src/core/ext/transport/chttp2/server/chttp2_server.cc

   1 /*
   2  *
   3  * Copyright 2015 gRPC authors.
   4  *
   5  * Licensed under the Apache License, Version 2.0 (the "License");
   6  * you may not use this file except in compliance with the License.
   7  * You may obtain a copy of the License at
   8  *
   9  *     http://www.apache.org/licenses/LICENSE-2.0
  10  *
  11  * Unless required by applicable law or agreed to in writing, software
  12  * distributed under the License is distributed on an "AS IS" BASIS,
  13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14  * See the License for the specific language governing permissions and
  15  * limitations under the License.
  16  *
  17  */
  18
  19 #include <grpc/support/port_platform.h>
  20
  21 #include "src/core/ext/transport/chttp2/server/chttp2_server.h"
  22
  23 #include <inttypes.h>
  24 #include <limits.h>
  25 #include <string.h>
  26 #include <vector>
  27
  28 #include "absl/strings/match.h"
  29 #include "absl/strings/str_cat.h"
  30 #include "absl/strings/str_format.h"
  31
  32 #include <grpc/grpc.h>
  33 #include <grpc/impl/codegen/grpc_types.h>
  34 #include <grpc/support/alloc.h>
  35 #include <grpc/support/log.h>
  36 #include <grpc/support/sync.h>
  37
  38 #include "src/core/ext/filters/http/server/http_server_filter.h"
  39 #include "src/core/ext/transport/chttp2/transport/chttp2_transport.h"
  40 #include "src/core/ext/transport/chttp2/transport/internal.h"
  41 #include "src/core/lib/channel/channel_args.h"
  42 #include "src/core/lib/channel/handshaker.h"
  43 #include "src/core/lib/channel/handshaker_registry.h"
  44 #include "src/core/lib/gprpp/ref_counted.h"
  45 #include "src/core/lib/gprpp/ref_counted_ptr.h"
  46 #include "src/core/lib/iomgr/endpoint.h"
  47 #include "src/core/lib/iomgr/resolve_address.h"
  48 #include "src/core/lib/iomgr/resource_quota.h"
  49 #include "src/core/lib/iomgr/sockaddr_utils.h"
  50 #include "src/core/lib/iomgr/tcp_server.h"
  51 #include "src/core/lib/iomgr/unix_sockets_posix.h"
  52 #include "src/core/lib/slice/slice_internal.h"
  53 #include "src/core/lib/surface/api_trace.h"
  54 #include "src/core/lib/surface/server.h"
  55
  56 namespace grpc_core {
  57 namespace {
  58
  59 const char kUnixUriPrefix[] = "unix:";
  60 const char kUnixAbstractUriPrefix[] = "unix-abstract:";
  61
  62 class Chttp2ServerListener : public Server::ListenerInterface {
  63  public:
  64   static grpc_error* Create(Server* server, grpc_resolved_address* addr,
  65                             grpc_channel_args* args, int* port_num);
  66
  67   static grpc_error* CreateWithAcceptor(Server* server, const char* name,
  68                                         grpc_channel_args* args);
  69
  70   // Do not instantiate directly.  Use one of the factory methods above.
  71   Chttp2ServerListener(Server* server, grpc_channel_args* args);
  72   ~Chttp2ServerListener() override;
  73
  74   void Start(Server* server,
  75              const std::vector<grpc_pollset*>* pollsets) override;
  76
  77   channelz::ListenSocketNode* channelz_listen_socket_node() const override {
  78     return channelz_listen_socket_.get();
  79   }
  80
  81   void SetOnDestroyDone(grpc_closure* on_destroy_done) override;
  82
  83   void Orphan() override;
  84
  85  private:
  86   class ConfigFetcherWatcher
  87       : public grpc_server_config_fetcher::WatcherInterface {
  88    public:
  89     explicit ConfigFetcherWatcher(Chttp2ServerListener* listener)
  90         : listener_(listener) {}
  91
  92     void UpdateConfig(grpc_channel_args* args) override {
  93       {
  94         MutexLock lock(&listener_->mu_);
  95         // TODO(yashykt): Fix this
  96         // grpc_channel_args_destroy(listener_->args_);
  97         // listener_->args_ = args;
  98         if (!listener_->shutdown_) return;  // Already started listening.
