Adding upstream version 1.52.0.upstream/1.52.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2386 insertions, 0 deletions

diff --git a/src/shrpx_http2_upstream.cc b/src/shrpx_http2_upstream.cc
new file mode 100644
index 0000000..9892bad
--- /dev/null
+++ b/src/shrpx_http2_upstream.cc
@@ -0,0 +1,2386 @@
+/*
+ * nghttp2 - HTTP/2 C Library
+ *
+ * Copyright (c) 2012 Tatsuhiro Tsujikawa
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#include "shrpx_http2_upstream.h"
+
+#include <netinet/tcp.h>
+#include <assert.h>
+#include <cerrno>
+#include <sstream>
+
+#include "shrpx_client_handler.h"
+#include "shrpx_https_upstream.h"
+#include "shrpx_downstream.h"
+#include "shrpx_downstream_connection.h"
+#include "shrpx_config.h"
+#include "shrpx_http.h"
+#include "shrpx_worker.h"
+#include "shrpx_http2_session.h"
+#include "shrpx_log.h"
+#ifdef HAVE_MRUBY
+#  include "shrpx_mruby.h"
+#endif // HAVE_MRUBY
+#include "http2.h"
+#include "util.h"
+#include "base64.h"
+#include "app_helper.h"
+#include "template.h"
+
+using namespace nghttp2;
+
+namespace shrpx {
+
+namespace {
+constexpr size_t MAX_BUFFER_SIZE = 32_k;
+} // namespace
+
+namespace {
+int on_stream_close_callback(nghttp2_session *session, int32_t stream_id,
+                             uint32_t error_code, void *user_data) {
+  auto upstream = static_cast<Http2Upstream *>(user_data);
+  if (LOG_ENABLED(INFO)) {
+    ULOG(INFO, upstream) << "Stream stream_id=" << stream_id
+                         << " is being closed";
+  }
+
+  auto downstream = static_cast<Downstream *>(
+      nghttp2_session_get_stream_user_data(session, stream_id));
+
+  if (!downstream) {
+    return 0;
+  }
+
+  auto &req = downstream->request();
+
+  upstream->consume(stream_id, req.unconsumed_body_length);
+
+  req.unconsumed_body_length = 0;
+
+  if (downstream->get_request_state() == DownstreamState::CONNECT_FAIL) {
+    upstream->remove_downstream(downstream);
+    // downstream was deleted
+
+    return 0;
+  }
+
+  if (downstream->can_detach_downstream_connection()) {
+    // Keep-alive
+    downstream->detach_downstream_connection();
+  }
+
+  downstream->set_request_state(DownstreamState::STREAM_CLOSED);
+
+  // At this point, downstream read may be paused.
+
+  // If shrpx_downstream::push_request_headers() failed, the
+  // error is handled here.
+  upstream->remove_downstream(downstream);
+  // downstream was deleted
+
+  // How to test this case? Request sufficient large download
+  // and make client send RST_STREAM after it gets first DATA
+  // frame chunk.
+
+  return 0;
+}
+} // namespace
+
+int Http2Upstream::upgrade_upstream(HttpsUpstream *http) {
+  int rv;
+
+  auto &balloc = http->get_downstream()->get_block_allocator();
+
+  auto http2_settings = http->get_downstream()->get_http2_settings();
+  http2_settings = util::to_base64(balloc, http2_settings);
+
+  auto settings_payload = base64::decode(balloc, std::begin(http2_settings),
+                                         std::end(http2_settings));
+
+  rv = nghttp2_session_upgrade2(
+      session_, settings_payload.byte(), settings_payload.size(),
+      http->get_downstream()->request().method == HTTP_HEAD, nullptr);
+  if (rv != 0) {
+    if (LOG_ENABLED(INFO)) {
+      ULOG(INFO, this) << "nghttp2_session_upgrade() returned error: "
+                       << nghttp2_strerror(rv);
+    }
+    return -1;
+  }
+  pre_upstream_.reset(http);
+  auto downstream = http->pop_downstream();
+  downstream->reset_upstream(this);
+  downstream->set_stream_id(1);
+  downstream->reset_upstream_rtimer();
+  downstream->set_stream_id(1);
+
+  auto ptr = downstream.get();
+
+  nghttp2_session_set_stream_user_data(session_, 1, ptr);
+  downstream_queue_.add_pending(std::move(downstream));
+  downstream_queue_.mark_active(ptr);
+
+  // TODO This might not be necessary
+  handler_->stop_read_timer();
+
+  if (LOG_ENABLED(INFO)) {
+    ULOG(INFO, this) << "Connection upgraded to HTTP/2";
+  }
+
+  return 0;
+}
+
+void Http2Upstream::start_settings_timer() {
+  ev_timer_start(handler_->get_loop(), &settings_timer_);
+}
+
+void Http2Upstream::stop_settings_timer() {
+  ev_timer_stop(handler_->get_loop(), &settings_timer_);
+}
+
+namespace {
+int on_header_callback2(nghttp2_session *session, const nghttp2_frame *frame,
+                        nghttp2_rcbuf *name, nghttp2_rcbuf *value,
+                        uint8_t flags, void *user_data) {
+  auto namebuf = nghttp2_rcbuf_get_buf(name);
+  auto valuebuf = nghttp2_rcbuf_get_buf(value);
+  auto config = get_config();
+
+  if (config->http2.upstream.debug.frame_debug) {
+    verbose_on_header_callback(session, frame, namebuf.base, namebuf.len,
+                               valuebuf.base, valuebuf.len, flags, user_data);
+  }
+  if (frame->hd.type != NGHTTP2_HEADERS) {
+    return 0;
+  }
+  auto upstream = static_cast<Http2Upstream *>(user_data);
+  auto downstream = static_cast<Downstream *>(
+      nghttp2_session_get_stream_user_data(session, frame->hd.stream_id));
+  if (!downstream) {
+    return 0;
+  }
+
+  auto &req = downstream->request();
+
+  auto &httpconf = config->http;
+
+  if (req.fs.buffer_size() + namebuf.len + valuebuf.len >
+          httpconf.request_header_field_buffer ||
+      req.fs.num_fields() >= httpconf.max_request_header_fields) {
+    if (downstream->get_response_state() == DownstreamState::MSG_COMPLETE) {
+      return 0;
+    }
+
+    if (LOG_ENABLED(INFO)) {
+      ULOG(INFO, upstream) << "Too large or many header field size="
+                           << req.fs.buffer_size() + namebuf.len + valuebuf.len
+                           << ", num=" << req.fs.num_fields() + 1;
+    }
+
+    // just ignore header fields if this is trailer part.
+    if (frame->headers.cat == NGHTTP2_HCAT_HEADERS) {
+      return 0;
+    }
+
+    if (upstream->error_reply(downstream, 431) != 0) {
+      return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
+    }
+
+    return 0;
+  }
+
+  auto token = http2::lookup_token(namebuf.base, namebuf.len);
+  auto no_index = flags & NGHTTP2_NV_FLAG_NO_INDEX;
+
+  downstream->add_rcbuf(name);
+  downstream->add_rcbuf(value);
+
+  if (frame->headers.cat == NGHTTP2_HCAT_HEADERS) {
+    // just store header fields for trailer part
+    req.fs.add_trailer_token(StringRef{namebuf.base, namebuf.len},
+                             StringRef{valuebuf.base, valuebuf.len}, no_index,
+                             token);
+    return 0;
+  }
+
+  req.fs.add_header_token(StringRef{namebuf.base, namebuf.len},
+                          StringRef{valuebuf.base, valuebuf.len}, no_index,
+                          token);
+  return 0;
+}
+} // namespace
+
+namespace {
+int on_invalid_header_callback2(nghttp2_session *session,
+                                const nghttp2_frame *frame, nghttp2_rcbuf *name,
+                                nghttp2_rcbuf *value, uint8_t flags,
+                                void *user_data) {
+  auto upstream = static_cast<Http2Upstream *>(user_data);
+  auto downstream = static_cast<Downstream *>(
+      nghttp2_session_get_stream_user_data(session, frame->hd.stream_id));
+  if (!downstream) {
+    return 0;
+  }
+
+  if (LOG_ENABLED(INFO)) {
+    auto namebuf = nghttp2_rcbuf_get_buf(name);
+    auto valuebuf = nghttp2_rcbuf_get_buf(value);
+
+    ULOG(INFO, upstream) << "Invalid header field for stream_id="
+                         << frame->hd.stream_id << ": name=["
+                         << StringRef{namebuf.base, namebuf.len} << "], value=["
+                         << StringRef{valuebuf.base, valuebuf.len} << "]";
+  }
+
+  upstream->rst_stream(downstream, NGHTTP2_PROTOCOL_ERROR);
+
+  return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
+}
+} // namespace
+
+namespace {
+int on_begin_headers_callback(nghttp2_session *session,
+                              const nghttp2_frame *frame, void *user_data) {
+  auto upstream = static_cast<Http2Upstream *>(user_data);
+
+  if (frame->headers.cat != NGHTTP2_HCAT_REQUEST) {
+    return 0;
+  }
+  if (LOG_ENABLED(INFO)) {
+    ULOG(INFO, upstream) << "Received upstream request HEADERS stream_id="
+                         << frame->hd.stream_id;
+  }
+
+  upstream->on_start_request(frame);
+
+  return 0;
+}
+} // namespace
+
+void Http2Upstream::on_start_request(const nghttp2_frame *frame) {
+  auto downstream = std::make_unique<Downstream>(this, handler_->get_mcpool(),
+                                                 frame->hd.stream_id);
+  nghttp2_session_set_stream_user_data(session_, frame->hd.stream_id,
+                                       downstream.get());
+
+  downstream->reset_upstream_rtimer();
+
+  handler_->repeat_read_timer();
+
+  auto &req = downstream->request();
+
+  // Although, we deprecated minor version from HTTP/2, we supply
+  // minor version 0 to use via header field in a conventional way.
