Possible cipher suites values and tls versions in help for apiserver and kubelet

Kubernetes-commit: 3dfa22e3fd8c650789176b9f4a8e46ab43ef5ebf

pkg/server/options/serving.go

@@ -22,6 +22,7 @@ import (
 	"net"
 	"path"
 	"strconv"
+	"strings"
 
 	"github.com/golang/glog"
 	"github.com/spf13/pflag"
@@ -134,14 +135,16 @@ func (s *SecureServingOptions) AddFlags(fs *pflag.FlagSet) {
 	fs.StringVar(&s.ServerCert.CertKey.KeyFile, "tls-private-key-file", s.ServerCert.CertKey.KeyFile,
 		"File containing the default x509 private key matching --tls-cert-file.")
 
+	tlsCipherPossibleValues := utilflag.TLSCipherPossibleValues()
 	fs.StringSliceVar(&s.CipherSuites, "tls-cipher-suites", s.CipherSuites,
 		"Comma-separated list of cipher suites for the server. "+
-			"Values are from tls package constants (https://golang.org/pkg/crypto/tls/#pkg-constants). "+
-			"If omitted, the default Go cipher suites will be used")
+			"If omitted, the default Go cipher suites will be use.  "+
+			"Possible values: "+strings.Join(tlsCipherPossibleValues, ","))
 
+	tlsPossibleVersions := utilflag.TLSPossibleVersions()
 	fs.StringVar(&s.MinTLSVersion, "tls-min-version", s.MinTLSVersion,
 		"Minimum TLS version supported. "+
-			"Value must match version names from https://golang.org/pkg/crypto/tls/#pkg-constants.")
+			"Possible values: "+strings.Join(tlsPossibleVersions, ", "))
 
 	fs.Var(utilflag.NewNamedCertKeyArray(&s.SNICertKeys), "tls-sni-cert-key", ""+
 		"A pair of x509 certificate and private key file paths, optionally suffixed with a list of "+

pkg/util/flag/ciphersuites_flag.go

@@ -19,6 +19,8 @@ package flag
 import (
 	"crypto/tls"
 	"fmt"
+
+	"k8s.io/apimachinery/pkg/util/sets"
 )
 
 // ciphers maps strings into tls package cipher constants in
@@ -48,6 +50,14 @@ var ciphers = map[string]uint16{
 	"TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305":  tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
 }
 
+func TLSCipherPossibleValues() []string {
+	cipherKeys := sets.NewString()
+	for key := range ciphers {
+		cipherKeys.Insert(key)
+	}
+	return cipherKeys.List()
+}
+
 func TLSCipherSuites(cipherNames []string) ([]uint16, error) {
 	if len(cipherNames) == 0 {
 		return nil, nil
@@ -69,6 +79,14 @@ var versions = map[string]uint16{
 	"VersionTLS12": tls.VersionTLS12,
 }
 
+func TLSPossibleVersions() []string {
+	versionsKeys := sets.NewString()
+	for key := range versions {
+		versionsKeys.Insert(key)
+	}
+	return versionsKeys.List()
+}
+
 func TLSVersion(versionName string) (uint16, error) {
 	if len(versionName) == 0 {
 		return DefaultTLSVersion(), nil