package itest import ( "context" "fmt" "github.com/btcsuite/btcd/wire" "github.com/lightningnetwork/lnd" "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" ) // testMultiHopHtlcLocalChainClaim tests that in a multi-hop HTLC scenario, if // we force close a channel with an incoming HTLC, and later find out the // preimage via the witness beacon, we properly settle the HTLC on-chain using // the HTLC success transaction in order to ensure we don't lose any funds. func testMultiHopHtlcLocalChainClaim(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, 3} 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) // At this point, Bob decides that he wants to exit the channel // immediately, so he force closes his commitment transaction. ctxt, _ = context.WithTimeout(ctxb, channelCloseTimeout) bobForceClose := closeChannelAndAssertType( ctxt, t, net, bob, aliceChanPoint, c == commitTypeAnchors, true, ) // Alice will sweep her commitment output immediately. If there are // anchors, Alice will also sweep hers. expectedTxes := 1 if c == commitTypeAnchors { expectedTxes = 2 } _, err = waitForNTxsInMempool( net.Miner.Node, expectedTxes, minerMempoolTimeout, ) require.NoError(t.t, err) // Suspend Bob to force Carol to go to 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)) _, err = net.Miner.Node.Generate(numBlocks) require.NoError(t.t, err) // Carol's commitment transaction should now be in the mempool. If there // is an anchor, Carol will sweep that too. _, err = waitForNTxsInMempool( net.Miner.Node, expectedTxes, minerMempoolTimeout, ) require.NoError(t.t, err) bobFundingTxid, err := lnd.GetChanPointFundingTxid(bobChanPoint) require.NoError(t.t, err) carolFundingPoint := wire.OutPoint{ Hash: *bobFundingTxid, Index: bobChanPoint.OutputIndex, } // Look up the closing transaction. It should be spending from the // funding transaction, closingTx := getSpendingTxInMempool( t, net.Miner.Node, minerMempoolTimeout, carolFundingPoint, ) closingTxid := closingTx.TxHash() // Mine a block that should confirm the commit tx, the anchor if present // and the coinbase. 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 on the commitment, Bob will also sweep his // anchor. expectedTxes = 2 if c == commitTypeAnchors { expectedTxes = 3 } txes, err := getNTxsFromMempool( net.Miner.Node, expectedTxes, minerMempoolTimeout, ) require.NoError(t.t, err) // Both Carol's second level transaction and Bob's sweep should be // spending from the commitment transaction. assertAllTxesSpendFrom(t, txes, closingTxid) // At this point we suspend Alice to make sure she'll handle the // on-chain settle after a restart. restartAlice, err := net.SuspendNode(alice) require.NoError(t.t, err) // Mine a block to confirm the two transactions (+ the coinbase). block = mineBlocks(t, net, 1, expectedTxes)[0] require.Len(t.t, block.Transactions, expectedTxes+1) var secondLevelMaturity uint32 switch c { // If this is a channel of the anchor type, we will subtract one block // from the default CSV, as the Sweeper will handle the input, and the Sweeper // sweeps the input as soon as the lock expires. case commitTypeAnchors: secondLevelMaturity = defaultCSV - 1 // For non-anchor channel types, the nursery will handle sweeping the // second level output, and it will wait one extra block before // sweeping it. default: secondLevelMaturity = defaultCSV } // Keep track of the second level tx maturity. carolSecondLevelCSV := secondLevelMaturity // When Bob notices Carol's second level transaction in the block, he // will extract the preimage and broadcast a second level tx to claim // the HTLC in his (already closed) channel with Alice. bobSecondLvlTx, 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(bobSecondLvlTx) require.NoError(t.t, err) require.Equal( t.t, *bobForceClose, tx.MsgTx().TxIn[0].PreviousOutPoint.Hash, ) // At this point, Bob should have broadcast his second layer success // transaction, and should have sent it to the nursery for incubation. 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) // We'll now mine a block which should confirm Bob's second layer // transaction. block = mineBlocks(t, net, 1, 1)[0] require.Len(t.t, block.Transactions, 2) assertTxInBlock(t, block, bobSecondLvlTx) // Keep track of Bob's second level maturity, and decrement our track // of Carol's. bobSecondLevelCSV := secondLevelMaturity carolSecondLevelCSV-- // Now that the preimage from Bob has hit the chain, restart Alice to // ensure she'll pick it up. err = restartAlice() require.NoError(t.t, err) // If we then mine 3 additional blocks, Carol's second level tx should // mature, and she can pull the funds from it with a sweep tx. _, err = net.Miner.Node.Generate(carolSecondLevelCSV) require.NoError(t.t, err) bobSecondLevelCSV -= carolSecondLevelCSV carolSweep, err := waitForTxInMempool(net.Miner.Node, minerMempoolTimeout) require.NoError(t.t, err) // Mining one additional block, Bob's second level tx is mature, and he // can sweep the output. block = mineBlocks(t, net, bobSecondLevelCSV, 1)[0] assertTxInBlock(t, block, carolSweep) bobSweep, err := waitForTxInMempool(net.Miner.Node, minerMempoolTimeout) require.NoError(t.t, err) // Make sure it spends from the second level tx. tx, err = net.Miner.Node.GetRawTransaction(bobSweep) require.NoError(t.t, err) require.Equal( t.t, *bobSecondLvlTx, tx.MsgTx().TxIn[0].PreviousOutPoint.Hash, ) // When we mine one additional block, that will confirm Bob's 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) assertNodeNumChannels(t, bob, 0) // Also Carol should have no channels left (open nor pending). err = waitForNumChannelPendingForceClose(ctxt, carol, 0, nil) require.NoError(t.t, err) assertNodeNumChannels(t, carol, 0) // 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) }