nghttp2/src/HttpServer.cc

/*
 * nghttp2 - HTTP/2 C Library
 *
 * Copyright (c) 2013 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 "HttpServer.h"

#include <sys/stat.h>
#include <sys/socket.h>
#include <netdb.h>
#include <unistd.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <netinet/tcp.h>

#include <cassert>
#include <set>
#include <iostream>
#include <thread>
#include <mutex>
#include <deque>

#include <openssl/err.h>

#include <zlib.h>

#include "app_helper.h"
#include "http2.h"
#include "util.h"
#include "ssl.h"

#ifndef O_BINARY
#define O_BINARY (0)
#endif // O_BINARY

namespace nghttp2 {

namespace {
const std::string STATUS_200 = "200";
const std::string STATUS_301 = "301";
const std::string STATUS_304 = "304";
const std::string STATUS_400 = "400";
const std::string STATUS_404 = "404";
const std::string DEFAULT_HTML = "index.html";
const std::string NGHTTPD_SERVER = "nghttpd nghttp2/" NGHTTP2_VERSION;
} // namespace

namespace {
int make_socket_nonblocking(int fd) {
  int flags;
  int rv;
  while ((flags = fcntl(fd, F_GETFL, 0)) == -1 && errno == EINTR)
    ;
  while ((rv = fcntl(fd, F_SETFL, flags | O_NONBLOCK)) == -1 && errno == EINTR)
    ;
  return rv;
}
} // namespace

namespace {
void delete_handler(Http2Handler *handler) {
  handler->remove_self();
  delete handler;
}
} // namespace

namespace {
void print_session_id(int64_t id) { std::cout << "[id=" << id << "] "; }
} // namespace

namespace {
void append_nv(Stream *stream, const std::vector<nghttp2_nv> &nva) {
  for (size_t i = 0; i < nva.size(); ++i) {
    auto &nv = nva[i];
    auto token = http2::lookup_token(nv.name, nv.namelen);
    if (token != -1) {
      http2::index_header(stream->hdidx, token, i);
    }
    http2::add_header(stream->headers, nv.name, nv.namelen, nv.value,
                      nv.valuelen, nv.flags & NGHTTP2_NV_FLAG_NO_INDEX);
  }
}
} // namespace

Config::Config()
    : stream_read_timeout(60.), stream_write_timeout(60.),
      session_option(nullptr), data_ptr(nullptr), padding(0), num_worker(1),
      header_table_size(-1), port(0), verbose(false), daemon(false),
      verify_client(false), no_tls(false), error_gzip(false),
      early_response(false) {
  nghttp2_option_new(&session_option);
  nghttp2_option_set_recv_client_preface(session_option, 1);
}

Config::~Config() { nghttp2_option_del(session_option); }

namespace {
void stream_timeout_cb(struct ev_loop *loop, ev_timer *w, int revents) {
  int rv;
  auto stream = static_cast<Stream *>(w->data);
  auto hd = stream->handler;
  auto config = hd->get_config();

  ev_timer_stop(hd->get_loop(), &stream->rtimer);
  ev_timer_stop(hd->get_loop(), &stream->wtimer);

  if (config->verbose) {
    print_session_id(hd->session_id());
    print_timer();
    std::cout << " timeout stream_id=" << stream->stream_id << std::endl;
  }

  hd->submit_rst_stream(stream, NGHTTP2_INTERNAL_ERROR);

  rv = hd->on_write();
  if (rv == -1) {
    delete_handler(hd);
  }
}
} // namespace

namespace {
void add_stream_read_timeout(Stream *stream) {
  auto hd = stream->handler;
  ev_timer_again(hd->get_loop(), &stream->rtimer);
}
} // namespace

namespace {
void add_stream_read_timeout_if_pending(Stream *stream) {
  auto hd = stream->handler;
  if (ev_is_active(&stream->rtimer)) {
    ev_timer_again(hd->get_loop(), &stream->rtimer);
  }
}
} // namespace

namespace {
void add_stream_write_timeout(Stream *stream) {
  auto hd = stream->handler;
  ev_timer_again(hd->get_loop(), &stream->wtimer);
}
} // namespace

namespace {
void remove_stream_read_timeout(Stream *stream) {
  auto hd = stream->handler;
  ev_timer_stop(hd->get_loop(), &stream->rtimer);
}
} // namespace

namespace {
void remove_stream_write_timeout(Stream *stream) {
  auto hd = stream->handler;
  ev_timer_stop(hd->get_loop(), &stream->wtimer);
}
} // namespace

namespace {
std::shared_ptr<std::string> cached_date;
} // namespace

namespace {
void refresh_cb(struct ev_loop *loop, ev_timer *w, int revents) {
  cached_date = std::make_shared<std::string>(util::http_date(time(nullptr)));
}
} // namespace

namespace {
void fill_callback(nghttp2_session_callbacks *callbacks, const Config *config);
} // namespace

class Sessions {
public:
  Sessions(struct ev_loop *loop, const Config *config, SSL_CTX *ssl_ctx)
      : loop_(loop), config_(config), ssl_ctx_(ssl_ctx), callbacks_(nullptr),
        next_session_id_(1) {
    nghttp2_session_callbacks_new(&callbacks_);

    fill_callback(callbacks_, config_);
  }
  ~Sessions() {
    for (auto handler : handlers_) {
      delete handler;
    }
    nghttp2_session_callbacks_del(callbacks_);
  }
  void add_handler(Http2Handler *handler) { handlers_.insert(handler); }
  void remove_handler(Http2Handler *handler) { handlers_.erase(handler); }
  SSL_CTX *get_ssl_ctx() const { return ssl_ctx_; }
  SSL *ssl_session_new(int fd) {
    SSL *ssl = SSL_new(ssl_ctx_);
    if (!ssl) {
      std::cerr << "SSL_new() failed" << std::endl;
      return nullptr;
    }
    if (SSL_set_fd(ssl, fd) == 0) {
      std::cerr << "SSL_set_fd() failed" << std::endl;
      SSL_free(ssl);
      return nullptr;
    }
    return ssl;
  }
  const Config *get_config() const { return config_; }
  struct ev_loop *get_loop() const {
    return loop_;
  }
  int64_t get_next_session_id() {
    auto session_id = next_session_id_;
    if (next_session_id_ == std::numeric_limits<int64_t>::max()) {
      next_session_id_ = 1;
    } else {
      ++next_session_id_;
    }
    return session_id;
  }
  const nghttp2_session_callbacks *get_callbacks() const { return callbacks_; }
  void accept_connection(int fd) {
    int val = 1;
    (void)setsockopt(fd, IPPROTO_TCP, TCP_NODELAY,
                     reinterpret_cast<char *>(&val), sizeof(val));
    SSL *ssl = nullptr;
    if (ssl_ctx_) {
      ssl = ssl_session_new(fd);
      if (!ssl) {
        close(fd);
        return;
      }
    }
    auto handler =
        util::make_unique<Http2Handler>(this, fd, ssl, get_next_session_id());
    handler->setup_bev();
    if (!ssl) {
      if (handler->on_connect() != 0) {
        return;
      }
    }
    add_handler(handler.release());
  }

