reject transactions from the mempool, that take too long to validate (#19611)

Author: arvidn

chia/full_node/mempool_manager.py

@@ -588,7 +588,7 @@ async def validate_spend_bundle(
             Optional[MempoolItem]: the item to add (to mempool or pending pool)
             list[bytes32]: conflicting mempool items to remove, if no Err
         """
-        start_time = time.time()
+        start_time = time.monotonic()
         if self.peak is None:
             return Err.MEMPOOL_NOT_INITIALIZED, None, []
 
@@ -778,14 +778,18 @@ async def validate_spend_bundle(
             if not can_replace(conflicts, removal_names, potential):
                 return Err.MEMPOOL_CONFLICT, potential, []
 
-        duration = time.time() - start_time
+        duration = time.monotonic() - start_time
 
         log.log(
             logging.DEBUG if duration < 2 else logging.WARNING,
             f"add_spendbundle {spend_name} took {duration:0.2f} seconds. "
             f"Cost: {cost} ({round(100.0 * cost / self.constants.MAX_BLOCK_COST_CLVM, 3)}% of max block cost)",
         )
 
+        if duration > 2:
+            log.warning("validating spend took too long, rejecting")
+            return Err.INVALID_SPEND_BUNDLE, None, []
+
         return None, potential, [item.name for item in conflicts]
 
     def get_spendbundle(self, bundle_hash: bytes32) -> Optional[SpendBundle]: