Introduce interactive signing state flags for funded states. by dunxen · Pull Request #3637 · lightningdevkit/rust-lightning

dunxen · 2025-03-03T18:50:23Z

This PR includes some deferred follow-ups extracted from #3423 and introduces new state flags to track interactive signing along with persistence of the minimum information needed from a signing session to reconstruct it.

A top-level state flag was avoided so that this work is compatible with splicing as well as V2 channel establishment (dual-funding).

ldk-reviews-bot · 2025-03-03T18:50:25Z

👋 Thanks for assigning @jkczyz as a reviewer!
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TheBlueMatt

Did you want to include test coverage for restarts here?

dunxen · 2025-03-04T15:29:10Z

Did you want to include test coverage for restarts here?

Not yet. Tracked in #3636. Will need to be able to contribute inputs first to test a useful order of message exchange + restart.

codecov · 2025-03-05T10:13:38Z

Codecov Report

Attention: Patch coverage is 64.55026% with 67 lines in your changes missing coverage. Please review.

Project coverage is 90.01%. Comparing base (89f5217) to head (fb00cb6).
Report is 19 commits behind head on main.

Files with missing lines	Patch %	Lines
lightning/src/ln/channel.rs	59.55%	49 Missing and 6 partials ⚠️
lightning/src/ln/interactivetxs.rs	46.66%	8 Missing ⚠️
lightning/src/ln/channelmanager.rs	90.90%	1 Missing and 1 partial ⚠️
lightning/src/ln/dual_funding_tests.rs	87.50%	1 Missing ⚠️
lightning/src/util/ser.rs	85.71%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@ Coverage Diff @@## main #3637 +/- ##
==========================================
+ Coverage 89.37% 90.01% +0.63% 
==========================================
Files 157 157 Lines 124095 129376 +5281 Branches 124095 129376 +5281 ==========================================
+ Hits 110915 116452 +5537 + Misses 10469 10187 -282 - Partials 2711 2737 +26

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wpaulino · 2025-03-05T21:15:29Z

@dunxen re-request when this is ready for review again, feel free to squash as well

ldk-reviews-bot · 2025-03-06T12:44:38Z

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TheBlueMatt · 2025-03-06T23:01:54Z

Taking myself off since @wpaulino and @jkczyz are on this one. Aside from my first comment I don't have any more high-level feedback.

ldk-reviews-bot · 2025-05-12T00:01:19Z

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ldk-reviews-bot · 2025-05-12T08:12:27Z

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jkczyz · 2025-05-12T15:45:21Z

@dunxen Was the latest push just a rebase?

dunxen · 2025-05-12T15:48:24Z

@dunxen Was the latest push just a rebase?

Oh yip.

Sorry, I didn't put a diff-tree showing that.

ldk-reviews-bot · 2025-05-14T08:12:51Z

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dunxen

Changes:

git diff-tree -U1 3c0b810 74139d0
diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs
index 66305c042..e6e9c8f3b 100644
--- a/lightning/src/ln/channel.rs+++ b/lightning/src/ln/channel.rs@@ -5942,6 +5942,6 @@ impl<SP: Deref> FundedChannel<SP> where
{
- if !matches!(self.context.channel_state, ChannelState::FundingNegotiated(flags) if flags.is_interactive_signing()) {+ if !matches!(self.context.channel_state, ChannelState::FundingNegotiated(flags) if flags.is_interactive_signing() && !flags.is_their_tx_signatures_sent()) {
return Err(ChannelError::Close(
(
- "Received initial commitment_signed before funding transaction constructed!".to_owned(),+ "Received initial commitment_signed before funding transaction constructed or after peer's tx_signatures received!".to_owned(),
ClosureReason::HolderForceClosed { broadcasted_latest_txn: Some(false) },
@@ -6615,2 +6615,13 @@ impl<SP: Deref> FundedChannel<SP> where
+ // We need to close the channel if our peer hasn't sent their commitment signed already.+ // Technically we'd wait on having an initial monitor persisted, so we shouldn't be broadcasting+ // the transaction, but this may risk losing funds for a manual broadcast if we continue.+ if !signing_session.has_received_commitment_signed() {+ return Err(ChannelError::Close(+ (+ "Received tx_signatures before initial commitment_signed".to_string(),+ ClosureReason::HolderForceClosed { broadcasted_latest_txn: Some(false) },+ )));+ }+
if msg.witnesses.len() != signing_session.remote_inputs_count() {
@@ -7458,3 +7469,9 @@ impl<SP: Deref> FundedChannel<SP> where
} else {
- return Err(ChannelError::close("Counterparty set `next_funding_txid` at incorrect state".into()));+ // We'll just send a `tx_abort` here if we don't have a signing session for this channel+ // on reestablish and tell our peer to just forget about it.+ // Our peer is doing something strange, but it doesn't warrant closing the channel.+ (None, None, Some(msgs::TxAbort {+ channel_id: self.context.channel_id(),+ data:+ "No active signing session. The associated funding transaction may have already been broadcast.".as_bytes().to_vec() }))
}

ldk-reviews-bot · 2025-05-17T00:00:49Z

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ldk-reviews-bot · 2025-05-17T00:00:52Z

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ldk-reviews-bot · 2025-05-19T00:01:20Z

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ldk-reviews-bot · 2025-05-19T00:01:22Z

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jkczyz

LGTM

Instead of having an explicit `ChannelContext::next_funding_txid` to set and read, we can get this value on the fly when it is appropriate to do so.

