github.com/decred/dcrlnd@v0.7.6/lntest/itest/lnd_channel_graph_test.go

package itest

import (
	"bytes"
	"context"
	"fmt"
	"io"
	"testing"
	"time"

	"github.com/decred/dcrd/dcrutil/v4"
	"github.com/decred/dcrlnd/chainreg"
	"github.com/decred/dcrlnd/lnrpc"
	"github.com/decred/dcrlnd/lnrpc/routerrpc"
	"github.com/decred/dcrlnd/lntest"
	"github.com/decred/dcrlnd/lntest/wait"
	"github.com/stretchr/testify/require"
)

// testUpdateChanStatus checks that calls to the UpdateChanStatus RPC update
// the channel graph as expected, and that channel state is properly updated
// in the presence of interleaved node disconnects / reconnects.
func testUpdateChanStatus(net *lntest.NetworkHarness, t *harnessTest) {
	ctxb := context.Background()

	// Create two fresh nodes and open a channel between them.
	alice := net.NewNode(t.t, "Alice", []string{
		"--minbackoff=10s",
		"--chan-enable-timeout=1.5s",
		"--chan-disable-timeout=3s",
		"--chan-status-sample-interval=.5s",
	})
	defer shutdownAndAssert(net, t, alice)

	bob := net.NewNode(t.t, "Bob", []string{
		"--minbackoff=10s",
		"--chan-enable-timeout=1.5s",
		"--chan-disable-timeout=3s",
		"--chan-status-sample-interval=.5s",
	})
	defer shutdownAndAssert(net, t, bob)

	// Connect Alice to Bob.
	net.ConnectNodes(t.t, alice, bob)

	// Give Alice some coins so she can fund a channel.
	net.SendCoins(t.t, dcrutil.AtomsPerCoin, alice)

	// Open a channel with 100k satoshis between Alice and Bob with Alice
	// being the sole funder of the channel.
	chanAmt := dcrutil.Amount(100000)
	chanPoint := openChannelAndAssert(
		t, net, alice, bob, lntest.OpenChannelParams{
			Amt: chanAmt,
		},
	)

	// Wait for Alice and Bob to receive the channel edge from the
	// funding manager.
	err := alice.WaitForNetworkChannelOpen(chanPoint)
	require.NoError(t.t, err, "alice didn't see the alice->bob channel")

	err = bob.WaitForNetworkChannelOpen(chanPoint)
	require.NoError(t.t, err, "bob didn't see the alice->bob channel")

	// Launch a node for Carol which will connect to Alice and Bob in order
	// to receive graph updates. This will ensure that the channel updates
	// are propagated throughout the network.
	carol := net.NewNode(t.t, "Carol", nil)
	defer shutdownAndAssert(net, t, carol)

	// Connect both Alice and Bob to the new node Carol, so she can sync her
	// graph.
	net.ConnectNodes(t.t, alice, carol)
	net.ConnectNodes(t.t, bob, carol)
	waitForGraphSync(t, carol)

	// assertChannelUpdate checks that the required policy update has
	// happened on the given node.
	assertChannelUpdate := func(node *lntest.HarnessNode,
		policy *lnrpc.RoutingPolicy) {

		require.NoError(
			t.t, carol.WaitForChannelPolicyUpdate(
				node.PubKeyStr, policy, chanPoint, false,
			), "error while waiting for channel update",
		)
	}

	// sendReq sends an UpdateChanStatus request to the given node.
	sendReq := func(node *lntest.HarnessNode, chanPoint *lnrpc.ChannelPoint,
		action routerrpc.ChanStatusAction) {

		req := &routerrpc.UpdateChanStatusRequest{
			ChanPoint: chanPoint,
			Action:    action,
		}
		ctxt, cancel := context.WithTimeout(ctxb, defaultTimeout)
		defer cancel()

		_, err = node.RouterClient.UpdateChanStatus(ctxt, req)
		require.NoErrorf(t.t, err, "UpdateChanStatus")
	}

