*: add support for cloudstack config-drive

Co-Authored-By: Frank Maximus <frank.maximus@nuagenetworks.net>

Upstream PR: apache/cloudstack#2097
Design document: https://cwiki.apache.org/confluence/display/CLOUDSTACK/Using+ConfigDrive+for+Metadata%2C+Userdata+and+Password

Author: fmaximus

internal/oem/oem.go

@@ -22,6 +22,7 @@ import (
 	"github.com/coreos/ignition/internal/log"
 	"github.com/coreos/ignition/internal/providers"
 	"github.com/coreos/ignition/internal/providers/azure"
+	"github.com/coreos/ignition/internal/providers/cloudstack"
 	"github.com/coreos/ignition/internal/providers/digitalocean"
 	"github.com/coreos/ignition/internal/providers/ec2"
 	"github.com/coreos/ignition/internal/providers/file"
@@ -98,10 +99,6 @@ func init() {
 		name:  "cloudsigma",
 		fetch: noop.FetchConfig,
 	})
-	configs.Register(Config{
-		name:  "cloudstack",
-		fetch: noop.FetchConfig,
-	})
 	configs.Register(Config{
 		name:  "digitalocean",
 		fetch: digitalocean.FetchConfig,
@@ -138,6 +135,10 @@ func init() {
 			},
 		},
 	})
+	configs.Register(Config{name: "cloudstack",
+		fetch:             cloudstack.FetchConfig,
+		defaultUserConfig: types.Config{Systemd: types.Systemd{Units: []types.Unit{userCloudInit("CloudStack", "cloudstack")}}},
+	})
 	configs.Register(Config{
 		name:       "ec2",
 		fetch:      ec2.FetchConfig,

internal/providers/cloudstack/cloudstack.go

@@ -0,0 +1,137 @@
+// Copyright 2017 CoreOS, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// The CloudStack provider fetches configurations from the userdata available in
+// the config-drive.
+// NOTE: This provider is still EXPERIMENTAL.
+
+package cloudstack
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"syscall"
+	"time"
+
+	"github.com/coreos/ignition/config"
+	"github.com/coreos/ignition/config/types"
+	"github.com/coreos/ignition/config/validate/report"
+	"github.com/coreos/ignition/internal/log"
+	"github.com/coreos/ignition/internal/resource"
+
+	"golang.org/x/net/context"
+)
+
+const (
+	diskByLabelPath         = "/dev/disk/by-label/"
+	configDriveUserdataPath = "/cloudstack/userdata/user_data.txt"
+)
+
+func FetchConfig(f resource.Fetcher) (types.Config, report.Report, error) {
+	var data []byte
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+
+	dispatch := func(name string, fn func() ([]byte, error)) {
+		raw, err := fn()
+		if err != nil {
+			switch err {
+			case context.Canceled:
+			case context.DeadlineExceeded:
+				f.Logger.Err("timed out while fetching config from %s", name)
+			default:
+				f.Logger.Err("failed to fetch config from %s: %v", name, err)
+			}
+			return
+		}
+
+		data = raw
+		cancel()
+	}
+
+	go dispatch("config drive (config)", func() ([]byte, error) {
+		return fetchConfigFromDevice(f.Logger, ctx, "config-2")
+	})
+
+	go dispatch("config drive (CONFIG)", func() ([]byte, error) {
+		return fetchConfigFromDevice(f.Logger, ctx, "CONFIG-2")
+	})
+
+	<-ctx.Done()
+	if ctx.Err() == context.DeadlineExceeded {
+		f.Logger.Info("Config drive was not available in time. Continuing without a config...")
+	}
+
+	return config.Parse(data)
+}
+
+func fileExists(path string) bool {
+	_, err := os.Stat(path)
+	return (err == nil)
+}
+
+func labelExists(label string) bool {
+	_, err := getPath(label)
+	return (err == nil)
+}
+
+func getPath(label string) (string, error) {
+	path := diskByLabelPath + label
+
+	if fileExists(path) {
+		return path, nil
+	}
+
+	return "", fmt.Errorf("label not found: %s", label)
+}
+
+func fetchConfigFromDevice(logger *log.Logger, ctx context.Context, label string) ([]byte, error) {
+	for !labelExists(label) {
+		logger.Debug("config drive (%q) not found. Waiting...", label)
+		select {
+		case <-time.After(time.Second):
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		}
+	}
+
+	path, err := getPath(label)
+	if err != nil {
+		return nil, err
+	}
+
+	logger.Debug("creating temporary mount point")
+	mnt, err := ioutil.TempDir("", "ignition-configdrive")
+	if err != nil {
+		return nil, fmt.Errorf("failed to create temp directory: %v", err)
+	}
+	defer os.Remove(mnt)
+
+	cmd := exec.Command("/bin/mount", "-o", "ro", "-t", "auto", path, mnt)
+	if _, err := logger.LogCmd(cmd, "mounting config drive"); err != nil {
+		return nil, err
+	}
+	defer logger.LogOp(
+		func() error { return syscall.Unmount(mnt, 0) },
+		"unmounting %q at %q", path, mnt,
+	)
+
+	if !fileExists(filepath.Join(mnt, configDriveUserdataPath)) {
+		return nil, nil
+	}
+
+	return ioutil.ReadFile(filepath.Join(mnt, configDriveUserdataPath))
+}