private:
  std::set<Http2Handler *> handlers_;
  struct ev_loop *loop_;
  const Config *config_;
  SSL_CTX *ssl_ctx_;
  nghttp2_session_callbacks *callbacks_;
  int64_t next_session_id_;
};

Stream::Stream(Http2Handler *handler, int32_t stream_id)
    : handler(handler), body_left(0), stream_id(stream_id), file(-1) {
  auto config = handler->get_config();
  ev_timer_init(&rtimer, stream_timeout_cb, 0., config->stream_read_timeout);
  ev_timer_init(&wtimer, stream_timeout_cb, 0., config->stream_write_timeout);
  rtimer.data = this;
  wtimer.data = this;

  headers.reserve(10);

  http2::init_hdidx(hdidx);
}

Stream::~Stream() {
  if (file != -1) {
    close(file);
  }

  auto loop = handler->get_loop();
  ev_timer_stop(loop, &rtimer);
  ev_timer_stop(loop, &wtimer);
}

namespace {
void on_session_closed(Http2Handler *hd, int64_t session_id) {
  if (hd->get_config()->verbose) {
    print_session_id(session_id);
    print_timer();
    std::cout << " closed" << std::endl;
  }
}
} // namespace

namespace {
void settings_timeout_cb(struct ev_loop *loop, ev_timer *w, int revents) {
  auto hd = static_cast<Http2Handler *>(w->data);
  hd->terminate_session(NGHTTP2_SETTINGS_TIMEOUT);
  hd->on_write();
}
} // namespace

namespace {
void readcb(struct ev_loop *loop, ev_io *w, int revents) {
  int rv;
  auto handler = static_cast<Http2Handler *>(w->data);

  rv = handler->on_read();
  if (rv == -1) {
    delete_handler(handler);
  }
}
} // namespace

namespace {
void writecb(struct ev_loop *loop, ev_io *w, int revents) {
  int rv;
  auto handler = static_cast<Http2Handler *>(w->data);

  rv = handler->on_write();
  if (rv == -1) {
    delete_handler(handler);
  }
}
} // namespace

Http2Handler::Http2Handler(Sessions *sessions, int fd, SSL *ssl,
                           int64_t session_id)
    : session_id_(session_id), session_(nullptr), sessions_(sessions),
      ssl_(ssl), data_pending_(nullptr), data_pendinglen_(0), fd_(fd) {
  ev_timer_init(&settings_timerev_, settings_timeout_cb, 10., 0.);
  ev_io_init(&wev_, writecb, fd, EV_WRITE);
  ev_io_init(&rev_, readcb, fd, EV_READ);

  settings_timerev_.data = this;
  wev_.data = this;
  rev_.data = this;

  auto loop = sessions_->get_loop();
  ev_io_start(loop, &rev_);

  if (ssl) {
    SSL_set_accept_state(ssl);
    read_ = &Http2Handler::tls_handshake;
    write_ = &Http2Handler::tls_handshake;
  } else {
    read_ = &Http2Handler::read_clear;
    write_ = &Http2Handler::write_clear;
  }
}

Http2Handler::~Http2Handler() {
  on_session_closed(this, session_id_);
  nghttp2_session_del(session_);
  if (ssl_) {
    SSL_set_shutdown(ssl_, SSL_RECEIVED_SHUTDOWN);
    SSL_shutdown(ssl_);
  }
  auto loop = sessions_->get_loop();
  ev_timer_stop(loop, &settings_timerev_);
  ev_io_stop(loop, &rev_);
  ev_io_stop(loop, &wev_);
  if (ssl_) {
    SSL_free(ssl_);
  }
  shutdown(fd_, SHUT_WR);
  close(fd_);
}

void Http2Handler::remove_self() { sessions_->remove_handler(this); }

struct ev_loop *Http2Handler::get_loop() const {
  return sessions_->get_loop();
}

int Http2Handler::setup_bev() { return 0; }

int Http2Handler::fill_wb() {
  if (data_pending_) {
    auto n = std::min(wb_.wleft(), data_pendinglen_);
    wb_.write(data_pending_, n);
    if (n < data_pendinglen_) {
      data_pending_ += n;
      data_pendinglen_ -= n;
      return 0;
    }

    data_pending_ = nullptr;
    data_pendinglen_ = 0;
  }

  for (;;) {
    const uint8_t *data;
    auto datalen = nghttp2_session_mem_send(session_, &data);

    if (datalen < 0) {
      std::cerr << "nghttp2_session_mem_send() returned error: "
                << nghttp2_strerror(datalen) << std::endl;
      return -1;
    }
    if (datalen == 0) {
      break;
    }
    auto n = wb_.write(data, datalen);
    if (n < static_cast<decltype(n)>(datalen)) {
      data_pending_ = data + n;
      data_pendinglen_ = datalen - n;
      break;
    }
  }
  return 0;
}

int Http2Handler::read_clear() {
  int rv;
  uint8_t buf[8192];

  for (;;) {
    ssize_t nread;
    while ((nread = read(fd_, buf, sizeof(buf))) == -1 && errno == EINTR)
      ;
    if (nread == -1) {
      if (errno == EAGAIN || errno == EWOULDBLOCK) {
        break;
      }
      return -1;
    }
    if (nread == 0) {
      return -1;
    }
    rv = nghttp2_session_mem_recv(session_, buf, nread);
    if (rv < 0) {
      std::cerr << "nghttp2_session_mem_recv() returned error: "
                << nghttp2_strerror(rv) << std::endl;
      return -1;
    }
  }