	// assertEdgeDisabled ensures that a given node has the correct
	// Disabled state for a channel.
	assertEdgeDisabled := func(node *lntest.HarnessNode,
		chanPoint *lnrpc.ChannelPoint, disabled bool) {

		outPoint, err := lntest.MakeOutpoint(chanPoint)
		require.NoError(t.t, err)

		err = wait.NoError(func() error {
			req := &lnrpc.ChannelGraphRequest{
				IncludeUnannounced: true,
			}
			ctxt, cancel := context.WithTimeout(ctxb, defaultTimeout)
			defer cancel()

			chanGraph, err := node.DescribeGraph(ctxt, req)
			if err != nil {
				return fmt.Errorf("unable to query node %v's "+
					"graph: %v", node, err)
			}
			numEdges := len(chanGraph.Edges)
			if numEdges != 1 {
				return fmt.Errorf("expected to find 1 edge in "+
					"the graph, found %d", numEdges)
			}
			edge := chanGraph.Edges[0]
			if edge.ChanPoint != outPoint.String() {
				return fmt.Errorf("expected chan_point %v, "+
					"got %v", outPoint, edge.ChanPoint)
			}
			var policy *lnrpc.RoutingPolicy
			if node.PubKeyStr == edge.Node1Pub {
				policy = edge.Node1Policy
			} else {
				policy = edge.Node2Policy
			}
			if disabled != policy.Disabled {
				return fmt.Errorf("expected policy.Disabled "+
					"to be %v, but policy was %v", disabled,
					policy)
			}

			return nil
		}, defaultTimeout)
		require.NoError(t.t, err)
	}

	// When updating the state of the channel between Alice and Bob, we
	// should expect to see channel updates with the default routing
	// policy. The value of "Disabled" will depend on the specific
	// scenario being tested.
	expectedPolicy := &lnrpc.RoutingPolicy{
		FeeBaseMAtoms:      int64(chainreg.DefaultDecredBaseFeeMAtoms),
		FeeRateMilliMAtoms: int64(chainreg.DefaultDecredFeeRate),
		TimeLockDelta:      chainreg.DefaultDecredTimeLockDelta,
		MinHtlc:            1000, // default value
		MaxHtlcMAtoms:      calculateMaxHtlc(chanAmt),
	}

	// Initially, the channel between Alice and Bob should not be
	// disabled.
	assertEdgeDisabled(alice, chanPoint, false)

	// Manually disable the channel and ensure that a "Disabled = true"
	// update is propagated.
	sendReq(alice, chanPoint, routerrpc.ChanStatusAction_DISABLE)
	expectedPolicy.Disabled = true
	assertChannelUpdate(alice, expectedPolicy)

	// Re-enable the channel and ensure that a "Disabled = false" update
	// is propagated.
	sendReq(alice, chanPoint, routerrpc.ChanStatusAction_ENABLE)
	expectedPolicy.Disabled = false
	assertChannelUpdate(alice, expectedPolicy)

	// Manually enabling a channel should NOT prevent subsequent
	// disconnections from automatically disabling the channel again
	// (we don't want to clutter the network with channels that are
	// falsely advertised as enabled when they don't work).
	require.NoError(t.t, net.DisconnectNodes(alice, bob))
	expectedPolicy.Disabled = true
	assertChannelUpdate(alice, expectedPolicy)
	assertChannelUpdate(bob, expectedPolicy)

	// Reconnecting the nodes should propagate a "Disabled = false" update.
	net.EnsureConnected(t.t, alice, bob)
	expectedPolicy.Disabled = false
	assertChannelUpdate(alice, expectedPolicy)
	assertChannelUpdate(bob, expectedPolicy)

	// Manually disabling the channel should prevent a subsequent
	// disconnect / reconnect from re-enabling the channel on
	// Alice's end. Note the asymmetry between manual enable and
	// manual disable!
	sendReq(alice, chanPoint, routerrpc.ChanStatusAction_DISABLE)

