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funding: skip rescan for already-confirmed zero-conf channels #10459

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funding: skip rescan for already-confirmed zero-conf channels #10459

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5 changes: 5 additions & 0 deletions docs/release-notes/release-notes-0.21.0.md
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Original file line number Diff line number Diff line change
Expand Up @@ -77,6 +77,11 @@

## Performance Improvements

* [Zero-conf channels that are already confirmed no longer trigger historical
chain rescans](https://github.com/lightningnetwork/lnd/pull/10459) from the
broadcast height on restart. This significantly reduces bandwidth usage for
mobile and neutrino clients.

## Deprecations

### ⚠️ **Warning:** The deprecated fee rate option `--sat_per_byte` will be removed in release version **0.22**
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63 changes: 47 additions & 16 deletions funding/manager.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3812,46 +3812,65 @@
if numConfs < 6 {
numConfs = 6
}

txid := completeChan.FundingOutpoint.Hash
log.Debugf("Will announce channel %v after ChannelPoint"+
"(%v) has gotten %d confirmations",
shortChanID.ToUint64(), completeChan.FundingOutpoint,
numConfs)
log.Debugf("Will announce channel %v after "+
"ChannelPoint(%v) has gotten %d confirmations",
shortChanID.ToUint64(),
completeChan.FundingOutpoint, numConfs)

fundingScript, err := MakeFundingScript(completeChan)
if err != nil {
return fmt.Errorf("unable to create funding script "+
"for ChannelPoint(%v): %v",
return fmt.Errorf("unable to create funding "+
"script for ChannelPoint(%v): %v",
completeChan.FundingOutpoint, err)
}

// Register with the ChainNotifier for a notification once the
// funding transaction reaches at least 6 confirmations.
// For zero-conf channels that are already confirmed, use
// the confirmed block height as the height hint instead
// of the broadcast height. This significantly reduces the
// rescan range on restart, which is especially important
// for mobile devices using the neutrino backend where
// historical rescans consume significant bandwidth.
heightHint := completeChan.BroadcastHeight()
if completeChan.IsZeroConf() && completeChan.ZeroConfConfirmed() {

Check failure on line 3836 in funding/manager.go

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confirmedScid := completeChan.ZeroConfRealScid()
heightHint = confirmedScid.BlockHeight

log.Debugf("Using confirmed height %d as hint for "+
"zero-conf ChannelPoint(%v)",
heightHint, completeChan.FundingOutpoint)
}

// Register with the ChainNotifier for a notification
// once the funding transaction reaches at least 6
// confirmations.
confNtfn, err := f.cfg.Notifier.RegisterConfirmationsNtfn(
&txid, fundingScript, numConfs,
completeChan.BroadcastHeight(),
heightHint,
)
if err != nil {
return fmt.Errorf("unable to register for "+
"confirmation of ChannelPoint(%v): %v",
completeChan.FundingOutpoint, err)
}

// Wait until 6 confirmations has been reached or the wallet
// signals a shutdown.
// Wait until 6 confirmations has been reached or the
// wallet signals a shutdown.
select {
case _, ok := <-confNtfn.Confirmed:
if !ok {
return fmt.Errorf("ChainNotifier shutting "+
"down, cannot complete funding flow "+
"for ChannelPoint(%v)",
return fmt.Errorf("ChainNotifier "+
"shutting down, cannot "+
"complete funding flow for "+
"ChannelPoint(%v)",
completeChan.FundingOutpoint)
}
// Fallthrough.

case <-f.quit:
return fmt.Errorf("%v, stopping funding flow for "+
"ChannelPoint(%v)",
return fmt.Errorf("%v, stopping funding flow "+
"for ChannelPoint(%v)",
ErrFundingManagerShuttingDown,
completeChan.FundingOutpoint)
}
Expand Down Expand Up @@ -3920,6 +3939,18 @@
// a zero-conf channel. This will wait for the real confirmation, add the
// confirmed SCID to the router graph, and then announce after six confs.
func (f *Manager) waitForZeroConfChannel(c *channeldb.OpenChannel) error {
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@gemini-code-assist gemini-code-assist bot Dec 21, 2025

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medium

While the logic to skip the rescan for already confirmed zero-conf channels is sound, this bug fix would benefit from an accompanying regression test. A test case could be added to simulate a restart where a zero-conf channel is already confirmed, and then assert that no historical rescan is triggered. This would help prevent future regressions and ensure the long-term stability of this optimization.

// If the zero-conf channel is already confirmed, we can skip the
// historical chain rescan. This is important for mobile devices where
// rescanning from the broadcast height can consume significant
// bandwidth, especially with the neutrino backend.
if c.ZeroConfConfirmed() {
log.Debugf("Zero-conf ChannelPoint(%v) already confirmed "+
"with SCID %v, skipping chain rescan",
c.FundingOutpoint, c.ZeroConfRealScid())

return nil
}

// First we'll check whether the channel is confirmed on-chain. If it
// is already confirmed, the chainntnfs subsystem will return with the
// confirmed tx. Otherwise, we'll wait here until confirmation occurs.
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