fix: Pass through no-API shutdown exit code

Without passing through the exit code a non-zero exit code was returned
on a successful no-API shutdown.

Signed-off-by: Jonathan Woollett-Light <jcawl@amazon.co.uk>

CHANGELOG.md

@@ -22,6 +22,9 @@
 
 - Fixed a bug that ignored the `--show-log-origin` option, preventing it from
   printing the source code file of the log messages.
+- [#4178](https://github.com/firecracker-microvm/firecracker/pull/4178):
+  Fixed a bug reporting a non-zero exit code on successful shutdown when
+  starting Firecracker with `--no-api`.
 
 ## [1.5.0]
 

src/firecracker/src/main.rs

@@ -83,6 +83,7 @@ impl From<MainError> for ExitCode {
             MainError::InvalidLogLevel(_) => FcExitCode::BadConfiguration,
             MainError::RunWithApi(ApiServerError::MicroVMStoppedWithoutError(code)) => code,
             MainError::RunWithApi(ApiServerError::MicroVMStoppedWithError(code)) => code,
+            MainError::RunWithoutApiError(RunWithoutApiError::Shutdown(code)) => code,
             _ => FcExitCode::GenericError,
         };
 

tests/integration_tests/functional/test_cmd_line_start.py

@@ -7,6 +7,7 @@
 import platform
 import re
 import shutil
+import time
 from pathlib import Path
 
 import pytest
@@ -156,6 +157,27 @@ def test_config_start_no_api(uvm_plain, vm_config_file):
     )
 
 
+@pytest.mark.parametrize("vm_config_file", ["framework/vm_config_network.json"])
+def test_config_start_no_api_exit(uvm_plain, vm_config_file):
+    """
+    Test microvm exit when API server is disabled.
+    """
+    test_microvm = uvm_plain
+    _configure_vm_from_json(test_microvm, vm_config_file)
+    _configure_network_interface(test_microvm)
+    test_microvm.jailer.extra_args.update({"no-api": None})
+
+    test_microvm.spawn()  # Start Firecracker and MicroVM
+    time.sleep(3)  # Wait for startup
+    test_microvm.ssh.run("reboot")  # Exit
+    time.sleep(3)  # Wait for shutdown
+
+    # Check error log
+    test_microvm.check_log_message(
+        "RunWithoutApiError error: MicroVMStopped without an error: Ok"
+    )
+
+
 @pytest.mark.parametrize(
     "vm_config_file",
     [