lnd.xprv/lntest/itest/lnd_multi-hop_htlc_aggregation_test.go

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package itest
import (
"context"
"fmt"
"time"
"github.com/btcsuite/btcd/chaincfg/chainhash"
"github.com/btcsuite/btcd/wire"
"github.com/lightningnetwork/lnd/lncfg"
"github.com/lightningnetwork/lnd/lnrpc"
"github.com/lightningnetwork/lnd/lnrpc/invoicesrpc"
"github.com/lightningnetwork/lnd/lnrpc/routerrpc"
"github.com/lightningnetwork/lnd/lntest"
"github.com/lightningnetwork/lnd/lntest/wait"
"github.com/lightningnetwork/lnd/lntypes"
"github.com/stretchr/testify/require"
)
// testMultiHopHtlcAggregation tests that in a multi-hop HTLC scenario, if we
// force close a channel with both incoming and outgoing HTLCs, we can properly
// resolve them using the second level timeout and success transactions. In
// case of anchor channels, the second-level spends can also be aggregated and
// properly feebumped, so we'll check that as well.
func testMultiHopHtlcAggregation(net *lntest.NetworkHarness, t *harnessTest,
alice, bob *lntest.HarnessNode, c commitType) {
const finalCltvDelta = 40
ctxb := context.Background()
// First, we'll create a three hop network: Alice -> Bob -> Carol.
aliceChanPoint, bobChanPoint, carol := createThreeHopNetwork(
t, net, alice, bob, false, c,
)
defer shutdownAndAssert(net, t, carol)
// To ensure we have capacity in both directions of the route, we'll
// make a fairly large payment Alice->Carol and settle it.
const reBalanceAmt = 500_000
invoice := &lnrpc.Invoice{
Value: reBalanceAmt,
}
ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
resp, err := carol.AddInvoice(ctxt, invoice)
require.NoError(t.t, err)
sendReq := &routerrpc.SendPaymentRequest{
PaymentRequest: resp.PaymentRequest,
TimeoutSeconds: 60,
FeeLimitMsat: noFeeLimitMsat,
}
ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
stream, err := alice.RouterClient.SendPaymentV2(ctxt, sendReq)
require.NoError(t.t, err)
result, err := getPaymentResult(stream)
require.NoError(t.t, err)
require.Equal(t.t, result.Status, lnrpc.Payment_SUCCEEDED)
// With the network active, we'll now add a new hodl invoices at both
// Alice's and Carol's end. Make sure the cltv expiry delta is large
// enough, otherwise Bob won't send out the outgoing htlc.
const numInvoices = 5
const invoiceAmt = 50_000
var (
carolInvoices []*invoicesrpc.AddHoldInvoiceResp
aliceInvoices []*invoicesrpc.AddHoldInvoiceResp
alicePreimages []lntypes.Preimage
payHashes [][]byte
alicePayHashes [][]byte
carolPayHashes [][]byte
)
// Add Carol invoices.
for i := 0; i < numInvoices; i++ {
preimage := lntypes.Preimage{1, 1, 1, byte(i)}
payHash := preimage.Hash()
invoiceReq := &invoicesrpc.AddHoldInvoiceRequest{
Value: invoiceAmt,
CltvExpiry: finalCltvDelta,
Hash: payHash[:],
}
ctxt, cancel := context.WithTimeout(ctxb, defaultTimeout)
defer cancel()
carolInvoice, err := carol.AddHoldInvoice(ctxt, invoiceReq)
require.NoError(t.t, err)
carolInvoices = append(carolInvoices, carolInvoice)
payHashes = append(payHashes, payHash[:])
carolPayHashes = append(carolPayHashes, payHash[:])
}
// We'll give Alice's invoices a longer CLTV expiry, to ensure the
// channel Bob<->Carol will be closed first.
for i := 0; i < numInvoices; i++ {
preimage := lntypes.Preimage{2, 2, 2, byte(i)}
payHash := preimage.Hash()
invoiceReq := &invoicesrpc.AddHoldInvoiceRequest{
Value: invoiceAmt,
CltvExpiry: 2 * finalCltvDelta,
Hash: payHash[:],
}
ctxt, cancel := context.WithTimeout(ctxb, defaultTimeout)
defer cancel()
aliceInvoice, err := alice.AddHoldInvoice(ctxt, invoiceReq)
require.NoError(t.t, err)
aliceInvoices = append(aliceInvoices, aliceInvoice)
alicePreimages = append(alicePreimages, preimage)
payHashes = append(payHashes, payHash[:])
alicePayHashes = append(alicePayHashes, payHash[:])
}
// Now that we've created the invoices, we'll pay them all from
// Alice<->Carol, going through Bob. We won't wait for the response
// however, as neither will immediately settle the payment.
ctx, cancel := context.WithCancel(ctxb)
defer cancel()
// Alice will pay all of Carol's invoices.
for _, carolInvoice := range carolInvoices {
_, err = alice.RouterClient.SendPaymentV2(
ctx, &routerrpc.SendPaymentRequest{
PaymentRequest: carolInvoice.PaymentRequest,
TimeoutSeconds: 60,
FeeLimitMsat: noFeeLimitMsat,
},
)
require.NoError(t.t, err)
}
// And Carol will pay Alice's.
for _, aliceInvoice := range aliceInvoices {
_, err = carol.RouterClient.SendPaymentV2(
ctx, &routerrpc.SendPaymentRequest{
PaymentRequest: aliceInvoice.PaymentRequest,
TimeoutSeconds: 60,
FeeLimitMsat: noFeeLimitMsat,
},
)
require.NoError(t.t, err)
}
// At this point, all 3 nodes should now the HTLCs active on their
// channels.
nodes := []*lntest.HarnessNode{alice, bob, carol}
err = wait.NoError(func() error {
return assertActiveHtlcs(nodes, payHashes...)
