From: Ignacio Hagopian <jsign.uy@gmail.com>
Date: Thu, 8 Oct 2020 20:32:50 +0000 (+0000)
Subject: net/http/httputil: flush ReverseProxy immediately if Content-Length is -1
X-Git-Tag: go1.16beta1~769
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=ca3c0df1f8e07337ba4048b191bf905118ebe251;p=gostls13.git

net/http/httputil: flush ReverseProxy immediately if Content-Length is -1

Finish up a prior TODO by making ReverseProxy flush immediately
if Content-Length is -1, which is a case that can occur if for
example we have a streamed response, or chunked encoding, or when
the body's length wasn't known.

Fixes #41642

Change-Id: I30babaaf3e14837b99e3ecdc562a0a0e50c579bf
GitHub-Last-Rev: efc019a9fe361082d40bee77317018c3b80451a3
GitHub-Pull-Request: golang/go#41858
Reviewed-on: https://go-review.googlesource.com/c/go/+/260637
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Ian Lance Taylor <iant@golang.org>
Trust: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
---

diff --git a/src/net/http/httputil/reverseproxy.go b/src/net/http/httputil/reverseproxy.go
index 3f48fab544..46e5f68a84 100644
--- a/src/net/http/httputil/reverseproxy.go
+++ b/src/net/http/httputil/reverseproxy.go
@@ -58,9 +58,9 @@ type ReverseProxy struct {
 	// A negative value means to flush immediately
 	// after each write to the client.
 	// The FlushInterval is ignored when ReverseProxy
-	// recognizes a response as a streaming response;
-	// for such responses, writes are flushed to the client
-	// immediately.
+	// recognizes a response as a streaming response, or
+	// if its ContentLength is -1; for such responses, writes
+	// are flushed to the client immediately.
 	FlushInterval time.Duration
 
 	// ErrorLog specifies an optional logger for errors
@@ -325,7 +325,7 @@ func (p *ReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 
 	rw.WriteHeader(res.StatusCode)
 
-	err = p.copyResponse(rw, res.Body, p.flushInterval(req, res))
+	err = p.copyResponse(rw, res.Body, p.flushInterval(res))
 	if err != nil {
 		defer res.Body.Close()
 		// Since we're streaming the response, if we run into an error all we can do
@@ -397,7 +397,7 @@ func removeConnectionHeaders(h http.Header) {
 
 // flushInterval returns the p.FlushInterval value, conditionally
 // overriding its value for a specific request/response.
-func (p *ReverseProxy) flushInterval(req *http.Request, res *http.Response) time.Duration {
+func (p *ReverseProxy) flushInterval(res *http.Response) time.Duration {
 	resCT := res.Header.Get("Content-Type")
 
 	// For Server-Sent Events responses, flush immediately.
@@ -406,7 +406,11 @@ func (p *ReverseProxy) flushInterval(req *http.Request, res *http.Response) time
 		return -1 // negative means immediately
 	}
 
-	// TODO: more specific cases? e.g. res.ContentLength == -1?
+	// We might have the case of streaming for which Content-Length might be unset.
+	if res.ContentLength == -1 {
+		return -1
+	}
+
 	return p.FlushInterval
 }
 
diff --git a/src/net/http/httputil/reverseproxy_test.go b/src/net/http/httputil/reverseproxy_test.go
index 764939fb0f..ea786864d8 100644
--- a/src/net/http/httputil/reverseproxy_test.go
+++ b/src/net/http/httputil/reverseproxy_test.go
@@ -1067,7 +1067,6 @@ func TestSelectFlushInterval(t *testing.T) {
 	tests := []struct {
 		name string
 		p    *ReverseProxy
-		req  *http.Request
 		res  *http.Response
 		want time.Duration
 	}{
@@ -1097,10 +1096,26 @@ func TestSelectFlushInterval(t *testing.T) {
 			p:    &ReverseProxy{FlushInterval: 0},
 			want: -1,
 		},
+		{
+			name: "Content-Length: -1, overrides non-zero",
+			res: &http.Response{
+				ContentLength: -1,
+			},
+			p:    &ReverseProxy{FlushInterval: 123},
+			want: -1,
+		},
+		{
+			name: "Content-Length: -1, overrides zero",
+			res: &http.Response{
+				ContentLength: -1,
+			},
+			p:    &ReverseProxy{FlushInterval: 0},
+			want: -1,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			got := tt.p.flushInterval(tt.req, tt.res)
+			got := tt.p.flushInterval(tt.res)
 			if got != tt.want {
 				t.Errorf("flushLatency = %v; want %v", got, tt.want)
 			}