openstack: dynamically mount the config-drive

When we want to use config-drive in immutable systems, very often the
config-drive is only used at boot and then umounted (e.g. ignition does
this).

Later when we want to fetch Metadata from the config drive, we actually
have to mount it.

In this PR, I'm adding similar code than coreos/ignition where we
dynamically mount the config-drive is the device was found with the
right label (config-2 or CONFIG-2 as documented in OpenStack). If the
device is found, we mount it, fetch the data and umount it.

Author: EmilienM

pkg/platforms/openstack/openstack.go

@@ -5,6 +5,8 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"os/exec"
+	"path/filepath"
 	"strconv"
 	"strings"
 
@@ -21,15 +23,18 @@ import (
 )
 
 const (
-	ospHostMetaDataDir     = "/host/var/config/openstack/2018-08-27"
-	ospMetaDataDir         = "/var/config/openstack/2018-08-27"
-	ospMetaDataBaseURL     = "http://169.254.169.254/openstack/2018-08-27"
-	ospNetworkDataJSON     = "network_data.json"
-	ospMetaDataJSON        = "meta_data.json"
-	ospHostNetworkDataFile = ospHostMetaDataDir + "/" + ospNetworkDataJSON
-	ospHostMetaDataFile    = ospHostMetaDataDir + "/" + ospMetaDataJSON
-	ospNetworkDataURL      = ospMetaDataBaseURL + "/" + ospNetworkDataJSON
-	ospMetaDataURL         = ospMetaDataBaseURL + "/" + ospMetaDataJSON
+	varConfigPath      = "/var/config"
+	ospMetaDataBaseDir = "/openstack/2018-08-27"
+	ospMetaDataDir     = varConfigPath + ospMetaDataBaseDir
+	ospMetaDataBaseURL = "http://169.254.169.254" + ospMetaDataBaseDir
+	ospNetworkDataJSON = "network_data.json"
+	ospMetaDataJSON    = "meta_data.json"
+	ospNetworkDataURL  = ospMetaDataBaseURL + "/" + ospNetworkDataJSON
+	ospMetaDataURL     = ospMetaDataBaseURL + "/" + ospMetaDataJSON
+	// Config drive is defined as an iso9660 or vfat (deprecated) drive
+	// with the "config-2" label.
+	//https://docs.openstack.org/nova/latest/user/config-drive.html
+	configDriveLabel = "config-2"
 )
 
 var (
@@ -109,9 +114,10 @@ func New(hostManager host.HostManagerInterface) OpenstackInterface {
 }
 
 // GetOpenstackData gets the metadata and network_data
-func getOpenstackData(useHostPath bool) (metaData *OSPMetaData, networkData *OSPNetworkData, err error) {
-	metaData, networkData, err = getOpenstackDataFromConfigDrive(useHostPath)
+func getOpenstackData(mountConfigDrive bool) (metaData *OSPMetaData, networkData *OSPNetworkData, err error) {
+	metaData, networkData, err = getOpenstackDataFromConfigDrive(mountConfigDrive)
 	if err != nil {
+		log.Log.Error(err, "GetOpenStackData(): non-fatal error getting OpenStack data from config drive")
 		metaData, networkData, err = getOpenstackDataFromMetadataService()
 		if err != nil {
 			return metaData, networkData, fmt.Errorf("GetOpenStackData(): error getting OpenStack data: %w", err)
@@ -153,46 +159,109 @@ func getOpenstackData(useHostPath bool) (metaData *OSPMetaData, networkData *OSP
 	return metaData, networkData, err
 }
 