}, defaultTimeout)
require.NoError(t.t, err)
// Wait for Alice and Carol to mark the invoices as accepted. There is
// a small gap to bridge between adding the htlc to the channel and
// executing the exit hop logic.
for _, payHash := range carolPayHashes {
h := lntypes.Hash{}
copy(h[:], payHash)
waitForInvoiceAccepted(t, carol, h)
}
for _, payHash := range alicePayHashes {
h := lntypes.Hash{}
copy(h[:], payHash)
waitForInvoiceAccepted(t, alice, h)
}
// Increase the fee estimate so that the following force close tx will
// be cpfp'ed.
net.SetFeeEstimate(30000)
// We want Carol's htlcs to expire off-chain to demonstrate bob's force
// close. However, Carol will cancel her invoices to prevent force
// closes, so we shut her down for now.
restartCarol, err := net.SuspendNode(carol)
require.NoError(t.t, err)
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// We'll now mine enough blocks to trigger Bob's broadcast of his
// commitment transaction due to the fact that the Carol's HTLCs are
// about to timeout. With the default outgoing broadcast delta of zero,
// this will be the same height as the htlc expiry height.
numBlocks := padCLTV(
uint32(finalCltvDelta - lncfg.DefaultOutgoingBroadcastDelta),
)
_, err = net.Miner.Client.Generate(numBlocks)
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require.NoError(t.t, err)
// Bob's force close transaction should now be found in the mempool. If
// there are anchors, we also expect Bob's anchor sweep.
expectedTxes := 1
if c == commitTypeAnchors {
expectedTxes = 2
}
bobFundingTxid, err := lnrpc.GetChanPointFundingTxid(bobChanPoint)
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require.NoError(t.t, err)
_, err = waitForNTxsInMempool(
net.Miner.Client, expectedTxes, minerMempoolTimeout,
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)
require.NoError(t.t, err)
closeTx := getSpendingTxInMempool(
t, net.Miner.Client, minerMempoolTimeout, wire.OutPoint{
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Hash: *bobFundingTxid,
Index: bobChanPoint.OutputIndex,
},
)
closeTxid := closeTx.TxHash()
// Go through the closing transaction outputs, and make an index for the HTLC outputs.
successOuts := make(map[wire.OutPoint]struct{})
timeoutOuts := make(map[wire.OutPoint]struct{})
for i, txOut := range closeTx.TxOut {
op := wire.OutPoint{
Hash: closeTxid,
Index: uint32(i),
}
switch txOut.Value {
// If this HTLC goes towards Carol, Bob will claim it with a
// timeout Tx. In this case the value will be the invoice
// amount.
case invoiceAmt:
timeoutOuts[op] = struct{}{}
// If the HTLC has direction towards Alice, Bob will
// claim it with the success TX when he learns the preimage. In
// this case one extra sat will be on the output, because of
// the routing fee.
case invoiceAmt + 1:
successOuts[op] = struct{}{}
}
}
// Once bob has force closed, we can restart carol.
require.NoError(t.t, restartCarol())
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// Mine a block to confirm the closing transaction.
mineBlocks(t, net, 1, expectedTxes)
time.Sleep(1 * time.Second)
// Let Alice settle her invoices. When Bob now gets the preimages, he
// has no other option than to broadcast his second-level transactions
// to claim the money.
for _, preimage := range alicePreimages {
ctx, cancel = context.WithTimeout(ctxb, defaultTimeout)
defer cancel()
_, err = alice.SettleInvoice(ctx, &invoicesrpc.SettleInvoiceMsg{
Preimage: preimage[:],
})
require.NoError(t.t, err)
}
// With the closing transaction confirmed, we should expect Bob's HTLC
// timeout transactions to be broadcast due to the expiry being reached.
