itest: add taproot chan support to basic channel funding

We keep in line with the existing test that uses implicit negotiation.
In the future, we should modify to also have explicit negotiation as
well.

itest/lnd_funding_test.go

@@ -34,8 +34,11 @@ func testBasicChannelFunding(ht *lntest.HarnessTest) {
 		lnrpc.CommitmentType_LEGACY,
 		lnrpc.CommitmentType_STATIC_REMOTE_KEY,
 		lnrpc.CommitmentType_ANCHORS,
+		lnrpc.CommitmentType_SIMPLE_TAPROOT,
 	}
 
+	// TODO(roasbeef): only testing implicit negotiation not also explicit?
+
 	// testFunding is a function closure that takes Carol and Dave's
 	// commitment types and test the funding flow.
 	testFunding := func(ht *lntest.HarnessTest, carolCommitType,
@@ -58,8 +61,18 @@ func testBasicChannelFunding(ht *lntest.HarnessTest) {
 		// connected to the funding flow can properly be executed.
 		ht.EnsureConnected(carol, dave)
 
+		var privateChan bool
+
+		// If this is to be a taproot channel type, then it needs to be
+		// private, otherwise it'll be rejected by Dave.
+		//
+		// TODO(roasbeef): lift after gossip 1.75
+		if carolCommitType == lnrpc.CommitmentType_SIMPLE_TAPROOT {
+			privateChan = true
+		}
+
 		carolChan, daveChan, closeChan := basicChannelFundingTest(
-			ht, carol, dave, nil,
+			ht, carol, dave, nil, privateChan,
 		)
 
 		// Both nodes should report the same commitment
@@ -74,14 +87,25 @@ func testBasicChannelFunding(ht *lntest.HarnessTest) {
 		expType := carolCommitType
 
 		switch daveCommitType {
+		// Dave supports taproot, type will be what Carol supports.
+		case lnrpc.CommitmentType_SIMPLE_TAPROOT:
+
 		// Dave supports anchors, type will be what Carol supports.
 		case lnrpc.CommitmentType_ANCHORS:
+			// However if Alice wants taproot chans, then we
+			// downgrade to anchors as this is still using implicit
+			// negotiation.
+			if expType == lnrpc.CommitmentType_SIMPLE_TAPROOT {
+				expType = lnrpc.CommitmentType_ANCHORS
+			}
 
 		// Dave only supports tweakless, channel will be downgraded to
 		// this type if Carol supports anchors.
 		case lnrpc.CommitmentType_STATIC_REMOTE_KEY:
 			if expType == lnrpc.CommitmentType_ANCHORS {
 				expType = lnrpc.CommitmentType_STATIC_REMOTE_KEY
+			} else if expType == lnrpc.CommitmentType_SIMPLE_TAPROOT {
+				expType = lnrpc.CommitmentType_STATIC_REMOTE_KEY
 			}
 
 		// Dave only supoprts legacy type, channel will be downgraded
@@ -104,6 +128,9 @@ func testBasicChannelFunding(ht *lntest.HarnessTest) {
 		case expType == lnrpc.CommitmentType_LEGACY &&
 			chansCommitType == lnrpc.CommitmentType_LEGACY:
 
+		case expType == lnrpc.CommitmentType_SIMPLE_TAPROOT &&
+			chansCommitType == lnrpc.CommitmentType_SIMPLE_TAPROOT:
+
 		default:
 			ht.Fatalf("expected nodes to signal "+
 				"commit type %v, instead got "+
@@ -145,7 +172,7 @@ test:
 // channel closure.
 func basicChannelFundingTest(ht *lntest.HarnessTest,
 	alice, bob *node.HarnessNode,
-	fundingShim *lnrpc.FundingShim) (*lnrpc.Channel,
+	fundingShim *lnrpc.FundingShim, privateChan bool) (*lnrpc.Channel,
 	*lnrpc.Channel, func()) {
 
 	chanAmt := funding.MaxBtcFundingAmount
@@ -172,6 +199,7 @@ func basicChannelFundingTest(ht *lntest.HarnessTest,
 		newResp.RemoteBalance.Msat += uint64(
 			lnwire.NewMSatFromSatoshis(remote),
 		)
+
 		// Deprecated fields.
 		newResp.Balance += int64(local) // nolint:staticcheck
 		ht.AssertChannelBalanceResp(node, newResp)
@@ -185,6 +213,7 @@ func basicChannelFundingTest(ht *lntest.HarnessTest,
 	// successfully.
 	chanPoint := ht.OpenChannel(
 		alice, bob, lntest.OpenChannelParams{
+			Private:     privateChan,
 			Amt:         chanAmt,
 			PushAmt:     pushAmt,
 			FundingShim: fundingShim,
@@ -528,7 +557,7 @@ func testExternalFundingChanPoint(ht *lntest.HarnessTest) {
 	// test as everything should now proceed as normal (a regular channel
 	// funding flow).
 	carolChan, daveChan, _ := basicChannelFundingTest(
-		ht, carol, dave, fundingShim2,
+		ht, carol, dave, fundingShim2, false,
 	)
 
 	// Both channels should be marked as frozen with the proper thaw

lntest/utils.go

@@ -123,6 +123,16 @@ func channelPointStr(chanPoint *lnrpc.ChannelPoint) string {
 	return cp.String()
 }
 
+// CommitTypeHasTaproot returns whether commitType is a taproot commitment.
+func CommitTypeHasTaproot(commitType lnrpc.CommitmentType) bool {
+	switch commitType {
+	case lnrpc.CommitmentType_SIMPLE_TAPROOT:
+		return true
+	default:
+		return false
+	}
+}
+
 // CommitTypeHasAnchors returns whether commitType uses anchor outputs.
 func CommitTypeHasAnchors(commitType lnrpc.CommitmentType) bool {
 	switch commitType {
@@ -149,6 +159,11 @@ func NodeArgsForCommitType(commitType lnrpc.CommitmentType) []string {
 			"--protocol.anchors",
 			"--protocol.script-enforced-lease",
 		}
+	case lnrpc.CommitmentType_SIMPLE_TAPROOT:
+		return []string{
+			"--protocol.anchors",
+			"--protocol.simple-taproot-chans",
+		}
 	}
 
 	return nil
@@ -172,11 +187,23 @@ func CalcStaticFee(c lnrpc.CommitmentType, numHTLCs int) btcutil.Amount {
 		feePerKw     = chainfee.SatPerKWeight(DefaultFeeRateSatPerKw)
 	)
 
+	switch {
+	// The taproot commitment type has the extra anchor outputs, but also a
+	// smaller witness field (will just be a normal key spend), so we need
+	// to account for that here as well.
+	case CommitTypeHasTaproot(c):
+		feePerKw = chainfee.SatPerKVByte(
+			defaultSatPerVByte * scale,
+		).FeePerKWeight()
+
+		commitWeight = input.TaprootCommitWeight
+		anchors = anchorSize
+
 	// The anchor commitment type is slightly heavier, and we must also add
 	// the value of the two anchors to the resulting fee the initiator
 	// pays. In addition the fee rate is capped at 10 sat/vbyte for anchor
 	// channels.
-	if CommitTypeHasAnchors(c) {
+	case CommitTypeHasAnchors(c):
 		feePerKw = chainfee.SatPerKVByte(
 			defaultSatPerVByte * scale,
 		).FeePerKWeight()