  return write_(*this);
}

int Http2Handler::write_clear() {
  auto loop = sessions_->get_loop();
  for (;;) {
    if (wb_.rleft() > 0) {
      struct iovec iov[2];
      auto iovcnt = wb_.riovec(iov);

      ssize_t nwrite;
      while ((nwrite = writev(fd_, iov, iovcnt)) == -1 && errno == EINTR)
        ;
      if (nwrite == -1) {
        if (errno == EAGAIN || errno == EWOULDBLOCK) {
          ev_io_start(loop, &wev_);
          return 0;
        }
        return -1;
      }
      wb_.drain(nwrite);
      continue;
    }
    wb_.reset();
    if (fill_wb() != 0) {
      return -1;
    }
    if (wb_.rleft() == 0) {
      break;
    }
  }

  if (wb_.rleft() == 0) {
    ev_io_stop(loop, &wev_);
  } else {
    ev_io_start(loop, &wev_);
  }

  if (nghttp2_session_want_read(session_) == 0 &&
      nghttp2_session_want_write(session_) == 0 && wb_.rleft() == 0) {
    return -1;
  }

  return 0;
}

int Http2Handler::tls_handshake() {
  ev_io_stop(sessions_->get_loop(), &wev_);

  auto rv = SSL_do_handshake(ssl_);

  if (rv == 0) {
    return -1;
  }

  if (rv < 0) {
    auto err = SSL_get_error(ssl_, rv);
    switch (err) {
    case SSL_ERROR_WANT_READ:
      return 0;
    case SSL_ERROR_WANT_WRITE:
      ev_io_start(sessions_->get_loop(), &wev_);
      return 0;
    default:
      return -1;
    }
  }

  if (sessions_->get_config()->verbose) {
    std::cerr << "SSL/TLS handshake completed" << std::endl;
  }

  if (verify_npn_result() != 0) {
    return -1;
  }

  read_ = &Http2Handler::read_tls;
  write_ = &Http2Handler::write_tls;

  if (on_connect() != 0) {
    return -1;
  }

  return 0;
}

int Http2Handler::read_tls() {
  uint8_t buf[8192];

  for (;;) {
    auto rv = SSL_read(ssl_, buf, sizeof(buf));

    if (rv == 0) {
      return -1;
    }

    if (rv < 0) {
      auto err = SSL_get_error(ssl_, rv);
      switch (err) {
      case SSL_ERROR_WANT_READ:
        goto fin;
      case SSL_ERROR_WANT_WRITE:
        ev_io_start(sessions_->get_loop(), &wev_);
        goto fin;
      default:
        return -1;
      }
    }

    auto nread = rv;
    rv = nghttp2_session_mem_recv(session_, buf, nread);
    if (rv < 0) {
      std::cerr << "nghttp2_session_mem_recv() returned error: "
                << nghttp2_strerror(rv) << std::endl;
      return -1;
    }
  }

fin:
  return write_(*this);
}

int Http2Handler::write_tls() {
  auto loop = sessions_->get_loop();
  for (;;) {
    if (wb_.rleft() > 0) {
      const void *p;
      size_t len;
      std::tie(p, len) = wb_.get();

      auto rv = SSL_write(ssl_, p, len);

      if (rv == 0) {
        return -1;
      }

      if (rv < 0) {
        auto err = SSL_get_error(ssl_, rv);
        switch (err) {
        case SSL_ERROR_WANT_READ:
          ev_io_stop(loop, &wev_);
          return 0;
        case SSL_ERROR_WANT_WRITE:
          ev_io_start(sessions_->get_loop(), &wev_);
          return 0;
        default:
          return -1;
        }
      }

      wb_.drain(rv);
      continue;
    }
    wb_.reset();
    if (fill_wb() != 0) {
      return -1;
    }
    if (wb_.rleft() == 0) {
      break;
    }
  }

  if (wb_.rleft() == 0) {
    ev_io_stop(loop, &wev_);
  } else {
    ev_io_start(loop, &wev_);
  }

  if (nghttp2_session_want_read(session_) == 0 &&
      nghttp2_session_want_write(session_) == 0 && wb_.rleft() == 0) {
    return -1;
  }

  return 0;
}

int Http2Handler::on_read() { return read_(*this); }

int Http2Handler::on_write() { return write_(*this); }

int Http2Handler::on_connect() {
  int r;

  r = nghttp2_session_server_new2(&session_, sessions_->get_callbacks(), this,
                                  sessions_->get_config()->session_option);
  if (r != 0) {
    return r;
  }
  nghttp2_settings_entry entry[4];
  size_t niv = 1;

  entry[0].settings_id = NGHTTP2_SETTINGS_MAX_CONCURRENT_STREAMS;
  entry[0].value = 100;

  if (sessions_->get_config()->header_table_size >= 0) {
    entry[niv].settings_id = NGHTTP2_SETTINGS_HEADER_TABLE_SIZE;
    entry[niv].value = sessions_->get_config()->header_table_size;
    ++niv;
  }
  r = nghttp2_submit_settings(session_, NGHTTP2_FLAG_NONE, entry, niv);
  if (r != 0) {
    return r;
  }

  ev_timer_start(sessions_->get_loop(), &settings_timerev_);

  return on_write();
}

int Http2Handler::verify_npn_result() {
  const unsigned char *next_proto = nullptr;
  unsigned int next_proto_len;
  // Check the negotiated protocol in NPN or ALPN
  SSL_get0_next_proto_negotiated(ssl_, &next_proto, &next_proto_len);
  for (int i = 0; i < 2; ++i) {
    if (next_proto) {
      if (sessions_->get_config()->verbose) {
        std::string proto(next_proto, next_proto + next_proto_len);
        std::cout << "The negotiated protocol: " << proto << std::endl;
      }
      if (util::check_h2_is_selected(next_proto, next_proto_len)) {
        return 0;
      }
      break;
    } else {
#if OPENSSL_VERSION_NUMBER >= 0x10002000L
      SSL_get0_alpn_selected(ssl_, &next_proto, &next_proto_len);
#else  // OPENSSL_VERSION_NUMBER < 0x10002000L
      break;
#endif // OPENSSL_VERSION_NUMBER < 0x10002000L
    }
  }
  if (sessions_->get_config()->verbose) {
    std::cerr << "Client did not advertise HTTP/2 protocol."
              << " (nghttp2 expects " << NGHTTP2_PROTO_VERSION_ID << ")"
              << std::endl;
  }
  return -1;
}