+  req.http_major = 2;
+  req.http_minor = 0;
+
+  add_pending_downstream(std::move(downstream));
+
+  ++num_requests_;
+
+  auto config = get_config();
+  auto &httpconf = config->http;
+  if (httpconf.max_requests <= num_requests_) {
+    start_graceful_shutdown();
+  }
+}
+
+int Http2Upstream::on_request_headers(Downstream *downstream,
+                                      const nghttp2_frame *frame) {
+  auto lgconf = log_config();
+  lgconf->update_tstamp(std::chrono::system_clock::now());
+  auto &req = downstream->request();
+  req.tstamp = lgconf->tstamp;
+
+  if (downstream->get_response_state() == DownstreamState::MSG_COMPLETE) {
+    return 0;
+  }
+
+  auto &nva = req.fs.headers();
+
+  if (LOG_ENABLED(INFO)) {
+    std::stringstream ss;
+    for (auto &nv : nva) {
+      if (nv.name == "authorization") {
+        ss << TTY_HTTP_HD << nv.name << TTY_RST << ": <redacted>\n";
+        continue;
+      }
+      ss << TTY_HTTP_HD << nv.name << TTY_RST << ": " << nv.value << "\n";
+    }
+    ULOG(INFO, this) << "HTTP request headers. stream_id="
+                     << downstream->get_stream_id() << "\n"
+                     << ss.str();
+  }
+
+  auto config = get_config();
+  auto &dump = config->http2.upstream.debug.dump;
+
+  if (dump.request_header) {
+    http2::dump_nv(dump.request_header, nva);
+  }
+
+  auto content_length = req.fs.header(http2::HD_CONTENT_LENGTH);
+  if (content_length) {
+    // libnghttp2 guarantees this can be parsed
+    req.fs.content_length = util::parse_uint(content_length->value);
+  }
+
+  // presence of mandatory header fields are guaranteed by libnghttp2.
+  auto authority = req.fs.header(http2::HD__AUTHORITY);
+  auto path = req.fs.header(http2::HD__PATH);
+  auto method = req.fs.header(http2::HD__METHOD);
+  auto scheme = req.fs.header(http2::HD__SCHEME);
+
+  auto method_token = http2::lookup_method_token(method->value);
+  if (method_token == -1) {
+    if (error_reply(downstream, 501) != 0) {
+      return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
+    }
+    return 0;
+  }
+
+  auto faddr = handler_->get_upstream_addr();
+
+  // For HTTP/2 proxy, we require :authority.
+  if (method_token != HTTP_CONNECT && config->http2_proxy &&
+      faddr->alt_mode == UpstreamAltMode::NONE && !authority) {
+    rst_stream(downstream, NGHTTP2_PROTOCOL_ERROR);
+    return 0;
+  }
+
+  req.method = method_token;
+  if (scheme) {
+    req.scheme = scheme->value;
+  }
+
+  // nghttp2 library guarantees either :authority or host exist
+  if (!authority) {
+    req.no_authority = true;
+    authority = req.fs.header(http2::HD_HOST);
+  }
+
+  if (authority) {
+    req.authority = authority->value;
+  }
+
+  if (path) {
+    if (method_token == HTTP_OPTIONS &&
+        path->value == StringRef::from_lit("*")) {
+      // Server-wide OPTIONS request.  Path is empty.
+    } else if (config->http2_proxy &&
+               faddr->alt_mode == UpstreamAltMode::NONE) {
+      req.path = path->value;
+    } else {
+      req.path = http2::rewrite_clean_path(downstream->get_block_allocator(),
+                                           path->value);
+    }
+  }
+
+  auto connect_proto = req.fs.header(http2::HD__PROTOCOL);
+  if (connect_proto) {
+    if (connect_proto->value != "websocket") {
+      if (error_reply(downstream, 400) != 0) {
+        return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
+      }
+      return 0;
+    }
+    req.connect_proto = ConnectProto::WEBSOCKET;
+  }
+
+  if (!(frame->hd.flags & NGHTTP2_FLAG_END_STREAM)) {
+    req.http2_expect_body = true;
+  } else if (req.fs.content_length == -1) {
+    // If END_STREAM flag is set to HEADERS frame, we are sure that
+    // content-length is 0.
+    req.fs.content_length = 0;
+  }
+
+  downstream->inspect_http2_request();
+
+  downstream->set_request_state(DownstreamState::HEADER_COMPLETE);
+
+  if (config->http.require_http_scheme &&
+      !http::check_http_scheme(req.scheme, handler_->get_ssl() != nullptr)) {
+    if (error_reply(downstream, 400) != 0) {
+      return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
+    }
+    return 0;
+  }
+
+#ifdef HAVE_MRUBY
+  auto worker = handler_->get_worker();
+  auto mruby_ctx = worker->get_mruby_context();
+
+  if (mruby_ctx->run_on_request_proc(downstream) != 0) {
+    if (error_reply(downstream, 500) != 0) {
+      return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
+    }
+    return 0;
+  }
+#endif // HAVE_MRUBY
+
+  if (frame->hd.flags & NGHTTP2_FLAG_END_STREAM) {
+    downstream->disable_upstream_rtimer();
+
+    downstream->set_request_state(DownstreamState::MSG_COMPLETE);
+  }
+
+  if (downstream->get_response_state() == DownstreamState::MSG_COMPLETE) {
+    return 0;
+  }
+
+  start_downstream(downstream);
+
+  return 0;
+}
+
+void Http2Upstream::start_downstream(Downstream *downstream) {
+  if (downstream_queue_.can_activate(downstream->request().authority)) {
+    initiate_downstream(downstream);
+    return;
+  }
+
+  downstream_queue_.mark_blocked(downstream);
+}
+
+void Http2Upstream::initiate_downstream(Downstream *downstream) {
+  int rv;
+
+#ifdef HAVE_MRUBY
+  DownstreamConnection *dconn_ptr;
+#endif // HAVE_MRUBY
+
+  for (;;) {
+    auto dconn = handler_->get_downstream_connection(rv, downstream);
+    if (!dconn) {
+      if (rv == SHRPX_ERR_TLS_REQUIRED) {
+        rv = redirect_to_https(downstream);
+      } else {
+        rv = error_reply(downstream, 502);
+      }
+      if (rv != 0) {
+        rst_stream(downstream, NGHTTP2_INTERNAL_ERROR);
+      }
+
+      downstream->set_request_state(DownstreamState::CONNECT_FAIL);
+      downstream_queue_.mark_failure(downstream);
+
+      return;
+    }
+
+#ifdef HAVE_MRUBY
+    dconn_ptr = dconn.get();
+#endif // HAVE_MRUBY
+    rv = downstream->attach_downstream_connection(std::move(dconn));
+    if (rv == 0) {
+      break;
+    }
+  }
+
+#ifdef HAVE_MRUBY
+  const auto &group = dconn_ptr->get_downstream_addr_group();
+  if (group) {
+    const auto &mruby_ctx = group->shared_addr->mruby_ctx;
+    if (mruby_ctx->run_on_request_proc(downstream) != 0) {
+      if (error_reply(downstream, 500) != 0) {
+        rst_stream(downstream, NGHTTP2_INTERNAL_ERROR);
+      }
+
+      downstream_queue_.mark_failure(downstream);
+
+      return;
+    }
+
+    if (downstream->get_response_state() == DownstreamState::MSG_COMPLETE) {
+      return;
+    }
+  }
+#endif // HAVE_MRUBY
+
+  rv = downstream->push_request_headers();
+  if (rv != 0) {
+
+    if (error_reply(downstream, 502) != 0) {
+      rst_stream(downstream, NGHTTP2_INTERNAL_ERROR);
+    }
+
+    downstream_queue_.mark_failure(downstream);
+
+    return;
+  }
+
+  downstream_queue_.mark_active(downstream);
+
+  auto &req = downstream->request();
+  if (!req.http2_expect_body) {
+    rv = downstream->end_upload_data();
+    if (rv != 0) {
+      rst_stream(downstream, NGHTTP2_INTERNAL_ERROR);
+    }
+  }
+
+  return;
+}
+
+namespace {
+int on_frame_recv_callback(nghttp2_session *session, const nghttp2_frame *frame,
+                           void *user_data) {
+  if (get_config()->http2.upstream.debug.frame_debug) {
+    verbose_on_frame_recv_callback(session, frame, user_data);
+  }
+  auto upstream = static_cast<Http2Upstream *>(user_data);
+  auto handler = upstream->get_client_handler();
+
+  switch (frame->hd.type) {
+  case NGHTTP2_DATA: {
+    auto downstream = static_cast<Downstream *>(
+        nghttp2_session_get_stream_user_data(session, frame->hd.stream_id));
+    if (!downstream) {
+      return 0;
+    }
+
+    if (frame->hd.flags & NGHTTP2_FLAG_END_STREAM) {
+      downstream->disable_upstream_rtimer();
+
+      if (downstream->end_upload_data() != 0) {
+        if (downstream->get_response_state() != DownstreamState::MSG_COMPLETE) {
+          upstream->rst_stream(downstream, NGHTTP2_INTERNAL_ERROR);
+        }
+      }
+
+      downstream->set_request_state(DownstreamState::MSG_COMPLETE);
+    }
+
+    return 0;
+  }
+  case NGHTTP2_HEADERS: {
+    auto downstream = static_cast<Downstream *>(
+        nghttp2_session_get_stream_user_data(session, frame->hd.stream_id));
+    if (!downstream) {
+      return 0;
+    }
+
+    if (frame->headers.cat == NGHTTP2_HCAT_REQUEST) {
+      downstream->reset_upstream_rtimer();
+
+      handler->stop_read_timer();
+
+      return upstream->on_request_headers(downstream, frame);
+    }
+
+    if (frame->hd.flags & NGHTTP2_FLAG_END_STREAM) {
+      downstream->disable_upstream_rtimer();
+
+      if (downstream->end_upload_data() != 0) {
+        if (downstream->get_response_state() != DownstreamState::MSG_COMPLETE) {
+          upstream->rst_stream(downstream, NGHTTP2_INTERNAL_ERROR);
+        }
+      }
+
+      downstream->set_request_state(DownstreamState::MSG_COMPLETE);
+    }
+
+    return 0;
+  }
+  case NGHTTP2_SETTINGS:
+    if ((frame->hd.flags & NGHTTP2_FLAG_ACK) == 0) {
+      return 0;
+    }
+    upstream->stop_settings_timer();
+    return 0;
+  case NGHTTP2_GOAWAY:
+    if (LOG_ENABLED(INFO)) {
+      auto debug_data = util::ascii_dump(frame->goaway.opaque_data,
+                                         frame->goaway.opaque_data_len);
+
+      ULOG(INFO, upstream) << "GOAWAY received: last-stream-id="
+                           << frame->goaway.last_stream_id
+                           << ", error_code=" << frame->goaway.error_code
+                           << ", debug_data=" << debug_data;
+    }
+    return 0;
+  default:
+    return 0;
+  }
+}
+} // namespace
+
+namespace {
+int on_data_chunk_recv_callback(nghttp2_session *session, uint8_t flags,
+                                int32_t stream_id, const uint8_t *data,
+                                size_t len, void *user_data) {
+  auto upstream = static_cast<Http2Upstream *>(user_data);
+  auto downstream = static_cast<Downstream *>(
+      nghttp2_session_get_stream_user_data(session, stream_id));
+
+  if (!downstream) {
+    if (upstream->consume(stream_id, len) != 0) {
+      return NGHTTP2_ERR_CALLBACK_FAILURE;
+    }
+
+    return 0;
+  }
+
+  downstream->reset_upstream_rtimer();
+
+  if (downstream->push_upload_data_chunk(data, len) != 0) {
+    if (downstream->get_response_state() != DownstreamState::MSG_COMPLETE) {
+      upstream->rst_stream(downstream, NGHTTP2_INTERNAL_ERROR);
+    }
+
+    if (upstream->consume(stream_id, len) != 0) {
+      return NGHTTP2_ERR_CALLBACK_FAILURE;
+    }
+
+    return 0;
+  }
+
+  return 0;
+}
+} // namespace
+
+namespace {
+int on_frame_send_callback(nghttp2_session *session, const nghttp2_frame *frame,
+                           void *user_data) {
+  if (get_config()->http2.upstream.debug.frame_debug) {
+    verbose_on_frame_send_callback(session, frame, user_data);
+  }
+  auto upstream = static_cast<Http2Upstream *>(user_data);
+  auto handler = upstream->get_client_handler();
+
+  switch (frame->hd.type) {
+  case NGHTTP2_DATA:
+  case NGHTTP2_HEADERS: {
+    if ((frame->hd.flags & NGHTTP2_FLAG_END_STREAM) == 0) {
+      return 0;
+    }
+    // RST_STREAM if request is still incomplete.
