Fix potential teardown race conditions with TCPEngineTransport's PostTasks.

blimp/net/tcp_engine_transport.cc

 // Copyright 2015 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 "blimp/net/tcp_engine_transport.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/callback.h"
 #include "base/callback_helpers.h"
 #include "base/location.h"
 #include "base/memory/ptr_util.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "blimp/net/message_port.h"
 #include "blimp/net/tcp_connection.h"
 #include "net/log/net_log_source.h"
 #include "net/socket/stream_socket.h"
 #include "net/socket/tcp_server_socket.h"
 
 namespace blimp {
 
 TCPEngineTransport::TCPEngineTransport(const net::IPEndPoint& address,
                                        net::NetLog* net_log)
-    : address_(address), net_log_(net_log) {}
+    : address_(address), net_log_(net_log), weak_factory_(this) {}
 
 TCPEngineTransport::~TCPEngineTransport() {}
 
 void TCPEngineTransport::Connect(const net::CompletionCallback& callback) {
   DCHECK(!accepted_socket_);
   DCHECK(!callback.is_null());
 
   if (!server_socket_) {
     server_socket_.reset(
         new net::TCPServerSocket(net_log_, net::NetLogSource()));
     int result = server_socket_->Listen(address_, 5);
     if (result != net::OK) {
       server_socket_.reset();
       base::ThreadTaskRunnerHandle::Get()->PostTask(
           FROM_HERE, base::Bind(callback, result));
       return;
     }
   }
 
-  net::CompletionCallback accept_callback = base::Bind(
-      &TCPEngineTransport::OnTCPConnectAccepted, base::Unretained(this));
+  net::CompletionCallback accept_callback =
+      base::Bind(&TCPEngineTransport::OnTCPConnectAccepted,
+                 weak_factory_.GetWeakPtr(), callback);

[Wez, 2016/11/18 02:35:47]

nit: Up to you, but I quite liked that the |callback| got saved into the object,
and later ResetAndReturn().Run()'d, since there are other stateful aspects to
this, e.g. the |accepted_socket_| anyway. It also has the nice property that you
can DCHECK(!connect_callback_) at the top of Connect() to trap duplicate calls,
if you want.

[Kevin M, 2016/11/18 18:17:38]

Yeah, that's true. I'll revert that change.

 
   int result = server_socket_->Accept(&accepted_socket_, accept_callback);
   if (result == net::ERR_IO_PENDING) {
-    connect_callback_ = callback;
     return;
   }
 
-  if (result != net::OK) {
-    server_socket_.reset();
-  }
-
-  base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
-                                                base::Bind(callback, result));
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE, base::Bind(accept_callback, result));
 }
 
 std::unique_ptr<MessagePort> TCPEngineTransport::TakeMessagePort() {
-  DCHECK(connect_callback_.is_null());
   DCHECK(accepted_socket_);
   return MessagePort::CreateForStreamSocketWithCompression(
       std::move(accepted_socket_));
 }
 
 std::unique_ptr<BlimpConnection> TCPEngineTransport::MakeConnection() {
   return base::MakeUnique<TCPConnection>(TakeMessagePort());
 }
 
 const char* TCPEngineTransport::GetName() const {
   return "TCP";
 }
 
 void TCPEngineTransport::GetLocalAddress(net::IPEndPoint* address) const {
   DCHECK(server_socket_);
   server_socket_->GetLocalAddress(address);
 }
 
-void TCPEngineTransport::OnTCPConnectAccepted(int result) {
+void TCPEngineTransport::OnTCPConnectAccepted(net::CompletionCallback callback,
+                                              int result) {
   DCHECK_NE(net::ERR_IO_PENDING, result);
   DCHECK(accepted_socket_);
   if (result != net::OK) {
+    server_socket_.reset();

[Wez, 2016/11/18 02:35:47]

nit: Is this strictly correct? I have vague recollections of rare situations in
which you can be woken to accept an incoming TCP connection, only to find that
Accept returns nothing, at least under Linux...

[Kevin M, 2016/11/18 18:17:38]

Done.

     accepted_socket_.reset();
   }
-  base::ResetAndReturn(&connect_callback_).Run(result);
+  base::ResetAndReturn(&callback).Run(result);

[Wez, 2016/11/18 02:35:47]

nit: If you leave this being passed the callback as a parameter then you don't
really need ResetAndReturn :)

[Kevin M, 2016/11/18 18:17:38]

Acknowledged.

 }
 
 }  // namespace blimp