Create stream object for pushed resource during nghttp2_submit_push_promise()

Previously, stream object for pushed resource was not created during
nghttp2_submit_push_promise().  It was created just before
nghttp2_before_frame_send_callback was called for that PUSH_PROMISE
frame.  This means that application could not call
nghttp2_submit_response for the pushed resource before
nghttp2_before_frame_send_callback was called.  This could be solved
by callback chaining, but for web server with back pressure from
backend stream, it is a bit unnecessarily hard to use.

This commit changes nghttp2_submit_push_promise() behaviour so that
stream object is created during that call.  It makes application call
nghttp2_submit_response right after successful
nghttp2_submit_push_promise call.

lib/includes/nghttp2/nghttp2.h

@@ -3573,14 +3573,20 @@ NGHTTP2_EXTERN int nghttp2_submit_settings(nghttp2_session *session,
  * :enum:`NGHTTP2_ERR_INVALID_ARGUMENT`
  *     The |stream_id| is 0; The |stream_id| does not designate stream
  *     that peer initiated.
+ * :enum:`NGHTTP2_ERR_STREAM_CLOSED`
+ *     The stream was alreay closed; or the |stream_id| is invalid.
  *
  * .. warning::
  *
  *   This function returns assigned promised stream ID if it succeeds.
- *   But that stream is not opened yet.  The application must not
+ *   As of 1.16.0, stream object for pushed resource is created when
- *   submit frame to that stream ID before
+ *   this function succeeds.  In that case, the application can submit
- *   :type:`nghttp2_before_frame_send_callback` is called for this
+ *   push response for the promised frame.
- *   frame.
+ *
+ *   In 1.15.0 or prior versions, pushed stream is not opened yet when
+ *   this function succeeds.  The application must not submit frame to
+ *   that stream ID before :type:`nghttp2_before_frame_send_callback`
+ *   is called for this frame.
  *
  */
 NGHTTP2_EXTERN int32_t

lib/nghttp2_session.c

@@ -750,6 +750,31 @@ int nghttp2_session_add_item(nghttp2_session *session,
       nghttp2_outbound_queue_push(&session->ob_reg, item);
       item->queued = 1;
       break;
+    case NGHTTP2_PUSH_PROMISE: {
+      nghttp2_headers_aux_data *aux_data;
+      nghttp2_priority_spec pri_spec;
+
+      aux_data = &item->aux_data.headers;
+
+      if (!stream) {
+        return NGHTTP2_ERR_STREAM_CLOSED;
+      }
+
+      nghttp2_priority_spec_init(&pri_spec, stream->stream_id,
+                                 NGHTTP2_DEFAULT_WEIGHT, 0);
+
+      if (!nghttp2_session_open_stream(
+              session, frame->push_promise.promised_stream_id,
+              NGHTTP2_STREAM_FLAG_NONE, &pri_spec, NGHTTP2_STREAM_RESERVED,
+              aux_data->stream_user_data)) {
+        return NGHTTP2_ERR_NOMEM;
+      }
+
+      nghttp2_outbound_queue_push(&session->ob_reg, item);
+      item->queued = 1;
+
+      break;
+    }
     case NGHTTP2_WINDOW_UPDATE:
       if (stream) {
         stream->window_update_queued = 1;
@@ -1903,30 +1928,8 @@ static int session_prep_frame(nghttp2_session *session,
     }
     case NGHTTP2_PUSH_PROMISE: {
       nghttp2_stream *stream;
-      nghttp2_headers_aux_data *aux_data;
-      nghttp2_priority_spec pri_spec;
       size_t estimated_payloadlen;
 
