1 files changed, 78 insertions, 49 deletions

diff --git a/src/core/ext/transport/chttp2/transport/writing.c b/src/core/ext/transport/chttp2/transport/writing.c
index 5be1092946..315f2a67a2 100644
--- a/src/core/ext/transport/chttp2/transport/writing.c
+++ b/src/core/ext/transport/chttp2/transport/writing.c
@@ -1,33 +1,18 @@
 /*
  *
- * Copyright 2015, Google Inc.
- * All rights reserved.
+ * Copyright 2015 gRPC authors.
  *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met:
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
  *
- *     * Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *     * Redistributions in binary form must reproduce the above
- * copyright notice, this list of conditions and the following disclaimer
- * in the documentation and/or other materials provided with the
- * distribution.
- *     * Neither the name of Google Inc. nor the names of its
- * contributors may be used to endorse or promote products derived from
- * this software without specific prior written permission.
+ *     http://www.apache.org/licenses/LICENSE-2.0
  *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
  *
  */
 
@@ -126,7 +111,7 @@ static void maybe_initiate_ping(grpc_exec_ctx *exec_ctx,
   }
   pq->inflight_id = t->ping_ctr * GRPC_CHTTP2_PING_TYPE_COUNT + ping_type;
   t->ping_ctr++;
-  grpc_closure_list_sched(exec_ctx, &pq->lists[GRPC_CHTTP2_PCL_INITIATE]);
+  GRPC_CLOSURE_LIST_SCHED(exec_ctx, &pq->lists[GRPC_CHTTP2_PCL_INITIATE]);
   grpc_closure_list_move(&pq->lists[GRPC_CHTTP2_PCL_NEXT],
                          &pq->lists[GRPC_CHTTP2_PCL_INFLIGHT]);
   grpc_slice_buffer_add(&t->outbuf,
@@ -177,6 +162,20 @@ static uint32_t target_write_size(grpc_chttp2_transport *t) {
   return 1024 * 1024;
 }
 
+// Returns true if initial_metadata contains only default headers.
+//
+// TODO(roth): The fact that we hard-code these particular headers here
+// is fairly ugly.  Need some better way to know which headers are
+// default, maybe via a bit in the static metadata table?
+static bool is_default_initial_metadata(grpc_metadata_batch *initial_metadata) {
+  int num_default_fields =
+      (initial_metadata->idx.named.status != NULL) +
+      (initial_metadata->idx.named.content_type != NULL) +
+      (initial_metadata->idx.named.grpc_encoding != NULL) +
+      (initial_metadata->idx.named.grpc_accept_encoding != NULL);
+  return (size_t)num_default_fields == initial_metadata->list.count;
+}
+
 grpc_chttp2_begin_write_result grpc_chttp2_begin_write(
     grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t) {
   grpc_chttp2_stream *s;
@@ -206,8 +205,7 @@ grpc_chttp2_begin_write_result grpc_chttp2_begin_write(
     while (grpc_chttp2_list_pop_stalled_by_transport(t, &s)) {
       if (!t->closed && grpc_chttp2_list_add_writable_stream(t, s) &&
           stream_ref_if_not_destroyed(&s->refcount->refs)) {
-        grpc_chttp2_initiate_write(exec_ctx, t, false,
-                                   "transport.read_flow_control");
+        grpc_chttp2_initiate_write(exec_ctx, t, "transport.read_flow_control");
       }
     }
   }
@@ -234,31 +232,59 @@ grpc_chttp2_begin_write_result grpc_chttp2_begin_write(
         t->is_client ? "CLIENT" : "SERVER", s->id, sent_initial_metadata,
         s->send_initial_metadata != NULL, s->announce_window));
 
