remove 1 rule check, fix docs

zebra-chain/src/transaction/unmined.rs

@@ -357,12 +357,7 @@ impl VerifiedUnminedTx {
         let fee_weight_ratio = zip317::conventional_fee_weight_ratio(&transaction, miner_fee);
         let unpaid_actions = zip317::unpaid_actions(&transaction, miner_fee);
 
-        zip317::mempool_checks(
-            unpaid_actions,
-            miner_fee,
-            transaction.conventional_fee,
-            transaction.size,
-        )?;
+        zip317::mempool_checks(unpaid_actions, miner_fee, transaction.size)?;
 
         Ok(Self {
             transaction,

zebra-chain/src/transaction/unmined/zip317.rs

@@ -169,7 +169,6 @@ fn conventional_actions(transaction: &Transaction) -> u32 {
 pub fn mempool_checks(
     unpaid_actions: u32,
     miner_fee: Amount<NonNegative>,
-    conventional_fee: Amount<NonNegative>,
     transaction_size: usize,
 ) -> Result<(), Error> {
     // # Standard Rule
@@ -189,18 +188,17 @@ pub fn mempool_checks(
     // > conventional fee as specified in this ZIP.
     //
     // <https://zips.z.cash/zip-0317#transaction-relaying>
-    if miner_fee < conventional_fee {
-        return Err(Error::FeeBelowConventional);
-    }
-
-    // # Standard rule
     //
-    // > Minimum Fee Rate
-    // >
-    // > Transactions must pay a fee of at least 100 zatoshis per 1000 bytes of serialized size,
-    // > with a maximum fee of 1000 zatoshis. In zcashd this is `DEFAULT_MIN_RELAY_TX_FEE`.
+    // In Zebra, we use a similar minimum fee rate to `zcashd` v5.5.0 and later.
+    // Transactions must pay a fee of at least 100 zatoshis per 1000 bytes of serialized size,
+    // with a maximum fee of 1000 zatoshis.
+    //
+    // <https://github.com/zcash/zcash/blob/9e856cfc5b81aa2607a16a23ff5584ea10014de6/src/amount.cpp#L24-L37>
     //
-    // <https://github.com/ZcashFoundation/zebra/issues/5336#issuecomment-1506748801>
+    // In zcashd this is `DEFAULT_MIN_RELAY_TX_FEE` and `LEGACY_DEFAULT_FEE`:
+    // <https://github.com/zcash/zcash/blob/f512291ff20098291442e83713de89bcddc07546/src/main.h#L71-L72>
+    // <https://github.com/zcash/zcash/blob/9e856cfc5b81aa2607a16a23ff5584ea10014de6/src/amount.h#L35-L36>
+
     const KILOBYTE: usize = 1000;
 
     // This calculation can't overflow, because transactions are limited to 2 MB,
@@ -232,9 +230,6 @@ pub enum Error {
     #[error("Unpaid actions is higher than the limit")]
     UnpaidActions,
 
-    #[error("Transaction fee is below the conventional fee for the transaction")]
-    FeeBelowConventional,
-
     #[error("Transaction fee is below the minimum fee rate")]
     FeeBelowMinimumRate,
 }

zebra-chain/src/transaction/unmined/zip317/tests.rs

@@ -3,38 +3,15 @@
 use super::{mempool_checks, Amount, Error};
 #[test]
 fn zip317_unpaid_actions_err() {
-    let check = mempool_checks(
-        51,
-        Amount::try_from(1).unwrap(),
-        Amount::try_from(10000).unwrap(),
-        1,
-    );
+    let check = mempool_checks(51, Amount::try_from(1).unwrap(), 1);
 
     assert!(check.is_err());
     assert_eq!(check.err(), Some(Error::UnpaidActions));
 }
 
-#[test]
-fn zip317_convetional_fee_err() {
-    let check = mempool_checks(
-        50,
-        Amount::try_from(1).unwrap(),
-        Amount::try_from(10000).unwrap(),
-        1,
-    );
-
-    assert!(check.is_err());
-    assert_eq!(check.err(), Some(Error::FeeBelowConventional));
-}
-
 #[test]
 fn zip317_minimum_rate_fee_err() {
-    let check = mempool_checks(
-        50,
-        Amount::try_from(1).unwrap(),
-        Amount::try_from(1).unwrap(),
-        1000,
-    );
+    let check = mempool_checks(50, Amount::try_from(1).unwrap(), 1000);
 
     assert!(check.is_err());
     assert_eq!(check.err(), Some(Error::FeeBelowMinimumRate));

zebra-consensus/src/transaction/tests.rs

@@ -2886,9 +2886,7 @@ async fn mempool_zip317_error() {
     assert!(verifier_response.is_err());
     assert_eq!(
         verifier_response.err(),
-        Some(TransactionError::Zip317(
-            zip317::Error::FeeBelowConventional
-        ))
+        Some(TransactionError::Zip317(zip317::Error::FeeBelowMinimumRate))
     );
 }