net/http: add test showing that ReverseProxy HTTP/2 bidi streaming works

Change-Id: I8361ae33c785e45e3ccc7e9bc2732c887eeb41c4
Reviewed-on: https://go-review.googlesource.com/127015
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matt Layher <mdlayher@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/net/http/clientserver_test.go

@@ -9,8 +9,11 @@ package http_test
 import (
 	"bytes"
 	"compress/gzip"
+	"crypto/rand"
+	"crypto/sha1"
 	"crypto/tls"
 	"fmt"
+	"hash"
 	"io"
 	"io/ioutil"
 	"log"
@@ -1479,3 +1482,67 @@ func testWriteHeaderAfterWrite(t *testing.T, h2, hijack bool) {
 		t.Errorf("stderr output = %q; want %q", gotLog, wantLog)
 	}
 }
+
+func TestBidiStreamReverseProxy(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+	backend := newClientServerTest(t, h2Mode, HandlerFunc(func(w ResponseWriter, r *Request) {
+		if _, err := io.Copy(w, r.Body); err != nil {
+			log.Printf("bidi backend copy: %v", err)
+		}
+	}))
+	defer backend.close()
+
+	backURL, err := url.Parse(backend.ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	rp := httputil.NewSingleHostReverseProxy(backURL)
+	rp.Transport = backend.tr
+	proxy := newClientServerTest(t, h2Mode, HandlerFunc(func(w ResponseWriter, r *Request) {
+		rp.ServeHTTP(w, r)
+	}))
+	defer proxy.close()
+
+	bodyRes := make(chan interface{}, 1) // error or hash.Hash
+	pr, pw := io.Pipe()
+	req, _ := NewRequest("PUT", proxy.ts.URL, pr)
+	const size = 4 << 20
+	go func() {
+		h := sha1.New()
+		_, err := io.CopyN(io.MultiWriter(h, pw), rand.Reader, size)
+		go pw.Close()
+		if err != nil {
+			bodyRes <- err
+		} else {
+			bodyRes <- h
+		}
+	}()
+	res, err := backend.c.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer res.Body.Close()
+	hgot := sha1.New()
+	n, err := io.Copy(hgot, res.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if n != size {
+		t.Fatalf("got %d bytes; want %d", n, size)
+	}
+	select {
+	case v := <-bodyRes:
+		switch v := v.(type) {
+		default:
+			t.Fatalf("body copy: %v", err)
+		case hash.Hash:
+			if !bytes.Equal(v.Sum(nil), hgot.Sum(nil)) {
+				t.Errorf("written bytes didn't match received bytes")
+			}
+		}
+	case <-time.After(10 * time.Second):
+		t.Fatal("timeout")
+	}
+
+}