Add nghttp2_option_no_closed_streams

nghttp2_option_no_closed_streams controls whether closed streams are
retained or not.  If nonzero is passed to that function's parameter
val, a session does not retain closed streams.  It may hurt the shape
of priority tree, but can save memory.

doc/Makefile.am

@@ -62,6 +62,7 @@ APIDOCS= \
 	nghttp2_option_set_max_send_header_block_length.rst \
 	nghttp2_option_set_no_auto_ping_ack.rst \
 	nghttp2_option_set_no_auto_window_update.rst \
+	nghttp2_option_set_no_closed_streams.rst \
 	nghttp2_option_set_no_http_messaging.rst \
 	nghttp2_option_set_no_recv_client_magic.rst \
 	nghttp2_option_set_peer_max_concurrent_streams.rst \

lib/includes/nghttp2/nghttp2.h

@@ -2551,6 +2551,16 @@ NGHTTP2_EXTERN void
 nghttp2_option_set_max_deflate_dynamic_table_size(nghttp2_option *option,
                                                   size_t val);
 
+/**
+ * @function
+ *
+ * This option prevents the library from retaining closed streams to
+ * maintain the priority tree.  If this option is set to nonzero,
+ * applications can discard closed stream completely to save memory.
+ */
+NGHTTP2_EXTERN void nghttp2_option_set_no_closed_streams(nghttp2_option *option,
+                                                         int val);
+
 /**
  * @function
  *

lib/nghttp2_option.c

@@ -107,3 +107,8 @@ void nghttp2_option_set_max_deflate_dynamic_table_size(nghttp2_option *option,
   option->opt_set_mask |= NGHTTP2_OPT_MAX_DEFLATE_DYNAMIC_TABLE_SIZE;
   option->max_deflate_dynamic_table_size = val;
 }
+
+void nghttp2_option_set_no_closed_streams(nghttp2_option *option, int val) {
+  option->opt_set_mask |= NGHTTP2_OPT_NO_CLOSED_STREAMS;
+  option->no_closed_streams = val;
+}

lib/nghttp2_option.h

@@ -65,6 +65,7 @@ typedef enum {
   NGHTTP2_OPT_BUILTIN_RECV_EXT_TYPES = 1 << 7,
   NGHTTP2_OPT_MAX_SEND_HEADER_BLOCK_LENGTH = 1 << 8,
   NGHTTP2_OPT_MAX_DEFLATE_DYNAMIC_TABLE_SIZE = 1 << 9,
+  NGHTTP2_OPT_NO_CLOSED_STREAMS = 1 << 10,
 } nghttp2_option_flag;
 
 /**
@@ -112,6 +113,10 @@ struct nghttp2_option {
    * NGHTTP2_OPT_NO_AUTO_PING_ACK
    */
   int no_auto_ping_ack;
+  /**
+   * NGHTTP2_OPT_NO_CLOSED_STREAMS
+   */
+  int no_closed_streams;
   /**
    * NGHTTP2_OPT_USER_RECV_EXT_TYPES
    */

lib/nghttp2_session.c

@@ -494,6 +494,11 @@ static int session_new(nghttp2_session **session_ptr,
     if (option->opt_set_mask & NGHTTP2_OPT_MAX_DEFLATE_DYNAMIC_TABLE_SIZE) {
       max_deflate_dynamic_table_size = option->max_deflate_dynamic_table_size;
     }
+
+    if ((option->opt_set_mask & NGHTTP2_OPT_NO_CLOSED_STREAMS) &&
+        option->no_closed_streams) {
+      (*session_ptr)->opt_flags |= NGHTTP2_OPTMASK_NO_CLOSED_STREAMS;
+    }
   }
 
   rv = nghttp2_hd_deflate_init2(&(*session_ptr)->hd_deflater,
@@ -1186,7 +1191,8 @@ int nghttp2_session_close_stream(nghttp2_session *session, int32_t stream_id,
   /* Closes both directions just in case they are not closed yet */
   stream->flags |= NGHTTP2_STREAM_FLAG_CLOSED;
 
-  if (session->server && !is_my_stream_id &&
+  if ((session->opt_flags & NGHTTP2_OPTMASK_NO_CLOSED_STREAMS) == 0 &&
+      session->server && !is_my_stream_id &&
       nghttp2_stream_in_dep_tree(stream)) {
     /* On server side, retain stream at most MAX_CONCURRENT_STREAMS
        combined with the current active incoming streams to make

lib/nghttp2_session.h

@@ -51,7 +51,8 @@ typedef enum {
   NGHTTP2_OPTMASK_NO_AUTO_WINDOW_UPDATE = 1 << 0,
   NGHTTP2_OPTMASK_NO_RECV_CLIENT_MAGIC = 1 << 1,
   NGHTTP2_OPTMASK_NO_HTTP_MESSAGING = 1 << 2,
-  NGHTTP2_OPTMASK_NO_AUTO_PING_ACK = 1 << 3
+  NGHTTP2_OPTMASK_NO_AUTO_PING_ACK = 1 << 3,
+  NGHTTP2_OPTMASK_NO_CLOSED_STREAMS = 1 << 4
 } nghttp2_optmask;
 
 /*

tests/main.c

@@ -312,6 +312,8 @@ int main(int argc _U_, char *argv[] _U_) {
                    test_nghttp2_session_removed_closed_stream) ||
       !CU_add_test(pSuite, "session_pause_data",
                    test_nghttp2_session_pause_data) ||
+      !CU_add_test(pSuite, "session_no_closed_streams",
+                   test_nghttp2_session_no_closed_streams) ||
       !CU_add_test(pSuite, "http_mandatory_headers",
                    test_nghttp2_http_mandatory_headers) ||
       !CU_add_test(pSuite, "http_content_length",

tests/nghttp2_session_test.c

@@ -10098,6 +10098,28 @@ void test_nghttp2_session_pause_data(void) {
   nghttp2_session_del(session);
 }
 
+void test_nghttp2_session_no_closed_streams(void) {
+  nghttp2_session *session;
+  nghttp2_session_callbacks callbacks;
+  nghttp2_option *option;
+
+  memset(&callbacks, 0, sizeof(nghttp2_session_callbacks));
+
+  nghttp2_option_new(&option);
+  nghttp2_option_set_no_closed_streams(option, 1);
+
+  nghttp2_session_server_new2(&session, &callbacks, NULL, option);
+
+  open_recv_stream(session, 1);
+
+  nghttp2_session_close_stream(session, 1, NGHTTP2_NO_ERROR);
+
+  CU_ASSERT(0 == session->num_closed_streams);
+
+  nghttp2_session_del(session);
+  nghttp2_option_del(option);
+}
+
 static void check_nghttp2_http_recv_headers_fail(
     nghttp2_session *session, nghttp2_hd_deflater *deflater, int32_t stream_id,
     int stream_state, const nghttp2_nv *nva, size_t nvlen) {

tests/nghttp2_session_test.h

@@ -154,6 +154,7 @@ void test_nghttp2_session_set_local_window_size(void);
 void test_nghttp2_session_cancel_from_before_frame_send(void);
 void test_nghttp2_session_removed_closed_stream(void);
 void test_nghttp2_session_pause_data(void);
+void test_nghttp2_session_no_closed_streams(void);
 void test_nghttp2_http_mandatory_headers(void);
 void test_nghttp2_http_content_length(void);
 void test_nghttp2_http_content_length_mismatch(void);