feat: Full support for proxy deploy

The index page will be handled correctly if the `XFF` and `X-API-URL-PREFIX` are set properly.

internal/config/flags.go

@@ -7,7 +7,6 @@ import (
 var InsecureSkipTLSVerify bool
 var SystemDefaultRegistry string
 var APIUIVersion = "1.1.11"
-
 var ShellPodImage string
 
 func Flags() []cli.Flag {

internal/ui/proxy.go

@@ -0,0 +1,116 @@
+package ui
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"strconv"
+
+	"github.com/rancher/apiserver/pkg/urlbuilder"
+	"k8s.io/apimachinery/pkg/util/proxy"
+)
+
+type RoundTripFunc func(*http.Request) (*http.Response, error)
+
+func (r RoundTripFunc) RoundTrip(req *http.Request) (*http.Response, error) {
+	return r(req)
+}
+
+func proxyMiddleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		scheme := urlbuilder.GetScheme(r)
+		host := urlbuilder.GetHost(r, scheme)
+		pathPrepend := r.Header.Get(urlbuilder.PrefixHeader)
+
+		if scheme == r.URL.Scheme && host == r.URL.Host && pathPrepend == "" {
+			next.ServeHTTP(w, r)
+			return
+		}
+
+		proxyRoundtrip := proxy.Transport{
+			Scheme:      scheme,
+			Host:        host,
+			PathPrepend: pathPrepend,
+			RoundTripper: RoundTripFunc(func(r *http.Request) (*http.Response, error) {
+				rw := &dummyResponseWriter{
+					next:   w,
+					header: make(http.Header),
+				}
+				next.ServeHTTP(rw, r)
+				return rw.getResponse(r), nil
+			}),
+		}
+		//proxyRoundtripper will write the response in RoundTrip func
+		resp, _ := proxyRoundtrip.RoundTrip(r)
+		responseToWriter(resp, w)
+	})
+
+}
+
+var _ http.ResponseWriter = &dummyResponseWriter{}
+var _ http.Hijacker = &dummyResponseWriter{}
+
+type dummyResponseWriter struct {
+	next http.ResponseWriter
+
+	header     http.Header
+	body       bytes.Buffer
+	statusCode int
+}
+
+// Hijack implements http.Hijacker.
+func (drw *dummyResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	if h, ok := drw.next.(http.Hijacker); ok {
+		return h.Hijack()
+	}
+	return nil, nil, fmt.Errorf("")
+}
+
+// Header implements the http.ResponseWriter interface.
+func (drw *dummyResponseWriter) Header() http.Header {
+	return drw.header
+}
+
+// Write implements the http.ResponseWriter interface.
+func (drw *dummyResponseWriter) Write(b []byte) (int, error) {
+	return drw.body.Write(b)
+}
+
+// WriteHeader implements the http.ResponseWriter interface.
+func (drw *dummyResponseWriter) WriteHeader(statusCode int) {
+	drw.statusCode = statusCode
+}
+
+// GetStatusCode returns the status code written to the response.
+func (drw *dummyResponseWriter) GetStatusCode() int {
+	if drw.statusCode == 0 {
+		return 200
+	}
+	return drw.statusCode
+}
+
+func (drw *dummyResponseWriter) getResponse(req *http.Request) *http.Response {
+	return &http.Response{
+		Status:     strconv.Itoa(drw.GetStatusCode()),
+		StatusCode: drw.GetStatusCode(),
+		Proto:      "HTTP/1.1",
+		ProtoMajor: 1,
+		ProtoMinor: 1,
+		Request:    req,
+		Header:     drw.header,
+		Body:       io.NopCloser(&drw.body),
+	}
+}
+
+func responseToWriter(resp *http.Response, writer http.ResponseWriter) {
+	for k, v := range resp.Header {
+		writer.Header()[k] = v
+	}
+	if resp.StatusCode != http.StatusOK {
+		writer.WriteHeader(resp.StatusCode)
+	}
+	_, _ = io.Copy(writer, resp.Body)
+}

internal/ui/routers.go

@@ -27,5 +27,5 @@ func New(opt *Options) (http.Handler, APIUI) {
 		http.Redirect(rw, req, url, http.StatusFound)
 	})
 
-	return router, apiUI(opt)
+	return proxyMiddleware(router), apiUI(opt)
 }