Warn user if connections to API or Discovery are going to be over proxy

cmd/kubeadm/app/cmd/init.go

@@ -168,16 +168,6 @@ func NewInit(cfgPath string, cfg *kubeadmapi.MasterConfiguration, skipPreFlight
 		}
 	}
 
-	if !skipPreFlight {
-		fmt.Println("Running pre-flight checks")
-		err := preflight.RunInitMasterChecks(cfg)
-		if err != nil {
-			return nil, &preflight.PreFlightError{Msg: err.Error()}
-		}
-	} else {
-		fmt.Println("Skipping pre-flight checks")
-	}
-
 	// Auto-detect the IP
 	if len(cfg.API.AdvertiseAddresses) == 0 {
 		// TODO(phase1+) perhaps we could actually grab eth0 and eth1
@@ -188,6 +178,16 @@ func NewInit(cfgPath string, cfg *kubeadmapi.MasterConfiguration, skipPreFlight
 		cfg.API.AdvertiseAddresses = []string{ip.String()}
 	}
 
+	if !skipPreFlight {
+		fmt.Println("Running pre-flight checks")
+		err := preflight.RunInitMasterChecks(cfg)
+		if err != nil {
+			return nil, &preflight.PreFlightError{Msg: err.Error()}
+		}
+	} else {
+		fmt.Println("Skipping pre-flight checks")
+	}
+
 	// TODO(phase1+) create a custom flag
 	if cfg.CloudProvider != "" {
 		if cloudprovider.IsCloudProvider(cfg.CloudProvider) {

cmd/kubeadm/app/cmd/join.go

@@ -98,9 +98,15 @@ func NewJoin(cfgPath string, args []string, cfg *kubeadmapi.NodeConfiguration, s
 		}
 	}
 
+	// TODO(phase1+) this we are missing args from the help text, there should be a way to tell cobra about it
+	if len(args) == 0 && len(cfg.MasterAddresses) == 0 {
+		return nil, fmt.Errorf("must specify master IP address (see --help)")
+	}
+	cfg.MasterAddresses = append(cfg.MasterAddresses, args...)
+
 	if !skipPreFlight {
 		fmt.Println("Running pre-flight checks")
-		err := preflight.RunJoinNodeChecks()
+		err := preflight.RunJoinNodeChecks(cfg)
 		if err != nil {
 			return nil, &preflight.PreFlightError{Msg: err.Error()}
 		}
@@ -108,12 +114,6 @@ func NewJoin(cfgPath string, args []string, cfg *kubeadmapi.NodeConfiguration, s
 		fmt.Println("Skipping pre-flight checks")
 	}
 
-	// TODO(phase1+) this we are missing args from the help text, there should be a way to tell cobra about it
-	if len(args) == 0 && len(cfg.MasterAddresses) == 0 {
-		return nil, fmt.Errorf("must specify master IP address (see --help)")
-	}
-	cfg.MasterAddresses = append(cfg.MasterAddresses, args...)
-
 	ok, err := kubeadmutil.UseGivenTokenIfValid(&cfg.Secrets)
 	if !ok {
 		if err != nil {

cmd/kubeadm/app/preflight/checks.go

@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"net/http"
 	"os"
 	"os/exec"
 
@@ -185,6 +186,33 @@ func (hc HostnameCheck) Check() (warnings, errors []error) {
 	return nil, errors
 }
 
+// HttpProxyCheck checks if https connection to specific host is going
+// to be done directly or over proxy. If proxy detected, it will return warning.
+type HttpProxyCheck struct {
+	Proto string
+	Host  string
+	Port  int
+}
+
+func (hst HttpProxyCheck) Check() (warnings, errors []error) {
+
+	url := fmt.Sprintf("%s://%s:%d", hst.Proto, hst.Host, hst.Port)
+
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return nil, []error{err}
+	}
+
+	proxy, err := http.DefaultTransport.(*http.Transport).Proxy(req)
+	if err != nil {
+		return nil, []error{err}
+	}
+	if proxy != nil {
+		return []error{fmt.Errorf("Connection to %q uses proxy %q. If that is not intended, adjust your proxy settings", url, proxy)}, nil
+	}
+	return nil, nil
+}
+
 func RunInitMasterChecks(cfg *kubeadmapi.MasterConfiguration) error {
 	// TODO: Some of these ports should come from kubeadm config eventually:
 	checks := []PreFlightCheck{
@@ -199,6 +227,7 @@ func RunInitMasterChecks(cfg *kubeadmapi.MasterConfiguration) error {
 		PortOpenCheck{port: 10250},
 		PortOpenCheck{port: 10251},
 		PortOpenCheck{port: 10252},
+		HttpProxyCheck{Proto: "https", Host: cfg.API.AdvertiseAddresses[0], Port: int(cfg.API.BindPort)},
 		DirAvailableCheck{Path: "/etc/kubernetes/manifests"},
 		DirAvailableCheck{Path: "/etc/kubernetes/pki"},
 		DirAvailableCheck{Path: "/var/lib/etcd"},
@@ -219,7 +248,7 @@ func RunInitMasterChecks(cfg *kubeadmapi.MasterConfiguration) error {
 	return runChecks(checks, os.Stderr)
 }
 
-func RunJoinNodeChecks() error {
+func RunJoinNodeChecks(cfg *kubeadmapi.NodeConfiguration) error {
 	// TODO: Some of these ports should come from kubeadm config eventually:
 	checks := []PreFlightCheck{
 		IsRootCheck{root: true},
@@ -227,6 +256,8 @@ func RunJoinNodeChecks() error {
 		ServiceCheck{Service: "docker"},
 		ServiceCheck{Service: "kubelet"},
 		PortOpenCheck{port: 10250},
+		HttpProxyCheck{Proto: "https", Host: cfg.MasterAddresses[0], Port: int(cfg.APIPort)},
+		HttpProxyCheck{Proto: "http", Host: cfg.MasterAddresses[0], Port: int(cfg.DiscoveryPort)},
 		DirAvailableCheck{Path: "/etc/kubernetes"},
 		DirAvailableCheck{Path: "/var/lib/kubelet"},
 		InPathCheck{executable: "ebtables", mandatory: true},