penwrt下 luci.http.setfilehandler 上传文件失败

** openwrt下 luci.http.setfilehandler 上传文件失败**

function importconfig()
    local http = require "luci.http"
    local archive_tmp = "/tmp/file.data"
    local Status = false
    local errorinfo
    local fp
    local msg
    http.setfilehandler(
        function(meta, chunk, eof)
            if not fp and meta and meta.name == "file_import" then
                fp = io.open(archive_tmp, "w")
                if nil == fp then
                    msg = "The storage space is insufficient."
                    return
                end
            end
            if fp and chunk then
                if 0 == #chunk then
                    msg = "Failed to upload the file."
                    return
                end
                local ret = fp:write(chunk)
                if not ret then
                    msg = "The storage space is insufficient."
                    return
                end
            end
            if fp and eof then
                fp:close()
            end
        end
    )
    
    local jsonData = {
        status = Status,
        error = errorinfo
    }
    
    luci.http.prepare_content("application/json")
    luci.http.write_json(jsonData)
end

运行结果及报错内容
一直会执行 0 == #chunk，提示上传文件失败

抓包看文件已经上传