SVM: add new solana-svm-rent-collector crate (#2688)

Cargo.toml

@@ -119,6 +119,7 @@ members = [
     "streamer",
     "svm",
     "svm-conformance",
+    "svm-rent-collector",
     "svm-transaction",
     "svm/examples/paytube",
     "test-validator",
@@ -434,6 +435,7 @@ solana-streamer = { path = "streamer", version = "=2.1.0" }
 solana-svm = { path = "svm", version = "=2.1.0" }
 solana-svm-conformance = { path = "svm-conformance", version = "=2.1.0" }
 solana-svm-example-paytube = { path = "svm/examples/paytube", version = "=2.1.0" }
+solana-svm-rent-collector = { path = "svm-rent-collector", version = "=2.1.0" }
 solana-svm-transaction = { path = "svm-transaction", version = "=2.1.0" }
 solana-system-program = { path = "programs/system", version = "=2.1.0" }
 solana-test-validator = { path = "test-validator", version = "=2.1.0" }

svm-rent-collector/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "solana-svm-rent-collector"
+description = "Solana SVM Rent Collector"
+documentation = "https://docs.rs/solana-svm-rent-collector"
+version = { workspace = true }
+authors = { workspace = true }
+repository = { workspace = true }
+homepage = { workspace = true }
+license = { workspace = true }
+edition = { workspace = true }
+
+[dependencies]
+solana-sdk = { workspace = true }

svm-rent-collector/src/lib.rs

@@ -0,0 +1,6 @@
+//! Solana SVM Rent Collector.
+//!
+//! Rent management for SVM.
+
+pub mod rent_state;
+pub mod svm_rent_collector;

svm-rent-collector/src/rent_state.rs

@@ -0,0 +1,15 @@
+//! Account rent state.
+
+/// Rent state of a Solana account.
+#[derive(Debug, PartialEq, Eq)]
+pub enum RentState {
+    /// account.lamports == 0
+    Uninitialized,
+    /// 0 < account.lamports < rent-exempt-minimum
+    RentPaying {
+        lamports: u64,    // account.lamports()
+        data_size: usize, // account.data().len()
+    },
+    /// account.lamports >= rent-exempt-minimum
+    RentExempt,
+}

svm-rent-collector/src/svm_rent_collector.rs

@@ -0,0 +1,137 @@
+//! Plugin trait for rent collection within the Solana SVM.
+
+use {
+    crate::rent_state::RentState,
+    solana_sdk::{
+        account::{AccountSharedData, ReadableAccount},
+        clock::Epoch,
+        pubkey::Pubkey,
+        rent::{Rent, RentDue},
+        rent_collector::CollectedInfo,
+        transaction::{Result, TransactionError},
+        transaction_context::{IndexOfAccount, TransactionContext},
+    },
+};
+
+mod rent_collector;
+
+/// Rent collector trait. Represents an entity that can evaluate the rent state
+/// of an account, determine rent due, and collect rent.
+///
+/// Implementors are responsible for evaluating rent due and collecting rent
+/// from accounts, if required. Methods for evaluating account rent state have
+/// default implementations, which can be overridden for customized rent
+/// management.
+pub trait SVMRentCollector {
+    /// Check rent state transition for an account in a transaction.
+    ///
+    /// This method has a default implementation that calls into
+    /// `check_rent_state_with_account`.
+    fn check_rent_state(
+        &self,
+        pre_rent_state: Option<&RentState>,
+        post_rent_state: Option<&RentState>,
+        transaction_context: &TransactionContext,
+        index: IndexOfAccount,
+    ) -> Result<()> {
+        if let Some((pre_rent_state, post_rent_state)) = pre_rent_state.zip(post_rent_state) {
+            let expect_msg =
+                "account must exist at TransactionContext index if rent-states are Some";
+            self.check_rent_state_with_account(
+                pre_rent_state,
+                post_rent_state,
+                transaction_context
+                    .get_key_of_account_at_index(index)
+                    .expect(expect_msg),
+                &transaction_context
+                    .get_account_at_index(index)
+                    .expect(expect_msg)
+                    .borrow(),
+                index,
+            )?;
+        }
+        Ok(())
+    }
+
+    /// Check rent state transition for an account directly.
+    ///
+    /// This method has a default implementation that checks whether the
+    /// transition is allowed and returns an error if it is not. It also
+    /// verifies that the account is not the incinerator.
+    fn check_rent_state_with_account(
+        &self,
+        pre_rent_state: &RentState,
+        post_rent_state: &RentState,
+        address: &Pubkey,
+        _account_state: &AccountSharedData,
+        account_index: IndexOfAccount,
+    ) -> Result<()> {
+        if !solana_sdk::incinerator::check_id(address)
+            && !self.transition_allowed(pre_rent_state, post_rent_state)
+        {
+            let account_index = account_index as u8;
+            Err(TransactionError::InsufficientFundsForRent { account_index })
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Collect rent from an account.
+    fn collect_rent(&self, address: &Pubkey, account: &mut AccountSharedData) -> CollectedInfo;
+
+    /// Determine the rent state of an account.
+    ///
+    /// This method has a default implementation that treats accounts with zero
+    /// lamports as uninitialized and uses the implemented `get_rent` to
+    /// determine whether an account is rent-exempt.
+    fn get_account_rent_state(&self, account: &AccountSharedData) -> RentState {
+        if account.lamports() == 0 {
+            RentState::Uninitialized
+        } else if self
+            .get_rent()
+            .is_exempt(account.lamports(), account.data().len())
+        {
+            RentState::RentExempt
+        } else {
+            RentState::RentPaying {
+                data_size: account.data().len(),
+                lamports: account.lamports(),
+            }
+        }
+    }
+
+    /// Get the rent collector's rent instance.
+    fn get_rent(&self) -> &Rent;
+
+    /// Get the rent due for an account.
+    fn get_rent_due(&self, lamports: u64, data_len: usize, account_rent_epoch: Epoch) -> RentDue;
+
+    /// Check whether a transition from the pre_rent_state to the
+    /// post_rent_state is valid.
+    ///
+    /// This method has a default implementation that allows transitions from
+    /// any state to `RentState::Uninitialized` or `RentState::RentExempt`.
+    /// Pre-state `RentState::RentPaying` can only transition to
+    /// `RentState::RentPaying` if the data size remains the same and the
+    /// account is not credited.
+    fn transition_allowed(&self, pre_rent_state: &RentState, post_rent_state: &RentState) -> bool {
+        match post_rent_state {
+            RentState::Uninitialized | RentState::RentExempt => true,
+            RentState::RentPaying {
+                data_size: post_data_size,
+                lamports: post_lamports,
+            } => {
+                match pre_rent_state {
+                    RentState::Uninitialized | RentState::RentExempt => false,
+                    RentState::RentPaying {
+                        data_size: pre_data_size,
+                        lamports: pre_lamports,
+                    } => {
+                        // Cannot remain RentPaying if resized or credited.
+                        post_data_size == pre_data_size && post_lamports <= pre_lamports
+                    }
+                }
+            }
+        }
+    }
+}