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'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.Node.Generate(numBlocks) 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) require.NoError(t.t, err) _, err = waitForNTxsInMempool( net.Miner.Node, expectedTxes, minerMempoolTimeout, ) require.NoError(t.t, err) closeTx := getSpendingTxInMempool( t, net.Miner.Node, minerMempoolTimeout, wire.OutPoint{ 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{}{} } } // 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.Node, expectedTxes, minerMempoolTimeout, ) 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.Node.Generate(defaultCSV - 2) require.NoError(t.t, err) // Find the commitment sweep. bobCommitSweepHash, err := waitForTxInMempool(net.Miner.Node, minerMempoolTimeout) require.NoError(t.t, err) bobCommitSweep, err := net.Miner.Node.GetRawTransaction(bobCommitSweepHash) 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.Node, minerMempoolTimeout) require.NoError(t.t, err) // Make sure it spends from the second level tx. secondLevelSweep, err := net.Miner.Node.GetRawTransaction(bobSweep) 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, ) }