channeldb: let AddrsForNode indicate if the node was found or not

Before this commit, the `(channeldb.DB).AddrsForNode` method treats the
results from the channel db and the graph db slightly differently. It
errors out if the channel db is unaware of the node in question but does
not error out if the graph is unaware of the node. So this commit
changes the logic slightly so that a "node-unknown" error from either
backing source is not seen as an error.

chanbackup/backup.go

@@ -34,10 +34,13 @@ func assembleChanBackup(addrSource channeldb.AddrSource,
 
 	// First, we'll query the channel source to obtain all the addresses
 	// that are associated with the peer for this channel.
-	nodeAddrs, err := addrSource.AddrsForNode(openChan.IdentityPub)
+	known, nodeAddrs, err := addrSource.AddrsForNode(openChan.IdentityPub)
 	if err != nil {
 		return nil, err
 	}
+	if !known {
+		return nil, fmt.Errorf("node unknown by address source")
+	}
 
 	single := NewSingle(openChan, nodeAddrs)
 

chanbackup/backup_test.go

@@ -62,20 +62,19 @@ func (m *mockChannelSource) addAddrsForNode(nodePub *btcec.PublicKey, addrs []ne
 	m.addrs[nodeKey] = addrs
 }
 
-func (m *mockChannelSource) AddrsForNode(nodePub *btcec.PublicKey) ([]net.Addr, error) {
+func (m *mockChannelSource) AddrsForNode(nodePub *btcec.PublicKey) (bool,
+	[]net.Addr, error) {
+
 	if m.failQuery {
-		return nil, fmt.Errorf("fail")
+		return false, nil, fmt.Errorf("fail")
 	}
 
 	var nodeKey [33]byte
 	copy(nodeKey[:], nodePub.SerializeCompressed())
 
 	addrs, ok := m.addrs[nodeKey]
-	if !ok {
-		return nil, fmt.Errorf("can't find addr")
-	}
 
-	return addrs, nil
+	return ok, addrs, nil
 }
 
 // TestFetchBackupForChan tests that we're able to construct a single channel

channel_notifier.go

@@ -45,7 +45,7 @@ func (c *channelNotifier) SubscribeChans(startingChans map[wire.OutPoint]struct{
 	// chanUpdates channel to inform subscribers about new pending or
 	// confirmed channels.
 	sendChanOpenUpdate := func(newOrPendingChan *channeldb.OpenChannel) {
-		nodeAddrs, err := c.addrs.AddrsForNode(
+		_, nodeAddrs, err := c.addrs.AddrsForNode(
 			newOrPendingChan.IdentityPub,
 		)
 		if err != nil {

channeldb/addr_source.go

@@ -1,6 +1,7 @@
 package channeldb
 
 import (
+	"errors"
 	"net"
 
 	"github.com/btcsuite/btcd/btcec/v2"
@@ -10,8 +11,9 @@ import (
 // node. It may combine the results of multiple address sources.
 type AddrSource interface {
 	// AddrsForNode returns all known addresses for the target node public
-	// key.
-	AddrsForNode(nodePub *btcec.PublicKey) ([]net.Addr, error)
+	// key. The returned boolean must indicate if the given node is unknown
+	// to the backing source.
+	AddrsForNode(nodePub *btcec.PublicKey) (bool, []net.Addr, error)
 }
 
 // multiAddrSource is an implementation of AddrSource which gathers all the
@@ -31,22 +33,35 @@ func NewMultiAddrSource(sources ...AddrSource) AddrSource {
 }
 
 // AddrsForNode returns all known addresses for the target node public key. It
-// queries all the address sources provided and de-duplicates the results.
+// queries all the address sources provided and de-duplicates the results. The
+// returned boolean is false only if none of the backing sources know of the
+// node.
 //
 // NOTE: this implements the AddrSource interface.
-func (c *multiAddrSource) AddrsForNode(nodePub *btcec.PublicKey) ([]net.Addr,
-	error) {
+func (c *multiAddrSource) AddrsForNode(nodePub *btcec.PublicKey) (bool,
+	[]net.Addr, error) {
+
+	if len(c.sources) == 0 {
+		return false, nil, errors.New("no address sources")
+	}
 
 	// The multiple address sources will likely contain duplicate addresses,
 	// so we use a map here to de-dup them.
 	dedupedAddrs := make(map[string]net.Addr)
 
