rules: allow non-present channels in restriction

[bitromortac]

The channel-restriction rule previously failed if any channel in its deny list wasn't currently open. A routine channel closure could block a request with invalid channel ID. This change removes that strict check to ensure the firewall remains resilient to channel changes. It is fine to remove the check, because we can't operate on closed channels anyhow.

[gemini-code-assist]

Summary of Changes

Hello @bitromortac, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request modifies the channel restriction logic to enhance its resilience against dynamic channel states. It specifically removes a strict check that previously required all channels in a deny list to be currently open, preventing unnecessary failures when channels are closed. This ensures the firewall remains operational and robust to routine channel changes without compromising security, as operations on closed channels are inherently impossible.

Highlights

• Channel Restriction Logic: The strict validation for channel presence within the channel-restriction rule has been removed. Previously, the rule would fail if any channel in its deny list was not currently open, leading to "invalid channel ID" errors. This change allows the rule to proceed even if a channel is closed.
• Error Handling: The explicit fmt.Errorf("invalid channel ID") return when a channel ID was not found during map updates has been removed, as the presence check is no longer performed.

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[gemini-code-assist]

Code Review

This pull request modifies the channel-restriction rule to be more resilient to channel closures. By removing the strict check that required a restricted channel to be open, the firewall can now handle deny lists containing closed or non-existent channels without failing. This is a good improvement for operational stability. The code change is clean and also improves variable scoping. I've noted one potential performance side-effect of this change with a suggestion for how to mitigate it.

[bitromortac]

/gemini review

[gemini-code-assist]

Code Review

This pull request modifies the channel restriction rule to allow non-present channels in the deny list. The changes include adding a checkedIDs map to track channel IDs that have been checked, updating the maybeUpdateChannelMaps function to handle a list of channel IDs, and modifying the checkers function to clear the negative cache and return an error if a channel ID is not found and has been checked. This ensures that the firewall remains resilient to channel changes and that the next request will trigger a fresh sync.

I am having trouble creating individual review comments. Click here to see my feedback.

rules/channel_restrictions.go (137-144)

This logic checks if any of the channel IDs need a sync. If one ID needs a sync, needsSync is set to true and the loop breaks. This is good. However, the mutex is unlocked before calling LND, which means another goroutine could modify chanIDToPoint or checkedIDs before LND returns the channel list. This could lead to a race condition where the same channel ID is checked multiple times, or a channel ID is missed entirely.

c.mu.Lock()
		var needsSync bool
		for _, id := range chanIDs {
			_, known := c.chanIDToPoint[id]
			if !known && !c.checkedIDs[id] {
				needsSync = true
				break
			}
		}

rules/channel_restrictions.go (75-78)

The original code iterated through each chanID in channels.DenyList and called maybeUpdateChannelMaps individually. This could lead to multiple calls to LND to fetch the list of open channels if multiple chanIDs are unknown. It's more efficient to update channel maps once for the entire deny list.

err := c.maybeUpdateChannelMaps(ctx, cfg, chanID)
		if err != nil {
			return nil, err
		}

rules/channel_restrictions.go (131-133)

The description of the function maybeUpdateChannelMaps is not accurate anymore. It should reflect that the function now accepts a list of channel IDs and updates the maps if any of them are not found or have not been checked previously.

// iff any of the channels given by the caller are not found in the current
// map set and have not been checked previously.

rules/channel_restrictions.go (162-169)

The code iterates through the channels returned by LND and updates the chanPointToID and chanIDToPoint maps. However, there's no check to see if the channel already exists in the maps. This could lead to unnecessary updates and potential performance issues.

	for _, channel := range chans {
		c.chanPointToID[channel.ChannelPoint] = channel.ChannelID
		c.chanIDToPoint[channel.ChannelID] = channel.ChannelPoint
	}

rules/channel_restrictions.go (328-334)

If hasCheckedIDs returns true, the code clears the checkedIDs map and returns an error, prompting the user to retry the request. This could lead to a retry loop if the channel is still not found in LND's list of open channels. Consider adding a delay or a maximum number of retries to prevent the loop from running indefinitely.

					return fmt.Errorf("unknown " +
							"channel point, " +
							"please retry the " +
							"request")

[ViktorT-11]

@claude review

[claude]

Claude encountered an error —— View job

Command failed: git fetch origin --depth=20 2601-closed-channels-restriction

---

I'll analyze this and get back to you.

[ViktorT-11]

I think this looks good, despite this code being quite complex and hard to follow fully. Leaving one comment regarding locking of the mutex.

[bitromortac]

@claude review

[claude]

Claude encountered an error —— View job

Command failed: git fetch origin --depth=20 2601-closed-channels-restriction

---

I'll analyze this and get back to you.

[ViktorT-11]

Thanks for the changes, I think that definitely makes things simpler to reason about :)! I think this looks good after all the linter issues have been addressed.

[ViktorT-11]

uTACK LGTM

[bitromortac]

/gemini review

[gemini-code-assist]

Code Review

This pull request improves the resilience of the channel-restriction rule by allowing it to handle cases where channels in the deny list are not currently open. The changes are well-implemented, introducing a caching mechanism (checkedIDs) and a retry logic to gracefully handle unknown channels without failing initialization. The core logic in maybeUpdateChannelMaps and the new getChannelIDWithRetryCheck function is sound and robust. The accompanying new test, TestChannelRestrictResilience, is very thorough and covers the complex interaction of states well. The refactoring of tests to use testify/mock is also a good improvement. Overall, this is a high-quality change that effectively addresses the stated problem.

[bitromortac]

Claude encountered an error —— View job

Command failed: git fetch origin --depth=20 2601-closed-channels-restriction

I'll analyze this and get back to you.

Concerning this, it will be fixed by
anthropics/claude-code-action#851

[bitromortac]

will fix this in with the next push