+// getConfigDriveDevice returns the config drive device which was found
+func getConfigDriveDevice() (string, error) {
+	dev := "/dev/disk/by-label/" + configDriveLabel
+	if _, err := os.Stat(dev); os.IsNotExist(err) {
+		out, err := exec.Command(
+			"blkid", "-l",
+			"-t", "LABEL="+configDriveLabel,
+			"-o", "device",
+		).CombinedOutput()
+		if err != nil {
+			return "", fmt.Errorf("unable to run blkid: %v", err)
+		}
+		dev = strings.TrimSpace(string(out))
+	}
+	log.Log.Info("found config drive device", "device", dev)
+	return dev, nil
+}
+
+// mountConfigDriveDevice mounts the config drive and return the path
+func mountConfigDriveDevice(device string) (string, error) {
+	if device == "" {
+		return "", fmt.Errorf("device is empty")
+	}
+	tmpDir, err := os.MkdirTemp("", "sriov-configdrive")
+	if err != nil {
+		return "", fmt.Errorf("error creating temp directory: %w", err)
+	}
+	cmd := exec.Command("mount", "-o", "ro", "-t", "auto", device, tmpDir)
+	if err := cmd.Run(); err != nil {
+		return "", fmt.Errorf("error mounting config drive: %w", err)
+	}
+	log.Log.V(2).Info("mounted config drive device", "device", device, "path", tmpDir)
+	return tmpDir, nil
+}
+
+// ummountConfigDriveDevice ummounts the config drive device
+func ummountConfigDriveDevice(path string) error {
+	if path == "" {
+		return fmt.Errorf("path is empty")
+	}
+	cmd := exec.Command("umount", path)
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("error umounting config drive: %w", err)
+	}
+	log.Log.V(2).Info("umounted config drive", "path", path)
+	return nil
+}
+
 // getOpenstackDataFromConfigDrive reads the meta_data and network_data files
-func getOpenstackDataFromConfigDrive(useHostPath bool) (metaData *OSPMetaData, networkData *OSPNetworkData, err error) {
+func getOpenstackDataFromConfigDrive(mountConfigDrive bool) (metaData *OSPMetaData, networkData *OSPNetworkData, err error) {
 	metaData = &OSPMetaData{}
 	networkData = &OSPNetworkData{}
+	var configDrivePath string
 	log.Log.Info("reading OpenStack meta_data from config-drive")
 	var metadataf *os.File
 	ospMetaDataFilePath := ospMetaDataFile
-	if useHostPath {
-		ospMetaDataFilePath = ospHostMetaDataFile
+	if mountConfigDrive {
+		configDriveDevice, err := getConfigDriveDevice()
+		if err != nil {
+			return metaData, networkData, fmt.Errorf("error finding config drive device: %w", err)
+		}
+		configDrivePath, err = mountConfigDriveDevice(configDriveDevice)
+		if err != nil {
+			return metaData, networkData, fmt.Errorf("error mounting config drive device: %w", err)
+		}
+		defer func() {
+			if e := ummountConfigDriveDevice(configDrivePath); err == nil && e != nil {
+				err = fmt.Errorf("error umounting config drive device: %w", e)
+			}
+			if e := os.Remove(configDrivePath); err == nil && e != nil {
+				err = fmt.Errorf("error removing temp directory %s: %w", configDrivePath, e)
+			}
+		}()
+		ospMetaDataFilePath = filepath.Join(configDrivePath, ospMetaDataBaseDir, ospMetaDataJSON)
+		ospNetworkDataFile = filepath.Join(configDrivePath, ospMetaDataBaseDir, ospNetworkDataJSON)
 	}
 	metadataf, err = os.Open(ospMetaDataFilePath)
 	if err != nil {
-		return metaData, networkData, fmt.Errorf("error opening file %s: %w", ospHostMetaDataFile, err)
+		return metaData, networkData, fmt.Errorf("error opening file %s: %w", ospMetaDataFilePath, err)
 	}
 	defer func() {
 		if e := metadataf.Close(); err == nil && e != nil {
-			err = fmt.Errorf("error closing file %s: %w", ospHostMetaDataFile, e)
+			err = fmt.Errorf("error closing file %s: %w", ospMetaDataFilePath, e)
 		}
 	}()
 	if err = json.NewDecoder(metadataf).Decode(&metaData); err != nil {
-		return metaData, networkData, fmt.Errorf("error unmarshalling metadata from file %s: %w", ospHostMetaDataFile, err)
+		return metaData, networkData, fmt.Errorf("error unmarshalling metadata from file %s: %w", ospMetaDataFilePath, err)
 	}
 
 	log.Log.Info("reading OpenStack network_data from config-drive")
 	var networkDataf *os.File
 	ospNetworkDataFilePath := ospNetworkDataFile
-	if useHostPath {
-		ospNetworkDataFilePath = ospHostNetworkDataFile
-	}
 	networkDataf, err = os.Open(ospNetworkDataFilePath)
 	if err != nil {
-		return metaData, networkData, fmt.Errorf("error opening file %s: %w", ospHostNetworkDataFile, err)
+		return metaData, networkData, fmt.Errorf("error opening file %s: %w", ospNetworkDataFilePath, err)
 	}
 	defer func() {
 		if e := networkDataf.Close(); err == nil && e != nil {
-			err = fmt.Errorf("error closing file %s: %w", ospHostNetworkDataFile, e)
+			err = fmt.Errorf("error closing file %s: %w", ospNetworkDataFilePath, e)
 		}
 	}()
 	if err = json.NewDecoder(networkDataf).Decode(&networkData); err != nil {
-		return metaData, networkData, fmt.Errorf("error unmarshalling metadata from file %s: %w", ospHostNetworkDataFile, err)
+		return metaData, networkData, fmt.Errorf("error unmarshalling metadata from file %s: %w", ospNetworkDataFilePath, err)
 	}
 	return metaData, networkData, err
 }