[7/?] - funding: update funding manager w/ new musig2+taproot funding flow #7346

Roasbeef · 2023-01-20T04:38:31Z

Change Description

Depends on #7345.

Only the last 6 commits are new.

In this PR, we build on the prior PR that updated the channel state machine to update the funding manager to be aware of the new funding flow.

This flow is identical to the existing flow, but both sides need to exchange local nonces up front, and then signatures sent are now partial signatures instead of regular signatures.

The funding manager also gains some new state of the local nonces it needs to generate in order to send the funding locked message, and also process the funding locked message from the remote party.

In order to allow the funding manger to generate the nonces that need to be applied to each channel, then AddNewChannel method has been modified to accept a set of options that the peer will then use to bind the nonces to a new channel.

We also update the link+peer interaction to know how to initialize the new channel, as well as the extra information that needs to be sent in funding locked and the channel reest message.

As a stop gap before Gossip 1.5, we need to set a new feature bit in the channel announcement itself. Otherwise, the router won't know how to validate the funding script of the newly created channel.

Steps to Test

Steps for reviewers to follow to test the change.

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Testing

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Tests covering the positive and negative (error paths) are included.
Bug fixes contain tests triggering the bug to prevent regressions.

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joostjager · 2023-01-31T16:02:15Z

funding/manager.go

+		log.Debugf("Applying taproot feature bit to "+
+			"ChannelAnnouncement for %v", chanID)
+
+		chanAnn.Features.Set(lnwire.SimpleTaprootChannelsRequired)


Do you expect the same feature bit to be used eventually for public channels?

Should this modify the feature bit dependency mapping to use "INC+" instead of "IN"?

No, this is a temp hack so we're able to signal to the gossiper exactly what type of channel this is. When things get to the router, we'll still verify the channel on-chain (compared the output to the expected script), so we need this in order to signal that this is a different type of channel.

joostjager

Shallow-reviewed all the PRs in the series and overall the addition of simple taproot channels does not look too involved at all! Of course relative to the expectation, because obviously it is still a large diff.

General comments:

Perhaps it is good to make the changes so that taproot channels follow the default flow instead of being the exception. So if !taproot { ... } rather than if taproot { ...}
Related to the first point: would it be feasible to take a more object-oriented approach for adding taproot channels? More grouping of taproot-channel-specific code in a single location and fewer selects on chan type could possibly improve code quality.
For public channels, gossip needs to change. Is there already anything concrete in terms of spec for that? Would be helpful to complete the mental model, even if not implemented.
To reduce complexity, it would be great if all non-taproot channels would just go away 😬

ellemouton

Did first pass - looks good! Sooo cool how the funding manager could be made taproot-chan-ready with such a slim diff 🔥

funding/manager.go

ellemouton · 2023-04-28T09:25:32Z

funding/manager.go

+		if !ok {
+			// If there's no pending nonce for this channel ID,
+			// then we'll generate one now.
+			verNonce, err := lnwallet.NewMusigVerificationNonce(


can use channel.GenMusigNonces() as is done for createFundingLocked

So can't use it here as we don't yet have the full channel state machine created. So instead we need to call the function manually. Also spotted a bug here (will be covered by the eventual itests): it uses the current commitment height, but should actually use the next commitment height. I think @ellemouton ran into this in the past.

funding/manager.go

feature/deps.go

Crypt-iQ · 2023-05-04T15:47:01Z

peer/brontide.go

@@ -2383,14 +2384,17 @@ out:
 					continue
 				}

+				// TODO(roasbeef): don't also need to apply
+				// nonces here? get from chan reest


I think it gets confusing because they may send a channel_ready and channel_reestablish

Goa here is to have the "last" one override the nonce that we'll store for them.

Goal here is to have the "last" one override the nonce that we'll store for them.

I think that means that the channel_ready will override the nonces previously set in channel_reestablish? IMO if channel_reestablish has been exchanged, we should ignore nonces in channel_ready and then we never need to worry about overriding nonces with scid alias rotation

Crypt-iQ · 2023-05-04T16:24:29Z

funding/manager.go

+		log.Debugf("Applying taproot feature bit to "+
+			"ChannelAnnouncement for %v", chanID)
+
+		chanAnn.Features.Set(lnwire.SimpleTaprootChannelsRequired)


Should this modify the feature bit dependency mapping to use "INC+" instead of "IN"?

routing/router.go

htlcswitch/link.go

funding/manager.go

htlcswitch/link.go

positiveblue

First pass done.