  99       }
 100       int port_temp;
 101       grpc_error* error = grpc_tcp_server_add_port(
 102           listener_->tcp_server_, &listener_->resolved_address_, &port_temp);
 103       if (error != GRPC_ERROR_NONE) {
 104         GRPC_ERROR_UNREF(error);
 105         gpr_log(GPR_ERROR, "Error adding port to server: %s",
 106                 grpc_error_string(error));
 107         // TODO(yashykt): We wouldn't need to assert here if we bound to the
 108         // port earlier during AddPort.
 109         GPR_ASSERT(0);
 110       }
 111       listener_->StartListening();
 112     }
 113
 114    private:
 115     Chttp2ServerListener* listener_;
 116   };
 117
 118   class ConnectionState : public RefCounted<ConnectionState> {
 119    public:
 120     ConnectionState(Chttp2ServerListener* listener,
 121                     grpc_pollset* accepting_pollset,
 122                     grpc_tcp_server_acceptor* acceptor,
 123                     RefCountedPtr<HandshakeManager> handshake_mgr,
 124                     grpc_channel_args* args, grpc_endpoint* endpoint);
 125
 126     ~ConnectionState() override;
 127
 128    private:
 129     static void OnTimeout(void* arg, grpc_error* error);
 130     static void OnReceiveSettings(void* arg, grpc_error* error);
 131     static void OnHandshakeDone(void* arg, grpc_error* error);
 132
 133     Chttp2ServerListener* const listener_;
 134     grpc_pollset* const accepting_pollset_;
 135     grpc_tcp_server_acceptor* const acceptor_;
 136     RefCountedPtr<HandshakeManager> handshake_mgr_;
 137     // State for enforcing handshake timeout on receiving HTTP/2 settings.
 138     grpc_chttp2_transport* transport_ = nullptr;
 139     grpc_millis deadline_;
 140     grpc_timer timer_;
 141     grpc_closure on_timeout_;
 142     grpc_closure on_receive_settings_;
 143     grpc_pollset_set* const interested_parties_;
 144   };
 145
 146   void StartListening();
 147
 148   static void OnAccept(void* arg, grpc_endpoint* tcp,
 149                        grpc_pollset* accepting_pollset,
 150                        grpc_tcp_server_acceptor* acceptor);
 151
 152   RefCountedPtr<HandshakeManager> CreateHandshakeManager();
 153
 154   static void TcpServerShutdownComplete(void* arg, grpc_error* error);
 155
 156   static void DestroyListener(Server* /*server*/, void* arg,
 157                               grpc_closure* destroy_done);
 158
 159   Server* const server_;
 160   grpc_channel_args* const args_;
 161   grpc_tcp_server* tcp_server_;
 162   grpc_resolved_address resolved_address_;
 163   Mutex mu_;
 164   ConfigFetcherWatcher* config_fetcher_watcher_ = nullptr;
 165   bool shutdown_ = true;
 166   grpc_closure tcp_server_shutdown_complete_;
 167   grpc_closure* on_destroy_done_ = nullptr;
 168   HandshakeManager* pending_handshake_mgrs_ = nullptr;
 169   RefCountedPtr<channelz::ListenSocketNode> channelz_listen_socket_;
 170 };
 171
 172 //
 173 // Chttp2ServerListener::ConnectionState
 174 //
 175
 176 grpc_millis GetConnectionDeadline(const grpc_channel_args* args) {
 177   int timeout_ms =
 178       grpc_channel_args_find_integer(args, GRPC_ARG_SERVER_HANDSHAKE_TIMEOUT_MS,
 179                                      {120 * GPR_MS_PER_SEC, 1, INT_MAX});
 180   return ExecCtx::Get()->Now() + timeout_ms;
 181 }
 182
 183 Chttp2ServerListener::ConnectionState::ConnectionState(
 184     Chttp2ServerListener* listener, grpc_pollset* accepting_pollset,
 185     grpc_tcp_server_acceptor* acceptor,
