Merge pull request #7480 from maxwellsayles/fundExpiryOnPending

lnd: compute FundingExpiryBlocks in PendingOpenChannel message

docs/release-notes/release-notes-0.17.0.md

@@ -53,6 +53,11 @@ package](https://github.com/lightningnetwork/lnd/pull/7356)
   a helpful note-to-self containing arbitrary useful information about the
   channel.
 
+* `PendingOpenChannel` now has the field
+  [`funding_expiry_blocks`](https://github.com/lightningnetwork/lnd/pull/7480)
+  that indicates the number of blocks until the funding transaction is
+  considered expired.
+
 * [gRPC keepalive parameters can now be set in the
   configuration](https://github.com/lightningnetwork/lnd/pull/7730). The `lnd`
   configuration settings `grpc.server-ping-time` and `grpc.server-ping-timeout`
@@ -125,6 +130,7 @@ unlock or create.
 * hieblmi
 * Jordi Montes
 * Matt Morehouse
+* Maxwell Sayles
 * Michael Street
 * Oliver Gugger
 * Shaurya Arora

funding/manager.go

@@ -104,10 +104,10 @@ const (
 	// TODO(roasbeef): tune.
 	msgBufferSize = 50
 
-	// maxWaitNumBlocksFundingConf is the maximum number of blocks to wait
+	// MaxWaitNumBlocksFundingConf is the maximum number of blocks to wait
 	// for the funding transaction to be confirmed before forgetting
 	// channels that aren't initiated by us. 2016 blocks is ~2 weeks.
-	maxWaitNumBlocksFundingConf = 2016
+	MaxWaitNumBlocksFundingConf = 2016
 
 	// pendingChansLimit is the maximum number of pending channels that we
 	// can have. After this point, pending channel opens will start to be
@@ -2535,7 +2535,7 @@ func (f *Manager) fundingTimeout(c *channeldb.OpenChannel,
 	pendingID [32]byte) error {
 
 	// We'll get a timeout if the number of blocks mined since the channel
-	// was initiated reaches maxWaitNumBlocksFundingConf and we are not the
+	// was initiated reaches MaxWaitNumBlocksFundingConf and we are not the
 	// channel initiator.
 	localBalance := c.LocalCommitment.LocalBalance.ToSatoshis()
 	closeInfo := &channeldb.ChannelCloseSummary{
@@ -2597,7 +2597,7 @@ func (f *Manager) fundingTimeout(c *channeldb.OpenChannel,
 
 // waitForFundingWithTimeout is a wrapper around waitForFundingConfirmation and
 // waitForTimeout that will return ErrConfirmationTimeout if we are not the
-// channel initiator and the maxWaitNumBlocksFundingConf has passed from the
+// channel initiator and the MaxWaitNumBlocksFundingConf has passed from the
 // funding broadcast height. In case of confirmation, the short channel ID of
 // the channel and the funding transaction will be returned.
 func (f *Manager) waitForFundingWithTimeout(
@@ -2754,7 +2754,7 @@ func (f *Manager) waitForFundingConfirmation(
 	}
 }
 
-// waitForTimeout will close the timeout channel if maxWaitNumBlocksFundingConf
+// waitForTimeout will close the timeout channel if MaxWaitNumBlocksFundingConf
 // has passed from the broadcast height of the given channel. In case of error,
 // the error is sent on timeoutChan. The wait can be canceled by closing the
 // cancelChan.
@@ -2777,7 +2777,7 @@ func (f *Manager) waitForTimeout(completeChan *channeldb.OpenChannel,
 
 	// On block maxHeight we will cancel the funding confirmation wait.
 	broadcastHeight := completeChan.BroadcastHeight()
-	maxHeight := broadcastHeight + maxWaitNumBlocksFundingConf
+	maxHeight := broadcastHeight + MaxWaitNumBlocksFundingConf
 	for {
 		select {
 		case epoch, ok := <-epochClient.Epochs:
@@ -2793,7 +2793,7 @@ func (f *Manager) waitForTimeout(completeChan *channeldb.OpenChannel,
 				log.Warnf("Waited for %v blocks without "+
 					"seeing funding transaction confirmed,"+
 					" cancelling.",
-					maxWaitNumBlocksFundingConf)
+					MaxWaitNumBlocksFundingConf)
 
