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

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
+}