+    auto stream_id = frame->hd.stream_id;
+    auto downstream = static_cast<Downstream *>(
+        nghttp2_session_get_stream_user_data(session, stream_id));
+
+    if (!downstream) {
+      return 0;
+    }
+
+    // For tunneling, issue RST_STREAM to finish the stream.
+    if (downstream->get_upgraded() ||
+        nghttp2_session_get_stream_remote_close(session, stream_id) == 0) {
+      if (LOG_ENABLED(INFO)) {
+        ULOG(INFO, upstream)
+            << "Send RST_STREAM to "
+            << (downstream->get_upgraded() ? "tunneled " : "")
+            << "stream stream_id=" << downstream->get_stream_id()
+            << " to finish off incomplete request";
+      }
+
+      upstream->rst_stream(downstream, NGHTTP2_NO_ERROR);
+    }
+
+    return 0;
+  }
+  case NGHTTP2_SETTINGS:
+    if ((frame->hd.flags & NGHTTP2_FLAG_ACK) == 0) {
+      upstream->start_settings_timer();
+    }
+    return 0;
+  case NGHTTP2_PUSH_PROMISE: {
+    auto promised_stream_id = frame->push_promise.promised_stream_id;
+
+    if (nghttp2_session_get_stream_user_data(session, promised_stream_id)) {
+      // In case of push from backend, downstream object was already
+      // created.
+      return 0;
+    }
+
+    auto promised_downstream = std::make_unique<Downstream>(
+        upstream, handler->get_mcpool(), promised_stream_id);
+    auto &req = promised_downstream->request();
+
+    // As long as we use nghttp2_session_mem_send(), setting stream
+    // user data here should not fail.  This is because this callback
+    // is called just after frame was serialized.  So no worries about
+    // hanging Downstream.
+    nghttp2_session_set_stream_user_data(session, promised_stream_id,
+                                         promised_downstream.get());
+
+    promised_downstream->set_assoc_stream_id(frame->hd.stream_id);
+    promised_downstream->disable_upstream_rtimer();
+
+    req.http_major = 2;
+    req.http_minor = 0;
+
+    req.fs.content_length = 0;
+    req.http2_expect_body = false;
+
+    auto &promised_balloc = promised_downstream->get_block_allocator();
+
+    for (size_t i = 0; i < frame->push_promise.nvlen; ++i) {
+      auto &nv = frame->push_promise.nva[i];
+
+      auto name =
+          make_string_ref(promised_balloc, StringRef{nv.name, nv.namelen});
+      auto value =
+          make_string_ref(promised_balloc, StringRef{nv.value, nv.valuelen});
+
+      auto token = http2::lookup_token(nv.name, nv.namelen);
+      switch (token) {
+      case http2::HD__METHOD:
+        req.method = http2::lookup_method_token(value);
+        break;
+      case http2::HD__SCHEME:
+        req.scheme = value;
+        break;
+      case http2::HD__AUTHORITY:
+        req.authority = value;
+        break;
+      case http2::HD__PATH:
+        req.path = http2::rewrite_clean_path(promised_balloc, value);
+        break;
+      }
+      req.fs.add_header_token(name, value, nv.flags & NGHTTP2_NV_FLAG_NO_INDEX,
+                              token);
+    }
+
+    promised_downstream->inspect_http2_request();
+
+    promised_downstream->set_request_state(DownstreamState::MSG_COMPLETE);
+
+    // a bit weird but start_downstream() expects that given
+    // downstream is in pending queue.
+    auto ptr = promised_downstream.get();
+    upstream->add_pending_downstream(std::move(promised_downstream));
+
+#ifdef HAVE_MRUBY
+    auto worker = handler->get_worker();
+    auto mruby_ctx = worker->get_mruby_context();
+
+    if (mruby_ctx->run_on_request_proc(ptr) != 0) {
+      if (upstream->error_reply(ptr, 500) != 0) {
+        upstream->rst_stream(ptr, NGHTTP2_INTERNAL_ERROR);
+        return 0;
+      }
+      return 0;
+    }
+#endif // HAVE_MRUBY
+
+    upstream->start_downstream(ptr);
+
+    return 0;
+  }
+  case NGHTTP2_GOAWAY:
+    if (LOG_ENABLED(INFO)) {
+      auto debug_data = util::ascii_dump(frame->goaway.opaque_data,
+                                         frame->goaway.opaque_data_len);
+
+      ULOG(INFO, upstream) << "Sending GOAWAY: last-stream-id="
+                           << frame->goaway.last_stream_id
+                           << ", error_code=" << frame->goaway.error_code
+                           << ", debug_data=" << debug_data;
+    }
+    return 0;
+  default:
+    return 0;
+  }
+}
+} // namespace
+
+namespace {
+int on_frame_not_send_callback(nghttp2_session *session,
+                               const nghttp2_frame *frame, int lib_error_code,
+                               void *user_data) {
+  auto upstream = static_cast<Http2Upstream *>(user_data);
+  if (LOG_ENABLED(INFO)) {
+    ULOG(INFO, upstream) << "Failed to send control frame type="
+                         << static_cast<uint32_t>(frame->hd.type)
+                         << ", lib_error_code=" << lib_error_code << ":"
+                         << nghttp2_strerror(lib_error_code);
+  }
+  if (frame->hd.type == NGHTTP2_HEADERS &&
+      lib_error_code != NGHTTP2_ERR_STREAM_CLOSED &&
+      lib_error_code != NGHTTP2_ERR_STREAM_CLOSING) {
+    // To avoid stream hanging around, issue RST_STREAM.
+    auto downstream = static_cast<Downstream *>(
+        nghttp2_session_get_stream_user_data(session, frame->hd.stream_id));
+    if (downstream) {
+      upstream->rst_stream(downstream, NGHTTP2_INTERNAL_ERROR);
+    }
+  }
+  return 0;
+}
+} // namespace
+
+namespace {
+constexpr auto PADDING = std::array<uint8_t, 256>{};
+} // namespace
+
+namespace {
+int send_data_callback(nghttp2_session *session, nghttp2_frame *frame,
+                       const uint8_t *framehd, size_t length,
+                       nghttp2_data_source *source, void *user_data) {
+  auto downstream = static_cast<Downstream *>(source->ptr);
+  auto upstream = static_cast<Http2Upstream *>(downstream->get_upstream());
+  auto body = downstream->get_response_buf();
+
+  auto wb = upstream->get_response_buf();
+
+  size_t padlen = 0;
+
+  wb->append(framehd, 9);
+  if (frame->data.padlen > 0) {
+    padlen = frame->data.padlen - 1;
+    wb->append(static_cast<uint8_t>(padlen));
+  }
+
+  body->remove(*wb, length);
+
+  wb->append(PADDING.data(), padlen);
+
+  if (body->rleft() == 0) {
+    downstream->disable_upstream_wtimer();
+  } else {
+    downstream->reset_upstream_wtimer();
+  }
+
+  if (length > 0 && downstream->resume_read(SHRPX_NO_BUFFER, length) != 0) {
+    return NGHTTP2_ERR_CALLBACK_FAILURE;
+  }
+
+  // We have to add length here, so that we can log this amount of
+  // data transferred.
+  downstream->response_sent_body_length += length;
+
+  auto max_buffer_size = upstream->get_max_buffer_size();
+
+  return wb->rleft() >= max_buffer_size ? NGHTTP2_ERR_PAUSE : 0;
+}
+} // namespace
+
+namespace {
+uint32_t infer_upstream_rst_stream_error_code(uint32_t downstream_error_code) {
+  // NGHTTP2_REFUSED_STREAM is important because it tells upstream
+  // client to retry.