+    grpc_mdelem *extra_headers_for_trailing_metadata[2];
+    size_t num_extra_headers_for_trailing_metadata = 0;
+
     /* send initial metadata if it's available */
-    if (!sent_initial_metadata && s->send_initial_metadata) {
-      grpc_encode_header_options hopt = {
-          .stream_id = s->id,
-          .is_eof = false,
-          .use_true_binary_metadata =
-              t->settings
-                  [GRPC_PEER_SETTINGS]
-                  [GRPC_CHTTP2_SETTINGS_GRPC_ALLOW_TRUE_BINARY_METADATA] != 0,
-          .max_frame_size = t->settings[GRPC_PEER_SETTINGS]
-                                       [GRPC_CHTTP2_SETTINGS_MAX_FRAME_SIZE],
-          .stats = &s->stats.outgoing};
-      grpc_chttp2_encode_header(exec_ctx, &t->hpack_compressor,
-                                s->send_initial_metadata, &hopt, &t->outbuf);
+    if (!sent_initial_metadata && s->send_initial_metadata != NULL) {
+      // We skip this on the server side if there is no custom initial
+      // metadata, there are no messages to send, and we are also sending
+      // trailing metadata.  This results in a Trailers-Only response,
+      // which is required for retries, as per:
+      // https://github.com/grpc/proposal/blob/master/A6-client-retries.md#when-retries-are-valid
+      if (t->is_client || s->fetching_send_message != NULL ||
+          s->flow_controlled_buffer.length != 0 ||
+          s->send_trailing_metadata == NULL ||
+          !is_default_initial_metadata(s->send_initial_metadata)) {
+        grpc_encode_header_options hopt = {
+            .stream_id = s->id,
+            .is_eof = false,
+            .use_true_binary_metadata =
+                t->settings
+                    [GRPC_PEER_SETTINGS]
+                    [GRPC_CHTTP2_SETTINGS_GRPC_ALLOW_TRUE_BINARY_METADATA] != 0,
+            .max_frame_size = t->settings[GRPC_PEER_SETTINGS]
+                                         [GRPC_CHTTP2_SETTINGS_MAX_FRAME_SIZE],
+            .stats = &s->stats.outgoing};
+        grpc_chttp2_encode_header(exec_ctx, &t->hpack_compressor, NULL, 0,
+                                  s->send_initial_metadata, &hopt, &t->outbuf);
+        now_writing = true;
+        t->ping_state.pings_before_data_required =
+            t->ping_policy.max_pings_without_data;
+        if (!t->is_client) {
+          t->ping_recv_state.last_ping_recv_time =
+              gpr_inf_past(GPR_CLOCK_MONOTONIC);
+          t->ping_recv_state.ping_strikes = 0;
+        }
+      } else {
+        GRPC_CHTTP2_IF_TRACING(
+            gpr_log(GPR_INFO, "not sending initial_metadata (Trailers-Only)"));
+        // When sending Trailers-Only, we need to move the :status and
+        // content-type headers to the trailers.
+        if (s->send_initial_metadata->idx.named.status != NULL) {
+          extra_headers_for_trailing_metadata
+              [num_extra_headers_for_trailing_metadata++] =
+                  &s->send_initial_metadata->idx.named.status->md;
+        }
+        if (s->send_initial_metadata->idx.named.content_type != NULL) {
+          extra_headers_for_trailing_metadata
+              [num_extra_headers_for_trailing_metadata++] =
+                  &s->send_initial_metadata->idx.named.content_type->md;
+        }
+      }
       s->send_initial_metadata = NULL;
       s->sent_initial_metadata = true;
       sent_initial_metadata = true;
-      now_writing = true;
-      t->ping_state.pings_before_data_required =
-          t->ping_policy.max_pings_without_data;
-      if (!t->is_client) {
-        t->ping_recv_state.last_ping_recv_time =
-            gpr_inf_past(GPR_CLOCK_MONOTONIC);
-        t->ping_recv_state.ping_strikes = 0;
-      }
     }
     /* send any window updates */
     if (s->announce_window > 0) {
@@ -336,6 +362,7 @@ grpc_chttp2_begin_write_result grpc_chttp2_begin_write(
       if (s->send_trailing_metadata != NULL &&
           s->fetching_send_message == NULL &&
           s->flow_controlled_buffer.length == 0) {
+        GRPC_CHTTP2_IF_TRACING(gpr_log(GPR_INFO, "sending trailing_metadata"));
         if (grpc_metadata_batch_is_empty(s->send_trailing_metadata)) {
           grpc_chttp2_encode_data(s->id, &s->flow_controlled_buffer, 0, true,
                                   &s->stats.outgoing, &t->outbuf);
@@ -353,6 +380,8 @@ grpc_chttp2_begin_write_result grpc_chttp2_begin_write(
                              [GRPC_CHTTP2_SETTINGS_MAX_FRAME_SIZE],
               .stats = &s->stats.outgoing};
           grpc_chttp2_encode_header(exec_ctx, &t->hpack_compressor,
+                                    extra_headers_for_trailing_metadata,
+                                    num_extra_headers_for_trailing_metadata,
                                     s->send_trailing_metadata, &hopt,
                                     &t->outbuf);
         }