[mojo-edk] Support transferring null Mach ports.

mojo/edk/system/mach_port_relay.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/edk/system/mach_port_relay.h"
 
 #include <mach/mach.h>
 
 #include <utility>
 
 #include "base/logging.h"
 #include "base/mac/mach_port_util.h"
 #include "base/mac/scoped_mach_port.h"
 #include "base/process/process.h"
 #include "mojo/edk/embedder/platform_handle_vector.h"
 
 namespace mojo {
 namespace edk {
 
 // static
 bool MachPortRelay::ReceivePorts(PlatformHandleVector* handles) {
   DCHECK(handles);
 
   for (size_t i = 0; i < handles->size(); i++) {
     PlatformHandle* handle = handles->data() + i;
     DCHECK(handle->type != PlatformHandle::Type::MACH);
     if (handle->type != PlatformHandle::Type::MACH_NAME)
       continue;
 
+    if (handle->port == MACH_PORT_NULL) {
+      handle->type = PlatformHandle::Type::MACH;
+      continue;
+    }
+
     base::mac::ScopedMachReceiveRight message_port(handle->port);
     base::mac::ScopedMachSendRight received_port(
         base::ReceiveMachPort(message_port.get()));
     if (received_port.get() == MACH_PORT_NULL) {
       handle->port = MACH_PORT_NULL;
       LOG(ERROR) << "Error receiving mach port";
       return false;
     }
 
     handle->port = received_port.release();
@@ skipping 25 matching lines @@
   ScopedPlatformHandleVectorPtr handles = message->TakeHandles();
   // Message should have handles, otherwise there's no point in calling this
   // function.
   DCHECK(handles);
   for (size_t i = 0; i < handles->size(); i++) {
     PlatformHandle* handle = &(*handles)[i];
     DCHECK(handle->type != PlatformHandle::Type::MACH_NAME);
     if (handle->type != PlatformHandle::Type::MACH)
       continue;
 
+    if (handle->port == MACH_PORT_NULL) {
+      handle->type = PlatformHandle::Type::MACH_NAME;
+      num_sent++;
+      continue;
+    }
+
     mach_port_name_t intermediate_port;
-    DCHECK(handle->port != MACH_PORT_NULL);
     intermediate_port = base::CreateIntermediateMachPort(
         task_port, base::mac::ScopedMachSendRight(handle->port), nullptr);
     if (intermediate_port == MACH_PORT_NULL) {
       handle->port = MACH_PORT_NULL;
       error = true;
       break;
     }
     handle->port = intermediate_port;
     handle->type = PlatformHandle::Type::MACH_NAME;
     num_sent++;
@@ skipping 17 matching lines @@
   ScopedPlatformHandleVectorPtr handles = message->TakeHandles();
   // Message should have handles, otherwise there's no point in calling this
   // function.
   DCHECK(handles);
   for (size_t i = 0; i < handles->size(); i++) {
     PlatformHandle* handle = handles->data() + i;
     DCHECK(handle->type != PlatformHandle::Type::MACH);
     if (handle->type != PlatformHandle::Type::MACH_NAME)
       continue;
 
+    if (handle->port == MACH_PORT_NULL) {
+      handle->type = PlatformHandle::Type::MACH;
+      num_received++;
+      continue;
+    }
+
     mach_port_t extracted_right = MACH_PORT_NULL;
     mach_msg_type_name_t extracted_right_type;
     kern_return_t kr =
         mach_port_extract_right(task_port, handle->port,
                                 MACH_MSG_TYPE_MOVE_SEND,
                                 &extracted_right, &extracted_right_type);
     if (kr != KERN_SUCCESS) {
       error = true;
       break;
     }
@@ skipping 22 matching lines @@
 }
 
 void MachPortRelay::OnReceivedTaskPort(base::ProcessHandle process) {
   base::AutoLock locker(observers_lock_);
   for (const auto observer : observers_)
     observer->OnProcessReady(process);
 }
 
 }  // namespace edk
 }  // namespace mojo