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,
  66                             Chttp2ServerArgsModifier args_modifier,
  67                             int* port_num);
  68
  69   static grpc_error* CreateWithAcceptor(Server* server, const char* name,
  70                                         grpc_channel_args* args,
  71                                         Chttp2ServerArgsModifier args_modifier);
  72
  73   // Do not instantiate directly.  Use one of the factory methods above.
  74   Chttp2ServerListener(Server* server, grpc_channel_args* args,
  75                        Chttp2ServerArgsModifier args_modifier);
  76   ~Chttp2ServerListener() override;
  77
  78   void Start(Server* server,
  79              const std::vector<grpc_pollset*>* pollsets) override;
  80
  81   channelz::ListenSocketNode* channelz_listen_socket_node() const override {
  82     return channelz_listen_socket_.get();
  83   }
  84
  85   void SetOnDestroyDone(grpc_closure* on_destroy_done) override;
  86
  87   void Orphan() override;
  88
  89  private:
  90   class ConfigFetcherWatcher
  91       : public grpc_server_config_fetcher::WatcherInterface {
  92    public:
  93     explicit ConfigFetcherWatcher(Chttp2ServerListener* listener)
  94         : listener_(listener) {}
  95
  96     void UpdateConfig(grpc_channel_args* args) override {
  97       {
  98         MutexLock lock(&listener_->mu_);
  99         grpc_channel_args_destroy(listener_->args_);
 100         grpc_error* error = GRPC_ERROR_NONE;
 101         args = listener_->args_modifier_(args, &error);
 102         if (error != GRPC_ERROR_NONE) {
 103           // TODO(yashykt): Set state to close down connections immediately
 104           // after accepting.
 105           GPR_ASSERT(0);
 106         }
 107         listener_->args_ = args;
 108         if (!listener_->shutdown_) return;  // Already started listening.
 109       }
 110       int port_temp;
 111       grpc_error* error = grpc_tcp_server_add_port(
 112           listener_->tcp_server_, &listener_->resolved_address_, &port_temp);
 113       if (error != GRPC_ERROR_NONE) {
 114         GRPC_ERROR_UNREF(error);
 115         gpr_log(GPR_ERROR, "Error adding port to server: %s",
 116                 grpc_error_string(error));
 117         // TODO(yashykt): We wouldn't need to assert here if we bound to the
 118         // port earlier during AddPort.
 119         GPR_ASSERT(0);
 120       }
 121       listener_->StartListening();
 122     }
 123
 124    private:
 125     Chttp2ServerListener* listener_;
 126   };
 127
 128   class ConnectionState : public RefCounted<ConnectionState> {
 129    public:
 130     ConnectionState(Chttp2ServerListener* listener,
 131                     grpc_pollset* accepting_pollset,
 132                     grpc_tcp_server_acceptor* acceptor,
 133                     RefCountedPtr<HandshakeManager> handshake_mgr,
 134                     grpc_channel_args* args, grpc_endpoint* endpoint);
 135
 136     ~ConnectionState() override;
 137
 138    private:
 139     static void OnTimeout(void* arg, grpc_error* error);
 140     static void OnReceiveSettings(void* arg, grpc_error* error);
 141     static void OnHandshakeDone(void* arg, grpc_error* error);
 142
 143     Chttp2ServerListener* const listener_;
 144     grpc_pollset* const accepting_pollset_;
 145     grpc_tcp_server_acceptor* const acceptor_;
 146     RefCountedPtr<HandshakeManager> handshake_mgr_;
 147     // State for enforcing handshake timeout on receiving HTTP/2 settings.