	// Alice sends out the "Disabled = true" update in response to
	// the ChanStatusAction_DISABLE request.
	expectedPolicy.Disabled = true
	assertChannelUpdate(alice, expectedPolicy)

	require.NoError(t.t, net.DisconnectNodes(alice, bob))

	// Bob sends a "Disabled = true" update upon detecting the
	// disconnect.
	expectedPolicy.Disabled = true
	assertChannelUpdate(bob, expectedPolicy)

	// Bob sends a "Disabled = false" update upon detecting the
	// reconnect.
	net.EnsureConnected(t.t, alice, bob)
	expectedPolicy.Disabled = false
	assertChannelUpdate(bob, expectedPolicy)

	// However, since we manually disabled the channel on Alice's end,
	// the policy on Alice's end should still be "Disabled = true". Again,
	// note the asymmetry between manual enable and manual disable!
	assertEdgeDisabled(alice, chanPoint, true)

	require.NoError(t.t, net.DisconnectNodes(alice, bob))

	// Bob sends a "Disabled = true" update upon detecting the
	// disconnect.
	expectedPolicy.Disabled = true
	assertChannelUpdate(bob, expectedPolicy)

	// After restoring automatic channel state management on Alice's end,
	// BOTH Alice and Bob should set the channel state back to "enabled"
	// on reconnect.
	sendReq(alice, chanPoint, routerrpc.ChanStatusAction_AUTO)
	net.EnsureConnected(t.t, alice, bob)

	expectedPolicy.Disabled = false
	assertChannelUpdate(alice, expectedPolicy)
	assertChannelUpdate(bob, expectedPolicy)
	assertEdgeDisabled(alice, chanPoint, false)
}

// testUnannouncedChannels checks unannounced channels are not returned by
// describeGraph RPC request unless explicitly asked for.
func testUnannouncedChannels(net *lntest.NetworkHarness, t *harnessTest) {
	ctxb := context.Background()

	amount := defaultChanAmt

	// Open a channel between Alice and Bob, ensuring the
	// channel has been opened properly.
	chanOpenUpdate := openChannelStream(
		t, net, net.Alice, net.Bob,
		lntest.OpenChannelParams{
			Amt: amount,
		},
	)

	// Mine 2 blocks, and check that the channel is opened but not yet
	// announced to the network.
	mineBlocks(t, net, 2, 1)

	// One block is enough to make the channel ready for use, since the
	// nodes have defaultNumConfs=1 set.
	fundingChanPoint, err := net.WaitForChannelOpen(chanOpenUpdate)
	if err != nil {
		t.Fatalf("error while waiting for channel open: %v", err)
	}

	// Alice should have 1 edge in her graph.
	req := &lnrpc.ChannelGraphRequest{
		IncludeUnannounced: true,
	}
	ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
	chanGraph, err := net.Alice.DescribeGraph(ctxt, req)
	if err != nil {
		t.Fatalf("unable to query alice's graph: %v", err)
	}

	numEdges := len(chanGraph.Edges)
	if numEdges != 1 {
		t.Fatalf("expected to find 1 edge in the graph, found %d", numEdges)
	}

	// Channels should not be announced yet, hence Alice should have no
	// announced edges in her graph.
	req.IncludeUnannounced = false
	ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
	chanGraph, err = net.Alice.DescribeGraph(ctxt, req)
	if err != nil {
		t.Fatalf("unable to query alice's graph: %v", err)
	}

	numEdges = len(chanGraph.Edges)
	if numEdges != 0 {
		t.Fatalf("expected to find 0 announced edges in the graph, found %d",
			numEdges)
	}

	// Mine 4 more blocks, and check that the channel is now announced.
	mineBlocks(t, net, 4, 0)

