Add fees syscall to expose cluster fees into programs (#4472)

runtime/src/bank.rs

@@ -24,6 +24,7 @@ use solana_sdk::hash::{extend_and_hash, Hash};
 use solana_sdk::native_loader;
 use solana_sdk::pubkey::Pubkey;
 use solana_sdk::signature::{Keypair, Signature};
+use solana_sdk::syscall::fees::{self, Fees};
 use solana_sdk::syscall::slot_hashes::{self, SlotHashes};
 use solana_sdk::system_transaction;
 use solana_sdk::timing::{duration_as_ms, duration_as_us, MAX_RECENT_BLOCKHASHES};
@@ -215,6 +216,18 @@ impl Bank {
         self.store(&slot_hashes::id(), &account);
     }
 
+    fn update_fees(&self) {
+        let mut account = self
+            .get_account(&fees::id())
+            .unwrap_or_else(|| fees::create_account(1));
+
+        let mut fees = Fees::from(&account).unwrap();
+        fees.fee_calculator = self.fee_calculator.clone();
+        fees.to(&mut account).unwrap();
+
+        self.store(&fees::id(), &account);
+    }
+
     fn set_hash(&self) -> bool {
         let mut hash = self.hash.write().unwrap();
 
@@ -274,6 +287,7 @@ impl Bank {
         // Bootstrap leader collects fees until `new_from_parent` is called.
         self.collector_id = genesis_block.bootstrap_leader_pubkey;
         self.fee_calculator = genesis_block.fee_calculator.clone();
+        self.update_fees();
 
         for (pubkey, account) in genesis_block.accounts.iter() {
             self.store(pubkey, account);
@@ -1931,6 +1945,21 @@ mod tests {
         assert!(bank.is_votable());
     }
 
+    #[test]
+    fn test_bank_fees_account() {
+        let (mut genesis_block, _) = create_genesis_block(500);
+        genesis_block.fee_calculator.lamports_per_signature = 12345;
+        let bank = Arc::new(Bank::new(&genesis_block));
+
+        let fees_account = bank.get_account(&fees::id()).unwrap();
+        let fees = Fees::from(&fees_account).unwrap();
+        assert_eq!(
+            bank.fee_calculator.lamports_per_signature,
+            fees.fee_calculator.lamports_per_signature
+        );
+        assert_eq!(fees.fee_calculator.lamports_per_signature, 12345);
+    }
+
     #[test]
     fn test_is_delta_with_no_committables() {
         let (genesis_block, mint_keypair) = create_genesis_block(8000);

sdk/src/syscall/fees.rs

@@ -0,0 +1,71 @@
+//! This account contains the current cluster fees
+//!
+use crate::account::Account;
+use crate::account_utils::State;
+use crate::fee_calculator::FeeCalculator;
+use crate::pubkey::Pubkey;
+use crate::syscall;
+use bincode::serialized_size;
+
+/// "Sysca11Fees11111111111111111111111111"
+///  fees account pubkey
+const ID: [u8; 32] = [
+    6, 167, 211, 138, 69, 218, 104, 33, 3, 92, 89, 173, 16, 89, 109, 253, 49, 97, 98, 165, 87, 222,
+    119, 112, 253, 90, 76, 184, 0, 0, 0, 0,
+];
+
+pub fn id() -> Pubkey {
+    Pubkey::new(&ID)
+}
+
+pub fn check_id(pubkey: &Pubkey) -> bool {
+    pubkey.as_ref() == ID
+}
+
+#[repr(C)]
+#[derive(Serialize, Deserialize, Debug, Default)]
+pub struct Fees {
+    pub fee_calculator: FeeCalculator,
+}
+
+impl Fees {
+    pub fn from(account: &Account) -> Option<Self> {
+        account.state().ok()
+    }
+    pub fn to(&self, account: &mut Account) -> Option<()> {
+        account.set_state(self).ok()
+    }
+
+    pub fn size_of() -> usize {
+        serialized_size(&Fees::default()).unwrap() as usize
+    }
+}
+
+pub fn create_account(lamports: u64) -> Account {
+    Account::new(lamports, Fees::size_of(), &syscall::id())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_fees_id() {
+        let name = "Sysca11Fees11111111111111111111111111111111";
+        // To get the bytes above:
+        // dbg!((name, bs58::decode(name).into_vec().unwrap()));
+        assert_eq!(name, id().to_string());
+        assert!(check_id(&id()));
+    }
+
+    #[test]
+    fn test_fees_create_account() {
+        let lamports = 42;
+        let account = create_account(lamports);
+        let fees = Fees::from(&account).unwrap();
+        assert_eq!(
+            fees.fee_calculator.lamports_per_signature,
+            FeeCalculator::default().lamports_per_signature
+        );
+    }
+}

sdk/src/syscall/mod.rs

@@ -2,6 +2,7 @@
 //!
 use crate::pubkey::Pubkey;
 
+pub mod fees;
 pub mod slot_hashes;
 
 /// "Sysca11111111111111111111111111111111111111"