 148     grpc_chttp2_transport* transport_ = nullptr;
 149     grpc_millis deadline_;
 150     grpc_timer timer_;
 151     grpc_closure on_timeout_;
 152     grpc_closure on_receive_settings_;
 153     grpc_pollset_set* const interested_parties_;
 154   };
 155
 156   void StartListening();
 157
 158   static void OnAccept(void* arg, grpc_endpoint* tcp,
 159                        grpc_pollset* accepting_pollset,
 160                        grpc_tcp_server_acceptor* acceptor);
 161
 162   RefCountedPtr<HandshakeManager> CreateHandshakeManager();
 163
 164   static void TcpServerShutdownComplete(void* arg, grpc_error* error);
 165
 166   static void DestroyListener(Server* /*server*/, void* arg,
 167                               grpc_closure* destroy_done);
 168
 169   Server* const server_;
 170   grpc_tcp_server* tcp_server_;
 171   grpc_resolved_address resolved_address_;
 172   Chttp2ServerArgsModifier args_modifier_;
 173   Mutex mu_;
 174   grpc_channel_args* args_;  // guarded by mu_
 175   ConfigFetcherWatcher* config_fetcher_watcher_ = nullptr;
 176   bool shutdown_ = true;
 177   grpc_closure tcp_server_shutdown_complete_;
 178   grpc_closure* on_destroy_done_ = nullptr;
 179   HandshakeManager* pending_handshake_mgrs_ = nullptr;
 180   RefCountedPtr<channelz::ListenSocketNode> channelz_listen_socket_;
 181 };
 182
 183 //
 184 // Chttp2ServerListener::ConnectionState
 185 //
 186
 187 grpc_millis GetConnectionDeadline(const grpc_channel_args* args) {
 188   int timeout_ms =
 189       grpc_channel_args_find_integer(args, GRPC_ARG_SERVER_HANDSHAKE_TIMEOUT_MS,
 190                                      {120 * GPR_MS_PER_SEC, 1, INT_MAX});
 191   return ExecCtx::Get()->Now() + timeout_ms;
 192 }
 193
 194 Chttp2ServerListener::ConnectionState::ConnectionState(
 195     Chttp2ServerListener* listener, grpc_pollset* accepting_pollset,
 196     grpc_tcp_server_acceptor* acceptor,
 197     RefCountedPtr<HandshakeManager> handshake_mgr, grpc_channel_args* args,
 198     grpc_endpoint* endpoint)
 199     : listener_(listener),
 200       accepting_pollset_(accepting_pollset),
 201       acceptor_(acceptor),
 202       handshake_mgr_(std::move(handshake_mgr)),
 203       deadline_(GetConnectionDeadline(args)),
 204       interested_parties_(grpc_pollset_set_create()) {
 205   grpc_pollset_set_add_pollset(interested_parties_, accepting_pollset_);
 206   HandshakerRegistry::AddHandshakers(HANDSHAKER_SERVER, args,
 207                                      interested_parties_, handshake_mgr_.get());
 208   handshake_mgr_->DoHandshake(endpoint, args, deadline_, acceptor_,
 209                               OnHandshakeDone, this);
 210 }
 211
 212 Chttp2ServerListener::ConnectionState::~ConnectionState() {
 213   if (transport_ != nullptr) {
 214     GRPC_CHTTP2_UNREF_TRANSPORT(transport_, "receive settings timeout");
 215   }
 216   grpc_pollset_set_del_pollset(interested_parties_, accepting_pollset_);
 217   grpc_pollset_set_destroy(interested_parties_);
 218 }
 219
 220 void Chttp2ServerListener::ConnectionState::OnTimeout(void* arg,
 221                                                       grpc_error* error) {
 222   ConnectionState* self = static_cast<ConnectionState*>(arg);
 223   // Note that we may be called with GRPC_ERROR_NONE when the timer fires
 224   // or with an error indicating that the timer system is being shut down.
 225   if (error != GRPC_ERROR_CANCELLED) {
 226     grpc_transport_op* op = grpc_make_transport_op(nullptr);
 227     op->disconnect_with_error = GRPC_ERROR_CREATE_FROM_STATIC_STRING(
 228         "Did not receive HTTP/2 settings before handshake timeout");
 229     grpc_transport_perform_op(&self->transport_->base, op);
 230   }
 231   self->Unref();
 232 }
 233
 234 void Chttp2ServerListener::ConnectionState::OnReceiveSettings(
 235     void* arg, grpc_error* error) {
 236   ConnectionState* self = static_cast<ConnectionState*>(arg);
 237   if (error == GRPC_ERROR_NONE) {
 238     grpc_timer_cancel(&self->timer_);
 239   }
 240   self->Unref();
 241 }
 242
 243 void Chttp2ServerListener::ConnectionState::OnHandshakeDone(void* arg,
 244                                                             grpc_error* error) {
 245   auto* args = static_cast<HandshakerArgs*>(arg);
 246   ConnectionState* self = static_cast<ConnectionState*>(args->user_data);
 247   {
 248     MutexLock lock(&self->listener_->mu_);
 249     grpc_resource_user* resource_user =
 250         self->listener_->server_->default_resource_user();
 251     if (error != GRPC_ERROR_NONE || self->listener_->shutdown_) {
 252       const char* error_str = grpc_error_string(error);
 253       gpr_log(GPR_DEBUG, "Handshaking failed: %s", error_str);
 254       if (resource_user != nullptr) {
 255         grpc_resource_user_free(resource_user,
 256                                 GRPC_RESOURCE_QUOTA_CHANNEL_SIZE);
 257       }
 258       if (error == GRPC_ERROR_NONE && args->endpoint != nullptr) {
 259         // We were shut down after handshaking completed successfully, so
 260         // destroy the endpoint here.