	// Give the network a chance to learn that auth proof is confirmed.
	var predErr error
	err = wait.Predicate(func() bool {
		// The channel should now be announced. Check that Alice has 1
		// announced edge.
		req.IncludeUnannounced = false
		ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
		chanGraph, err = net.Alice.DescribeGraph(ctxt, req)
		if err != nil {
			predErr = fmt.Errorf("unable to query alice's graph: %v", err)
			return false
		}

		numEdges = len(chanGraph.Edges)
		if numEdges != 1 {
			predErr = fmt.Errorf("expected to find 1 announced edge in "+
				"the graph, found %d", numEdges)
			return false
		}
		return true
	}, defaultTimeout)
	if err != nil {
		t.Fatalf("%v", predErr)
	}

	// The channel should now be announced. Check that Alice has 1 announced
	// edge.
	req.IncludeUnannounced = false
	ctxt, _ = context.WithTimeout(ctxb, defaultTimeout)
	chanGraph, err = net.Alice.DescribeGraph(ctxt, req)
	if err != nil {
		t.Fatalf("unable to query alice's graph: %v", err)
	}

	numEdges = len(chanGraph.Edges)
	if numEdges != 1 {
		t.Fatalf("expected to find 1 announced edge in the graph, found %d",
			numEdges)
	}

	// Close the channel used during the test.
	closeChannelAndAssert(t, net, net.Alice, fundingChanPoint, false)
}

func testGraphTopologyNotifications(net *lntest.NetworkHarness, t *harnessTest) {
	t.t.Run("pinned", func(t *testing.T) {
		ht := newHarnessTest(t, net)
		testGraphTopologyNtfns(net, ht, true)
	})
	t.t.Run("unpinned", func(t *testing.T) {
		ht := newHarnessTest(t, net)
		testGraphTopologyNtfns(net, ht, false)
	})
}

func testGraphTopologyNtfns(net *lntest.NetworkHarness, t *harnessTest, pinned bool) {
	ctxb := context.Background()

	const chanAmt = defaultChanAmt

	// Spin up Bob first, since we will need to grab his pubkey when
	// starting Alice to test pinned syncing.
	bob := net.NewNode(t.t, "bob", nil)
	defer shutdownAndAssert(net, t, bob)

	ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
	bobInfo, err := bob.GetInfo(ctxt, &lnrpc.GetInfoRequest{})
	require.NoError(t.t, err)
	bobPubkey := bobInfo.IdentityPubkey

	// For unpinned syncing, start Alice as usual. Otherwise grab Bob's
	// pubkey to include in his pinned syncer set.
	var aliceArgs []string
	if pinned {
		aliceArgs = []string{
			"--numgraphsyncpeers=0",
			fmt.Sprintf("--gossip.pinned-syncers=%s", bobPubkey),
		}
	}

	alice := net.NewNode(t.t, "alice", aliceArgs)
	defer shutdownAndAssert(net, t, alice)

	// Connect Alice and Bob.
	net.EnsureConnected(t.t, alice, bob)

	// Alice stimmy.
	net.SendCoins(t.t, dcrutil.AtomsPerCoin, alice)

	// Bob stimmy.
	net.SendCoins(t.t, dcrutil.AtomsPerCoin, bob)

	// Assert that Bob has the correct sync type before proceeeding.
	if pinned {
		assertSyncType(t, alice, bobPubkey, lnrpc.Peer_PINNED_SYNC)
	} else {
		assertSyncType(t, alice, bobPubkey, lnrpc.Peer_ACTIVE_SYNC)
	}

	// Regardless of syncer type, ensure that both peers report having
	// completed their initial sync before continuing to make a channel.
	waitForGraphSync(t, alice)

	// Let Alice subscribe to graph notifications.
	graphSub := subscribeGraphNotifications(ctxb, t, alice)
	defer close(graphSub.quit)

	// Open a new channel between Alice and Bob.
	chanPoint := openChannelAndAssert(
		t, net, alice, bob,
		lntest.OpenChannelParams{
			Amt: chanAmt,
		},
	)

