feat(proc-cmdline): Parse /proc/cmdline for cloud-config-url

If the --from-proc-cmdline flag is given to coreos-cloudinit, the local
/proc/cmdline file will be parsed for a cloud-config-url

coreos-cloudinit.go

@@ -26,6 +26,9 @@ func main() {
 	var url string
 	flag.StringVar(&url, "from-url", "", "Download user-data from provided url")
 
+	var useProcCmdline bool
+	flag.BoolVar(&useProcCmdline, "from-proc-cmdline", false, fmt.Sprintf("Parse %s for '%s=<url>', using the cloud-config served by an HTTP GET to <url>", datasource.ProcCmdlineLocation, datasource.ProcCmdlineCloudConfigFlag))
+
 	var workspace string
 	flag.StringVar(&workspace, "workspace", "/var/lib/coreos-cloudinit", "Base directory coreos-cloudinit should use to store data")
 
@@ -39,8 +42,8 @@ func main() {
 		os.Exit(0)
 	}
 
-	if file != "" && url != "" {
-		fmt.Println("Provide one of --from-file or --from-url")
+	if file != "" && url != "" && !useProcCmdline {
+		fmt.Println("Provide one of --from-file, --from-url or --from-proc-cmdline")
 		os.Exit(1)
 	}
 
@@ -49,8 +52,10 @@ func main() {
 		ds = datasource.NewLocalFile(file)
 	} else if url != "" {
 		ds = datasource.NewMetadataService(url)
+	} else if useProcCmdline {
+		ds = datasource.NewProcCmdline()
 	} else {
-		fmt.Println("Provide one of --from-file or --from-url")
+		fmt.Println("Provide one of --from-file, --from-url or --from-proc-cmdline")
 		os.Exit(1)
 	}
 

datasource/datasource.go

@@ -1,6 +1,31 @@
 package datasource
 
+import (
+	"io/ioutil"
+	"net/http"
+)
+
 type Datasource interface {
 	Fetch() ([]byte, error)
 	Type()  string
 }
+
+func fetchURL(url string) ([]byte, error) {
+	client := http.Client{}
+	resp, err := client.Get(url)
+	if err != nil {
+		return []byte{}, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode / 100 != 2 {
+		return []byte{}, nil
+	}
+
+	respBytes, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	return respBytes, nil
+}

datasource/metadata_service.go

@@ -1,36 +1,15 @@
 package datasource
 
-import (
-	"io/ioutil"
-	"net/http"
-)
-
 type metadataService struct {
 	url string
-	client http.Client
 }
 
 func NewMetadataService(url string) *metadataService {
-	return &metadataService{url, http.Client{}}
+	return &metadataService{url}
 }
 
 func (ms *metadataService) Fetch() ([]byte, error) {
-	resp, err := ms.client.Get(ms.url)
-	if err != nil {
-		return []byte{}, err
-	}
-	defer resp.Body.Close()
-
-	if resp.StatusCode / 100 != 2 {
-		return []byte{}, nil
-	}
-
-	respBytes, err := ioutil.ReadAll(resp.Body)
-	if err != nil {
-		return nil, err
-	}
-
-	return respBytes, nil
+	return fetchURL(ms.url)
 }
 
 func (ms *metadataService) Type() string {

datasource/proc_cmdline.go

@@ -0,0 +1,66 @@
+package datasource
+
+import (
+	"errors"
+	"io/ioutil"
+	"log"
+	"strings"
+)
+
+const (
+	ProcCmdlineLocation        = "/proc/cmdline"
+	ProcCmdlineCloudConfigFlag = "cloud-config-url"
+)
+
+type procCmdline struct{}
+
+func NewProcCmdline() *procCmdline {
+	return &procCmdline{}
+}
+
+func (self *procCmdline) Fetch() ([]byte, error) {
+	cmdline, err := ioutil.ReadFile(ProcCmdlineLocation)
+	if err != nil {
+		return nil, err
+	}
+
+	url, err := findCloudConfigURL(string(cmdline))
+	if err != nil {
+		return nil, err
+	}
+
+	cfg, err := fetchURL(url)
+	if err != nil {
+		return nil, err
+	}
+
+	return cfg, nil
+}
+
+func (self *procCmdline) Type() string {
+	return "proc-cmdline"
+}
+
+func findCloudConfigURL(input string) (url string, err error) {
+	err = errors.New("cloud-config-url not found")
+	for _, token := range strings.Split(input, " ") {
+		parts := strings.SplitN(token, "=", 2)
+
+		key := parts[0]
+		key = strings.Replace(key, "_", "-", -1)
+
+		if key != "cloud-config-url" {
+			continue
+		}
+
+		if len(parts) != 2 {
+			log.Printf("Found cloud-config-url in /proc/cmdline with no value, ignoring.")
+			continue
+		}
+
+		url = parts[1]
+		err = nil
+	}
+
+	return
+}

datasource/proc_cmdline_test.go

@@ -0,0 +1,47 @@
+package datasource
+
+import (
+	"testing"
+)
+
+func TestParseCmdlineCloudConfigFound(t *testing.T) {
+	tests := []struct {
+		input  string
+		expect string
+	}{
+		{
+			"cloud-config-url=example.com",
+			"example.com",
+		},
+		{
+			"cloud_config_url=example.com",
+			"example.com",
+		},
+		{
+			"cloud-config-url cloud-config-url=example.com",
+			"example.com",
+		},
+		{
+			"cloud-config-url= cloud-config-url=example.com",
+			"example.com",
+		},
+		{
+			"cloud-config-url=one.example.com cloud-config-url=two.example.com",
+			"two.example.com",
+		},
+		{
+			"foo=bar cloud-config-url=example.com ping=pong",
+			"example.com",
+		},
+	}
+
+	for i, tt := range tests {
+		output, err := findCloudConfigURL(tt.input)
+		if output != tt.expect {
+			t.Errorf("Test case %d failed: %s != %s", i, output, tt.expect)
+		}
+		if err != nil {
+			t.Errorf("Test case %d produced error: %v", i, err)
+		}
+	}
+}

test

@@ -4,7 +4,7 @@ echo "Building bin/coreos-cloudinit"
 . build
 
 echo "Running tests..."
-for pkg in "./initialize ./system"; do
+for pkg in "./initialize ./system ./datasource"; do
 	go test -i $pkg
 	go test -v $pkg
 done