Add support for VGA console screenshots

cmd/incusd/instance_console.go

@@ -533,9 +533,10 @@ func instanceConsolePost(d *Daemon, r *http.Request) response.Response {
 
 // swagger:operation GET /1.0/instances/{name}/console instances instance_console_get
 //
-//	Get console log
+//	Get console output
 //
-//	Gets the console log for the instance.
+//	Gets the console output for the instance either as text log or as vga
+//	screendump.
 //
 //	---
 //	produces:
@@ -546,14 +547,27 @@ func instanceConsolePost(d *Daemon, r *http.Request) response.Response {
 //	    description: Project name
 //	    type: string
 //	    example: default
+//	  - in: query
+//	    name: type
+//	    description: Console type
+//	    type: string
+//	    enum: [log, vga]
+//	    default: log
+//	    example: vga
 //	responses:
 //	  "200":
-//	     description: Raw console log
+//	     description: |
+//	       Console output either as raw console log or as vga screendump in PNG
+//	       format depending on the `type` parameter provided with the request.
 //	     content:
 //	       application/octet-stream:
 //	         schema:
 //	           type: string
 //	           example: some-text
+//	       image/png:
+//	         schema:
+//	           type: string
+//	           format: binary
 //	  "400":
 //	    $ref: "#/responses/BadRequest"
 //	  "403":
@@ -576,6 +590,11 @@ func instanceConsoleLogGet(d *Daemon, r *http.Request) response.Response {
 		return response.SmartError(err)
 	}
 
+	consoleLogType := request.QueryParam(r, "type")
+	if consoleLogType != "" && consoleLogType != "log" && consoleLogType != "vga" {
+		return response.SmartError(fmt.Errorf("Invalid value for type parameter: %s", consoleLogType))
+	}
+
 	if internalInstance.IsSnapshot(name) {
 		return response.BadRequest(fmt.Errorf("Invalid instance name"))
 	}
@@ -649,16 +668,48 @@ func instanceConsoleLogGet(d *Daemon, r *http.Request) response.Response {
 			return response.SmartError(fmt.Errorf("Failed to cast inst to VM"))
 		}
 
-		logContents, err := v.ConsoleLog()
-		if err != nil {
-			return response.SmartError(err)
+		var headers map[string]string
+		if consoleLogType == "vga" {
+			screenshotFile, err := os.CreateTemp(v.Path(), "screenshot-*.png")
+			if err != nil {
+				return response.SmartError(fmt.Errorf("Couldn't create screenshot file: %w", err))
+			}
+
+			ent.Cleanup = func() {
+				_ = screenshotFile.Close()
+				_ = os.Remove(screenshotFile.Name())
+			}
+
+			err = v.ConsoleScreenshot(screenshotFile)
+			if err != nil {
+				return response.SmartError(err)
+			}
+
+			fileInfo, err := screenshotFile.Stat()
+			if err != nil {
+				return response.SmartError(fmt.Errorf("Couldn't stat screenshot file for filesize: %w", err))
+			}
+
+			headers = map[string]string{
+				"Content-Type": "image/png",
+			}
+
+			ent.File = screenshotFile
+			ent.FileSize = fileInfo.Size()
+			ent.Filename = screenshotFile.Name()
+		} else {
+			logContents, err := v.ConsoleLog()
+			if err != nil {
+				return response.SmartError(err)
+			}
+
+			ent.File = bytes.NewReader([]byte(logContents))
+			ent.FileSize = int64(len(logContents))
 		}
 
-		ent.File = bytes.NewReader([]byte(logContents))
 		ent.FileModified = time.Now()
-		ent.FileSize = int64(len(logContents))
 
-		return response.FileResponse(r, []response.FileResponseEntry{ent}, nil)
+		return response.FileResponse(r, []response.FileResponseEntry{ent}, headers)
 	}
 
 	return response.SmartError(fmt.Errorf("Unsupported instance type %q", inst.Type()))

doc/api-extensions.md

@@ -2660,3 +2660,7 @@ The following configuration options have been added:
 ## `storage_live_migration`
 
 This adds support for virtual-machines live-migration between storage pools.
+
+## `instance_console_screenshot`
+
+This adds support to take screenshots of the current VGA console of a VM.

