Work on #61: Add support for ICMP

+ Update dependencies

vendor/cloud.google.com/go/compute/metadata/metadata.go

@@ -61,25 +61,14 @@ var (
 	instID  = &cachedValue{k: "instance/id", trim: true}
 )
 
-var (
-	defaultClient = &Client{hc: &http.Client{
-		Transport: &http.Transport{
-			Dial: (&net.Dialer{
-				Timeout:   2 * time.Second,
-				KeepAlive: 30 * time.Second,
-			}).Dial,
-			ResponseHeaderTimeout: 2 * time.Second,
-		},
-	}}
-	subscribeClient = &Client{hc: &http.Client{
-		Transport: &http.Transport{
-			Dial: (&net.Dialer{
-				Timeout:   2 * time.Second,
-				KeepAlive: 30 * time.Second,
-			}).Dial,
-		},
-	}}
-)
+var defaultClient = &Client{hc: &http.Client{
+	Transport: &http.Transport{
+		Dial: (&net.Dialer{
+			Timeout:   2 * time.Second,
+			KeepAlive: 30 * time.Second,
+		}).Dial,
+	},
+}}
 
 // NotDefinedError is returned when requested metadata is not defined.
 //
@@ -137,7 +126,7 @@ func testOnGCE() bool {
 	resc := make(chan bool, 2)
 
 	// Try two strategies in parallel.
-	// See https://github.com/GoogleCloudPlatform/google-cloud-go/issues/194
+	// See https://github.com/googleapis/google-cloud-go/issues/194
 	go func() {
 		req, _ := http.NewRequest("GET", "http://"+metadataIP, nil)
 		req.Header.Set("User-Agent", userAgent)
@@ -151,7 +140,7 @@ func testOnGCE() bool {
 	}()
 
 	go func() {
-		addrs, err := net.LookupHost("metadata.google.internal")
+		addrs, err := net.DefaultResolver.LookupHost(ctx, "metadata.google.internal")
 		if err != nil || len(addrs) == 0 {
 			resc <- false
 			return
@@ -206,10 +195,9 @@ func systemInfoSuggestsGCE() bool {
 	return name == "Google" || name == "Google Compute Engine"
 }
 
-// Subscribe calls Client.Subscribe on a client designed for subscribing (one with no
-// ResponseHeaderTimeout).
+// Subscribe calls Client.Subscribe on the default client.
 func Subscribe(suffix string, fn func(v string, ok bool) error) error {
-	return subscribeClient.Subscribe(suffix, fn)
+	return defaultClient.Subscribe(suffix, fn)
 }
 
 // Get calls Client.Get on the default client.
@@ -227,6 +215,9 @@ func InternalIP() (string, error) { return defaultClient.InternalIP() }
 // ExternalIP returns the instance's primary external (public) IP address.
 func ExternalIP() (string, error) { return defaultClient.ExternalIP() }
 
+// Email calls Client.Email on the default client.
+func Email(serviceAccount string) (string, error) { return defaultClient.Email(serviceAccount) }
+
 // Hostname returns the instance's hostname. This will be of the form
 // "<instanceID>.c.<projID>.internal".
 func Hostname() (string, error) { return defaultClient.Hostname() }
@@ -277,9 +268,14 @@ type Client struct {
 	hc *http.Client
 }
 
-// NewClient returns a Client that can be used to fetch metadata. All HTTP requests
-// will use the given http.Client instead of the default client.
+// NewClient returns a Client that can be used to fetch metadata.
+// Returns the client that uses the specified http.Client for HTTP requests.
+// If nil is specified, returns the default client.
 func NewClient(c *http.Client) *Client {
+	if c == nil {
+		return defaultClient
+	}
+
 	return &Client{hc: c}
 }
 
@@ -300,8 +296,12 @@ func (c *Client) getETag(suffix string) (value, etag string, err error) {
 		// being stable anyway.
 		host = metadataIP
 	}
-	url := "http://" + host + "/computeMetadata/v1/" + suffix
-	req, _ := http.NewRequest("GET", url, nil)
+	suffix = strings.TrimLeft(suffix, "/")
+	u := "http://" + host + "/computeMetadata/v1/" + suffix
+	req, err := http.NewRequest("GET", u, nil)
+	if err != nil {
+		return "", "", err
+	}
 	req.Header.Set("Metadata-Flavor", "Google")
 	req.Header.Set("User-Agent", userAgent)
 	res, err := c.hc.Do(req)
@@ -312,13 +312,13 @@ func (c *Client) getETag(suffix string) (value, etag string, err error) {
 	if res.StatusCode == http.StatusNotFound {
 		return "", "", NotDefinedError(suffix)
 	}
-	if res.StatusCode != 200 {
-		return "", "", fmt.Errorf("status code %d trying to fetch %s", res.StatusCode, url)
-	}
 	all, err := ioutil.ReadAll(res.Body)
 	if err != nil {
 		return "", "", err
 	}
+	if res.StatusCode != 200 {
+		return "", "", &Error{Code: res.StatusCode, Message: string(all)}
+	}
 	return string(all), res.Header.Get("Etag"), nil
 }
 
@@ -367,6 +367,16 @@ func (c *Client) InternalIP() (string, error) {
 	return c.getTrimmed("instance/network-interfaces/0/ip")
 }
 
+// Email returns the email address associated with the service account.
+// The account may be empty or the string "default" to use the instance's
+// main account.
+func (c *Client) Email(serviceAccount string) (string, error) {
+	if serviceAccount == "" {
+		serviceAccount = "default"
+	}
+	return c.getTrimmed("instance/service-accounts/" + serviceAccount + "/email")
+}
+
 // ExternalIP returns the instance's primary external (public) IP address.
 func (c *Client) ExternalIP() (string, error) {
 	return c.getTrimmed("instance/network-interfaces/0/access-configs/0/external-ip")
@@ -394,11 +404,7 @@ func (c *Client) InstanceTags() ([]string, error) {
 
 // InstanceName returns the current VM's instance ID string.
 func (c *Client) InstanceName() (string, error) {
-	host, err := c.Hostname()
-	if err != nil {
-		return "", err
-	}
-	return strings.Split(host, ".")[0], nil
+	return c.getTrimmed("instance/name")
 }
 
 // Zone returns the current VM's zone, such as "us-central1-b".
@@ -499,3 +505,15 @@ func (c *Client) Subscribe(suffix string, fn func(v string, ok bool) error) erro
 		}
 	}
 }
+
+// Error contains an error response from the server.
+type Error struct {
+	// Code is the HTTP response status code.
+	Code int
+	// Message is the server response message.
+	Message string
+}
+
+func (e *Error) Error() string {
+	return fmt.Sprintf("compute: Received %d `%s`", e.Code, e.Message)
+}