int Http2Handler::submit_file_response(const std::string &status,
                                       Stream *stream, time_t last_modified,
                                       off_t file_length,
                                       nghttp2_data_provider *data_prd) {
  auto date_str = cached_date;
  std::string content_length = util::utos(file_length);
  std::string last_modified_str;
  nghttp2_nv nva[] = {
      http2::make_nv_ls(":status", status),
      http2::make_nv_ls("server", NGHTTPD_SERVER),
      http2::make_nv_ls("content-length", content_length),
      http2::make_nv_ll("cache-control", "max-age=3600"),
      http2::make_nv_ls("date", *date_str),
      http2::make_nv_ll("", ""),
  };
  size_t nvlen = 5;
  if (last_modified != 0) {
    last_modified_str = util::http_date(last_modified);
    nva[nvlen++] = http2::make_nv_ls("last-modified", last_modified_str);
  }
  return nghttp2_submit_response(session_, stream->stream_id, nva, nvlen,
                                 data_prd);
}

int Http2Handler::submit_response(const std::string &status, int32_t stream_id,
                                  const Headers &headers,
                                  nghttp2_data_provider *data_prd) {
  auto date_str = cached_date;
  auto nva =
      std::vector<nghttp2_nv>{http2::make_nv_ls(":status", status),
                              http2::make_nv_ls("server", NGHTTPD_SERVER),
                              http2::make_nv_ls("date", *date_str)};
  for (auto &nv : headers) {
    nva.push_back(http2::make_nv(nv.name, nv.value, nv.no_index));
  }
  int r = nghttp2_submit_response(session_, stream_id, nva.data(), nva.size(),
                                  data_prd);
  return r;
}

int Http2Handler::submit_response(const std::string &status, int32_t stream_id,
                                  nghttp2_data_provider *data_prd) {
  auto nva =
      std::vector<nghttp2_nv>{http2::make_nv_ls(":status", status),
                              http2::make_nv_ls("server", NGHTTPD_SERVER)};
  return nghttp2_submit_response(session_, stream_id, nva.data(), nva.size(),
                                 data_prd);
}

int Http2Handler::submit_non_final_response(const std::string &status,
                                            int32_t stream_id) {
  auto nva = std::vector<nghttp2_nv>{http2::make_nv_ls(":status", status)};
  return nghttp2_submit_headers(session_, NGHTTP2_FLAG_NONE, stream_id, nullptr,
                                nva.data(), nva.size(), nullptr);
}

int Http2Handler::submit_push_promise(Stream *stream,
                                      const std::string &push_path) {
  auto authority =
      http2::get_header(stream->hdidx, http2::HD__AUTHORITY, stream->headers);

  if (!authority) {
    authority =
        http2::get_header(stream->hdidx, http2::HD_HOST, stream->headers);
  }

  auto nva = std::vector<nghttp2_nv>{
      http2::make_nv_ll(":method", "GET"),
      http2::make_nv_ls(":path", push_path),
      get_config()->no_tls ? http2::make_nv_ll(":scheme", "http")
                           : http2::make_nv_ll(":scheme", "https"),
      http2::make_nv_ls(":authority", authority->value)};

  auto promised_stream_id = nghttp2_submit_push_promise(
      session_, NGHTTP2_FLAG_END_HEADERS, stream->stream_id, nva.data(),
      nva.size(), nullptr);

  if (promised_stream_id < 0) {
    return promised_stream_id;
  }

  auto promised_stream = util::make_unique<Stream>(this, promised_stream_id);

  append_nv(promised_stream.get(), nva);
  add_stream(promised_stream_id, std::move(promised_stream));

  return 0;
}

int Http2Handler::submit_rst_stream(Stream *stream, uint32_t error_code) {
  remove_stream_read_timeout(stream);
  remove_stream_write_timeout(stream);

  return nghttp2_submit_rst_stream(session_, NGHTTP2_FLAG_NONE,
                                   stream->stream_id, error_code);
}

void Http2Handler::add_stream(int32_t stream_id,
                              std::unique_ptr<Stream> stream) {
  id2stream_[stream_id] = std::move(stream);
}

void Http2Handler::remove_stream(int32_t stream_id) {
  id2stream_.erase(stream_id);
}

Stream *Http2Handler::get_stream(int32_t stream_id) {
  auto itr = id2stream_.find(stream_id);
  if (itr == std::end(id2stream_)) {
    return nullptr;
  } else {
    return (*itr).second.get();
  }
}

int64_t Http2Handler::session_id() const { return session_id_; }

Sessions *Http2Handler::get_sessions() const { return sessions_; }

const Config *Http2Handler::get_config() const {
  return sessions_->get_config();
}

void Http2Handler::remove_settings_timer() {
  ev_timer_stop(sessions_->get_loop(), &settings_timerev_);
}

void Http2Handler::terminate_session(uint32_t error_code) {
  nghttp2_session_terminate_session(session_, error_code);
}

ssize_t file_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) {
  auto hd = static_cast<Http2Handler *>(user_data);
  auto stream = hd->get_stream(stream_id);

  int fd = source->fd;
  ssize_t nread;

  while ((nread = read(fd, buf, length)) == -1 && errno == EINTR)
    ;

  if (nread == -1) {
    remove_stream_read_timeout(stream);
    remove_stream_write_timeout(stream);

    return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
  }

  stream->body_left -= nread;
  if (nread == 0 || stream->body_left <= 0) {
    *data_flags |= NGHTTP2_DATA_FLAG_EOF;

    if (nghttp2_session_get_stream_remote_close(session, stream_id) == 0) {
      remove_stream_read_timeout(stream);
      remove_stream_write_timeout(stream);

      hd->submit_rst_stream(stream, NGHTTP2_NO_ERROR);
    }
  }

  return nread;
}

namespace {
void prepare_status_response(Stream *stream, Http2Handler *hd,
                             const std::string &status) {
  int pipefd[2];
  if (status == STATUS_304 || pipe(pipefd) == -1) {
    hd->submit_response(status, stream->stream_id, 0);
    return;
  }
  std::string body;
  body.reserve(256);
  body = "<html><head><title>";
  body += status;
  body += "</title></head><body><h1>";
  body += status;
  body += "</h1><hr><address>";
  body += NGHTTPD_SERVER;
  body += " at port ";
  body += util::utos(hd->get_config()->port);
  body += "</address>";
  body += "</body></html>";