 186     RefCountedPtr<HandshakeManager> handshake_mgr, grpc_channel_args* args,
 187     grpc_endpoint* endpoint)
 188     : listener_(listener),
 189       accepting_pollset_(accepting_pollset),
 190       acceptor_(acceptor),
 191       handshake_mgr_(std::move(handshake_mgr)),
 192       deadline_(GetConnectionDeadline(args)),
 193       interested_parties_(grpc_pollset_set_create()) {
 194   grpc_pollset_set_add_pollset(interested_parties_, accepting_pollset_);
 195   HandshakerRegistry::AddHandshakers(HANDSHAKER_SERVER, args,
 196                                      interested_parties_, handshake_mgr_.get());
 197   handshake_mgr_->DoHandshake(endpoint, args, deadline_, acceptor_,
 198                               OnHandshakeDone, this);
 199 }
 200
 201 Chttp2ServerListener::ConnectionState::~ConnectionState() {
 202   if (transport_ != nullptr) {
 203     GRPC_CHTTP2_UNREF_TRANSPORT(transport_, "receive settings timeout");
 204   }
 205   grpc_pollset_set_del_pollset(interested_parties_, accepting_pollset_);
 206   grpc_pollset_set_destroy(interested_parties_);
 207 }
 208
 209 void Chttp2ServerListener::ConnectionState::OnTimeout(void* arg,
 210                                                       grpc_error* error) {
 211   ConnectionState* self = static_cast<ConnectionState*>(arg);
 212   // Note that we may be called with GRPC_ERROR_NONE when the timer fires
 213   // or with an error indicating that the timer system is being shut down.
 214   if (error != GRPC_ERROR_CANCELLED) {
 215     grpc_transport_op* op = grpc_make_transport_op(nullptr);
 216     op->disconnect_with_error = GRPC_ERROR_CREATE_FROM_STATIC_STRING(
 217         "Did not receive HTTP/2 settings before handshake timeout");
 218     grpc_transport_perform_op(&self->transport_->base, op);
 219   }
 220   self->Unref();
 221 }
 222
 223 void Chttp2ServerListener::ConnectionState::OnReceiveSettings(
 224     void* arg, grpc_error* error) {
 225   ConnectionState* self = static_cast<ConnectionState*>(arg);
 226   if (error == GRPC_ERROR_NONE) {
 227     grpc_timer_cancel(&self->timer_);
 228   }
 229   self->Unref();
 230 }
 231
 232 void Chttp2ServerListener::ConnectionState::OnHandshakeDone(void* arg,
 233                                                             grpc_error* error) {
 234   auto* args = static_cast<HandshakerArgs*>(arg);
 235   ConnectionState* self = static_cast<ConnectionState*>(args->user_data);
 236   {
 237     MutexLock lock(&self->listener_->mu_);
 238     grpc_resource_user* resource_user =
 239         self->listener_->server_->default_resource_user();
 240     if (error != GRPC_ERROR_NONE || self->listener_->shutdown_) {
 241       const char* error_str = grpc_error_string(error);
 242       gpr_log(GPR_DEBUG, "Handshaking failed: %s", error_str);
 243       if (resource_user != nullptr) {
 244         grpc_resource_user_free(resource_user,
 245                                 GRPC_RESOURCE_QUOTA_CHANNEL_SIZE);
 246       }
 247       if (error == GRPC_ERROR_NONE && args->endpoint != nullptr) {
 248         // We were shut down after handshaking completed successfully, so
 249         // destroy the endpoint here.
 250         // TODO(ctiller): It is currently necessary to shutdown endpoints
 251         // before destroying them, even if we know that there are no
 252         // pending read/write callbacks.  This should be fixed, at which
 253         // point this can be removed.