 261         // TODO(ctiller): It is currently necessary to shutdown endpoints
 262         // before destroying them, even if we know that there are no
 263         // pending read/write callbacks.  This should be fixed, at which
 264         // point this can be removed.
 265         grpc_endpoint_shutdown(args->endpoint, GRPC_ERROR_NONE);
 266         grpc_endpoint_destroy(args->endpoint);
 267         grpc_channel_args_destroy(args->args);
 268         grpc_slice_buffer_destroy_internal(args->read_buffer);
 269         gpr_free(args->read_buffer);
 270       }
 271     } else {
 272       // If the handshaking succeeded but there is no endpoint, then the
 273       // handshaker may have handed off the connection to some external
 274       // code, so we can just clean up here without creating a transport.
 275       if (args->endpoint != nullptr) {
 276         grpc_transport* transport = grpc_create_chttp2_transport(
 277             args->args, args->endpoint, false, resource_user);
 278         grpc_error* channel_init_err = self->listener_->server_->SetupTransport(
 279             transport, self->accepting_pollset_, args->args,
 280             grpc_chttp2_transport_get_socket_node(transport), resource_user);
 281         if (channel_init_err == GRPC_ERROR_NONE) {
 282           // Use notify_on_receive_settings callback to enforce the
 283           // handshake deadline.
 284           // Note: The reinterpret_cast<>s here are safe, because
 285           // grpc_chttp2_transport is a C-style extension of
 286           // grpc_transport, so this is morally equivalent of a
 287           // static_cast<> to a derived class.
 288           // TODO(roth): Change to static_cast<> when we C++-ify the
 289           // transport API.
 290           self->transport_ =
 291               reinterpret_cast<grpc_chttp2_transport*>(transport);
 292           self->Ref().release();  // Held by OnReceiveSettings().
 293           GRPC_CLOSURE_INIT(&self->on_receive_settings_, OnReceiveSettings,
 294                             self, grpc_schedule_on_exec_ctx);
 295           grpc_chttp2_transport_start_reading(transport, args->read_buffer,
 296                                               &self->on_receive_settings_);
 297           grpc_channel_args_destroy(args->args);
 298           self->Ref().release();  // Held by OnTimeout().
 299           GRPC_CHTTP2_REF_TRANSPORT(
 300               reinterpret_cast<grpc_chttp2_transport*>(transport),
 301               "receive settings timeout");
 302           GRPC_CLOSURE_INIT(&self->on_timeout_, OnTimeout, self,
 303                             grpc_schedule_on_exec_ctx);
 304           grpc_timer_init(&self->timer_, self->deadline_, &self->on_timeout_);
 305         } else {
 306           // Failed to create channel from transport. Clean up.
 307           gpr_log(GPR_ERROR, "Failed to create channel: %s",
 308                   grpc_error_string(channel_init_err));
 309           GRPC_ERROR_UNREF(channel_init_err);
 310           grpc_transport_destroy(transport);
 311           grpc_slice_buffer_destroy_internal(args->read_buffer);
 312           gpr_free(args->read_buffer);
 313           if (resource_user != nullptr) {
 314             grpc_resource_user_free(resource_user,
 315                                     GRPC_RESOURCE_QUOTA_CHANNEL_SIZE);
 316           }
 317           grpc_channel_args_destroy(args->args);
 318         }
 319       } else {
 320         if (resource_user != nullptr) {
 321           grpc_resource_user_free(resource_user,
 322                                   GRPC_RESOURCE_QUOTA_CHANNEL_SIZE);
 323         }
 324       }
 325     }
 326     self->handshake_mgr_->RemoveFromPendingMgrList(
 327         &self->listener_->pending_handshake_mgrs_);
 328   }
 329   self->handshake_mgr_.reset();
 330   gpr_free(self->acceptor_);
 331   grpc_tcp_server_unref(self->listener_->tcp_server_);
 332   self->Unref();
 333 }
 334
 335 //
 336 // Chttp2ServerListener
 337 //
 338
 339 grpc_error* Chttp2ServerListener::Create(Server* server,
 340                                          grpc_resolved_address* addr,
 341                                          grpc_channel_args* args,
 342                                          Chttp2ServerArgsModifier args_modifier,
 343                                          int* port_num) {
 344   Chttp2ServerListener* listener = nullptr;
 345   // The bulk of this method is inside of a lambda to make cleanup
 346   // easier without using goto.