+	// known will be set to true if any backing source is aware of the node.
+	var known bool
+
 	// Iterate over all the address sources and query each one for the
 	// addresses it has for the node in question.
 	for _, src := range c.sources {
-		addrs, err := src.AddrsForNode(nodePub)
+		isKnown, addrs, err := src.AddrsForNode(nodePub)
 		if err != nil {
-			return nil, err
+			return false, nil, err
+		}
+
+		if isKnown {
+			known = true
 		}
 
 		for _, addr := range addrs {
@@ -60,7 +75,7 @@ func (c *multiAddrSource) AddrsForNode(nodePub *btcec.PublicKey) ([]net.Addr,
 		addrs = append(addrs, addr)
 	}
 
-	return addrs, nil
+	return known, addrs, nil
 }
 
 // A compile-time check to ensure that multiAddrSource implements the AddrSource

channeldb/addr_source_test.go

@@ -36,11 +36,12 @@ func TestMultiAddrSource(t *testing.T) {
 
 		// Let source 1 know of 2 addresses (addr 1 and 2) for node 1.
 		src1.On("AddrsForNode", pk1).Return(
-			[]net.Addr{addr1, addr2}, nil,
+			true, []net.Addr{addr1, addr2}, nil,
 		).Once()
 
 		// Let source 2 know of 2 addresses (addr 2 and 3) for node 1.
 		src2.On("AddrsForNode", pk1).Return(
+			true, []net.Addr{addr2, addr3}, nil,
 			[]net.Addr{addr2, addr3}, nil,
 		).Once()
 
@@ -50,8 +51,9 @@ func TestMultiAddrSource(t *testing.T) {
 
 		// Query it for the addresses known for node 1. The results
 		// should contain addr 1, 2 and 3.
-		addrs, err := multiSrc.AddrsForNode(pk1)
+		known, addrs, err := multiSrc.AddrsForNode(pk1)
 		require.NoError(t, err)
+		require.True(t, known)
 		require.ElementsMatch(t, addrs, []net.Addr{addr1, addr2, addr3})
 	})
 
@@ -69,21 +71,49 @@ func TestMultiAddrSource(t *testing.T) {
 
 		// Let source 1 know of address 1 for node 1.
 		src1.On("AddrsForNode", pk1).Return(
-			[]net.Addr{addr1}, nil,
+			true, []net.Addr{addr1}, nil,
 		).Once()
-		src2.On("AddrsForNode", pk1).Return(nil, nil).Once()
+		src2.On("AddrsForNode", pk1).Return(false, nil, nil).Once()
 
 		// Create a multi-addr source that consists of both source 1
 		// and 2.
 		multiSrc := NewMultiAddrSource(src1, src2)
 
 		// Query it for the addresses known for node 1. The results
 		// should contain addr 1.
-		addrs, err := multiSrc.AddrsForNode(pk1)
+		known, addrs, err := multiSrc.AddrsForNode(pk1)
 		require.NoError(t, err)
+		require.True(t, known)
 		require.ElementsMatch(t, addrs, []net.Addr{addr1})
 	})
 
+	t.Run("unknown address", func(t *testing.T) {
+		t.Parallel()
+
+		var (
+			src1 = newMockAddrSource(t)
+			src2 = newMockAddrSource(t)
+		)
+		t.Cleanup(func() {
+			src1.AssertExpectations(t)
+			src2.AssertExpectations(t)
+		})
+
+		// Create a multi-addr source that consists of both source 1
+		// and 2. Neither source known of node 1.
+		multiSrc := NewMultiAddrSource(src1, src2)
+
+		src1.On("AddrsForNode", pk1).Return(false, nil, nil).Once()
+		src2.On("AddrsForNode", pk1).Return(false, nil, nil).Once()
+
+		// Query it for the addresses known for node 1. It should return
+		// false to indicate that the node is unknown to all backing
+		// sources.
+		known, addrs, err := multiSrc.AddrsForNode(pk1)
+		require.NoError(t, err)
+		require.False(t, known)
+		require.Empty(t, addrs)
+	})
 }
 
 type mockAddrSource struct {
@@ -97,18 +127,18 @@ func newMockAddrSource(t *testing.T) *mockAddrSource {
 	return &mockAddrSource{t: t}
 }
 