 254         grpc_endpoint_shutdown(args->endpoint, GRPC_ERROR_NONE);
 255         grpc_endpoint_destroy(args->endpoint);
 256         grpc_channel_args_destroy(args->args);
 257         grpc_slice_buffer_destroy_internal(args->read_buffer);
 258         gpr_free(args->read_buffer);
 259       }
 260     } else {
 261       // If the handshaking succeeded but there is no endpoint, then the
 262       // handshaker may have handed off the connection to some external
 263       // code, so we can just clean up here without creating a transport.
 264       if (args->endpoint != nullptr) {
 265         grpc_transport* transport = grpc_create_chttp2_transport(
 266             args->args, args->endpoint, false, resource_user);
 267         grpc_error* channel_init_err = self->listener_->server_->SetupTransport(
 268             transport, self->accepting_pollset_, args->args,
 269             grpc_chttp2_transport_get_socket_node(transport), resource_user);
 270         if (channel_init_err == GRPC_ERROR_NONE) {
 271           // Use notify_on_receive_settings callback to enforce the
 272           // handshake deadline.
 273           // Note: The reinterpret_cast<>s here are safe, because
 274           // grpc_chttp2_transport is a C-style extension of
 275           // grpc_transport, so this is morally equivalent of a
 276           // static_cast<> to a derived class.
 277           // TODO(roth): Change to static_cast<> when we C++-ify the
 278           // transport API.
 279           self->transport_ =
 280               reinterpret_cast<grpc_chttp2_transport*>(transport);
 281           self->Ref().release();  // Held by OnReceiveSettings().
 282           GRPC_CLOSURE_INIT(&self->on_receive_settings_, OnReceiveSettings,
 283                             self, grpc_schedule_on_exec_ctx);
 284           grpc_chttp2_transport_start_reading(transport, args->read_buffer,
 285                                               &self->on_receive_settings_);
 286           grpc_channel_args_destroy(args->args);
 287           self->Ref().release();  // Held by OnTimeout().
 288           GRPC_CHTTP2_REF_TRANSPORT(
 289               reinterpret_cast<grpc_chttp2_transport*>(transport),
 290               "receive settings timeout");
 291           GRPC_CLOSURE_INIT(&self->on_timeout_, OnTimeout, self,
 292                             grpc_schedule_on_exec_ctx);
 293           grpc_timer_init(&self->timer_, self->deadline_, &self->on_timeout_);
 294         } else {
 295           // Failed to create channel from transport. Clean up.
 296           gpr_log(GPR_ERROR, "Failed to create channel: %s",
 297                   grpc_error_string(channel_init_err));
 298           GRPC_ERROR_UNREF(channel_init_err);
 299           grpc_transport_destroy(transport);
 300           grpc_slice_buffer_destroy_internal(args->read_buffer);
 301           gpr_free(args->read_buffer);
 302           if (resource_user != nullptr) {
 303             grpc_resource_user_free(resource_user,
 304                                     GRPC_RESOURCE_QUOTA_CHANNEL_SIZE);
 305           }
 306           grpc_channel_args_destroy(args->args);
 307         }
 308       } else {
 309         if (resource_user != nullptr) {
 310           grpc_resource_user_free(resource_user,
 311                                   GRPC_RESOURCE_QUOTA_CHANNEL_SIZE);
 312         }
 313       }
 314     }
 315     self->handshake_mgr_->RemoveFromPendingMgrList(
 316         &self->listener_->pending_handshake_mgrs_);
 317   }
 318   self->handshake_mgr_.reset();
 319   gpr_free(self->acceptor_);
 320   grpc_tcp_server_unref(self->listener_->tcp_server_);
 321   self->Unref();
 322 }
 323
 324 //
 325 // Chttp2ServerListener
 326 //
 327
 328 grpc_error* Chttp2ServerListener::Create(Server* server,
 329                                          grpc_resolved_address* addr,
 330                                          grpc_channel_args* args,
 331                                          int* port_num) {
 332   Chttp2ServerListener* listener = nullptr;
 333   // The bulk of this method is inside of a lambda to make cleanup
 334   // easier without using goto.
