stake-pool: Fund rent-exemption from reserve in decrease_additional (…

…#5288)

* stake-pool: Fund rent-exemption from reserve in `decrease_additional`

* stake-pool-js: Add reserve stake to "decrease additional"

* Only withdraw required lamports into split destination

* Avoid depleting the reserve

* Use actual lamport number from ephemeral account

* Cargo fmt

* Move error check

stake-pool/js/src/index.ts

@@ -795,6 +795,7 @@ export async function decreaseValidatorStake(
         stakePool: stakePoolAddress,
         staker: stakePool.account.data.staker,
         validatorList: stakePool.account.data.validatorList,
+        reserveStake: stakePool.account.data.reserveStake,
         transientStakeSeed: transientStakeSeed.toNumber(),
         withdrawAuthority,
         validatorStake,

stake-pool/js/src/instructions.ts

@@ -226,6 +226,7 @@ export type DecreaseValidatorStakeParams = {
 };
 
 export interface DecreaseAdditionalValidatorStakeParams extends DecreaseValidatorStakeParams {
+  reserveStake: PublicKey;
   ephemeralStake: PublicKey;
   ephemeralStakeSeed: number;
 }
@@ -612,6 +613,7 @@ export class StakePoolInstruction {
       staker,
       withdrawAuthority,
       validatorList,
+      reserveStake,
       validatorStake,
       transientStake,
       lamports,
@@ -628,6 +630,7 @@ export class StakePoolInstruction {
       { pubkey: staker, isSigner: true, isWritable: false },
       { pubkey: withdrawAuthority, isSigner: false, isWritable: false },
       { pubkey: validatorList, isSigner: false, isWritable: true },
+      { pubkey: reserveStake, isSigner: false, isWritable: true },
       { pubkey: validatorStake, isSigner: false, isWritable: true },
       { pubkey: ephemeralStake, isSigner: false, isWritable: true },
       { pubkey: transientStake, isSigner: false, isWritable: true },

stake-pool/program/src/error.rs

@@ -154,6 +154,9 @@ pub enum StakePoolError {
     /// the rent-exempt reserve for a stake account.
     #[error("ReserveDepleted")]
     ReserveDepleted,
+    /// Missing required sysvar account
+    #[error("Missing required sysvar account")]
+    MissingRequiredSysvar,
 }
 impl From<StakePoolError> for ProgramError {
     fn from(e: StakePoolError) -> Self {

stake-pool/program/src/instruction.rs

@@ -446,24 +446,28 @@ pub enum StakePoolInstruction {
     ///
     /// Works regardless if the transient stake account already exists.
     ///
-    /// Internally, this instruction splits a validator stake account into an
-    /// ephemeral stake account, deactivates it, then merges or splits it into
-    /// the transient stake account delegated to the appropriate validator.
+    /// Internally, this instruction:
+    ///  * withdraws rent-exempt reserve lamports from the reserve into the ephemeral stake
+    ///  * splits a validator stake account into an ephemeral stake account
+    ///  * deactivates the ephemeral account
+    ///  * merges or splits the ephemeral account into the transient stake account
+    ///    delegated to the appropriate validator
     ///
-    ///  The amount of lamports to move must be at least rent-exemption plus
+    ///  The amount of lamports to move must be at least
     /// `max(crate::MINIMUM_ACTIVE_STAKE, solana_program::stake::tools::get_minimum_delegation())`.
     ///
     ///  0. `[]` Stake pool
     ///  1. `[s]` Stake pool staker
     ///  2. `[]` Stake pool withdraw authority
     ///  3. `[w]` Validator list
-    ///  4. `[w]` Canonical stake account to split from
-    ///  5. `[w]` Uninitialized ephemeral stake account to receive stake
-    ///  6. `[w]` Transient stake account
-    ///  7. `[]` Clock sysvar
-    ///  8. '[]' Stake history sysvar
-    ///  9. `[]` System program
-    /// 10. `[]` Stake program
+    ///  4. `[w]` Reserve stake account, to fund rent exempt reserve
+    ///  5. `[w]` Canonical stake account to split from
+    ///  6. `[w]` Uninitialized ephemeral stake account to receive stake
+    ///  7. `[w]` Transient stake account
+    ///  8. `[]` Clock sysvar
+    ///  9. '[]' Stake history sysvar
+    /// 10. `[]` System program
+    /// 11. `[]` Stake program
     DecreaseAdditionalValidatorStake {
         /// amount of lamports to split into the transient stake account
         lamports: u64,
@@ -793,6 +797,7 @@ pub fn decrease_additional_validator_stake(
     staker: &Pubkey,
     stake_pool_withdraw_authority: &Pubkey,
     validator_list: &Pubkey,
+    reserve_stake: &Pubkey,
     validator_stake: &Pubkey,
     ephemeral_stake: &Pubkey,
     transient_stake: &Pubkey,
@@ -805,6 +810,7 @@ pub fn decrease_additional_validator_stake(
         AccountMeta::new_readonly(*staker, true),
         AccountMeta::new_readonly(*stake_pool_withdraw_authority, false),
         AccountMeta::new(*validator_list, false),
+        AccountMeta::new(*reserve_stake, false),
         AccountMeta::new(*validator_stake, false),
         AccountMeta::new(*ephemeral_stake, false),
         AccountMeta::new(*transient_stake, false),
@@ -1211,6 +1217,7 @@ pub fn decrease_additional_validator_stake_with_vote(
         &stake_pool.staker,
         &pool_withdraw_authority,
         &stake_pool.validator_list,
+        &stake_pool.reserve_stake,
         &validator_stake_address,
         &ephemeral_stake_address,
         &transient_stake_address,

