feat(l1): enforce minimum priority-fee floor at mempool admission

cmd/ethrex/cli.rs

@@ -10,7 +10,7 @@ use std::{
 
 use clap::{ArgAction, Parser as ClapParser, Subcommand as ClapSubcommand};
 use ethrex_blockchain::{
-    BlockchainOptions, BlockchainType, L2Config,
+    BlockchainOptions, BlockchainType, DEFAULT_MIN_TIP_WEI, L2Config,
     error::{ChainError, InvalidBlockError},
 };
 use ethrex_common::types::{Block, DEFAULT_BUILDER_GAS_CEIL, Genesis, validate_block_body};
@@ -183,6 +183,15 @@ pub struct Options {
         env = "ETHREX_MEMPOOL_MAX_SIZE"
     )]
     pub mempool_max_size: usize,
+    #[arg(
+        help = "Minimum priority-fee cap (in wei) required for a transaction to be admitted into the mempool. Compared against the raw tip cap: `max_priority_fee_per_gas` for typed transactions, `gas_price` for legacy transactions (independent of current base fee, so admission stays stable as base fee oscillates). Set to 0 to disable the floor.",
+        long = "mempool.min-tip",
+        default_value_t = DEFAULT_MIN_TIP_WEI,
+        value_name = "MIN_TIP_WEI",
+        help_heading = "Node options",
+        env = "ETHREX_MEMPOOL_MIN_TIP"
+    )]
+    pub mempool_min_tip: u64,
     #[arg(
         long = "http.addr",
         default_value = "127.0.0.1",
@@ -464,6 +473,7 @@ impl Default for Options {
             dev: Default::default(),
             force: false,
             mempool_max_size: Default::default(),
+            mempool_min_tip: DEFAULT_MIN_TIP_WEI,
             tx_broadcasting_time_interval: Default::default(),
             target_peers: Default::default(),
             lookup_interval: Default::default(),

cmd/ethrex/initializers.rs

@@ -531,6 +531,7 @@ pub async fn init_l1(
             max_blobs_per_block: opts.max_blobs_per_block,
             precompute_witnesses: opts.precompute_witnesses,
             precompile_cache_enabled: !opts.no_precompile_cache,
+            min_tip_wei: opts.mempool_min_tip,
         },
     );
 

cmd/ethrex/l2/initializers.rs

@@ -228,6 +228,7 @@ pub async fn init_l2(
         max_blobs_per_block: None, // L2 doesn't support blob transactions
         precompute_witnesses: opts.node_opts.precompute_witnesses,
         precompile_cache_enabled: true,
+        min_tip_wei: opts.node_opts.mempool_min_tip,
     };
 
     let blockchain = init_blockchain(store.clone(), blockchain_opts.clone());

crates/blockchain/blockchain.rs

@@ -211,6 +211,10 @@ pub struct Blockchain {
     merkle_pool: rayon::ThreadPool,
 }
 
+/// Default min-tip floor (wei). Matches geth's mempool `PriceLimit = 1 wei`.
+/// Effectively just rejects zero-tip transactions at admission.
+pub const DEFAULT_MIN_TIP_WEI: u64 = 1;
+
 /// Configuration options for the blockchain.
 #[derive(Debug, Clone)]
 pub struct BlockchainOptions {
@@ -229,6 +233,10 @@ pub struct BlockchainOptions {
     /// warmer thread and the executor. Set to false (via `--no-precompile-cache`) to
     /// disable the cache for benchmarking purposes.
     pub precompile_cache_enabled: bool,
+    /// Minimum effective priority fee (in wei) required for a transaction to be
+    /// admitted into the mempool. Transactions below this floor are rejected at
+    /// admission. Set to 0 to disable the floor.
+    pub min_tip_wei: u64,
 }
 
 impl Default for BlockchainOptions {
@@ -240,6 +248,7 @@ impl Default for BlockchainOptions {
             max_blobs_per_block: None,
             precompute_witnesses: false,
             precompile_cache_enabled: true,
+            min_tip_wei: DEFAULT_MIN_TIP_WEI,
         }
     }
 }
@@ -342,13 +351,20 @@ impl Blockchain {
         }
     }
 