+  switch (downstream_error_code) {
+  case NGHTTP2_NO_ERROR:
+  case NGHTTP2_REFUSED_STREAM:
+    return downstream_error_code;
+  default:
+    return NGHTTP2_INTERNAL_ERROR;
+  }
+}
+} // namespace
+
+namespace {
+void settings_timeout_cb(struct ev_loop *loop, ev_timer *w, int revents) {
+  auto upstream = static_cast<Http2Upstream *>(w->data);
+  auto handler = upstream->get_client_handler();
+  ULOG(INFO, upstream) << "SETTINGS timeout";
+  if (upstream->terminate_session(NGHTTP2_SETTINGS_TIMEOUT) != 0) {
+    delete handler;
+    return;
+  }
+  handler->signal_write();
+}
+} // namespace
+
+namespace {
+void shutdown_timeout_cb(struct ev_loop *loop, ev_timer *w, int revents) {
+  auto upstream = static_cast<Http2Upstream *>(w->data);
+  auto handler = upstream->get_client_handler();
+  upstream->submit_goaway();
+  handler->signal_write();
+}
+} // namespace
+
+namespace {
+void prepare_cb(struct ev_loop *loop, ev_prepare *w, int revents) {
+  auto upstream = static_cast<Http2Upstream *>(w->data);
+  upstream->check_shutdown();
+}
+} // namespace
+
+void Http2Upstream::submit_goaway() {
+  auto last_stream_id = nghttp2_session_get_last_proc_stream_id(session_);
+  nghttp2_submit_goaway(session_, NGHTTP2_FLAG_NONE, last_stream_id,
+                        NGHTTP2_NO_ERROR, nullptr, 0);
+}
+
+void Http2Upstream::check_shutdown() {
+  auto worker = handler_->get_worker();
+
+  if (!worker->get_graceful_shutdown()) {
+    return;
+  }
+
+  ev_prepare_stop(handler_->get_loop(), &prep_);
+
+  start_graceful_shutdown();
+}
+
+void Http2Upstream::start_graceful_shutdown() {
+  int rv;
+  if (ev_is_active(&shutdown_timer_)) {
+    return;
+  }
+
+  rv = nghttp2_submit_shutdown_notice(session_);
+  if (rv != 0) {
+    ULOG(FATAL, this) << "nghttp2_submit_shutdown_notice() failed: "
+                      << nghttp2_strerror(rv);
+    return;
+  }
+
+  handler_->signal_write();
+
+  ev_timer_start(handler_->get_loop(), &shutdown_timer_);
+}
+
+nghttp2_session_callbacks *create_http2_upstream_callbacks() {
+  int rv;
+  nghttp2_session_callbacks *callbacks;
+
+  rv = nghttp2_session_callbacks_new(&callbacks);
+
+  if (rv != 0) {
+    return nullptr;
+  }
+
+  nghttp2_session_callbacks_set_on_stream_close_callback(
+      callbacks, on_stream_close_callback);
+
+  nghttp2_session_callbacks_set_on_frame_recv_callback(callbacks,
+                                                       on_frame_recv_callback);
+
+  nghttp2_session_callbacks_set_on_data_chunk_recv_callback(
+      callbacks, on_data_chunk_recv_callback);
+
+  nghttp2_session_callbacks_set_on_frame_send_callback(callbacks,
+                                                       on_frame_send_callback);
+
+  nghttp2_session_callbacks_set_on_frame_not_send_callback(
+      callbacks, on_frame_not_send_callback);
+
+  nghttp2_session_callbacks_set_on_header_callback2(callbacks,
+                                                    on_header_callback2);
+
+  nghttp2_session_callbacks_set_on_invalid_header_callback2(
+      callbacks, on_invalid_header_callback2);
+
+  nghttp2_session_callbacks_set_on_begin_headers_callback(
+      callbacks, on_begin_headers_callback);
+
+  nghttp2_session_callbacks_set_send_data_callback(callbacks,
+                                                   send_data_callback);
+
+  auto config = get_config();
+
+  if (config->padding) {
+    nghttp2_session_callbacks_set_select_padding_callback(
+        callbacks, http::select_padding_callback);
+  }
+
+  if (config->http2.upstream.debug.frame_debug) {
+    nghttp2_session_callbacks_set_error_callback2(callbacks,
+                                                  verbose_error_callback);
+  }
+
+  return callbacks;
+}
+
+namespace {
+size_t downstream_queue_size(Worker *worker) {
+  auto &downstreamconf = *worker->get_downstream_config();
+
+  if (get_config()->http2_proxy) {
+    return downstreamconf.connections_per_host;
+  }
+
+  return downstreamconf.connections_per_frontend;
+}
+} // namespace
+
+Http2Upstream::Http2Upstream(ClientHandler *handler)
+    : wb_(handler->get_worker()->get_mcpool()),
+      downstream_queue_(downstream_queue_size(handler->get_worker()),
+                        !get_config()->http2_proxy),
+      handler_(handler),
+      session_(nullptr),
+      max_buffer_size_(MAX_BUFFER_SIZE),
+      num_requests_(0) {
+  int rv;
+
+  auto config = get_config();
+  auto &http2conf = config->http2;
+
+  auto faddr = handler_->get_upstream_addr();
+
+  rv =
+      nghttp2_session_server_new2(&session_, http2conf.upstream.callbacks, this,
+                                  faddr->alt_mode != UpstreamAltMode::NONE
+                                      ? http2conf.upstream.alt_mode_option
+                                      : http2conf.upstream.option);
+
+  assert(rv == 0);
+
+  flow_control_ = true;
+
+  // TODO Maybe call from outside?
+  std::array<nghttp2_settings_entry, 5> entry;
+  size_t nentry = 3;
+
+  entry[0].settings_id = NGHTTP2_SETTINGS_MAX_CONCURRENT_STREAMS;
+  entry[0].value = http2conf.upstream.max_concurrent_streams;
+
+  entry[1].settings_id = NGHTTP2_SETTINGS_INITIAL_WINDOW_SIZE;
+  if (faddr->alt_mode != UpstreamAltMode::NONE) {
+    entry[1].value = (1u << 31) - 1;
+  } else {
+    entry[1].value = http2conf.upstream.window_size;
+  }
+
+  entry[2].settings_id = NGHTTP2_SETTINGS_NO_RFC7540_PRIORITIES;
+  entry[2].value = 1;
+
+  if (!config->http2_proxy) {
+    entry[nentry].settings_id = NGHTTP2_SETTINGS_ENABLE_CONNECT_PROTOCOL;
+    entry[nentry].value = 1;
+    ++nentry;
+  }
+
+  if (http2conf.upstream.decoder_dynamic_table_size !=
+      NGHTTP2_DEFAULT_HEADER_TABLE_SIZE) {
+    entry[nentry].settings_id = NGHTTP2_SETTINGS_HEADER_TABLE_SIZE;
+    entry[nentry].value = http2conf.upstream.decoder_dynamic_table_size;
+    ++nentry;
+  }
+
+  rv = nghttp2_submit_settings(session_, NGHTTP2_FLAG_NONE, entry.data(),
+                               nentry);
+  if (rv != 0) {
+    ULOG(ERROR, this) << "nghttp2_submit_settings() returned error: "
+                      << nghttp2_strerror(rv);
+  }
+
+  auto window_size = faddr->alt_mode != UpstreamAltMode::NONE
+                         ? std::numeric_limits<int32_t>::max()
+                     : http2conf.upstream.optimize_window_size
+                         ? std::min(http2conf.upstream.connection_window_size,
+                                    NGHTTP2_INITIAL_CONNECTION_WINDOW_SIZE)
+                         : http2conf.upstream.connection_window_size;
+
+  rv = nghttp2_session_set_local_window_size(session_, NGHTTP2_FLAG_NONE, 0,
+                                             window_size);
+
+  if (rv != 0) {
+    ULOG(ERROR, this)
+        << "nghttp2_session_set_local_window_size() returned error: "
+        << nghttp2_strerror(rv);
+  }
+
+  // We wait for SETTINGS ACK at least 10 seconds.
+  ev_timer_init(&settings_timer_, settings_timeout_cb,
+                http2conf.upstream.timeout.settings, 0.);
+
+  settings_timer_.data = this;
+
+  // timer for 2nd GOAWAY.  HTTP/2 spec recommend 1 RTT.  We wait for
+  // 2 seconds.
+  ev_timer_init(&shutdown_timer_, shutdown_timeout_cb, 2., 0);
+  shutdown_timer_.data = this;
+
+  ev_prepare_init(&prep_, prepare_cb);
+  prep_.data = this;
+  ev_prepare_start(handler_->get_loop(), &prep_);
+
+#if defined(TCP_INFO) && defined(TCP_NOTSENT_LOWAT)
+  if (http2conf.upstream.optimize_write_buffer_size) {
+    auto conn = handler_->get_connection();
+    conn->tls_dyn_rec_warmup_threshold = 0;
+
+    uint32_t pollout_thres = 1;
+    rv = setsockopt(conn->fd, IPPROTO_TCP, TCP_NOTSENT_LOWAT, &pollout_thres,
+                    static_cast<socklen_t>(sizeof(pollout_thres)));
+
+    if (rv != 0) {
+      if (LOG_ENABLED(INFO)) {
+        auto error = errno;
+        LOG(INFO) << "setsockopt(TCP_NOTSENT_LOWAT, " << pollout_thres
+                  << ") failed: errno=" << error;
+      }
+    }
+  }
+#endif // defined(TCP_INFO) && defined(TCP_NOTSENT_LOWAT)
+
+  handler_->reset_upstream_read_timeout(
+      config->conn.upstream.timeout.http2_read);
+
+  handler_->signal_write();
+}
+
+Http2Upstream::~Http2Upstream() {
+  nghttp2_session_del(session_);
+  ev_prepare_stop(handler_->get_loop(), &prep_);
+  ev_timer_stop(handler_->get_loop(), &shutdown_timer_);
+  ev_timer_stop(handler_->get_loop(), &settings_timer_);
+}
+
+int Http2Upstream::on_read() {
+  ssize_t rv = 0;
+  auto rb = handler_->get_rb();
+  auto rlimit = handler_->get_rlimit();
+
+  if (rb->rleft()) {
+    rv = nghttp2_session_mem_recv(session_, rb->pos(), rb->rleft());
+    if (rv < 0) {
+      if (rv != NGHTTP2_ERR_BAD_CLIENT_MAGIC) {
+        ULOG(ERROR, this) << "nghttp2_session_mem_recv() returned error: "
+                          << nghttp2_strerror(rv);
+      }
+      return -1;
+    }
+
+    // nghttp2_session_mem_recv should consume all input bytes on
+    // success.
+    assert(static_cast<size_t>(rv) == rb->rleft());
+    rb->reset();
+    rlimit->startw();
+  }
+
+  if (nghttp2_session_want_read(session_) == 0 &&
+      nghttp2_session_want_write(session_) == 0 && wb_.rleft() == 0) {
+    if (LOG_ENABLED(INFO)) {
+      ULOG(INFO, this) << "No more read/write for this HTTP2 session";
+    }
+    return -1;
+  }
+
+  handler_->signal_write();
+  return 0;
+}
+
+// After this function call, downstream may be deleted.