  Headers headers;
  if (hd->get_config()->error_gzip) {
    gzFile write_fd = gzdopen(pipefd[1], "w");
    gzwrite(write_fd, body.c_str(), body.size());
    gzclose(write_fd);
    headers.emplace_back("content-encoding", "gzip");
  } else {
    ssize_t rv;

    while ((rv = write(pipefd[1], body.c_str(), body.size())) == -1 &&
           errno == EINTR)
      ;

    if (rv != static_cast<ssize_t>(body.size())) {
      std::cerr << "Could not write all response body: " << rv << std::endl;
    }
  }
  close(pipefd[1]);

  stream->file = pipefd[0];
  stream->body_left = body.size();
  nghttp2_data_provider data_prd;
  data_prd.source.fd = pipefd[0];
  data_prd.read_callback = file_read_callback;
  headers.emplace_back("content-type", "text/html; charset=UTF-8");
  hd->submit_response(status, stream->stream_id, headers, &data_prd);
}
} // namespace

namespace {
void prepare_redirect_response(Stream *stream, Http2Handler *hd,
                               const std::string &path,
                               const std::string &status) {
  auto scheme =
      http2::get_header(stream->hdidx, http2::HD__SCHEME, stream->headers);
  auto authority =
      http2::get_header(stream->hdidx, http2::HD__AUTHORITY, stream->headers);
  if (!authority) {
    authority =
        http2::get_header(stream->hdidx, http2::HD_HOST, stream->headers);
  }

  auto redirect_url = scheme->value;
  redirect_url += "://";
  redirect_url += authority->value;
  redirect_url += path;

  auto headers = Headers{{"location", redirect_url}};

  hd->submit_response(status, stream->stream_id, headers, nullptr);
}
} // namespace

namespace {
void prepare_response(Stream *stream, Http2Handler *hd,
                      bool allow_push = true) {
  int rv;
  auto reqpath =
      http2::get_header(stream->hdidx, http2::HD__PATH, stream->headers)->value;
  auto ims =
      get_header(stream->hdidx, http2::HD_IF_MODIFIED_SINCE, stream->headers);

  time_t last_mod = 0;
  bool last_mod_found = false;
  if (ims) {
    last_mod_found = true;
    last_mod = util::parse_http_date(ims->value);
  }
  auto query_pos = reqpath.find("?");
  std::string url;
  if (query_pos != std::string::npos) {
    // Do not response to this request to allow clients to test timeouts.
    if (reqpath.find("nghttpd_do_not_respond_to_req=yes", query_pos) !=
        std::string::npos) {
      return;
    }
    url = reqpath.substr(0, query_pos);
  } else {
    url = reqpath;
  }

  url = util::percentDecode(url.begin(), url.end());
  if (!util::check_path(url)) {
    prepare_status_response(stream, hd, STATUS_404);
    return;
  }
  auto push_itr = hd->get_config()->push.find(url);
  if (allow_push && push_itr != std::end(hd->get_config()->push)) {
    for (auto &push_path : (*push_itr).second) {
      rv = hd->submit_push_promise(stream, push_path);
      if (rv != 0) {
        std::cerr << "nghttp2_submit_push_promise() returned error: "
                  << nghttp2_strerror(rv) << std::endl;
      }
    }
  }
  std::string path = hd->get_config()->htdocs + url;
  if (path[path.size() - 1] == '/') {
    path += DEFAULT_HTML;
  }
  int file = open(path.c_str(), O_RDONLY | O_BINARY);
  if (file == -1) {
    prepare_status_response(stream, hd, STATUS_404);

    return;
  }

  struct stat buf;

  if (fstat(file, &buf) == -1) {
    close(file);
    prepare_status_response(stream, hd, STATUS_404);

    return;
  }

  if (buf.st_mode & S_IFDIR) {
    close(file);

    if (query_pos == std::string::npos) {
      reqpath += "/";
    } else {
      reqpath.insert(query_pos, "/");
    }

    prepare_redirect_response(stream, hd, reqpath, STATUS_301);

    return;
  }

  stream->file = file;
  stream->body_left = buf.st_size;

  nghttp2_data_provider data_prd;

  data_prd.source.fd = file;
  data_prd.read_callback = file_read_callback;

  if (last_mod_found && buf.st_mtime <= last_mod) {
    prepare_status_response(stream, hd, STATUS_304);

    return;
  }

  hd->submit_file_response(STATUS_200, stream, buf.st_mtime, buf.st_size,
                           &data_prd);
}
} // namespace

namespace {
int on_header_callback(nghttp2_session *session, const nghttp2_frame *frame,
                       const uint8_t *name, size_t namelen,
                       const uint8_t *value, size_t valuelen, uint8_t flags,
                       void *user_data) {
  auto hd = static_cast<Http2Handler *>(user_data);
  if (hd->get_config()->verbose) {
    print_session_id(hd->session_id());
    verbose_on_header_callback(session, frame, name, namelen, value, valuelen,
                               flags, user_data);
  }
  if (frame->hd.type != NGHTTP2_HEADERS ||
      frame->headers.cat != NGHTTP2_HCAT_REQUEST) {
    return 0;
  }
  auto stream = hd->get_stream(frame->hd.stream_id);
  if (!stream) {
    return 0;
  }
  if (!http2::check_nv(name, namelen, value, valuelen)) {
    return 0;
  }

  auto token = http2::lookup_token(name, namelen);

  if (name[0] == ':') {
    if ((!stream->headers.empty() &&
         stream->headers.back().name.c_str()[0] != ':') ||
        !http2::check_http2_request_pseudo_header(stream->hdidx, token)) {

      nghttp2_submit_rst_stream(session, NGHTTP2_FLAG_NONE, frame->hd.stream_id,
                                NGHTTP2_PROTOCOL_ERROR);
      return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
    }
  }

  if (!http2::http2_header_allowed(token)) {
    nghttp2_submit_rst_stream(session, NGHTTP2_FLAG_NONE, frame->hd.stream_id,
                              NGHTTP2_PROTOCOL_ERROR);
    return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
  }

  http2::index_header(stream->hdidx, token, stream->headers.size());
  http2::add_header(stream->headers, name, namelen, value, valuelen,
                    flags & NGHTTP2_NV_FLAG_NO_INDEX);
  return 0;
}
} // namespace