stake-pool/program/src/processor.rs

@@ -1241,12 +1241,16 @@ impl Processor {
         lamports: u64,
         transient_stake_seed: u64,
         maybe_ephemeral_stake_seed: Option<u64>,
+        fund_rent_exempt_reserve: bool,
     ) -> ProgramResult {
         let account_info_iter = &mut accounts.iter();
         let stake_pool_info = next_account_info(account_info_iter)?;
         let staker_info = next_account_info(account_info_iter)?;
         let withdraw_authority_info = next_account_info(account_info_iter)?;
         let validator_list_info = next_account_info(account_info_iter)?;
+        let maybe_reserve_stake_info = fund_rent_exempt_reserve
+            .then(|| next_account_info(account_info_iter))
+            .transpose()?;
         let validator_stake_account_info = next_account_info(account_info_iter)?;
         let maybe_ephemeral_stake_account_info = maybe_ephemeral_stake_seed
             .map(|_| next_account_info(account_info_iter))
@@ -1298,6 +1302,10 @@ impl Processor {
             return Err(StakePoolError::InvalidState.into());
         }
 
+        if let Some(reserve_stake_info) = maybe_reserve_stake_info {
+            stake_pool.check_reserve_stake(reserve_stake_info)?;
+        }
+
         let (meta, stake) = get_stake_state(validator_stake_account_info)?;
         let vote_account_address = stake.delegation.voter_pubkey;
 
@@ -1339,10 +1347,10 @@ impl Processor {
         }
 
         let stake_space = std::mem::size_of::<stake::state::StakeState>();
-        let stake_minimum_delegation = stake::tools::get_minimum_delegation()?;
         let stake_rent = rent.minimum_balance(stake_space);
-        let current_minimum_lamports =
-            stake_rent.saturating_add(minimum_delegation(stake_minimum_delegation));
+
+        let stake_minimum_delegation = stake::tools::get_minimum_delegation()?;
+        let current_minimum_lamports = minimum_delegation(stake_minimum_delegation);
         if lamports < current_minimum_lamports {
             msg!(
                 "Need at least {} lamports for transient stake to meet minimum delegation and rent-exempt requirements, {} provided",
@@ -1366,7 +1374,7 @@ impl Processor {
             return Err(ProgramError::InsufficientFunds);
         }
 
