Cancel outstanding listen ops for RPC when shutting down

Use Boost's signal2 slot tracking mechanism to cancel any (still open)
listening sockets when receiving a shutdown signal.

Signed-off-by: Giel van Schijndel <me@mortis.eu>

src/bitcoinrpc.cpp

@@ -2741,7 +2741,6 @@ static void RPCListen(boost::shared_ptr< basic_socket_acceptor<Protocol, SocketA
                    ssl::context& context,
                    const bool fUseSSL)
 {
-
     // Accept connection
     AcceptedConnectionImpl<Protocol>* conn = new AcceptedConnectionImpl<Protocol>(acceptor->get_io_service(), context, fUseSSL);
 
@@ -2768,8 +2767,10 @@ static void RPCAcceptHandler(boost::shared_ptr< basic_socket_acceptor<Protocol,
 {
     vnThreadsRunning[THREAD_RPCLISTENER]++;
 
-    // Immediately start accepting new connections
-    RPCListen(acceptor, context, fUseSSL);
+    // Immediately start accepting new connections, except when we're canceled or our socket is closed.
+    if (error != error::operation_aborted
+     && acceptor->is_open())
+        RPCListen(acceptor, context, fUseSSL);
 
     AcceptedConnectionImpl<ip::tcp>* tcp_conn = dynamic_cast< AcceptedConnectionImpl<ip::tcp>* >(conn);
 
@@ -2833,11 +2834,6 @@ void ThreadRPCServer2(void* parg)
 
     asio::io_service io_service;
 
-    // Make sure that we'll get stopped when the application shuts down
-    boost::signals2::scoped_connection rpc_listen_thread_stop(
-            uiInterface.QueueShutdown.connect(boost::bind(
-                &asio::io_service::stop, &io_service)));
-
     ssl::context context(io_service, ssl::context::sslv23);
     if (fUseSSL)
     {
@@ -2862,21 +2858,24 @@ void ThreadRPCServer2(void* parg)
     asio::ip::address bindAddress = loopback ? asio::ip::address_v6::loopback() : asio::ip::address_v6::any();
     ip::tcp::endpoint endpoint(bindAddress, GetArg("-rpcport", 8332));
 
-    std::list< boost::shared_ptr<ip::tcp::acceptor> > acceptors;
     try
     {
-        acceptors.push_back(boost::shared_ptr<ip::tcp::acceptor>(new ip::tcp::acceptor(io_service)));
-        acceptors.back()->open(endpoint.protocol());
-        acceptors.back()->set_option(boost::asio::ip::tcp::acceptor::reuse_address(true));
+        boost::shared_ptr<ip::tcp::acceptor> acceptor(new ip::tcp::acceptor(io_service));
+        acceptor->open(endpoint.protocol());
+        acceptor->set_option(boost::asio::ip::tcp::acceptor::reuse_address(true));
 
         // Try making the socket dual IPv6/IPv4 (if listening on the "any" address)
         boost::system::error_code v6_only_error;
-        acceptors.back()->set_option(boost::asio::ip::v6_only(loopback), v6_only_error);
+        acceptor->set_option(boost::asio::ip::v6_only(loopback), v6_only_error);
 
-        acceptors.back()->bind(endpoint);
-        acceptors.back()->listen(socket_base::max_connections);
+        acceptor->bind(endpoint);
+        acceptor->listen(socket_base::max_connections);
 
-        RPCListen(acceptors.back(), context, fUseSSL);
+        RPCListen(acceptor, context, fUseSSL);
+        // Cancel outstanding listen-requests for this acceptor when shutting down
+        uiInterface.QueueShutdown.connect(signals2::slot<void ()>(
+                    static_cast<void (ip::tcp::acceptor::*)()>(&ip::tcp::acceptor::close), acceptor.get())
+                .track(acceptor));
 
         // If dual IPv6/IPv4 failed (or we're opening loopback interfaces only), open IPv4 separately
         if (loopback || v6_only_error)
@@ -2884,13 +2883,17 @@ void ThreadRPCServer2(void* parg)
             bindAddress = loopback ? asio::ip::address_v4::loopback() : asio::ip::address_v4::any();
             endpoint.address(bindAddress);
 
-            acceptors.push_back(boost::shared_ptr<ip::tcp::acceptor>(new ip::tcp::acceptor(io_service)));
-            acceptors.back()->open(endpoint.protocol());
-            acceptors.back()->set_option(boost::asio::ip::tcp::acceptor::reuse_address(true));
-            acceptors.back()->bind(endpoint);
-            acceptors.back()->listen(socket_base::max_connections);
-
-            RPCListen(acceptors.back(), context, fUseSSL);
+            acceptor.reset(new ip::tcp::acceptor(io_service));
+            acceptor->open(endpoint.protocol());
+            acceptor->set_option(boost::asio::ip::tcp::acceptor::reuse_address(true));
+            acceptor->bind(endpoint);
+            acceptor->listen(socket_base::max_connections);
+
+            RPCListen(acceptor, context, fUseSSL);
+            // Cancel outstanding listen-requests for this acceptor when shutting down
+            uiInterface.QueueShutdown.connect(signals2::slot<void ()>(
+                        static_cast<void (ip::tcp::acceptor::*)()>(&ip::tcp::acceptor::close), acceptor.get())
+                    .track(acceptor));
         }
     }
     catch(boost::system::system_error &e)
@@ -2904,14 +2907,6 @@ void ThreadRPCServer2(void* parg)
     vnThreadsRunning[THREAD_RPCLISTENER]--;
     io_service.run();
     vnThreadsRunning[THREAD_RPCLISTENER]++;
-
-    // Terminate all outstanding accept-requests
-    BOOST_FOREACH(boost::shared_ptr<ip::tcp::acceptor>& acceptor, acceptors)
-    {
-        acceptor->cancel();
-        acceptor->close();
-    }
-    acceptors.clear();
 }
 
 void ThreadRPCServer3(void* parg)