[WIP]: Create a Plugin System for Lima

Makefile

@@ -241,18 +241,44 @@ endif
 # calls the native resolver library and not the simplistic version in the Go library.
 ENVS__output/bin/limactl$(exe) = CGO_ENABLED=1 GOOS="$(GOOS)" GOARCH="$(GOARCH)" CC="$(CC)"
 
+LIMACTL_DRIVER_TAGS :=
+ifneq (,$(findstring vz,$(ADDITIONAL_DRIVERS)))
+LIMACTL_DRIVER_TAGS += external_vz
+endif
+ifneq (,$(findstring qemu,$(ADDITIONAL_DRIVERS)))
+LIMACTL_DRIVER_TAGS += external_qemu
+endif
+ifneq (,$(findstring wsl2,$(ADDITIONAL_DRIVERS)))
+LIMACTL_DRIVER_TAGS += external_wsl2
+endif
+
+GO_BUILDTAGS ?=
+GO_BUILDTAGS_LIMACTL := $(strip $(GO_BUILDTAGS) $(LIMACTL_DRIVER_TAGS))
+
 _output/bin/limactl$(exe): $(LIMACTL_DEPS) $$(call force_build,$$@)
-# If the previous cross-compilation was for GOOS=windows, limactl.exe might still be present.
 ifneq ($(GOOS),windows) #
 	@rm -rf _output/bin/limactl.exe
 else
 	@rm -rf _output/bin/limactl
 endif
-	$(ENVS_$@) $(GO_BUILD) -o $@ ./cmd/limactl
+	$(ENVS_$@) $(GO_BUILD) -tags '$(GO_BUILDTAGS_LIMACTL)' -o $@ ./cmd/limactl
 ifeq ($(GOOS),darwin)
 	codesign -f -v --entitlements vz.entitlements -s - $@
 endif
 
+DRIVER_INSTALL_DIR := _output/libexec/lima
+
+.PHONY: additional-drivers
+additional-drivers:
+	@mkdir -p $(DRIVER_INSTALL_DIR)
+	@for drv in $(ADDITIONAL_DRIVERS); do \
+		echo "Building $$drv as external"; \
+		$(GO_BUILD) -o $(DRIVER_INSTALL_DIR)/lima-driver-$$drv ./cmd/lima-driver-$$drv; \
+		if [ "$$drv" = "vz" ]; then \
+            codesign -f -v --entitlements vz.entitlements -s - $(DRIVER_INSTALL_DIR)/lima-driver-vz; \
+        fi; \
+	done
+
 LIMA_CMDS = $(sort lima lima$(bat)) # $(sort ...) deduplicates the list
 LIMA_DEPS = $(addprefix _output/bin/,$(LIMA_CMDS))
 lima: $(LIMA_DEPS)

cmd/lima-driver-qemu/main.go

@@ -0,0 +1,14 @@
+// SPDX-FileCopyrightText: Copyright The Lima Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package main
+
+import (
+	"github.com/lima-vm/lima/pkg/driver/external/server"
+	"github.com/lima-vm/lima/pkg/driver/qemu"
+)
+
+// To be used as an external driver for Lima.
+func main() {
+	server.Serve(qemu.New())
+}

cmd/lima-driver-vz/main.go

@@ -0,0 +1,16 @@
+//go:build darwin
+
+// SPDX-FileCopyrightText: Copyright The Lima Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package main
+
+import (
+	"github.com/lima-vm/lima/pkg/driver/external/server"
+	"github.com/lima-vm/lima/pkg/driver/vz"
+)
+
+// To be used as an external driver for Lima.
+func main() {
+	server.Serve(vz.New())
+}

cmd/lima-driver-wsl2/main.go

@@ -0,0 +1,16 @@
+//go:build windows
+
+// SPDX-FileCopyrightText: Copyright The Lima Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package main
+
+import (
+	"github.com/lima-vm/lima/pkg/driver/external/server"
+	"github.com/lima-vm/lima/pkg/driver/wsl2"
+)
+
+// To be used as an external driver for Lima.
+func main() {
+	server.Serve(wsl2.New())
+}

cmd/limactl/disk.go

@@ -13,11 +13,11 @@
 	"text/tabwriter"
 
 	contfs "github.com/containerd/continuity/fs"
 	"github.com/docker/go-units"
-	"github.com/lima-vm/go-qcow2reader"
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 
+	"github.com/lima-vm/go-qcow2reader"
 	"github.com/lima-vm/lima/pkg/imgutil/proxyimgutil"
 	"github.com/lima-vm/lima/pkg/store"
 	"github.com/lima-vm/lima/pkg/store/filenames"

cmd/limactl/main.go

@@ -16,6 +16,7 @@
 	"github.com/spf13/cobra"
 
