VHOST_USER_FLAG_NEED_REPLY
if ((msg->header.flags & ~VHOST_USER_FLAG_NEED_REPLY) !=
msg->header.flags |= VHOST_USER_FLAG_NEED_REPLY;
reply.header.flags &= ~VHOST_USER_FLAG_NEED_REPLY;
if (msg.msg.header.flags & VHOST_USER_FLAG_NEED_REPLY)