namespace {
int on_begin_headers_callback(nghttp2_session *session,
                              const nghttp2_frame *frame, void *user_data) {
  auto hd = static_cast<Http2Handler *>(user_data);

  if (frame->hd.type != NGHTTP2_HEADERS ||
      frame->headers.cat != NGHTTP2_HCAT_REQUEST) {
    return 0;
  }

  auto stream = util::make_unique<Stream>(hd, frame->hd.stream_id);

  add_stream_read_timeout(stream.get());

  hd->add_stream(frame->hd.stream_id, std::move(stream));

  return 0;
}
} // namespace

namespace {
int hd_on_frame_recv_callback(nghttp2_session *session,
                              const nghttp2_frame *frame, void *user_data) {
  auto hd = static_cast<Http2Handler *>(user_data);
  if (hd->get_config()->verbose) {
    print_session_id(hd->session_id());
    verbose_on_frame_recv_callback(session, frame, user_data);
  }
  switch (frame->hd.type) {
  case NGHTTP2_DATA: {
    // TODO Handle POST
    auto stream = hd->get_stream(frame->hd.stream_id);
    if (!stream) {
      return 0;
    }

    if (frame->hd.flags & NGHTTP2_FLAG_END_STREAM) {
      remove_stream_read_timeout(stream);
      if (!hd->get_config()->early_response) {
        prepare_response(stream, hd);
      }
    } else {
      add_stream_read_timeout(stream);
    }

    break;
  }
  case NGHTTP2_HEADERS: {
    auto stream = hd->get_stream(frame->hd.stream_id);
    if (!stream) {
      return 0;
    }

    if (frame->headers.cat == NGHTTP2_HCAT_REQUEST) {

      if (!http2::http2_mandatory_request_headers_presence(stream->hdidx)) {
        hd->submit_rst_stream(stream, NGHTTP2_PROTOCOL_ERROR);
        return 0;
      }

      auto expect100 =
          http2::get_header(stream->hdidx, http2::HD_EXPECT, stream->headers);

      if (expect100 && util::strieq("100-continue", expect100->value.c_str())) {
        hd->submit_non_final_response("100", frame->hd.stream_id);
      }

      if (hd->get_config()->early_response) {
        prepare_response(stream, hd);
      }
    }

    if (frame->hd.flags & NGHTTP2_FLAG_END_STREAM) {
      remove_stream_read_timeout(stream);
      if (!hd->get_config()->early_response) {
        prepare_response(stream, hd);
      }
    } else {
      add_stream_read_timeout(stream);
    }

    break;
  }
  case NGHTTP2_SETTINGS:
    if (frame->hd.flags & NGHTTP2_FLAG_ACK) {
      hd->remove_settings_timer();
    }
    break;
  case NGHTTP2_PUSH_PROMISE:
    nghttp2_submit_rst_stream(session, NGHTTP2_FLAG_NONE,
                              frame->push_promise.promised_stream_id,
                              NGHTTP2_REFUSED_STREAM);
    break;
  default:
    break;
  }
  return 0;
}
} // namespace

namespace {
int hd_on_frame_send_callback(nghttp2_session *session,
                              const nghttp2_frame *frame, void *user_data) {
  auto hd = static_cast<Http2Handler *>(user_data);

  if (hd->get_config()->verbose) {
    print_session_id(hd->session_id());
    verbose_on_frame_send_callback(session, frame, user_data);
  }

  switch (frame->hd.type) {
  case NGHTTP2_DATA:
  case NGHTTP2_HEADERS: {
    auto stream = hd->get_stream(frame->hd.stream_id);

    if (!stream) {
      return 0;
    }

    if (frame->hd.flags & NGHTTP2_FLAG_END_STREAM) {
      remove_stream_write_timeout(stream);
    } else if (std::min(nghttp2_session_get_stream_remote_window_size(
                            session, frame->hd.stream_id),
                        nghttp2_session_get_remote_window_size(session)) <= 0) {
      // If stream is blocked by flow control, enable write timeout.
      add_stream_read_timeout_if_pending(stream);
      add_stream_write_timeout(stream);
    } else {
      add_stream_read_timeout_if_pending(stream);
      remove_stream_write_timeout(stream);
    }

    break;
  }
  case NGHTTP2_PUSH_PROMISE: {
    auto promised_stream_id = frame->push_promise.promised_stream_id;
    auto promised_stream = hd->get_stream(promised_stream_id);
    auto stream = hd->get_stream(frame->hd.stream_id);

    if (!stream || !promised_stream) {
      return 0;
    }

    add_stream_read_timeout_if_pending(stream);
    add_stream_write_timeout(stream);

    prepare_response(promised_stream, hd, /*allow_push */ false);
  }
  }
  return 0;
}
} // namespace

namespace {
ssize_t select_padding_callback(nghttp2_session *session,
                                const nghttp2_frame *frame, size_t max_payload,
                                void *user_data) {
  auto hd = static_cast<Http2Handler *>(user_data);
  return std::min(max_payload, frame->hd.length + hd->get_config()->padding);
}
} // 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 hd = static_cast<Http2Handler *>(user_data);
  auto stream = hd->get_stream(stream_id);

  if (!stream) {
    return 0;
  }

  // TODO Handle POST

  add_stream_read_timeout(stream);

  return 0;
}
} // namespace

namespace {
int on_stream_close_callback(nghttp2_session *session, int32_t stream_id,
                             uint32_t error_code, void *user_data) {
  auto hd = static_cast<Http2Handler *>(user_data);
  hd->remove_stream(stream_id);
  if (hd->get_config()->verbose) {
    print_session_id(hd->session_id());
    print_timer();
    printf(" stream_id=%d closed\n", stream_id);
    fflush(stdout);
  }
  return 0;
}
} // namespace

namespace {
void fill_callback(nghttp2_session_callbacks *callbacks, const Config *config) {
  nghttp2_session_callbacks_set_on_stream_close_callback(
      callbacks, on_stream_close_callback);

  nghttp2_session_callbacks_set_on_frame_recv_callback(
      callbacks, hd_on_frame_recv_callback);

  nghttp2_session_callbacks_set_on_frame_send_callback(
      callbacks, hd_on_frame_send_callback);

  if (config->verbose) {
    nghttp2_session_callbacks_set_on_invalid_frame_recv_callback(
        callbacks, verbose_on_invalid_frame_recv_callback);
  }