	// The channel opening above should have triggered a few notifications
	// sent to the notification client. We'll expect two channel updates,
	// and two node announcements.
	var numChannelUpds int
	var numNodeAnns int
	for numChannelUpds < 2 && numNodeAnns < 2 {
		select {
		// Ensure that a new update for both created edges is properly
		// dispatched to our registered client.
		case graphUpdate := <-graphSub.updateChan:
			// Process all channel updates prsented in this update
			// message.
			for _, chanUpdate := range graphUpdate.ChannelUpdates {
				switch chanUpdate.AdvertisingNode {
				case alice.PubKeyStr:
				case bob.PubKeyStr:
				default:
					t.Fatalf("unknown advertising node: %v",
						chanUpdate.AdvertisingNode)
				}
				switch chanUpdate.ConnectingNode {
				case alice.PubKeyStr:
				case bob.PubKeyStr:
				default:
					t.Fatalf("unknown connecting node: %v",
						chanUpdate.ConnectingNode)
				}

				if chanUpdate.Capacity != int64(chanAmt) {
					t.Fatalf("channel capacities mismatch:"+
						" expected %v, got %v", chanAmt,
						dcrutil.Amount(chanUpdate.Capacity))
				}
				numChannelUpds++
			}

			for _, nodeUpdate := range graphUpdate.NodeUpdates {
				switch nodeUpdate.IdentityKey {
				case alice.PubKeyStr:
				case bob.PubKeyStr:
				default:
					t.Fatalf("unknown node: %v",
						nodeUpdate.IdentityKey)
				}
				numNodeAnns++
			}
		case err := <-graphSub.errChan:
			t.Fatalf("unable to recv graph update: %v", err)
		case <-time.After(time.Second * 10):
			t.Fatalf("timeout waiting for graph notifications, "+
				"only received %d/2 chanupds and %d/2 nodeanns",
				numChannelUpds, numNodeAnns)
		}
	}

	_, blockHeight, err := net.Miner.Node.GetBestBlock(context.Background())
	if err != nil {
		t.Fatalf("unable to get current blockheight %v", err)
	}

	// Now we'll test that updates are properly sent after channels are closed
	// within the network.
	closeChannelAndAssert(t, net, alice, chanPoint, false)

	// Now that the channel has been closed, we should receive a
	// notification indicating so.
out:
	for {
		select {
		case graphUpdate := <-graphSub.updateChan:
			if len(graphUpdate.ClosedChans) != 1 {
				continue
			}

			closedChan := graphUpdate.ClosedChans[0]
			if closedChan.ClosedHeight != uint32(blockHeight+1) {
				t.Fatalf("close heights of channel mismatch: "+
					"expected %v, got %v", blockHeight+1,
					closedChan.ClosedHeight)
			}
			chanPointTxid, err := lnrpc.GetChanPointFundingTxid(chanPoint)
			if err != nil {
				t.Fatalf("unable to get txid: %v", err)
			}
			closedChanTxid, err := lnrpc.GetChanPointFundingTxid(
				closedChan.ChanPoint,
			)
			if err != nil {
				t.Fatalf("unable to get txid: %v", err)
			}
			if !bytes.Equal(closedChanTxid[:], chanPointTxid[:]) {
				t.Fatalf("channel point hash mismatch: "+
					"expected %v, got %v", chanPointTxid,
					closedChanTxid)
			}
			if closedChan.ChanPoint.OutputIndex != chanPoint.OutputIndex {
				t.Fatalf("output index mismatch: expected %v, "+
					"got %v", chanPoint.OutputIndex,
					closedChan.ChanPoint)
			}

			break out

		case err := <-graphSub.errChan:
			t.Fatalf("unable to recv graph update: %v", err)
		case <-time.After(time.Second * 10):
			t.Fatalf("notification for channel closure not " +
				"sent")
		}
	}

