http2: accept HEAD requests with a body

RFC 7231 permits HEAD requests to contain a body, although it does
state there are no defined semantics for payloads of HEAD requests
and that some servers may reject HEAD requests with a payload.

Accept HEAD requests with a body.

Test is in net/http CL 418614.

For golang/go#53960.

Change-Id: I946d3ec796054c3908beb8a69cc78aa51c04c972
Reviewed-on: https://go-review.googlesource.com/c/net/+/418634
Run-TryBot: Damien Neil <dneil@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>

http2/server.go

@@ -2099,12 +2099,6 @@ func (sc *serverConn) newWriterAndRequest(st *stream, f *MetaHeadersFrame) (*res
 		return nil, nil, sc.countError("bad_path_method", streamError(f.StreamID, ErrCodeProtocol))
 	}
 
-	bodyOpen := !f.StreamEnded()
-	if rp.method == "HEAD" && bodyOpen {
-		// HEAD requests can't have bodies
-		return nil, nil, sc.countError("head_body", streamError(f.StreamID, ErrCodeProtocol))
-	}
-
 	rp.header = make(http.Header)
 	for _, hf := range f.RegularFields() {
 		rp.header.Add(sc.canonicalHeader(hf.Name), hf.Value)
@@ -2117,6 +2111,7 @@ func (sc *serverConn) newWriterAndRequest(st *stream, f *MetaHeadersFrame) (*res
 	if err != nil {
 		return nil, nil, err
 	}
+	bodyOpen := !f.StreamEnded()
 	if bodyOpen {
 		if vv, ok := rp.header["Content-Length"]; ok {
 			if cl, err := strconv.ParseUint(vv[0], 10, 63); err == nil {

http2/server_test.go

@@ -3388,21 +3388,6 @@ func TestConfigureServer(t *testing.T) {
 	}
 }
 
-func TestServerRejectHeadWithBody(t *testing.T) {
-	st := newServerTester(t, func(w http.ResponseWriter, r *http.Request) {
-		// No response body.
-	})
-	defer st.Close()
-	st.greet()
-	st.writeHeaders(HeadersFrameParam{
-		StreamID:      1, // clients send odd numbers
-		BlockFragment: st.encodeHeader(":method", "HEAD"),
-		EndStream:     false, // what we're testing, a bogus HEAD request with body
-		EndHeaders:    true,
-	})
-	st.wantRSTStream(1, ErrCodeProtocol)
-}
-
 func TestServerNoAutoContentLengthOnHead(t *testing.T) {
 	st := newServerTester(t, func(w http.ResponseWriter, r *http.Request) {
 		// No response body. (or smaller than one frame)