dex: relax inner guard for withdrawn LP updates #5051
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The DEX engine has an inner guard against invalid state transitions that acts as a last line of defense in case all other validation failed. This inner guard reifies the LP update state-machine, rejecting obviously wrong transitions (e.g, Closed -> Open). Previously, this inner guard defended against updating a withdrawn LP without increasing its sequence number. This is true in the ordinary case when users are driving the state change e.g, by burning/minting a new withdrawn LP. But too limiting in the case when the protocol itself performs an update. This PR: 1. Relax the inner guard 2. Simplifies the reward deposit logic 3. Provides a justification why the inner guard check is triply redundant. The guard is relaxed and removes a third layer of defense, the other two are: 1. The `withdraw_position` entrypoint called by the action handler 2. Check that the transaction value balances (burn, mint inc. seq)
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TalDerei
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| // Ok, you'd think we'd be done here, alas, the [`guard_invalid_transitions`] function | ||
| // will complain if the position has already been withdrawn, but the sequence has not yet been incremented! | ||
| new_state.state = match prev_state.state { | ||
| position::State::Opened => position::State::Opened, | ||
| position::State::Closed => position::State::Closed, | ||
| position::State::Withdrawn { sequence } => position::State::Withdrawn { | ||
| sequence: sequence.saturating_add(1), | ||
| }, | ||
| }; |
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ACK – references #5035 (comment)
hdevalence
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hdevalence
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**Overview** In this PR, we: - Relax the inner guard to allow withdrawn LP updates without `seq+1` - Simplify the reward deposit logic so that it sticks to depositing rewards **Context** Before updating position states, the DEX engine runs an inner guard to defend against ostensibly invalid state transitions (e.g, Closed -> Open). In particular, since there was no mechanism to update an LP without also updating its sequence number, that particular transition was disallowed. This is no longer the case with the implementation of epoch-scoped LQTs. **Other validation** The guard is relaxed and removes a third layer of defense, the other two are: 1. The `withdraw_position` entrypoint called by the action handler 2. Ordinary check that the transaction value balances (burn, mint inc. seq) ## Checklist before requesting a review - [x] I have added guiding text to explain how a reviewer should test these changes. This is tested once we test the end-to-end multi-withdraw mechanism. - [x] If this code contains consensus-breaking changes, I have added the "consensus-breaking" label. Otherwise, I declare my belief that there are not consensus-breaking changes, for the following reason: > LQT target
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Overview
In this PR, we:
seq+1Context
Before updating position states, the DEX engine runs an inner guard to defend against
ostensibly invalid state transitions (e.g, Closed -> Open).
In particular, since there was no mechanism to update an LP without also updating its
sequence number, that particular transition was disallowed. This is no longer the case
with the implementation of epoch-scoped LQTs.
Other validation
The guard is relaxed and removes a third layer of defense, the other two are: 1. The
withdraw_positionentrypoint called by the action handler 2. Ordinary check that thetransaction value balances (burn, mint inc. seq)
Checklist before requesting a review
This is tested once we test the end-to-end multi-withdraw mechanism.
If this code contains consensus-breaking changes, I have added the
"consensus-breaking" label. Otherwise, I declare my belief that there are not
consensus-breaking changes, for the following reason: