routing: add TlvTrafficShaper to bandwidth hints

config_builder.go

@@ -44,6 +44,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnwallet/btcwallet"
 	"github.com/lightningnetwork/lnd/lnwallet/rpcwallet"
 	"github.com/lightningnetwork/lnd/macaroons"
+	"github.com/lightningnetwork/lnd/routing"
 	"github.com/lightningnetwork/lnd/rpcperms"
 	"github.com/lightningnetwork/lnd/signal"
 	"github.com/lightningnetwork/lnd/sqldb"
@@ -157,6 +158,10 @@ type AuxComponents struct {
 	// AuxLeafStore is an optional data source that can be used by custom
 	// channels to fetch+store various data.
 	AuxLeafStore fn.Option[lnwallet.AuxLeafStore]
+
+	// TrafficShaper is an optional traffic shaper that can be used to
+	// control the outgoing channel of a payment.
+	TrafficShaper fn.Option[routing.TlvTrafficShaper]
 }
 
 // DefaultWalletImpl is the default implementation of our normal, btcwallet

htlcswitch/interfaces.go

@@ -12,6 +12,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/record"
+	"github.com/lightningnetwork/lnd/tlv"
 )
 
 // InvoiceDatabase is an interface which represents the persistent subsystem
@@ -271,6 +272,16 @@ type ChannelLink interface {
 	// have buffered messages.
 	AttachMailBox(MailBox)
 
+	// FundingCustomBlob returns the custom funding blob of the channel that
+	// this link is associated with. The funding blob represents static
+	// information about the channel that was created at channel funding
+	// time.
+	FundingCustomBlob() fn.Option[tlv.Blob]
+
+	// CommitmentCustomBlob returns the custom blob of the current local
+	// commitment of the channel that this link is associated with.
+	CommitmentCustomBlob() fn.Option[tlv.Blob]
+
 	// Start/Stop are used to initiate the start/stop of the channel link
 	// functioning.
 	Start() error

htlcswitch/link.go

@@ -3775,3 +3775,16 @@ func (l *channelLink) fail(linkErr LinkFailureError,
 	l.failed = true
 	l.cfg.OnChannelFailure(l.ChanID(), l.ShortChanID(), linkErr)
 }
+
+// FundingCustomBlob returns the custom funding blob of the channel that this
+// link is associated with. The funding blob represents static information about
+// the channel that was created at channel funding time.
+func (l *channelLink) FundingCustomBlob() fn.Option[tlv.Blob] {
+	return l.channel.State().CustomBlob
+}
+
+// CommitmentCustomBlob returns the custom blob of the current local commitment
+// of the channel that this link is associated with.
+func (l *channelLink) CommitmentCustomBlob() fn.Option[tlv.Blob] {
+	return l.channel.LocalCommitmentBlob()
+}

htlcswitch/mock.go

@@ -27,6 +27,7 @@ import (
 	"github.com/lightningnetwork/lnd/channeldb/models"
 	"github.com/lightningnetwork/lnd/clock"
 	"github.com/lightningnetwork/lnd/contractcourt"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/invoices"
 	"github.com/lightningnetwork/lnd/lnpeer"
@@ -35,6 +36,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/ticker"
+	"github.com/lightningnetwork/lnd/tlv"
 )
 
 func isAlias(scid lnwire.ShortChannelID) bool {
@@ -912,6 +914,10 @@ func (f *mockChannelLink) ChannelPoint() wire.OutPoint {
 	return wire.OutPoint{}
 }
 
+func (f *mockChannelLink) ChannelCustomBlob() fn.Option[tlv.Blob] {
+	return fn.Option[tlv.Blob]{}
+}
+
 func (f *mockChannelLink) Stop()                                        {}
 func (f *mockChannelLink) EligibleToForward() bool                      { return f.eligible }
 func (f *mockChannelLink) MayAddOutgoingHtlc(lnwire.MilliSatoshi) error { return nil }
@@ -942,6 +948,14 @@ func (f *mockChannelLink) OnCommitOnce(LinkDirection, func()) {
 	// TODO(proofofkeags): Implement
 }
 
+func (f *mockChannelLink) FundingCustomBlob() fn.Option[tlv.Blob] {
+	return fn.None[tlv.Blob]()
+}
+
+func (f *mockChannelLink) CommitmentCustomBlob() fn.Option[tlv.Blob] {
+	return fn.None[tlv.Blob]()
+}
+
 var _ ChannelLink = (*mockChannelLink)(nil)
 
 func newDB() (*channeldb.DB, func(), error) {

lnwallet/channel.go

@@ -9589,3 +9589,19 @@ func (lc *LightningChannel) MultiSigKeys() (keychain.KeyDescriptor,
 	return lc.channelState.LocalChanCfg.MultiSigKey,
 		lc.channelState.RemoteChanCfg.MultiSigKey
 }
+
+// LocalCommitmentBlob returns the custom blob of the local commitment.
+func (lc *LightningChannel) LocalCommitmentBlob() fn.Option[tlv.Blob] {
+	lc.RLock()
+	defer lc.RUnlock()
+
+	chanState := lc.channelState
+	localBalance := chanState.LocalCommitment.CustomBlob
+
+	return fn.MapOption(func(b tlv.Blob) tlv.Blob {
+		newBlob := make([]byte, len(b))
+		copy(newBlob, b)
+
+		return newBlob
+	})(localBalance)
+}

routing/bandwidth.go

@@ -1,10 +1,15 @@
 package routing
 
 import (
+	"fmt"
+
+	"github.com/btcsuite/btcd/btcutil"
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/htlcswitch"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
+	"github.com/lightningnetwork/lnd/tlv"
 )
 