	// For the final portion of the test, we'll ensure that once a new node
	// appears in the network, the proper notification is dispatched. Note
	// that a node that does not have any channels open is ignored, so first
	// we disconnect Alice and Bob, open a channel between Bob and Carol,
	// and finally connect Alice to Bob again.
	if err := net.DisconnectNodes(alice, bob); err != nil {
		t.Fatalf("unable to disconnect alice and bob: %v", err)
	}
	carol := net.NewNode(t.t, "Carol", nil)
	defer shutdownAndAssert(net, t, carol)

	net.ConnectNodes(t.t, bob, carol)
	chanPoint = openChannelAndAssert(
		t, net, bob, carol,
		lntest.OpenChannelParams{
			Amt: chanAmt,
		},
	)

	// Reconnect Alice and Bob. This should result in the nodes syncing up
	// their respective graph state, with the new addition being the
	// existence of Carol in the graph, and also the channel between Bob
	// and Carol. Note that we will also receive a node announcement from
	// Bob, since a node will update its node announcement after a new
	// channel is opened.
	net.EnsureConnected(t.t, alice, bob)

	// We should receive an update advertising the newly connected node,
	// Bob's new node announcement, and the channel between Bob and Carol.
	numNodeAnns = 0
	numChannelUpds = 0
	for numChannelUpds < 2 && numNodeAnns < 1 {
		select {
		case graphUpdate := <-graphSub.updateChan:
			for _, nodeUpdate := range graphUpdate.NodeUpdates {
				switch nodeUpdate.IdentityKey {
				case carol.PubKeyStr:
				case bob.PubKeyStr:
				default:
					t.Fatalf("unknown node update pubey: %v",
						nodeUpdate.IdentityKey)
				}
				numNodeAnns++
			}

			for _, chanUpdate := range graphUpdate.ChannelUpdates {
				switch chanUpdate.AdvertisingNode {
				case carol.PubKeyStr:
				case bob.PubKeyStr:
				default:
					t.Fatalf("unknown advertising node: %v",
						chanUpdate.AdvertisingNode)
				}
				switch chanUpdate.ConnectingNode {
				case carol.PubKeyStr:
				case bob.PubKeyStr:
				default:
					t.Fatalf("unknown connecting node: %v",
						chanUpdate.ConnectingNode)
				}

				if chanUpdate.Capacity != int64(chanAmt) {
					t.Fatalf("channel capacities mismatch:"+
						" expected %v, got %v", chanAmt,
						dcrutil.Amount(chanUpdate.Capacity))
				}
				numChannelUpds++
			}
		case err := <-graphSub.errChan:
			t.Fatalf("unable to recv graph update: %v", err)
		case <-time.After(time.Second * 10):
			t.Fatalf("timeout waiting for graph notifications, "+
				"only received %d/2 chanupds and %d/2 nodeanns",
				numChannelUpds, numNodeAnns)
		}
	}

	// Close the channel between Bob and Carol.
	closeChannelAndAssert(t, net, bob, chanPoint, false)
}

// testNodeAnnouncement ensures that when a node is started with one or more
// external IP addresses specified on the command line, that those addresses
// announced to the network and reported in the network graph.
func testNodeAnnouncement(net *lntest.NetworkHarness, t *harnessTest) {
	ctxb := context.Background()

	aliceSub := subscribeGraphNotifications(ctxb, t, net.Alice)
	defer close(aliceSub.quit)

	advertisedAddrs := []string{
		"192.168.1.1:8333",
		"[2001:db8:85a3:8d3:1319:8a2e:370:7348]:8337",
		"bkb6azqggsaiskzi.onion:9735",
		"fomvuglh6h6vcag73xo5t5gv56ombih3zr2xvplkpbfd7wrog4swjwid.onion:1234",
	}

	var lndArgs []string
	for _, addr := range advertisedAddrs {
		lndArgs = append(lndArgs, "--externalip="+addr)
	}

	dave := net.NewNode(t.t, "Dave", lndArgs)
	defer shutdownAndAssert(net, t, dave)

