dco-win: fix reconnect with dco-win driver

DCO device is "exclusive" device, meaning that only one app at the time can access it
and device is considered opened until pending IO is complete.

start_impl_() might be called on reconnect, in the same stack with closing device handle.
Closing handle also triggers completion of pending IO, such as async read. However this happens
in the next iteration of ASIO even loop. Therefore we defer opening DCO device
(i.e. calling start_impl_) to let ASIO complete pending IO.

Note that this is not required when async resolve is performed, since this implies deferring.

Signed-off-by: Lev Stipakov <[email protected]>

openvpn/dco/ovpndcowincli.hpp

@@ -43,7 +43,12 @@ class OvpnDcoWinClient : public Client, public KoRekey::Receiver {
     RemoteList& rl = *config->transport.remote_list;
     if (rl.endpoint_available(&server_host, &server_port, &proto_))
       {
-	start_impl_();
+	// defer to let pending IO finish
+	openvpn_io::post(io_context, [self=Ptr(this)]()
+	{
+	  OPENVPN_ASYNC_HANDLER;
+	  self->start_impl_();
+	});
       }
     else
       {