Implement accepting dual-funded channels without contributing #3137

dunxen · 2024-06-20T11:02:30Z

We split this out from #2302 for easier review and to address the common non-public API parts of the V2 channel establishment implementation.

This will allow the holder to be an acceptor, but not initiator of V2 channels. We also don't expose an API for contributing to an inbound channel.

The functionality to initiate V2 channels and fund inbound channels forms part of #2302.

codecov-commenter · 2024-06-24T17:04:11Z

Codecov Report

Attention: Patch coverage is 62.30159% with 570 lines in your changes missing coverage. Please review.

Project coverage is 89.19%. Comparing base (0db051b) to head (67e0c12).

Files with missing lines	Patch %	Lines
lightning/src/ln/channelmanager.rs	58.92%	235 Missing and 18 partials ⚠️
lightning/src/ln/channel.rs	69.46%	154 Missing and 17 partials ⚠️
lightning/src/ln/interactivetxs.rs	51.81%	142 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3137      +/-   ##
==========================================
- Coverage   89.58%   89.19%   -0.40%     
==========================================
  Files         127      127              
  Lines      103534   104949    +1415     
  Branches   103534   104949    +1415     
==========================================
+ Hits        92750    93608     +858     
- Misses       8080     8600     +520     
- Partials     2704     2741      +37

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optout21

Looks great, mostly localized code improvements suggested.

lightning/src/ln/channel.rs

lightning/src/ln/channelmanager.rs

lightning/src/ln/mod.rs

optout21 · 2024-06-26T12:42:52Z

As I see, the dual_funding cfg flag has been removed (not a problem)

optout21 · 2024-06-26T12:43:36Z

Looks to me that #2989 is in fact included in this PR (good!)

lightning/src/events/mod.rs

TheBlueMatt

Some initial comments, sorry this took so long to get back to.

lightning/src/events/mod.rs

lightning/src/ln/channel.rs

lightning/src/ln/channelmanager.rs

lightning/src/ln/channel.rs

lightning/src/ln/channelmanager.rs

TheBlueMatt · 2024-07-08T02:06:29Z

lightning/src/ln/channelmanager.rs

+
+						if chan.interactive_tx_signing_session.is_some() {
+							let monitor = try_chan_phase_entry!(self,
+								chan.commitment_signed_initial_v2(&msg, best_block, &self.signer_provider, &&logger), chan_phase_entry);


Ugh...So the spec changed the definition of commitment_signed to now also include the initial funding commitment tx signing? Even though it implies other things inside the interactive state machine? Is it too late to change this? This seems nuts.

Does this mean that we should support adding HTLCs prior to the initial commitment transaction?

The previous things it implies should really be looked at in the spec and changed there. We don't want to support adding HTLCs prior to initial commitment. So I really need to investigate what is going on with the spec and what might need to be fixed there.

TheBlueMatt · 2024-07-08T02:07:19Z

lightning/src/ln/channelmanager.rs

+						if chan.interactive_tx_signing_session.is_some() {
+							let monitor = try_chan_phase_entry!(self,
+								chan.commitment_signed_initial_v2(&msg, best_block, &self.signer_provider, &&logger), chan_phase_entry);
+							if let Ok(persist_status) = self.chain_monitor.watch_channel(chan.context.get_funding_txo().unwrap(), monitor) {


If the persist status is pending we need to handle the later stuff in monitor_updating_restored. Really the whole contents of the block here should be in monitor_updating_restored.

lightning/src/ln/channel.rs

dunxen

Thanks @TheBlueMatt, for review and some good points raised. I'll address these ASAP ❤️

dunxen · 2024-07-10T16:06:44Z

Still working on remaining initial feedback.

TheBlueMatt · 2024-07-15T15:51:54Z

No rush, let me know when you want another pass.

dunxen · 2024-10-04T14:43:54Z

Rebased and working through drying up and continuing to address: #3137 (comment)

TheBlueMatt · 2024-10-07T13:40:20Z

LMK when you want another round of review here. I think it was mostly there so kinda waiting for you to tell me you've DRY'd things up and will take a look.

dunxen · 2024-10-08T12:18:37Z

DRY'd up new initial commitment in latest push. Now moving over some tests from #2302 and modifying them to have manual V2 open channel messages so we can at least test them here.

