Make IPC channels track their peer process ID

ipc/ipc_channel_proxy.cc

Index: ipc/ipc_channel_proxy.cc
===================================================================
--- ipc/ipc_channel_proxy.cc	(revision 130443)
+++ ipc/ipc_channel_proxy.cc	(working copy)
@@ -66,7 +66,6 @@
     : listener_message_loop_(base::MessageLoopProxy::current()),
       listener_(listener),
       ipc_message_loop_(ipc_message_loop),
-      peer_pid_(0),
       channel_connected_called_(false) {
 }
 
@@ -126,7 +125,6 @@
   // the filter is run on the IO thread.
   OnAddFilter();
 
-  peer_pid_ = peer_pid;
   for (size_t i = 0; i < filters_.size(); ++i)
     filters_[i]->OnChannelConnected(peer_pid);
 
@@ -208,11 +206,13 @@
 
     // If the channel has already been created, then we need to send this
     // message so that the filter gets access to the Channel.
-    if (channel_.get())
+    if (channel_.get()) {
       new_filters[i]->OnFilterAdded(channel_.get());
-    // Ditto for if the channel has been connected.
-    if (peer_pid_)
-      new_filters[i]->OnChannelConnected(peer_pid_);
+      // Ditto for if the channel has been connected.
+      base::ProcessId peer_pid = channel_->peer_pid();
+      if (peer_pid)
+        new_filters[i]->OnChannelConnected(peer_pid);
+    }
   }
 }
 
@@ -280,7 +280,7 @@
 
   channel_connected_called_ = true;
   if (listener_)
-    listener_->OnChannelConnected(peer_pid_);
+    listener_->OnChannelConnected(channel_->peer_pid());
 }
 
 // Called on the listener's thread
@@ -386,6 +386,12 @@
   context()->ClearIPCMessageLoop();
 }
 
+base::ProcessId ChannelProxy::peer_pid() const {

[jam, 2012/04/04 19:05:00]

ChannelProxy gets called on the listener thread, but the IPC::Channel lives on
the IO thread, so it's not correct to call its member functions on the
listener's thread..

[jschuh, 2012/04/04 19:18:08]

That is a subtlety I definitely did not appreciate. So, I'll just keep the
ChannelProxy::peer_pid_ as it was before and update it when the channel
connects.

+  if (context_.get() && context_->channel_.get())
+    return context_->channel_->peer_pid();
+  return 0;

[Tom Sepez, 2012/04/04 19:07:07]

return base::kNullProcessId constant?  Any reason to believe base::ProcessID
will be both an int/ptr as opposed to a struct, and/or 0.

[jschuh, 2012/04/04 21:05:13]

Done.

+}
+
 #if defined(OS_POSIX) && !defined(OS_NACL)
 // See the TODO regarding lazy initialization of the channel in
 // ChannelProxy::Init().