Add a way to send trailer with nghttp2_submit_request/nghttp2_submit_response

nghttp2_submit_request and nghttp2_submit_response will set
NGHTTP2_FLAG_END_STREAM after all given data is sent (data could be
0).  This means we have no way to send trailers.  In this commit, we
added NGHTTP2_DATA_FLAG_NO_END_STREAM flag.  The application can set
this flag in *data_flags inside nghttp2_data_source_read_callback.  If
NGHTTP2_DATA_FLAG_EOF is set, library automatically set
NGHTTP2_FLAG_END_STREAM.  But if both NGHTTP2_DATA_FLAG_EOF and
NGHTTP2_DATA_FLAG_NO_END_STREAM are set, NGHTTP2_FLAG_END_STREAM will
not set by library.  Then application can use new
nghttp2_submit_trailer() to send trailers.  nghttp2_submit_trailer()
will set NGHTTP2_FLAG_END_STREAM and it is actually thing wrapper of
nghttp2_submit_headers().

lib/includes/nghttp2/nghttp2.h

@@ -682,7 +682,14 @@ typedef enum {
   /**
    * Indicates EOF was sensed.
    */
-  NGHTTP2_DATA_FLAG_EOF = 0x01
+  NGHTTP2_DATA_FLAG_EOF = 0x01,
+  /**
+   * Indicates that END_STREAM flag must not be set even if
+   * NGHTTP2_DATA_FLAG_EOF is set.  Usually this flag is used to send
+   * trailer header fields with `nghttp2_submit_request()` or
+   * `nghttp2_submit_response()`.
+   */
+  NGHTTP2_DATA_FLAG_NO_END_STREAM = 0x02,
 } nghttp2_data_flag;
 
 /**
@@ -2834,6 +2841,53 @@ int nghttp2_submit_response(nghttp2_session *session, int32_t stream_id,
                             const nghttp2_nv *nva, size_t nvlen,
                             const nghttp2_data_provider *data_prd);
 
+/**
+ * @function
+ *
+ * Submits trailer HEADERS against the stream |stream_id|.
+ *
+ * The |nva| is an array of name/value pair :type:`nghttp2_nv` with
+ * |nvlen| elements.  The application is responsible not to include
+ * required pseudo-header fields (header field whose name starts with
+ * ":") in |nva|.
+ *
+ * This function creates copies of all name/value pairs in |nva|.  It
+ * also lower-cases all names in |nva|.  The order of elements in
+ * |nva| is preserved.
+ *
+ * For server, trailer must be followed by response HEADERS or
+ * response DATA.  The library does not check that response HEADERS
+ * has already sent and if `nghttp2_submit_trailer()` is called before
+ * any response HEADERS submission (usually by
+ * `nghttp2_submit_response()`), the content of |nva| will be sent as
+ * reponse headers, which will result in error.
+ *
+ * This function has the same effect with `nghttp2_submit_headers()`,
+ * with flags = :enum:`NGHTTP2_FLAG_END_HEADERS` and both pri_spec and
+ * stream_user_data to NULL.
+ *
+ * To submit trailer after `nghttp2_submit_response()` is called, the
+ * application has to specify :type:`nghttp2_data_provider` to
+ * `nghttp2_submit_response()`.  In side
+ * :type:`nghttp2_data_source_read_callback`, when setting
+ * :enum:`NGHTTP2_DATA_FLAG_EOF`, also set
+ * :enum:`NGHTTP2_DATA_FLAG_NO_END_STREAM`.  After that, the
+ * application can send trailer using `nghttp2_submit_trailer()`.
+ * `nghttp2_submit_trailer()` can be used inside
+ * :type:`nghttp2_data_source_read_callback`.
+ *
+ * This function returns 0 if it succeeds and |stream_id| is -1.
+ * Otherwise, this function returns 0 if it succeeds, or one of the
+ * following negative error codes:
+ *
+ * :enum:`NGHTTP2_ERR_NOMEM`
+ *     Out of memory.
+ * :enum:`NGHTTP2_ERR_INVALID_ARGUMENT`
+ *     The |stream_id| is 0.
+ */
+int nghttp2_submit_trailer(nghttp2_session *session, int32_t stream_id,
+                           const nghttp2_nv *nva, size_t nvlen);
+
 /**
  * @function
  *