-        let source_stake_account_info =
+        let (source_stake_account_info, split_lamports) =
             if let Some((ephemeral_stake_seed, ephemeral_stake_account_info)) =
                 maybe_ephemeral_stake_seed.zip(maybe_ephemeral_stake_account_info)
             {
@@ -1388,6 +1396,30 @@ impl Processor {
                     stake_space,
                 )?;
 
+                // if needed, withdraw rent-exempt reserve for ephemeral account
+                if let Some(reserve_stake_info) = maybe_reserve_stake_info {
+                    let required_lamports_for_rent_exemption =
+                        stake_rent.saturating_sub(ephemeral_stake_account_info.lamports());
+                    if required_lamports_for_rent_exemption > 0 {
+                        if required_lamports_for_rent_exemption >= reserve_stake_info.lamports() {
+                            return Err(StakePoolError::ReserveDepleted.into());
+                        }
+                        let stake_history_info = maybe_stake_history_info
+                            .ok_or(StakePoolError::MissingRequiredSysvar)?;
+                        Self::stake_withdraw(
+                            stake_pool_info.key,
+                            reserve_stake_info.clone(),
+                            withdraw_authority_info.clone(),
+                            AUTHORITY_WITHDRAW,
+                            stake_pool.stake_withdraw_bump_seed,
+                            ephemeral_stake_account_info.clone(),
+                            clock_info.clone(),
+                            stake_history_info.clone(),
+                            required_lamports_for_rent_exemption,
+                        )?;
+                    }
+                }
+
                 // split into ephemeral stake account
                 Self::stake_split(
                     stake_pool_info.key,
@@ -1408,11 +1440,14 @@ impl Processor {
                     stake_pool.stake_withdraw_bump_seed,
                 )?;
 
-                ephemeral_stake_account_info
+                (
+                    ephemeral_stake_account_info,
+                    ephemeral_stake_account_info.lamports(),
+                )
             } else {
                 // if no ephemeral account is provided, split everything from the
                 // validator stake account, into the transient stake account
-                validator_stake_account_info
+                (validator_stake_account_info, lamports)
             };
 
         let transient_stake_bump_seed = check_transient_stake_address(
@@ -1459,7 +1494,7 @@ impl Processor {
                 withdraw_authority_info.clone(),
                 AUTHORITY_WITHDRAW,
                 stake_pool.stake_withdraw_bump_seed,
-                lamports,
+                split_lamports,
                 transient_stake_account_info.clone(),
             )?;
 
@@ -1482,9 +1517,11 @@ impl Processor {
                 .checked_sub(lamports)
                 .ok_or(StakePoolError::CalculationFailure)?
                 .into();
+        // `split_lamports` may be greater than `lamports` if the reserve stake
+        // funded the rent-exempt reserve
         validator_stake_info.transient_stake_lamports =
             u64::from(validator_stake_info.transient_stake_lamports)
-                .checked_add(lamports)
+                .checked_add(split_lamports)
                 .ok_or(StakePoolError::CalculationFailure)?
                 .into();
         validator_stake_info.transient_seed_suffix = transient_stake_seed.into();
@@ -3811,6 +3848,7 @@ impl Processor {
                     lamports,
                     transient_stake_seed,
                     None,
+                    false,
                 )
             }
             StakePoolInstruction::DecreaseAdditionalValidatorStake {
@@ -3825,6 +3863,7 @@ impl Processor {
                     lamports,
                     transient_stake_seed,
                     Some(ephemeral_stake_seed),
+                    true,
                 )
             }
             StakePoolInstruction::IncreaseValidatorStake {
@@ -4038,6 +4077,7 @@ impl PrintProgramError for StakePoolError {
             StakePoolError::ExceededSlippage => msg!("Error: instruction exceeds desired slippage limit"),
             StakePoolError::IncorrectMintDecimals => msg!("Error: Provided mint does not have 9 decimals to match SOL"),
             StakePoolError::ReserveDepleted => msg!("Error: Pool reserve does not have enough lamports to fund rent-exempt reserve in split destination. Deposit more SOL in reserve, or pre-fund split destination with the rent-exempt reserve for a stake account."),
+            StakePoolError::MissingRequiredSysvar => msg!("Missing required sysvar account"),
         }
     }
 }