environment: add support for updating /etc/environment with IP values

To maintain the behavior of the coreos-setup-environment that has
started to move into cloudinit we need to write out /etc/environment
with the public and private addresses, if known. The file is updated so
that other contents are not replaced. This behavior is disabled entirely
if /etc/environment was written by a write_files entry.

initialize/config.go

@@ -223,12 +223,27 @@ func Apply(cfg CloudConfig, env *Environment) error {
 		cfg.Coreos.Units = append(cfg.Coreos.Units, u...)
 	}
 
+	wroteEnvironment := false
 	for _, file := range cfg.WriteFiles {
-		path, err := system.WriteFile(&file, env.Root())
+		fullPath, err := system.WriteFile(&file, env.Root())
 		if err != nil {
 			return err
 		}
-		log.Printf("Wrote file %s to filesystem", path)
+		if path.Clean(file.Path) == "/etc/environment" {
+			wroteEnvironment = true
+		}
+		log.Printf("Wrote file %s to filesystem", fullPath)
+	}
+
+	if !wroteEnvironment {
+		ef := env.DefaultEnvironmentFile()
+		if ef != nil {
+			err := system.WriteEnvFile(ef, env.Root())
+			if err != nil {
+				return err
+			}
+			log.Printf("Updated /etc/environment")
+		}
 	}
 
 	if env.NetconfType() != "" {

initialize/env.go

@@ -4,6 +4,8 @@ import (
 	"os"
 	"path"
 	"strings"
+
+	"github.com/coreos/coreos-cloudinit/system"
 )
 
 const DefaultSSHKeyName = "coreos-cloudinit"
@@ -65,6 +67,26 @@ func (e *Environment) Apply(data string) string {
 	return data
 }
 
+func (e *Environment) DefaultEnvironmentFile() *system.EnvFile {
+	ef := system.EnvFile{
+		File: &system.File{
+			Path: "/etc/environment",
+		},
+		Vars: map[string]string{},
+	}
+	if ip, ok := e.substitutions["$public_ipv4"]; ok && len(ip) > 0 {
+		ef.Vars["COREOS_PUBLIC_IPV4"] = ip
+	}
+	if ip, ok := e.substitutions["$private_ipv4"]; ok && len(ip) > 0 {
+		ef.Vars["COREOS_PRIVATE_IPV4"] = ip
+	}
+	if len(ef.Vars) == 0 {
+		return nil
+	} else {
+		return &ef
+	}
+}
+
 // normalizeSvcEnv standardizes the keys of the map (environment variables for a service)
 // by replacing any dashes with underscores and ensuring they are entirely upper case.
 // For example, "some-env" --> "SOME_ENV"

initialize/env_test.go

@@ -1,8 +1,12 @@
 package initialize
 
 import (
+	"io/ioutil"
 	"os"
+	"path"
 	"testing"
+
+	"github.com/coreos/coreos-cloudinit/system"
 )
 
 func TestEnvironmentApply(t *testing.T) {
@@ -56,3 +60,47 @@ ExecStop=/usr/bin/echo $unknown`,
 		}
 	}
 }
+
+func TestEnvironmentFile(t *testing.T) {
+	subs := map[string]string{
+		"$public_ipv4":  "1.2.3.4",
+		"$private_ipv4": "5.6.7.8",
+	}
+	expect := "COREOS_PUBLIC_IPV4=1.2.3.4\nCOREOS_PRIVATE_IPV4=5.6.7.8\n"
+
+	dir, err := ioutil.TempDir(os.TempDir(), "coreos-cloudinit-")
+	if err != nil {
+		t.Fatalf("Unable to create tempdir: %v", err)
+	}
+	defer os.RemoveAll(dir)
+
+	env := NewEnvironment("./", "./", "./", "", "", subs)
+	ef := env.DefaultEnvironmentFile()
+	err = system.WriteEnvFile(ef, dir)
+	if err != nil {
+		t.Fatalf("WriteEnvFile failed: %v", err)
+	}
+
+	fullPath := path.Join(dir, "etc", "environment")
+	contents, err := ioutil.ReadFile(fullPath)
+	if err != nil {
+		t.Fatalf("Unable to read expected file: %v", err)
+	}
+
+	if string(contents) != expect {
+		t.Fatalf("File has incorrect contents: %q", contents)
+	}
+}
+
+func TestEnvironmentFileNil(t *testing.T) {
+	subs := map[string]string{
+		"$public_ipv4":  "",
+		"$private_ipv4": "",
+	}
+
+	env := NewEnvironment("./", "./", "./", "", "", subs)
+	ef := env.DefaultEnvironmentFile()
+	if ef != nil {
+		t.Fatalf("Environment file not nil: %v", ef)
+	}
+}

system/env_file.go

@@ -22,7 +22,10 @@ var validKey = regexp.MustCompile(`^[a-zA-Z0-9_]+$`)
 // match each line, optionally capturing valid identifiers, discarding dos line endings
 var lineLexer = regexp.MustCompile(`(?m)^((?:([a-zA-Z0-9_]+)=)?.*?)\r?\n`)
 
-func updateEnv(old []byte, pending map[string]string) []byte {
+// mergeEnvContents: Update the existing file contents with new values,
+// preserving variable ordering and all content this code doesn't understand.
+// All new values are appended to the bottom of the old.
+func mergeEnvContents(old []byte, pending map[string]string) []byte {
 	var buf bytes.Buffer
 	var match [][]byte
 
@@ -53,7 +56,7 @@ func updateEnv(old []byte, pending map[string]string) []byte {
 // Existing ordering and any unknown formatting such as comments are
 // preserved. If no changes are required the file is untouched.
 func WriteEnvFile(ef *EnvFile, root string) error {
-	// validate new keys, updateEnv uses pending to track writes
+	// validate new keys, mergeEnvContents uses pending to track writes
 	pending := make(map[string]string, len(ef.Vars))
 	for key, value := range ef.Vars {
 		if !validKey.MatchString(key) {
@@ -75,7 +78,7 @@ func WriteEnvFile(ef *EnvFile, root string) error {
 		}
 	}
 
-	newContent := updateEnv(oldContent, pending)
+	newContent := mergeEnvContents(oldContent, pending)
 	if bytes.Equal(oldContent, newContent) {
 		return nil
 	}