Update Kubeadm proxy handling for IPv6

cmd/kubeadm/app/preflight/checks.go

@@ -425,9 +425,9 @@ func (hst HTTPProxyCheck) Name() string {
 // Check validates http connectivity type, direct or via proxy.
 func (hst HTTPProxyCheck) Check() (warnings, errors []error) {
 
-	url := fmt.Sprintf("%s://%s", hst.Proto, hst.Host)
+	u := (&url.URL{Scheme: hst.Proto, Host: hst.Host}).String()
 
-	req, err := http.NewRequest("GET", url, nil)
+	req, err := http.NewRequest("GET", u, nil)
 	if err != nil {
 		return nil, []error{err}
 	}
@@ -437,7 +437,7 @@ func (hst HTTPProxyCheck) Check() (warnings, errors []error) {
 		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 []error{fmt.Errorf("Connection to %q uses proxy %q. If that is not intended, adjust your proxy settings", u, proxy)}, nil
 	}
 	return nil, nil
 }

cmd/kubeadm/app/preflight/checks_test.go

@@ -504,38 +504,84 @@ func TestHTTPProxyCIDRCheck(t *testing.T) {
 	}
 
 	// Save current content of *_proxy and *_PROXY variables.
-	savedEnv := resetProxyEnv()
+	savedEnv := resetProxyEnv(t)
 	defer restoreEnv(savedEnv)
-	t.Log("Saved environment: ", savedEnv)
-
-	os.Setenv("HTTP_PROXY", "http://proxy.example.com:3128")
-	os.Setenv("NO_PROXY", "example.com,10.0.0.0/8,2001:db8::/48")
 
-	// Check if we can reliably execute tests:
-	// ProxyFromEnvironment caches the *_proxy environment variables and
-	// if ProxyFromEnvironment already executed before our test with empty
-	// HTTP_PROXY it will make these tests return false positive failures
-	req, err := http.NewRequest("GET", "http://host.fake.tld/", nil)
-	if err != nil {
-		t.Fatalf("unexpected err: %v", err)
-	}
-	proxy, err := http.ProxyFromEnvironment(req)
-	if err != nil {
-		t.Fatalf("unexpected err: %v", err)
+	for _, rt := range tests {
+		warning, _ := rt.check.Check()
+		if (warning != nil) != rt.expectWarnings {
+			t.Errorf(
+				"failed HTTPProxyCIDRCheck:\n\texpected: %t\n\t  actual: %t (CIDR:%s). Warnings: %v",
+				rt.expectWarnings,
+				(warning != nil),
+				rt.check.CIDR,
+				warning,
+			)
+		}
 	}
-	if proxy == nil {
-		t.Skip("test skipped as ProxyFromEnvironment already initialized in environment without defined HTTP proxy")
+}
+
+func TestHTTPProxyCheck(t *testing.T) {
+	var tests = []struct {
+		name           string
+		check          HTTPProxyCheck
+		expectWarnings bool
+	}{
+		{
+			name: "Loopback address",
+			check: HTTPProxyCheck{
+				Proto: "https",
+				Host:  "127.0.0.1",
+			}, // Loopback addresses never should produce proxy warnings
+			expectWarnings: false,
+		},
+		{
+			name: "IPv4 direct access",
+			check: HTTPProxyCheck{
+				Proto: "https",
+				Host:  "10.96.0.1",
+			}, // Expected to be accessed directly, we set NO_PROXY to 10.0.0.0/8
+			expectWarnings: false,
+		},
+		{
+			name: "IPv4 via proxy",
+			check: HTTPProxyCheck{
+				Proto: "https",
+				Host:  "192.168.0.1",
+			}, // Expected to go via proxy as this range is not listed in NO_PROXY
+			expectWarnings: true,
+		},
+		{
+			name: "IPv6 direct access",
+			check: HTTPProxyCheck{
+				Proto: "https",
+				Host:  "[2001:db8::1:15]",
+			}, // Expected to be accessed directly, part of 2001:db8::/48 in NO_PROXY
+			expectWarnings: false,
+		},
+		{
+			name: "IPv6 via proxy",
+			check: HTTPProxyCheck{
+				Proto: "https",
+				Host:  "[2001:db8:1::1:15]",
+			}, // Expected to go via proxy, range is not in 2001:db8::/48
+			expectWarnings: true,
+		},
 	}
-	t.Log("http.ProxyFromEnvironment is usable, continue executing test")
+
+	// Save current content of *_proxy and *_PROXY variables.
+	savedEnv := resetProxyEnv(t)
+	defer restoreEnv(savedEnv)
 
 	for _, rt := range tests {
 		warning, _ := rt.check.Check()
 		if (warning != nil) != rt.expectWarnings {
 			t.Errorf(
-				"failed HTTPProxyCIDRCheck:\n\texpected: %t\n\t  actual: %t (CIDR:%s). Warnings: %v",
+				"%s failed HTTPProxyCheck:\n\texpected: %t\n\t  actual: %t (Host:%s). Warnings: %v",
+				rt.name,
 				rt.expectWarnings,
 				(warning != nil),
-				rt.check.CIDR,
+				rt.check.Host,
 				warning,
 			)
 		}
@@ -545,7 +591,7 @@ func TestHTTPProxyCIDRCheck(t *testing.T) {
 // resetProxyEnv is helper function that unsets all *_proxy variables
 // and return previously set values as map. This can be used to restore
 // original state of the environment.
-func resetProxyEnv() map[string]string {
+func resetProxyEnv(t *testing.T) map[string]string {
 	savedEnv := make(map[string]string)
 	for _, e := range os.Environ() {
 		pair := strings.Split(e, "=")
@@ -554,6 +600,26 @@ func resetProxyEnv() map[string]string {
 			os.Unsetenv(pair[0])
 		}
 	}
+	t.Log("Saved environment: ", savedEnv)
+
+	os.Setenv("HTTP_PROXY", "http://proxy.example.com:3128")
+	os.Setenv("NO_PROXY", "example.com,10.0.0.0/8,2001:db8::/48")
+	// Check if we can reliably execute tests:
+	// ProxyFromEnvironment caches the *_proxy environment variables and
+	// if ProxyFromEnvironment already executed before our test with empty
+	// HTTP_PROXY it will make these tests return false positive failures
+	req, err := http.NewRequest("GET", "http://host.fake.tld/", nil)
+	if err != nil {
+		t.Fatalf("unexpected err: %v", err)
+	}
+	proxy, err := http.ProxyFromEnvironment(req)
+	if err != nil {
+		t.Fatalf("unexpected err: %v", err)
+	}
+	if proxy == nil {
+		t.Skip("test skipped as ProxyFromEnvironment already initialized in environment without defined HTTP proxy")
+	}
+	t.Log("http.ProxyFromEnvironment is usable, continue executing test")
 	return savedEnv
 }