package itest import ( "context" "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" ) // testMultiHopHtlcRemoteChainClaim tests that in the multi-hop HTLC scenario, // if the remote party goes to chain while we have an incoming HTLC, then when // we found out the preimage via the witness beacon, we properly settle the // HTLC directly on-chain using the preimage in order to ensure that we don't // lose any funds. func testMultiHopHtlcRemoteChainClaim(net *lntest.NetworkHarness, t *harnessTest, alice, bob *lntest.HarnessNode, c commitType) { ctxb := context.Background() // First, we'll create a three hop network: Alice -> Bob -> Carol, with // Carol refusing to actually settle or directly cancel any HTLC's // self. aliceChanPoint, bobChanPoint, carol := createThreeHopNetwork( t, net, alice, bob, false, c, ) // Clean up carol's node when the test finishes. defer shutdownAndAssert(net, t, carol) // With the network active, we'll now add a new hodl invoice at Carol's // end. Make sure the cltv expiry delta is large enough, otherwise Bob // won't send out the outgoing htlc. const invoiceAmt = 100000 preimage := lntypes.Preimage{1, 2, 5} payHash := preimage.Hash() invoiceReq := &invoicesrpc.AddHoldInvoiceRequest{ Value: invoiceAmt, CltvExpiry: 40, Hash: payHash[:], } ctxt, cancel := context.WithTimeout(ctxb, defaultTimeout) defer cancel() carolInvoice, err := carol.AddHoldInvoice(ctxt, invoiceReq) require.NoError(t.t, err) // Now that we've created the invoice, we'll send a single payment from // Alice to Carol. We won't wait for the response however, as Carol // will not immediately settle the payment. ctx, cancel := context.WithCancel(ctxb) defer cancel() _, err = alice.RouterClient.SendPaymentV2( ctx, &routerrpc.SendPaymentRequest{ PaymentRequest: carolInvoice.PaymentRequest, TimeoutSeconds: 60, FeeLimitMsat: noFeeLimitMsat, }, ) require.NoError(t.t, err) // At this point, all 3 nodes should now have an active channel with // the created HTLC pending on all of them. nodes := []*lntest.HarnessNode{alice, bob, carol} err = wait.NoError(func() error { return assertActiveHtlcs(nodes, payHash[:]) }, defaultTimeout) require.NoError(t.t, err) // Wait for carol to mark invoice as accepted. There is a small gap to // bridge between adding the htlc to the channel and executing the exit // hop logic. waitForInvoiceAccepted(t, carol, payHash) // Increase the fee estimate so that the following force close tx will // be cpfp'ed. net.SetFeeEstimate(30000) // Next, Alice decides that she wants to exit the channel, so she'll // immediately force close the channel by broadcast her commitment // transaction. ctxt, _ = context.WithTimeout(ctxb, channelCloseTimeout) aliceForceClose := closeChannelAndAssertType( ctxt, t, net, alice, aliceChanPoint, c == commitTypeAnchors, true, ) // Wait for the channel to be marked pending force close. ctxt, _ = context.WithTimeout(ctxb, defaultTimeout) err = waitForChannelPendingForceClose(ctxt, alice, aliceChanPoint) require.NoError(t.t, err) // After closeChannelAndAssertType returns, it has mined a block so now // bob will attempt to redeem his anchor commitment (if the channel // type is of that type). if c == commitTypeAnchors { _, err = waitForNTxsInMempool( net.Miner.Node, 1, minerMempoolTimeout, ) if err != nil { t.Fatalf("unable to find bob's anchor commit sweep: %v", err) } } // Mine enough blocks for Alice to sweep her funds from the force // closed channel. closeChannelAndAssertType() already mined a block // containing the commitment tx and the commit sweep tx will be // broadcast immediately before it can be included in a block, so mine // one less than defaultCSV in order to perform mempool assertions. _, err = net.Miner.Node.Generate(defaultCSV - 1) require.NoError(t.t, err) // Alice should now sweep her funds. _, err = waitForNTxsInMempool( net.Miner.Node, 1, minerMempoolTimeout, ) require.NoError(t.t, err) // Suspend bob, so Carol is forced to go on chain. restartBob, err := net.SuspendNode(bob) require.NoError(t.t, err) // Settle invoice. This will just mark the invoice as settled, as there // is no link anymore to remove the htlc from the commitment tx. For // this test, it is important to actually settle and not leave the // invoice in the accepted state, because without a known preimage, the // channel arbitrator won't go to chain. ctx, cancel = context.WithTimeout(ctxb, defaultTimeout) defer cancel() _, err = carol.SettleInvoice(ctx, &invoicesrpc.SettleInvoiceMsg{ Preimage: