net/http/httputil: ensure DumpRequestOut dumps all of Body

Bodies larger than 8KB (the default bufio reader size) weren't
being dumped.  Force a read of the body so they're teed into
the response buffer.

Thanks to Steven Hartland for identifying the problem.

Fixes #8089

LGTM=r
R=golang-codereviews, r
CC=adg, golang-codereviews
https://golang.org/cl/144650044

src/net/http/httputil/dump.go

@@ -95,19 +95,27 @@ func DumpRequestOut(req *http.Request, body bool) ([]byte, error) {
 	// with a dummy response.
 	var buf bytes.Buffer // records the output
 	pr, pw := io.Pipe()
+	defer pr.Close()
+	defer pw.Close()
 	dr := &delegateReader{c: make(chan io.Reader)}
 	// Wait for the request before replying with a dummy response:
 	go func() {
-		http.ReadRequest(bufio.NewReader(pr))
+		req, err := http.ReadRequest(bufio.NewReader(pr))
+		if err == nil {
+			// Ensure all the body is read; otherwise
+			// we'll get a partial dump.
+			io.Copy(ioutil.Discard, req.Body)
+			req.Body.Close()
+		}
 		dr.c <- strings.NewReader("HTTP/1.1 204 No Content\r\n\r\n")
 	}()
 
 	t := &http.Transport{
+		DisableKeepAlives: true,
 		Dial: func(net, addr string) (net.Conn, error) {
 			return &dumpConn{io.MultiWriter(&buf, pw), dr}, nil
 		},
 	}
-	defer t.CloseIdleConnections()
 
 	_, err := t.RoundTrip(reqSend)
 

src/net/http/httputil/dump_test.go

@@ -111,6 +111,30 @@ var dumpTests = []dumpTest{
 
 		NoBody: true,
 	},
+
+	// Request with Body > 8196 (default buffer size)
+	{
+		Req: http.Request{
+			Method: "POST",
+			URL: &url.URL{
+				Scheme: "http",
+				Host:   "post.tld",
+				Path:   "/",
+			},
+			ContentLength: 8193,
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+		},
+
+		Body: bytes.Repeat([]byte("a"), 8193),
+
+		WantDumpOut: "POST / HTTP/1.1\r\n" +
+			"Host: post.tld\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"Content-Length: 8193\r\n" +
+			"Accept-Encoding: gzip\r\n\r\n" +
+			strings.Repeat("a", 8193),
+	},
 }
 
 func TestDumpRequest(t *testing.T) {
@@ -125,6 +149,8 @@ func TestDumpRequest(t *testing.T) {
 				tt.Req.Body = ioutil.NopCloser(bytes.NewReader(b))
 			case func() io.ReadCloser:
 				tt.Req.Body = b()
+			default:
+				t.Fatalf("Test %d: unsupported Body of %T", i, tt.Body)
 			}
 		}
 		setBody()
@@ -159,7 +185,9 @@ func TestDumpRequest(t *testing.T) {
 		}
 	}
 	if dg := runtime.NumGoroutine() - numg0; dg > 4 {
-		t.Errorf("Unexpectedly large number of new goroutines: %d new", dg)
+		buf := make([]byte, 4096)
+		buf = buf[:runtime.Stack(buf, true)]
+		t.Errorf("Unexpectedly large number of new goroutines: %d new: %s", dg, buf)
 	}
 }