Restore guest agent unix socket functionality

Make both vsock and virtio explicit, instead of hardcoding
internal filenames in the agents. Fallback to to the unix.

Signed-off-by: Anders F Björklund <anders.f.bjorklund@gmail.com>

cmd/lima-guestagent/daemon_linux.go

@@ -11,7 +11,6 @@ import (
 	"github.com/lima-vm/lima/pkg/guestagent"
 	"github.com/lima-vm/lima/pkg/guestagent/api/server"
 	"github.com/lima-vm/lima/pkg/guestagent/serialport"
-	"github.com/lima-vm/lima/pkg/store/filenames"
 	"github.com/mdlayher/vsock"
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
@@ -25,21 +24,23 @@ func newDaemonCommand() *cobra.Command {
 	}
 	daemonCommand.Flags().Duration("tick", 3*time.Second, "tick for polling events")
 	daemonCommand.Flags().Int("vsock-port", 0, "use vsock server instead a UNIX socket")
+	daemonCommand.Flags().String("virtio-port", "", "use virtio server instead a UNIX socket")
 	return daemonCommand
 }
 
 func daemonAction(cmd *cobra.Command, _ []string) error {
+	socket := "/run/lima-guestagent.sock"
 	tick, err := cmd.Flags().GetDuration("tick")
 	if err != nil {
 		return err
 	}
-	vSockPortOverride, err := cmd.Flags().GetInt("vsock-port")
+	vSockPort, err := cmd.Flags().GetInt("vsock-port")
 	if err != nil {
 		return err
 	}
-	vSockPort := 0
-	if vSockPortOverride != 0 {
-		vSockPort = vSockPortOverride
+	virtioPort, err := cmd.Flags().GetString("virtio-port")
+	if err != nil {
+		return err
 	}
 	if tick == 0 {
 		return errors.New("tick must be specified")
@@ -67,11 +68,14 @@ func daemonAction(cmd *cobra.Command, _ []string) error {
 	r := mux.NewRouter()
 	server.AddRoutes(r, backend)
 	srv := &http.Server{Handler: r}
+	err = os.RemoveAll(socket)
+	if err != nil {
+		return err
+	}
 
 	var l net.Listener
-	virtioPort := "/dev/virtio-ports/" + filenames.VirtioPort
-	if _, err := os.Stat(virtioPort); err == nil {
-		qemuL, err := serialport.Listen(virtioPort)
+	if virtioPort != "" {
+		qemuL, err := serialport.Listen("/dev/virtio-ports/" + virtioPort)
 		if err != nil {
 			return err
 		}
@@ -84,6 +88,16 @@ func daemonAction(cmd *cobra.Command, _ []string) error {
 		}
 		l = vsockL
 		logrus.Infof("serving the guest agent on vsock port: %d", vSockPort)
+	} else {
+		socketL, err := net.Listen("unix", socket)
+		if err != nil {
+			return err
+		}
+		if err := os.Chmod(socket, 0o777); err != nil {
+			return err
+		}
+		l = socketL
+		logrus.Infof("serving the guest agent on %q", socket)
 	}
 	return srv.Serve(l)
 }

pkg/cidata/cidata.TEMPLATE.d/boot/25-guestagent-base.sh

@@ -28,7 +28,7 @@ name="lima-guestagent"
 description="Forward ports to the lima-hostagent"
 
 command=${LIMA_CIDATA_GUEST_INSTALL_PREFIX}/bin/lima-guestagent
-command_args="daemon --vsock-port "${LIMA_CIDATA_VSOCK_PORT}""
+command_args="daemon --vsock-port "${LIMA_CIDATA_VSOCK_PORT}" --virtio-port "${LIMA_CIDATA_VIRTIO_PORT}""
 command_background=true
 pidfile="/run/lima-guestagent.pid"
 EOF
@@ -40,5 +40,11 @@ else
 	# Remove legacy systemd service
 	rm -f "${LIMA_CIDATA_HOME}/.config/systemd/user/lima-guestagent.service"
 