TheBlueMatt · 2024-10-08T15:22:23Z

lightning/src/ln/channel.rs

+	fn context(&self) -> &ChannelContext<SP>;
+
+	fn initial_commitment_signed<L: Deref>(
+		&mut self, holder_commitment_tx: HolderCommitmentTransaction,


We should be able to shift more code here. eg assert_no_commitment_advancement() is shared across both places. The checking logic in check_funding_created_signature is shared in both sides (its broken out in the funding_created handler so that we can reset the state if it fails, but there's not really a strong reason to do that, we always FC the channel if we fail anyway, but we should still reset the funding_outpoint to None if we fail but the common code can check that case and do so). The call to .validate_holder_commitment is shared. There may be more too.

Ok yeah I was a bit too prudent in sharing the code but there are still some obvious pieces like you pointed out. Will push them up in the existing DRY commit and a new commit with tests.

dunxen · 2024-10-10T13:13:45Z

Pushed the DRYing up. Migrating the appropriate tests from 2302 is taking some time as more manual helper methods are needed. Almost there, though.

jkczyz

Some comments based on our offline discussion. Will take a closer look at your recent changes.

jkczyz · 2024-10-10T15:44:31Z

lightning/src/ln/channel.rs

+	pub interactive_tx_constructor: Option<InteractiveTxConstructor>,
+	pub interactive_tx_signing_session: Option<InteractiveTxSigningSession>,


Are these mutually exclusive? Actually, when would we have an InteractiveTxSigningSession when in ChannelPhase::Funded?

Sorry, that should have said InteractiveTxConstructor when in ChannelPhase::Funded.

jkczyz · 2024-10-10T15:52:48Z

lightning/src/ln/channel.rs

+			Ok(tx_constructor) => {
+				channel.set_interactive_tx_constructor(tx_constructor);
+			},


Could we construct InteractiveTxConstructor before InboundV2Channel such that we can simply include the former when constructing the latter rather than needing a mutator?

jkczyz · 2024-10-10T16:04:56Z

lightning/src/ln/channelmanager.rs

+					ChannelPhase::Funded(chan) => &mut chan.interactive_tx_constructor,
+					_ => try_chan_phase_entry!(self, Err(ChannelError::Close(
+						(
+							"Got an unexpected tx_signatures message".into(),


Should this say tx_abort message?

lightning/src/ln/channel.rs

TheBlueMatt · 2024-10-15T16:53:30Z

lightning/src/ln/channel.rs

+		if self.commitment_secrets.get_min_seen_secret() != (1 << 48) ||
+				self.cur_counterparty_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER ||
+				self.holder_commitment_point.transaction_number() != INITIAL_COMMITMENT_NUMBER {
+			panic!("Should not have advanced channel commitment tx numbers prior to funding_created");


Since we're moving this, let's make it a debug_assert!(false, ...)

TheBlueMatt · 2024-10-15T17:04:31Z

lightning/src/ln/channel.rs

+	// If we've sent `commtiment_signed` for an interactive transaction construction,
+	// but have not received `tx_signatures` we MUST set `next_funding_txid` to the
+	// txid of that interactive transaction, else we MUST NOT set it.
+	next_funding_txid: Option<Txid>,


Can you elaborate more in the comment on what issue(s) this addresses? Does this need a persistence of some kind to make it safe?

TheBlueMatt · 2024-10-15T17:05:58Z

lightning/src/ln/channelmanager.rs

+		initiator_input_value_satoshis: u64,
+	}
+
+	// TODO(dual_funding): Use real node and API for creating V2 channels as initiator when available,


bleh, if possible can we avoid adding more test code to channelmanager.rs...that file is huge (or do we need too many variables directly from ChannelManager that aren't pub here)?

I'd recommend the functional_tests.rs or new functional_tests_dual_funding.rs

functional_tests.rs is also kinda huge. Ideally we keep our test files way smaller than most of them are :(

TheBlueMatt · 2024-10-15T20:47:36Z

lightning/src/ln/channelmanager.rs

+				temporary_channel_id.clone()));
+		}
+
+		// Version-specific checks and logic


Most of the code in both sides of this branch is the same, can we DRY it up more?

TheBlueMatt · 2024-10-15T20:50:13Z

lightning/src/ln/interactivetxs.rs

-	) -> Result<(Self, Option<InteractiveTxMessageSend>), AbortReason>
+	/// If the holder is the initiator, they need to send the first message which is a `TxAddInput`
+	/// message.
+	pub fn new<ES: Deref>(args: InteractiveTxConstructorArgs<ES>) -> Result<Self, AbortReason>


Can most of the changes in here be split into separate commit(s) so they can be described in commit messages?