 // bandwidthHints provides hints about the currently available balance in our
@@ -18,7 +23,39 @@ type bandwidthHints interface {
 	// will be used. If the channel is unavailable, a zero amount is
 	// returned.
 	availableChanBandwidth(channelID uint64,
-		amount lnwire.MilliSatoshi) (lnwire.MilliSatoshi, bool)
+		amount lnwire.MilliSatoshi,
+		htlcBlob fn.Option[tlv.Blob]) (lnwire.MilliSatoshi, bool)
+}
+
+// TlvTrafficShaper is an interface that allows the sender to determine if a
+// payment should be carried by a channel based on the TLV records that may be
+// present in the `update_add_htlc` message or the channel commitment itself.
+type TlvTrafficShaper interface {
+	AuxHtlcModifier
+
+	// HandleTraffic is called in order to check if the channel identified
+	// by the provided channel ID may have external mechanisms that would
+	// allow it to carry out the payment.
+	HandleTraffic(cid lnwire.ShortChannelID,
+		fundingBlob fn.Option[tlv.Blob]) (bool, error)
+
+	// PaymentBandwidth returns the available bandwidth for a custom channel
+	// decided by the given channel aux blob and HTLC blob. A return value
+	// of 0 means there is no bandwidth available. To find out if a channel
+	// is a custom channel that should be handled by the traffic shaper, the
+	// HandleTraffic method should be called first.
+	PaymentBandwidth(htlcBlob,
+		commitmentBlob fn.Option[tlv.Blob]) (lnwire.MilliSatoshi, error)
+}
+
+// AuxHtlcModifier is an interface that allows the sender to modify the outgoing
+// HTLC of a payment by changing the amount or the wire message tlv records.
+type AuxHtlcModifier interface {
+	// ProduceHtlcExtraData is a function that, based on the previous extra
+	// data blob of an HTLC, may produce a different blob or modify the
+	// amount of bitcoin this htlc should carry.
+	ProduceHtlcExtraData(totalAmount lnwire.MilliSatoshi,
+		htlcBlob tlv.Blob) (btcutil.Amount, tlv.Blob, error)
 }
 
 // getLinkQuery is the function signature used to lookup a link.
@@ -29,8 +66,9 @@ type getLinkQuery func(lnwire.ShortChannelID) (
 // uses the link lookup provided to query the link for our latest local channel
 // balances.
 type bandwidthManager struct {
-	getLink    getLinkQuery
-	localChans map[lnwire.ShortChannelID]struct{}
+	getLink       getLinkQuery
+	localChans    map[lnwire.ShortChannelID]struct{}
+	trafficShaper fn.Option[TlvTrafficShaper]
 }
 
 // newBandwidthManager creates a bandwidth manager for the source node provided
@@ -40,11 +78,13 @@ type bandwidthManager struct {
 // allows us to reduce the number of extraneous attempts as we can skip channels
 // that are inactive, or just don't have enough bandwidth to carry the payment.
 func newBandwidthManager(graph routingGraph, sourceNode route.Vertex,
-	linkQuery getLinkQuery) (*bandwidthManager, error) {
+	linkQuery getLinkQuery,
+	trafficShaper fn.Option[TlvTrafficShaper]) (*bandwidthManager, error) {
 
 	manager := &bandwidthManager{
-		getLink:    linkQuery,
-		localChans: make(map[lnwire.ShortChannelID]struct{}),
+		getLink:       linkQuery,
+		localChans:    make(map[lnwire.ShortChannelID]struct{}),
+		trafficShaper: trafficShaper,
 	}
 
 	// First, we'll collect the set of outbound edges from the target
@@ -71,7 +111,8 @@ func newBandwidthManager(graph routingGraph, sourceNode route.Vertex,
 // queried is one of our local channels, so any failure to retrieve the link
 // is interpreted as the link being offline.
 func (b *bandwidthManager) getBandwidth(cid lnwire.ShortChannelID,
-	amount lnwire.MilliSatoshi) lnwire.MilliSatoshi {
+	amount lnwire.MilliSatoshi,
+	htlcBlob fn.Option[tlv.Blob]) lnwire.MilliSatoshi {
 
 	link, err := b.getLink(cid)
 	if err != nil {
@@ -89,30 +130,83 @@ func (b *bandwidthManager) getBandwidth(cid lnwire.ShortChannelID,
 		return 0
 	}
 