preimage[:], }) require.NoError(t.t, err) // We'll now mine enough blocks so Carol decides that she needs to go // on-chain to claim the HTLC as Bob has been inactive. numBlocks := padCLTV(uint32( invoiceReq.CltvExpiry-lncfg.DefaultIncomingBroadcastDelta, ) - defaultCSV) _, err = net.Miner.Node.Generate(numBlocks) require.NoError(t.t, err) expectedTxes := 1 if c == commitTypeAnchors { expectedTxes = 2 } // Carol's commitment transaction should now be in the mempool. If // there are anchors, Carol also sweeps her anchor. _, err = waitForNTxsInMempool( net.Miner.Node, expectedTxes, minerMempoolTimeout, ) require.NoError(t.t, err) bobFundingTxid, err := lnrpc.GetChanPointFundingTxid(bobChanPoint) require.NoError(t.t, err) carolFundingPoint := wire.OutPoint{ Hash: *bobFundingTxid, Index: bobChanPoint.OutputIndex, } // The closing transaction should be spending from the funding // transaction. closingTx := getSpendingTxInMempool( t, net.Miner.Node, minerMempoolTimeout, carolFundingPoint, ) closingTxid := closingTx.TxHash() // Mine a block, which should contain: the commitment, possibly an // anchor sweep and the coinbase tx. block := mineBlocks(t, net, 1, expectedTxes)[0] require.Len(t.t, block.Transactions, expectedTxes+1) assertTxInBlock(t, block, &closingTxid) // Restart bob again. err = restartBob() require.NoError(t.t, err) // After the force close transacion is mined, Carol should broadcast her // second level HTLC transacion. Bob will broadcast a sweep tx to sweep // his output in the channel with Carol. He can do this immediately, as // the output is not timelocked since Carol was the one force closing. // If there are anchors, Bob should also sweep his. expectedTxes = 2 if c == commitTypeAnchors { expectedTxes = 3 } txes, err := getNTxsFromMempool( net.Miner.Node, expectedTxes, minerMempoolTimeout, ) require.NoError(t.t, err) // All transactions should be pending from the commitment transaction. assertAllTxesSpendFrom(t, txes, closingTxid) // Mine a block to confirm the two transactions (+ coinbase). block = mineBlocks(t, net, 1, expectedTxes)[0] require.Len(t.t, block.Transactions, expectedTxes+1) // Keep track of the second level tx maturity. carolSecondLevelCSV := uint32(defaultCSV) // When Bob notices Carol's second level transaction in the block, he // will extract the preimage and broadcast a sweep tx to directly claim // the HTLC in his (already closed) channel with Alice. bobHtlcSweep, err := waitForTxInMempool( net.Miner.Node, minerMempoolTimeout, ) require.NoError(t.t, err) // It should spend from the commitment in the channel with Alice. tx, err := net.Miner.Node.GetRawTransaction(bobHtlcSweep) require.NoError(t.t, err) require.Equal( t.t, *aliceForceClose, tx.MsgTx().TxIn[0].PreviousOutPoint.Hash, ) // We'll now mine a block which should confirm Bob's HTLC sweep // transaction. block = mineBlocks(t, net, 1, 1)[0] require.Len(t.t, block.Transactions, 2) assertTxInBlock(t, block, bobHtlcSweep) carolSecondLevelCSV-- // Now that the sweeping transaction has been confirmed, Bob should now // recognize that all contracts have been fully resolved, and show no // pending close channels. ctxt, _ = context.WithTimeout(ctxb, defaultTimeout) err = waitForNumChannelPendingForceClose(ctxt, bob, 0, nil) require.NoError(t.t, err) // If we then mine 3 additional blocks, Carol's second level tx will // mature, and she should pull the funds. _, err = net.Miner.Node.Generate(carolSecondLevelCSV) require.NoError(t.t, err) carolSweep, err := waitForTxInMempool( net.Miner.Node, minerMempoolTimeout, ) require.NoError(t.t, err) // When Carol's sweep gets confirmed, she should have no more pending // channels. block = mineBlocks(t, net, 1, 1)[0] assertTxInBlock(t, block, carolSweep) ctxt, _ = context.WithTimeout(ctxb, defaultTimeout) err = waitForNumChannelPendingForceClose(ctxt, carol, 0, nil) require.NoError(t.t, err) // The invoice should show as settled for Carol, indicating that it was // swept on-chain. invoicesReq := &lnrpc.ListInvoiceRequest{} invoicesResp, err := carol.ListInvoices(ctxb, invoicesReq) require.NoError(t.t, err) require.Len(t.t, invoicesResp.Invoices, 1) invoice := invoicesResp.Invoices[0] require.Equal(t.t, lnrpc.Invoice_SETTLED, invoice.State) require.Equal(t.t, int64(invoiceAmt), invoice.AmtPaidSat) // Finally, check that the Alice's payment is correctly marked // succeeded. ctxt, _ = context.WithTimeout(ctxt, defaultTimeout) err = checkPaymentStatus( ctxt, alice, preimage, lnrpc.Payment_SUCCEEDED, ) require.NoError(t.t, err) }