cmd/k8s-operator,k8s-operator/api-proxy: move k8s proxy code to library (#15857)

The defaultEnv and defaultBool functions are copied over temporarily
to minimise diff. This lays the ground work for having both the operator
and the new k8s-proxy binary implement the API proxy

Updates #13358

Change-Id: Ieacc79af64df2f13b27a18135517bb31c80a5a02
Signed-off-by: Tom Proctor <tomhjp@users.noreply.github.com>

cmd/k8s-operator/depaware.txt

@@ -840,9 +840,10 @@ tailscale.com/cmd/k8s-operator dependencies: (generated by github.com/tailscale/
         tailscale.com/ipn/store/kubestore                            from tailscale.com/cmd/k8s-operator+
         tailscale.com/ipn/store/mem                                  from tailscale.com/ipn/ipnlocal+
         tailscale.com/k8s-operator                                   from tailscale.com/cmd/k8s-operator
+        tailscale.com/k8s-operator/api-proxy                         from tailscale.com/cmd/k8s-operator
         tailscale.com/k8s-operator/apis                              from tailscale.com/k8s-operator/apis/v1alpha1
         tailscale.com/k8s-operator/apis/v1alpha1                     from tailscale.com/cmd/k8s-operator+
-        tailscale.com/k8s-operator/sessionrecording                  from tailscale.com/cmd/k8s-operator
+        tailscale.com/k8s-operator/sessionrecording                  from tailscale.com/k8s-operator/api-proxy
         tailscale.com/k8s-operator/sessionrecording/spdy             from tailscale.com/k8s-operator/sessionrecording
         tailscale.com/k8s-operator/sessionrecording/tsrecorder       from tailscale.com/k8s-operator/sessionrecording+
         tailscale.com/k8s-operator/sessionrecording/ws               from tailscale.com/k8s-operator/sessionrecording
@@ -945,7 +946,7 @@ tailscale.com/cmd/k8s-operator dependencies: (generated by github.com/tailscale/
         tailscale.com/util/clientmetric                              from tailscale.com/cmd/k8s-operator+
         tailscale.com/util/cloudenv                                  from tailscale.com/hostinfo+
         tailscale.com/util/cmpver                                    from tailscale.com/clientupdate+
-        tailscale.com/util/ctxkey                                    from tailscale.com/cmd/k8s-operator+
+        tailscale.com/util/ctxkey                                    from tailscale.com/client/tailscale/apitype+
      💣 tailscale.com/util/deephash                                  from tailscale.com/ipn/ipnlocal+
    L 💣 tailscale.com/util/dirwalk                                   from tailscale.com/metrics+
         tailscale.com/util/dnsname                                   from tailscale.com/appc+

cmd/k8s-operator/operator.go

@@ -45,6 +45,7 @@ import (
 	"tailscale.com/hostinfo"
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/store/kubestore"
+	apiproxy "tailscale.com/k8s-operator/api-proxy"
 	tsapi "tailscale.com/k8s-operator/apis/v1alpha1"
 	"tailscale.com/kube/kubetypes"
 	"tailscale.com/tsnet"
@@ -102,8 +103,8 @@ func main() {
 	// The operator can run either as a plain operator or it can
 	// additionally act as api-server proxy
 	// https://tailscale.com/kb/1236/kubernetes-operator/?q=kubernetes#accessing-the-kubernetes-control-plane-using-an-api-server-proxy.
-	mode := parseAPIProxyMode()
-	if mode == apiserverProxyModeDisabled {
+	mode := apiproxy.ParseAPIProxyMode()
+	if mode == apiproxy.APIServerProxyModeDisabled {
 		hostinfo.SetApp(kubetypes.AppOperator)
 	} else {
 		hostinfo.SetApp(kubetypes.AppAPIServerProxy)
@@ -112,7 +113,7 @@ func main() {
 	s, tsc := initTSNet(zlog)
 	defer s.Close()
 	restConfig := config.GetConfigOrDie()
-	maybeLaunchAPIServerProxy(zlog, restConfig, s, mode)
+	apiproxy.MaybeLaunchAPIServerProxy(zlog, restConfig, s, mode)
 	rOpts := reconcilerOpts{
 		log:                           zlog,
 		tsServer:                      s,

k8s-operator/api-proxy/doc.go

@@ -0,0 +1,8 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build !plan9
+
+// Package apiproxy contains the Kubernetes API Proxy implementation used by
+// k8s-operator and k8s-proxy.
+package apiproxy

k8s-operator/api-proxy/env.go

@@ -0,0 +1,29 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build !plan9
+
+package apiproxy
+
+import (
+	"os"
+
+	"tailscale.com/types/opt"
+)
+
+func defaultBool(envName string, defVal bool) bool {
+	vs := os.Getenv(envName)
+	if vs == "" {
+		return defVal
+	}
+	v, _ := opt.Bool(vs).Get()
+	return v
+}
+
+func defaultEnv(envName, defVal string) string {
+	v := os.Getenv(envName)
+	if v == "" {
+		return defVal
+	}
+	return v
+}

k8s-operator/api-proxy/proxy.go

@@ -3,7 +3,7 @@
 
 //go:build !plan9
 
-package main
+package apiproxy
 
 import (
 	"crypto/tls"
@@ -37,15 +37,15 @@ var (
 	whoIsKey                  = ctxkey.New("", (*apitype.WhoIsResponse)(nil))
 )
 