+int Http2Upstream::on_write() {
+  int rv;
+  auto config = get_config();
+  auto &http2conf = config->http2;
+
+  if ((http2conf.upstream.optimize_write_buffer_size ||
+       http2conf.upstream.optimize_window_size) &&
+      handler_->get_ssl()) {
+    auto conn = handler_->get_connection();
+    TCPHint hint;
+    rv = conn->get_tcp_hint(&hint);
+    if (rv == 0) {
+      if (http2conf.upstream.optimize_write_buffer_size) {
+        max_buffer_size_ = std::min(MAX_BUFFER_SIZE, hint.write_buffer_size);
+      }
+
+      if (http2conf.upstream.optimize_window_size) {
+        auto faddr = handler_->get_upstream_addr();
+        if (faddr->alt_mode == UpstreamAltMode::NONE) {
+          auto window_size = std::min(http2conf.upstream.connection_window_size,
+                                      static_cast<int32_t>(hint.rwin * 2));
+
+          rv = nghttp2_session_set_local_window_size(
+              session_, NGHTTP2_FLAG_NONE, 0, window_size);
+          if (rv != 0) {
+            if (LOG_ENABLED(INFO)) {
+              ULOG(INFO, this)
+                  << "nghttp2_session_set_local_window_size() with window_size="
+                  << window_size << " failed: " << nghttp2_strerror(rv);
+            }
+          }
+        }
+      }
+    }
+  }
+
+  for (;;) {
+    if (wb_.rleft() >= max_buffer_size_) {
+      return 0;
+    }
+
+    const uint8_t *data;
+    auto datalen = nghttp2_session_mem_send(session_, &data);
+
+    if (datalen < 0) {
+      ULOG(ERROR, this) << "nghttp2_session_mem_send() returned error: "
+                        << nghttp2_strerror(datalen);
+      return -1;
+    }
+    if (datalen == 0) {
+      break;
+    }
+    wb_.append(data, datalen);
+  }
+
+  if (nghttp2_session_want_read(session_) == 0 &&
+      nghttp2_session_want_write(session_) == 0 && wb_.rleft() == 0) {
+    if (LOG_ENABLED(INFO)) {
+      ULOG(INFO, this) << "No more read/write for this HTTP2 session";
+    }
+    return -1;
+  }
+
+  return 0;
+}
+
+ClientHandler *Http2Upstream::get_client_handler() const { return handler_; }
+
+int Http2Upstream::downstream_read(DownstreamConnection *dconn) {
+  auto downstream = dconn->get_downstream();
+
+  if (downstream->get_response_state() == DownstreamState::MSG_RESET) {
+    // The downstream stream was reset (canceled). In this case,
+    // RST_STREAM to the upstream and delete downstream connection
+    // here. Deleting downstream will be taken place at
+    // on_stream_close_callback.
+    rst_stream(downstream,
+               infer_upstream_rst_stream_error_code(
+                   downstream->get_response_rst_stream_error_code()));
+    downstream->pop_downstream_connection();
+    // dconn was deleted
+    dconn = nullptr;
+  } else if (downstream->get_response_state() ==
+             DownstreamState::MSG_BAD_HEADER) {
+    if (error_reply(downstream, 502) != 0) {
+      return -1;
+    }
+    downstream->pop_downstream_connection();
+    // dconn was deleted
+    dconn = nullptr;
+  } else {
+    auto rv = downstream->on_read();
+    if (rv == SHRPX_ERR_EOF) {
+      if (downstream->get_request_header_sent()) {
+        return downstream_eof(dconn);
+      }
+      return SHRPX_ERR_RETRY;
+    }
+    if (rv == SHRPX_ERR_DCONN_CANCELED) {
+      downstream->pop_downstream_connection();
+      handler_->signal_write();
+      return 0;
+    }
+    if (rv != 0) {
+      if (rv != SHRPX_ERR_NETWORK) {
+        if (LOG_ENABLED(INFO)) {
+          DCLOG(INFO, dconn) << "HTTP parser failure";
+        }
+      }
+      return downstream_error(dconn, Downstream::EVENT_ERROR);
+    }
+
+    if (downstream->can_detach_downstream_connection()) {
+      // Keep-alive
+      downstream->detach_downstream_connection();
+    }
+  }
+
+  handler_->signal_write();
+
+  // At this point, downstream may be deleted.
+
+  return 0;
+}
+
+int Http2Upstream::downstream_write(DownstreamConnection *dconn) {
+  int rv;
+  rv = dconn->on_write();
+  if (rv == SHRPX_ERR_NETWORK) {
+    return downstream_error(dconn, Downstream::EVENT_ERROR);
+  }
+  if (rv != 0) {
+    return rv;
+  }
+  return 0;
+}
+
+int Http2Upstream::downstream_eof(DownstreamConnection *dconn) {
+  auto downstream = dconn->get_downstream();
+
+  if (LOG_ENABLED(INFO)) {
+    DCLOG(INFO, dconn) << "EOF. stream_id=" << downstream->get_stream_id();
+  }
+
+  // Delete downstream connection. If we don't delete it here, it will
+  // be pooled in on_stream_close_callback.
+  downstream->pop_downstream_connection();
+  // dconn was deleted
+  dconn = nullptr;
+  // downstream will be deleted in on_stream_close_callback.
+  if (downstream->get_response_state() == DownstreamState::HEADER_COMPLETE) {
+    // Server may indicate the end of the request by EOF
+    if (LOG_ENABLED(INFO)) {
+      ULOG(INFO, this) << "Downstream body was ended by EOF";
+    }
+    downstream->set_response_state(DownstreamState::MSG_COMPLETE);
+
+    // For tunneled connection, MSG_COMPLETE signals
+    // downstream_data_read_callback to send RST_STREAM after pending
+    // response body is sent. This is needed to ensure that RST_STREAM
+    // is sent after all pending data are sent.
+    on_downstream_body_complete(downstream);
+  } else if (downstream->get_response_state() !=
+             DownstreamState::MSG_COMPLETE) {
+    // If stream was not closed, then we set MSG_COMPLETE and let
+    // on_stream_close_callback delete downstream.
+    if (error_reply(downstream, 502) != 0) {
+      return -1;
+    }
+  }
+  handler_->signal_write();
+  // At this point, downstream may be deleted.
+  return 0;
+}
+
+int Http2Upstream::downstream_error(DownstreamConnection *dconn, int events) {
+  auto downstream = dconn->get_downstream();
+
+  if (LOG_ENABLED(INFO)) {
+    if (events & Downstream::EVENT_ERROR) {
+      DCLOG(INFO, dconn) << "Downstream network/general error";
+    } else {
+      DCLOG(INFO, dconn) << "Timeout";
+    }
+    if (downstream->get_upgraded()) {
+      DCLOG(INFO, dconn) << "Note: this is tunnel connection";
+    }
+  }
+
+  // Delete downstream connection. If we don't delete it here, it will
+  // be pooled in on_stream_close_callback.
+  downstream->pop_downstream_connection();
+  // dconn was deleted
+  dconn = nullptr;
+
+  if (downstream->get_response_state() == DownstreamState::MSG_COMPLETE) {
+    // For SSL tunneling, we issue RST_STREAM. For other types of
+    // stream, we don't have to do anything since response was
+    // complete.
+    if (downstream->get_upgraded()) {
+      rst_stream(downstream, NGHTTP2_NO_ERROR);
+    }
+  } else {
+    if (downstream->get_response_state() == DownstreamState::HEADER_COMPLETE) {
+      if (downstream->get_upgraded()) {
+        on_downstream_body_complete(downstream);
+      } else {
+        rst_stream(downstream, NGHTTP2_INTERNAL_ERROR);
+      }
+    } else {
+      unsigned int status;
+      if (events & Downstream::EVENT_TIMEOUT) {
+        if (downstream->get_request_header_sent()) {
+          status = 504;
+        } else {
+          status = 408;
+        }
+      } else {
+        status = 502;
+      }
+      if (error_reply(downstream, status) != 0) {
+        return -1;
+      }
+    }
+    downstream->set_response_state(DownstreamState::MSG_COMPLETE);
+  }
+  handler_->signal_write();
+  // At this point, downstream may be deleted.