+    /// Test-permissive `Blockchain` constructor. Mirrors `BlockchainOptions::default`
+    /// but disables admission-policy gates (e.g. the min-tip floor) so that
+    /// unrelated tests don't need to set every mempool option explicitly.
     pub fn default_with_store(store: Store) -> Self {
+        let options = BlockchainOptions {
+            min_tip_wei: 0,
+            ..BlockchainOptions::default()
+        };
         Self {
             storage: store,
             mempool: Mempool::new(MAX_MEMPOOL_SIZE_DEFAULT),
             is_synced: AtomicBool::new(false),
             payloads: Arc::new(TokioMutex::new(Vec::new())),
-            options: BlockchainOptions::default(),
+            options,
             merkle_pool: Self::build_merkle_pool(),
         }
     }
@@ -2505,6 +2521,24 @@ impl Blockchain {
             return Err(MempoolError::TxTipAboveFeeCapError);
         }
 
+        // Admission-time minimum tip floor. Compares the raw tip cap
+        // (`max_priority_fee_per_gas` for typed txs, `gas_price` for legacy)
+        // against `min_tip_wei`, matching geth's `PriceLimit` check on
+        // `tx.GasTipCap()` and reth's check on `max_priority_fee_per_gas`.
+        // Using the raw tip cap keeps the admission decision independent of
+        // the current base fee, so a tx that paid the floor at admission
+        // doesn't get reclassified as under-floor when base fee oscillates.
+        // A floor of 0 disables the check.
+        if self.options.min_tip_wei > 0 {
+            let tip_cap = u64::try_from(tx.gas_tip_cap()).unwrap_or(u64::MAX);
+            if tip_cap < self.options.min_tip_wei {
+                return Err(MempoolError::TipBelowMinimum {
+                    actual: tip_cap,
+                    limit: self.options.min_tip_wei,
+                });
+            }
+        }
+
         // Check that the gas limit covers the gas needs for transaction metadata.
         if tx.gas_limit() < mempool::transaction_intrinsic_gas(tx, &header, &config)? {
             return Err(MempoolError::TxIntrinsicGasCostAboveLimitError);

crates/blockchain/error.rs

@@ -83,6 +83,8 @@ pub enum MempoolError {
     TxMaxInitCodeSizeError,
     #[error("Transaction encoded size ({actual} bytes) exceeds the {limit}-byte limit")]
     TxSizeExceeded { actual: usize, limit: usize },
+    #[error("Tip cap {actual} wei below the configured minimum of {limit} wei")]
+    TipBelowMinimum { actual: u64, limit: u64 },
     #[error("Transaction gas limit exceeded")]
     TxGasLimitExceededError,
     #[error(

crates/common/types/constants.rs

@@ -12,10 +12,9 @@ pub const VERSIONED_HASH_VERSION_KZG: u8 = 0x01; // Defined in [EIP-4844](https:
 /// Minimum tip, obtained from geth's default miner config (https://github.com/ethereum/go-ethereum/blob/f750117ad19d623622cc4a46ea361a716ba7407e/miner/miner.go#L56)
 ///
 /// Scope: this constant is consumed only by the RPC gas-price estimators
-/// (`eth_gasPrice`, `eth_maxPriorityFeePerGas`). It is NOT a mempool
-/// admission gate — zero-tip transactions are currently admitted.
-///
-/// TODO: This should be configurable along with the tip filter on https://github.com/lambdaclass/ethrex/issues/680
+/// (`eth_gasPrice`, `eth_maxPriorityFeePerGas`). The mempool admission
+/// floor is a separate, lower default (see
+/// `ethrex_blockchain::DEFAULT_MIN_TIP_WEI`).
 pub const MIN_GAS_TIP: u64 = 1000000;
 
 // Blob size related

docs/CLI.md

@@ -91,6 +91,12 @@ Node options:
           [env: ETHREX_MEMPOOL_MAX_SIZE=]
           [default: 10000]
 
+      --mempool.min-tip <MIN_TIP_WEI>
+          Minimum priority-fee cap (in wei) required for a transaction to be admitted into the mempool. Compared against the raw tip cap: `max_priority_fee_per_gas` for typed transactions, `gas_price` for legacy transactions (independent of current base fee, so admission stays stable as base fee oscillates). Set to 0 to disable the floor.
+
+          [env: ETHREX_MEMPOOL_MIN_TIP=]
+          [default: 1]
+
       --precompute-witnesses
           Once synced, computes execution witnesses upon receiving newPayload messages and stores them in local storage