lib/nghttp2_session.c

@@ -6222,7 +6222,10 @@ int nghttp2_session_pack_data(nghttp2_session *session, nghttp2_bufs *bufs,
 
   if (data_flags & NGHTTP2_DATA_FLAG_EOF) {
     aux_data->eof = 1;
-    if (aux_data->flags & NGHTTP2_FLAG_END_STREAM) {
+    /* If NGHTTP2_DATA_FLAG_NO_END_STREAM is set, don't set
+       NGHTTP2_FLAG_END_STREAM */
+    if ((aux_data->flags & NGHTTP2_FLAG_END_STREAM) &&
+        (data_flags & NGHTTP2_DATA_FLAG_NO_END_STREAM) == 0) {
       frame->hd.flags |= NGHTTP2_FLAG_END_STREAM;
     }
   }

lib/nghttp2_submit.c

@@ -155,6 +155,12 @@ static int32_t submit_headers_shared_nva(nghttp2_session *session,
                                attach_stream);
 }
 
+int32_t nghttp2_submit_trailer(nghttp2_session *session, int32_t stream_id,
+                               const nghttp2_nv *nva, size_t nvlen) {
+  return submit_headers_shared_nva(session, NGHTTP2_FLAG_END_STREAM, stream_id,
+                                   NULL, nva, nvlen, NULL, NULL, 0);
+}
+
 int32_t nghttp2_submit_headers(nghttp2_session *session, uint8_t flags,
                                int32_t stream_id,
                                const nghttp2_priority_spec *pri_spec,

tests/main.c

@@ -154,6 +154,7 @@ int main(int argc _U_, char *argv[] _U_) {
                    test_nghttp2_submit_response_with_data) ||
       !CU_add_test(pSuite, "submit_response_without_data",
                    test_nghttp2_submit_response_without_data) ||
+      !CU_add_test(pSuite, "submit_trailer", test_nghttp2_submit_trailer) ||
       !CU_add_test(pSuite, "submit_headers_start_stream",
                    test_nghttp2_submit_headers_start_stream) ||
       !CU_add_test(pSuite, "submit_headers_reply",

tests/nghttp2_session_test.c

@@ -88,6 +88,13 @@ static const nghttp2_nv resnv[] = {
     MAKE_NV(":status", "200"),
 };
 
+static const nghttp2_nv trailernv[] = {
+    // from http://tools.ietf.org/html/rfc6249#section-7
+    MAKE_NV("digest", "SHA-256="
+                      "MWVkMWQxYTRiMzk5MDQ0MzI3NGU5NDEyZTk5OWY1ZGFmNzgyZTJlODYz"
+                      "YjRjYzFhOTlmNTQwYzI2M2QwM2U2MQ=="),
+};
+
 static void scripted_data_feed_init2(scripted_data_feed *df,
                                      nghttp2_bufs *bufs) {
   nghttp2_buf_chain *ci;
@@ -279,6 +286,14 @@ static ssize_t fail_data_source_read_callback(nghttp2_session *session _U_,
   return NGHTTP2_ERR_CALLBACK_FAILURE;
 }
 
