Define IPC_USES_READWRITE

ipc/ipc_channel_posix.cc

Index: ipc/ipc_channel_posix.cc
diff --git a/ipc/ipc_channel_posix.cc b/ipc/ipc_channel_posix.cc
index bbf137432943d7abfe487f8dacf96828a31823ee..4a71f424eac123aa898ce329069813da0bf1f3b9 100644
--- a/ipc/ipc_channel_posix.cc
+++ b/ipc/ipc_channel_posix.cc
@@ -285,7 +285,7 @@ Channel::ChannelImpl::ChannelImpl(const std::string& channel_id, Mode mode,
       server_listen_pipe_(-1),
       pipe_(-1),
       client_pipe_(-1),
-#if !defined(OS_MACOSX)
+#if defined(IPC_USES_READWRITE)
       fd_pipe_(-1),
       remote_fd_pipe_(-1),
 #endif
@@ -407,16 +407,10 @@ bool Channel::ChannelImpl::CreatePipe(const std::string& channel_id,
   scoped_ptr<Message> msg(new Message(MSG_ROUTING_NONE,
                                       HELLO_MESSAGE_TYPE,
                                       IPC::Message::PRIORITY_NORMAL));
-  #if !defined(OS_MACOSX)
+  #if defined(IPC_USES_READWRITE)
   if (!uses_fifo_) {
-    // On Linux, the seccomp sandbox makes it very expensive to call
-    // recvmsg() and sendmsg(). Often, we are perfectly OK with resorting to
-    // read() and write(), which are cheap.
-    //
-    // As we cannot anticipate, when the sender will provide us with file
-    // handles, we have to make the decision about whether we call read() or
-    // recvmsg() before we actually make the call. The easiest option is to
-    // create a dedicated socketpair() for exchanging file handles.
+    // Create a dedicated socketpair() for exchanging file descriptors.
+    // See comments for IPC_USES_READWRITE for details.
     if (mode == MODE_SERVER) {
       fd_pipe_ = -1;
     } else if (remote_fd_pipe_ == -1) {
@@ -483,7 +477,7 @@ bool Channel::ChannelImpl::ProcessIncomingMessages() {
       // Read from pipe.
       // recvmsg() returns 0 if the connection has closed or EAGAIN if no data
       // is waiting on the pipe.
-#if !defined(OS_MACOSX)
+#if defined(IPC_USES_READWRITE)
       if (fd_pipe_ >= 0) {
         bytes_read = HANDLE_EINTR(read(pipe_, input_buf_,
                                        Channel::kReadBufferSize));
@@ -616,7 +610,7 @@ bool Channel::ChannelImpl::ProcessIncomingMessages() {
           if (m.header()->num_fds > num_fds - fds_i) {
             // the message has been completely received, but we didn't get
             // enough file descriptors.
-#if !defined(OS_MACOSX)
+#if defined(IPC_USES_READWRITE)
             if (!uses_fifo_) {
               char dummy;
               struct iovec fd_pipe_iov = { &dummy, 1 };
@@ -706,7 +700,7 @@ bool Channel::ChannelImpl::ProcessIncomingMessages() {
           if (!m.ReadInt(&iter, &pid)) {
             NOTREACHED();
           }
-#if !defined(OS_MACOSX)
+#if defined(IPC_USES_READWRITE)
           if (mode_ == MODE_SERVER && !uses_fifo_) {
             // On non-Mac, the Hello message from the client to the server
             // also contains the fd_pipe_, which  will be used for all
@@ -769,7 +763,7 @@ bool Channel::ChannelImpl::ProcessOutgoingMessages() {
   while (!output_queue_.empty()) {
     Message* msg = output_queue_.front();
 
-#if !defined(OS_MACOSX)
+#if defined(IPC_USES_READWRITE)
     scoped_ptr<Message> hello;
     if (remote_fd_pipe_ != -1 &&
         msg->routing_id() == MSG_ROUTING_NONE &&
@@ -839,7 +833,7 @@ bool Channel::ChannelImpl::ProcessOutgoingMessages() {
       // num_fds < MAX_DESCRIPTORS_PER_MESSAGE so no danger of overflow.
       msg->header()->num_fds = static_cast<uint16>(num_fds);
 
-#if !defined(OS_MACOSX)
+#if defined(IPC_USES_READWRITE)
       if (!uses_fifo_ &&
           (msg->routing_id() != MSG_ROUTING_NONE ||
            msg->type() != HELLO_MESSAGE_TYPE)) {
@@ -861,7 +855,7 @@ bool Channel::ChannelImpl::ProcessOutgoingMessages() {
 
     if (bytes_written == 1) {
       fd_written = pipe_;
-#if !defined(OS_MACOSX)
+#if defined(IPC_USES_READWRITE)
       if (mode_ != MODE_SERVER && !uses_fifo_ &&
           msg->routing_id() == MSG_ROUTING_NONE &&
           msg->type() == HELLO_MESSAGE_TYPE) {
@@ -1030,7 +1024,7 @@ void Channel::ChannelImpl::Close() {
     PipeMap::GetInstance()->RemoveAndClose(pipe_name_);
     client_pipe_ = -1;
   }
-#if !defined(OS_MACOSX)
+#if defined(IPC_USES_READWRITE)
   if (fd_pipe_ != -1) {
     if (HANDLE_EINTR(close(fd_pipe_)) < 0)
       PLOG(ERROR) << "close";