Merge pull request #6521 from guggero/p2tr-open-channel

chanfunding: properly support p2tr inputs in funding TX

docs/release-notes/release-notes-0.15.0.md

@@ -60,6 +60,10 @@ releases. Backward compatibility is not guaranteed!
 155](https://github.com/lightningnetwork/lnd/pull/6468), allowing it to connect
 to Bitcoin nodes that advertise a Tor v3 onion service address.
 
+[A new neutrino sub-server](https://github.com/lightningnetwork/lnd/pull/5652)
+capable of status checks, adding, disconnecting and listing peers, fetching
+compact filters and block/block headers.
+
 ## Bug Fixes
 
 * [Pipelining an UpdateFulfillHTLC message now only happens when the related UpdateAddHTLC is locked-in.](https://github.com/lightningnetwork/lnd/pull/6246)
@@ -87,12 +91,6 @@ to Bitcoin nodes that advertise a Tor v3 onion service address.
   first](https://github.com/lightningnetwork/lnd/pull/6214).
 
 * [Fixed crash in MuSig2Combine](https://github.com/lightningnetwork/lnd/pull/6502)
-  
-## Neutrino
-
-* [New neutrino sub-server](https://github.com/lightningnetwork/lnd/pull/5652)
-  capable of status checks, adding, disconnecting and listing
-  peers, fetching compact filters and block/block headers.
 
 * [Added signature length
   validation](https://github.com/lightningnetwork/lnd/pull/6314) when calling
@@ -141,6 +139,9 @@ from occurring that would result in an erroneous force close.](https://github.co
 * [Ignore addresses with unknown types in NodeAnnouncements](
   https://github.com/lightningnetwork/lnd/pull/6435)
 
+* [Taproot wallet inputs can also be used to fund
+  channels](https://github.com/lightningnetwork/lnd/pull/6521)
+
 ## Routing
 
 * [Add a new `time_pref` parameter to the QueryRoutes and SendPayment APIs](https://github.com/lightningnetwork/lnd/pull/6024) that

lntest/harness_net.go

@@ -1417,7 +1417,7 @@ func (n *NetworkHarness) DumpLogs(node *HarnessNode) (string, error) {
 func (n *NetworkHarness) SendCoins(t *testing.T, amt btcutil.Amount,
 	target *HarnessNode) {
 
-	err := n.sendCoins(
+	err := n.SendCoinsOfType(
 		amt, target, lnrpc.AddressType_WITNESS_PUBKEY_HASH, true,
 	)
 	require.NoErrorf(t, err, "unable to send coins for %s", target.Cfg.Name)
@@ -1429,7 +1429,7 @@ func (n *NetworkHarness) SendCoins(t *testing.T, amt btcutil.Amount,
 func (n *NetworkHarness) SendCoinsUnconfirmed(t *testing.T, amt btcutil.Amount,
 	target *HarnessNode) {
 
-	err := n.sendCoins(
+	err := n.SendCoinsOfType(
 		amt, target, lnrpc.AddressType_WITNESS_PUBKEY_HASH, false,
 	)
 	require.NoErrorf(
@@ -1443,7 +1443,7 @@ func (n *NetworkHarness) SendCoinsUnconfirmed(t *testing.T, amt btcutil.Amount,
 func (n *NetworkHarness) SendCoinsNP2WKH(t *testing.T, amt btcutil.Amount,
 	target *HarnessNode) {
 
-	err := n.sendCoins(
+	err := n.SendCoinsOfType(
 		amt, target, lnrpc.AddressType_NESTED_PUBKEY_HASH, true,
 	)
 	require.NoErrorf(
@@ -1457,16 +1457,18 @@ func (n *NetworkHarness) SendCoinsNP2WKH(t *testing.T, amt btcutil.Amount,
 func (n *NetworkHarness) SendCoinsP2TR(t *testing.T, amt btcutil.Amount,
 	target *HarnessNode) {
 
-	err := n.sendCoins(amt, target, lnrpc.AddressType_TAPROOT_PUBKEY, true)
+	err := n.SendCoinsOfType(
+		amt, target, lnrpc.AddressType_TAPROOT_PUBKEY, true,
+	)
 	require.NoErrorf(
 		t, err, "unable to send P2TR coins for %s", target.Cfg.Name,
 	)
 }
 
