root/ppapi/proxy/host_dispatcher.cc

DEFINITIONS

1. ReserveInstanceID
2. old_value_
3. allow_plugin_reentrancy_
4. InitHostWithChannel
5. GetForInstance
6. SetForInstance
7. RemoveForInstance
8. IsPlugin
9. Send
10. OnMessageReceived
11. OnChannelError
12. GetProxiedInterface
13. AddFilter
14. OnInvalidMessageReceived
15. OnHostMsgLogWithSource

// Copyright (c) 2012 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 "ppapi/proxy/host_dispatcher.h"

#include "base/debug/trace_event.h"
#include "base/logging.h"
#include "ppapi/c/private/ppb_proxy_private.h"
#include "ppapi/c/ppb_var.h"
#include "ppapi/proxy/host_var_serialization_rules.h"
#include "ppapi/proxy/interface_list.h"
#include "ppapi/proxy/ppapi_messages.h"
#include "ppapi/proxy/resource_creation_proxy.h"
#include "ppapi/shared_impl/ppapi_globals.h"

namespace ppapi {
namespace proxy {

namespace {

typedef std::map<PP_Instance, HostDispatcher*> InstanceToDispatcherMap;
InstanceToDispatcherMap* g_instance_to_dispatcher = NULL;

typedef std::map<PP_Module, HostDispatcher*> ModuleToDispatcherMap;
ModuleToDispatcherMap* g_module_to_dispatcher = NULL;

PP_Bool ReserveInstanceID(PP_Module module, PP_Instance instance) {
  // Default to returning true (usable) failure. Otherwise, if there's some
  // kind of communication error or the plugin just crashed, we'll get into an
  // infinite loop generating new instnace IDs since we think they're all in
  // use.
  ModuleToDispatcherMap::const_iterator found =
      g_module_to_dispatcher->find(module);
  if (found == g_module_to_dispatcher->end()) {
    NOTREACHED();
    return PP_TRUE;
  }

  bool usable = true;
  if (!found->second->Send(new PpapiMsg_ReserveInstanceId(instance, &usable)))
    return PP_TRUE;
  return PP_FromBool(usable);
}

// Saves the state of the given bool and puts it back when it goes out of
// scope.
class BoolRestorer {
 public:
  BoolRestorer(bool* var) : var_(var), old_value_(*var) {
  }
  ~BoolRestorer() {
    *var_ = old_value_;
  }
 private:
  bool* var_;
  bool old_value_;
};

}  // namespace

HostDispatcher::HostDispatcher(PP_Module module,
                               PP_GetInterface_Func local_get_interface,
                               SyncMessageStatusReceiver* sync_status,
                               const PpapiPermissions& permissions)
    : Dispatcher(local_get_interface, permissions),
      sync_status_(sync_status),
      pp_module_(module),
      ppb_proxy_(NULL),
      allow_plugin_reentrancy_(false) {
  if (!g_module_to_dispatcher)
    g_module_to_dispatcher = new ModuleToDispatcherMap;
  (*g_module_to_dispatcher)[pp_module_] = this;

  SetSerializationRules(new HostVarSerializationRules);

  ppb_proxy_ = reinterpret_cast<const PPB_Proxy_Private*>(
      local_get_interface(PPB_PROXY_PRIVATE_INTERFACE));
  DCHECK(ppb_proxy_) << "The proxy interface should always be supported.";

  ppb_proxy_->SetReserveInstanceIDCallback(pp_module_, &ReserveInstanceID);
}

HostDispatcher::~HostDispatcher() {
  g_module_to_dispatcher->erase(pp_module_);
}

bool HostDispatcher::InitHostWithChannel(
    Delegate* delegate,
    base::ProcessId peer_pid,
    const IPC::ChannelHandle& channel_handle,
    bool is_client,
    const ppapi::Preferences& preferences) {
  if (!Dispatcher::InitWithChannel(delegate, peer_pid, channel_handle,
                                   is_client))
    return false;
  AddIOThreadMessageFilter(sync_status_.get());

  Send(new PpapiMsg_SetPreferences(preferences));
  return true;
}

// static
HostDispatcher* HostDispatcher::GetForInstance(PP_Instance instance) {
  if (!g_instance_to_dispatcher)
    return NULL;
  InstanceToDispatcherMap::iterator found = g_instance_to_dispatcher->find(
      instance);
  if (found == g_instance_to_dispatcher->end())
    return NULL;
  return found->second;
}

// static
void HostDispatcher::SetForInstance(PP_Instance instance,
                                    HostDispatcher* dispatcher) {
  if (!g_instance_to_dispatcher)
    g_instance_to_dispatcher = new InstanceToDispatcherMap;
  (*g_instance_to_dispatcher)[instance] = dispatcher;
}

// static
void HostDispatcher::RemoveForInstance(PP_Instance instance) {
  if (!g_instance_to_dispatcher)
    return;
  InstanceToDispatcherMap::iterator found = g_instance_to_dispatcher->find(
      instance);
  if (found != g_instance_to_dispatcher->end())
    g_instance_to_dispatcher->erase(found);
}

bool HostDispatcher::IsPlugin() const {
  return false;
}

bool HostDispatcher::Send(IPC::Message* msg) {
  TRACE_EVENT2("ppapi proxy", "HostDispatcher::Send",
               "Class", IPC_MESSAGE_ID_CLASS(msg->type()),
               "Line", IPC_MESSAGE_ID_LINE(msg->type()));

