machine: Add GetMetadata and UpdateMetadata

GetMetadata and UpdateMetadata allow respectively allow retrieving and
updating the metadata available in the Firecracker MMDS.  UpdateMetadata
will merge new content with the existing content.  GetMetadata will
retrieve metadata into the provided struct, which should be annotated
with json struct tags.

Signed-off-by: Samuel Karp <[email protected]>

Author: Corbin Phelps

firecracker.go

@@ -15,9 +15,10 @@ package firecracker
 
 import (
 	"context"
-	"github.com/go-openapi/strfmt"
 	"time"
 
+	"github.com/go-openapi/strfmt"
+
 	"github.com/sirupsen/logrus"
 
 	"github.com/firecracker-microvm/firecracker-go-sdk/client"
@@ -234,6 +235,39 @@ func (f *Client) PutMmds(ctx context.Context, metadata interface{}, opts ...PutM
 	return f.client.Operations.PutMmds(params)
 }
 
+// GetMmdsOpt is a functional option to be used for the GetMmds API in setting
+// any additional optional fields.
+type GetMmdsOpt func(*ops.GetMmdsParams)
+
+// GetMmds is a wrapper for the swagger generated client to make calling of the
+// API easier.
+func (f *Client) GetMmds(ctx context.Context, opts ...GetMmdsOpt) (*ops.GetMmdsOK, error) {
+	params := ops.NewGetMmdsParams()
+	params.SetContext(ctx)
+	for _, opt := range opts {
+		opt(params)
+	}
+
+	return f.client.Operations.GetMmds(params)
+}
+
+// PatchMmdsOpt is a functional option to be used for the GetMmds API in setting
+// any additional optional fields.
+type PatchMmdsOpt func(*ops.PatchMmdsParams)
+
+// PatchMmds is a wrapper for the swagger generated client to make calling of the
+// API easier.
+func (f *Client) PatchMmds(ctx context.Context, metadata interface{}, opts ...PatchMmdsOpt) (*ops.PatchMmdsNoContent, error) {
+	params := ops.NewPatchMmdsParams()
+	params.SetContext(ctx)
+	params.SetBody(metadata)
+	for _, opt := range opts {
+		opt(params)
+	}
+
+	return f.client.Operations.PatchMmds(params)
+}
+
 // GetMachineConfigurationOpt  is a functional option to be used for the
 // GetMachineConfiguration API in setting any additional optional fields.
 type GetMachineConfigurationOpt func(*ops.GetMachineConfigurationParams)

machine.go

@@ -15,6 +15,7 @@ package firecracker
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -660,6 +661,40 @@ func (m *Machine) SetMetadata(ctx context.Context, metadata interface{}) error {
 	return nil
 }
 
+// UpdateMetadata patches the machine's metadata for MDDS
+func (m *Machine) UpdateMetadata(ctx context.Context, metadata interface{}) error {
+	if _, err := m.client.PatchMmds(ctx, metadata); err != nil {
+		m.logger.Errorf("Updating metadata: %s", err)
+		return err
+	}
+
+	m.logger.Printf("UpdateMetadata successful")
+	return nil
+}
+
+// GetMetadata gets the machine's metadata from MDDS and unmarshals it into v
+func (m *Machine) GetMetadata(ctx context.Context, v interface{}) error {
+	resp, err := m.client.GetMmds(ctx)
+	if err != nil {
+		m.logger.Errorf("Getting metadata: %s", err)
+		return err
+	}
+
+	payloadData, err := json.Marshal(resp.Payload)
+	if err != nil {
+		m.logger.Errorf("Getting metadata failed parsing payload: %s", err)
+		return err
+	}
+
+	if err := json.Unmarshal(payloadData, v); err != nil {
+		m.logger.Errorf("Getting metadata failed parsing payload: %s", err)
+		return err
+	}
+
+	m.logger.Printf("GetMetadata successful")
+	return nil
+}
+
 // UpdateGuestDrive will modify the current guest drive of ID index with the new
 // parameters of the partialDrive.
 func (m *Machine) UpdateGuestDrive(ctx context.Context, driveID, pathOnHost string, opts ...PatchGuestDriveByIDOpt) error {

machine_test.go

@@ -330,6 +330,8 @@ func TestMicroVMExecution(t *testing.T) {
 	t.Run("TestAttachSecondaryDrive", func(t *testing.T) { testAttachSecondaryDrive(ctx, t, m) })
 	t.Run("TestAttachVsock", func(t *testing.T) { testAttachVsock(ctx, t, m) })
 	t.Run("SetMetadata", func(t *testing.T) { testSetMetadata(ctx, t, m) })
+	t.Run("UpdateMetadata", func(t *testing.T) { testUpdateMetadata(ctx, t, m) })
+	t.Run("GetMetadata", func(t *testing.T) { testGetMetadata(ctx, t, m) }) // Should be after testSetMetadata and testUpdateMetadata
 	t.Run("TestUpdateGuestDrive", func(t *testing.T) { testUpdateGuestDrive(ctx, t, m) })
 	t.Run("TestUpdateGuestNetworkInterface", func(t *testing.T) { testUpdateGuestNetworkInterface(ctx, t, m) })
 	t.Run("TestStartInstance", func(t *testing.T) { testStartInstance(ctx, t, m) })
@@ -667,6 +669,28 @@ func testSetMetadata(ctx context.Context, t *testing.T, m *Machine) {
 	}
 }
 
+func testUpdateMetadata(ctx context.Context, t *testing.T, m *Machine) {
+	metadata := map[string]string{"patch_key": "patch_value"}
+	err := m.UpdateMetadata(ctx, metadata)
+	if err != nil {
+		t.Errorf("failed to set metadata: %s", err)
+	}
+}
+
+func testGetMetadata(ctx context.Context, t *testing.T, m *Machine) {
+	metadata := struct {
+		Key      string `json:"key"`
+		PatchKey string `json:"patch_key"`
+	}{}
+	if err := m.GetMetadata(ctx, &metadata); err != nil {
+		t.Errorf("failed to get metadata: %s", err)
+	}
+
+	if metadata.Key != "value" || metadata.PatchKey != "patch_value" {
+		t.Error("failed to get expected metadata values")
+	}
+}
+
 func TestLogFiles(t *testing.T) {
 	cfg := Config{
 		Debug:           true,