[dart:io] Adds a finalizer to _NativeSocket to avoid socket leaks

runtime/bin/eventhandler_win.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #if !defined(DART_IO_DISABLED)
 
 #include "platform/globals.h"
 #if defined(HOST_OS_WINDOWS)
 
 #include "bin/eventhandler.h"
@@ skipping 97 matching lines @@
   data_length_ = num_bytes;
   return num_bytes;
 }
 
 
 int OverlappedBuffer::GetRemainingLength() {
   ASSERT(operation_ == kRead || operation_ == kRecvFrom);
   return data_length_ - index_;
 }
 
+
 Handle::Handle(intptr_t handle)
-    : DescriptorInfoBase(handle),
+    : ReferenceCounted(),
+      DescriptorInfoBase(handle),
       handle_(reinterpret_cast<HANDLE>(handle)),
       completion_port_(INVALID_HANDLE_VALUE),
       event_handler_(NULL),
       data_ready_(NULL),
       pending_read_(NULL),
       pending_write_(NULL),
       last_error_(NOERROR),
       flags_(0),
       read_thread_id_(Thread::kInvalidThreadId),
       read_thread_handle_(NULL),
       read_thread_starting_(false),
       read_thread_finished_(false),
       monitor_(new Monitor()) {}
 
 
 Handle::~Handle() {
   delete monitor_;
 }
 
 
 bool Handle::CreateCompletionPort(HANDLE completion_port) {
+  ASSERT(completion_port_ == INVALID_HANDLE_VALUE);
+  Retain();

[zra, 2017/03/25 22:39:50]

// A reference to the Handle is Retained by the IO completion port.
// It is Released by DeleteIfClosed.

   completion_port_ = CreateIoCompletionPort(
       handle(), completion_port, reinterpret_cast<ULONG_PTR>(this), 0);
   return (completion_port_ != NULL);
 }
 
 
 void Handle::Close() {
   MonitorLocker ml(monitor_);
   if (!SupportsOverlappedIO()) {
     // If the handle uses synchronous I/O (e.g. stdin), cancel any pending
@@ skipping 234 matching lines @@
   } else {
     HandleError(this);
   }
   SetLastError(error);
 }
 
 
 void FileHandle::EnsureInitialized(EventHandlerImplementation* event_handler) {
   MonitorLocker ml(monitor_);
   event_handler_ = event_handler;
-  if (SupportsOverlappedIO() && (completion_port_ == INVALID_HANDLE_VALUE)) {
-    CreateCompletionPort(event_handler_->completion_port());
+  if (completion_port_ == INVALID_HANDLE_VALUE) {
+    if (SupportsOverlappedIO()) {
+      CreateCompletionPort(event_handler_->completion_port());
+    } else {
+      // We need to retain the Handle even if overlapped IO is not supported.
+      Retain();

[zra, 2017/03/25 22:39:50]

// It is Released by DeleteIfClosed after ReadSyncCompleteAsync
// manually puts an event on the IO completion port.

+      completion_port_ = event_handler_->completion_port();
+    }
   }
 }
 
 
 bool FileHandle::IsClosed() {
   return IsClosing() && !HasPendingRead() && !HasPendingWrite();
 }
 
 
 void DirectoryWatchHandle::EnsureInitialized(
@@ skipping 132 matching lines @@
     closesocket(buffer->client());
   }
 
   pending_accept_count_--;
   OverlappedBuffer::DisposeBuffer(buffer);
 }
 
 
 static void DeleteIfClosed(Handle* handle) {
   if (handle->IsClosed()) {
+    handle->set_completion_port(INVALID_HANDLE_VALUE);
+    handle->set_event_handler(NULL);
     handle->NotifyAllDartPorts(1 << kDestroyedEvent);
     handle->RemoveAllPorts();
-    delete handle;
+    handle->Release();

[zra, 2017/03/25 22:39:50]

// Once the Handle is closed, no further events on the IO completion port
// will mention it. Thus, we can drop the reference here.

   }
 }
 
 
 void ListenSocket::DoClose() {
   closesocket(socket());
   handle_ = INVALID_HANDLE_VALUE;
   while (CanAccept()) {
     // Get rid of connections already accepted.
     ClientSocket* client = Accept();
     if (client != NULL) {
       client->Close();
+      // Release the reference from the list.

[zra, 2017/03/25 22:39:50]

// When an accept completes, we make a new ClientSocket (1 reference),
// and add it to the IO completion port (1 more reference). If an
// accepted connection is never requested by the Dart code, then
// this list owns a reference (first Release), and the IO completion
// port owns a reference, (second Release in DeleteIfClosed).