 347   grpc_error* error = [&]() {
 348     // Create Chttp2ServerListener.
 349     listener = new Chttp2ServerListener(server, args, args_modifier);
 350     error = grpc_tcp_server_create(&listener->tcp_server_shutdown_complete_,
 351                                    args, &listener->tcp_server_);
 352     if (error != GRPC_ERROR_NONE) return error;
 353     if (server->config_fetcher() != nullptr) {
 354       listener->resolved_address_ = *addr;
 355       // TODO(yashykt): Consider binding so as to be able to return the port
 356       // number.
 357     } else {
 358       error = grpc_tcp_server_add_port(listener->tcp_server_, addr, port_num);
 359       if (error != GRPC_ERROR_NONE) return error;
 360     }
 361     // Create channelz node.
 362     if (grpc_channel_args_find_bool(args, GRPC_ARG_ENABLE_CHANNELZ,
 363                                     GRPC_ENABLE_CHANNELZ_DEFAULT)) {
 364       std::string string_address = grpc_sockaddr_to_string(addr, false);
 365       listener->channelz_listen_socket_ =
 366           MakeRefCounted<channelz::ListenSocketNode>(
 367               string_address.c_str(),
 368               absl::StrFormat("chttp2 listener %s", string_address.c_str()));
 369     }
 370     // Register with the server only upon success
 371     server->AddListener(OrphanablePtr<Server::ListenerInterface>(listener));
 372     return GRPC_ERROR_NONE;
 373   }();
 374   if (error != GRPC_ERROR_NONE) {
 375     if (listener != nullptr) {
 376       if (listener->tcp_server_ != nullptr) {
 377         // listener is deleted when tcp_server_ is shutdown.
 378         grpc_tcp_server_unref(listener->tcp_server_);
 379       } else {
 380         delete listener;
 381       }
 382     } else {
 383       grpc_channel_args_destroy(args);
 384     }
 385   }
 386   return error;
 387 }
 388
 389 grpc_error* Chttp2ServerListener::CreateWithAcceptor(
 390     Server* server, const char* name, grpc_channel_args* args,
 391     Chttp2ServerArgsModifier args_modifier) {
 392   Chttp2ServerListener* listener =
 393       new Chttp2ServerListener(server, args, args_modifier);
 394   grpc_error* error = grpc_tcp_server_create(
 395       &listener->tcp_server_shutdown_complete_, args, &listener->tcp_server_);
 396   if (error != GRPC_ERROR_NONE) {
 397     delete listener;
 398     return error;
 399   }
 400   // TODO(yangg) channelz
 401   TcpServerFdHandler** arg_val =
 402       grpc_channel_args_find_pointer<TcpServerFdHandler*>(args, name);
 403   *arg_val = grpc_tcp_server_create_fd_handler(listener->tcp_server_);
 404   server->AddListener(OrphanablePtr<Server::ListenerInterface>(listener));
 405   return GRPC_ERROR_NONE;
 406 }
 407
 408 Chttp2ServerListener::Chttp2ServerListener(
 409     Server* server, grpc_channel_args* args,
 410     Chttp2ServerArgsModifier args_modifier)
 411     : server_(server), args_modifier_(args_modifier), args_(args) {
 412   GRPC_CLOSURE_INIT(&tcp_server_shutdown_complete_, TcpServerShutdownComplete,
 413                     this, grpc_schedule_on_exec_ctx);
 414 }
 415
 416 Chttp2ServerListener::~Chttp2ServerListener() {
 417   grpc_channel_args_destroy(args_);
 418 }
 419
 420 /* Server callback: start listening on our ports */
 421 void Chttp2ServerListener::Start(
 422     Server* /*server*/, const std::vector<grpc_pollset*>* /* pollsets */) {
 423   if (server_->config_fetcher() != nullptr) {
 424     grpc_channel_args* args = nullptr;
 425     auto watcher = absl::make_unique<ConfigFetcherWatcher>(this);
 426     {
 427       MutexLock lock(&mu_);
 428       config_fetcher_watcher_ = watcher.get();
