Merge pull request #1184 from PiotrSikora/max_streams

Fix handling of SETTINGS_MAX_CONCURRENT_STREAMS.

lib/includes/nghttp2/nghttp2.h

@@ -2478,15 +2478,15 @@ nghttp2_option_set_no_auto_window_update(nghttp2_option *option, int val);
  *
  * This option sets the SETTINGS_MAX_CONCURRENT_STREAMS value of
  * remote endpoint as if it is received in SETTINGS frame.  Without
- * specifying this option, before the local endpoint receives
+ * specifying this option, the maximum number of outgoing concurrent
- * SETTINGS_MAX_CONCURRENT_STREAMS in SETTINGS frame from remote
+ * streams is initially limited to 100 to avoid issues when the local
- * endpoint, SETTINGS_MAX_CONCURRENT_STREAMS is unlimited.  This may
+ * endpoint submits lots of requests before receiving initial SETTINGS
- * cause problem if local endpoint submits lots of requests initially
+ * frame from the remote endpoint, since sending them at once to the
- * and sending them at once to the remote peer may lead to the
+ * remote endpoint could lead to rejection of some of the requests.
- * rejection of some requests.  Specifying this option to the sensible
+ * This value will be overwritten when the local endpoint receives
- * value, say 100, may avoid this kind of issue. This value will be
+ * initial SETTINGS frame from the remote endpoint, either to the
- * overwritten if the local endpoint receives
+ * value advertised in SETTINGS_MAX_CONCURRENT_STREAMS or to the
- * SETTINGS_MAX_CONCURRENT_STREAMS from the remote endpoint.
+ * default value (unlimited) if none was advertised.
  */
 NGHTTP2_EXTERN void
 nghttp2_option_set_peer_max_concurrent_streams(nghttp2_option *option,

lib/nghttp2_session.c

@@ -4410,6 +4410,12 @@ int nghttp2_session_on_settings_received(nghttp2_session *session,
     return session_call_on_frame_received(session, frame);
   }
 
+  if (!session->remote_settings_received) {
+    session->remote_settings.max_concurrent_streams =
+        NGHTTP2_DEFAULT_MAX_CONCURRENT_STREAMS;
+    session->remote_settings_received = 1;
+  }
+
   for (i = 0; i < frame->settings.niv; ++i) {
     nghttp2_settings_entry *entry = &frame->settings.iv[i];
 

lib/nghttp2_session.h

@@ -303,8 +303,10 @@ struct nghttp2_session {
      increased/decreased by submitting WINDOW_UPDATE. See
      nghttp2_submit_window_update(). */
   int32_t local_window_size;
-  /* Settings value received from the remote endpoint. We just use ID
+  /* This flag is used to indicate that the local endpoint received initial
-     as index. The index = 0 is unused. */
+     SETTINGS frame from the remote endpoint. */
+  uint8_t remote_settings_received;
+  /* Settings value received from the remote endpoint. */
   nghttp2_settings_storage remote_settings;
   /* Settings value of the local endpoint. */
   nghttp2_settings_storage local_settings;

tests/nghttp2_session_test.c

@@ -3294,6 +3294,7 @@ void test_nghttp2_session_on_settings_received(void) {
   nghttp2_outbound_item *item;
   nghttp2_nv nv = MAKE_NV(":authority", "example.org");
   nghttp2_mem *mem;
+  nghttp2_option *option;
 
   mem = nghttp2_mem_default();
 
@@ -3406,6 +3407,23 @@ void test_nghttp2_session_on_settings_received(void) {
   nghttp2_frame_settings_free(&frame.settings, mem);
   nghttp2_session_del(session);
 
+  /* Check that remote SETTINGS_MAX_CONCURRENT_STREAMS is set to a value set by
+     nghttp2_option_set_peer_max_concurrent_streams() and reset to the default
+     value (unlimited) after receiving initial SETTINGS frame from the peer. */
+  nghttp2_option_new(&option);
+  nghttp2_option_set_peer_max_concurrent_streams(option, 1000);
+  nghttp2_session_client_new2(&session, &callbacks, NULL, option);
+  CU_ASSERT(1000 == session->remote_settings.max_concurrent_streams);
+
+  nghttp2_frame_settings_init(&frame.settings, NGHTTP2_FLAG_NONE, NULL, 0);
+  CU_ASSERT(0 == nghttp2_session_on_settings_received(session, &frame, 0));
+  CU_ASSERT(NGHTTP2_DEFAULT_MAX_CONCURRENT_STREAMS ==
+            session->remote_settings.max_concurrent_streams);
+
+  nghttp2_frame_settings_free(&frame.settings, mem);
+  nghttp2_session_del(session);
+  nghttp2_option_del(option);
+
   /* Check too large SETTINGS_MAX_FRAME_SIZE */
   nghttp2_session_server_new(&session, &callbacks, NULL);