Falls back to SPDY for gorilla/websocket https proxy error

Kubernetes-commit: 9d560540c5268e0e2aebf5306907494cf522c260

Author: seans3

pkg/util/httpstream/httpstream.go

@@ -116,6 +116,15 @@ func IsUpgradeFailure(err error) bool {
 return errors.As(err, &upgradeErr)
 }
 
+// isHTTPSProxyError returns true if error is Gorilla/Websockets HTTPS Proxy dial error;
+// false otherwise (see https://github.com/kubernetes/kubernetes/issues/126134).
+func IsHTTPSProxyError(err error) bool {
+if err == nil {
+return false
+}
+return strings.Contains(err.Error(), "proxy: unknown scheme: https")
+}
+
 // IsUpgradeRequest returns true if the given request is a connection upgrade request
 func IsUpgradeRequest(req *http.Request) bool {
 for _, h := range req.Header[http.CanonicalHeaderKey(HeaderConnection)] {

pkg/util/httpstream/httpstream_test.go

@@ -168,3 +168,32 @@ func TestIsUpgradeFailureError(t *testing.T) {
 })
 }
 }
+
+func TestIsHTTPSProxyError(t *testing.T) {
+testCases := map[string]struct {
+err error
+expected bool
+}{
+"nil error should return false": {
+err: nil,
+expected: false,
+},
+"Not HTTPS proxy error should return false": {
+err: errors.New("this is not an upgrade error"),
+expected: false,
+},
+"HTTPS proxy error should return true": {
+err: errors.New("proxy: unknown scheme: https"),
+expected: true,
+},
+}
+
+for name, test := range testCases {
+t.Run(name, func(t *testing.T) {
+actual := IsHTTPSProxyError(test.err)
+if test.expected != actual {
+t.Errorf("expected HTTPS proxy error %t, got %t", test.expected, actual)
+}
+})
+}
+}