 				// Notify the caller of the timeout.
 				close(timeoutChan)

funding/manager_test.go

@@ -2192,14 +2192,15 @@ func TestFundingManagerFundingTimeout(t *testing.T) {
 	// We expect Bob to forget the channel after 2016 blocks (2 weeks), so
 	// mine 2016-1, and check that it is still pending.
 	bob.mockNotifier.epochChan <- &chainntnfs.BlockEpoch{
-		Height: fundingBroadcastHeight + maxWaitNumBlocksFundingConf - 1,
+		Height: fundingBroadcastHeight +
+			MaxWaitNumBlocksFundingConf - 1,
 	}
 
 	// Bob should still be waiting for the channel to open.
 	assertNumPendingChannelsRemains(t, bob, 1)
 
 	bob.mockNotifier.epochChan <- &chainntnfs.BlockEpoch{
-		Height: fundingBroadcastHeight + maxWaitNumBlocksFundingConf,
+		Height: fundingBroadcastHeight + MaxWaitNumBlocksFundingConf,
 	}
 
 	// Bob should have sent an Error message to Alice.
@@ -2245,14 +2246,16 @@ func TestFundingManagerFundingNotTimeoutInitiator(t *testing.T) {
 		t.Fatalf("alice did not publish funding tx")
 	}
 
-	// Increase the height to 1 minus the maxWaitNumBlocksFundingConf
+	// Increase the height to 1 minus the MaxWaitNumBlocksFundingConf
 	// height.
 	alice.mockNotifier.epochChan <- &chainntnfs.BlockEpoch{
-		Height: fundingBroadcastHeight + maxWaitNumBlocksFundingConf - 1,
+		Height: fundingBroadcastHeight +
+			MaxWaitNumBlocksFundingConf - 1,
 	}
 
 	bob.mockNotifier.epochChan <- &chainntnfs.BlockEpoch{
-		Height: fundingBroadcastHeight + maxWaitNumBlocksFundingConf - 1,
+		Height: fundingBroadcastHeight +
+			MaxWaitNumBlocksFundingConf - 1,
 	}
 
 	// Assert both and Alice and Bob still have 1 pending channels.
@@ -2260,13 +2263,13 @@ func TestFundingManagerFundingNotTimeoutInitiator(t *testing.T) {
 
 	assertNumPendingChannelsRemains(t, bob, 1)
 
-	// Increase both Alice and Bob to maxWaitNumBlocksFundingConf height.
+	// Increase both Alice and Bob to MaxWaitNumBlocksFundingConf height.
 	alice.mockNotifier.epochChan <- &chainntnfs.BlockEpoch{
-		Height: fundingBroadcastHeight + maxWaitNumBlocksFundingConf,
+		Height: fundingBroadcastHeight + MaxWaitNumBlocksFundingConf,
 	}
 
 	bob.mockNotifier.epochChan <- &chainntnfs.BlockEpoch{
-		Height: fundingBroadcastHeight + maxWaitNumBlocksFundingConf,
+		Height: fundingBroadcastHeight + MaxWaitNumBlocksFundingConf,
 	}
 
 	// Since Alice was the initiator, the channel should not have timed out.

itest/list_on_test.go

@@ -57,6 +57,10 @@ var allTestCases = []*lntest.TestCase{
 		Name:     "sphinx replay persistence",
 		TestFunc: testSphinxReplayPersistence,
 	},
+	{
+		Name:     "funding expiry blocks on pending",
+		TestFunc: testFundingExpiryBlocksOnPending,
+	},
 	{
 		Name:     "list channels",
 		TestFunc: testListChannels,

itest/lnd_open_channel_test.go

@@ -621,3 +621,34 @@ func verifyCloseUpdate(chanUpdate *lnrpc.ChannelEventUpdate,
 
 	return nil
 }
+
+// testFundingExpiryBlocksOnPending checks that after an OpenChannel, and
+// before the funding transaction is confirmed, that the FundingExpiryBlocks
+// field of a PendingChannels decreases.
+func testFundingExpiryBlocksOnPending(ht *lntest.HarnessTest) {
+	alice, bob := ht.Alice, ht.Bob
+	param := lntest.OpenChannelParams{Amt: 100000}
+	update := ht.OpenChannelAssertPending(alice, bob, param)
+
+	// At this point, the channel's funding transaction will have been
+	// broadcast, but not confirmed. Alice and Bob's nodes should reflect
+	// this when queried via RPC. FundingExpiryBlock should decrease
+	// as blocks are mined, until the channel is confirmed. Empty blocks
+	// won't confirm the funding transaction, so let's mine a few empty
+	// blocks and verify the value of FundingExpiryBlock at each step.
+	const numEmptyBlocks = 3
+	for i := int32(0); i < numEmptyBlocks; i++ {
+		expectedVal := funding.MaxWaitNumBlocksFundingConf - i
+		pending := ht.AssertNumPendingOpenChannels(alice, 1)
+		require.Equal(ht, expectedVal, pending[0].FundingExpiryBlocks)
+		pending = ht.AssertNumPendingOpenChannels(bob, 1)
+		require.Equal(ht, expectedVal, pending[0].FundingExpiryBlocks)
+		ht.MineEmptyBlocks(1)
+	}
+
+	// Mine 1 block to confirm the funding transaction, and then close the
+	// channel.
+	ht.MineBlocksAndAssertNumTxes(1, 1)
+	chanPoint := lntest.ChanPointFromPendingUpdate(update)
+	ht.CloseChannel(alice, chanPoint)
+}