The code looks good and the changes are pretty straight forward 🎉

There are some issues to resolve before merging (like make it panic proof). I also did not see any tests in the commits, are they added later in the PR chain?

funding/manager.go

lightninglabs-deploy · 2023-07-17T03:27:24Z

@Roasbeef, remember to re-request review from reviewers when ready

Crypt-iQ

I think that this might be an outdated branch because there are three panics?

msg.LocalNonce in handleFundingOpen
msg.LocalNonce in handleFundingAccept
sig.Nonce in VerifyCommitSig

funding/manager.go

Crypt-iQ · 2023-07-12T16:07:19Z

funding/manager.go

@@ -3517,6 +3674,8 @@ func (f *Manager) handleFundingLocked(peer lnpeer.Peer,
 				return
 			}

+			// TODO(roasbeef): call sendFundingLocked here?
+


think we need to include nonces here. Also think the spec needs to clarify what to do when we receive another FundingLocked that rotates the alias, do we ignore the nonces?

Yes as is we'll ignore the second one (existing logic). We'll use the same nonce each time until the channel state has moved forward one.

funding/manager.go

Crypt-iQ · 2023-07-13T14:52:16Z

peer/brontide.go

@@ -2383,14 +2384,17 @@ out:
 					continue
 				}

+				// TODO(roasbeef): don't also need to apply
+				// nonces here? get from chan reest


I think that means that the channel_ready will override the nonces previously set in channel_reestablish? IMO if channel_reestablish has been exchanged, we should ignore nonces in channel_ready and then we never need to worry about overriding nonces with scid alias rotation

htlcswitch/link.go

contractcourt/chain_watcher.go

funding/manager.go

lnwallet/transactions.go

lnwallet/channel.go

feature/default_sets.go

funding/commitment_type_negotiation.go

funding/manager.go

routing/router.go

htlcswitch/link.go

Roasbeef · 2023-07-24T18:40:39Z

sig.Nonce in VerifyCommitSig

sig.Nonce isn't a pointer here.

ellemouton

LGTM pending resolution on @Crypt-iQ's comment re RegisterSpendNtfn & CI fixes.
Left one comment re allowing unsetting of the new feature bit.

feature/deps.go

funding/commitment_type_negotiation.go

funding/manager.go

Crypt-iQ · 2023-07-25T13:50:29Z

sig.Nonce in VerifyCommitSig

sig.Nonce isn't a pointer here.

if sig is nil then it will be nil-ptr-dereference

… types

yyforyongyu

Think it's very close. Got one question - should we update the commit weight and fee here when calling NewChannelReservation?

yyforyongyu · 2023-07-26T05:40:10Z

funding/manager.go

@@ -1965,6 +2021,20 @@ func (f *Manager) handleFundingAccept(peer lnpeer.Peer,
 		},
 		UpfrontShutdown: msg.UpfrontShutdownScript,
 	}
+
+	if resCtx.reservation.IsTaproot() {


nit: would put this check after L1968 to align with other checks such as if !resCtx.reservation.IsZeroConf() && msg.MinAcceptDepth == 0 { .

yyforyongyu · 2023-07-26T05:56:35Z

funding/manager.go

+		fundingSigned.CommitSig, err = lnwire.NewSigFromSignature(sig)
+		if err != nil {
+			log.Errorf("unable to parse signature: %v", err)
+			f.failFundingFlow(peer, pendingChanID, err)


This is probably a bug, not introduced from this PR tho. At L2320 we already called f.deleteReservationCtx which removes the channel from f.activeReservations. Hence when we call failFundingFlow here, it will error out because f.cancelReservationCtx won't find the reservation.

funding/manager.go

ellemouton · 2023-07-26T07:27:25Z

should we update the commit weight and fee here when calling NewChannelReservation?