 429       args = grpc_channel_args_copy(args_);
 430     }
 431     server_->config_fetcher()->StartWatch(
 432         grpc_sockaddr_to_string(&resolved_address_, false), args,
 433         std::move(watcher));
 434   } else {
 435     StartListening();
 436   }
 437 }
 438
 439 void Chttp2ServerListener::StartListening() {
 440   grpc_tcp_server_start(tcp_server_, &server_->pollsets(), OnAccept, this);
 441   MutexLock lock(&mu_);
 442   shutdown_ = false;
 443 }
 444
 445 void Chttp2ServerListener::SetOnDestroyDone(grpc_closure* on_destroy_done) {
 446   MutexLock lock(&mu_);
 447   on_destroy_done_ = on_destroy_done;
 448 }
 449
 450 RefCountedPtr<HandshakeManager> Chttp2ServerListener::CreateHandshakeManager() {
 451   MutexLock lock(&mu_);
 452   if (shutdown_) return nullptr;
 453   grpc_resource_user* resource_user = server_->default_resource_user();
 454   if (resource_user != nullptr &&
 455       !grpc_resource_user_safe_alloc(resource_user,
 456                                      GRPC_RESOURCE_QUOTA_CHANNEL_SIZE)) {
 457     gpr_log(GPR_ERROR,
 458             "Memory quota exhausted, rejecting connection, no handshaking.");
 459     return nullptr;
 460   }
 461   auto handshake_mgr = MakeRefCounted<HandshakeManager>();
 462   handshake_mgr->AddToPendingMgrList(&pending_handshake_mgrs_);
 463   grpc_tcp_server_ref(tcp_server_);  // Ref held by ConnectionState.
 464   return handshake_mgr;
 465 }
 466
 467 void Chttp2ServerListener::OnAccept(void* arg, grpc_endpoint* tcp,
 468                                     grpc_pollset* accepting_pollset,
 469                                     grpc_tcp_server_acceptor* acceptor) {
 470   Chttp2ServerListener* self = static_cast<Chttp2ServerListener*>(arg);
 471   RefCountedPtr<HandshakeManager> handshake_mgr =
 472       self->CreateHandshakeManager();
 473   if (handshake_mgr == nullptr) {
 474     grpc_endpoint_shutdown(tcp, GRPC_ERROR_NONE);
 475     grpc_endpoint_destroy(tcp);
 476     gpr_free(acceptor);
 477     return;
 478   }
 479   grpc_channel_args* args = nullptr;
 480   {
 481     MutexLock lock(&self->mu_);
 482     args = grpc_channel_args_copy(self->args_);
 483   }
 484   // Deletes itself when done.
 485   new ConnectionState(self, accepting_pollset, acceptor,
 486                       std::move(handshake_mgr), args, tcp);
 487   grpc_channel_args_destroy(args);
 488 }
 489
 490 void Chttp2ServerListener::TcpServerShutdownComplete(void* arg,
 491                                                      grpc_error* error) {
 492   Chttp2ServerListener* self = static_cast<Chttp2ServerListener*>(arg);
 493   /* ensure all threads have unlocked */
 494   grpc_closure* destroy_done = nullptr;
 495   {
 496     MutexLock lock(&self->mu_);
 497     destroy_done = self->on_destroy_done_;
 498     GPR_ASSERT(self->shutdown_);
 499     if (self->pending_handshake_mgrs_ != nullptr) {
 500       self->pending_handshake_mgrs_->ShutdownAllPending(GRPC_ERROR_REF(error));
 501     }
 502     self->channelz_listen_socket_.reset();
 503   }
 504   // Flush queued work before destroying handshaker factory, since that
 505   // may do a synchronous unref.
 506   ExecCtx::Get()->Flush();
 507   if (destroy_done != nullptr) {
 508     ExecCtx::Run(DEBUG_LOCATION, destroy_done, GRPC_ERROR_REF(error));
 509     ExecCtx::Get()->Flush();
 510   }
 511   delete self;
 512 }
 513
 514 /* Server callback: destroy the tcp listener (so we don't generate further
 515    callbacks) */
 516 void Chttp2ServerListener::Orphan() {
 517   // Cancel the watch before shutting down so as to avoid holding a ref to the
 518   // listener in the watcher.
