htlcswitch: within link, with each new block, check to see if commit fee should change

In this commit we add a new case to the main select statement within a
channel link. This select statement will serve as a Sipping Bird which
will check the network fee rate (as returned by the fee estimator) and
compare that to the fee on the commitment transaction. Using the
shouldAdjustCommitFee function, we determine if we should update the
commitment fee. If so, then we’ll send an UpdateFee message and also
trigger a new commitment update.

We also add a new unit test: TestChannelLinkUpdateCommitFee to ensure
that we update the fee accordingly if the fee increases or decreases by
a large portion.

htlcswitch/test_utils.go

@@ -365,6 +365,8 @@ func getChanID(msg lnwire.Message) (lnwire.ChannelID, error) {
 		chanID = msg.ChanID
 	case *lnwire.FundingLocked:
 		chanID = msg.ChanID
+	case *lnwire.UpdateFee:
+		chanID = msg.ChanID
 	default:
 		return chanID, fmt.Errorf("unknown type: %T", msg)
 	}
@@ -426,13 +428,20 @@ func generateRoute(hops ...ForwardingInfo) ([lnwire.OnionPacketSize]byte, error)
 type threeHopNetwork struct {
 	aliceServer      *mockServer
 	aliceChannelLink *channelLink
+	aliceBlockEpoch  chan *chainntnfs.BlockEpoch
+
+	firstBobChannelLink *channelLink
+	bobFirstBlockEpoch  chan *chainntnfs.BlockEpoch
 
-	firstBobChannelLink  *channelLink
 	bobServer            *mockServer
 	secondBobChannelLink *channelLink
+	bobSecondBlockEpoch  chan *chainntnfs.BlockEpoch
 
 	carolChannelLink *channelLink
 	carolServer      *mockServer
+	carolBlockEpoch  chan *chainntnfs.BlockEpoch
+
+	feeEstimator *mockFeeEstimator
 
 	globalPolicy ForwardingPolicy
 }
@@ -698,21 +707,29 @@ func newThreeHopNetwork(t testing.TB, aliceChannel, firstBobChannel,
 	bobServer := newMockServer(t, "bob")
 	carolServer := newMockServer(t, "carol")
 
-	// Create mock decoder instead of sphinx one in order to mock the
-	// route which htlc should follow.
+	// Create mock decoder instead of sphinx one in order to mock the route
+	// which htlc should follow.
 	decoder := &mockIteratorDecoder{}
 
-	globalEpoch := &chainntnfs.BlockEpochEvent{
-		Epochs: make(chan *chainntnfs.BlockEpoch),
-		Cancel: func() {
-		},
+	feeEstimator := &mockFeeEstimator{
+		byteFeeIn:   make(chan btcutil.Amount),
+		weightFeeIn: make(chan btcutil.Amount),
+		quit:        make(chan struct{}),
 	}
+
 	globalPolicy := ForwardingPolicy{
 		MinHTLC:       lnwire.NewMSatFromSatoshis(5),
 		BaseFee:       lnwire.NewMSatFromSatoshis(1),
 		TimeLockDelta: 6,
 	}
 	obfuscator := newMockObfuscator()
+
+	aliceEpochChan := make(chan *chainntnfs.BlockEpoch)
+	aliceEpoch := &chainntnfs.BlockEpochEvent{
+		Epochs: aliceEpochChan,
+		Cancel: func() {
+		},
+	}
 	aliceChannelLink := NewChannelLink(
 		ChannelLinkConfig{
 			FwrdingPolicy:     globalPolicy,
@@ -725,7 +742,8 @@ func newThreeHopNetwork(t testing.TB, aliceChannel, firstBobChannel,
 			},
 			GetLastChannelUpdate: mockGetChanUpdateMessage,
 			Registry:             aliceServer.registry,
-			BlockEpochs:          globalEpoch,
+			BlockEpochs:          aliceEpoch,
+			FeeEstimator:         feeEstimator,
 			SyncStates:           true,
 		},
 		aliceChannel,
@@ -735,6 +753,12 @@ func newThreeHopNetwork(t testing.TB, aliceChannel, firstBobChannel,
 		t.Fatalf("unable to add alice channel link: %v", err)
 	}
 
