Removed unnecessary requirements for loading snapshots

Signed-off-by: David Son <davbson@amazon.com>

Author: sondavidb

examples/cmd/snapshotting/example_demo.go

@@ -299,8 +299,26 @@ func loadSnapshotSSH(ctx context.Context, socketPath, memPath, snapPath, ipToRes
 		},
 	}
 
+	driveID := "root"
+	isRootDevice := true
+	isReadOnly := false
+	rootfsPath := "root-drive-with-ssh.img"
+
 	socketFile := fmt.Sprintf("%s.load", socketPath)
-	cfg := createNewConfig(socketFile, withNetworkInterface(networkInterface))
+	cfg := sdk.Config{
+		SocketPath: socketPath + ".load",
+		Drives: []models.Drive{
+			{
+				DriveID:      &driveID,
+				IsRootDevice: &isRootDevice,
+				IsReadOnly:   &isReadOnly,
+				PathOnHost:   &rootfsPath,
+			},
+		},
+		NetworkInterfaces: []sdk.NetworkInterface{
+			networkInterface,
+		},
+	}
 
 	// Use the firecracker binary
 	cmd := sdk.VMCommandBuilder{}.WithSocketPath(socketFile).WithBin(filepath.Join(dir, "firecracker")).Build(ctx)

examples/cmd/snapshotting/go.mod

@@ -40,4 +40,4 @@ require (
 	gopkg.in/yaml.v2 v2.4.0 // indirect
 )
 
-replace github.com/firecracker-microvm/firecracker-go-sdk => ../../..
+replace github.com/firecracker-microvm/firecracker-go-sdk => ../../..

handlers.go

@@ -37,9 +37,10 @@ const (
 	CreateBalloonHandlerName           = "fcinit.CreateBalloon"
 	LoadSnapshotHandlerName            = "fcinit.LoadSnapshot"
 
-	ValidateCfgHandlerName        = "validate.Cfg"
-	ValidateJailerCfgHandlerName  = "validate.JailerCfg"
-	ValidateNetworkCfgHandlerName = "validate.NetworkCfg"
+	ValidateCfgHandlerName             = "validate.Cfg"
+	ValidateJailerCfgHandlerName       = "validate.JailerCfg"
+	ValidateNetworkCfgHandlerName      = "validate.NetworkCfg"
+	ValidateLoadSnapshotCfgHandlerName = "validate.LoadSnapshotCfg"
 )
 
 // HandlersAdapter is an interface used to modify a given set of handlers.
@@ -57,6 +58,16 @@ var ConfigValidationHandler = Handler{
 	},
 }
 
+// LoadSnapshotConfigValidationHandler is used to validate that required
+// fields are present.
+var LoadSnapshotConfigValidationHandler = Handler{
+	Name: ValidateLoadSnapshotCfgHandlerName,
+	Fn: func(ctx context.Context, m *Machine) error {
+		// ensure that the configuration is valid for the FcInit handlers.
+		return m.Cfg.ValidateLoadSnapshot()
+	},
+}
+
 // JailerConfigValidationHandler is used to validate that required fields are
 // present.
 var JailerConfigValidationHandler = Handler{
@@ -317,6 +328,11 @@ var defaultValidationHandlerList = HandlerList{}.Append(
 	NetworkConfigValidationHandler,
 )
 
+var loadSnapshotValidationHandlerList = HandlerList{}.Append(
+	NetworkConfigValidationHandler,
+	LoadSnapshotConfigValidationHandler,
+)
+
 var defaultHandlers = Handlers{
 	Validation: defaultValidationHandlerList,
 	FcInit:     defaultFcInitHandlerList,

machine.go

@@ -204,6 +204,33 @@ func (cfg *Config) Validate() error {
 	return nil
 }
 
+func (cfg *Config) ValidateLoadSnapshot() error {
+	if cfg.DisableValidation {
+		return nil
+	}
+
+	for _, drive := range cfg.Drives {
+		rootPath := StringValue(drive.PathOnHost)
+		if _, err := os.Stat(rootPath); err != nil {
+			return fmt.Errorf("failed to stat drive path, %q: %v", rootPath, err)
+		}
+	}
+
+	if _, err := os.Stat(cfg.SocketPath); err == nil {
+		return fmt.Errorf("socket %s already exists", cfg.SocketPath)
+	}
+
+	if _, err := os.Stat(cfg.Snapshot.MemFilePath); err != nil {
+		return err
+	}
+
+	if _, err := os.Stat(cfg.Snapshot.SnapshotPath); err != nil {
+		return err
+	}
+
+	return nil
+}
+
 func (cfg *Config) ValidateNetwork() error {
 	if cfg.DisableValidation {
 		return nil

machine_test.go

@@ -1939,7 +1939,19 @@ func TestLoadSnapshot(t *testing.T) {
 			},
 
 			loadSnapshot: func(ctx context.Context, machineLogger *logrus.Logger, socketPath, memPath, snapPath string) {
-				cfg := createValidConfig(t, socketPath+".load")
+				// Note that many fields are not necessary when loading a snapshot
+				cfg := Config{
+					SocketPath: socketPath + ".load",
+					Drives: []models.Drive{
+						{
+							DriveID:      String("root"),
+							IsRootDevice: Bool(true),
+							IsReadOnly:   Bool(true),
+							PathOnHost:   String(testRootfs),
+						},
+					},
+				}
+
 				m, err := NewMachine(ctx, cfg, func(m *Machine) {
 					// Rewriting m.cmd partially wouldn't work since Cmd has
 					// some unexported members
@@ -2078,10 +2090,21 @@ func TestLoadSnapshot(t *testing.T) {
 						VMIfName:    "eth0",
 					},
 				}
-				cfg := createValidConfig(t, fmt.Sprintf("%s.load", socketPath),
-					withRootDrive(rootfsPath),
-					withNetworkInterface(networkInterface),
-				)
+
+				cfg := Config{
+					SocketPath: socketPath + ".load",
+					Drives: []models.Drive{
+						{
+							DriveID:      String("root"),
+							IsRootDevice: Bool(true),
+							IsReadOnly:   Bool(true),
+							PathOnHost:   String(rootfsPath),
+						},
+					},
+					NetworkInterfaces: []NetworkInterface{
+						networkInterface,
+					},
+				}
 
 				cmd := VMCommandBuilder{}.WithSocketPath(fmt.Sprintf("%s.load", socketPath)).WithBin(getFirecrackerBinaryPath()).Build(ctx)
 

opts.go

@@ -62,6 +62,7 @@ func WithSnapshot(memFilePath, snapshotPath string, opts ...WithSnapshotOpt) Opt
 			opt(&m.Cfg.Snapshot)
 		}
 
+		m.Handlers.Validation = loadSnapshotValidationHandlerList
 		m.Handlers.FcInit = loadSnapshotHandlerList
 	}
 }