-type apiServerProxyMode int
+type APIServerProxyMode int
 
-func (a apiServerProxyMode) String() string {
+func (a APIServerProxyMode) String() string {
 	switch a {
-	case apiserverProxyModeDisabled:
+	case APIServerProxyModeDisabled:
 		return "disabled"
-	case apiserverProxyModeEnabled:
+	case APIServerProxyModeEnabled:
 		return "auth"
-	case apiserverProxyModeNoAuth:
+	case APIServerProxyModeNoAuth:
 		return "noauth"
 	default:
 		return "unknown"
@@ -53,12 +53,12 @@ func (a apiServerProxyMode) String() string {
 }
 
 const (
-	apiserverProxyModeDisabled apiServerProxyMode = iota
-	apiserverProxyModeEnabled
-	apiserverProxyModeNoAuth
+	APIServerProxyModeDisabled APIServerProxyMode = iota
+	APIServerProxyModeEnabled
+	APIServerProxyModeNoAuth
 )
 
-func parseAPIProxyMode() apiServerProxyMode {
+func ParseAPIProxyMode() APIServerProxyMode {
 	haveAuthProxyEnv := os.Getenv("AUTH_PROXY") != ""
 	haveAPIProxyEnv := os.Getenv("APISERVER_PROXY") != ""
 	switch {
@@ -67,34 +67,34 @@ func parseAPIProxyMode() apiServerProxyMode {
 	case haveAuthProxyEnv:
 		var authProxyEnv = defaultBool("AUTH_PROXY", false) // deprecated
 		if authProxyEnv {
-			return apiserverProxyModeEnabled
+			return APIServerProxyModeEnabled
 		}
-		return apiserverProxyModeDisabled
+		return APIServerProxyModeDisabled
 	case haveAPIProxyEnv:
 		var apiProxyEnv = defaultEnv("APISERVER_PROXY", "") // true, false or "noauth"
 		switch apiProxyEnv {
 		case "true":
-			return apiserverProxyModeEnabled
+			return APIServerProxyModeEnabled
 		case "false", "":
-			return apiserverProxyModeDisabled
+			return APIServerProxyModeDisabled
 		case "noauth":
-			return apiserverProxyModeNoAuth
+			return APIServerProxyModeNoAuth
 		default:
 			panic(fmt.Sprintf("unknown APISERVER_PROXY value %q", apiProxyEnv))
 		}
 	}
-	return apiserverProxyModeDisabled
+	return APIServerProxyModeDisabled
 }
 
 // maybeLaunchAPIServerProxy launches the auth proxy, which is a small HTTP server
 // that authenticates requests using the Tailscale LocalAPI and then proxies
 // them to the kube-apiserver.
-func maybeLaunchAPIServerProxy(zlog *zap.SugaredLogger, restConfig *rest.Config, s *tsnet.Server, mode apiServerProxyMode) {
-	if mode == apiserverProxyModeDisabled {
+func MaybeLaunchAPIServerProxy(zlog *zap.SugaredLogger, restConfig *rest.Config, s *tsnet.Server, mode APIServerProxyMode) {
+	if mode == APIServerProxyModeDisabled {
 		return
 	}
 	startlog := zlog.Named("launchAPIProxy")
-	if mode == apiserverProxyModeNoAuth {
+	if mode == APIServerProxyModeNoAuth {
 		restConfig = rest.AnonymousClientConfig(restConfig)
 	}
 	cfg, err := restConfig.TransportConfig()
@@ -132,8 +132,8 @@ func maybeLaunchAPIServerProxy(zlog *zap.SugaredLogger, restConfig *rest.Config,
 //     are passed through to the Kubernetes API.
 //
 // It never returns.
-func runAPIServerProxy(ts *tsnet.Server, rt http.RoundTripper, log *zap.SugaredLogger, mode apiServerProxyMode, host string) {
-	if mode == apiserverProxyModeDisabled {
+func runAPIServerProxy(ts *tsnet.Server, rt http.RoundTripper, log *zap.SugaredLogger, mode APIServerProxyMode, host string) {
+	if mode == APIServerProxyModeDisabled {
 		return
 	}
 	ln, err := ts.Listen("tcp", ":443")
@@ -192,7 +192,7 @@ type apiserverProxy struct {
 	lc  *local.Client
 	rp  *httputil.ReverseProxy
 
-	mode        apiServerProxyMode
+	mode        APIServerProxyMode
 	ts          *tsnet.Server
 	upstreamURL *url.URL
 }
@@ -285,7 +285,7 @@ func (ap *apiserverProxy) execForProto(w http.ResponseWriter, r *http.Request, p
 func (h *apiserverProxy) addImpersonationHeadersAsRequired(r *http.Request) {
 	r.URL.Scheme = h.upstreamURL.Scheme
 	r.URL.Host = h.upstreamURL.Host
-	if h.mode == apiserverProxyModeNoAuth {
+	if h.mode == APIServerProxyModeNoAuth {
 		// If we are not providing authentication, then we are just
 		// proxying to the Kubernetes API, so we don't need to do
 		// anything else.

k8s-operator/api-proxy/proxy_test.go

@@ -3,7 +3,7 @@
 
 //go:build !plan9
 
-package main
+package apiproxy
 
 import (
 	"net/http"