lnrpc/lightning.proto

@@ -2581,6 +2581,17 @@ message PendingChannelsResponse {
 
         // Previously used for confirmation_height. Do not reuse.
         reserved 2;
+
+        // The number of blocks until the funding transaction is considered
+        // expired. If this value gets close to zero, there is a risk that the
+        // channel funding will be canceled by the channel responder. The
+        // channel should be fee bumped using CPFP (see walletrpc.BumpFee) to
+        // ensure that the channel confirms in time. Otherwise a force-close
+        // will be necessary if the channel confirms after the funding
+        // transaction expires. A negative value means the channel responder has
+        // very likely canceled the funding and the channel will never become
+        // fully operational.
+        int32 funding_expiry_blocks = 3;
     }
 
     message WaitingCloseChannel {

lnrpc/lightning.swagger.json

@@ -3052,6 +3052,11 @@
           "type": "string",
           "format": "int64",
           "description": "The required number of satoshis per kilo-weight that the requester will\npay at all times, for both the funding transaction and commitment\ntransaction. This value can later be updated once the channel is open."
+        },
+        "funding_expiry_blocks": {
+          "type": "integer",
+          "format": "int32",
+          "description": "The number of blocks until the funding transaction is considered\nexpired. If this value gets close to zero, there is a risk that the\nchannel funding will be canceled by the channel responder. The\nchannel should be fee bumped using CPFP (see walletrpc.BumpFee) to\nensure that the channel confirms in time. Otherwise a force-close\nwill be necessary if the channel confirms after the funding\ntransaction expires. A negative value means the channel responder has\nvery likely canceled the funding and the channel will never become\nfully operational."
         }
       }
     },

rpcserver.go

@@ -3373,6 +3373,11 @@ func (r *rpcServer) fetchPendingOpenChannels() (pendingOpenChannels, error) {
 		return nil, err
 	}
 
+	_, currentHeight, err := r.server.cc.ChainIO.GetBestBlock()
+	if err != nil {
+		return nil, err
+	}
+
 	result := make(pendingOpenChannels, len(channels))
 	for i, pendingChan := range channels {
 		pub := pendingChan.IdentityPub.SerializeCompressed()
@@ -3389,6 +3394,12 @@ func (r *rpcServer) fetchPendingOpenChannels() (pendingOpenChannels, error) {
 		commitBaseWeight := blockchain.GetTransactionWeight(utx)
 		commitWeight := commitBaseWeight + input.WitnessCommitmentTxWeight
 
+		// FundingExpiryBlocks is the distance from the current block
+		// height to the broadcast height + MaxWaitNumBlocksFundingConf.
+		maxFundingHeight := funding.MaxWaitNumBlocksFundingConf +
+			pendingChan.BroadcastHeight()
+		fundingExpiryBlocks := int32(maxFundingHeight) - currentHeight
+
 		result[i] = &lnrpc.PendingChannelsResponse_PendingOpenChannel{
 			Channel: &lnrpc.PendingChannelsResponse_PendingChannel{
 				RemoteNodePub:        hex.EncodeToString(pub),
@@ -3402,9 +3413,10 @@ func (r *rpcServer) fetchPendingOpenChannels() (pendingOpenChannels, error) {
 				CommitmentType:       rpcCommitmentType(pendingChan.ChanType),
 				Private:              isPrivate(pendingChan),
 			},
-			CommitWeight: commitWeight,
-			CommitFee:    int64(localCommitment.CommitFee),
-			FeePerKw:     int64(localCommitment.FeePerKw),
+			CommitWeight:        commitWeight,
+			CommitFee:           int64(localCommitment.CommitFee),
+			FeePerKw:            int64(localCommitment.FeePerKw),
+			FundingExpiryBlocks: fundingExpiryBlocks,
 			// TODO(roasbeef): need to track confirmation height
 		}
 	}