+      client->Release();
       DeleteIfClosed(client);
     } else {
       break;
     }
   }
+  AcceptEx_ = NULL;
 }
 
 
 bool ListenSocket::CanAccept() {
   MonitorLocker ml(monitor_);
   return accepted_head_ != NULL;
 }
 
 
 ClientSocket* ListenSocket::Accept() {
@@ skipping 206 matching lines @@
   // Note that we return '0', unless a thread have already completed a write.
   if (thread_wrote_ > 0) {
     if (num_bytes > thread_wrote_) {
       num_bytes = thread_wrote_;
     }
     thread_wrote_ -= num_bytes;
     return num_bytes;
   }
   if (!write_thread_exists_) {
     write_thread_exists_ = true;
+    Retain();

[zra, 2017/03/25 22:39:50]

// The write thread gets a reference to the Handle, which it places in
// the events it puts on the IO completion port. The reference is
// Released by DeleteIfClosed.

     int result = Thread::Start(WriteFileThread, reinterpret_cast<uword>(this));
     if (result != 0) {
       FATAL1("Failed to start write file thread %d", result);
     }
     while (!write_thread_running_) {
       // Wait until we the thread is running.
       ml.Wait(Monitor::kNoTimeout);
     }
   }
   // Only queue up to INT_MAX bytes.
@@ skipping 16 matching lines @@
     }
     // Join the thread.
     DWORD res = WaitForSingleObject(thread_handle_, INFINITE);
     CloseHandle(thread_handle_);
     ASSERT(res == WAIT_OBJECT_0);
   }
   Handle::DoClose();
 }
 
 
+#if defined(DEBUG)
+intptr_t ClientSocket::disconnecting_ = 0;
+#endif
+
+
 bool ClientSocket::LoadDisconnectEx() {
   // Load the DisconnectEx function into memory using WSAIoctl.
   GUID guid_disconnect_ex = WSAID_DISCONNECTEX;
   DWORD bytes;
   int status =
       WSAIoctl(socket(), SIO_GET_EXTENSION_FUNCTION_POINTER,
                &guid_disconnect_ex, sizeof(guid_disconnect_ex), &DisconnectEx_,
                sizeof(DisconnectEx_), &bytes, NULL, NULL);
   return (status != SOCKET_ERROR);
 }
@@ skipping 66 matching lines @@
 
 void ClientSocket::IssueDisconnect() {
   OverlappedBuffer* buffer = OverlappedBuffer::AllocateDisconnectBuffer();
   BOOL ok =
       DisconnectEx_(socket(), buffer->GetCleanOverlapped(), TF_REUSE_SOCKET, 0);
   // DisconnectEx works like other OverlappedIO APIs, where we can get either an
   // immediate success or delayed operation by WSA_IO_PENDING being set.
   if (ok || (WSAGetLastError() != WSA_IO_PENDING)) {
     DisconnectComplete(buffer);
   }
+  // When the Dart side receives this event, it may decide to close its Dart
+  // ports. When all ports are closed, the VM will shut down. The EventHandler
+  // will then shut down. If the EventHandler shuts down before this
+  // asynchronous disconnect finishes, this ClientSocket will be leaked.
+  // TODO(dart:io): Retain a list of client sockets that are in the process of
+  // disconnecting. Disconnect them forcefully, and clean up their resources
+  // when the EventHandler shuts down.
   NotifyAllDartPorts(1 << kDestroyedEvent);
   RemoveAllPorts();
+#if defined(DEBUG)
+  disconnecting_++;
+#endif
 }
 
 
 void ClientSocket::DisconnectComplete(OverlappedBuffer* buffer) {
   OverlappedBuffer::DisposeBuffer(buffer);
   closesocket(socket());
   if (data_ready_ != NULL) {
     OverlappedBuffer::DisposeBuffer(data_ready_);
   }
   mark_closed();
+#if defined(DEBUG)
+  disconnecting_--;
+#endif
 }
 
 
 void ClientSocket::ConnectComplete(OverlappedBuffer* buffer) {
   OverlappedBuffer::DisposeBuffer(buffer);
   // Update socket to support full socket API, after ConnectEx completed.
   setsockopt(socket(), SOL_SOCKET, SO_UPDATE_CONNECT_CONTEXT, NULL, 0);
   // If the port is set, we already listen for this socket in Dart.
   // Handle the cases here.
   if (!IsClosedRead() && ((Mask() & (1 << kInEvent)) != 0)) {
@@ skipping 91 matching lines @@
 
