From 93b231ecb3d0a92b98ba96e6f1de11eb56737cae Mon Sep 17 00:00:00 2001
From: pecornilleau <pe.cornilleau@marigold.dev>
Date: Mon, 12 Jun 2023 19:09:33 +0200
Subject: [PATCH] EVM: Kernel: simulation mode doesn't require gas

---
 src/bin_evm_proxy/lib/simulation.ml     |  4 +--
 src/kernel_evm/kernel/src/simulation.rs | 33 ++++++++++++++++++++++++-
 tezt/tests/evm_rollup.ml                |  2 --
 3 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/src/bin_evm_proxy/lib/simulation.ml b/src/bin_evm_proxy/lib/simulation.ml
index a1c024b186e7..cf30843756c5 100644
--- a/src/bin_evm_proxy/lib/simulation.ml
+++ b/src/bin_evm_proxy/lib/simulation.ml
@@ -45,9 +45,7 @@ let rlp_encode call =
       [
         of_opt of_addr call.from;
         of_opt of_addr call.to_;
-        (* TODO: https://gitlab.com/tezos/tezos/-/issues/5863
-           evm_execution will fail a simulation without gas *)
-        of_qty (Option.value ~default:(Qty (Z.of_int 11111)) call.gas);
+        of_opt of_qty call.gas;
         of_opt of_qty call.gasPrice;
         of_opt of_qty call.value;
         of_opt of_hash call.data;
diff --git a/src/kernel_evm/kernel/src/simulation.rs b/src/kernel_evm/kernel/src/simulation.rs
index bc1eba6d1eb3..6e81a3bc2572 100644
--- a/src/kernel_evm/kernel/src/simulation.rs
+++ b/src/kernel_evm/kernel/src/simulation.rs
@@ -23,6 +23,9 @@ pub const SIMULATION_SIMPLE_TAG: u8 = 1;
 pub const SIMULATION_CREATE_TAG: u8 = 2;
 // SIMULATION/CHUNK/NUM 2B/CHUNK
 pub const SIMULATION_CHUNK_TAG: u8 = 3;
+/// Maximum gas used by the simulation. Bounded to limit DOS on the rollup node
+/// Is used as default value if no gas is set.
+pub const MAX_SIMULATION_GAS: u64 = 1_000_000_000u64;
 
 /// Container for eth_call data, used in messages sent by the rollup node
 /// simulation.
@@ -85,7 +88,9 @@ impl Simulation {
             self.to,
             self.from.unwrap_or(default_caller),
             self.data.clone(),
-            self.gas,
+            self.gas
+                .map(|gas| u64::max(gas, MAX_SIMULATION_GAS))
+                .or(Some(MAX_SIMULATION_GAS)), // gas could be omitted
             self.value,
         )
         .map_err(Error::Simulation)?;
@@ -394,6 +399,32 @@ mod tests {
         );
     }
 
+    #[test]
+    fn simulation_result_no_gas() {
+        // setup
+        let mut host = MockHost::default();
+        let new_address = create_contract(&mut host);
+
+        // run simulation num
+        let simulation = Simulation {
+            from: None,
+            gas_price: None,
+            to: Some(new_address),
+            data: hex::decode(STORAGE_CONTRACT_CALL_NUM).unwrap(),
+            gas: None,
+            value: None,
+        };
+        let outcome = simulation.run(&mut host);
+
+        assert!(outcome.is_ok(), "simulation should have succeeded");
+        let outcome = outcome.unwrap();
+        assert_eq!(
+            Some(vec![0u8; 32]),
+            outcome.result,
+            "simulation result should be 0"
+        );
+    }
+
     #[test]
     fn parse_simulation() {
         let to = address_of_str("3535353535353535353535353535353535353535");
diff --git a/tezt/tests/evm_rollup.ml b/tezt/tests/evm_rollup.ml
index bd103ff2861f..da28514cbacc 100644
--- a/tezt/tests/evm_rollup.ml
+++ b/tezt/tests/evm_rollup.ml
@@ -1082,7 +1082,6 @@ let test_eth_call_large =
         [
           ("to", Ezjsonm.encode_string sender.address);
           ("data", Ezjsonm.encode_string ("0x" ^ String.make 12_000 'a'));
-          ("gas", `String "111111");
         ]
       in
 
@@ -1132,7 +1131,6 @@ let test_eth_call_storage_contract_rollup_node =
         [
           ("to", Ezjsonm.encode_string address);
           ("data", Ezjsonm.encode_string data);
-          ("gas", `String "111111");
         ]
       in
 
-- 
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