+	bobFirstEpochChan := make(chan *chainntnfs.BlockEpoch)
+	bobFirstEpoch := &chainntnfs.BlockEpochEvent{
+		Epochs: bobFirstEpochChan,
+		Cancel: func() {
+		},
+	}
 	firstBobChannelLink := NewChannelLink(
 		ChannelLinkConfig{
 			FwrdingPolicy:     globalPolicy,
@@ -747,7 +771,8 @@ func newThreeHopNetwork(t testing.TB, aliceChannel, firstBobChannel,
 			},
 			GetLastChannelUpdate: mockGetChanUpdateMessage,
 			Registry:             bobServer.registry,
-			BlockEpochs:          globalEpoch,
+			BlockEpochs:          bobFirstEpoch,
+			FeeEstimator:         feeEstimator,
 			SyncStates:           true,
 		},
 		firstBobChannel,
@@ -757,6 +782,12 @@ func newThreeHopNetwork(t testing.TB, aliceChannel, firstBobChannel,
 		t.Fatalf("unable to add first bob channel link: %v", err)
 	}
 
+	bobSecondEpochChan := make(chan *chainntnfs.BlockEpoch)
+	bobSecondEpoch := &chainntnfs.BlockEpochEvent{
+		Epochs: bobSecondEpochChan,
+		Cancel: func() {
+		},
+	}
 	secondBobChannelLink := NewChannelLink(
 		ChannelLinkConfig{
 			FwrdingPolicy:     globalPolicy,
@@ -769,7 +800,8 @@ func newThreeHopNetwork(t testing.TB, aliceChannel, firstBobChannel,
 			},
 			GetLastChannelUpdate: mockGetChanUpdateMessage,
 			Registry:             bobServer.registry,
-			BlockEpochs:          globalEpoch,
+			BlockEpochs:          bobSecondEpoch,
+			FeeEstimator:         feeEstimator,
 			SyncStates:           true,
 		},
 		secondBobChannel,
@@ -779,6 +811,12 @@ func newThreeHopNetwork(t testing.TB, aliceChannel, firstBobChannel,
 		t.Fatalf("unable to add second bob channel link: %v", err)
 	}
 
+	carolBlockEpoch := make(chan *chainntnfs.BlockEpoch)
+	carolEpoch := &chainntnfs.BlockEpochEvent{
+		Epochs: bobSecondEpochChan,
+		Cancel: func() {
+		},
+	}
 	carolChannelLink := NewChannelLink(
 		ChannelLinkConfig{
 			FwrdingPolicy:     globalPolicy,
@@ -791,7 +829,8 @@ func newThreeHopNetwork(t testing.TB, aliceChannel, firstBobChannel,
 			},
 			GetLastChannelUpdate: mockGetChanUpdateMessage,
 			Registry:             carolServer.registry,
-			BlockEpochs:          globalEpoch,
+			BlockEpochs:          carolEpoch,
+			FeeEstimator:         feeEstimator,
 			SyncStates:           true,
 		},
 		carolChannel,
@@ -802,14 +841,22 @@ func newThreeHopNetwork(t testing.TB, aliceChannel, firstBobChannel,
 	}
 
 	return &threeHopNetwork{
-		aliceServer:          aliceServer,
-		aliceChannelLink:     aliceChannelLink.(*channelLink),
-		firstBobChannelLink:  firstBobChannelLink.(*channelLink),
+		aliceServer:      aliceServer,
+		aliceChannelLink: aliceChannelLink.(*channelLink),
+		aliceBlockEpoch:  aliceEpochChan,
+
+		firstBobChannelLink: firstBobChannelLink.(*channelLink),
+		bobFirstBlockEpoch:  bobFirstEpochChan,
+
 		bobServer:            bobServer,
 		secondBobChannelLink: secondBobChannelLink.(*channelLink),
-		carolChannelLink:     carolChannelLink.(*channelLink),
-		carolServer:          carolServer,
+		bobSecondBlockEpoch:  bobSecondEpochChan,
 
+		carolChannelLink: carolChannelLink.(*channelLink),
+		carolServer:      carolServer,
+		carolBlockEpoch:  carolBlockEpoch,
+
+		feeEstimator: feeEstimator,
 		globalPolicy: globalPolicy,
 	}
 }