 	"github.com/lima-vm/lima/pkg/debugutil"
+	"github.com/lima-vm/lima/pkg/driver/external/server"
 	"github.com/lima-vm/lima/pkg/fsutil"
 	"github.com/lima-vm/lima/pkg/osutil"
 	"github.com/lima-vm/lima/pkg/store/dirnames"
@@ -43,6 +44,8 @@
 		handleExitCoder(err)
 		logrus.Fatal(err)
 	}
+
+	defer server.StopAllExternalDrivers()
 }
 
 func newApp() *cobra.Command {

cmd/limactl/main_darwin.go

@@ -0,0 +1,9 @@
+//go:build !external_vz
+
+// SPDX-FileCopyrightText: Copyright The Lima Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package main
+
+// Import vz driver to register it in the registry on darwin.
+import _ "github.com/lima-vm/lima/pkg/driver/vz"

cmd/limactl/main_qemu.go

@@ -0,0 +1,9 @@
+//go:build !external_qemu
+
+// SPDX-FileCopyrightText: Copyright The Lima Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package main
+
+// Import qemu driver to register it in the registry on all platforms.
+import _ "github.com/lima-vm/lima/pkg/driver/qemu"

cmd/limactl/main_windows.go

@@ -0,0 +1,9 @@
+//go:build !external_wsl2
+
+// SPDX-FileCopyrightText: Copyright The Lima Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package main
+
+// Import wsl2 driver to register it in the registry on windows.
+import _ "github.com/lima-vm/lima/pkg/driver/wsl2"

cmd/limactl/start.go

@@ -21,6 +21,7 @@ import (
 	"github.com/lima-vm/lima/pkg/limatmpl"
 	"github.com/lima-vm/lima/pkg/limayaml"
 	networks "github.com/lima-vm/lima/pkg/networks/reconcile"
+	"github.com/lima-vm/lima/pkg/registry"
 	"github.com/lima-vm/lima/pkg/store"
 	"github.com/lima-vm/lima/pkg/store/filenames"
 	"github.com/lima-vm/lima/pkg/templatestore"
@@ -32,6 +33,7 @@ func registerCreateFlags(cmd *cobra.Command, commentPrefix string) {
 	flags := cmd.Flags()
 	flags.String("name", "", commentPrefix+"Override the instance name")
 	flags.Bool("list-templates", false, commentPrefix+"List available templates and exit")
+	flags.Bool("list-drivers", false, commentPrefix+"List available drivers and exit")
 	editflags.RegisterCreate(cmd, commentPrefix)
 }
 
@@ -54,6 +56,7 @@ $ limactl create --set='.cpus = 2 | .memory = "2GiB"'
 To see the template list:
 $ limactl create --list-templates
 
+
 To create an instance "default" from a local file:
 $ limactl create --name=default /usr/local/share/lima/templates/fedora.yaml
 
@@ -393,6 +396,14 @@ func createStartActionCommon(cmd *cobra.Command, _ []string) (exit bool, err err
 			_, _ = fmt.Fprintln(w, f.Name)
 		}
 		return true, nil
+	} else if listDrivers, err := cmd.Flags().GetBool("list-drivers"); err != nil {
+		return true, err
+	} else if listDrivers {
+		w := cmd.OutOrStdout()
+		for k := range registry.List() {
+			_, _ = fmt.Fprintln(w, k)
+		}
+		return true, nil
 	}
 	return false, nil
 }

pkg/driver/driver.go

@@ -5,17 +5,13 @@ package driver
 
 import (
 	"context"
-	"errors"
 	"net"
 
 	"github.com/lima-vm/lima/pkg/store"
 )
 
-// Driver interface is used by hostagent for managing vm.
-//
-// This interface is extended by BaseDriver which provides default implementation.
-// All other driver definition must extend BaseDriver.
-type Driver interface {
+// Lifecycle defines basic lifecycle operations.
+type Lifecycle interface {
 	// Validate returns error if the current driver isn't support for given config
 	Validate() error
 
@@ -35,120 +31,66 @@ type Driver interface {
 	// The second argument may contain error occurred while starting driver
 	Start(_ context.Context) (chan error, error)
 