This follows the the specification closely in branching without being too verbose, so that it should be easy to follow the logic. See: https://github.com/lightning/bolts/blob/aa5207a/02-peer-protocol.md?plain=1#L2520-L2531

This intoduces the INTERACTIVE_SIGNING, THEIR_TX_SIGNATURES_SENT, and OUR_TX_SIGNATURES_SENT funded state flags. A top-level state flag for INTERACTIVE_SIGNING was avoided so that this work is compatible with splicing as well as V2 channel establishment (dual-funding). This commit also ensures that `ChannelPending` is only emitted after peers exchange `tx_signatures`.

We fully persist `InteractiveTxSigningSession` as it provides the full context of the constructed transaction which is still needed for signing.

When this config field is enabled, the dual_fund feature bit will be set which determines support when receiving `open_channel2` messages.

dunxen · 2025-05-20T19:58:30Z

Sorry, a possibly earlier rebase slipped in with the last change 🤦‍♂️
Meant to rebase my draft PR. But just fixed up #3637 (comment)

ldk-reviews-bot · 2025-05-21T00:01:57Z

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wpaulino

One last comment but it can go in a follow-up

wpaulino · 2025-05-21T20:35:28Z

+ } else {
+ // The `next_funding_txid` does not match the latest interactive funding transaction so we
+ // MUST send tx_abort to let the remote know that they can forget this funding transaction.
+ (None, None, Some(msgs::TxAbort {


Looks like we actually need to close the channel here:
A receiving node: - if next_funding_txid is set: - if it also sets next_funding_txid in its own channel_reestablish, but the values don't match: - MUST send an error and fail the channel.

ldk-reviews-bot · 2025-05-22T19:59:23Z

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dunxen marked this pull request as draft March 3, 2025 18:50

dunxen mentioned this pull request Dec 5, 2024
Dual-funded channels and Splicing Project Tracking #1621
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dunxen force-pushed the 2025-02-interactivesigningstate branch 2 times, most recently from 4c6b6ab to c1f430aCompare March 4, 2025 09:02

dunxen changed the title ~~DRAFT: Introduce interactive signing state flags for funded states.~~Introduce interactive signing state flags for funded states.Mar 4, 2025

dunxen marked this pull request as ready for review March 4, 2025 09:03

dunxen requested review from TheBlueMatt, jkczyz and wpaulino March 4, 2025 09:04

dunxen force-pushed the 2025-02-interactivesigningstate branch from c1f430a to e89ba58Compare March 4, 2025 11:09

TheBlueMatt reviewed Mar 4, 2025
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dunxen force-pushed the 2025-02-interactivesigningstate branch from e89ba58 to 3b2ac55Compare March 5, 2025 10:05

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dunxen force-pushed the 2025-02-interactivesigningstate branch from 5110ecc to 1d96044Compare March 6, 2025 12:43

dunxen requested review from TheBlueMatt and wpaulino March 6, 2025 12:44

dunxen added weekly goal Someone wants to land this this week Dual-funding labels Mar 6, 2025

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dunxen force-pushed the 2025-02-interactivesigningstate branch from 1d96044 to 55e5f6fCompare March 11, 2025 11:42

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dunxen force-pushed the 2025-02-interactivesigningstate branch from 3c0b810 to 74139d0Compare May 14, 2025 12:37

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dunxen requested a review from wpaulino May 14, 2025 12:47

jkczyz previously approved these changes May 19, 2025
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dunxen added 5 commits May 20, 2025 21:40

Get next_funding_txid from the funding_outpoint based on state
c3807d4
Instead of having an explicit `ChannelContext::next_funding_txid` to set and read, we can get this value on the fly when it is appropriate to do so.

Handle receiving channel_reestablish with next_funding_txid
df35ff7
This follows the the specification closely in branching without being too verbose, so that it should be easy to follow the logic. See: https://github.com/lightning/bolts/blob/aa5207a/02-peer-protocol.md?plain=1#L2520-L2531

Persist InteractiveTxSigningSession to resume signing across restarts
9b5d8a3
We fully persist `InteractiveTxSigningSession` as it provides the full context of the constructed transaction which is still needed for signing.

Add enable_dual_funded_channels to UserConfig
b5ac8e8
When this config field is enabled, the dual_fund feature bit will be set which determines support when receiving `open_channel2` messages.

dunxen dismissed jkczyz’s stale review via b5ac8e8May 20, 2025 19:48

dunxen force-pushed the 2025-02-interactivesigningstate branch from 74139d0 to b5ac8e8Compare May 20, 2025 19:48

dunxen requested a review from jkczyz May 20, 2025 19:58

wpaulino approved these changes May 21, 2025
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jkczyz approved these changes May 23, 2025
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jkczyz merged commit 1156efb into lightningdevkit:mainMay 23, 2025

optout21 mentioned this pull request Jun 10, 2025
Add Shared Input support in interactive TX construction #3842
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