 519   if (config_fetcher_watcher_ != nullptr) {
 520     server_->config_fetcher()->CancelWatch(config_fetcher_watcher_);
 521   }
 522   grpc_tcp_server* tcp_server;
 523   {
 524     MutexLock lock(&mu_);
 525     shutdown_ = true;
 526     tcp_server = tcp_server_;
 527   }
 528   grpc_tcp_server_shutdown_listeners(tcp_server);
 529   grpc_tcp_server_unref(tcp_server);
 530 }
 531
 532 }  // namespace
 533
 534 //
 535 // Chttp2ServerAddPort()
 536 //
 537
 538 grpc_error* Chttp2ServerAddPort(Server* server, const char* addr,
 539                                 grpc_channel_args* args,
 540                                 Chttp2ServerArgsModifier args_modifier,
 541                                 int* port_num) {
 542   if (strncmp(addr, "external:", 9) == 0) {
 543     return grpc_core::Chttp2ServerListener::CreateWithAcceptor(
 544         server, addr, args, args_modifier);
 545   }
 546   *port_num = -1;
 547   grpc_resolved_addresses* resolved = nullptr;
 548   std::vector<grpc_error*> error_list;
 549   // Using lambda to avoid use of goto.
 550   grpc_error* error = [&]() {
 551     if (absl::StartsWith(addr, kUnixUriPrefix)) {
 552       error = grpc_resolve_unix_domain_address(
 553           addr + sizeof(kUnixUriPrefix) - 1, &resolved);
 554     } else if (absl::StartsWith(addr, kUnixAbstractUriPrefix)) {
 555       error = grpc_resolve_unix_abstract_domain_address(
 556           addr + sizeof(kUnixAbstractUriPrefix) - 1, &resolved);
 557     } else {
 558       error = grpc_blocking_resolve_address(addr, "https", &resolved);
 559     }
 560     if (error != GRPC_ERROR_NONE) return error;
 561     // Create a listener for each resolved address.
 562     for (size_t i = 0; i < resolved->naddrs; i++) {
 563       // If address has a wildcard port (0), use the same port as a previous
 564       // listener.
 565       if (*port_num != -1 && grpc_sockaddr_get_port(&resolved->addrs[i]) == 0) {
 566         grpc_sockaddr_set_port(&resolved->addrs[i], *port_num);
 567       }
 568       int port_temp = -1;
 569       error = grpc_core::Chttp2ServerListener::Create(
 570           server, &resolved->addrs[i], grpc_channel_args_copy(args),
 571           args_modifier, &port_temp);
 572       if (error != GRPC_ERROR_NONE) {
 573         error_list.push_back(error);
 574       } else {
 575         if (*port_num == -1) {
 576           *port_num = port_temp;
 577         } else {
 578           GPR_ASSERT(*port_num == port_temp);
 579         }
 580       }
 581     }
 582     if (error_list.size() == resolved->naddrs) {
 583       std::string msg =
 584           absl::StrFormat("No address added out of total %" PRIuPTR " resolved",
 585                           resolved->naddrs);
 586       return GRPC_ERROR_CREATE_REFERENCING_FROM_COPIED_STRING(
 587           msg.c_str(), error_list.data(), error_list.size());
 588     } else if (!error_list.empty()) {
 589       std::string msg = absl::StrFormat(
 590           "Only %" PRIuPTR " addresses added out of total %" PRIuPTR
 591           " resolved",
 592           resolved->naddrs - error_list.size(), resolved->naddrs);
 593       error = GRPC_ERROR_CREATE_REFERENCING_FROM_COPIED_STRING(
 594           msg.c_str(), error_list.data(), error_list.size());
 595       gpr_log(GPR_INFO, "WARNING: %s", grpc_error_string(error));
 596       GRPC_ERROR_UNREF(error);
 597       // we managed to bind some addresses: continue without error
 598     }
 599     return GRPC_ERROR_NONE;
 600   }();  // lambda end
 601   for (grpc_error* error : error_list) {
 602     GRPC_ERROR_UNREF(error);
 603   }
 604   grpc_channel_args_destroy(args);
 605   if (resolved != nullptr) {
 606     grpc_resolved_addresses_destroy(resolved);
 607   }
 608   if (error != GRPC_ERROR_NONE) *port_num = 0;
 609   return error;
 610 }
 611
 612 }  // namespace grpc_core