web界面上传文件，python里面返回一个请求c服务的url,继而请求c,用的是libevhtp

Question

static void
upload_ajax_cb(evhtp_request_t *req, void *arg)
{
    RecvFSM *fsm = arg;
    SearpcClient *rpc_client = NULL;
    char *parent_dir;
    GError *error = NULL;
    int error_code = ERROR_INTERNAL;
    char *filenames_json, *tmp_files_json;

    evhtp_headers_add_header (req->headers_out,
                              evhtp_header_new("Access-Control-Allow-Headers",
                                               "x-requested-with, content-type, accept, origin, authorization", 1, 1));
    evhtp_headers_add_header (req->headers_out,
                              evhtp_header_new("Access-Control-Allow-Methods",
                                               "GET, POST, PUT, PATCH, DELETE, OPTIONS", 1, 1));
    evhtp_headers_add_header (req->headers_out,
                              evhtp_header_new("Access-Control-Allow-Origin",
                                               "*", 1, 1));
    evhtp_headers_add_header (req->headers_out,
                              evhtp_header_new("Access-Control-Max-Age",
                                               "86400", 1, 1));

    evhtp_headers_add_header (req->headers_out,
                              evhtp_header_new("Content-Type",
                                               "application/json; charset=utf-8", 1, 1));

    if (evhtp_request_get_method(req) == htp_method_OPTIONS) {

         set_content_length_header (req);
         evhtp_send_reply (req, EVHTP_RES_OK);
         return;
    }



    if (!fsm || fsm->state == RECV_ERROR)
        return;

    if (!fsm->files) {
        seaf_warning ("[upload] No file uploaded.\n");
        set_content_length_header (req);
        evhtp_send_reply (req, EVHTP_RES_BADREQ);
        return;
    }

    parent_dir = g_hash_table_lookup (fsm->form_kvs, "parent_dir");
    if (!parent_dir) {
        seaf_warning ("[upload] No parent dir given.\n");
        evbuffer_add_printf(req->buffer_out, "Invalid URL.\n");
        set_content_length_header (req);
        evhtp_send_reply (req, EVHTP_RES_BADREQ);
        return;
    }

    if (!check_tmp_file_list (fsm->files, &error_code))
        goto error;

    rpc_client = ccnet_create_pooled_rpc_client (seaf->client_pool,
                                                 NULL,
                                                 "seafserv-threaded-rpcserver");

    if (seafile_check_quota (rpc_client, fsm->repo_id, NULL) < 0) {
        seaf_warning ("[upload] Out of quota.\n");
        error_code = ERROR_QUOTA;
        goto error;
    }

    filenames_json = file_list_to_json (fsm->filenames);
    tmp_files_json = file_list_to_json (fsm->files);

    char *ret_json = seafile_post_multi_files (rpc_client,
                                               fsm->repo_id,
                                               parent_dir,
                                               filenames_json,
                                               tmp_files_json,
                                               fsm->user,
                                               0,
                                               &error);
    g_free (filenames_json);
    g_free (tmp_files_json);
    if (error) {
        if (error->code == POST_FILE_ERR_FILENAME) {
            error_code = ERROR_FILENAME;
            seaf_warning ("[upload] Bad filename.\n");
        }
        g_clear_error (&error);
        goto error;
    }

    ccnet_rpc_client_free (rpc_client);

    evbuffer_add (req->buffer_out, ret_json, strlen(ret_json));
    g_free (ret_json);

    set_content_length_header (req);
    evhtp_send_reply (req, EVHTP_RES_OK);
    return;

error:
    if (rpc_client)
        ccnet_rpc_client_free (rpc_client);

    switch (error_code) {
    case ERROR_FILENAME:
        evbuffer_add_printf(req->buffer_out, "{\"error\": \"Invalid filename.\"}");
        set_content_length_header (req);
        evhtp_send_reply (req, SEAF_HTTP_RES_BADFILENAME);
        break;
    case ERROR_EXISTS:
        evbuffer_add_printf(req->buffer_out, "{\"error\": \"File already exists.\"}");
        set_content_length_header (req);
        evhtp_send_reply (req, SEAF_HTTP_RES_EXISTS);
        break;
    case ERROR_SIZE:
        evbuffer_add_printf(req->buffer_out, "{\"error\": \"File size is too large.\"}");
        set_content_length_header (req);
        evhtp_send_reply (req, SEAF_HTTP_RES_TOOLARGE);
        break;
    case ERROR_QUOTA:
        evbuffer_add_printf(req->buffer_out, "{\"error\": \"Out of quota.\"}");
        set_content_length_header (req);
        evhtp_send_reply (req, SEAF_HTTP_RES_NOQUOTA);
        break;
    case ERROR_RECV:
    case ERROR_INTERNAL:
        set_content_length_header (req);
        evhtp_send_reply (req, EVHTP_RES_SERVERR);
        break;
    }
}

def get_file_op_url(request, repo_id):
    """Get file upload/update url for AJAX.
    """
    content_type = 'application/json; charset=utf-8'

    op_type = request.GET.get('op_type') # value can be 'upload', 'update', 'upload-blks', 'update-blks'
    if not op_type:
        err_msg = _(u'Argument missing')
        return HttpResponse(json.dumps({"error": err_msg}), status=400,
                            content_type=content_type)

    username = request.user.username
    url = ''
    if check_repo_access_permission(repo_id, request.user) == 'rw':
        token = seafile_api.get_fileserver_access_token(repo_id, 'dummy',
                                                        op_type, username)
        url = gen_file_upload_url(token, op_type + '-aj')
    
    return HttpResponse(json.dumps({"url": url}), content_type=content_type)

例如
192.168.1.10:8082是c的fileserver服务
8082被fileserver二进制程序监听

我的问题是这里的headers_out是返回给谁的，是浏览器的web客户端，还是SearpcClient这里自定义的client