-	sudo "${LIMA_CIDATA_GUEST_INSTALL_PREFIX}"/bin/lima-guestagent install-systemd --vsock-port "${LIMA_CIDATA_VSOCK_PORT}"
+	if [ "${LIMA_CIDATA_VSOCK_PORT}" != "0" ]; then
+		sudo "${LIMA_CIDATA_GUEST_INSTALL_PREFIX}"/bin/lima-guestagent install-systemd --vsock-port "${LIMA_CIDATA_VSOCK_PORT}"
+	elif [ "${LIMA_CIDATA_VIRTIO_PORT}" != "" ]; then
+		sudo "${LIMA_CIDATA_GUEST_INSTALL_PREFIX}"/bin/lima-guestagent install-systemd --virtio-port "${LIMA_CIDATA_VIRTIO_PORT}"
+	else
+		sudo "${LIMA_CIDATA_GUEST_INSTALL_PREFIX}"/bin/lima-guestagent install-systemd
+	fi
 fi

pkg/cidata/cidata.TEMPLATE.d/lima.env

@@ -41,6 +41,7 @@ LIMA_CIDATA_SKIP_DEFAULT_DEPENDENCY_RESOLUTION=
 {{- end}}
 LIMA_CIDATA_VMTYPE={{ .VMType }}
 LIMA_CIDATA_VSOCK_PORT={{ .VSockPort }}
+LIMA_CIDATA_VIRTIO_PORT={{ .VirtioPort}}
 {{- if .Plain}}
 LIMA_CIDATA_PLAIN=1
 {{- else}}

pkg/cidata/cidata.go

@@ -110,7 +110,7 @@ func setupEnv(y *limayaml.LimaYAML, args TemplateArgs) (map[string]string, error
 	return env, nil
 }
 
-func GenerateISO9660(instDir, name string, y *limayaml.LimaYAML, udpDNSLocalPort, tcpDNSLocalPort int, nerdctlArchive string, vsockPort int) error {
+func GenerateISO9660(instDir, name string, y *limayaml.LimaYAML, udpDNSLocalPort, tcpDNSLocalPort int, nerdctlArchive string, vsockPort int, virtioPort string) error {
 	if err := limayaml.Validate(*y, false); err != nil {
 		return err
 	}
@@ -135,6 +135,7 @@ func GenerateISO9660(instDir, name string, y *limayaml.LimaYAML, udpDNSLocalPort
 		RosettaBinFmt:  *y.Rosetta.BinFmt,
 		VMType:         *y.VMType,
 		VSockPort:      vsockPort,
+		VirtioPort:     virtioPort,
 		Plain:          *y.Plain,
 	}
 

pkg/cidata/template.go

@@ -81,6 +81,7 @@ type TemplateArgs struct {
 	SkipDefaultDependencyResolution bool
 	VMType                          string
 	VSockPort                       int
+	VirtioPort                      string
 	Plain                           bool
 }
 

pkg/driver/driver.go

@@ -64,6 +64,10 @@ type Driver interface {
 
 	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)
 }
 
@@ -73,6 +77,7 @@ type BaseDriver struct {
 
 	SSHLocalPort int
 	VSockPort    int
+	VirtioPort   string
 }
 
 var _ Driver = (*BaseDriver)(nil)
@@ -137,6 +142,12 @@ func (d *BaseDriver) ListSnapshots(_ context.Context) (string, error) {
 	return "", fmt.Errorf("unimplemented")
 }
 
+func (d *BaseDriver) ForwardGuestAgent() bool {
+	// if driver is not providing, use host agent
+	return d.VSockPort == 0 && d.VirtioPort == ""
+}
+
 func (d *BaseDriver) GuestAgentConn(_ context.Context) (net.Conn, error) {
-	return nil, fmt.Errorf("unimplemented")
+	// use the unix socket forwarded by host agent
+	return nil, nil
 }

pkg/hostagent/hostagent.go

@@ -53,7 +53,8 @@ type HostAgent struct {
 	eventEnc   *json.Encoder
 	eventEncMu sync.Mutex
 
-	vSockPort int
+	vSockPort  int
+	virtioPort string
 
 	clientMu sync.RWMutex
 	client   guestagentclient.GuestAgentClient
@@ -117,6 +118,7 @@ func New(instName string, stdout io.Writer, sigintCh chan os.Signal, opts ...Opt
 	}
 
 	vSockPort := 0
+	virtioPort := ""
 	if *y.VMType == limayaml.VZ {
 		vSockPort = 2222
 	} else if *y.VMType == limayaml.WSL2 {
@@ -125,9 +127,11 @@ func New(instName string, stdout io.Writer, sigintCh chan os.Signal, opts ...Opt
 			logrus.WithError(err).Error("failed to get free VSock port")
 		}
 		vSockPort = port
+	} else if *y.VMType == limayaml.QEMU {
+		virtioPort = filenames.VirtioPort
 	}
 
