net/http: support full-duplex HTTP/1 responses

Add support for concurrently reading from an HTTP/1 request body
while writing the response.

Normally, the HTTP/1 server automatically consumes any remaining
request body before starting to write a response, to avoid deadlocking
clients which attempt to write a complete request before reading the
response.

Add a ResponseController.EnableFullDuplex method which disables this
behavior.

For #15527
For #57786

Change-Id: Ie7ee8267d8333e9b32b82b9b84d4ad28ab8edf01
Reviewed-on: https://go-review.googlesource.com/c/go/+/472636
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Damien Neil <dneil@google.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>

1 files changed, 48 insertions, 0 deletions

diff --git a/src/net/http/responsecontroller_test.go b/src/net/http/responsecontroller_test.go
index 0dca7332b7..ee8b55a89f 100644
--- a/src/net/http/responsecontroller_test.go
+++ b/src/net/http/responsecontroller_test.go
@@ -263,3 +263,51 @@ func testWrappedResponseController(t *testing.T, mode testMode) {
 	io.Copy(io.Discard, res.Body)
 	defer res.Body.Close()
 }
+
+func TestResponseControllerEnableFullDuplex(t *testing.T) {
+	run(t, testResponseControllerEnableFullDuplex)
+}
+func testResponseControllerEnableFullDuplex(t *testing.T, mode testMode) {
+	cst := newClientServerTest(t, mode, HandlerFunc(func(w ResponseWriter, req *Request) {
+		ctl := NewResponseController(w)
+		if err := ctl.EnableFullDuplex(); err != nil {
+			// TODO: Drop test for HTTP/2 when x/net is updated to support
+			// EnableFullDuplex. Since HTTP/2 supports full duplex by default,
+			// the rest of the test is fine; it's just the EnableFullDuplex call
+			// that fails.
+			if mode != http2Mode {
+				t.Errorf("ctl.EnableFullDuplex() = %v, want nil", err)
+			}
+		}
+		w.WriteHeader(200)
+		ctl.Flush()
+		for {
+			var buf [1]byte
+			n, err := req.Body.Read(buf[:])
+			if n != 1 || err != nil {
+				break
+			}
+			w.Write(buf[:])
+			ctl.Flush()
+		}
+	}))
+	pr, pw := io.Pipe()
+	res, err := cst.c.Post(cst.ts.URL, "text/apocryphal", pr)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer res.Body.Close()
+	for i := byte(0); i < 10; i++ {
+		if _, err := pw.Write([]byte{i}); err != nil {
+			t.Fatalf("Write: %v", err)
+		}
+		var buf [1]byte
+		if n, err := res.Body.Read(buf[:]); n != 1 || err != nil {
+			t.Fatalf("Read: %v, %v", n, err)
+		}
+		if buf[0] != i {
+			t.Fatalf("read byte %v, want %v", buf[0], i)
+		}
+	}
+	pw.Close()
+}