Add a force pipelining option to load flags.

net/socket/buffered_write_stream_socket.cc

+// 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 "net/socket/buffered_write_stream_socket.h"
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/message_loop.h"
+#include "net/base/io_buffer.h"
+#include "net/base/net_errors.h"
+
+namespace net {
+
+BufferedWriteStreamSocket::BufferedWriteStreamSocket(
+    StreamSocket* socket_to_wrap)
+    : wrapped_socket_(socket_to_wrap),
+      io_buffer_(new GrowableIOBuffer()),
+      ALLOW_THIS_IN_INITIALIZER_LIST(weak_factory_(this)),
+      pending_callback_(false),
+      error_(0) {
+}
+
+BufferedWriteStreamSocket::~BufferedWriteStreamSocket() {
+}
+
+int BufferedWriteStreamSocket::Read(IOBuffer* buf, int buf_len,
+                                    const CompletionCallback& callback) {
+  return wrapped_socket_->Read(buf, buf_len, callback);
+}
+
+int BufferedWriteStreamSocket::Write(IOBuffer* buf, int buf_len,
+                                     const CompletionCallback& callback) {
+  if (error_) {
+    return error_;
+  }
+  int old_capacity = io_buffer_->capacity();
+  io_buffer_->SetCapacity(old_capacity + buf_len);
+  memcpy(io_buffer_->data() + old_capacity, buf->data(), buf_len);
+  if (!pending_callback_) {
+    MessageLoop::current()->PostTask(
+        FROM_HERE,
+        base::Bind(&BufferedWriteStreamSocket::DoDelayedWrite,
+                   weak_factory_.GetWeakPtr()));
+    pending_callback_ = true;
+  }
+  return buf_len;
+}
+
+bool BufferedWriteStreamSocket::SetReceiveBufferSize(int32 size) {
+  return wrapped_socket_->SetReceiveBufferSize(size);
+}
+
+bool BufferedWriteStreamSocket::SetSendBufferSize(int32 size) {
+  return wrapped_socket_->SetSendBufferSize(size);
+}
+
+int BufferedWriteStreamSocket::Connect(const CompletionCallback& callback) {
+  return wrapped_socket_->Connect(callback);
+}
+
+void BufferedWriteStreamSocket::Disconnect() {
+  wrapped_socket_->Disconnect();
+}
+
+bool BufferedWriteStreamSocket::IsConnected() const {
+  return wrapped_socket_->IsConnected();
+}
+
+bool BufferedWriteStreamSocket::IsConnectedAndIdle() const {
+  return wrapped_socket_->IsConnectedAndIdle();
+}
+
+int BufferedWriteStreamSocket::GetPeerAddress(AddressList* address) const {
+  return wrapped_socket_->GetPeerAddress(address);
+}
+
+int BufferedWriteStreamSocket::GetLocalAddress(IPEndPoint* address) const {
+  return wrapped_socket_->GetLocalAddress(address);
+}
+
+const BoundNetLog& BufferedWriteStreamSocket::NetLog() const {
+  return wrapped_socket_->NetLog();
+}
+
+void BufferedWriteStreamSocket::SetSubresourceSpeculation() {
+  wrapped_socket_->SetSubresourceSpeculation();
+}
+
+void BufferedWriteStreamSocket::SetOmniboxSpeculation() {
+  wrapped_socket_->SetOmniboxSpeculation();
+}
+
+bool BufferedWriteStreamSocket::WasEverUsed() const {
+  return wrapped_socket_->WasEverUsed();
+}
+
+bool BufferedWriteStreamSocket::UsingTCPFastOpen() const {
+  return wrapped_socket_->UsingTCPFastOpen();
+}
+
+int64 BufferedWriteStreamSocket::NumBytesRead() const {
+  return wrapped_socket_->NumBytesRead();
+}
+
+base::TimeDelta BufferedWriteStreamSocket::GetConnectTimeMicros() const {
+  return wrapped_socket_->GetConnectTimeMicros();
+}
+
+void BufferedWriteStreamSocket::DoDelayedWrite() {
+  int result = wrapped_socket_->Write(
+      io_buffer_, io_buffer_->RemainingCapacity(),
+      base::Bind(&BufferedWriteStreamSocket::OnIOComplete,
+                 base::Unretained(this)));

[mmenke, 2012/02/24 16:36:39]

This does not look safe to me.  If we get ERR_IO_PENDING, and then we get
another call to wrapped_socket_->Write(), we realloc the buffer, but the
|wrapped_socket_| holds on to a pointer to the buffer while it's writing, and is
sitll allowed to read from it.  This results in the underlying OS write function
possibly dereferencing a stale pointer.

I believe you need special behavior if BufferedWriteStreamSocket::Write is
called while |wrapped_socket_| is writing to the socket.  You need to return
ERR_IO_PENDING and keep information about the passed in buffer.  Then, when
OnIOComplete is called, you append the cached bytes to send to the io_buffer_
and send them.  Once that's done, you call the callback function that was passed
to write.

Alternatively, you could CHECK that this never happens in
BufferedWriteStreamSocket::Write.  If you do this, should have a big warning in
the header file, and maybe change the class name to be scarier.

[James Simonsen, 2012/02/24 23:58:51]

Nice catch!

I went with a backup buffer. It's the same sort of idea as double buffering for
a video display, except that we append instead of swap.

[mmenke, 2012/02/25 00:32:43]

Great, I much prefer this approach..

+  if (result == ERR_IO_PENDING) {
+    pending_callback_ = true;
+  } else {
+    OnIOComplete(result);
+  }
+}
+
+void BufferedWriteStreamSocket::OnIOComplete(int result) {
+  pending_callback_ = false;
+  if (result < 0) {
+    error_ = result;
+    io_buffer_->SetCapacity(0);
+  } else {
+    io_buffer_->set_offset(io_buffer_->offset() + result);
+    if (io_buffer_->RemainingCapacity()) {
+      DoDelayedWrite();
+    } else {
+      io_buffer_->SetCapacity(0);
+    }
+  }
+}
+
+}  // namespace net