-	// CanRunGUI returns bool to indicate if the hostagent need to run GUI synchronously
-	CanRunGUI() bool
-
-	// RunGUI is for starting GUI synchronously by hostagent. This method should be wait and return only after vm terminates
-	// It returns error if there are any failures
-	RunGUI() error
-
 	// Stop will terminate the running vm instance.
 	// It returns error if there are any errors during Stop
 	Stop(_ context.Context) error
-
-	// Register will add an instance to a registry.
-	// It returns error if there are any errors during Register
-	Register(_ context.Context) error
-
-	// Unregister will perform any cleanup related to the vm instance.
-	// It returns error if there are any errors during Unregister
-	Unregister(_ context.Context) error
-
-	ChangeDisplayPassword(_ context.Context, password string) error
-
-	GetDisplayConnection(_ context.Context) (string, error)
-
-	CreateSnapshot(_ context.Context, tag string) error
-
-	ApplySnapshot(_ context.Context, tag string) error
-
-	DeleteSnapshot(_ context.Context, tag string) error
-
-	ListSnapshots(_ context.Context) (string, error)
-
-	// ForwardGuestAgent returns if the guest agent sock needs forwarding by host agent.
-	ForwardGuestAgent() bool
-
-	// GuestAgentConn returns the guest agent connection, or nil (if forwarded by ssh).
-	GuestAgentConn(_ context.Context) (net.Conn, error)
-}
-
-type BaseDriver struct {
-	Instance *store.Instance
-
-	SSHLocalPort int
-	VSockPort    int
-	VirtioPort   string
-}
-
-var _ Driver = (*BaseDriver)(nil)
-
-func (d *BaseDriver) Validate() error {
-	return nil
-}
-
-func (d *BaseDriver) Initialize(_ context.Context) error {
-	return nil
-}
-
-func (d *BaseDriver) CreateDisk(_ context.Context) error {
-	return nil
-}
-
-func (d *BaseDriver) Start(_ context.Context) (chan error, error) {
-	return nil, nil
-}
-
-func (d *BaseDriver) CanRunGUI() bool {
-	return false
-}
-
-func (d *BaseDriver) RunGUI() error {
-	return nil
 }
 
-func (d *BaseDriver) Stop(_ context.Context) error {
-	return nil
-}
+// GUI defines GUI-related operations.
+type GUI interface {
+	// RunGUI is for starting GUI synchronously by hostagent. This method should be wait and return only after vm terminates
+	// It returns error if there are any failures
+	RunGUI() error
 
-func (d *BaseDriver) Register(_ context.Context) error {
-	return nil
+	ChangeDisplayPassword(ctx context.Context, password string) error
+	DisplayConnection(ctx context.Context) (string, error)
 }
 
-func (d *BaseDriver) Unregister(_ context.Context) error {
-	return nil
+// SnapshotManager defines operations for managing snapshots.
+type SnapshotManager interface {
+	CreateSnapshot(ctx context.Context, tag string) error
+	ApplySnapshot(ctx context.Context, tag string) error
+	DeleteSnapshot(ctx context.Context, tag string) error
+	ListSnapshots(ctx context.Context) (string, error)
 }
 
-func (d *BaseDriver) ChangeDisplayPassword(_ context.Context, _ string) error {
-	return nil
+// Registration defines operations for registering and unregistering the driver instance.
+type Registration interface {
+	Register(ctx context.Context) error
+	Unregister(ctx context.Context) error
 }
 
-func (d *BaseDriver) GetDisplayConnection(_ context.Context) (string, error) {
-	return "", nil
-}
+// GuestAgent defines operations for the guest agent.
+type GuestAgent interface {
+	// ForwardGuestAgent returns if the guest agent sock needs forwarding by host agent.
+	ForwardGuestAgent() bool
 
-func (d *BaseDriver) CreateSnapshot(_ context.Context, _ string) error {
-	return errors.New("unimplemented")
+	// GuestAgentConn returns the guest agent connection, or nil (if forwarded by ssh).
+	GuestAgentConn(_ context.Context) (net.Conn, string, error)
 }
 
-func (d *BaseDriver) ApplySnapshot(_ context.Context, _ string) error {
-	return errors.New("unimplemented")
-}
+// Driver interface is used by hostagent for managing vm.
+type Driver interface {
+	Lifecycle
+	GUI
+	SnapshotManager
+	Registration
+	GuestAgent
 
-func (d *BaseDriver) DeleteSnapshot(_ context.Context, _ string) error {
-	return errors.New("unimplemented")
-}
+	Info() Info
 
-func (d *BaseDriver) ListSnapshots(_ context.Context) (string, error) {
-	return "", errors.New("unimplemented")
+	// SetConfig sets the configuration for the instance.
+	Configure(inst *store.Instance, sshLocalPort int) *ConfiguredDriver
 }
 
-func (d *BaseDriver) ForwardGuestAgent() bool {
-	// if driver is not providing, use host agent
-	return d.VSockPort == 0 && d.VirtioPort == ""
+type ConfiguredDriver struct {
+	Driver
 }
 
-func (d *BaseDriver) GuestAgentConn(_ context.Context) (net.Conn, error) {
-	// use the unix socket forwarded by host agent
-	return nil, nil
+type Info struct {
+	DriverName  string `json:"driverName"`
+	CanRunGUI   bool   `json:"canRunGui,omitempty"`
+	VsockPort   int    `json:"vsockPort"`
+	VirtioPort  string `json:"virtioPort"`
+	InstanceDir string `json:"instanceDir,omitempty"`
 }