-      aux_data = &item->aux_data.headers;
-
-      stream = nghttp2_session_get_stream(session, frame->hd.stream_id);
-
-      /* stream could be NULL if associated stream was already
-         closed. */
-      if (stream) {
-        nghttp2_priority_spec_init(&pri_spec, stream->stream_id,
-                                   NGHTTP2_DEFAULT_WEIGHT, 0);
-      } else {
-        nghttp2_priority_spec_default_init(&pri_spec);
-      }
-
-      if (!nghttp2_session_open_stream(
-              session, frame->push_promise.promised_stream_id,
-              NGHTTP2_STREAM_FLAG_NONE, &pri_spec, NGHTTP2_STREAM_RESERVED,
-              aux_data->stream_user_data)) {
-        return NGHTTP2_ERR_NOMEM;
-      }
-
       estimated_payloadlen = session_estimate_headers_payload(
           session, frame->push_promise.nva, frame->push_promise.nvlen, 0);
 
@@ -1934,6 +1937,10 @@ static int session_prep_frame(nghttp2_session *session,
         return NGHTTP2_ERR_FRAME_SIZE_ERROR;
       }
 
+      /* stream could be NULL if associated stream was already
+         closed. */
+      stream = nghttp2_session_get_stream(session, frame->hd.stream_id);
+
       /* predicte should fail if stream is NULL. */
       rv = session_predicate_push_promise_send(session, stream);
       if (rv != 0) {

lib/nghttp2_session.h

@@ -334,7 +334,7 @@ int nghttp2_session_is_my_stream_id(nghttp2_session *session,
  * NGHTTP2_ERR_NOMEM
  *     Out of memory.
  * NGHTTP2_ERR_STREAM_CLOSED
- *     Stream already closed (DATA frame only)
+ *     Stream already closed (DATA and PUSH_PROMISE frame only)
  */
 int nghttp2_session_add_item(nghttp2_session *session,
                              nghttp2_outbound_item *item);

tests/nghttp2_session_test.c

@@ -4554,28 +4554,28 @@ void test_nghttp2_submit_push_promise(void) {
   CU_ASSERT(2 == nghttp2_submit_push_promise(session, NGHTTP2_FLAG_NONE, 1,
                                              reqnv, ARRLEN(reqnv), &ud));
 
+  stream = nghttp2_session_get_stream(session, 2);
+
+  CU_ASSERT(NULL != stream);
+  CU_ASSERT(NGHTTP2_STREAM_RESERVED == stream->state);
+  CU_ASSERT(&ud == nghttp2_session_get_stream_user_data(session, 2));
+
   ud.frame_send_cb_called = 0;
   ud.sent_frame_type = 0;
+
   CU_ASSERT(0 == nghttp2_session_send(session));
   CU_ASSERT(1 == ud.frame_send_cb_called);
   CU_ASSERT(NGHTTP2_PUSH_PROMISE == ud.sent_frame_type);
+
   stream = nghttp2_session_get_stream(session, 2);
+
   CU_ASSERT(NGHTTP2_STREAM_RESERVED == stream->state);
   CU_ASSERT(&ud == nghttp2_session_get_stream_user_data(session, 2));
 
   /* submit PUSH_PROMISE while associated stream is not opened */
-  CU_ASSERT(4 == nghttp2_submit_push_promise(session, NGHTTP2_FLAG_NONE, 3,
+  CU_ASSERT(NGHTTP2_ERR_STREAM_CLOSED ==
-                                             reqnv, ARRLEN(reqnv), &ud));
+            nghttp2_submit_push_promise(session, NGHTTP2_FLAG_NONE, 3, reqnv,
-
+                                        ARRLEN(reqnv), &ud));
-  ud.frame_not_send_cb_called = 0;
-
-  CU_ASSERT(0 == nghttp2_session_send(session));
-  CU_ASSERT(1 == ud.frame_not_send_cb_called);
-  CU_ASSERT(NGHTTP2_PUSH_PROMISE == ud.not_sent_frame_type);
-
-  stream = nghttp2_session_get_stream(session, 4);
-
-  CU_ASSERT(NULL == stream);
 
   nghttp2_session_del(session);
 }