add mounting of root partition

internal/providers/ionoscloud/ionoscloud.go

@@ -1,4 +1,4 @@
-// Copyright 2019 Red Hat, Inc.
+// Copyright 2024 Red Hat, Inc.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -19,18 +19,28 @@
 package ionoscloud
 
 import (
+	"context"
+	"fmt"
 	"os"
+	"os/exec"
+	"path/filepath"
+	"time"
 
 	"github.com/coreos/ignition/v2/config/v3_6_experimental/types"
+	"github.com/coreos/ignition/v2/internal/distro"
+	"github.com/coreos/ignition/v2/internal/log"
 	"github.com/coreos/ignition/v2/internal/platform"
 	"github.com/coreos/ignition/v2/internal/providers/util"
 	"github.com/coreos/ignition/v2/internal/resource"
+	ut "github.com/coreos/ignition/v2/internal/util"
 
 	"github.com/coreos/vcontext/report"
 )
 
 const (
-	defaultFilename = "/var/lib/cloud/seed/nocloud/user-data"
+	rootLabelEnvVar  = "IGNITION_CONFIG_ROOT_LABEL"
+	defaultRootLabel = "ROOT"
+	userDataPath     = "/var/lib/cloud/seed/nocloud/user-data"
 )
 
 func init() {
@@ -41,18 +51,93 @@ func init() {
 }
 
 func fetchConfig(f *resource.Fetcher) (types.Config, report.Report, error) {
-	f.Logger.Info("using config file at %q", defaultFilename)
+	var data []byte
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 
-	rawConfig, err := os.ReadFile(defaultFilename)
+	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()
+	}
+
+	deviceLabel := os.Getenv(rootLabelEnvVar)
+	if deviceLabel == "" {
+		deviceLabel = defaultRootLabel
+	}
+
+	go dispatch(
+		"load config from root partition", func() ([]byte, error) {
+			return fetchConfigFromDevice(f.Logger, ctx, filepath.Join(distro.DiskByLabelDir(), deviceLabel))
+		},
+	)
+
+	<-ctx.Done()
+	if ctx.Err() == context.DeadlineExceeded {
+		f.Logger.Info("root partition was not available in time. Continuing without a config...")
+	}
+
+	return util.ParseConfig(f.Logger, data)
+}
+
+func fileExists(path string) bool {
+	_, err := os.Stat(path)
+	return (err == nil)
+}
+
+func fetchConfigFromDevice(logger *log.Logger, ctx context.Context, device string) ([]byte, error) {
+	for !fileExists(device) {
+		logger.Debug("root partition (%q) not found. Waiting...", device)
+		select {
+		case <-time.After(time.Second):
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		}
+	}
+
+	logger.Debug("creating temporary mount point")
+	mnt, err := os.MkdirTemp("", "ignition-config")
+	if err != nil {
+		return nil, fmt.Errorf("failed to create temp directory: %v", err)
+	}
+	defer os.Remove(mnt)
+
+	cmd := exec.Command(distro.MountCmd(), "-o", "ro", "-t", "auto", device, mnt)
+	if _, err := logger.LogCmd(cmd, "mounting root partition"); err != nil {
+		return nil, err
+	}
+	defer func() {
+		_ = logger.LogOp(
+			func() error {
+				return ut.UmountPath(mnt)
+			},
+			"unmounting %q at %q", device, mnt,
+		)
+	}()
+
+	if !fileExists(filepath.Join(mnt, userDataPath)) {
+		return nil, nil
+	}
+
+	contents, err := os.ReadFile(filepath.Join(mnt, userDataPath))
 	if err != nil {
-		f.Logger.Err("couldn't read config %q: %v", defaultFilename, err)
-		return types.Config{}, report.Report{}, err
+		return nil, err
 	}
 
-	if util.IsCloudConfig(rawConfig) {
-		f.Logger.Debug("config drive (%q) contains a cloud-config configuration, ignoring", defaultFilename)
-		return types.Config{}, report.Report{}, err
+	if util.IsCloudConfig(contents) {
+		logger.Debug("root partition (%q) contains a cloud-config configuration, ignoring", device)
+		return nil, nil
 	}
 
-	return util.ParseConfig(f.Logger, rawConfig)
+	return contents, nil
 }