 void EventHandlerImplementation::HandleInterrupt(InterruptMessage* msg) {
   ASSERT(this != NULL);
   if (msg->id == kTimerId) {
     // Change of timeout request. Just set the new timeout and port as the
     // completion thread will use the new timeout value for its next wait.
     timeout_queue_.UpdateTimeout(msg->dart_port, msg->data);
   } else if (msg->id == kShutdownId) {
     shutdown_ = true;
   } else {
-    Handle* handle = reinterpret_cast<Handle*>(msg->id);
+    Socket* socket = reinterpret_cast<Socket*>(msg->id);
+    RefCntReleaseScope<Socket> rs(socket);
+    if (socket->fd() == -1) {
+      return;
+    }
+    Handle* handle = reinterpret_cast<Handle*>(socket->fd());
     ASSERT(handle != NULL);
 
     if (handle->is_listen_socket()) {
       ListenSocket* listen_socket = reinterpret_cast<ListenSocket*>(handle);
       listen_socket->EnsureInitialized(this);
 
       MonitorLocker ml(listen_socket->monitor_);
 
       if (IS_COMMAND(msg->data, kReturnTokenCommand)) {
         listen_socket->ReturnTokens(msg->dart_port, TOKEN_COUNT(msg->data));
       } else if (IS_COMMAND(msg->data, kSetEventMaskCommand)) {
         // `events` can only have kInEvent/kOutEvent flags set.
         intptr_t events = msg->data & EVENT_MASK;
         ASSERT(0 == (events & ~(1 << kInEvent | 1 << kOutEvent)));
         listen_socket->SetPortAndMask(msg->dart_port, events);
         TryDispatchingPendingAccepts(listen_socket);
       } else if (IS_COMMAND(msg->data, kCloseCommand)) {
         listen_socket->RemovePort(msg->dart_port);
 
         // We only close the socket file descriptor from the operating
         // system if there are no other dart socket objects which
         // are listening on the same (address, port) combination.
         ListeningSocketRegistry* registry = ListeningSocketRegistry::Instance();
         MutexLocker locker(registry->mutex());
-        if (registry->CloseSafe(reinterpret_cast<intptr_t>(listen_socket))) {
+        if (registry->CloseSafe(socket)) {
           ASSERT(listen_socket->Mask() == 0);
           listen_socket->Close();
+          socket->SetClosedFd();
         }
 
         DartUtils::PostInt32(msg->dart_port, 1 << kDestroyedEvent);
       } else {
         UNREACHABLE();
       }
     } else {
       handle->EnsureInitialized(this);
       MonitorLocker ml(handle->monitor_);
 
@@ skipping 47 matching lines @@
         ClientSocket* client_socket = reinterpret_cast<ClientSocket*>(handle);
         client_socket->Shutdown(SD_RECEIVE);
       } else if (IS_COMMAND(msg->data, kShutdownWriteCommand)) {
         ASSERT(handle->is_client_socket());
 
         ClientSocket* client_socket = reinterpret_cast<ClientSocket*>(handle);
         client_socket->Shutdown(SD_SEND);
       } else if (IS_COMMAND(msg->data, kCloseCommand)) {
         handle->SetPortAndMask(msg->dart_port, 0);
         handle->Close();
+        socket->SetClosedFd();
       } else {
         UNREACHABLE();
       }
     }
 
     DeleteIfClosed(handle);
   }
 }
 
 
@@ skipping 276 matching lines @@
       }
     } else if (key == NULL) {
       // A key of NULL signals an interrupt message.
       InterruptMessage* msg = reinterpret_cast<InterruptMessage*>(overlapped);
       handler_impl->HandleInterrupt(msg);
       delete msg;
     } else {
       handler_impl->HandleIOCompletion(bytes, key, overlapped);
     }
   }
+
+  // The eventhandler thread is going down so there should be no more live
+  // Handles or Sockets.
+  // TODO(dart:io): It would be nice to be able to assert here that:
+  //     ReferenceCounted<Handle>::instances() == 0;
+  // However, we cannot at the moment. See the TODO on:
+  //     ClientSocket::IssueDisconnect()
+  DEBUG_ASSERT(ReferenceCounted<Handle>::instances() ==
+               ClientSocket::disconnecting());
+  DEBUG_ASSERT(ReferenceCounted<Socket>::instances() == 0);
   handler->NotifyShutdownDone();
 }
 
 
 void EventHandlerImplementation::Start(EventHandler* handler) {
   int result =
       Thread::Start(EventHandlerEntry, reinterpret_cast<uword>(handler));
   if (result != 0) {
     FATAL1("Failed to start event handler thread %d", result);
   }
@@ skipping 15 matching lines @@
 void EventHandlerImplementation::Shutdown() {
   SendData(kShutdownId, 0, 0);
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(HOST_OS_WINDOWS)
 
 #endif  // !defined(DART_IO_DISABLED)