Ensure ChannelMonitorUpdates are ordered with full monitor writes
#3196
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When we update a channel, then while connecting a block persist a full `ChannelMonitor` prior to persisting the `ChannelMonitorUpdate`, users can end up seeing a full `ChannelMonitor` with a given `latest_update_id` prior to seeing the `ChannelMonitorUpdate` with the same `update_id`. This could cause users to have a full `ChannelMonitor` on disk as well as a `ChannelMonitorUpdate` which was already applied. While this isn't an issue for the LDK-provided update-based `Persist`, its somewhat surprising for users so we avoid it.
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Additional details and impacted files@@ Coverage Diff @@
## main #3196 +/- ##
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- Coverage 89.78% 89.74% -0.04%
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Files 121 121
Lines 100932 100933 +1
Branches 100932 100933 +1
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tnull
approved these changes
Jul 22, 2024
| /// update_persisted_channel, the user returns a | ||
| /// Note that this lock must be held from [`ChannelMonitor::update_monitor`] through to | ||
| /// [`Persist::update_persisted_channel`] to prevent a race where we call | ||
| /// [`Persist::update_persisted_channel`], the user returns a | ||
| /// [`ChannelMonitorUpdateStatus::InProgress`], and then calls channel_monitor_updated |
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nit: Since you're already here, mind ticking/linkng channel_monitor_updated / Vec as well?
| /// persist a full [`ChannelMonitor`] prior to persisting the [`ChannelMonitorUpdate`]. This | ||
| /// could cause users to have a full [`ChannelMonitor`] on disk as well as a | ||
| /// [`ChannelMonitorUpdate`] which was already applied. While this isn't an issue for the | ||
| /// LDK-provided update-based [`Persist`], its somewhat surprising for users so we avoid it. |
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Suggested change
| /// LDK-provided update-based [`Persist`], its somewhat surprising for users so we avoid it. | |
| /// LDK-provided update-based [`Persist`], it is somewhat surprising for users so we avoid it. |
|
Going ahead and land this, nits could still be addressed in a follow up. |
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When we update a channel, then while connecting a block persist a full
ChannelMonitorprior to persisting theChannelMonitorUpdate, users can end up seeing a fullChannelMonitorwith a givenlatest_update_idprior to seeing theChannelMonitorUpdatewith the sameupdate_id. This could cause users to have a fullChannelMonitoron disk as well as aChannelMonitorUpdatewhich was already applied. While this isn't an issue for the LDK-provided update-basedPersist, its somewhat surprising for users so we avoid it.I fought for a while with actually changing the locking structure to enforce this, but it ended up breaking the
LockedChannelMonitorstuff so I gave up.