// We will also expect the success transactions, since he learnt the
// preimages from Alice. We also expect Carol to sweep her commitment
// output.
expectedTxes = 2*numInvoices + 1
// In case of anchors, all success transactions will be aggregated into
// one, the same is the case for the timeout transactions. In this case
// Carol will also sweep her anchor output in a separate tx (since it
// will be low fee).
if c == commitTypeAnchors {
expectedTxes = 4
}
txes, err := getNTxsFromMempool(
net.Miner.Client, expectedTxes, minerMempoolTimeout,
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)
require.NoError(t.t, err)
// Since Bob can aggregate the transactions, we expect a single
// transaction, that have multiple spends from the commitment.
var (
timeoutTxs []*chainhash.Hash
successTxs []*chainhash.Hash
)
for _, tx := range txes {
txid := tx.TxHash()
for i := range tx.TxIn {
prevOp := tx.TxIn[i].PreviousOutPoint
if _, ok := successOuts[prevOp]; ok {
successTxs = append(successTxs, &txid)
break
}
if _, ok := timeoutOuts[prevOp]; ok {
timeoutTxs = append(timeoutTxs, &txid)
break
}
}
}
// In case of anchor we expect all the timeout and success second
// levels to be aggregated into one tx. For earlier channel types, they
// will be separate transactions.
if c == commitTypeAnchors {
require.Len(t.t, timeoutTxs, 1)
require.Len(t.t, successTxs, 1)
} else {
require.Len(t.t, timeoutTxs, numInvoices)
require.Len(t.t, successTxs, numInvoices)
}
// All mempool transactions should be spending from the commitment
// transaction.
assertAllTxesSpendFrom(t, txes, closeTxid)
// Mine a block to confirm the transactions.
block := mineBlocks(t, net, 1, expectedTxes)[0]
require.Len(t.t, block.Transactions, expectedTxes+1)
// At this point, Bob should have broadcast his second layer success
// transaction, and should have sent it to the nursery for incubation,
// or to the sweeper for sweeping.
ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
err = waitForNumChannelPendingForceClose(
ctxt, bob, 1, func(c *lnrpcForceCloseChannel) error {
if c.Channel.LocalBalance != 0 {
return nil
}
if len(c.PendingHtlcs) != 1 {
return fmt.Errorf("bob should have pending " +
"htlc but doesn't")
}
if c.PendingHtlcs[0].Stage != 1 {
return fmt.Errorf("bob's htlc should have "+
"advanced to the first stage but was "+
"stage: %v", c.PendingHtlcs[0].Stage)
}
return nil
},
)
require.NoError(t.t, err)
// If we then mine additional blocks, Bob can sweep his commitment
// output.
_, err = net.Miner.Client.Generate(defaultCSV - 2)
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require.NoError(t.t, err)
// Find the commitment sweep.
bobCommitSweepHash, err := waitForTxInMempool(net.Miner.Client, minerMempoolTimeout)
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require.NoError(t.t, err)
bobCommitSweep, err := net.Miner.Client.GetRawTransaction(bobCommitSweepHash)
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require.NoError(t.t, err)
require.Equal(
t.t, closeTxid, bobCommitSweep.MsgTx().TxIn[0].PreviousOutPoint.Hash,
)
// Also ensure it is not spending from any of the HTLC output.
for _, txin := range bobCommitSweep.MsgTx().TxIn {
for _, timeoutTx := range timeoutTxs {
if *timeoutTx == txin.PreviousOutPoint.Hash {
t.Fatalf("found unexpected spend of timeout tx")
}
}
for _, successTx := range successTxs {
if *successTx == txin.PreviousOutPoint.Hash {
t.Fatalf("found unexpected spend of success tx")
}
}
}
switch {
// Mining one additional block, Bob's second level tx is mature, and he
// can sweep the output.
case c == commitTypeAnchors:
_ = mineBlocks(t, net, 1, 1)
// In case this is a non-anchor channel type, we must mine 2 blocks, as
// the nursery waits an extra block before sweeping.
default:
_ = mineBlocks(t, net, 2, 1)
}
bobSweep, err := waitForTxInMempool(net.Miner.Client, minerMempoolTimeout)
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require.NoError(t.t, err)
// Make sure it spends from the second level tx.
secondLevelSweep, err := net.Miner.Client.GetRawTransaction(bobSweep)
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require.NoError(t.t, err)
// It should be sweeping all the second-level outputs.
var secondLvlSpends int
for _, txin := range secondLevelSweep.MsgTx().TxIn {
for _, timeoutTx := range timeoutTxs {
if *timeoutTx == txin.PreviousOutPoint.Hash {
secondLvlSpends++
}
}
for _, successTx := range successTxs {
if *successTx == txin.PreviousOutPoint.Hash {
secondLvlSpends++
}
}
}
require.Equal(t.t, 2*numInvoices, secondLvlSpends)
// When we mine one additional block, that will confirm Bob's second
// level sweep. Now Bob should have no pending channels anymore, as
// this just resolved it by the confirmation of the sweep transaction.
block = mineBlocks(t, net, 1, 1)[0]
assertTxInBlock(t, block, bobSweep)
ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
err = waitForNumChannelPendingForceClose(ctxt, bob, 0, nil)
require.NoError(t.t, err)
// THe channel with Alice is still open.
assertNodeNumChannels(t, bob, 1)
// Carol should have no channels left (open nor pending).
err = waitForNumChannelPendingForceClose(ctxt, carol, 0, nil)
require.NoError(t.t, err)
assertNodeNumChannels(t, carol, 0)
// Coop close channel, expect no anchors.
ctxt, _ = context.WithTimeout(ctxb, channelCloseTimeout)
closeChannelAndAssertType(
ctxt, t, net, alice, aliceChanPoint, false, false,
)
}