multi: update GenTaprootFundingScript to pass tapscript root

In most cases, we won't yet be passing a root. The option usage helps us keep the control flow mostly unchanged.

Author: Roasbeef

contractcourt/chain_watcher.go

@@ -16,6 +16,7 @@ import (
 	"github.com/davecgh/go-spew/spew"
 	"github.com/lightningnetwork/lnd/chainntnfs"
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/lnwallet"
 )
@@ -301,8 +302,11 @@ func (c *chainWatcher) Start() error {
 		err error
 	)
 	if chanState.ChanType.IsTaproot() {
+		fundingOpts := fn.MapOptionZ(
+			chanState.TapscriptRoot, lnwallet.TapscriptRootToOpt,
+		)
 		c.fundingPkScript, _, err = input.GenTaprootFundingScript(
-			localKey, remoteKey, 0,
+			localKey, remoteKey, 0, fundingOpts...,
 		)
 		if err != nil {
 			return err

funding/manager.go

@@ -23,6 +23,7 @@ import (
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/channeldb/models"
 	"github.com/lightningnetwork/lnd/discovery"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/labels"
@@ -2853,8 +2854,12 @@ func makeFundingScript(channel *channeldb.OpenChannel) ([]byte, error) {
 	remoteKey := channel.RemoteChanCfg.MultiSigKey.PubKey
 
 	if channel.ChanType.IsTaproot() {
+		fundingOpts := fn.MapOptionZ(
+			channel.TapscriptRoot, lnwallet.TapscriptRootToOpt,
+		)
 		pkScript, _, err := input.GenTaprootFundingScript(
 			localKey, remoteKey, int64(channel.Capacity),
+			fundingOpts...,
 		)
 		if err != nil {
 			return nil, err

lnwallet/wallet.go

@@ -2442,6 +2442,12 @@ func initStateHints(commit1, commit2 *wire.MsgTx,
 	return nil
 }
 
+// TapscriptRootToOpt is a helper function that converts a tapscript root into
+// the functional option we can use to pass into GenTaprootFundingScript.
+func TapscriptRootToOpt(root chainhash.Hash) []input.FundingScriptOpt {
+	return []input.FundingScriptOpt{input.WithTapscriptRoot(root)}
+}
+
 // ValidateChannel will attempt to fully validate a newly mined channel, given
 // its funding transaction and existing channel state. If this method returns
 // an error, then the mined channel is invalid, and shouldn't be used.

routing/router.go

@@ -1549,6 +1549,8 @@ func makeFundingScript(bitcoinKey1, bitcoinKey2 []byte,
 			return nil, err
 		}
 
+		// TODO(roasbeef): add tapscript root to gossip v1.5
+
 		return fundingScript, nil
 	}