[fuchsia] Add "debug" ServiceDirectory support.

Bug: 920920
Change-Id: If3d67f02111cced48e7483b8d952a4ef00c40037
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1614688
Commit-Queue: Fabrice de Gans-Riberi <fdegans@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#660701}

base/fuchsia/service_directory.cc

@@ -10,6 +10,7 @@
 #include <zircon/processargs.h>
 
 #include "base/fuchsia/fuchsia_logging.h"
+#include "base/memory/ptr_util.h"
 #include "base/message_loop/message_loop_current.h"
 #include "base/no_destructor.h"
 
@@ -27,8 +28,11 @@ ServiceDirectory::~ServiceDirectory() {
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
   DCHECK(services_.empty());
 
-  zx_status_t status = svc_dir_destroy(svc_dir_);
-  ZX_DCHECK(status == ZX_OK, status);
+  // Only the root ServiceDirectory "owns" svc_dir_.
+  if (!sub_directory_) {
+    zx_status_t status = svc_dir_destroy(svc_dir_);
+    ZX_DCHECK(status == ZX_OK, status);
+  }
 }
 
 // static
@@ -48,6 +52,8 @@ void ServiceDirectory::Initialize(
       svc_dir_create(async_get_default_dispatcher(),
                      request.TakeChannel().release(), &svc_dir_);
   ZX_CHECK(status == ZX_OK, status);
+
+  debug_ = WrapUnique(new ServiceDirectory(svc_dir_, "debug"));
 }
 
 void ServiceDirectory::AddServiceUnsafe(
@@ -60,21 +66,29 @@ void ServiceDirectory::AddServiceUnsafe(
   std::string name_str = name.as_string();
   services_[name_str] = connect_callback;
 
-  // Publish to "svc".
-  zx_status_t status =
-      svc_dir_add_service(svc_dir_, "svc", name_str.c_str(), this,
-                          &ServiceDirectory::HandleConnectRequest);
-  ZX_DCHECK(status == ZX_OK, status);
-
-  // Publish to "public" for compatibility.
-  status = svc_dir_add_service(svc_dir_, "public", name_str.c_str(), this,
-                               &ServiceDirectory::HandleConnectRequest);
-  ZX_DCHECK(status == ZX_OK, status);
-
-  // Publish to the legacy "flat" namespace, which is required by some clients.
-  status = svc_dir_add_service(svc_dir_, nullptr, name_str.c_str(), this,
-                               &ServiceDirectory::HandleConnectRequest);
-  ZX_DCHECK(status == ZX_OK, status);
+  if (sub_directory_) {
+    zx_status_t status =
+        svc_dir_add_service(svc_dir_, sub_directory_, name_str.c_str(), this,
+                            &ServiceDirectory::HandleConnectRequest);
+    ZX_DCHECK(status == ZX_OK, status);
+  } else {
+    // Publish to "svc".
+    zx_status_t status =
+        svc_dir_add_service(svc_dir_, "svc", name_str.c_str(), this,
+                            &ServiceDirectory::HandleConnectRequest);
+    ZX_DCHECK(status == ZX_OK, status);
+
+    // Publish to "public" for compatibility.
+    status = svc_dir_add_service(svc_dir_, "public", name_str.c_str(), this,
+                                 &ServiceDirectory::HandleConnectRequest);
+    ZX_DCHECK(status == ZX_OK, status);
+
+    // Publish to the legacy "flat" namespace, which is required by some
+    // clients.
+    status = svc_dir_add_service(svc_dir_, nullptr, name_str.c_str(), this,
+                                 &ServiceDirectory::HandleConnectRequest);
+    ZX_DCHECK(status == ZX_OK, status);
+  }
 }
 
 void ServiceDirectory::RemoveService(StringPiece name) {
@@ -87,14 +101,20 @@ void ServiceDirectory::RemoveService(StringPiece name) {
   DCHECK(it != services_.end());
   services_.erase(it);
 
-  // Unregister from "svc", "public", and flat namespace.
-  zx_status_t status =
-      svc_dir_remove_service(svc_dir_, "svc", name_str.c_str());
-  ZX_DCHECK(status == ZX_OK, status);
-  status = svc_dir_remove_service(svc_dir_, "public", name_str.c_str());
-  ZX_DCHECK(status == ZX_OK, status);
-  status = svc_dir_remove_service(svc_dir_, nullptr, name_str.c_str());
-  ZX_DCHECK(status == ZX_OK, status);
+  if (sub_directory_) {
+    zx_status_t status =
+        svc_dir_remove_service(svc_dir_, sub_directory_, name_str.c_str());
+    ZX_DCHECK(status == ZX_OK, status);
+  } else {
+    // Unregister from "svc", "public", and flat namespace.
+    zx_status_t status =
+        svc_dir_remove_service(svc_dir_, "svc", name_str.c_str());
+    ZX_DCHECK(status == ZX_OK, status);
+    status = svc_dir_remove_service(svc_dir_, "public", name_str.c_str());
+    ZX_DCHECK(status == ZX_OK, status);
+    status = svc_dir_remove_service(svc_dir_, nullptr, name_str.c_str());
+    ZX_DCHECK(status == ZX_OK, status);
+  }
 }
 
 void ServiceDirectory::RemoveAllServices() {
@@ -119,5 +139,12 @@ void ServiceDirectory::HandleConnectRequest(void* context,
   it->second.Run(zx::channel(service_request));
 }
 