+  return 0;
+}
+
+int Http2Upstream::rst_stream(Downstream *downstream, uint32_t error_code) {
+  if (LOG_ENABLED(INFO)) {
+    ULOG(INFO, this) << "RST_STREAM stream_id=" << downstream->get_stream_id()
+                     << " with error_code=" << error_code;
+  }
+  int rv;
+  rv = nghttp2_submit_rst_stream(session_, NGHTTP2_FLAG_NONE,
+                                 downstream->get_stream_id(), error_code);
+  if (rv < NGHTTP2_ERR_FATAL) {
+    ULOG(FATAL, this) << "nghttp2_submit_rst_stream() failed: "
+                      << nghttp2_strerror(rv);
+    return -1;
+  }
+  return 0;
+}
+
+int Http2Upstream::terminate_session(uint32_t error_code) {
+  int rv;
+  rv = nghttp2_session_terminate_session(session_, error_code);
+  if (rv != 0) {
+    return -1;
+  }
+  return 0;
+}
+
+namespace {
+ssize_t downstream_data_read_callback(nghttp2_session *session,
+                                      int32_t stream_id, uint8_t *buf,
+                                      size_t length, uint32_t *data_flags,
+                                      nghttp2_data_source *source,
+                                      void *user_data) {
+  int rv;
+  auto downstream = static_cast<Downstream *>(source->ptr);
+  auto body = downstream->get_response_buf();
+  assert(body);
+  auto upstream = static_cast<Http2Upstream *>(user_data);
+
+  const auto &resp = downstream->response();
+
+  auto nread = std::min(body->rleft(), length);
+
+  auto max_buffer_size = upstream->get_max_buffer_size();
+
+  auto buffer = upstream->get_response_buf();
+
+  if (max_buffer_size <
+      std::min(nread, static_cast<size_t>(256)) + 9 + buffer->rleft()) {
+    if (LOG_ENABLED(INFO)) {
+      ULOG(INFO, upstream) << "Buffer is almost full.  Skip write DATA";
+    }
+    return NGHTTP2_ERR_PAUSE;
+  }
+
+  nread = std::min(nread, max_buffer_size - 9 - buffer->rleft());
+
+  auto body_empty = body->rleft() == nread;
+
+  *data_flags |= NGHTTP2_DATA_FLAG_NO_COPY;
+
+  if (body_empty &&
+      downstream->get_response_state() == DownstreamState::MSG_COMPLETE) {
+
+    *data_flags |= NGHTTP2_DATA_FLAG_EOF;
+
+    if (!downstream->get_upgraded()) {
+      const auto &trailers = resp.fs.trailers();
+      if (!trailers.empty()) {
+        std::vector<nghttp2_nv> nva;
+        nva.reserve(trailers.size());
+        http2::copy_headers_to_nva_nocopy(nva, trailers, http2::HDOP_STRIP_ALL);
+        if (!nva.empty()) {
+          rv = nghttp2_submit_trailer(session, stream_id, nva.data(),
+                                      nva.size());
+          if (rv != 0) {
+            if (nghttp2_is_fatal(rv)) {
+              return NGHTTP2_ERR_CALLBACK_FAILURE;
+            }
+          } else {
+            *data_flags |= NGHTTP2_DATA_FLAG_NO_END_STREAM;
+          }
+        }
+      }
+    }
+  }
+
+  if (nread == 0 && ((*data_flags) & NGHTTP2_DATA_FLAG_EOF) == 0) {
+    downstream->disable_upstream_wtimer();
+    return NGHTTP2_ERR_DEFERRED;
+  }
+
+  return nread;
+}
+} // namespace
+
+int Http2Upstream::send_reply(Downstream *downstream, const uint8_t *body,
+                              size_t bodylen) {
+  int rv;
+
+  nghttp2_data_provider data_prd, *data_prd_ptr = nullptr;
+
+  if (bodylen) {
+    data_prd.source.ptr = downstream;
+    data_prd.read_callback = downstream_data_read_callback;
+    data_prd_ptr = &data_prd;
+  }
+
+  const auto &resp = downstream->response();
+  auto config = get_config();
+  auto &httpconf = config->http;
+
+  auto &balloc = downstream->get_block_allocator();
+
+  const auto &headers = resp.fs.headers();
+  auto nva = std::vector<nghttp2_nv>();
+  // 2 for :status and server
+  nva.reserve(2 + headers.size() + httpconf.add_response_headers.size());
+
+  auto response_status = http2::stringify_status(balloc, resp.http_status);
+
+  nva.push_back(http2::make_nv_ls_nocopy(":status", response_status));
+
+  for (auto &kv : headers) {
+    if (kv.name.empty() || kv.name[0] == ':') {
+      continue;
+    }
+    switch (kv.token) {
+    case http2::HD_CONNECTION:
+    case http2::HD_KEEP_ALIVE:
+    case http2::HD_PROXY_CONNECTION:
+    case http2::HD_TE:
+    case http2::HD_TRANSFER_ENCODING:
+    case http2::HD_UPGRADE:
+      continue;
+    }
+    nva.push_back(http2::make_nv_nocopy(kv.name, kv.value, kv.no_index));
+  }
+
+  if (!resp.fs.header(http2::HD_SERVER)) {
+    nva.push_back(http2::make_nv_ls_nocopy("server", config->http.server_name));
+  }
+
+  for (auto &p : httpconf.add_response_headers) {
+    nva.push_back(http2::make_nv_nocopy(p.name, p.value));
+  }
+
+  rv = nghttp2_submit_response(session_, downstream->get_stream_id(),
+                               nva.data(), nva.size(), data_prd_ptr);
+  if (nghttp2_is_fatal(rv)) {
+    ULOG(FATAL, this) << "nghttp2_submit_response() failed: "
+                      << nghttp2_strerror(rv);
+    return -1;
+  }
+
+  auto buf = downstream->get_response_buf();
+
+  buf->append(body, bodylen);
+
+  downstream->set_response_state(DownstreamState::MSG_COMPLETE);
+
+  if (data_prd_ptr) {
+    downstream->reset_upstream_wtimer();
+  }
+
+  return 0;
+}
+
+int Http2Upstream::error_reply(Downstream *downstream,
+                               unsigned int status_code) {
+  int rv;
+  auto &resp = downstream->response();
+
+  auto &balloc = downstream->get_block_allocator();
+
+  auto html = http::create_error_html(balloc, status_code);
+  resp.http_status = status_code;
+  auto body = downstream->get_response_buf();
+  body->append(html);
+  downstream->set_response_state(DownstreamState::MSG_COMPLETE);
+
+  nghttp2_data_provider data_prd;
+  data_prd.source.ptr = downstream;
+  data_prd.read_callback = downstream_data_read_callback;
+
+  auto lgconf = log_config();
+  lgconf->update_tstamp(std::chrono::system_clock::now());
+
+  auto response_status = http2::stringify_status(balloc, status_code);
+  auto content_length = util::make_string_ref_uint(balloc, html.size());
+  auto date = make_string_ref(balloc, lgconf->tstamp->time_http);
+
+  auto nva = std::array<nghttp2_nv, 5>{
+      {http2::make_nv_ls_nocopy(":status", response_status),
+       http2::make_nv_ll("content-type", "text/html; charset=UTF-8"),
+       http2::make_nv_ls_nocopy("server", get_config()->http.server_name),
+       http2::make_nv_ls_nocopy("content-length", content_length),
+       http2::make_nv_ls_nocopy("date", date)}};
+
+  rv = nghttp2_submit_response(session_, downstream->get_stream_id(),
+                               nva.data(), nva.size(), &data_prd);
+  if (rv < NGHTTP2_ERR_FATAL) {
+    ULOG(FATAL, this) << "nghttp2_submit_response() failed: "
+                      << nghttp2_strerror(rv);
+    return -1;
+  }
+
+  downstream->reset_upstream_wtimer();
+
+  return 0;
+}
+
+void Http2Upstream::add_pending_downstream(
+    std::unique_ptr<Downstream> downstream) {
+  downstream_queue_.add_pending(std::move(downstream));
+}
+
+void Http2Upstream::remove_downstream(Downstream *downstream) {
+  if (downstream->accesslog_ready()) {
+    handler_->write_accesslog(downstream);
+  }
+
+  nghttp2_session_set_stream_user_data(session_, downstream->get_stream_id(),
+                                       nullptr);
+
+  auto next_downstream = downstream_queue_.remove_and_get_blocked(downstream);
+
+  if (next_downstream) {
+    initiate_downstream(next_downstream);
+  }
+
+  if (downstream_queue_.get_downstreams() == nullptr) {
+    // There is no downstream at the moment.  Start idle timer now.
+    handler_->repeat_read_timer();
+  }
+}
+
+// WARNING: Never call directly or indirectly nghttp2_session_send or
+// nghttp2_session_recv. These calls may delete downstream.
+int Http2Upstream::on_downstream_header_complete(Downstream *downstream) {
+  int rv;
+
+  const auto &req = downstream->request();
+  auto &resp = downstream->response();
+
+  auto &balloc = downstream->get_block_allocator();
+
+  if (LOG_ENABLED(INFO)) {
+    if (downstream->get_non_final_response()) {
+      DLOG(INFO, downstream) << "HTTP non-final response header";
+    } else {
+      DLOG(INFO, downstream) << "HTTP response header completed";
+    }
+  }
+
+  auto config = get_config();
+  auto &httpconf = config->http;
+
+  if (!config->http2_proxy && !httpconf.no_location_rewrite) {
+    downstream->rewrite_location_response_header(req.scheme);
+  }
+
+#ifdef HAVE_MRUBY
+  if (!downstream->get_non_final_response()) {
+    auto dconn = downstream->get_downstream_connection();
+    const auto &group = dconn->get_downstream_addr_group();
+    if (group) {
+      const auto &dmruby_ctx = group->shared_addr->mruby_ctx;
+
+      if (dmruby_ctx->run_on_response_proc(downstream) != 0) {
+        if (error_reply(downstream, 500) != 0) {
+          return -1;
+        }
+        // Returning -1 will signal deletion of dconn.
+        return -1;
+      }
+
+      if (downstream->get_response_state() == DownstreamState::MSG_COMPLETE) {
+        return -1;
+      }
+    }
+
+    auto worker = handler_->get_worker();
+    auto mruby_ctx = worker->get_mruby_context();
+
+    if (mruby_ctx->run_on_response_proc(downstream) != 0) {
+      if (error_reply(downstream, 500) != 0) {
+        return -1;
+      }
+      // Returning -1 will signal deletion of dconn.
+      return -1;
+    }
+
+    if (downstream->get_response_state() == DownstreamState::MSG_COMPLETE) {
+      return -1;
+    }
+  }
+#endif // HAVE_MRUBY
+
+  auto &http2conf = config->http2;
+
+  // We need some conditions that must be fulfilled to initiate server
+  // push.
+  //
+  // * Server push is disabled for http2 proxy or client proxy, since
+  //   incoming headers are mixed origins.  We don't know how to
+  //   reliably determine the authority yet.
+  //
+  // * We need non-final response or 200 response code for associated
+  //   resource.  This is too restrictive, we will review this later.
+  //
+  // * We requires GET or POST for associated resource.  Probably we
+  //   don't want to push for HEAD request.  Not sure other methods
+  //   are also eligible for push.
+  if (!http2conf.no_server_push &&
+      nghttp2_session_get_remote_settings(session_,
+                                          NGHTTP2_SETTINGS_ENABLE_PUSH) == 1 &&
+      !config->http2_proxy && (downstream->get_stream_id() % 2) &&
+      resp.fs.header(http2::HD_LINK) &&
+      (downstream->get_non_final_response() || resp.http_status == 200) &&
+      (req.method == HTTP_GET || req.method == HTTP_POST)) {
+
+    if (prepare_push_promise(downstream) != 0) {
+      // Continue to send response even if push was failed.
+    }
+  }
+
+  auto nva = std::vector<nghttp2_nv>();
+  // 6 means :status and possible server, via, x-http2-push, alt-svc,
+  // and set-cookie (for affinity cookie) header field.
