Merge pull request #37494 from kad/issue-36573

Automatic merge from submit-queue (batch tested with PRs 36990, 37494, 38152, 37561, 38136)

Pass proxy environment variables to static pods

**What this PR does / why we need it**:

To access outside world or cloud provider APIs it might be
required to use proxy. kubeadm will be passing proxy variables to static pods during init stage.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes kubernetes/kubernetes#36573, kubernetes/kubeadm#5

**Special notes for your reviewer**:

**Release note**:
```release-note
- kubeadm will pass proxy environment variables to static pods.
```

cmd/kubeadm/app/master/manifests.go

@@ -76,6 +76,7 @@ func WriteStaticPodManifests(cfg *kubeadmapi.MasterConfiguration) error {
 			VolumeMounts:  volumeMounts,
 			LivenessProbe: componentProbe(8080, "/healthz"),
 			Resources:     componentResources("250m"),
+			Env:           getProxyEnvVars(),
 		}, volumes...),
 		kubeControllerManager: componentPod(api.Container{
 			Name:          kubeControllerManager,
@@ -84,6 +85,7 @@ func WriteStaticPodManifests(cfg *kubeadmapi.MasterConfiguration) error {
 			VolumeMounts:  volumeMounts,
 			LivenessProbe: componentProbe(10252, "/healthz"),
 			Resources:     componentResources("200m"),
+			Env:           getProxyEnvVars(),
 		}, volumes...),
 		kubeScheduler: componentPod(api.Container{
 			Name:          kubeScheduler,
@@ -91,6 +93,7 @@ func WriteStaticPodManifests(cfg *kubeadmapi.MasterConfiguration) error {
 			Command:       getSchedulerCommand(cfg),
 			LivenessProbe: componentProbe(10251, "/healthz"),
 			Resources:     componentResources("100m"),
+			Env:           getProxyEnvVars(),
 		}),
 	}
 
@@ -359,3 +362,21 @@ func getProxyCommand(cfg *kubeadmapi.MasterConfiguration) (command []string) {
 
 	return
 }
+
+func getProxyEnvVars() []api.EnvVar {
+	envs := []api.EnvVar{}
+	for _, env := range os.Environ() {
+		pos := strings.Index(env, "=")
+		if pos == -1 {
+			// malformed environment variable, skip it.
+			continue
+		}
+		name := env[:pos]
+		value := env[pos+1:]
+		if strings.HasSuffix(strings.ToLower(name), "_proxy") && value != "" {
+			envVar := api.EnvVar{Name: name, Value: value}
+			envs = append(envs, envVar)
+		}
+	}
+	return envs
+}