+ServiceDirectory::ServiceDirectory(svc_dir_t* svc_dir, const char* name) {
+  DCHECK(svc_dir);
+
+  svc_dir_ = svc_dir;
+  sub_directory_ = name;
+}
+
 }  // namespace fuchsia
 }  // namespace base

base/fuchsia/service_directory.h

@@ -31,6 +31,8 @@ namespace fuchsia {
 // implementation is destroyed. GetDefault() should be used to get the default
 // ServiceDirectory for the current process. The default instance exports
 // services via a channel supplied at process creation time.
+// Debug services are published to a "debug" sub-directory only accessible by
+// other services via the Hub.
 //
 // Not thread-safe. All methods must be called on the thread that created the
 // object.
@@ -71,6 +73,9 @@ class BASE_EXPORT ServiceDirectory {
   void RemoveService(StringPiece name);
   void RemoveAllServices();
 
+  // Returns the debug ServiceDirectory.
+  ServiceDirectory* debug() const { return debug_.get(); }
+
   // Passes requests for |name| through to a generic |connect_callback|.
   // This is used only when proxying requests for interfaces not known at
   // compile-time. Use the type-safe APIs above whenever possible.
@@ -78,6 +83,9 @@ class BASE_EXPORT ServiceDirectory {
                         RepeatingCallback<void(zx::channel)> connect_callback);
 
  private:
+  // Sub-directory constructor.
+  ServiceDirectory(svc_dir_t* svc_dir, const char* name);
+
   // Called by |svc_dir_| to handle service requests.
   static void HandleConnectRequest(void* context,
                                    const char* service_name,
@@ -85,9 +93,17 @@ class BASE_EXPORT ServiceDirectory {
 
   THREAD_CHECKER(thread_checker_);
 
+  // Owned by the root directory.
   svc_dir_t* svc_dir_ = nullptr;
   flat_map<std::string, RepeatingCallback<void(zx::channel)>> services_;
 
+  // The debug sub-directory. Empty if this is a sub-directory.
+  std::unique_ptr<ServiceDirectory> debug_;
+
+  // If mon-null, this directory represents a sub-directory of the root
+  // ServiceDirectory.
+  const char* sub_directory_ = nullptr;
+
   DISALLOW_COPY_AND_ASSIGN(ServiceDirectory);
 };
 

base/fuchsia/service_directory_test_base.cc

@@ -31,6 +31,15 @@ ServiceDirectoryTestBase::ServiceDirectoryTestBase() {
   public_service_directory_client_ =
       std::make_unique<ServiceDirectoryClient>(std::move(svc_directory));
 
+  // Create the ServiceDirectoryClient, connected to the "debug" sub-directory.
+  fidl::InterfaceHandle<::fuchsia::io::Directory> debug_directory;
+  CHECK_EQ(fdio_service_connect_at(
+               directory.channel().get(), "/debug/.",
+               debug_directory.NewRequest().TakeChannel().release()),
+           ZX_OK);
+  debug_service_directory_client_ =
+      std::make_unique<ServiceDirectoryClient>(std::move(debug_directory));
+
   // Create the ServiceDirectoryClient, connected to the "public" sub-directory
   // (same contents as "svc", provided for compatibility).
   fidl::InterfaceHandle<::fuchsia::io::Directory> public_directory;

base/fuchsia/service_directory_test_base.h

@@ -35,6 +35,7 @@ class ServiceDirectoryTestBase : public testing::Test {
       service_binding_;
 
   std::unique_ptr<ServiceDirectoryClient> public_service_directory_client_;
+  std::unique_ptr<ServiceDirectoryClient> debug_service_directory_client_;
   std::unique_ptr<ServiceDirectoryClient>
       legacy_public_service_directory_client_;
   std::unique_ptr<ServiceDirectoryClient> root_service_directory_client_;

base/fuchsia/service_directory_unittest.cc

@@ -96,5 +96,23 @@ TEST_F(ServiceDirectoryTest, NoService) {
   VerifyTestInterface(&stub, ZX_ERR_PEER_CLOSED);
 }
 
+// Verify that we can connect to a debug service.
+TEST_F(ServiceDirectoryTest, ConnectDebugService) {
+  // Remove the public service binding.
+  service_binding_.reset();
+
+  // Publish the test service to the "debug" directory.
+  ScopedServiceBinding<testfidl::TestInterface> debug_service_binding(
+      service_directory_->debug(), &test_service_);
+
+  auto debug_stub = debug_service_directory_client_
+                        ->ConnectToService<testfidl::TestInterface>();
+  VerifyTestInterface(&debug_stub, ZX_OK);
+
+  auto release_stub = public_service_directory_client_
+                          ->ConnectToService<testfidl::TestInterface>();
+  VerifyTestInterface(&release_stub, ZX_ERR_PEER_CLOSED);
+}
+
 }  // namespace fuchsia
 }  // namespace base