multi: build retribution info in TowerClient

Since the TowerClient now has a callback that it can use to retrieve the
retribution for a certain channel and commit height, let it use this
call back instead of requiring the info to be passed to it through
BackupState.

htlcswitch/interfaces.go

@@ -7,7 +7,6 @@ import (
 	"github.com/lightningnetwork/lnd/invoices"
 	"github.com/lightningnetwork/lnd/lnpeer"
 	"github.com/lightningnetwork/lnd/lntypes"
-	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/record"
@@ -255,11 +254,8 @@ type TowerClient interface {
 	// state. If the method returns nil, the backup is guaranteed to be
 	// successful unless the tower is unavailable and client is force quit,
 	// or the justice transaction would create dust outputs when trying to
-	// abide by the negotiated policy. If the channel we're trying to back
-	// up doesn't have a tweak for the remote party's output, then
-	// isTweakless should be true.
-	BackupState(*lnwire.ChannelID, *lnwallet.BreachRetribution,
-		channeldb.ChannelType) error
+	// abide by the negotiated policy.
+	BackupState(chanID *lnwire.ChannelID, stateNum uint64) error
 }
 
 // InterceptableHtlcForwarder is the interface to set the interceptor

htlcswitch/link.go

@@ -2022,11 +2022,6 @@ func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
 		// We've received a revocation from the remote chain, if valid,
 		// this moves the remote chain forward, and expands our
 		// revocation window.
-		//
-		// Before advancing our remote chain, we will record the
-		// current commit tx, which is used by the TowerClient to
-		// create backups.
-		oldCommitTx := l.channel.State().RemoteCommitment.CommitTx
 
 		// We now process the message and advance our remote commit
 		// chain.
@@ -2063,24 +2058,15 @@ func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
 		// create a backup for the current state.
 		if l.cfg.TowerClient != nil {
 			state := l.channel.State()
-			breachInfo, err := lnwallet.NewBreachRetribution(
-				state, state.RemoteCommitment.CommitHeight-1, 0,
-				// OldCommitTx is the breaching tx at height-1.
-				oldCommitTx,
-			)
-			if err != nil {
-				l.fail(LinkFailureError{code: ErrInternalError},
-					"failed to load breach info: %v", err)
-				return
-			}
-
 			chanID := l.ChanID()
+
 			err = l.cfg.TowerClient.BackupState(
-				&chanID, breachInfo, state.ChanType,
+				&chanID, state.RemoteCommitment.CommitHeight-1,
 			)
 			if err != nil {
 				l.fail(LinkFailureError{code: ErrInternalError},
-					"unable to queue breach backup: %v", err)
+					"unable to queue breach backup: %v",
+					err)
 				return
 			}
 		}

watchtower/wtclient/client.go

@@ -136,11 +136,8 @@ type Client interface {
 	// state. If the method returns nil, the backup is guaranteed to be
 	// successful unless the client is force quit, or the justice
 	// transaction would create dust outputs when trying to abide by the
-	// negotiated policy. If the channel we're trying to back up doesn't
-	// have a tweak for the remote party's output, then isTweakless should
-	// be true.
-	BackupState(*lnwire.ChannelID, *lnwallet.BreachRetribution,
-		channeldb.ChannelType) error
+	// negotiated policy.
+	BackupState(chanID *lnwire.ChannelID, stateNum uint64) error
 
 	// Start initializes the watchtower client, allowing it process requests
 	// to backup revoked channel states.
@@ -805,32 +802,41 @@ func (c *TowerClient) RegisterChannel(chanID lnwire.ChannelID) error {
 //   - breached outputs contain too little value to sweep at the target sweep
 //     fee rate.
 func (c *TowerClient) BackupState(chanID *lnwire.ChannelID,
-	breachInfo *lnwallet.BreachRetribution,
-	chanType channeldb.ChannelType) error {
+	stateNum uint64) error {
 
 	// Retrieve the cached sweep pkscript used for this channel.
 	c.backupMu.Lock()
 	summary, ok := c.summaries[*chanID]
 	if !ok {
 		c.backupMu.Unlock()
+
 		return ErrUnregisteredChannel
 	}
 
 	// Ignore backups that have already been presented to the client.
 	height, ok := c.chanCommitHeights[*chanID]
-	if ok && breachInfo.RevokedStateNum <= height {
+	if ok && stateNum <= height {
 		c.backupMu.Unlock()
 		c.log.Debugf("Ignoring duplicate backup for chanid=%v at "+
-			"height=%d", chanID, breachInfo.RevokedStateNum)
+			"height=%d", chanID, stateNum)
+
 		return nil
 	}
 
 	// This backup has a higher commit height than any known backup for this
 	// channel. We'll update our tip so that we won't accept it again if the
 	// link flaps.
-	c.chanCommitHeights[*chanID] = breachInfo.RevokedStateNum
+	c.chanCommitHeights[*chanID] = stateNum
 	c.backupMu.Unlock()
 
+	// Fetch the breach retribution info and channel type.
+	breachInfo, chanType, err := c.cfg.BuildBreachRetribution(
+		*chanID, stateNum,
+	)
+	if err != nil {
+		return err
+	}
+
 	task := newBackupTask(
 		chanID, breachInfo, summary.SweepPkScript, chanType,
 	)

watchtower/wtclient/client_test.go

@@ -731,10 +731,9 @@ func (h *testHarness) backupState(id, i uint64, expErr error) {
 	_, retribution := h.channel(id).getState(i)
 
 	chanID := chanIDFromInt(id)
-	err := h.client.BackupState(
-		&chanID, retribution, channeldb.SingleFunderBit,
-	)
-	require.ErrorIs(h.t, err, expErr)
+
+	err := h.client.BackupState(&chanID, retribution.RevokedStateNum)
+	require.ErrorIs(h.t, expErr, err)
 }
 
 // sendPayments instructs the channel identified by id to send amt to the remote