-	if err := cidata.GenerateISO9660(inst.Dir, instName, y, udpDNSLocalPort, tcpDNSLocalPort, o.nerdctlArchive, vSockPort); err != nil {
+	if err := cidata.GenerateISO9660(inst.Dir, instName, y, udpDNSLocalPort, tcpDNSLocalPort, o.nerdctlArchive, vSockPort, virtioPort); err != nil {
 		return nil, err
 	}
 
@@ -160,6 +164,7 @@ func New(instName string, stdout io.Writer, sigintCh chan os.Signal, opts ...Opt
 		Yaml:         y,
 		SSHLocalPort: sshLocalPort,
 		VSockPort:    vSockPort,
+		VirtioPort:   virtioPort,
 	})
 
 	a := &HostAgent{
@@ -176,6 +181,7 @@ func New(instName string, stdout io.Writer, sigintCh chan os.Signal, opts ...Opt
 		sigintCh:          sigintCh,
 		eventEnc:          json.NewEncoder(stdout),
 		vSockPort:         vSockPort,
+		virtioPort:        virtioPort,
 		guestAgentAliveCh: make(chan struct{}),
 	}
 	return a, nil
@@ -561,6 +567,9 @@ func (a *HostAgent) watchGuestAgentEvents(ctx context.Context) {
 		}
 	}
 
+	localUnix := filepath.Join(a.instDir, filenames.GuestAgentSock)
+	remoteUnix := "/run/lima-guestagent.sock"
+
 	a.onClose = append(a.onClose, func() error {
 		logrus.Debugf("Stop forwarding unix sockets")
 		var errs []error
@@ -573,9 +582,19 @@ func (a *HostAgent) watchGuestAgentEvents(ctx context.Context) {
 				}
 			}
 		}
+		if a.driver.ForwardGuestAgent() {
+			if err := forwardSSH(context.Background(), a.sshConfig, a.sshLocalPort, localUnix, remoteUnix, verbCancel, false); err != nil {
+				errs = append(errs, err)
+			}
+		}
 		return errors.Join(errs...)
 	})
 	for {
+		if a.client == nil || !isGuestAgentSocketAccessible(ctx, a.client) {
+			if a.driver.ForwardGuestAgent() {
+				_ = forwardSSH(ctx, a.sshConfig, a.sshLocalPort, localUnix, remoteUnix, verbForward, false)
+			}
+		}
 		client, err := a.getOrCreateClient(ctx)
 		if err == nil {
 			if err := a.processGuestAgentEvents(ctx, client); err != nil {
@@ -610,8 +629,18 @@ func (a *HostAgent) getOrCreateClient(ctx context.Context) (guestagentclient.Gue
 	return a.client, err
 }
 
-func (a *HostAgent) createClient(ctx context.Context) (guestagentclient.GuestAgentClient, error) {
+func (a *HostAgent) createConnection(ctx context.Context) (net.Conn, error) {
 	conn, err := a.driver.GuestAgentConn(ctx)
+	// default to forwarded sock
+	if conn == nil && err == nil {
+		var d net.Dialer
+		conn, err = d.DialContext(ctx, "unix", filepath.Join(a.instDir, filenames.GuestAgentSock))
+	}
+	return conn, err
+}
+
+func (a *HostAgent) createClient(ctx context.Context) (guestagentclient.GuestAgentClient, error) {
+	conn, err := a.createConnection(ctx)
 	if err != nil {
 		return nil, err
 	}

website/content/en/docs/dev/Internals/_index.md

@@ -72,10 +72,12 @@ VNC:
 
 Guest agent:
 
-Each drivers use their own mode of communication 
+Each drivers use their own mode of communication
 - `qemu`: uses virtio-port `io.lima-vm.guest_agent.0`
 - `vz`: uses vsock port 2222
 - `wsl2`: uses free random vsock port
+The fallback is to use port forward over ssh port
+- `ga.sock`: Forwarded to `/run/lima-guestagent.sock` in the guest, via SSH
 
 Host agent:
 - `ha.pid`: hostagent PID