SIMD-0079: Allow commission decrease at any time during an epoch

proposals/0079-allow_commission_decrease_at_any_time.md

@@ -0,0 +1,81 @@
+---
+simd: '0079'
+title: Allow Commission Decrease at Any Time
+authors:
+  - Bryan Ischo ([email protected])
+category: Standard
+type: Core
+status: Draft
+created: 2023-10-26
+feature: https://github.com/solana-labs/solana/issues/29361
+---
+
+## Summary
+
+The commission_updates_only_allowed_in_first_half_of_epoch feature disallows
+commission decrease in the second half of epoch. Given that the purpose of this
+feature was to prevent 'rug pulls' which are accomplished by increasing
+commission at the end of epoch and then decreasing commission at the beginning
+of next epoch, disallowing decreases during the second half of epoch is
+unnecessary.
+
+A feature gate must be added to support this SIMD as all validators' vote
+programs must treat commission change instructions the same or else consensus
+will diverge.
+
+## Motivation
+
+Some validator operators may need to decrease commission in order to satisfy
+their own operational criteria.
+
+As an example, a validator operator may have a policy whereby any error that
+results in reduced stake account rewards for the epoch, will result in the
+operator choosing to reduce commission to 0% for that epoch to ensure that
+stake accounts are not disadvantaged by that error.  Not being allowed to do
+this in the second half of an epoch is a problem because it would prevent that
+commission change until the next epoch, which will not allow this policy to
+take effect for stake accounts which were de-activating during the epoch.
+
+## Alternatives Considered
+
+No alternatives were considered.
+
+## New Terminology
+
+None
+
+## Detailed Design
+
+A feature will be added which, when enabled, must cause all node
+implementations' vote program's set-commission instruction handling to first
+check whether the proposed commission change is a decrease or no change, and if
+so, do not invoke the "only allow commission change in first half of epoch"
+rule.
+
+## Impact
+
+Validators will now be able to decrease commission at any time in the epoch,
+but only increase commission in the first half of epochs (because of the
+commission_updates_only_allowed_in_first_half_of_epoch feature already
+implemented).
+
+## Security Considerations
+
+None
+
+## Drawbacks
+
+It may cause additional confusion to validators who might not understand why
+some types of commission changes succeed only in the first half of epochs while
+others succeed always.
+
+## Backwards Compatibility
+
+This feature requires a feature gate because software which includes the
+implementation will allow certain set-commission transactions to succeed where
+software without the implementation would fail those transactions.  Thus all
+validators must be updated to the new functionality at an epoch boundary so
+that all validators agree on the result of executing those transactions.
+
+When activated, breaks the ability of older Solana node software to verify
+ledgers with this feature.