  nghttp2_session_callbacks_set_on_data_chunk_recv_callback(
      callbacks, on_data_chunk_recv_callback);

  nghttp2_session_callbacks_set_on_header_callback(callbacks,
                                                   on_header_callback);

  nghttp2_session_callbacks_set_on_begin_headers_callback(
      callbacks, on_begin_headers_callback);

  if (config->padding) {
    nghttp2_session_callbacks_set_select_padding_callback(
        callbacks, select_padding_callback);
  }
}
} // namespace

struct ClientInfo {
  int fd;
};

struct Worker {
  std::unique_ptr<Sessions> sessions;
  ev_async w;
  // protectes q
  std::mutex m;
  std::deque<ClientInfo> q;
};

namespace {
void worker_acceptcb(struct ev_loop *loop, ev_async *w, int revents) {
  auto worker = static_cast<Worker *>(w->data);
  auto &sessions = worker->sessions;

  std::deque<ClientInfo> q;
  {
    std::lock_guard<std::mutex> lock(worker->m);
    q.swap(worker->q);
  }

  for (auto c : q) {
    sessions->accept_connection(c.fd);
  }
}
} // namespace

namespace {
void run_worker(Worker *worker) { ev_run(worker->sessions->get_loop(), 0); }
} // namespace

class AcceptHandler {
public:
  AcceptHandler(Sessions *sessions, const Config *config)
      : sessions_(sessions), config_(config), next_worker_(0) {
    if (config_->num_worker == 1) {
      return;
    }
    for (size_t i = 0; i < config_->num_worker; ++i) {
      if (config_->verbose) {
        std::cerr << "spawning thread #" << i << std::endl;
      }
      auto worker = util::make_unique<Worker>();
      auto loop = ev_loop_new(0);
      worker->sessions =
          util::make_unique<Sessions>(loop, config_, sessions_->get_ssl_ctx());
      ev_async_init(&worker->w, worker_acceptcb);
      worker->w.data = worker.get();
      ev_async_start(loop, &worker->w);

      auto t = std::thread(run_worker, worker.get());
      t.detach();
      workers_.push_back(std::move(worker));
    }
  }
  void accept_connection(int fd) {
    if (config_->num_worker == 1) {
      sessions_->accept_connection(fd);
      return;
    }

    // Dispatch client to the one of the worker threads, in a round
    // robin manner.
    auto &worker = workers_[next_worker_];
    if (next_worker_ == config_->num_worker - 1) {
      next_worker_ = 0;
    } else {
      ++next_worker_;
    }
    {
      std::lock_guard<std::mutex> lock(worker->m);
      worker->q.push_back({fd});
    }
    ev_async_send(worker->sessions->get_loop(), &worker->w);
  }

private:
  std::vector<std::unique_ptr<Worker>> workers_;
  Sessions *sessions_;
  const Config *config_;
  // In multi threading mode, this points to the next thread that
  // client will be dispatched.
  size_t next_worker_;
};

namespace {
void acceptcb(struct ev_loop *loop, ev_io *w, int revents);
} // namespace

class ListenEventHandler {
public:
  ListenEventHandler(Sessions *sessions, int fd,
                     std::shared_ptr<AcceptHandler> acceptor)
      : acceptor_(acceptor), sessions_(sessions), fd_(fd) {
    ev_io_init(&w_, acceptcb, fd, EV_READ);
    w_.data = this;
    ev_io_start(sessions_->get_loop(), &w_);
  }
  void accept_connection() {
    for (;;) {
      auto fd = accept(fd_, nullptr, nullptr);
      if (fd == -1) {
        if (errno == EAGAIN || errno == EWOULDBLOCK) {
          break;
        }
        continue;
      }
      make_socket_nonblocking(fd);
      acceptor_->accept_connection(fd);
    }
  }

private:
  ev_io w_;
  std::shared_ptr<AcceptHandler> acceptor_;
  Sessions *sessions_;
  int fd_;
};

namespace {
void acceptcb(struct ev_loop *loop, ev_io *w, int revents) {
  auto handler = static_cast<ListenEventHandler *>(w->data);
  handler->accept_connection();
}
} // namespace

HttpServer::HttpServer(const Config *config) : config_(config) {}

namespace {
int next_proto_cb(SSL *s, const unsigned char **data, unsigned int *len,
                  void *arg) {
  auto next_proto = static_cast<std::vector<unsigned char> *>(arg);
  *data = next_proto->data();
  *len = next_proto->size();
  return SSL_TLSEXT_ERR_OK;
}
} // namespace

namespace {
int verify_callback(int preverify_ok, X509_STORE_CTX *ctx) {
  // We don't verify the client certificate. Just request it for the
  // testing purpose.
  return 1;
}
} // namespace

namespace {
int start_listen(struct ev_loop *loop, Sessions *sessions,
                 const Config *config) {
  addrinfo hints;
  int r;
  bool ok = false;

  auto acceptor = std::make_shared<AcceptHandler>(sessions, config);
  auto service = util::utos(config->port);

  memset(&hints, 0, sizeof(addrinfo));
  hints.ai_family = AF_UNSPEC;
  hints.ai_socktype = SOCK_STREAM;
  hints.ai_flags = AI_PASSIVE;
#ifdef AI_ADDRCONFIG
  hints.ai_flags |= AI_ADDRCONFIG;
#endif // AI_ADDRCONFIG

  addrinfo *res, *rp;
  r = getaddrinfo(nullptr, service.c_str(), &hints, &res);
  if (r != 0) {
    std::cerr << "getaddrinfo() failed: " << gai_strerror(r) << std::endl;
    return -1;
  }
  for (rp = res; rp; rp = rp->ai_next) {
    int fd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
    if (fd == -1) {
      continue;
    }
    int val = 1;
    if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &val,
                   static_cast<socklen_t>(sizeof(val))) == -1) {
      close(fd);
      continue;
    }
    make_socket_nonblocking(fd);
#ifdef IPV6_V6ONLY
    if (rp->ai_family == AF_INET6) {
      if (setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &val,
                     static_cast<socklen_t>(sizeof(val))) == -1) {
        close(fd);
        continue;
      }
    }
#endif // IPV6_V6ONLY
    if (bind(fd, rp->ai_addr, rp->ai_addrlen) == 0 && listen(fd, 1000) == 0) {
      new ListenEventHandler(sessions, fd, acceptor);

