net/http/httputil: pass through any "TE: trailers" header to backend

Fixes #21096

Change-Id: I2a4688a79bdaa25b4e8ef38e3390d93d3d0bce04
Reviewed-on: https://go-review.googlesource.com/115135
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/net/http/httputil/reverseproxy.go b/src/net/http/httputil/reverseproxy.go
index 80ee22895af6ac93b52dccff65ba5c981476b2f0..d5d0a505f7b93f1d17c5561c75b9ab843bc0d764 100644 (file)
--- a/src/net/http/httputil/reverseproxy.go
+++ b/src/net/http/httputil/reverseproxy.go
@@ -178,9 +178,20 @@ func (p *ReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
        // important is "Connection" because we want a persistent
        // connection, regardless of what the client sent to us.
        for _, h := range hopHeaders {
-               if outreq.Header.Get(h) != "" {
-                       outreq.Header.Del(h)
+               hv := outreq.Header.Get(h)
+               if hv == "" {
+                       continue
                }
+               if h == "Te" && hv == "trailers" {
+                       // Issue 21096: tell backend applications that
+                       // care about trailer support that we support
+                       // trailers. (We do, but we don't go out of
+                       // our way to advertise that unless the
+                       // incoming client request thought it was
+                       // worth mentioning)
+                       continue
+               }
+               outreq.Header.Del(h)
        }
 
        if clientIP, _, err := net.SplitHostPort(req.RemoteAddr); err == nil {

diff --git a/src/net/http/httputil/reverseproxy_test.go b/src/net/http/httputil/reverseproxy_test.go
index 3dcc5c72874facc6d0ba96da34c24ed989ddfe9f..1ad67562af047be468ff1f4e7ca36b8d2690a5c0 100644 (file)
--- a/src/net/http/httputil/reverseproxy_test.go
+++ b/src/net/http/httputil/reverseproxy_test.go
@@ -49,6 +49,9 @@ func TestReverseProxy(t *testing.T) {
                if c := r.Header.Get("Connection"); c != "" {
                        t.Errorf("handler got Connection header value %q", c)
                }
+               if c := r.Header.Get("Te"); c != "trailers" {
+                       t.Errorf("handler got Te header value %q; want 'trailers'", c)
+               }
                if c := r.Header.Get("Upgrade"); c != "" {
                        t.Errorf("handler got Upgrade header value %q", c)
                }
@@ -85,6 +88,7 @@ func TestReverseProxy(t *testing.T) {
        getReq, _ := http.NewRequest("GET", frontend.URL, nil)
        getReq.Host = "some-name"
        getReq.Header.Set("Connection", "close")
+       getReq.Header.Set("Te", "trailers")
        getReq.Header.Set("Proxy-Connection", "should be deleted")
        getReq.Header.Set("Upgrade", "foo")
        getReq.Close = true