+  nva.reserve(resp.fs.headers().size() + 6 +
+              httpconf.add_response_headers.size());
+
+  if (downstream->get_non_final_response()) {
+    auto response_status = http2::stringify_status(balloc, resp.http_status);
+
+    nva.push_back(http2::make_nv_ls_nocopy(":status", response_status));
+
+    http2::copy_headers_to_nva_nocopy(nva, resp.fs.headers(),
+                                      http2::HDOP_STRIP_ALL);
+
+    if (LOG_ENABLED(INFO)) {
+      log_response_headers(downstream, nva);
+    }
+
+    rv = nghttp2_submit_headers(session_, NGHTTP2_FLAG_NONE,
+                                downstream->get_stream_id(), nullptr,
+                                nva.data(), nva.size(), nullptr);
+
+    resp.fs.clear_headers();
+
+    if (rv != 0) {
+      ULOG(FATAL, this) << "nghttp2_submit_headers() failed";
+      return -1;
+    }
+
+    return 0;
+  }
+
+  auto striphd_flags = http2::HDOP_STRIP_ALL & ~http2::HDOP_STRIP_VIA;
+  StringRef response_status;
+
+  if (req.connect_proto == ConnectProto::WEBSOCKET && resp.http_status == 101) {
+    response_status = http2::stringify_status(balloc, 200);
+    striphd_flags |= http2::HDOP_STRIP_SEC_WEBSOCKET_ACCEPT;
+  } else {
+    response_status = http2::stringify_status(balloc, resp.http_status);
+  }
+
+  nva.push_back(http2::make_nv_ls_nocopy(":status", response_status));
+
+  http2::copy_headers_to_nva_nocopy(nva, resp.fs.headers(), striphd_flags);
+
+  if (!config->http2_proxy && !httpconf.no_server_rewrite) {
+    nva.push_back(http2::make_nv_ls_nocopy("server", httpconf.server_name));
+  } else {
+    auto server = resp.fs.header(http2::HD_SERVER);
+    if (server) {
+      nva.push_back(http2::make_nv_ls_nocopy("server", (*server).value));
+    }
+  }
+
+  if (!req.regular_connect_method() || !downstream->get_upgraded()) {
+    auto affinity_cookie = downstream->get_affinity_cookie_to_send();
+    if (affinity_cookie) {
+      auto dconn = downstream->get_downstream_connection();
+      assert(dconn);
+      auto &group = dconn->get_downstream_addr_group();
+      auto &shared_addr = group->shared_addr;
+      auto &cookieconf = shared_addr->affinity.cookie;
+      auto secure =
+          http::require_cookie_secure_attribute(cookieconf.secure, req.scheme);
+      auto cookie_str = http::create_affinity_cookie(
+          balloc, cookieconf.name, affinity_cookie, cookieconf.path, secure);
+      nva.push_back(http2::make_nv_ls_nocopy("set-cookie", cookie_str));
+    }
+  }
+
+  if (!resp.fs.header(http2::HD_ALT_SVC)) {
+    // We won't change or alter alt-svc from backend for now
+    if (!httpconf.http2_altsvc_header_value.empty()) {
+      nva.push_back(http2::make_nv_ls_nocopy(
+          "alt-svc", httpconf.http2_altsvc_header_value));
+    }
+  }
+
+  auto via = resp.fs.header(http2::HD_VIA);
+  if (httpconf.no_via) {
+    if (via) {
+      nva.push_back(http2::make_nv_ls_nocopy("via", (*via).value));
+    }
+  } else {
+    // we don't create more than 16 bytes in
+    // http::create_via_header_value.
+    size_t len = 16;
+    if (via) {
+      len += via->value.size() + 2;
+    }
+
+    auto iov = make_byte_ref(balloc, len + 1);
+    auto p = iov.base;
+    if (via) {
+      p = std::copy(std::begin(via->value), std::end(via->value), p);
+      p = util::copy_lit(p, ", ");
+    }
+    p = http::create_via_header_value(p, resp.http_major, resp.http_minor);
+    *p = '\0';
+
+    nva.push_back(http2::make_nv_ls_nocopy("via", StringRef{iov.base, p}));
+  }
+
+  for (auto &p : httpconf.add_response_headers) {
+    nva.push_back(http2::make_nv_nocopy(p.name, p.value));
+  }
+
+  if (downstream->get_stream_id() % 2 == 0) {
+    // This header field is basically for human on client side to
+    // figure out that the resource is pushed.
+    nva.push_back(http2::make_nv_ll("x-http2-push", "1"));
+  }
+
+  if (LOG_ENABLED(INFO)) {
+    log_response_headers(downstream, nva);
+  }
+
+  if (http2conf.upstream.debug.dump.response_header) {
+    http2::dump_nv(http2conf.upstream.debug.dump.response_header, nva.data(),
+                   nva.size());
+  }
+
+  nghttp2_data_provider data_prd;
+  data_prd.source.ptr = downstream;
+  data_prd.read_callback = downstream_data_read_callback;
+
+  nghttp2_data_provider *data_prdptr;
+
+  if (downstream->expect_response_body() ||
+      downstream->expect_response_trailer()) {
+    data_prdptr = &data_prd;
+  } else {
+    data_prdptr = nullptr;
+  }
+
+  rv = nghttp2_submit_response(session_, downstream->get_stream_id(),
+                               nva.data(), nva.size(), data_prdptr);
+  if (rv != 0) {
+    ULOG(FATAL, this) << "nghttp2_submit_response() failed";
+    return -1;
+  }
+
+  if (data_prdptr) {
+    downstream->reset_upstream_wtimer();
+  }
+
+  return 0;
+}
+
+// WARNING: Never call directly or indirectly nghttp2_session_send or
+// nghttp2_session_recv. These calls may delete downstream.
+int Http2Upstream::on_downstream_body(Downstream *downstream,
+                                      const uint8_t *data, size_t len,
+                                      bool flush) {
+  auto body = downstream->get_response_buf();
+  body->append(data, len);
+
+  if (flush) {
+    nghttp2_session_resume_data(session_, downstream->get_stream_id());
+
+    downstream->ensure_upstream_wtimer();
+  }
+
+  return 0;
+}
+
+// WARNING: Never call directly or indirectly nghttp2_session_send or
+// nghttp2_session_recv. These calls may delete downstream.
+int Http2Upstream::on_downstream_body_complete(Downstream *downstream) {
+  if (LOG_ENABLED(INFO)) {
+    DLOG(INFO, downstream) << "HTTP response completed";
+  }
+
+  auto &resp = downstream->response();
+
+  if (!downstream->validate_response_recv_body_length()) {
+    rst_stream(downstream, NGHTTP2_PROTOCOL_ERROR);
+    resp.connection_close = true;
+    return 0;
+  }
+
+  nghttp2_session_resume_data(session_, downstream->get_stream_id());
+  downstream->ensure_upstream_wtimer();
+
+  return 0;
+}
+
+bool Http2Upstream::get_flow_control() const { return flow_control_; }
+
+void Http2Upstream::pause_read(IOCtrlReason reason) {}
+
+int Http2Upstream::resume_read(IOCtrlReason reason, Downstream *downstream,
+                               size_t consumed) {
+  if (get_flow_control()) {
+    if (consume(downstream->get_stream_id(), consumed) != 0) {
+      return -1;
+    }
+
+    auto &req = downstream->request();
+
+    req.consume(consumed);
+  }
+
+  handler_->signal_write();
+  return 0;
+}
+
+int Http2Upstream::on_downstream_abort_request(Downstream *downstream,
+                                               unsigned int status_code) {
+  int rv;
+
+  rv = error_reply(downstream, status_code);
+
+  if (rv != 0) {
+    return -1;
+  }
+
+  handler_->signal_write();
+  return 0;
+}
+
+int Http2Upstream::on_downstream_abort_request_with_https_redirect(
+    Downstream *downstream) {
+  int rv;
+
+  rv = redirect_to_https(downstream);
+  if (rv != 0) {
+    return -1;
+  }
+
+  handler_->signal_write();
+  return 0;
+}
+
+int Http2Upstream::redirect_to_https(Downstream *downstream) {
+  auto &req = downstream->request();
+  if (req.regular_connect_method() || req.scheme != "http") {
+    return error_reply(downstream, 400);
+  }
+
+  auto authority = util::extract_host(req.authority);
+  if (authority.empty()) {
+    return error_reply(downstream, 400);
+  }
+
+  auto &balloc = downstream->get_block_allocator();
+  auto config = get_config();
+  auto &httpconf = config->http;
+
+  StringRef loc;
+  if (httpconf.redirect_https_port == StringRef::from_lit("443")) {
+    loc = concat_string_ref(balloc, StringRef::from_lit("https://"), authority,
+                            req.path);
+  } else {
+    loc = concat_string_ref(balloc, StringRef::from_lit("https://"), authority,
+                            StringRef::from_lit(":"),
+                            httpconf.redirect_https_port, req.path);
+  }
+
+  auto &resp = downstream->response();
+  resp.http_status = 308;
+  resp.fs.add_header_token(StringRef::from_lit("location"), loc, false,
+                           http2::HD_LOCATION);
+
+  return send_reply(downstream, nullptr, 0);
+}
+
+int Http2Upstream::consume(int32_t stream_id, size_t len) {
+  int rv;
+
+  auto faddr = handler_->get_upstream_addr();
+
+  if (faddr->alt_mode != UpstreamAltMode::NONE) {
+    return 0;
+  }
+
+  rv = nghttp2_session_consume(session_, stream_id, len);
+
+  if (rv != 0) {
+    ULOG(WARN, this) << "nghttp2_session_consume() returned error: "
+                     << nghttp2_strerror(rv);
+    return -1;
+  }
+
+  return 0;
+}
+
+void Http2Upstream::log_response_headers(
+    Downstream *downstream, const std::vector<nghttp2_nv> &nva) const {
+  std::stringstream ss;
+  for (auto &nv : nva) {
+    ss << TTY_HTTP_HD << StringRef{nv.name, nv.namelen} << TTY_RST << ": "
+       << StringRef{nv.value, nv.valuelen} << "\n";
+  }
+  ULOG(INFO, this) << "HTTP response headers. stream_id="
+                   << downstream->get_stream_id() << "\n"
+                   << ss.str();
+}
+
+int Http2Upstream::on_timeout(Downstream *downstream) {
+  if (LOG_ENABLED(INFO)) {
+    ULOG(INFO, this) << "Stream timeout stream_id="
+                     << downstream->get_stream_id();
+  }
+
+  rst_stream(downstream, NGHTTP2_INTERNAL_ERROR);
+  handler_->signal_write();
+
+  return 0;
+}
+
+void Http2Upstream::on_handler_delete() {
+  for (auto d = downstream_queue_.get_downstreams(); d; d = d->dlnext) {
+    if (d->get_dispatch_state() == DispatchState::ACTIVE &&
+        d->accesslog_ready()) {
+      handler_->write_accesslog(d);
+    }
+  }
+}
+
+int Http2Upstream::on_downstream_reset(Downstream *downstream, bool no_retry) {
+  int rv;
+
+  if (downstream->get_dispatch_state() != DispatchState::ACTIVE) {
+    // This is error condition when we failed push_request_headers()
+    // in initiate_downstream().  Otherwise, we have
+    // DispatchState::ACTIVE state, or we did not set
+    // DownstreamConnection.