 335   grpc_error* error = [&]() {
 336     // Create Chttp2ServerListener.
 337     listener = new Chttp2ServerListener(server, args);
 338     error = grpc_tcp_server_create(&listener->tcp_server_shutdown_complete_,
 339                                    args, &listener->tcp_server_);
 340     if (error != GRPC_ERROR_NONE) return error;
 341     if (server->config_fetcher() != nullptr) {
 342       listener->resolved_address_ = *addr;
 343       // TODO(yashykt): Consider binding so as to be able to return the port
 344       // number.
 345     } else {
 346       error = grpc_tcp_server_add_port(listener->tcp_server_, addr, port_num);
 347       if (error != GRPC_ERROR_NONE) return error;
 348     }
 349     // Create channelz node.
 350     if (grpc_channel_args_find_bool(args, GRPC_ARG_ENABLE_CHANNELZ,
 351                                     GRPC_ENABLE_CHANNELZ_DEFAULT)) {
 352       std::string string_address = grpc_sockaddr_to_string(addr, false);
 353       listener->channelz_listen_socket_ =
 354           MakeRefCounted<channelz::ListenSocketNode>(
 355               string_address.c_str(),
 356               absl::StrFormat("chttp2 listener %s", string_address.c_str()));
 357     }
 358     // Register with the server only upon success
 359     server->AddListener(OrphanablePtr<Server::ListenerInterface>(listener));
 360     return GRPC_ERROR_NONE;
 361   }();
 362   if (error != GRPC_ERROR_NONE) {
 363     if (listener != nullptr) {
 364       if (listener->tcp_server_ != nullptr) {
 365         // listener is deleted when tcp_server_ is shutdown.
 366         grpc_tcp_server_unref(listener->tcp_server_);
 367       } else {
 368         delete listener;
 369       }
 370     } else {
 371       grpc_channel_args_destroy(args);
 372     }
 373   }
 374   return error;
 375 }
 376
 377 grpc_error* Chttp2ServerListener::CreateWithAcceptor(Server* server,
 378                                                      const char* name,
 379                                                      grpc_channel_args* args) {
 380   Chttp2ServerListener* listener = new Chttp2ServerListener(server, args);
 381   grpc_error* error = grpc_tcp_server_create(
 382       &listener->tcp_server_shutdown_complete_, args, &listener->tcp_server_);
 383   if (error != GRPC_ERROR_NONE) {
 384     delete listener;
 385     return error;
 386   }
 387   // TODO(yangg) channelz
 388   TcpServerFdHandler** arg_val =
 389       grpc_channel_args_find_pointer<TcpServerFdHandler*>(args, name);
 390   *arg_val = grpc_tcp_server_create_fd_handler(listener->tcp_server_);
 391   server->AddListener(OrphanablePtr<Server::ListenerInterface>(listener));
 392   return GRPC_ERROR_NONE;
 393 }
 394
 395 Chttp2ServerListener::Chttp2ServerListener(Server* server,
 396                                            grpc_channel_args* args)
 397     : server_(server), args_(args) {
 398   GRPC_CLOSURE_INIT(&tcp_server_shutdown_complete_, TcpServerShutdownComplete,
 399                     this, grpc_schedule_on_exec_ctx);
 400 }
 401
 402 Chttp2ServerListener::~Chttp2ServerListener() {
 403   grpc_channel_args_destroy(args_);
 404 }
 405
 406 /* Server callback: start listening on our ports */
 407 void Chttp2ServerListener::Start(
 408     Server* /*server*/, const std::vector<grpc_pollset*>* /* pollsets */) {
 409   if (server_->config_fetcher() != nullptr) {
 410     auto watcher = absl::make_unique<ConfigFetcherWatcher>(this);
 411     {
