From d440d194e5e9b4971177f57ce60ab6a3ec1ecd8c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?K=C3=A9vin=20Dunglas?= Date: Tue, 4 Jan 2022 21:30:37 +0100 Subject: [PATCH] net/http: reverseproxy: forward 1xx responses Support for 1xx responses has recently been merged in net/http (#42597). As discussed in this CL (https://go-review.googlesource.com/c/go/+/269997/comments/1ff70bef_c25a829a), support for forwarding 1xx responses in ReverseProxy has been extracted in this separate patch. According to RFC 7231, "a proxy MUST forward 1xx responses unless the proxy itself requested the generation of the 1xx response". Consequently, all received 1xx responses are automatically forwarded as long as the underlying transport supports ClientTrace.Got1xxResponse. Fixes #26088 Fixes #51914 --- src/net/http/httputil/reverseproxy.go | 30 ++++++++- src/net/http/httputil/reverseproxy_test.go | 76 ++++++++++++++++++++++ 2 files changed, 105 insertions(+), 1 deletion(-) diff --git a/src/net/http/httputil/reverseproxy.go b/src/net/http/httputil/reverseproxy.go index 9ab7367eb2a9e..0bb54b5b515a4 100644 --- a/src/net/http/httputil/reverseproxy.go +++ b/src/net/http/httputil/reverseproxy.go @@ -15,6 +15,7 @@ import ( "mime" "net" "net/http" + "net/http/httptrace" "net/http/internal/ascii" "net/textproto" "net/url" @@ -96,6 +97,9 @@ func (r *ProxyRequest) SetXForwarded() { // ReverseProxy is an HTTP Handler that takes an incoming request and // sends it to another server, proxying the response back to the // client. +// +// 1xx responses are forwarded to the client if the underlying +// transport supports ClientTrace.Got1xxResponse. type ReverseProxy struct { // Rewrite must be a function which modifies // the request into a new request to be sent @@ -449,6 +453,23 @@ func (p *ReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) { outreq.Header.Set("User-Agent", "") } + var headerSet bool + trace := &httptrace.ClientTrace{ + Got1xxResponse: func(code int, header textproto.MIMEHeader) error { + h := rw.Header() + copyHeader(h, http.Header(header)) + rw.WriteHeader(code) + + // Clear headers, it's not automatically done by ResponseWriter.WriteHeader() for 1xx responses + for k, _ := range h { + h.Del(k) + } + + return nil + }, + } + outreq = outreq.WithContext(httptrace.WithClientTrace(outreq.Context(), trace)) + res, err := transport.RoundTrip(outreq) if err != nil { p.getErrorHandler()(rw, outreq, err) @@ -470,7 +491,14 @@ func (p *ReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) { return } - copyHeader(rw.Header(), res.Header) + h := rw.Header() + if headerSet { + for k, _ := range h { + h.Del(k) + } + } + + copyHeader(h, res.Header) // The "Trailer" header isn't included in the Transport's response, // at least for *http.Transport. Build it up from Trailer. diff --git a/src/net/http/httputil/reverseproxy_test.go b/src/net/http/httputil/reverseproxy_test.go index f8157e9435267..e0d96ef9cce58 100644 --- a/src/net/http/httputil/reverseproxy_test.go +++ b/src/net/http/httputil/reverseproxy_test.go @@ -16,7 +16,9 @@ import ( "log" "net/http" "net/http/httptest" + "net/http/httptrace" "net/http/internal/ascii" + "net/textproto" "net/url" "os" "reflect" @@ -1671,3 +1673,77 @@ func TestReverseProxyRewriteReplacesOut(t *testing.T) { t.Errorf("got response %q, want %q", got, want) } } + +func Test1xxResponses(t *testing.T) { + backend := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { + h := w.Header() + h.Add("Link", "; rel=preload; as=style") + h.Add("Link", "; rel=preload; as=script") + w.WriteHeader(http.StatusEarlyHints) + + h.Add("Link", "; rel=preload; as=script") + w.WriteHeader(http.StatusProcessing) + + w.Write([]byte("Hello")) + })) + defer backend.Close() + backendURL, err := url.Parse(backend.URL) + if err != nil { + t.Fatal(err) + } + proxyHandler := NewSingleHostReverseProxy(backendURL) + proxyHandler.ErrorLog = log.New(io.Discard, "", 0) // quiet for tests + frontend := httptest.NewServer(proxyHandler) + defer frontend.Close() + frontendClient := frontend.Client() + + checkLinkHeaders := func(t *testing.T, expected, got []string) { + t.Helper() + + if len(expected) != len(got) { + t.Errorf("Expected %d link headers; got %d", len(expected), len(got)) + } + + for i := range expected { + if expected[i] != got[i] { + t.Errorf("Expected %q link header; got %q", expected[i], got[i]) + } + } + } + + var respCounter uint8 + trace := &httptrace.ClientTrace{ + Got1xxResponse: func(code int, header textproto.MIMEHeader) error { + switch code { + case http.StatusEarlyHints: + checkLinkHeaders(t, []string{"; rel=preload; as=style", "; rel=preload; as=script"}, header["Link"]) + case http.StatusProcessing: + checkLinkHeaders(t, []string{"; rel=preload; as=style", "; rel=preload; as=script", "; rel=preload; as=script"}, header["Link"]) + default: + t.Error("Unexpected 1xx response") + } + + respCounter++ + + return nil + }, + } + req, _ := http.NewRequestWithContext(httptrace.WithClientTrace(context.Background(), trace), "GET", frontend.URL, nil) + + res, err := frontendClient.Do(req) + if err != nil { + t.Fatalf("Get: %v", err) + } + + defer res.Body.Close() + + if respCounter != 2 { + t.Errorf("Excpected 2 1xx responses; got %d", respCounter) + } + checkLinkHeaders(t, []string{"; rel=preload; as=style", "; rel=preload; as=script", "; rel=preload; as=script"}, res.Header["Link"]) + + body, _ := io.ReadAll(res.Body) + if string(body) != "Hello" { + t.Errorf("Read body %q; want Hello", body) + } +}