-// sendCoins attempts to send amt satoshis from the internal mining node to the
-// targeted lightning node. The confirmed boolean indicates whether the
+// SendCoinsOfType attempts to send amt satoshis from the internal mining node
+// to the targeted lightning node. The confirmed boolean indicates whether the
 // transaction that pays to the target should confirm.
-func (n *NetworkHarness) sendCoins(amt btcutil.Amount, target *HarnessNode,
+func (n *NetworkHarness) SendCoinsOfType(amt btcutil.Amount, target *HarnessNode,
 	addrType lnrpc.AddressType, confirmed bool) error {
 
 	ctx, cancel := context.WithTimeout(n.runCtx, DefaultTimeout)

lntest/itest/lnd_funding_test.go

@@ -244,8 +244,6 @@ func basicChannelFundingTest(t *harnessTest, net *lntest.NetworkHarness,
 // testUnconfirmedChannelFunding tests that our unconfirmed change outputs can
 // be used to fund channels.
 func testUnconfirmedChannelFunding(net *lntest.NetworkHarness, t *harnessTest) {
-	ctxb := context.Background()
-
 	const (
 		chanAmt = funding.MaxBtcFundingAmount
 		pushAmt = btcutil.Amount(100000)
@@ -256,27 +254,10 @@ func testUnconfirmedChannelFunding(net *lntest.NetworkHarness, t *harnessTest) {
 	defer shutdownAndAssert(net, t, carol)
 
 	// We'll send her some confirmed funds.
-	net.SendCoins(t.t, 2*chanAmt, carol)
-
-	// Now let Carol send some funds to herself, making a unconfirmed
-	// change output.
-	addrReq := &lnrpc.NewAddressRequest{
-		Type: lnrpc.AddressType_WITNESS_PUBKEY_HASH,
-	}
-	ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
-	resp, err := carol.NewAddress(ctxt, addrReq)
-	require.NoError(t.t, err, "unable to get new address")
-
-	sendReq := &lnrpc.SendCoinsRequest{
-		Addr:   resp.Address,
-		Amount: int64(chanAmt) / 5,
-	}
-	ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
-	_, err = carol.SendCoins(ctxt, sendReq)
-	require.NoError(t.t, err, "unable to send coins")
+	net.SendCoinsUnconfirmed(t.t, chanAmt*2, carol)
 
 	// Make sure the unconfirmed tx is seen in the mempool.
-	_, err = waitForTxInMempool(net.Miner.Client, minerMempoolTimeout)
+	_, err := waitForTxInMempool(net.Miner.Client, minerMempoolTimeout)
 	require.NoError(t.t, err, "failed to find tx in miner mempool")
 
 	// Now, we'll connect her to Alice so that they can open a channel
@@ -362,6 +343,141 @@ func testUnconfirmedChannelFunding(net *lntest.NetworkHarness, t *harnessTest) {
 	closeChannelAndAssert(t, net, carol, chanPoint, false)
 }
 