 412       MutexLock lock(&mu_);
 413       config_fetcher_watcher_ = watcher.get();
 414     }
 415     server_->config_fetcher()->StartWatch(
 416         grpc_sockaddr_to_string(&resolved_address_, false), std::move(watcher));
 417   } else {
 418     StartListening();
 419   }
 420 }
 421
 422 void Chttp2ServerListener::StartListening() {
 423   grpc_tcp_server_start(tcp_server_, &server_->pollsets(), OnAccept, this);
 424   MutexLock lock(&mu_);
 425   shutdown_ = false;
 426 }
 427
 428 void Chttp2ServerListener::SetOnDestroyDone(grpc_closure* on_destroy_done) {
 429   MutexLock lock(&mu_);
 430   on_destroy_done_ = on_destroy_done;
 431 }
 432
 433 RefCountedPtr<HandshakeManager> Chttp2ServerListener::CreateHandshakeManager() {
 434   MutexLock lock(&mu_);
 435   if (shutdown_) return nullptr;
 436   grpc_resource_user* resource_user = server_->default_resource_user();
 437   if (resource_user != nullptr &&
 438       !grpc_resource_user_safe_alloc(resource_user,
 439                                      GRPC_RESOURCE_QUOTA_CHANNEL_SIZE)) {
 440     gpr_log(GPR_ERROR,
 441             "Memory quota exhausted, rejecting connection, no handshaking.");
 442     return nullptr;
 443   }
 444   auto handshake_mgr = MakeRefCounted<HandshakeManager>();
 445   handshake_mgr->AddToPendingMgrList(&pending_handshake_mgrs_);
 446   grpc_tcp_server_ref(tcp_server_);  // Ref held by ConnectionState.
 447   return handshake_mgr;
 448 }
 449
 450 void Chttp2ServerListener::OnAccept(void* arg, grpc_endpoint* tcp,
 451                                     grpc_pollset* accepting_pollset,
 452                                     grpc_tcp_server_acceptor* acceptor) {
 453   Chttp2ServerListener* self = static_cast<Chttp2ServerListener*>(arg);
 454   RefCountedPtr<HandshakeManager> handshake_mgr =
 455       self->CreateHandshakeManager();
 456   if (handshake_mgr == nullptr) {
 457     grpc_endpoint_shutdown(tcp, GRPC_ERROR_NONE);
 458     grpc_endpoint_destroy(tcp);
 459     gpr_free(acceptor);
 460     return;
 461   }
 462   // Deletes itself when done.
 463   new ConnectionState(self, accepting_pollset, acceptor,
 464                       std::move(handshake_mgr), self->args_, tcp);
 465 }
 466
 467 void Chttp2ServerListener::TcpServerShutdownComplete(void* arg,
 468                                                      grpc_error* error) {
 469   Chttp2ServerListener* self = static_cast<Chttp2ServerListener*>(arg);
 470   /* ensure all threads have unlocked */
 471   grpc_closure* destroy_done = nullptr;
 472   {
 473     MutexLock lock(&self->mu_);
 474     destroy_done = self->on_destroy_done_;
 475     GPR_ASSERT(self->shutdown_);
 476     if (self->pending_handshake_mgrs_ != nullptr) {
 477       self->pending_handshake_mgrs_->ShutdownAllPending(GRPC_ERROR_REF(error));
 478     }
 479     self->channelz_listen_socket_.reset();
 480   }
 481   // Flush queued work before destroying handshaker factory, since that
 482   // may do a synchronous unref.
 483   ExecCtx::Get()->Flush();
 484   if (destroy_done != nullptr) {
 485     ExecCtx::Run(DEBUG_LOCATION, destroy_done, GRPC_ERROR_REF(error));
 486     ExecCtx::Get()->Flush();
 487   }
 488   delete self;
 489 }
 490
 491 /* Server callback: destroy the tcp listener (so we don't generate further
 492    callbacks) */
 493 void Chttp2ServerListener::Orphan() {
 494   // Cancel the watch before shutting down so as to avoid holding a ref to the
 495   // listener in the watcher.
