
+  we re-init the `shutdown` 
+  exchange](https://github.com/lightningnetwork/lnd/pull/8464)
+
 * The AMP struct in payment hops will [now be populated](https://github.com/lightningnetwork/lnd/pull/7976) when the AMP TLV is set.
 
 * [Add Taproot witness types

htlcswitch/interfaces.go

@@ -135,14 +135,16 @@ type ChannelUpdateHandler interface {
 	MayAddOutgoingHtlc(lnwire.MilliSatoshi) error
 
 	// EnableAdds sets the ChannelUpdateHandler state to allow
-	// UpdateAddHtlc's in the specified direction. It returns an error if
-	// the state already allowed those adds.
-	EnableAdds(direction LinkDirection) error
-
-	// DiableAdds sets the ChannelUpdateHandler state to allow
-	// UpdateAddHtlc's in the specified direction. It returns an error if
-	// the state already disallowed those adds.
-	DisableAdds(direction LinkDirection) error
+	// UpdateAddHtlc's in the specified direction. It returns true if the
+	// state was changed and false if the desired state was already set
+	// before the method was called.
+	EnableAdds(direction LinkDirection) bool
+
+	// DisableAdds sets the ChannelUpdateHandler state to allow
+	// UpdateAddHtlc's in the specified direction. It returns true if the
+	// state was changed and false if the desired state was already set
+	// before the method was called.
+	DisableAdds(direction LinkDirection) bool
 
 	// IsFlushing returns true when UpdateAddHtlc's are disabled in the
 	// direction of the argument.

htlcswitch/link.go

@@ -19,6 +19,7 @@ import (
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/channeldb/models"
 	"github.com/lightningnetwork/lnd/contractcourt"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/htlcswitch/hodl"
 	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/invoices"
@@ -271,6 +272,14 @@ type ChannelLinkConfig struct {
 	// GetAliases is used by the link and switch to fetch the set of
 	// aliases for a given link.
 	GetAliases func(base lnwire.ShortChannelID) []lnwire.ShortChannelID
+
+	// PreviouslySentShutdown is an optional value that is set if, at the
+	// time of the link being started, persisted shutdown info was found for
+	// the channel. This value being set means that we previously sent a
+	// Shutdown message to our peer, and so we should do so again on
+	// re-establish and should not allow anymore HTLC adds on the outgoing
+	// direction of the link.
+	PreviouslySentShutdown fn.Option[lnwire.Shutdown]
 }
 
 // channelLink is the service which drives a channel's commitment update
@@ -618,41 +627,25 @@ func (l *channelLink) EligibleToUpdate() bool {
 }
 
 // EnableAdds sets the ChannelUpdateHandler state to allow UpdateAddHtlc's in
-// the specified direction. It returns an error if the state already allowed
-// those adds.
-func (l *channelLink) EnableAdds(linkDirection LinkDirection) error {
+// the specified direction. It returns true if the state was changed and false
+// if the desired state was already set before the method was called.
+func (l *channelLink) EnableAdds(linkDirection LinkDirection) bool {
 	if linkDirection == Outgoing {
-		if !l.isOutgoingAddBlocked.Swap(false) {
-			return errors.New("outgoing adds already enabled")
-		}
-	}
-
-	if linkDirection == Incoming {
-		if !l.isIncomingAddBlocked.Swap(false) {
-			return errors.New("incoming adds already enabled")
-		}
+		return l.isOutgoingAddBlocked.Swap(false)
 	}
 
-	return nil
+	return l.isIncomingAddBlocked.Swap(false)
 }
 
-// DiableAdds sets the ChannelUpdateHandler state to allow UpdateAddHtlc's in
-// the specified direction. It returns an error if the state already disallowed
-// those adds.
-func (l *channelLink) DisableAdds(linkDirection LinkDirection) error {
+// DisableAdds sets the ChannelUpdateHandler state to allow UpdateAddHtlc's in
+// the specified direction. It returns true if the state was changed and false
+// if the desired state was already set before the method was called.
+func (l *channelLink) DisableAdds(linkDirection LinkDirection) bool {
 	if linkDirection == Outgoing {
-		if l.isOutgoingAddBlocked.Swap(true) {
-			return errors.New("outgoing adds already disabled")
-		}
+		return !l.isOutgoingAddBlocked.Swap(true)
 	}
 
-	if linkDirection == Incoming {
-		if l.isIncomingAddBlocked.Swap(true) {
-			return errors.New("incoming adds already disabled")
-		}
-	}
-
-	return nil
+	return !l.isIncomingAddBlocked.Swap(true)
 }
 
 // IsFlushing returns true when UpdateAddHtlc's are disabled in the direction of
@@ -1206,6 +1199,25 @@ func (l *channelLink) htlcManager() {
 		}
 	}
 
+	// If a shutdown message has previously been sent on this link, then we
+	// need to make sure that we have disabled any HTLC adds on the outgoing
+	// direction of the link and that we re-resend the same shutdown message
+	// that we previously sent.
+	l.cfg.PreviouslySentShutdown.WhenSome(func(shutdown lnwire.Shutdown) {
+		// Immediately disallow any new outgoing HTLCs.
+		if !l.DisableAdds(Outgoing) {
+			l.log.Warnf("Outgoing link adds already disabled")
+		}
+
+		// Re-send the shutdown message the peer. Since syncChanStates
+		// would have sent any outstanding CommitSig, it is fine for us
+		// to immediately queue the shutdown message now.
+		err := l.cfg.Peer.SendMessage(false, &shutdown)
+		if err != nil {
+			l.log.Warnf("Error sending shutdown message: %v", err)
+		}
+	})
+
 	// We've successfully reestablished the channel, mark it as such to
 	// allow the switch to forward HTLCs in the outbound direction.
 	l.markReestablished()