+// testChannelFundingInputTypes tests that any type of supported input type can
+// be used to fund channels.
+func testChannelFundingInputTypes(net *lntest.NetworkHarness, t *harnessTest) {
+	const (
+		chanAmt  = funding.MaxBtcFundingAmount
+		burnAddr = "bcrt1qxsnqpdc842lu8c0xlllgvejt6rhy49u6fmpgyz"
+	)
+	addrTypes := []lnrpc.AddressType{
+		lnrpc.AddressType_WITNESS_PUBKEY_HASH,
+		lnrpc.AddressType_NESTED_PUBKEY_HASH,
+		lnrpc.AddressType_TAPROOT_PUBKEY,
+	}
+
+	// We'll start off by creating a node for Carol.
+	carol := net.NewNode(t.t, "Carol", nil)
+	defer shutdownAndAssert(net, t, carol)
+
+	// Now, we'll connect her to Alice so that they can open a
+	// channel together.
+	net.ConnectNodes(t.t, carol, net.Alice)
+
+	for _, addrType := range addrTypes {
+		// We'll send her some confirmed funds.
+		err := net.SendCoinsOfType(chanAmt*2, carol, addrType, true)
+		require.NoErrorf(
+			t.t, err, "unable to send coins for carol and addr "+
+				"type %v", addrType,
+		)
+
+		chanOpenUpdate := openChannelStream(
+			t, net, carol, net.Alice, lntest.OpenChannelParams{
+				Amt: chanAmt,
+			},
+		)
+
+		// Creates a helper closure to be used below which asserts the
+		// proper response to a channel balance RPC.
+		checkChannelBalance := func(node *lntest.HarnessNode,
+			local, remote, pendingLocal,
+			pendingRemote btcutil.Amount) {
+
+			expectedResponse := &lnrpc.ChannelBalanceResponse{
+				LocalBalance: &lnrpc.Amount{
+					Sat: uint64(local),
+					Msat: uint64(lnwire.NewMSatFromSatoshis(
+						local,
+					)),
+				},
+				RemoteBalance: &lnrpc.Amount{
+					Sat: uint64(remote),
+					Msat: uint64(lnwire.NewMSatFromSatoshis(
+						remote,
+					)),
+				},
+				PendingOpenLocalBalance: &lnrpc.Amount{
+					Sat: uint64(pendingLocal),
+					Msat: uint64(lnwire.NewMSatFromSatoshis(
+						pendingLocal,
+					)),
+				},
+				PendingOpenRemoteBalance: &lnrpc.Amount{
+					Sat: uint64(pendingRemote),
+					Msat: uint64(lnwire.NewMSatFromSatoshis(
+						pendingRemote,
+					)),
+				},
+				UnsettledLocalBalance:  &lnrpc.Amount{},
+				UnsettledRemoteBalance: &lnrpc.Amount{},
+				// Deprecated fields.
+				Balance:            int64(local),
+				PendingOpenBalance: int64(pendingLocal),
+			}
+			assertChannelBalanceResp(t, node, expectedResponse)
+		}
+
+		// As the channel is pending open, it's expected Carol has both
+		// zero local and remote balances, and pending local/remote
+		// should not be zero.
+		//
+		// Note that atm we haven't obtained the chanPoint yet, so we
+		// use the type directly.
+		cType := lnrpc.CommitmentType_STATIC_REMOTE_KEY
+		carolLocalBalance := chanAmt - calcStaticFee(cType, 0)
+		checkChannelBalance(carol, 0, 0, carolLocalBalance, 0)
+
+		// For Alice, her local/remote balances should be zero, and the
+		// local/remote balances are the mirror of Carol's.
+		checkChannelBalance(net.Alice, 0, 0, 0, carolLocalBalance)
+
+		// Confirm the channel and wait for it to be recognized by both
+		// parties. Two transactions should be mined, the unconfirmed
+		// spend and the funding tx.
+		mineBlocks(t, net, 6, 1)
+		chanPoint, err := net.WaitForChannelOpen(chanOpenUpdate)
+		require.NoError(
+			t.t, err, "error while waiting for channel open",
+		)
+
+		// With the channel open, we'll check the balances on each side
+		// of the channel as a sanity check to ensure things worked out
+		// as intended.
+		checkChannelBalance(carol, carolLocalBalance, 0, 0, 0)
+		checkChannelBalance(net.Alice, 0, carolLocalBalance, 0, 0)
+
+		// Now that we're done with the test, the channel can be closed.
+		closeChannelAndAssert(t, net, carol, chanPoint, false)
+
+		// Empty out the wallet so there aren't any lingering coins.
+		sendAllCoinsConfirm(net, carol, t, burnAddr)
+	}
+}
+
+// sendAllCoinsConfirm sends all coins of the node's wallet to the given address
+// and awaits one confirmation.
+func sendAllCoinsConfirm(net *lntest.NetworkHarness, node *lntest.HarnessNode,
+	t *harnessTest, addr string) {
+
+	ctxb := context.Background()
+	ctxt, cancel := context.WithTimeout(ctxb, defaultTimeout)
+	defer cancel()
+
+	sweepReq := &lnrpc.SendCoinsRequest{
+		Addr:    addr,
+		SendAll: true,
+	}
+	_, err := node.SendCoins(ctxt, sweepReq)
+	require.NoError(t.t, err)
+
+	// Make sure the unconfirmed tx is seen in the mempool.
+	_, err = waitForTxInMempool(net.Miner.Client, minerMempoolTimeout)
+	require.NoError(t.t, err, "failed to find tx in miner mempool")
+
+	mineBlocks(t, net, 1, 1)
+}
+
 // testExternalFundingChanPoint tests that we're able to carry out a normal
 // channel funding workflow given a channel point that was constructed outside
 // the main daemon.