+static ssize_t no_end_stream_data_source_read_callback(
+    nghttp2_session *session _U_, int32_t stream_id _U_, uint8_t *buf _U_,
+    size_t len _U_, uint32_t *data_flags, nghttp2_data_source *source _U_,
+    void *user_data _U_) {
+  *data_flags |= NGHTTP2_DATA_FLAG_EOF | NGHTTP2_DATA_FLAG_NO_END_STREAM;
+  return 0;
+}
+
 /* static void no_stream_user_data_stream_close_callback */
 /* (nghttp2_session *session, */
 /*  int32_t stream_id, */
@@ -3472,6 +3487,63 @@ void test_nghttp2_submit_response_without_data(void) {
   nghttp2_session_del(session);
 }
 
+void test_nghttp2_submit_trailer(void) {
+  nghttp2_session *session;
+  nghttp2_session_callbacks callbacks;
+  accumulator acc;
+  nghttp2_data_provider data_prd;
+  nghttp2_outbound_item *item;
+  my_user_data ud;
+  nghttp2_frame frame;
+  nghttp2_hd_inflater inflater;
+  nva_out out;
+  nghttp2_bufs bufs;
+  nghttp2_mem *mem;
+
+  mem = nghttp2_mem_default();
+  frame_pack_bufs_init(&bufs);
+
+  data_prd.read_callback = no_end_stream_data_source_read_callback;
+  nva_out_init(&out);
+  acc.length = 0;
+  ud.acc = &acc;
+  memset(&callbacks, 0, sizeof(nghttp2_session_callbacks));
+  callbacks.send_callback = null_send_callback;
+  CU_ASSERT(0 == nghttp2_session_server_new(&session, &callbacks, &ud));
+
+  nghttp2_hd_inflate_init(&inflater, mem);
+  nghttp2_session_open_stream(session, 1, NGHTTP2_FLAG_END_STREAM,
+                              &pri_spec_default, NGHTTP2_STREAM_OPENING, NULL);
+  CU_ASSERT(0 == nghttp2_submit_response(session, 1, resnv, ARRLEN(resnv),
+                                         &data_prd));
+  CU_ASSERT(0 == nghttp2_session_send(session));
+
+  CU_ASSERT(0 ==
+            nghttp2_submit_trailer(session, 1, trailernv, ARRLEN(trailernv)));
+
+  session->callbacks.send_callback = accumulator_send_callback;
+
+  item = nghttp2_session_get_next_ob_item(session);
+  CU_ASSERT(NGHTTP2_HEADERS == item->frame.hd.type);
+  CU_ASSERT(NGHTTP2_HCAT_HEADERS == item->frame.headers.cat);
+  CU_ASSERT(item->frame.hd.flags & NGHTTP2_FLAG_END_STREAM);
+
+  CU_ASSERT(0 == nghttp2_session_send(session));
+  CU_ASSERT(0 == unpack_frame(&frame, acc.buf, acc.length));
+
+  nghttp2_bufs_add(&bufs, acc.buf, acc.length);
+  inflate_hd(&inflater, &out, &bufs, NGHTTP2_FRAME_HDLEN, mem);
+
+  CU_ASSERT(ARRLEN(trailernv) == out.nvlen);
+  assert_nv_equal(trailernv, out.nva, out.nvlen, mem);
+
+  nva_out_reset(&out, mem);
+  nghttp2_bufs_free(&bufs);
+  nghttp2_frame_headers_free(&frame.headers, mem);
+  nghttp2_hd_inflate_free(&inflater);
+  nghttp2_session_del(session);
+}
+
 void test_nghttp2_submit_headers_start_stream(void) {
   nghttp2_session *session;
   nghttp2_session_callbacks callbacks;

tests/nghttp2_session_test.h

@@ -69,6 +69,7 @@ void test_nghttp2_submit_request_with_data(void);
 void test_nghttp2_submit_request_without_data(void);
 void test_nghttp2_submit_response_with_data(void);
 void test_nghttp2_submit_response_without_data(void);
+void test_nghttp2_submit_trailer(void);
 void test_nghttp2_submit_headers_start_stream(void);
 void test_nghttp2_submit_headers_reply(void);
 void test_nghttp2_submit_headers_push_reply(void);