  // Normal sync messages are set to unblock, which would normally cause the
  // plugin to be reentered to process them. We only want to do this when we
  // know the plugin is in a state to accept reentrancy. Since the plugin side
  // never clears this flag on messages it sends, we can't get deadlock, but we
  // may still get reentrancy in the host as a result.
  if (!allow_plugin_reentrancy_)
    msg->set_unblock(false);

  if (msg->is_sync()) {
    // Don't allow sending sync messages during module shutdown. Seee the "else"
    // block below for why.
    CHECK(!PP_ToBool(ppb_proxy()->IsInModuleDestructor(pp_module())));

    // Prevent the dispatcher from going away during sync calls. Scenarios
    // where this could happen include a Send for a sync message which while
    // waiting for the reply, dispatches an incoming ExecuteScript call which
    // destroys the plugin module and in turn the dispatcher.
    ScopedModuleReference scoped_ref(this);

    sync_status_->BeginBlockOnSyncMessage();
    bool result = Dispatcher::Send(msg);
    sync_status_->EndBlockOnSyncMessage();

    return result;
  } else {
    // We don't want to have a scoped ref for async message cases since since
    // async messages are sent during module desruction. In this case, the
    // module will have a 0 refcount and addrefing and releasing it will
    // reenter the destructor and it will crash.
    return Dispatcher::Send(msg);
  }
}

bool HostDispatcher::OnMessageReceived(const IPC::Message& msg) {
  // Prevent the dispatcher from going away during a message handler. This must
  // be at the outermost scope so it's released last.
  ScopedModuleReference death_grip(this);

  TRACE_EVENT2("ppapi proxy", "HostDispatcher::OnMessageReceived",
               "Class", IPC_MESSAGE_ID_CLASS(msg.type()),
               "Line", IPC_MESSAGE_ID_LINE(msg.type()));

  // We only want to allow reentrancy when the most recent message from the
  // plugin was a scripting message. We save the old state of the flag on the
  // stack in case we're (we are the host) being reentered ourselves. The flag
  // is set to false here for all messages, and then the scripting API will
  // explicitly set it to true during processing of those messages that can be
  // reentered.
  BoolRestorer restorer(&allow_plugin_reentrancy_);
  allow_plugin_reentrancy_ = false;

  for (size_t i = 0; i < filters_.size(); i++) {
    if (filters_[i]->OnMessageReceived(msg))
      return true;
  }

  bool handled = true;
  IPC_BEGIN_MESSAGE_MAP(HostDispatcher, msg)
    IPC_MESSAGE_HANDLER(PpapiHostMsg_LogWithSource, OnHostMsgLogWithSource)
    IPC_MESSAGE_UNHANDLED(handled = false)
  IPC_END_MESSAGE_MAP()

  if (handled)
    return true;
  return Dispatcher::OnMessageReceived(msg);

  // Note: |this| may be deleted once the death_grip goes out of scope!
}

void HostDispatcher::OnChannelError() {
  Dispatcher::OnChannelError();  // Stop using the channel.

  // Tell the host about the crash so it can clean up and display notification.
  ppb_proxy_->PluginCrashed(pp_module());
}

const void* HostDispatcher::GetProxiedInterface(const std::string& iface_name) {
  const void* proxied_interface =
      InterfaceList::GetInstance()->GetInterfaceForPPP(iface_name);
  if (!proxied_interface)
    return NULL;  // Don't have a proxy for this interface, don't query further.

  PluginSupportedMap::iterator iter(plugin_supported_.find(iface_name));
  if (iter == plugin_supported_.end()) {
    // Need to query. Cache the result so we only do this once.
    bool supported = false;

    bool previous_reentrancy_value = allow_plugin_reentrancy_;
    allow_plugin_reentrancy_ = true;
    Send(new PpapiMsg_SupportsInterface(iface_name, &supported));
    allow_plugin_reentrancy_ = previous_reentrancy_value;

    std::pair<PluginSupportedMap::iterator, bool> iter_success_pair;
    iter_success_pair = plugin_supported_.insert(
        PluginSupportedMap::value_type(iface_name, supported));
    iter = iter_success_pair.first;
  }
  if (iter->second)
    return proxied_interface;
  return NULL;
}

void HostDispatcher::AddFilter(IPC::Listener* listener) {
  filters_.push_back(listener);
}

void HostDispatcher::OnInvalidMessageReceived() {
  // TODO(brettw) bug 95345 kill the plugin when an invalid message is
  // received.
}

void HostDispatcher::OnHostMsgLogWithSource(PP_Instance instance,
                                            int int_log_level,
                                            const std::string& source,
                                            const std::string& value) {
  PP_LogLevel level = static_cast<PP_LogLevel>(int_log_level);
  if (instance) {
    PpapiGlobals::Get()->LogWithSource(instance, level, source, value);
  } else {
    PpapiGlobals::Get()->BroadcastLogWithSource(pp_module_, level,
                                                source, value);
  }
}

// ScopedModuleReference -------------------------------------------------------

ScopedModuleReference::ScopedModuleReference(Dispatcher* dispatcher)
    : dispatcher_(NULL) {
  if (!dispatcher->IsPlugin()) {
    dispatcher_ = static_cast<HostDispatcher*>(dispatcher);
    dispatcher_->ppb_proxy()->AddRefModule(dispatcher_->pp_module());
  }
}

ScopedModuleReference::~ScopedModuleReference() {
  if (dispatcher_)
    dispatcher_->ppb_proxy()->ReleaseModule(dispatcher_->pp_module());
}

}  // namespace proxy
}  // namespace ppapi