lntest/itest/lnd_test_list_on_test.go

@@ -24,6 +24,10 @@ var allTestCases = []*testCase{
 		name: "basic funding flow",
 		test: testBasicChannelFunding,
 	},
+	{
+		name: "basic funding flow with all input types",
+		test: testChannelFundingInputTypes,
+	},
 	{
 		name: "unconfirmed channel funding",
 		test: testUnconfirmedChannelFunding,

lnwallet/btcwallet/signer.go

@@ -41,6 +41,8 @@ func (b *BtcWallet) FetchInputInfo(prevOut *wire.OutPoint) (*lnwallet.Utxo, erro
 		addressType = lnwallet.WitnessPubKey
 	case txscript.IsPayToScriptHash(txOut.PkScript):
 		addressType = lnwallet.NestedWitnessPubKey
+	case txscript.IsPayToTaproot(txOut.PkScript):
+		addressType = lnwallet.TaprootPubkey
 	}
 
 	return &lnwallet.Utxo{

lnwallet/chanfunding/coin_select.go

@@ -79,6 +79,11 @@ func calculateFees(utxos []Coin, feeRate chainfee.SatPerKWeight) (btcutil.Amount
 		case txscript.IsPayToScriptHash(utxo.PkScript):
 			weightEstimate.AddNestedP2WKHInput()
 
+		case txscript.IsPayToTaproot(utxo.PkScript):
+			weightEstimate.AddTaprootKeySpendInput(
+				txscript.SigHashDefault,
+			)
+
 		default:
 			return 0, 0, &errUnsupportedInput{utxo.PkScript}
 		}

lnwallet/chanfunding/wallet_assembler.go

@@ -111,7 +111,6 @@ func (f *FullIntent) CompileFundingTx(extraInputs []*wire.TxIn,
 		f.coinSource, extraInputs,
 	)
 	signDesc := input.SignDescriptor{
-		HashType: txscript.SigHashAll,
 		SigHashes: txscript.NewTxSigHashes(
 			fundingTx, prevOutFetcher,
 		),
@@ -136,6 +135,13 @@ func (f *FullIntent) CompileFundingTx(extraInputs []*wire.TxIn,
 		}
 		signDesc.InputIndex = i
 
+		// We support spending a p2tr input ourselves. But not as part
+		// of their inputs.
+		signDesc.HashType = txscript.SigHashAll
+		if txscript.IsPayToTaproot(info.PkScript) {
+			signDesc.HashType = txscript.SigHashDefault
+		}
+
 		// Finally, we'll sign the input as is, and populate the input
 		// with the witness and sigScript (if needed).
 		inputScript, err := f.signer.ComputeInputScript(
@@ -398,7 +404,9 @@ var _ txscript.PrevOutputFetcher = (*SegWitV0DualFundingPrevOutputFetcher)(nil)
 //
 // NOTE: Since the actual pkScript and amounts aren't passed in, this will just
 // make sure that nothing will panic when creating a SegWit v0 sighash. But this
-// code will NOT WORK for transactions that spend any Taproot inputs!
+// code will NOT WORK for transactions that spend any _remote_ Taproot inputs!
+// So basically dual-funding won't work with Taproot inputs unless the UTXO info
+// is exchanged between the peers.
 func NewSegWitV0DualFundingPrevOutputFetcher(localSource CoinSource,
 	remoteInputs []*wire.TxIn) txscript.PrevOutputFetcher {