+    downstream->pop_downstream_connection();
+    handler_->signal_write();
+
+    return 0;
+  }
+
+  if (!downstream->request_submission_ready()) {
+    if (downstream->get_response_state() == DownstreamState::MSG_COMPLETE) {
+      // We have got all response body already.  Send it off.
+      downstream->pop_downstream_connection();
+      return 0;
+    }
+    // pushed stream is handled here
+    rst_stream(downstream, NGHTTP2_INTERNAL_ERROR);
+    downstream->pop_downstream_connection();
+
+    handler_->signal_write();
+
+    return 0;
+  }
+
+  downstream->pop_downstream_connection();
+
+  downstream->add_retry();
+
+  std::unique_ptr<DownstreamConnection> dconn;
+
+  rv = 0;
+
+  if (no_retry || downstream->no_more_retry()) {
+    goto fail;
+  }
+
+  // downstream connection is clean; we can retry with new
+  // downstream connection.
+
+  for (;;) {
+    auto dconn = handler_->get_downstream_connection(rv, downstream);
+    if (!dconn) {
+      goto fail;
+    }
+
+    rv = downstream->attach_downstream_connection(std::move(dconn));
+    if (rv == 0) {
+      break;
+    }
+  }
+
+  rv = downstream->push_request_headers();
+  if (rv != 0) {
+    goto fail;
+  }
+
+  return 0;
+
+fail:
+  if (rv == SHRPX_ERR_TLS_REQUIRED) {
+    rv = on_downstream_abort_request_with_https_redirect(downstream);
+  } else {
+    rv = on_downstream_abort_request(downstream, 502);
+  }
+  if (rv != 0) {
+    rst_stream(downstream, NGHTTP2_INTERNAL_ERROR);
+  }
+  downstream->pop_downstream_connection();
+
+  handler_->signal_write();
+
+  return 0;
+}
+
+int Http2Upstream::prepare_push_promise(Downstream *downstream) {
+  int rv;
+
+  const auto &req = downstream->request();
+  auto &resp = downstream->response();
+
+  auto base = http2::get_pure_path_component(req.path);
+  if (base.empty()) {
+    return 0;
+  }
+
+  auto &balloc = downstream->get_block_allocator();
+
+  for (auto &kv : resp.fs.headers()) {
+    if (kv.token != http2::HD_LINK) {
+      continue;
+    }
+    for (auto &link : http2::parse_link_header(kv.value)) {
+      StringRef scheme, authority, path;
+
+      rv = http2::construct_push_component(balloc, scheme, authority, path,
+                                           base, link.uri);
+      if (rv != 0) {
+        continue;
+      }
+
+      if (scheme.empty()) {
+        scheme = req.scheme;
+      }
+
+      if (authority.empty()) {
+        authority = req.authority;
+      }
+
+      if (resp.is_resource_pushed(scheme, authority, path)) {
+        continue;
+      }
+
+      rv = submit_push_promise(scheme, authority, path, downstream);
+      if (rv != 0) {
+        return -1;
+      }
+
+      resp.resource_pushed(scheme, authority, path);
+    }
+  }
+  return 0;
+}
+
+int Http2Upstream::submit_push_promise(const StringRef &scheme,
+                                       const StringRef &authority,
+                                       const StringRef &path,
+                                       Downstream *downstream) {
+  const auto &req = downstream->request();
+
+  std::vector<nghttp2_nv> nva;
+  // 4 for :method, :scheme, :path and :authority
+  nva.reserve(4 + req.fs.headers().size());
+
+  // just use "GET" for now
+  nva.push_back(http2::make_nv_ll(":method", "GET"));
+  nva.push_back(http2::make_nv_ls_nocopy(":scheme", scheme));
+  nva.push_back(http2::make_nv_ls_nocopy(":path", path));
+  nva.push_back(http2::make_nv_ls_nocopy(":authority", authority));
+
+  for (auto &kv : req.fs.headers()) {
+    switch (kv.token) {
+    // TODO generate referer
+    case http2::HD__AUTHORITY:
+    case http2::HD__SCHEME:
+    case http2::HD__METHOD:
+    case http2::HD__PATH:
+      continue;
+    case http2::HD_ACCEPT_ENCODING:
+    case http2::HD_ACCEPT_LANGUAGE:
+    case http2::HD_CACHE_CONTROL:
+    case http2::HD_HOST:
+    case http2::HD_USER_AGENT:
+      nva.push_back(http2::make_nv_nocopy(kv.name, kv.value, kv.no_index));
+      break;
+    }
+  }
+
+  auto promised_stream_id = nghttp2_submit_push_promise(
+      session_, NGHTTP2_FLAG_NONE, downstream->get_stream_id(), nva.data(),
+      nva.size(), nullptr);
+
+  if (promised_stream_id < 0) {
+    if (LOG_ENABLED(INFO)) {
+      ULOG(INFO, this) << "nghttp2_submit_push_promise() failed: "
+                       << nghttp2_strerror(promised_stream_id);
+    }
+    if (nghttp2_is_fatal(promised_stream_id)) {
+      return -1;
+    }
+    return 0;
+  }
+
+  if (LOG_ENABLED(INFO)) {
+    std::stringstream ss;
+    for (auto &nv : nva) {
+      ss << TTY_HTTP_HD << StringRef{nv.name, nv.namelen} << TTY_RST << ": "
+         << StringRef{nv.value, nv.valuelen} << "\n";
+    }
+    ULOG(INFO, this) << "HTTP push request headers. promised_stream_id="
+                     << promised_stream_id << "\n"
+                     << ss.str();
+  }
+
+  return 0;
+}
+
+bool Http2Upstream::push_enabled() const {
+  auto config = get_config();
+  return !(config->http2.no_server_push ||
+           nghttp2_session_get_remote_settings(
+               session_, NGHTTP2_SETTINGS_ENABLE_PUSH) == 0 ||
+           config->http2_proxy);
+}
+
+int Http2Upstream::initiate_push(Downstream *downstream, const StringRef &uri) {
+  int rv;
+
+  if (uri.empty() || !push_enabled() ||
+      (downstream->get_stream_id() % 2) == 0) {
+    return 0;
+  }
+
+  const auto &req = downstream->request();
+
+  auto base = http2::get_pure_path_component(req.path);
+  if (base.empty()) {
+    return -1;
+  }
+
+  auto &balloc = downstream->get_block_allocator();
+
+  StringRef scheme, authority, path;
+
+  rv = http2::construct_push_component(balloc, scheme, authority, path, base,
+                                       uri);
+  if (rv != 0) {
+    return -1;
+  }
+
+  if (scheme.empty()) {
+    scheme = req.scheme;
+  }
+
+  if (authority.empty()) {
+    authority = req.authority;
+  }
+
+  auto &resp = downstream->response();
+
+  if (resp.is_resource_pushed(scheme, authority, path)) {
+    return 0;
+  }
+
+  rv = submit_push_promise(scheme, authority, path, downstream);
+
+  if (rv != 0) {
+    return -1;
+  }
+
+  resp.resource_pushed(scheme, authority, path);
+
+  return 0;
+}
+
+int Http2Upstream::response_riovec(struct iovec *iov, int iovcnt) const {
+  if (iovcnt == 0 || wb_.rleft() == 0) {
+    return 0;
+  }
+
+  return wb_.riovec(iov, iovcnt);
+}
+
+void Http2Upstream::response_drain(size_t n) { wb_.drain(n); }
+
+bool Http2Upstream::response_empty() const { return wb_.rleft() == 0; }
+
+DefaultMemchunks *Http2Upstream::get_response_buf() { return &wb_; }
+
+Downstream *
+Http2Upstream::on_downstream_push_promise(Downstream *downstream,
+                                          int32_t promised_stream_id) {
+  // promised_stream_id is for backend HTTP/2 session, not for
+  // frontend.
+  auto promised_downstream =
+      std::make_unique<Downstream>(this, handler_->get_mcpool(), 0);
+  auto &promised_req = promised_downstream->request();
+
+  promised_downstream->set_downstream_stream_id(promised_stream_id);
+  // Set associated stream in frontend
+  promised_downstream->set_assoc_stream_id(downstream->get_stream_id());
+
+  promised_downstream->disable_upstream_rtimer();
+
+  promised_req.http_major = 2;
+  promised_req.http_minor = 0;
+
+  promised_req.fs.content_length = 0;
+  promised_req.http2_expect_body = false;
+
+  auto ptr = promised_downstream.get();
+  add_pending_downstream(std::move(promised_downstream));
+  downstream_queue_.mark_active(ptr);
+
+  return ptr;
+}
+
+int Http2Upstream::on_downstream_push_promise_complete(
+    Downstream *downstream, Downstream *promised_downstream) {
+  std::vector<nghttp2_nv> nva;
+
+  const auto &promised_req = promised_downstream->request();
+  const auto &headers = promised_req.fs.headers();
+
+  nva.reserve(headers.size());
+
+  for (auto &kv : headers) {
+    nva.push_back(http2::make_nv(kv.name, kv.value, kv.no_index));
+  }
+
+  auto promised_stream_id = nghttp2_submit_push_promise(
+      session_, NGHTTP2_FLAG_NONE, downstream->get_stream_id(), nva.data(),
+      nva.size(), promised_downstream);
+  if (promised_stream_id < 0) {
+    return -1;
+  }
+
+  promised_downstream->set_stream_id(promised_stream_id);
+
+  return 0;
+}
+
+void Http2Upstream::cancel_premature_downstream(
+    Downstream *promised_downstream) {
+  if (LOG_ENABLED(INFO)) {
+    ULOG(INFO, this) << "Remove premature promised stream "
+                     << promised_downstream;
+  }
+  downstream_queue_.remove_and_get_blocked(promised_downstream, false);
+}
+
+size_t Http2Upstream::get_max_buffer_size() const { return max_buffer_size_; }
+
+} // namespace shrpx