Avoid channel clone (#43181)

Use fdio_fd_transfer instead of fdio_fd_clone.

shell/platform/fuchsia/dart-pkg/zircon/BUILD.gn

@@ -26,6 +26,7 @@ source_set("zircon") {
   ]
 
   deps = [
+    "$fuchsia_sdk_root/fidl:fuchsia.io",
     "$fuchsia_sdk_root/pkg:async-cpp",
     "$fuchsia_sdk_root/pkg:async-default",
     "$fuchsia_sdk_root/pkg:async-loop-cpp",

shell/platform/fuchsia/dart-pkg/zircon/sdk_ext/system.cc

@@ -6,8 +6,9 @@
 
 #include <array>
 
-#include <fcntl.h>
+#include <fuchsia/io/cpp/fidl.h>
 #include <lib/fdio/directory.h>
+#include <lib/fdio/fd.h>
 #include <lib/fdio/io.h>
 #include <lib/fdio/limits.h>
 #include <lib/fdio/namespace.h>
@@ -172,17 +173,25 @@ fdio_ns_t* GetNamespace() {
   return reinterpret_cast<fdio_ns_t*>(fdio_ns_ptr);
 }
 
-fml::UniqueFD FdFromPath(std::string path) {
-  // Get a VMO for the file.
-  fdio_ns_t* ns = reinterpret_cast<fdio_ns_t*>(GetNamespace());
-  fml::UniqueFD dirfd(fdio_ns_opendir(ns));
-  if (!dirfd.is_valid())
-    return fml::UniqueFD();
-
-  const char* c_path = path.c_str();
-  if (path.length() > 0 && c_path[0] == '/')
-    c_path = &c_path[1];
-  return fml::UniqueFD(openat(dirfd.get(), c_path, O_RDONLY));
+zx_status_t FdFromPath(const char* path, fml::UniqueFD& fd) {
+  fml::UniqueFD dir_fd(fdio_ns_opendir(GetNamespace()));
+  if (!dir_fd.is_valid()) {
+    // TODO: can we return errno?
+    return ZX_ERR_IO;
+  }
+  if (path != nullptr && *path == '/') {
+    path++;
+  }
+  int raw_fd;
+  if (zx_status_t status = fdio_open_fd_at(
+          dir_fd.get(), path,
+          static_cast<uint32_t>(fuchsia::io::OpenFlags::RIGHT_READABLE),
+          &raw_fd);
+      status != ZX_OK) {
+    return status;
+  }
+  fd.reset(raw_fd);
+  return ZX_OK;
 }
 
 }  // namespace
@@ -207,36 +216,30 @@ zx_status_t System::ConnectToService(std::string path,
                                  channel->ReleaseHandle());
 }
 
-zx::channel System::CloneChannelFromFileDescriptor(int fd) {
-  zx::handle handle;
-  zx_status_t status = fdio_fd_clone(fd, handle.reset_and_get_address());
-  if (status != ZX_OK)
-    return zx::channel();
-
-  zx_info_handle_basic_t info = {};
-  status =
-      handle.get_info(ZX_INFO_HANDLE_BASIC, &info, sizeof(info), NULL, NULL);
-
-  if (status != ZX_OK || info.type != ZX_OBJ_TYPE_CHANNEL)
-    return zx::channel();
-
-  return zx::channel(handle.release());
-}
-
 Dart_Handle System::ChannelFromFile(std::string path) {
-  fml::UniqueFD fd = FdFromPath(path);
-  if (!fd.is_valid()) {
-    return ConstructDartObject(kHandleResult, ToDart(ZX_ERR_IO));
+  fml::UniqueFD fd;
+  if (zx_status_t status = FdFromPath(path.c_str(), fd); status != ZX_OK) {
+    return ConstructDartObject(kHandleResult, ToDart(status));
   }
 
-  // Get channel from fd.
-  zx::channel channel = CloneChannelFromFileDescriptor(fd.get());
-  if (!channel) {
-    return ConstructDartObject(kHandleResult, ToDart(ZX_ERR_IO));
+  zx::handle handle;
+  if (zx_status_t status =
+          fdio_fd_transfer(fd.release(), handle.reset_and_get_address());
+      status != ZX_OK) {
+    return ConstructDartObject(kHandleResult, ToDart(status));
+  }
+  zx_info_handle_basic_t info;
+  if (zx_status_t status = handle.get_info(ZX_INFO_HANDLE_BASIC, &info,
+                                           sizeof(info), nullptr, nullptr);
+      status != ZX_OK) {
+    return ConstructDartObject(kHandleResult, ToDart(status));
+  }
+  if (info.type != ZX_OBJ_TYPE_CHANNEL) {
+    return ConstructDartObject(kHandleResult, ToDart(ZX_ERR_WRONG_TYPE));
   }
 
   return ConstructDartObject(kHandleResult, ToDart(ZX_OK),
-                             ToDart(Handle::Create(channel.release())));
+                             ToDart(Handle::Create(handle.release())));
 }
 
 zx_status_t System::ChannelWrite(fml::RefPtr<Handle> channel,
@@ -451,20 +454,25 @@ Dart_Handle System::VmoCreate(uint64_t size, uint32_t options) {
 }
 
 Dart_Handle System::VmoFromFile(std::string path) {
-  fml::UniqueFD fd = FdFromPath(path);
-  if (!fd.is_valid())
-    return ConstructDartObject(kFromFileResult, ToDart(ZX_ERR_IO));
+  fml::UniqueFD fd;
+  if (zx_status_t status = FdFromPath(path.c_str(), fd); status != ZX_OK) {
+    return ConstructDartObject(kHandleResult, ToDart(status));
+  }
 
   struct stat stat_struct;
-  if (fstat(fd.get(), &stat_struct) == -1)
+  if (fstat(fd.get(), &stat_struct) != 0) {
+    // TODO: can we return errno?
     return ConstructDartObject(kFromFileResult, ToDart(ZX_ERR_IO));
-  zx_handle_t vmo = ZX_HANDLE_INVALID;
-  zx_status_t status = fdio_get_vmo_clone(fd.get(), &vmo);
-  if (status != ZX_OK)
+  }
+  zx::vmo vmo;
+  if (zx_status_t status =
+          fdio_get_vmo_clone(fd.get(), vmo.reset_and_get_address());
+      status != ZX_OK) {
     return ConstructDartObject(kFromFileResult, ToDart(status));
+  }
 
-  return ConstructDartObject(kFromFileResult, ToDart(status),
-                             ToDart(Handle::Create(vmo)),
+  return ConstructDartObject(kFromFileResult, ToDart(ZX_OK),
+                             ToDart(Handle::Create(vmo.release())),
                              ToDart(stat_struct.st_size));
 }
 

shell/platform/fuchsia/dart-pkg/zircon/sdk_ext/system.h

@@ -76,8 +76,6 @@ class System : public fml::RefCountedThreadSafe<System>,
 
  private:
   static void VmoMapFinalizer(void* isolate_callback_data, void* peer);
-
-  static zx::channel CloneChannelFromFileDescriptor(int fd);
 };
 
 }  // namespace dart