VMware: Fix guestinfo.*.config.data and *.config.url variables

The decision whether to use ignition.config.data or coreos.config.data
was based on their presence in ovfenv. If this was missing, coreos.config.data
would always be used. Also, if the retrieval of the guestinfo would have an error,
the value from ovfenv would not be used even though it was supposed to be a fallback.
Thus, refactor the logic to get variables from the ovfenv as fallback while preferring the
direct guestinfo variables. With this new function, fix the logic of falling back to
coreos.config.data but preferring ignition.config.data.

The OVF metadata for CoreOS specified guestinfo.coreos.config.url but that was
never used to fetch the Ignition config.
Thus, use guestinfo.*.config.url as fallback if no guestinfo.*.config.data variables are set.

internal/providers/vmware/vmware_amd64.go

@@ -18,6 +18,8 @@
 package vmware
 
 import (
+	"net/url"
+
 	"github.com/coreos/ignition/v2/config/v3_4_experimental/types"
 	"github.com/coreos/ignition/v2/internal/providers"
 	"github.com/coreos/ignition/v2/internal/providers/util"
@@ -26,7 +28,7 @@ import (
 	"github.com/coreos/vcontext/report"
 	"github.com/vmware/vmw-guestinfo/rpcvmx"
 	"github.com/vmware/vmw-guestinfo/vmcheck"
-	"github.com/vmware/vmw-ovflib"
+	ovf "github.com/vmware/vmw-ovflib"
 )
 
 func FetchConfig(f *resource.Fetcher) (types.Config, report.Report, error) {
@@ -36,26 +38,83 @@ func FetchConfig(f *resource.Fetcher) (types.Config, report.Report, error) {
 		return types.Config{}, report.Report{}, providers.ErrNoProvider
 	}
 
-	config, err := fetchRawConfig(f)
+	config, err := fetchDataConfig(f)
+	if err == nil && len(config) == 0 {
+		config, err = fetchUrlConfig(f)
+	}
 	if err != nil {
 		return types.Config{}, report.Report{}, err
 	}
 
-	decodedData, err := decodeConfig(config)
+	f.Logger.Debug("config successfully fetched")
+	return util.ParseConfig(f.Logger, config)
+}
+
+func fetchDataConfig(f *resource.Fetcher) ([]byte, error) {
+	var data string
+	var encoding string
+	var err error
+
+	data, err = getVariable(f, "ignition.config.data")
+	if err == nil && data != "" {
+		encoding, _ = getVariable(f, "ignition.config.data.encoding")
+	} else {
+		data, _ = getVariable(f, "coreos.config.data")
+		if err == nil && data != "" {
+			encoding, _ = getVariable(f, "coreos.config.data.encoding")
+		}
+	}
+	// Do not check against err from "encoding" because leaving it empty is ok
+	if data == "" {
+		f.Logger.Debug("failed to fetch config")
+		return []byte{}, nil
+	}
+
+	decodedData, err := decodeConfig(config{
+		data:     data,
+		encoding: encoding,
+	})
 	if err != nil {
 		f.Logger.Debug("failed to decode config: %v", err)
-		return types.Config{}, report.Report{}, err
+		return nil, err
 	}
 
-	f.Logger.Debug("config successfully fetched")
-	return util.ParseConfig(f.Logger, decodedData)
+	return decodedData, nil
 }
 
-func fetchRawConfig(f *resource.Fetcher) (config, error) {
+func fetchUrlConfig(f *resource.Fetcher) ([]byte, error) {
+	rawUrl, err := getVariable(f, "ignition.config.url")
+	if err != nil || rawUrl == "" {
+		rawUrl, err = getVariable(f, "coreos.config.url")
+	}
+	if err != nil || rawUrl == "" {
+		f.Logger.Info("no config URL provided")
+		return []byte{}, nil
+	}
+
+	f.Logger.Debug("found url: %q", rawUrl)
+
+	url, err := url.Parse(rawUrl)
+	if err != nil {
+		f.Logger.Err("failed to parse url: %v", err)
+		return nil, err
+	}
+	if url == nil {
+		return []byte{}, nil
+	}
+
+	data, err := f.FetchToBuffer(*url, resource.FetchOptions{})
+	if err != nil {
+		return nil, err
+	}
+
+	return data, nil
+}
+
+func getVariable(f *resource.Fetcher, key string) (string, error) {
 	info := rpcvmx.NewConfig()
 
 	var ovfData string
-	var ovfEncoding string
 
 	ovfEnv, err := info.String("ovfenv", "")
 	if err != nil {
@@ -65,26 +124,18 @@ func fetchRawConfig(f *resource.Fetcher) (config, error) {
 		env, err := ovf.ReadEnvironment([]byte(ovfEnv))
 		if err != nil {
 			f.Logger.Warning("failed to parse OVF environment: %v. Continuing...", err)
+		} else {
+			ovfData = env.Properties["guestinfo."+key]
 		}
-
-		ovfData = env.Properties["guestinfo.ignition.config.data"]
-		ovfEncoding = env.Properties["guestinfo.ignition.config.data.encoding"]
-	}
-
-	data, err := info.String("ignition.config.data", ovfData)
-	if err != nil {
-		f.Logger.Debug("failed to fetch config: %v", err)
-		return config{}, err
 	}
 
-	encoding, err := info.String("ignition.config.data.encoding", ovfEncoding)
+	// The guest variables get preference over the ovfenv variables which are given here as fallback
+	data, err := info.String(key, ovfData)
 	if err != nil {
-		f.Logger.Debug("failed to fetch config encoding: %v", err)
-		return config{}, err
+		f.Logger.Debug("failed to fetch variable, falling back to ovfenv value: %v", err)
+		return ovfData, nil
 	}
 
-	return config{
-		data:     data,
-		encoding: encoding,
-	}, nil
+	// An empty string will be returned if nothing was found
+	return data, nil
 }