	// We must let Dave have an open channel before he can send a node
	// announcement, so we open a channel with Bob,
	net.ConnectNodes(t.t, net.Bob, dave)

	// Alice shouldn't receive any new updates yet since the channel has yet
	// to be opened.
	select {
	case <-aliceSub.updateChan:
		t.Fatalf("received unexpected update from dave")
	case <-time.After(time.Second):
	}

	// We'll then go ahead and open a channel between Bob and Dave. This
	// ensures that Alice receives the node announcement from Bob as part of
	// the announcement broadcast.
	chanPoint := openChannelAndAssert(
		t, net, net.Bob, dave,
		lntest.OpenChannelParams{
			Amt: 1000000,
		},
	)

	assertAddrs := func(addrsFound []string, targetAddrs ...string) {
		addrs := make(map[string]struct{}, len(addrsFound))
		for _, addr := range addrsFound {
			addrs[addr] = struct{}{}
		}

		for _, addr := range targetAddrs {
			if _, ok := addrs[addr]; !ok {
				t.Fatalf("address %v not found in node "+
					"announcement", addr)
			}
		}
	}

	waitForAddrsInUpdate := func(graphSub graphSubscription,
		nodePubKey string, targetAddrs ...string) {

		for {
			select {
			case graphUpdate := <-graphSub.updateChan:
				for _, update := range graphUpdate.NodeUpdates {
					if update.IdentityKey == nodePubKey {
						assertAddrs(
							update.Addresses,
							targetAddrs...,
						)
						return
					}
				}
			case err := <-graphSub.errChan:
				t.Fatalf("unable to recv graph update: %v", err)
			case <-time.After(defaultTimeout):
				t.Fatalf("did not receive node ann update")
			}
		}
	}

	// We'll then wait for Alice to receive Dave's node announcement
	// including the expected advertised addresses from Bob since they
	// should already be connected.
	waitForAddrsInUpdate(
		aliceSub, dave.PubKeyStr, advertisedAddrs...,
	)

	// Close the channel between Bob and Dave.
	closeChannelAndAssert(t, net, net.Bob, chanPoint, false)
}

// graphSubscription houses the proxied update and error chans for a node's
// graph subscriptions.
type graphSubscription struct {
	updateChan chan *lnrpc.GraphTopologyUpdate
	errChan    chan error
	quit       chan struct{}
}

// subscribeGraphNotifications subscribes to channel graph updates and launches
// a goroutine that forwards these to the returned channel.
func subscribeGraphNotifications(ctxb context.Context, t *harnessTest,
	node *lntest.HarnessNode) graphSubscription {

	// We'll first start by establishing a notification client which will
	// send us notifications upon detected changes in the channel graph.
	req := &lnrpc.GraphTopologySubscription{}
	ctx, cancelFunc := context.WithCancel(ctxb)
	topologyClient, err := node.SubscribeChannelGraph(ctx, req)
	require.NoError(t.t, err, "unable to create topology client")

	// We'll launch a goroutine that will be responsible for proxying all
	// notifications recv'd from the client into the channel below.
	errChan := make(chan error, 1)
	quit := make(chan struct{})
	graphUpdates := make(chan *lnrpc.GraphTopologyUpdate, 20)
	go func() {
		for {
			defer cancelFunc()

			select {
			case <-quit:
				return
			default:
				graphUpdate, err := topologyClient.Recv()
				select {
				case <-quit:
					return
				default:
				}

				if err == io.EOF {
					return
				} else if err != nil {
					select {
					case errChan <- err:
					case <-quit:
					}
					return
				}

				select {
				case graphUpdates <- graphUpdate:
				case <-quit:
					return
				}
			}
		}
	}()

	return graphSubscription{
		updateChan: graphUpdates,
		errChan:    errChan,
		quit:       quit,
	}
}