I think we can just change that to use the lnwallet.CommitWeight method instead which is updated with a taproot case here

Crypt-iQ

LGTM pending two comments:

[7/?] - funding: update funding manager w/ new musig2+taproot funding flow #7346 (comment)
[7/?] - funding: update funding manager w/ new musig2+taproot funding flow #7346 (review)

…chans

In this commit, we add support for the new musig2 channel funding flow. This flow is identical to the existing flow, but not both sides need to exchange local nonces up front, and then signatures sent are now partial signatures instead of regular signatures. The funding manager also gains some new state of the local nonces it needs to generate in order to send the funding locked message, and also process the funding locked message from the remote party. In order to allow the funding manger to generate the nonces that need to be applied to each channel, then AddNewChannel method has been modified to accept a set of options that the peer will then use to bind the nonces to a new channel.

… channels In this commit, we start to set _internally_ a new feature bit in the channel announcements we generate. As these taproot channels can only be unadvertised, this will never actually leak to the public network. The funding manager will then set this field to allow the router to properly validate these channels.

In this commit, we update the chain watcher to be able to generate the correct pkScript so it can register for confirmation and spend notifications for taproot channels.

This ensures that when loading the channel again after a normal chan reest, we generate the local nonces, which ensures we can then process nonces the remote party sends us in their chan reest message.

This ensures that we end up playing the target output on chain for taproot channels.

Roasbeef · 2023-07-27T00:04:52Z

Pushed up a final set of commits adding unit test coverage for the new funding manager flows, cc @positiveblue

Crypt-iQ · 2023-07-27T10:15:37Z

@ellemouton comment was that channelFeatures.OnlyContains can be called with ZeroConfRequired and ScidAliasRequired, but then hasFeatures doesn't contain ScidAliasOptional. I think that the ZeroConfRequired+ScidAliasRequired case is missing from this PR

Roasbeef added the taproot chans label Jan 20, 2023

Roasbeef mentioned this pull request Jan 20, 2023

[8/?] - lncli+lnrpc: add support for creating unadvertised taproot channels #7347

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saubyk added this to the v0.16.0 milestone Jan 20, 2023

saubyk assigned Roasbeef Jan 26, 2023

joostjager reviewed Jan 31, 2023

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Roasbeef requested review from positiveblue and sputn1ck February 14, 2023 18:35

saubyk modified the milestones: v0.16.0, v0.16.1 Feb 14, 2023

saubyk modified the milestones: v0.16.1, v0.17.0 Mar 13, 2023

Roasbeef changed the base branch from master to simple-taproot-chans-channel-statemachine April 27, 2023 00:10

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feature: add SimpleTaprootChannelsOptional to the set of default chan…

bc65546

… types

Roasbeef force-pushed the simple-taproot-chans-funding-mgr branch 2 times, most recently from 8cfdf30 to a1b6a0d Compare July 26, 2023 00:54

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Crypt-iQ approved these changes Jul 26, 2023

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Roasbeef added 10 commits July 26, 2023 15:46

funding: update explicitNegotiateCommitmentType to recognize taproot …

1804e03

…chans

htlcswitch: add awareness of new partial sig fields and musig2 nonces

b66d538

contractcourt: update chain watcher to understand the taproot pkscript

e46dae5

In this commit, we update the chain watcher to be able to generate the correct pkScript so it can register for confirmation and spend notifications for taproot channels.

lnwallet: generate local nonces if non passed in for taproot chans

3555afb

This ensures that when loading the channel again after a normal chan reest, we generate the local nonces, which ensures we can then process nonces the remote party sends us in their chan reest message.

lnwallet: add extra sanity check in VerifyCommitSig

ed3becb

contractcourt: for taproot channels, wait for conf in closeObserver

b09c3db

This ensures that we end up playing the target output on chain for taproot channels.

lntest: update SingleMockSigner to support musig2

7bca374

funding: add unit tests for reg+zero conf taproot chans

ea25054

Roasbeef force-pushed the simple-taproot-chans-funding-mgr branch from a1b6a0d to ea25054 Compare July 27, 2023 00:04

Roasbeef merged commit dd8820d into lightningnetwork:simple-taproot-chans-staging Jul 27, 2023
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[7/?] - funding: update funding manager w/ new musig2+taproot funding flow #7346

[7/?] - funding: update funding manager w/ new musig2+taproot funding flow #7346

Roasbeef commented Jan 20, 2023

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[7/?] - funding: update funding manager w/ new musig2+taproot funding flow #7346

[7/?] - funding: update funding manager w/ new musig2+taproot funding flow #7346

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Roasbeef commented Jan 20, 2023

Change Description

Steps to Test

Pull Request Checklist

Testing

Code Style and Documentation

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