TheBlueMatt · 2024-10-15T20:56:22Z

lightning/src/ln/channel.rs

+
+				// TODO(dual_funding): Check all sigs are SIGHASH_ALL.
+
+				// TODO(dual_funding): I don't see how we're going to be able to ensure witness-standardness


Yea, in general I think we aren't gonna bother, at least not for some time. We should carefully document when we add local-funding logic that the counterparty can add inputs which will prevent the funding tx from confirming, and we make no attempt to prevent that. We should also document this in the open channel logic now (and in release notes added in this PR since its a major change).

TheBlueMatt · 2024-10-15T21:00:17Z

lightning/src/ln/channelmanager.rs

+						msg,
+					});
+				}
+				Ok(())


Should we close the channel here?

TheBlueMatt · 2024-10-15T21:04:15Z

lightning/src/ln/interactivetxs.rs

+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub(crate) struct InteractiveTxSigningSession {


Same here, can this go in a separate commit? Could also use some documentation.

TheBlueMatt · 2024-10-15T21:04:56Z

Git history is weird here looks like some commits from upstream got cherry-picked, can just rebase to fix it.

dunxen · 2024-10-16T10:34:31Z

Git history is weird here looks like some commits from upstream got cherry-picked, can just rebase to fix it.

Yeah, I see now. Fixing.

Will address outstanding feedback from today.

We'll only gate public API related to contributing toward an inbound or opening a dual funded channel.

Here we add the `interactive_tx_constructor` field to the `Channel`, `OutboundV2Channel`, and `InboundV2Channel` structs.

…nnel::funding_signed`

dunxen added the Dual-funding label Jun 20, 2024

dunxen force-pushed the 2024-06-non-public-API-v2-channels branch 3 times, most recently from b981cd7 to 0caf60e Compare June 20, 2024 16:14

dunxen marked this pull request as ready for review June 20, 2024 16:27

dunxen mentioned this pull request Jun 20, 2024

Implement V2 channel establishment #2302

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dunxen force-pushed the 2024-06-non-public-API-v2-channels branch from 0caf60e to 44821af Compare June 24, 2024 16:55

optout21 requested changes Jun 26, 2024

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optout21 mentioned this pull request Jun 27, 2024

Interactive TX negotiation tracks shared outputs #2989

Merged

dunxen force-pushed the 2024-06-non-public-API-v2-channels branch 4 times, most recently from 0db700b to 7dceedd Compare July 3, 2024 09:44

dunxen requested review from optout21 and TheBlueMatt and removed request for optout21 July 3, 2024 09:51

optout21 previously approved these changes Jul 3, 2024

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dunxen requested a review from jkczyz July 4, 2024 15:02

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dunxen force-pushed the 2024-06-non-public-API-v2-channels branch from 7dceedd to 64c35f4 Compare July 10, 2024 16:05

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dunxen added 9 commits October 16, 2024 12:36

Add dual-funding spec links

327dc68

Remove dual_funding cfg attributes

5b88011

We'll only gate public API related to contributing toward an inbound or opening a dual funded channel.

Add interactive tx constructor to all V2-related channel structs

92bc86c

Here we add the `interactive_tx_constructor` field to the `Channel`, `OutboundV2Channel`, and `InboundV2Channel` structs.

Implement support for accepting V2 channels

24df286

DRY up code in InboundV1Channel::funding_created and `OutboundV1Cha…

ec51a72

…nnel::funding_signed`

Handle initial commitment_signed for V2 channels

fd2cc18

Handle re-establishment next_funding_txid

593ca96

Add option_dual_fund feature

6bf97fb

Temporarily allow some unused dual-funding code

3b0b55e

dunxen force-pushed the 2024-06-non-public-API-v2-channels branch from 494413c to 009512f Compare October 16, 2024 10:36

Add manual testing for accepting dual-funded channels

67e0c12

dunxen force-pushed the 2024-06-non-public-API-v2-channels branch from 009512f to 67e0c12 Compare October 16, 2024 13:42

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Implement accepting dual-funded channels without contributing #3137

Implement accepting dual-funded channels without contributing #3137

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		pub interactive_tx_constructor: Option<InteractiveTxConstructor>,
		pub interactive_tx_signing_session: Option<InteractiveTxSigningSession>,


		// TODO(dual_funding): Check all sigs are SIGHASH_ALL.

		// TODO(dual_funding): I don't see how we're going to be able to ensure witness-standardness

Implement accepting dual-funded channels without contributing #3137

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