Tests for snapshot network renames

Test that we can correctly parse configuration and API calls in a
backwards compatible way.

Signed-off-by: Andrew Laucius <andrewla@gmail.com>

src/firecracker/src/api_server/request/snapshot.rs

@@ -121,7 +121,7 @@ fn parse_put_snapshot_load(body: &Body) -> Result<ParsedRequest, RequestError> {
 
 #[cfg(test)]
 mod tests {
-    use vmm::vmm_config::snapshot::{MemBackendConfig, MemBackendType};
+    use vmm::vmm_config::snapshot::{MemBackendConfig, MemBackendType, NetworkOverride};
 
     use super::*;
     use crate::api_server::parsed_request::tests::{depr_action_from_req, vmm_action_from_request};
@@ -182,6 +182,7 @@ mod tests {
             },
             enable_diff_snapshots: false,
             resume_vm: false,
+            network_overrides: vec![],
         };
         let mut parsed_request = parse_put_snapshot(&Body::new(body), Some("load")).unwrap();
         assert!(parsed_request
@@ -209,6 +210,7 @@ mod tests {
             },
             enable_diff_snapshots: true,
             resume_vm: false,
+            network_overrides: vec![],
         };
         let mut parsed_request = parse_put_snapshot(&Body::new(body), Some("load")).unwrap();
         assert!(parsed_request
@@ -236,6 +238,44 @@ mod tests {
             },
             enable_diff_snapshots: false,
             resume_vm: true,
+            network_overrides: vec![],
+        };
+        let mut parsed_request = parse_put_snapshot(&Body::new(body), Some("load")).unwrap();
+        assert!(parsed_request
+            .parsing_info()
+            .take_deprecation_message()
+            .is_none());
+        assert_eq!(
+            vmm_action_from_request(parsed_request),
+            VmmAction::LoadSnapshot(expected_config)
+        );
+
+        let body = r#"{
+            "snapshot_path": "foo",
+            "mem_backend": {
+                "backend_path": "bar",
+                "backend_type": "Uffd"
+            },
+            "resume_vm": true,
+            "network_overrides": [
+                {
+                    "iface_id": "eth0",
+                    "host_dev_name": "vmtap2"
+                }
+            ]
+        }"#;
+        let expected_config = LoadSnapshotParams {
+            snapshot_path: PathBuf::from("foo"),
+            mem_backend: MemBackendConfig {
+                backend_path: PathBuf::from("bar"),
+                backend_type: MemBackendType::Uffd,
+            },
+            enable_diff_snapshots: false,
+            resume_vm: true,
+            network_overrides: vec![NetworkOverride {
+                iface_id: String::from("eth0"),
+                host_dev_name: String::from("vmtap2"),
+            }],
         };
         let mut parsed_request = parse_put_snapshot(&Body::new(body), Some("load")).unwrap();
         assert!(parsed_request
@@ -260,6 +300,7 @@ mod tests {
             },
             enable_diff_snapshots: false,
             resume_vm: true,
+            network_overrides: vec![],
         };
         let parsed_request = parse_put_snapshot(&Body::new(body), Some("load")).unwrap();
         assert_eq!(

src/vmm/src/persist.rs

@@ -422,7 +422,10 @@ pub fn restore_from_snapshot(
             .iter_mut()
             .find(|x| x.device_state.id == entry.iface_id)
         {
-            device.device_state.tap_if_name = entry.host_dev_name.clone();
+            device
+                .device_state
+                .tap_if_name
+                .clone_from(&entry.host_dev_name);
         } else {
             return Err(SnapshotStateFromFileError::UnknownNetworkDevice.into());
         }

tests/framework/microvm.py

@@ -969,6 +969,7 @@ def restore_from_snapshot(
         snapshot: Snapshot,
         resume: bool = False,
         uffd_path: Path = None,
+        rename_interfaces: dict = None,
     ):
         """Restore a snapshot"""
         jailed_snapshot = snapshot.copy_to_chroot(Path(self.chroot()))
@@ -996,11 +997,19 @@ def restore_from_snapshot(
         # Adjust things just in case
         self.kernel_file = Path(self.kernel_file)
 
+        iface_overrides = []
+        if rename_interfaces is not None:
+            iface_overrides = [
+                {"iface_id": k, "host_dev_name": v}
+                for k, v in rename_interfaces.items()
+            ]
+
         self.api.snapshot_load.put(
             mem_backend=mem_backend,
             snapshot_path=str(jailed_vmstate),
             enable_diff_snapshots=snapshot.is_diff,
             resume_vm=resume,
+            network_overrides=iface_overrides,
         )
         # This is not a "wait for boot", but rather a "VM still works after restoration"
         if snapshot.net_ifaces and resume:

tests/integration_tests/functional/test_snapshot_basic.py

@@ -2,6 +2,7 @@
 # SPDX-License-Identifier: Apache-2.0
 """Basic tests scenarios for snapshot save/restore."""
 
+import dataclasses
 import filecmp
 import logging
 import os
@@ -13,6 +14,7 @@
 import pytest
 
 import host_tools.drive as drive_tools
+import host_tools.network as net_tools
 from framework.microvm import SnapshotType
 from framework.utils import check_filesystem, check_output
 from framework.utils_vsock import (
@@ -540,3 +542,35 @@ def test_vmgenid(guest_kernel_linux_6_1, rootfs, microvm_factory, snapshot_type)
 
         # Update the base for next iteration
         base_snapshot = snapshot
+
+
+def test_snapshot_rename_interface(uvm_nano, microvm_factory):
+    """
+    Test that we can restore a snapshot and point its interface to a
+    different host interface.
+    """
+    base_iface = net_tools.NetIfaceConfig.with_id(0)
+
+    vm = uvm_nano
+    iface1 = dataclasses.replace(base_iface, tap_name="tap1")
+    vm.add_net_iface(iface=iface1)
+    # Create an interface but don't attach it to the device
+    vm.start()
+
+    snapshot = vm.snapshot_full()
+
+    restored_vm = microvm_factory.build()
+    restored_vm.spawn()
+    iface2 = dataclasses.replace(base_iface, tap_name="tap2")
+
+    # The snapshot.net_faces is used by the test framework to create the
+    # appropriate tap devices on the host; we replace those here with the new
+    # name, otherwise the framework would create `tap1` when restoring the
+    # snapshot
+    snapshot.net_ifaces.clear()
+    snapshot.net_ifaces.append(iface2)
+
+    restored_vm.restore_from_snapshot(
+        snapshot, rename_interfaces={base_iface.dev_name: "tap2"}
+    )
+    restored_vm.resume()