-	// If our link isn't currently in a state where it can  add another
-	// outgoing htlc, treat the link as unusable.
+	var (
+		auxBandwidth           lnwire.MilliSatoshi
+		auxBandwidthDetermined bool
+	)
+	err = fn.MapOptionZ(b.trafficShaper, func(ts TlvTrafficShaper) error {
+		fundingBlob := link.FundingCustomBlob()
+		shouldHandle, err := ts.HandleTraffic(cid, fundingBlob)
+		if err != nil {
+			return fmt.Errorf("traffic shaper failed to decide "+
+				"whether to handle traffic: %w", err)
+		}
+
+		log.Debugf("ShortChannelID=%v: external traffic shaper is "+
+			"handling traffic: %v", cid, shouldHandle)
+
+		// If this channel isn't handled by the external traffic shaper,
+		// we'll return early.
+		if !shouldHandle {
+			return nil
+		}
+
+		// Ask for a specific bandwidth to be used for the channel.
+		commitmentBlob := link.CommitmentCustomBlob()
+		auxBandwidth, err = ts.PaymentBandwidth(
+			htlcBlob, commitmentBlob,
+		)
+		if err != nil {
+			return fmt.Errorf("failed to get bandwidth from "+
+				"external traffic shaper: %w", err)
+		}
+
+		log.Debugf("ShortChannelID=%v: external traffic shaper "+
+			"reported available bandwidth: %v", cid, auxBandwidth)
+
+		auxBandwidthDetermined = true
+
+		return nil
+	})
+	if err != nil {
+		log.Errorf("ShortChannelID=%v: failed to get bandwidth from "+
+			"external traffic shaper: %v", cid, err)
+
+		return 0
+	}
+
+	// If our link isn't currently in a state where it can add
+	// another outgoing htlc, treat the link as unusable.
 	if err := link.MayAddOutgoingHtlc(amount); err != nil {
-		log.Warnf("ShortChannelID=%v: cannot add outgoing htlc: %v",
-			cid, err)
+		log.Warnf("ShortChannelID=%v: cannot add outgoing "+
+			"htlc: %v", cid, err)
 		return 0
 	}
 
-	// Otherwise, we'll return the current best estimate for the available
-	// bandwidth for the link.
+	// If the external traffic shaper determined the bandwidth, we'll return
+	// that value, even if it is zero (which would mean no bandwidth is
+	// available on that channel).
+	if auxBandwidthDetermined {
+		return auxBandwidth
+	}
+
+	// Otherwise, we'll return the current best estimate for the
+	// available bandwidth for the link.
 	return link.Bandwidth()
 }
 
 // availableChanBandwidth returns the total available bandwidth for a channel
 // and a bool indicating whether the channel hint was found. If the channel is
 // unavailable, a zero amount is returned.
 func (b *bandwidthManager) availableChanBandwidth(channelID uint64,
-	amount lnwire.MilliSatoshi) (lnwire.MilliSatoshi, bool) {
+	amount lnwire.MilliSatoshi,
+	htlcBlob fn.Option[tlv.Blob]) (lnwire.MilliSatoshi, bool) {
 
 	shortID := lnwire.NewShortChanIDFromInt(channelID)
 	_, ok := b.localChans[shortID]
 	if !ok {
 		return 0, false
 	}
 
-	return b.getBandwidth(shortID, amount), true
+	return b.getBandwidth(shortID, amount, htlcBlob), true
 }

routing/bandwidth_test.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/btcsuite/btcd/btcutil"
 	"github.com/go-errors/errors"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/htlcswitch"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/stretchr/testify/require"
@@ -115,11 +116,13 @@ func TestBandwidthManager(t *testing.T) {
 
 			m, err := newBandwidthManager(
 				g, sourceNode.pubkey, testCase.linkQuery,
+				fn.None[TlvTrafficShaper](),
 			)
 			require.NoError(t, err)
 
 			bandwidth, found := m.availableChanBandwidth(
 				testCase.channelID, 10,
+				fn.None[[]byte](),
 			)
 			require.Equal(t, testCase.expectedBandwidth, bandwidth)
 			require.Equal(t, testCase.expectFound, found)

routing/integrated_routing_context_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/kvdb"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
@@ -24,7 +25,8 @@ type mockBandwidthHints struct {
 }
 
 func (m *mockBandwidthHints) availableChanBandwidth(channelID uint64,
-	_ lnwire.MilliSatoshi) (lnwire.MilliSatoshi, bool) {
+	_ lnwire.MilliSatoshi,
+	htlcBlob fn.Option[[]byte]) (lnwire.MilliSatoshi, bool) {
 
 	if m.hints == nil {
 		return 0, false
@@ -229,6 +231,7 @@ func (c *integratedRoutingContext) testPayment(maxParts uint32,
 		// Find a route.
 		route, err := session.RequestRoute(
 			amtRemaining, lnwire.MaxMilliSatoshi, inFlightHtlcs, 0,
+			nil,
 		)
 		if err != nil {
 			return attempts, err