doc/rest-api.yaml

@@ -9297,19 +9297,32 @@ paths:
             tags:
                 - instances
         get:
-            description: Gets the console log for the instance.
+            description: |-
+                Gets the console output for the instance either as text log or as vga
+                screendump.
             operationId: instance_console_get
             parameters:
                 - description: Project name
                   example: default
                   in: query
                   name: project
                   type: string
+                - default: log
+                  description: Console type
+                  enum:
+                    - log
+                    - vga
+                  example: vga
+                  in: query
+                  name: type
+                  type: string
             produces:
                 - application/json
             responses:
                 "200":
-                    description: Raw console log
+                    description: |
+                        Console output either as raw console log or as vga screendump in PNG
+                        format depending on the `type` parameter provided with the request.
                 "400":
                     $ref: '#/responses/BadRequest'
                 "403":
@@ -9318,7 +9331,7 @@ paths:
                     $ref: '#/responses/NotFound'
                 "500":
                     $ref: '#/responses/InternalServerError'
-            summary: Get console log
+            summary: Get console output
             tags:
                 - instances
         post:

internal/server/instance/drivers/driver_qemu.go

@@ -1637,6 +1637,13 @@ func (d *qemu) start(stateful bool, op *operationlock.InstanceOperation) error {
 			}
 		}
 
+		// Change ownership of main instance directory.
+		err = os.Chown(d.Path(), int(d.state.OS.UnprivUID), -1)
+		if err != nil {
+			op.Done(err)
+			return fmt.Errorf("Failed to chown instance path: %w", err)
+		}
+
 		// Change ownership of config directory files so they are accessible to the
 		// unprivileged qemu process so that the 9p share can work.
 		//
@@ -9438,3 +9445,29 @@ func (d *qemu) consoleSwapSocketWithRB() error {
 
 	return monitor.ChardevChange("console", qmp.ChardevChangeInfo{Type: "ringbuf"})
 }
+
+// ConsoleScreenshot returns a screenshot of the current VGA console in PNG format.
+func (d *qemu) ConsoleScreenshot(screenshotFile *os.File) error {
+	if !d.IsRunning() {
+		return fmt.Errorf("Instance is not running")
+	}
+
+	// Check if the agent is running.
+	monitor, err := qmp.Connect(d.monitorPath(), qemuSerialChardevName, d.getMonitorEventHandler(), d.QMPLogFilePath())
+	if err != nil {
+		return err
+	}
+
+	err = screenshotFile.Chown(int(d.state.OS.UnprivUID), -1)
+	if err != nil {
+		return fmt.Errorf("Failed to chown screenshot path: %w", err)
+	}
+
+	// Take the screenshot.
+	err = monitor.Screendump(screenshotFile.Name())
+	if err != nil {
+		return fmt.Errorf("Failed taking screenshot: %w", err)
+	}
+
+	return nil
+}

internal/server/instance/drivers/qmp/commands.go

@@ -1274,3 +1274,23 @@ func (m *Monitor) ChardevChange(device string, info ChardevChangeInfo) error {
 
 	return fmt.Errorf("Unsupported chardev type %q", info.Type)
 }
+
+// Screendump takes a screenshot of the current VGA console.
+// The screendump is stored to the filename provided as argument.
+func (m *Monitor) Screendump(filename string) error {
+	var args struct {
+		Filename string `json:"filename"`
+		Device   string `json:"device,omitempty"`
+		Head     int    `json:"head,omitempty"`
+		Format   string `json:"format,omitempty"`
+	}
+
+	args.Filename = filename
+	args.Format = "png"
+
+	var queryResp struct {
+		Return struct{} `json:"return"`
+	}
+
+	return m.Run("screendump", args, &queryResp)
+}

internal/server/instance/instance_interface.go

@@ -191,6 +191,7 @@ type VM interface {
 
 	AgentCertificate() *x509.Certificate
 	ConsoleLog() (string, error)
+	ConsoleScreenshot(screenshotFile *os.File) error
 }
 
 // CriuMigrationArgs arguments for CRIU migration.

internal/server/response/response.go

@@ -357,7 +357,6 @@ func (r *errorResponse) Render(w http.ResponseWriter) error {
 	}
 
 	err := json.NewEncoder(output).Encode(resp)
-
 	if err != nil {
 		return err
 	}
@@ -452,7 +451,11 @@ func (r *fileResponse) Render(w http.ResponseWriter) error {
 			rs = f
 		}
 
-		w.Header().Set("Content-Type", "application/octet-stream")
+		// Only set Content-Type header if it is still set to the default or not yet set at all.
+		if w.Header().Get("Content-Type") == "application/json" || w.Header().Get("Content-Type") == "" {
+			w.Header().Set("Content-Type", "application/octet-stream")
+		}
+
 		w.Header().Set("Content-Length", fmt.Sprintf("%d", sz))
 		w.Header().Set("Content-Disposition", fmt.Sprintf("inline;filename=%s", r.files[0].Filename))
 

internal/version/api.go

@@ -452,6 +452,7 @@ var APIExtensions = []string{
 	"custom_volume_refresh_exclude_older_snapshots",
 	"storage_initial_owner",
 	"storage_live_migration",
+	"instance_console_screenshot",
 }
 
 // APIExtensionsCount returns the number of available API extensions.