[Splicing] Preserve funding_transaction for the later lifecycle of the channel, simple solution

[optout21]

Fixes #3300

In splicing, the funding transaction (not just the ID) is needed during splice negotiation.
Funding transaction is kept in field ChannelContext.funding_transaction.
However, the way it is currently used is that it is cleared when the tx is broadcast, and this fact is used in some logic.

This change:

• does not clear ChannelContext.funding_transaction when tx is broadcast, but it's preserved (it's never reset)
• adjust on test case (close_on_unfunded_channel)

Note that in some cases the funding transaction may get broadcasted more than once, which is a change in behavior.

Alternative is to preserve behavior, with some extra field, #3317 .

[TheBlueMatt]

We shouldn't keep broadcasting forever, but I think we can trivially solve that by just checking if the funding tx has confirmed before broadcasting?

[jkczyz]

We shouldn't keep broadcasting forever, but I think we can trivially solve that by just checking if the funding tx has confirmed before broadcasting?

Is that what is checked immediately below where the funding tx was previously taken?

rust-lightning/lightning/src/ln/channel.rs

Lines 5492 to 5496 in ee23649

	// That said, if the funding transaction is already confirmed (ie we're active with a
	// minimum_depth over 0) don't bother re-broadcasting the confirmed funding tx.
	if matches!(self.context.channel_state, ChannelState::ChannelReady(_)) && self.context.minimum_depth != Some(0) {
	funding_broadcastable = None;
	}

Or are there other places we'd need to worry about?

[TheBlueMatt]

Is that what is checked immediately below where the funding tx was previously taken?

Not quite, that will keep broadcasting forever if the channel is 0conf or keep broadcasting after the funding is confirmed at minimum_depth - 1 confirmations, which is a bit weird.

[optout21]

Not quite, that will keep broadcasting forever if the channel is 0conf or keep broadcasting after the funding is confirmed at minimum_depth - 1 confirmations, which is a bit weird.

Indeed, once the funding transaction is confirmed, it makes no sense to rebroadcast, funding_tx_confirmation_height is not checked here.

[TheBlueMatt]

I think with just that change I'd be happy with this PR :)

[coderabbitai]

---

Thank you for using CodeRabbit. We offer it for free to the OSS community and would appreciate your support in helping us grow. If you find it useful, would you consider giving us a shout-out on your favorite social media?

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

🪧 Tips

Chat

There are 3 ways to chat with CodeRabbit:

• Review comments: Directly reply to a review comment made by CodeRabbit. Example:
  • I pushed a fix in commit <commit_id>, please review it.
  • Generate unit testing code for this file.
  • Open a follow-up GitHub issue for this discussion.
• Files and specific lines of code (under the "Files changed" tab): Tag @coderabbitai in a new review comment at the desired location with your query. Examples:
  • @coderabbitai generate unit testing code for this file.
  • @coderabbitai modularize this function.
• PR comments: Tag @coderabbitai in a new PR comment to ask questions about the PR branch. For the best results, please provide a very specific query, as very limited context is provided in this mode. Examples:
  • @coderabbitai gather interesting stats about this repository and render them as a table. Additionally, render a pie chart showing the language distribution in the codebase.
  • @coderabbitai read src/utils.ts and generate unit testing code.
  • @coderabbitai read the files in the src/scheduler package and generate a class diagram using mermaid and a README in the markdown format.
  • @coderabbitai help me debug CodeRabbit configuration file.

Note: Be mindful of the bot's finite context window. It's strongly recommended to break down tasks such as reading entire modules into smaller chunks. For a focused discussion, use review comments to chat about specific files and their changes, instead of using the PR comments.

CodeRabbit Commands (Invoked using PR comments)

• @coderabbitai pause to pause the reviews on a PR.
• @coderabbitai resume to resume the paused reviews.
• @coderabbitai review to trigger an incremental review. This is useful when automatic reviews are disabled for the repository.
• @coderabbitai full review to do a full review from scratch and review all the files again.
• @coderabbitai summary to regenerate the summary of the PR.
• @coderabbitai resolve resolve all the CodeRabbit review comments.
• @coderabbitai configuration to show the current CodeRabbit configuration for the repository.
• @coderabbitai help to get help.

Other keywords and placeholders

• Add @coderabbitai ignore anywhere in the PR description to prevent this PR from being reviewed.
• Add @coderabbitai summary to generate the high-level summary at a specific location in the PR description.
• Add @coderabbitai anywhere in the PR title to generate the title automatically.

CodeRabbit Configuration File (.coderabbit.yaml)

• You can programmatically configure CodeRabbit by adding a .coderabbit.yaml file to the root of your repository.
• Please see the configuration documentation for more information.
• If your editor has YAML language server enabled, you can add the path at the top of this file to enable auto-completion and validation: # yaml-language-server: $schema=https://coderabbit.ai/integrations/schema.v2.json

Documentation and Community

• Visit our Documentation for detailed information on how to use CodeRabbit.
• Join our Discord Community to get help, request features, and share feedback.
• Follow us on X/Twitter for updates and announcements.

[optout21]

Changed the test for preventing re-broadcast to look whether the funding transaction is confirmed or not (instead of looking at ChannelReady state).
With this, the test updated had to be reverted, the behavior is the same as before.

[optout21]

Addressed @jkczyz 's comments; not yet squashed

[jkczyz]

LGTM. Feel free to squash

[optout21]

Squashed with no changes