-func (m *mockAddrSource) AddrsForNode(pub *btcec.PublicKey) ([]net.Addr,
+func (m *mockAddrSource) AddrsForNode(pub *btcec.PublicKey) (bool, []net.Addr,
 	error) {
 
 	args := m.Called(pub)
-	if args.Get(0) == nil {
-		return nil, args.Error(1)
+	if args.Get(1) == nil {
+		return args.Bool(0), nil, args.Error(2)
 	}
 
-	addrs, ok := args.Get(0).([]net.Addr)
+	addrs, ok := args.Get(1).([]net.Addr)
 	require.True(m.t, ok)
 
-	return addrs, args.Error(1)
+	return args.Bool(0), addrs, args.Error(2)
 }
 
 func newTestPubKey(t *testing.T) *btcec.PublicKey {

channeldb/db.go

@@ -1345,46 +1345,62 @@ func (c *ChannelStateDB) RestoreChannelShells(channelShells ...*ChannelShell) er
 
 // AddrsForNode consults the graph and channel database for all addresses known
 // to the passed node public key.
-func (d *DB) AddrsForNode(nodePub *btcec.PublicKey) ([]net.Addr,
-	error) {
+func (d *DB) AddrsForNode(nodePub *btcec.PublicKey) (bool, []net.Addr, error) {
+	var (
+		// addrs holds the collection of deduplicated addresses we know
+		// of for the node.
+		addrs = make(map[string]net.Addr)
+
+		// known keeps track of if any of the backing sources know of
+		// this node.
+		known bool
+	)
 
+	// First, query the channel DB for its known addresses.
 	linkNode, err := d.channelStateDB.linkNodeDB.FetchLinkNode(nodePub)
-	if err != nil {
-		return nil, err
+	switch {
+	// If we get back a ErrNodeNotFound error, then this just means that the
+	// channel DB does not know of the error, but we don't error out here
+	// because we still want to check the graph db.
+	case err != nil && !errors.Is(err, ErrNodeNotFound):
+		return false, nil, err
+
+	// A nil error means the node is known.
+	case err == nil:
+		known = true
+		for _, addr := range linkNode.Addresses {
+			addrs[addr.String()] = addr
+		}
 	}
 
 	// We'll also query the graph for this peer to see if they have any
 	// addresses that we don't currently have stored within the link node
 	// database.
 	pubKey, err := route.NewVertexFromBytes(nodePub.SerializeCompressed())
 	if err != nil {
-		return nil, err
+		return false, nil, err
 	}
 	graphNode, err := d.graph.FetchLightningNode(pubKey)
-	if err != nil && err != graphdb.ErrGraphNodeNotFound {
-		return nil, err
-	} else if err == graphdb.ErrGraphNodeNotFound {
-		// If the node isn't found, then that's OK, as we still have the
-		// link node data. But any other error needs to be returned.
-		graphNode = &graphdb.LightningNode{}
+	switch {
+	// We don't consider it an error if the graph is unaware of the node.
+	case err != nil && !errors.Is(err, graphdb.ErrGraphNodeNotFound):
+		return false, nil, err
+
+	// If we do find the node, we add its addresses to our deduplicated set.
+	case err == nil:
+		known = true
+		for _, addr := range graphNode.Addresses {
+			addrs[addr.String()] = addr
+		}
 	}
 
-	// Now that we have both sources of addrs for this node, we'll use a
-	// map to de-duplicate any addresses between the two sources, and
-	// produce a final list of the combined addrs.
-	addrs := make(map[string]net.Addr)
-	for _, addr := range linkNode.Addresses {
-		addrs[addr.String()] = addr
-	}
-	for _, addr := range graphNode.Addresses {
-		addrs[addr.String()] = addr
-	}
+	// Convert the deduplicated set into a list.
 	dedupedAddrs := make([]net.Addr, 0, len(addrs))
 	for _, addr := range addrs {
 		dedupedAddrs = append(dedupedAddrs, addr)
 	}
 
-	return dedupedAddrs, nil
+	return known, dedupedAddrs, nil
 }
 
 // AbandonChannel attempts to remove the target channel from the open channel

channeldb/db_test.go

@@ -219,7 +219,7 @@ func TestAddrsForNode(t *testing.T) {
 
 	// Now that we've created a link node, as well as a vertex for the
 	// node, we'll query for all its addresses.
-	nodeAddrs, err := fullDB.AddrsForNode(nodePub)
+	_, nodeAddrs, err := fullDB.AddrsForNode(nodePub)
 	require.NoError(t, err, "unable to obtain node addrs")
 
 	expectedAddrs := make(map[string]struct{})