      if (config->verbose) {
        std::cout << (rp->ai_family == AF_INET ? "IPv4" : "IPv6")
                  << ": listen on port " << config->port << std::endl;
      }
      ok = true;
      continue;
    } else {
      std::cerr << strerror(errno) << std::endl;
    }
    close(fd);
  }
  freeaddrinfo(res);

  if (!ok) {
    return -1;
  }
  return 0;
}
} // namespace

#if OPENSSL_VERSION_NUMBER >= 0x10002000L
namespace {
int alpn_select_proto_cb(SSL *ssl, const unsigned char **out,
                         unsigned char *outlen, const unsigned char *in,
                         unsigned int inlen, void *arg) {
  auto config = static_cast<HttpServer *>(arg)->get_config();
  if (config->verbose) {
    std::cout << "[ALPN] client offers:" << std::endl;
  }
  if (config->verbose) {
    for (unsigned int i = 0; i < inlen; i += in [i] + 1) {
      std::cout << " * ";
      std::cout.write(reinterpret_cast<const char *>(&in[i + 1]), in[i]);
      std::cout << std::endl;
    }
  }
  if (!util::select_h2(out, outlen, in, inlen)) {
    return SSL_TLSEXT_ERR_NOACK;
  }
  return SSL_TLSEXT_ERR_OK;
}
} // namespace
#endif // OPENSSL_VERSION_NUMBER >= 0x10002000L

int HttpServer::run() {
  SSL_CTX *ssl_ctx = nullptr;
  std::vector<unsigned char> next_proto;

  if (!config_->no_tls) {
    ssl_ctx = SSL_CTX_new(SSLv23_server_method());
    if (!ssl_ctx) {
      std::cerr << ERR_error_string(ERR_get_error(), nullptr) << std::endl;
      return -1;
    }

    SSL_CTX_set_options(ssl_ctx,
                        SSL_OP_ALL | SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3 |
                            SSL_OP_NO_COMPRESSION |
                            SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION |
                            SSL_OP_SINGLE_ECDH_USE | SSL_OP_NO_TICKET |
                            SSL_OP_CIPHER_SERVER_PREFERENCE);
    SSL_CTX_set_mode(ssl_ctx, SSL_MODE_AUTO_RETRY);
    SSL_CTX_set_mode(ssl_ctx, SSL_MODE_RELEASE_BUFFERS);

    SSL_CTX_set_cipher_list(ssl_ctx, ssl::DEFAULT_CIPHER_LIST);

    const unsigned char sid_ctx[] = "nghttpd";
    SSL_CTX_set_session_id_context(ssl_ctx, sid_ctx, sizeof(sid_ctx) - 1);
    SSL_CTX_set_session_cache_mode(ssl_ctx, SSL_SESS_CACHE_SERVER);

#ifndef OPENSSL_NO_EC

    // Disabled SSL_CTX_set_ecdh_auto, because computational cost of
    // chosen curve is much higher than P-256.

    // #if OPENSSL_VERSION_NUMBER >= 0x10002000L
    //     SSL_CTX_set_ecdh_auto(ssl_ctx, 1);
    // #else // OPENSSL_VERSION_NUBMER < 0x10002000L
    // Use P-256, which is sufficiently secure at the time of this
    // writing.
    auto ecdh = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1);
    if (ecdh == nullptr) {
      std::cerr << "EC_KEY_new_by_curv_name failed: "
                << ERR_error_string(ERR_get_error(), nullptr);
      return -1;
    }
    SSL_CTX_set_tmp_ecdh(ssl_ctx, ecdh);
    EC_KEY_free(ecdh);
// #endif // OPENSSL_VERSION_NUBMER < 0x10002000L

#endif // OPENSSL_NO_EC

    if (!config_->dh_param_file.empty()) {
      // Read DH parameters from file
      auto bio = BIO_new_file(config_->dh_param_file.c_str(), "r");
      if (bio == nullptr) {
        std::cerr << "BIO_new_file() failed: "
                  << ERR_error_string(ERR_get_error(), nullptr) << std::endl;
        return -1;
      }

      auto dh = PEM_read_bio_DHparams(bio, nullptr, nullptr, nullptr);

      if (dh == nullptr) {
        std::cerr << "PEM_read_bio_DHparams() failed: "
                  << ERR_error_string(ERR_get_error(), nullptr) << std::endl;
        return -1;
      }

      SSL_CTX_set_tmp_dh(ssl_ctx, dh);
      DH_free(dh);
      BIO_free(bio);
    }

    if (SSL_CTX_use_PrivateKey_file(ssl_ctx, config_->private_key_file.c_str(),
                                    SSL_FILETYPE_PEM) != 1) {
      std::cerr << "SSL_CTX_use_PrivateKey_file failed." << std::endl;
      return -1;
    }
    if (SSL_CTX_use_certificate_chain_file(ssl_ctx,
                                           config_->cert_file.c_str()) != 1) {
      std::cerr << "SSL_CTX_use_certificate_file failed." << std::endl;
      return -1;
    }
    if (SSL_CTX_check_private_key(ssl_ctx) != 1) {
      std::cerr << "SSL_CTX_check_private_key failed." << std::endl;
      return -1;
    }
    if (config_->verify_client) {
      SSL_CTX_set_verify(ssl_ctx, SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE |
                                      SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
                         verify_callback);
    }

    next_proto = util::get_default_alpn();

    SSL_CTX_set_next_protos_advertised_cb(ssl_ctx, next_proto_cb, &next_proto);
#if OPENSSL_VERSION_NUMBER >= 0x10002000L
    // ALPN selection callback
    SSL_CTX_set_alpn_select_cb(ssl_ctx, alpn_select_proto_cb, this);
#endif // OPENSSL_VERSION_NUMBER >= 0x10002000L
  }

  auto loop = EV_DEFAULT;

  Sessions sessions(loop, config_, ssl_ctx);
  if (start_listen(loop, &sessions, config_) != 0) {
    std::cerr << "Could not listen" << std::endl;
    return -1;
  }

  ev_timer refresh_wtc;
  ev_timer_init(&refresh_wtc, refresh_cb, 1.0, 0.);
  ev_timer_again(loop, &refresh_wtc);

  cached_date = std::make_shared<std::string>(util::http_date(time(nullptr)));

  ev_run(loop, 0);
  return 0;
}

const Config *HttpServer::get_config() const { return config_; }

} // namespace nghttp2