 496   if (config_fetcher_watcher_ != nullptr) {
 497     server_->config_fetcher()->CancelWatch(config_fetcher_watcher_);
 498   }
 499   grpc_tcp_server* tcp_server;
 500   {
 501     MutexLock lock(&mu_);
 502     shutdown_ = true;
 503     tcp_server = tcp_server_;
 504   }
 505   grpc_tcp_server_shutdown_listeners(tcp_server);
 506   grpc_tcp_server_unref(tcp_server);
 507 }
 508
 509 }  // namespace
 510
 511 //
 512 // Chttp2ServerAddPort()
 513 //
 514
 515 grpc_error* Chttp2ServerAddPort(Server* server, const char* addr,
 516                                 grpc_channel_args* args, int* port_num) {
 517   if (strncmp(addr, "external:", 9) == 0) {
 518     return grpc_core::Chttp2ServerListener::CreateWithAcceptor(server, addr,
 519                                                                args);
 520   }
 521   *port_num = -1;
 522   grpc_resolved_addresses* resolved = nullptr;
 523   std::vector<grpc_error*> error_list;
 524   // Using lambda to avoid use of goto.
 525   grpc_error* error = [&]() {
 526     if (absl::StartsWith(addr, kUnixUriPrefix)) {
 527       error = grpc_resolve_unix_domain_address(
 528           addr + sizeof(kUnixUriPrefix) - 1, &resolved);
 529     } else if (absl::StartsWith(addr, kUnixAbstractUriPrefix)) {
 530       error = grpc_resolve_unix_abstract_domain_address(
 531           addr + sizeof(kUnixAbstractUriPrefix) - 1, &resolved);
 532     } else {
 533       error = grpc_blocking_resolve_address(addr, "https", &resolved);
 534     }
 535     if (error != GRPC_ERROR_NONE) return error;
 536     // Create a listener for each resolved address.
 537     for (size_t i = 0; i < resolved->naddrs; i++) {
 538       // If address has a wildcard port (0), use the same port as a previous
 539       // listener.
 540       if (*port_num != -1 && grpc_sockaddr_get_port(&resolved->addrs[i]) == 0) {
 541         grpc_sockaddr_set_port(&resolved->addrs[i], *port_num);
 542       }
 543       int port_temp;
 544       error = grpc_core::Chttp2ServerListener::Create(
 545           server, &resolved->addrs[i], grpc_channel_args_copy(args),
 546           &port_temp);
 547       if (error != GRPC_ERROR_NONE) {
 548         error_list.push_back(error);
 549       } else {
 550         if (*port_num == -1) {
 551           *port_num = port_temp;
 552         } else {
 553           GPR_ASSERT(*port_num == port_temp);
 554         }
 555       }
 556     }
 557     if (error_list.size() == resolved->naddrs) {
 558       std::string msg =
 559           absl::StrFormat("No address added out of total %" PRIuPTR " resolved",
 560                           resolved->naddrs);
 561       return GRPC_ERROR_CREATE_REFERENCING_FROM_COPIED_STRING(
 562           msg.c_str(), error_list.data(), error_list.size());
 563     } else if (!error_list.empty()) {
 564       std::string msg = absl::StrFormat(
 565           "Only %" PRIuPTR " addresses added out of total %" PRIuPTR
 566           " resolved",
 567           resolved->naddrs - error_list.size(), resolved->naddrs);
 568       error = GRPC_ERROR_CREATE_REFERENCING_FROM_COPIED_STRING(
 569           msg.c_str(), error_list.data(), error_list.size());
 570       gpr_log(GPR_INFO, "WARNING: %s", grpc_error_string(error));
 571       GRPC_ERROR_UNREF(error);
 572       // we managed to bind some addresses: continue without error
 573     }
 574     return GRPC_ERROR_NONE;
 575   }();  // lambda end
 576   for (grpc_error* error : error_list) {
 577     GRPC_ERROR_UNREF(error);
 578   }
 579   grpc_channel_args_destroy(args);
 580   if (resolved != nullptr) {
 581     grpc_resolved_addresses_destroy(resolved);
 582   }
 583   if (error != GRPC_ERROR_NONE) *port_num = 0;
 584   return error;
 585 }
 586
 587 }  // namespace grpc_core