lncli: reject negative sat_per_vbyte in close/open channel commands (fixes #9834)

[ThomsenDrake]

Fixes #9834

Problem

The --sat_per_vbyte flag was declared as cli.Int64Flag but read via ctx.Uint64(), causing negative values to wrap to huge positive numbers (e.g., -1 becomes 2^63 - 1). This affects four commands:

• lncli closechannel
• lncli closeallchannels
• lncli openchannel
• lncli batchopenchannel

A user passing --sat_per_vbyte=-1 would get a transaction with an absurdly high fee rate instead of an error.

Fix

Changed cli.Int64Flag → cli.Uint64Flag for sat_per_vbyte in all four commands. The urfave/cli library rejects negative values at parse time when the flag is Uint64, producing a clear error message.

Testing

• Existing unit tests pass (no test changes needed — the flag type change only affects CLI parsing)
• Verified: urfave/cli Uint64Flag rejects negative inputs with "invalid value "-1" for flag -sat_per_vbyte: parse error"

Files Changed

• cmd/commands/cmd_open_channel.go (2 changes: openchannel + batchopenchannel)
• cmd/commands/commands.go (2 changes: closechannel + closeallchannels)

[gemini-code-assist]

Summary of Changes

Hello, 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 addresses a critical issue where negative fee rate inputs for channel operations could lead to unintended and excessively high transaction fees. By correctly typing the sat_per_vbyte flag as an unsigned integer, the system now robustly rejects invalid negative inputs at the command-line parsing stage, enhancing user experience and preventing costly errors during channel opening and closing.

Highlights

• Prevents negative sat_per_vbyte values: The sat_per_vbyte flag, previously an Int64Flag but read as Uint64, caused negative inputs to wrap to extremely large positive numbers, resulting in absurdly high transaction fees for channel operations.
• Improved input validation: The flag type for sat_per_vbyte has been changed from cli.Int64Flag to cli.Uint64Flag in openchannel, batchopenchannel, closechannel, and closeallchannels commands. This leverages urfave/cli's built-in validation to reject negative values at parse time, providing clear error messages.

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[gemini-code-assist]

Code Review

This pull request updates the sat_per_vbyte flag type from cli.Int64Flag to cli.Uint64Flag for the openChannelCommand, batchOpenChannelCommand, closeChannelCommand, and closeAllChannelsCommand. This change correctly represents fee values as unsigned integers. There is no feedback to provide.

[lightninglabs-deploy]

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

[ThomsenDrake]

@saubyk As requested by the CI bot — re-requesting your review on this PR when you have a moment. The change is minimal (Int64Flag → Uint64Flag for fee rate inputs) and addresses issue #9834 which is assigned to you.

Changes:

• openChannelCommand: cli.Int64Flag → cli.Uint64Flag
• batchOpenChannelCommand: cli.Int64Flag → cli.Uint64Flag
• closeChannelCommand: cli.Int64Flag → cli.Uint64Flag
• closeAllChannelsCommand: cli.Int64Flag → cli.Uint64Flag

All existing tests pass. The Gemini Code Assist bot review found no issues.